Name: a research method for detecting transient myocardial ischemia in patients with suspected acute coronary syndrome using continuous st-segment analysis
Uploaded: 2012-12-28T13:00:00
Duration: 18 min 11 s
Description: Watch this Scientific Journal Video about A Research Method For Detecting Transient Myocardial Ischemia In Patients With Suspected Acute Coronary Syndrome Using Continuous ST-segment Analysis at JoVE.

This study was funded by a grant from the National Institutes for Nursing Research R21 NR-011202 (MMP); R21 NR-009716 (MGC).
The authors would like to thank Debbie Ganchan, RN, BSN for her careful and thoughtful data collection. We would also like to thank Saint Mary's Hospital as well as the nurses and physicians at the hospital who have generously offered their assistance with the study.

1. Patient Preparation
<ol>
	<li>Obtaining informed consent.</li>
	<li>Identify land marks on the chest for accurate lead placement. In order to minimize ECG artifact and noise the Mason-Likar electrode configuration is used in which limb lead electrodes are placed on the torso rather than the distal extremities (Figure 2).23</li>
	<li>Prep the skin of the torso with alcohol prep pads and dry briskly with gauze pads to ensure optimal skin electrode contact.</li>
	<li>If necessary, clip chest hair at the specific torso locations in order to make adequate contact with the skin electrode. Perform this step with caution as many of this patient population receive anticoagulation therapy and are therefore prone to bleeding.</li>
	<li>Use indelible ink, if possible, to mark the skin electrode sites to ensure electrodes are returned to the correct location in the event they fall off or are removed for procedures (i.e., echocardiograms, chest X-ray, etc.).</li>
	<li>In women, electrode V3 should be placed on top of the breast tissue and electrodes V4 and V5 should be placed immediately below a pendulous breast so that the breast lies on top of the electrode in order to ensure accurate placement and prevent motion artifact.</li>
	<li>Dual monitoring is used in this study, the hospital bedside monitor and the research Holter recorder. Hence, two ECG skin electrodes are applied to the torso.</li>
	<li>Connect ECG lead wires to the skin electrodes before placing the electrodes on the patient's chest to prevent unnecessary pressure on the chest.Radiolucent skin electrodes are applied in order to avoid removal for radiographic procedures.</li>
	<li>Enter the patient's unique research identification number (de-identified) into the Holter device and start ECG monitoring.</li>
	<li>Place the Holter recorder in a monitor pouch, and place via a lanyard around neck or place in the gown pocket.</li>
	<li>Obtain positional ECGs for use during the off-line analysis of the ECG data. The three positions to include are: 1) supine, 2) right side, and 3) left side lying.</li>
	<li>Assess the patient at least every 2 hr when the research staff is present in the hospital and at the end of the day-time shift to ensure monitoring is maintained over night. Staff education of nurses, and ancillary staff (i.e., X-ray, echocardiography, and catheterization technicians) is done to ensure skin electrodes are replaced if removed for a procedure. A torso diagram with correct electrode placement is left at the bedside as a resource so that staff can replace the skin electrodes if necessary as well as extra skin electrodes.</li>
	<li>If the patient goes to the cardiac catheterization laboratory, connect the radiolucent lead wires to the skin electrodes so that ECG monitoring can be maintained during the catheterization procedure to ensure continuous monitoring.</li>
	<li>When monitoring is completed, the equipment is cleaned with antimicrobial wipes.</li>
</ol>
2. ECG Analysis Procedure
<ol>
	<li>At the completion of monitoring (may vary in duration), load the compact flashcard from the ECG Holter recorder onto the flashcard reader of H-Scribe research computer.</li>
	<li>Prepare the data for analysis by identifying and labeling each QRS complex as normal, ventricular, supraventricular or artifact with the H-Scribe arrhythmia analysis software.</li>
	<li>Initial assessment of the ECG data is done without knowledge of clinical data, to minimize bias.</li>
	<li>The H-Scribe software is programmed to identify transient myocardial ischemia using the standard definition; ST deviation (elevation or depression) &ge; 100 microvolts in &ge; 2 ECG lead(s) lasting &ge; 60 sec.32 In this study, ST-segment deviation is measured at 60 msec past the J-point.</li>
	<li>ST-segment changes meeting these criteria are identified and labeled by the H-Scribe and indicated on the analysis summary. Human oversight to verify whether ischemia is present must be done for any computer generated event in order to ensure false positive ST-segment changes are identified correctly. This process will be described below.</li>
	<li>ST-segment trends are assessed for changes suggestive of acute ischemia an efficient method of evaluating hours of continuously acquired ECG data (Figure 3).</li>
	<li>In order to identify true myocardial ischemia, any trend suggestive of acute ischemia is assessed by obtaining three ECGs:
	<ol class="ualpha">
		<li>Baseline ECG prior to the ST-segment changes, identified as 'pre-event ECG'</li>
		<li>An ECG during the maximum point of ST segment deviation, identified as 'max event ECG'</li>
		<li>An ECG when ST-segment deviation has completely resolved, identified as 'post-event ECG'</li>
	</ol>
	</li>
	<li>Assess each of the three ECGs to ensure the ST changes are not due to false positive changes (e.g., accelerated ventricular rhythm, intermittent ventricular pacing rhythm, intermittent bundle branch block, or body position changes).20</li>
	<li>Missing ECG data, data of insufficient quality and false-positive ST changes are excluded from the analysis. These problems will be minimized by using several strategies. These include (1) use of radiolucent ECG electrodes, eliminating the need to remove the electrodes for X-rays; (2) high quality skin prep by research nurses performed at the outset of monitoring; (3) rounding every 2 hr on patients throughout the day; and (4) availability by phone to answer concerns or questions from the nursing and medical staff. Additionally, the research team communicates with both nursing and medical staff on a regular basis.</li>
	<li>Once the ECG data is analyzed the patient's medical record is used to identify dates/times of treatments, medications and symptoms during the monitoring period.</li>
	<li>Verification of ECG analysis is ensured by having a second expert analyze the ECG data using the same methodology described above in a designated proportion of the sample. Our team does this for 20% of the patients enrolled.</li>
	<li>For research purposes, archive de-identified ECG data onto an external hard drive and/or onto a network drive to ensure the data is saved appropriately.</li>
</ol>

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The authors have no competing financial interests to declare.

In this article a research methodology using Holter recordings that capture continuous 12-lead ECG recordings is described. While computer-assisted ST-segment software works well for detecting transient ischemia, accurate analysis requires careful, expert human oversight. Important factors to consider during analysis include (1) artifact, (2) the consistency and accuracy electrode placement, (3) body position changes, (4) drug effects, and (5) sudden waveform changes.20
In summary, continuous 12-lead ECG monitoring, which is both inexpensive and non-invasive, can identify transient episodes of myocardial ischemia, a precursor to MI, even when asymptomatic.10,12,33,34 However, 12-lead ECG monitoring is not usual hospital practice; rather, only two leads are typically monitored. Information obtained with 12-lead ECG monitoring might provide useful information for deciding on the best treatment in patients with ACS. However, randomized clinical trials assessing clinician responses to ischemia are needed to determine the value of this technology for identifying high risk patients that might benefit from more aggressive management strategies during ACS.

According to the most recent American Heart Association statistics, coronary artery disease (CAD) was estimated to be responsible for 1.2 million hospital stays and was the most expensive medical condition treated.1 More than half of the hospital stays for CAD were among patients who also received percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG) during their stay. Because of the prevalence of CAD, clinicians working in hospitals are likely to encounter these patients frequently. The purpose of this manuscript is to describe the ECG application and analysis methodology used in the COMPARE Study (electroCardiographic evaluatiOn of ischeMia comParing invAsive to phaRmacological trEatment; (R21 NR-011202), which might be utilized by other researches exploring this clinical problem.
Each year, nearly 700,000 Americans will have a new coronary attack, or acute coronary syndrome (ACS).1 The pathophysiology of ACS involves rupture of an atherosclerotic plaque; hence, treatment is aimed at plaque stabilization in order to prevent cellular death. However, there is considerable debate among clinicians, about which treatment pathway is best: early invasive using percutaneous coronary intervention (PCI/stent) when indicated or a conservative approach (i.e., medications only or PCI/stent if recurrent symptoms occur).2-5
There are three types of ACS: ST elevation myocardial infarction (STEMI), non-ST elevation MI (NSTEMI), and unstable angina (UA).6 Among the three types, NSTEMI/UA is nearly four times as common as STEMI.7,8 Treatment decisions for NSTEMI/UA are based largely on symptoms and resting or exercise electrocardiograms (ECG). However, because of the dynamic and unpredictable nature of the atherosclerotic plaque, these methods often under-detect myocardial ischemia because symptoms are unreliable, and/or continuous ECG monitoring was not utilized.
The manifestations of NSTEMI/UA may include (1) symptoms (chest, arm, jaw or neck pain, sweating, nausea), (2) release of cardiac biomarkers in the case of NSTEMI (Troponin I, Troponin T, or creatnine kinase-MB) and (3) electrocardiographic (ECG) changes (intermittent ST elevation/depression, or T-wave inversion). While symptoms may occur in ACS, it is well documented that transient episodes of ECG-detected ischemia are clinically silent in over 70% of patients.9-12 Importantly, many studies have found that patients with ECG-detected ischemia, as compared to patients without such events, were at higher risk for unfavorable outcomes in both the short term11-13 and long term.14-16 Hence, symptoms are an unreliable indicator of ischemia in NSTEMI/UA, which is problematic since treatment decisions for an early invasive strategy or initial medication strategy are often driven by patient symptoms.2-5 Further, biomarkers identify NSTEMI/UA patients too late because their presence in the serum indicates that cellular death has already occurred.
Electrocardiographic changes indicative of ischemia occur within seconds of diminished coronary blood flow.10,17 The portion of the ECG complex that changes during acute ischemia is the ST-segment, which is measured at one of three points; (1) J-point, (2) J point plus 60 milliseconds (msec) or, (3) J-point plus 80 (msec) (Figure 1).
The 12-lead ECG has important advantages over both symptoms and biomarkers in identifying MI in that it is non-invasive, inexpensive, and if maintained continuously can identify transient ischemia, even when it is clinically silent. While 12-lead ECG monitoring is ideal because multiple areas of the heart are assessed, typical hospital practice incorporates monitoring with only two ECG leads. The two ECG leads most commonly monitored by nurses in the hospital setting are leads V1 and II.18 Unfortunately, these two leads are not sensitive for detecting transient ischemia in many ACS patients.10,19 Therefore, ischemia occurring outside of these two monitored leads will be missed.
Using 12-lead ECG monitoring the COMPARE Study is designed to assess the frequency and clinical consequences of transient myocardial ischemia, in patients with NSTEMI/UA treated with early invasive PCI/stent compared to those managed with an initial conservative approach, which includes medications alone, with transition to PCI/stent following recurrent symptoms. In our study, continuous 12-lead ECG Holter recorder is used to capture ischemia. The aim of this descriptive study is to assess the frequency and clinical consequences of transient myocardial ischemia, in patients with NSTEMI/UA treated with either early invasive PCI/stent or those managed conservatively (medications or PCI/stent following recurrent symptoms).
Methodological Challenges
While computer-assisted ST-segment software works well for detecting transient ischemia, accurate analysis requires careful, expert human oversight. Important factors to consider during analysis include (1) artifact, (2) the consistency and accuracy electrode placement, (3) body position changes, (4) drug effects, and (5) sudden waveform changes.20 Each of these factors will be discussed below.
Artifact: Because clinically significant ST-segment changes are as small as 100 microvolt (one small box on the ECG paper), noisy signal from muscle artifact can significantly hinder analysis. Most artifacts are related to improper skin preparation.21 The problem can be easily solved with careful skin preparation of the patient's torso at the outset of monitoring and as needed throughout the monitoring period.21-23 Skin preparation should include removal of hair at the sites of electrodes, vigorous removal of skin oil/debris, and use of an alcohol prep pad and/or a washcloth.23,24
Consistency and Accuracy of Electrode Placement: False positive ST-segment changes can occur when electrodes are moved or removed during monitoring.20 This can be managed by marking each electrode site with indelible ink at the outset of monitoring to ensure that electrodes are reapplied to the correct location if they fall off or are removed for procedures (e.g., echocardiogram, X-rays).25 We recommend an assessment of the patient's torso at least every 4 hr to ensure skin electrodes are on the chest.
Body Position Changes: Studies using continuous ST-segment monitoring have shown that some patients can exhibit concomitant QRS and ST-segment amplitude changes during body position changes (i.e., left-, or right-side lying), which can be mistaken for myocardial ischemia.26,27 Our research team found that body position changes were the most common cause of false positive ST-segment alarms.20 Using echocardiography, Feldman and co-workers28 found that when patients moved from a supine to a left side-lying position, the left ventricle moved closer to the lateral chest wall. This had a direct effect on the distance of the left ventricle from the chest electrodes and resulted in an increase in the amplitude of the R-wave in the ECG leads over this myocardial territory. These changes have been confirmed by others.26,27 In general, positional ECG changes are suspected when ECG waveform amplitudes increase with concomitant ST-segment changes. A helpful strategy is to obtain 'positional template ECGs' with patients assuming supine, left- and right-side lying positions when monitoring is initiated, for later comparison during the analysis.
Pharmacological Effects: Even in therapeutic doses drugs can affect ECG waveforms. Drugs that alter the ST-segment are particularly important since they lead to a misdiagnosis of myocardial ischemia.29 These drugs include digitalis, antiarrhythmics, and phenothiazines. The "digitalis effect" is used to describe the characteristic ST-segment and T wave changes that can occur with this drug, including 'coved' ST-segment depression, a flattened T-wave and a short QTc interval.30 Other drugs, such as the antiarrhythmics (i.e., quinidine, sotalol and amiodarone)30 and phenothiazine, used to treat schizophrenia/psychotic disorders, increase the QTc interval, and decrease T-wave amplitude.31
Nevertheless, patients taking these drugs can be monitored for acute ST-segment changes that may indicate acute myocardial ischemia. The baseline abnormalities seen with the drugs are chronic; hence any ST-segment deviation (depression or elevation) that occurs from the patient's baseline ST-segment level should be assessed for acute ischemia.
Sudden Waveform Changes: Transient conditions, such as arrhythmias, right- or left bundle branch block (BBB), and intermittent ventricular paced beats, can distort the ST-segment and lead to a false-positive ischemia diagnosis.20
In summary, continuous ST-segment monitoring is an excellent tool for identifying transient myocardial ischemia in patients with suspected ACS. However, this method requires that careful application of electrodes and leads wires is performed at the initiation and throughout monitoring. This method also requires careful human oversight in order to eliminate false positive ST-segment changes.
Step-by-Step Methodology
In the COMPARE study, a digital Holter recorder is used (H12+, Mortara Instruments, Milwaukee, WI), which records electrical potentials sampled at 4-msec intervals over a 10-sec period to identify a median beat. All 12 ECG leads (I, II, III, aVR, aVL, aVF, V1-V6) are simultaneously acquired at a digital sampling rate of 1,000 samples per sec per channel which is stored to a compact flash memory card. In addition, the H12+ features electrode impedance measurement to ensure proper skin preparation prior to beginning the Holter recording. A display indicates if an ECG lead has become detached and also provides an internal clock for recording of diary events. Data from the Holter monitor flashcard is then downloaded to the H-Scribe, an off-line Holter Analysis System (Mortara Instruments, Milwaukee, WI). The software allows analysis of continuous ECG recordings to determine the quality of the signal, presence of arrhythmias, and ischemia.
Research assistants with experience working with the cardiac patient population collect the ECG Holter data. A training session at the start of the study was scheduled to ensure the quality and consistency of the study protocol. A training session covering the ECG monitoring procedure, including how to apply ECG monitoring equipment, initiate/maintain ECG monitoring, and download ECG Holter data onto the research computer was done. Return demonstrations were performed and inter-rater reliability is done throughout the study by randomly assessing 10% of currently enrolled subjects. Bi-weekly research team meetings ensure that recruitment goals are being met, challenges are discussed, and results of inter-rater reliability tests can be shared.
The research methodology used in the COMPARE Study has two important steps; patient preparation and off-line ECG analysis. Both of these methods will be explained in a step-by-step manner in the subsequent section.

<table border="1">
 <tbody>
 <tr>
 <td>Name of Reagent/Material</td>
 <td>Company</td>
 <td>Catalogue Number</td>
 <td>Comments</td>
 </tr>
 <tr>
 <td>Skin Electrodes: Bio ProTech Foam Radiotranslucent Electrode</td>
 <td> Cardiac Direct </td>
 <td>SKU: T716C </td>
 <td></td>
 </tr>
 <tr>
 <td>Radiolucent Leadwires</td>
 <td>Advantage Medical Cables </td>
 <td>LW-3090R48/5A </td>
 <td></td>
 </tr>
 <tr>
 <td>Holter Recorder: H12+ 12-lead Holter recorder, Version 3.12, 24 hr Compact Flash card, American Heart Association 10 wire LeadForm patient cable</td>
 <td>Mortara Instrument, Inc. Milwaukee, WI </td>
 <td>H12PLUS-AAA-XXXXX </td>
 <td></td>
 </tr>
 <tr>
 <td>H-Scribe ECG Holter Analysis System, Version 3.71 </td>
 <td>Mortara Instrument, Inc. Milwaukee, WI </td>
 <td>HSCRIBE - BAA - AACXX </td>
 <td></td>
 </tr>
 </tbody>
</table>

a research method for detecting transient myocardial ischemia in patients with suspected acute coronary syndrome using continuous st-segment analysis

Each year, an estimated 785,000 Americans will have a new coronary attack, or acute coronary syndrome (ACS). The pathophysiology of ACS involves rupture of an atherosclerotic plaque; hence, treatment is aimed at plaque stabilization in order to prevent cellular death. However, there is considerable debate among clinicians, about which treatment pathway is best: early invasive using percutaneous coronary intervention (PCI/stent) when indicated or a conservative approach (i.e., medication only with PCI/stent if recurrent symptoms occur).
There are three types of ACS: ST elevation myocardial infarction (STEMI), non-ST elevation MI (NSTEMI), and unstable angina (UA). Among the three types, NSTEMI/UA is nearly four times as common as STEMI. Treatment decisions for NSTEMI/UA are based largely on symptoms and resting or exercise electrocardiograms (ECG). However, because of the dynamic and unpredictable nature of the atherosclerotic plaque, these methods often under detect myocardial ischemia because symptoms are unreliable, and/or continuous ECG monitoring was not utilized.
Continuous 12-lead ECG monitoring, which is both inexpensive and non-invasive, can identify transient episodes of myocardial ischemia, a precursor to MI, even when asymptomatic. However, continuous 12-lead ECG monitoring is not usual hospital practice; rather, only two leads are typically monitored. Information obtained with 12-lead ECG monitoring might provide useful information for deciding the best ACS treatment.
Purpose. Therefore, using 12-lead ECG monitoring, the COMPARE Study (electroCardiographic evaluatiOn of ischeMia comParing invAsive to phaRmacological trEatment) was designed to assess the frequency and clinical consequences of transient myocardial ischemia, in patients with NSTEMI/UA treated with either early invasive PCI/stent or those managed conservatively (medications or PCI/stent following recurrent symptoms). The purpose of this manuscript is to describe the methodology used in the COMPARE Study.
Method. Permission to proceed with this study was obtained from the Institutional Review Board of the hospital and the university. Research nurses identify hospitalized patients from the emergency department and telemetry unit with suspected ACS. Once consented, a 12-lead ECG Holter monitor is applied, and remains in place during the patient's entire hospital stay. Patients are also maintained on the routine bedside ECG monitoring system per hospital protocol. Off-line ECG analysis is done using sophisticated software and careful human oversight.

The initial analysis of the ECG data includes an assessment of the ST-segment trends in each of the 11 leads using the H-Scribe software. Of note, lead aVR is not displayed on trend because it's an inverted lead and is not considered useful for trend analysis; however, this lead is visible on the 12-lead ECG printout. This method is a quick and easy assessment used to evaluate hours of ECG data for the presence of possible transient myocardial ischemia. A change in the ST-segment trend requires further in-depth analysis of printed 12-lead ECG's before, during and after the trend change and will be explained below.
<img alt="Figure 1" src="/files/ftp_upload/50124/50124fig1.jpg" /> 
 Figure 1. Panel A shows a normal ST-segment, which is flat compared to the PR segment; B showsST-segment elevation, typically indicating total coronary occlusion; and C shows ST-segment depression, typically indicating partial coronary occlusion. ST-segment deviation can be measured at the J-point, J-point + 60 msec, or J-point + 80 msec. (Source: Pelter, M. &amp; Carey, M. in AACN Procedure Manual for Critical Care (ed Wiegand Lynn McHale DJ) 511-518 (Elsevier Saunders, 2011 with permission).
<img alt="Figure 2" src="/files/ftp_upload/50124/50124fig2.jpg" /> 
 Figure 2. Torso illustrates lead locations used for the Mason-Likar electrode configuration. Right Arm (RA) Infraclavicular fossa close to the right shoulder; Left Arm (LA) infraclavicular fossa close to the left shoulder; Right Leg (RL) Lower right abdomen below the umbilicus; Left Leg (LL) lower left abdomen below the umbilicus; V1 4th intercostal space right of the sternal boarder; V2 4th intercostal space left of the sternal boarder; V3 Mid way between V2 and V4; V4 5th intercostal space midclavicular line; V5 Straight line from V4 anterior axillary line; V6 Straight line from V4 midaxillary. (Source: Pelter, M. &amp; Carey, M. in AACN Procedure Manual for Critical Care (ed Wiegand Lynn McHale DJ) 511-518 (Elsevier Saunders, 2011 with permission).
<img alt="Figure 3" fo:content-width="5in" fo:src="/files/ftp_upload/50124/50124fig3highres.jpg" src="/files/ftp_upload/50124/50124fig3.jpg" /> 
 Figure 3. Illustrates a 'normal,' or non-ischemic ST-segment trend in a patient with 23 &frac12; hr of ST-segment monitoring. On the Y-axis, are the 11 ECG leads, with lead V1 shown at the top and lead III at the bottom. The 0.0 on the Y-axis indicates a normal or isoelectric ST-segment. The X-axis displays a 24 hr time period. In this example, ECG monitoring was initiated just before 0900 and ended at 0800 the next morning. The ST-segments in this patient remain at the 0.0 point throughout the monitoring period (solid line), indicating there were no ST-segment shifts indicative of transient myocardial ischemia. A 12-lead ECG can be obtained from any point in time during the monitoring period by simply selecting a specific time and printing the ECG. It is possible to save any ECG(s) in a report format for the research documentation file. <a href="https://www.jove.com/files/ftp_upload/50124/50124fig3large.jpg" target="_blank"> Click here to view larger figure</a>.
<img alt="Figure 4" fo:content-width="6in" fo:src="/files/ftp_upload/50124/50124fig4highres.jpg" src="/files/ftp_upload/50124/50124fig4.jpg" /> 
 Figure 4. In this example, a transient ST-segment elevation event is illustrated. Monitoring is initiated just before 1200 and is maintained continuously until 1000 the next day (X-axis). At 1230, less than 1 hr after monitoring was initiated, ST-segment elevation is seen in leads II, aVF and III (see bottom three ST-segment trends). 4A, 4B, and 4C are 12-lead ECG's printed pre-event, during maximal ST-segment changes, and post-event and show abrupt ST-segment elevation in lead II, aVF, and III suggestive of complete coronary occlusion, that resolves after 1 hr. Of note, this patient was asymptomatic and the ST segment changes were not detected by the hospital staff. The ST-segment trend also shows two additional small but brief ST-segment changes in these same leads at 1500 and just before 1800. Because these ST-segment changes did not exceed the 100 microvolt threshold required for an ST event they were not counted as transient ischemic events. The following morning at 0800 this patients was taken to the cardiac catheterization laboratory based on his symptoms and troponin (2.5 &mu;g/L). A 90% lesion was found in the right coronary artery and a stent was placed. The ST-segment elevation at the end of the monitoring period occurred during the percutaneous coronary intervention procedure including stent placement and resolved following the procedure. 4A. Pre-event transient ischemic event ECG. 4B. Maximal ST elevation during ischemic event. Note ST-segment elevation of 200 microvolts in leads II, III, and aVF. 4C. 12-lead ECG following the ischemic event. Note that ST-segment elevation has resolved in leads II, III, and aVF (arrows). <a href="https://www.jove.com/files/ftp_upload/50124/50124fig4large.jpg" target="_blank"> Click here to view larger figure</a>.
<img alt="Figure 5" fo:content-width="6in" fo:src="/files/ftp_upload/50124/50124fig5highres.jpg" src="/files/ftp_upload/50124/50124fig5.jpg" /> 
 Figure 5. This figure illustrates two issues that can occur during Holter monitoring, interruption of continuous monitoring due to; (1) detached lead wires or skin electrodes, and (2) motion artifact. In both cases, ECG data is not available for analysis. Just prior to 1400, the ST-segment trend disappears in all of the leads when the right leg electrode (ground electrode) became detached. When the lead was replaced at 1600 monitoring resumed. Unfortunately, this same problem occurs just after 0100 and continued until the end of the recording. <a href="https://www.jove.com/files/ftp_upload/50124/50124fig5large.jpg" target="_blank"> Click here to view larger figure</a>.
Also illustrated in this figure when monitoring resumes just prior to 1600 is an abrupt change in the ST-trend. A similar pattern of irregular ST-segment trend changes are seen at approximately 1200, and from 1830 to 2000. 5A shows motion artifact as the sources of the ST-segment changes, and was also the source of the other irregular trend changes. In general, abrupt and or erratic changes of the ST-segment trend often indicate motion artifact and or body position changes, rather than myocardial ischemia. However, ECGs from before, during and after ST-segment trend changes should be printed and carefully evaluated for possible ischemia.
<img alt="Figure 6" fo:content-width="6in" fo:src="/files/ftp_upload/50124/50124fig6highres.jpg" src="/files/ftp_upload/50124/50124fig6.jpg" /> 
 Figure 6. This ST-segment trend show false positive ST-segment changes due to intermittent ventricular pacer. Just prior to 0100 the ST-segment trend changes showing ST-segment elevation in lead V3, V4, V5, II, aVF and III. 6A is a 12-lead ECG obtained at 00:51:02 just prior to the trend change. Of note, are atrial pacer spikes visible in the last 4 beats of the 10 sec rhythm strip in lead II (see bottom of figure). Note ST-segment depression in leads II, III, aVF, V5 and V6 likely due to the drug digitalis, which this patient was taking. These changes are chronic and were present throughout the monitoring period. 6B shows an ECG obtained at 01:20:39 where ventricular pacing is now present, atrial pacing is visible as well. The result of ventricular pacing is a change of the ST segment from predominantly negative to predominately positive in leads V3, V4, V5, II, aVF, resulting in ST-segment elevation. However, these changes are not due to ischemia but rather abnormal depolarization and repolarization associated with ventricular pacer. <a href="https://www.jove.com/files/ftp_upload/50124/50124fig6large.jpg" target="_blank"> Click here to view larger figure</a>.

Watch this Scientific Journal Video about A Research Method For Detecting Transient Myocardial Ischemia In Patients With Suspected Acute Coronary Syndrome Using Continuous ST-segment Analysis at JoVE.

A Research Method For Detecting Transient Myocardial Ischemia In Patients With Suspected Acute Coronary Syndrome Using Continuous ST-segment Analysis

Continuous 12-lead electrocardiographic (ECG) monitoring can identify transient myocardial ischemia, even when asymptomatic, among patients with suspected acute coronary syndrome (ACS). In this article we describe our method for initiating patient monitoring using a Holter device, downloading the ECG data for off-line analysis, and how to utilize the ECG software to identify transient ischemia.

Each year, an estimated 785,000 Americans will have a new coronary attack, or acute coronary syndrome (ACS). The pathophysiology of ACS involves rupture ...

a-research-method-for-detecting-transient-myocardial-ischemia

Research

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Medicine

Acute Myocardial Infarction in Rats

With heart failure leading the cause of death in the USA (Hunt), biomedical research is fundamental to advance medical treatments for cardiovascular diseases. Animal models that mimic human cardiac disease, such as myocardial infarction (MI) and ischemia-reperfusion (IR) that induces heart failure as well as pressure-overload (transverse aortic constriction) that induces cardiac hypertrophy and heart failure (Goldman and Tarnavski), are useful models to study cardiovascular disease. In particular, myocardial ischemia (MI) is a leading cause for cardiovascular morbidity and mortality despite controlling certain risk factors such as arteriosclerosis and treatments via surgical intervention (Thygesen). Furthermore, an acute loss of the myocardium following myocardial ischemia (MI) results in increased loading conditions that induces ventricular remodeling of the infarcted border zone and the remote non-infarcted myocardium. Myocyte apoptosis, necrosis and the resultant increased hemodynamic load activate multiple biochemical intracellular signaling that initiates LV dilatation, hypertrophy, ventricular shape distortion, and collagen scar formation. This pathological remodeling and failure to normalize the increased wall stresses results in progressive dilatation, recruitment of the border zone myocardium into the scar, and eventually deterioration in myocardial contractile function (i.e. heart failure). The progression of LV dysfunction and heart failure in rats is similar to that observed in patients who sustain a large myocardial infarction, survive and subsequently develops heart failure (Goldman). The acute myocardial infarction (AMI) model in rats has been used to mimic human cardiovascular disease; specifically used to study cardiac signaling mechanisms associated with heart failure as well as to assess the contribution of therapeutic strategies for the treatment of heart failure. The method described in this report is the rat model of acute myocardial infarction (AMI). This model is also referred to as an acute ischemic cardiomyopathy or ischemia followed by reperfusion (IR); which is induced by an acute 30-minute period of ischemia by ligation of the left anterior descending artery (LAD) followed by reperfusion of the tissue by releasing the LAD ligation (Vasilyev and McConnell). This protocol will focus on assessment of the infarct size and the area-at-risk (AAR) by Evan's blue dye and triphenyl tetrazolium chloride (TTC) following 4-hours of reperfusion; additional comments toward the evaluation of cardiac function and remodeling by modifying the duration of reperfusion, is also presented. Overall, this AMI rat animal model is useful for studying the consequence of a myocardial infarction on cardiac pathophysiological and physiological function.

The rat model of acute myocardial infarction (AMI) is useful to study the consequence of a MI on cardiac pathophysiological and physiological function.

With heart failure leading the cause of death in the USA (Hunt), biomedical research is fundamental to advance medical treatments for cardiovascular ...

Continuous Manual Exchange Transfusion for Patients with Sickle Cell Disease: An Efficient Method to Avoid Iron Overload

Children with sickle cell anemia (SCA) may be at risk of cerebral vasculopathy and strokes, which can be prevented by chronic transfusion programs. Repeated transfusions of packed red blood cells (PRBCs) is currently the simplest and most used technique for chronic transfusion programs. However, iron overload is one of the major side effects of this therapy. More developed methods exist, notably the apheresis of RBC (erythrapheresis), which is currently the safest and most efficient method. However, it is costly, complicated, and cannot be implemented everywhere, nor is it suitable for all patients. Manual exchange transfusions combine one or more manual phlebotomies with a PRBC transfusion.
At the Reference Center of Sickle Cell Disease, we set up a continuous method of manual exchange transfusion that is feasible for all hospital settings, demands no specific equipment, and is widely applicable. In terms of HbS decrease, stroke prevention, and iron overload prevention, this method showed comparable efficiency to erythrapheresis. In cases where erythrapheresis is not available, this method can be a good alternative for patients and care centers.

We have outlined a method of continuous manual exchange transfusion for the treatment of sickle cell disease in patients. This safe protocol was designed to effectively limit iron overload in patients in need of chronic transfusions and can be used extensively without any special equipment.

Children with sickle cell anemia (SCA) may be at risk of cerebral vasculopathy and strokes, which can be prevented by chronic transfusion programs. ...

Real-time Pressure-volume Analysis of Acute Myocardial Infarction in Mice

Acute myocardial infarction can lead to acute heart failure and cardiogenic shock. The evaluation of hemodynamics is critical for the evaluation of any potential therapeutic approach directed against acute left ventricular (LV) dysfunction. Current imaging modalities (e.g., echocardiography and magnetic resonance imaging) have several limitations since data on LV pressure cannot directly be measured. LV catheterization in mice undergoing coronary artery occlusion could serve as a novel method for a real-time evaluation of LV function.
At the beginning of the procedure, mice were anesthetized followed by endotracheal intubation. For LV catheterization, the right carotid artery was exposed via middle-neck incision. The catheter was introduced and placed into the LV cavity. Left thoracotomy was conducted and the left main coronary artery (LCA) was ligated. To induce reperfusion, the suture was released after 45 min. Pressure-volume data was recorded at all times.
Ligation of the LCA caused a decrease in LV systolic function as evidenced by a 30% reduction in stroke volume, LV ejection fraction (EF), and cardiac output. Maximum dP/dt as a parameter for LV contractility was also significantly reduced and diastolic function was severely impaired (minimum dP/dt -40%). Reperfusion over a period of 20 min did not lead to a complete recovery of LV function.
Real-time pressure-volume analysis served as a valid procedure for monitoring cardiac function during acute myocardial infarction in mice. Maintaining stable anesthesia and a standardized surgical approach was crucial to ensure valid results. As the early phase of acute myocardial infarction is critical for morbidity and mortality, the delineated method could be beneficial for preclinical evaluation of new strategies for cardioprotection.

Acute myocardial infarction in mice induces acute but incompletely characterized changes in left ventricular (LV) function. LV catheterization in mice undergoing coronary artery occlusion serves as a novel method for a real-time evaluation of LV function.

Acute myocardial infarction can lead to acute heart failure and cardiogenic shock. The evaluation of hemodynamics is critical for the evaluation of any ...

Evaluation of Coronary Flow Reserve After Myocardial Ischemia Reperfusion in Rats

Coronary artery disease is the leading cause of death worldwide. After an acute myocardial infarction, early and successful myocardial intervention via recanalization of the coronary artery is the most effective strategy for reducing the size of ischemic myocardium. The coronary microvasculature cannot be visualized and imaged&#160;in vivo, but there are several invasive and noninvasive techniques that can be used to assess parameters which depend directly on coronary microvascular function. The endothelial function after ischemia reperfusion can be assessed also at the level of the coronary circulation via the coronary flow reserve (CFR).&#160;In this study, peak velocity of left anterior descending (LAD) coronary arteries was measured in rats in vivo via Transthoracic Doppler Echocardiography during resting and stress challenge (induced by Dobutamine). A normal heart can increase its coronary blood flow up to four times above the resting values during stress induction. Following ischemia reperfusion, we found a significantly diminished CFR, which can be used as a marker of coronary microvascular dysfunction. CFR has opened a window on the importance of microvascular dysfunction and has been shown to predict cardiovascular risk independent of whether the severe obstructive disease is present.

Coronary flow reserve (CFR), is defined as the ratio of maximal coronary blood flow to the resting coronary blood flow. We present a protocol for evaluating CFR in rats via ultrasound, which offers the opportunity to predict cardiovascular risk factors in the absence of obstructive coronary disease.

Coronary artery disease is the leading cause of death worldwide. After an acute myocardial infarction, early and successful myocardial intervention via ...

Postconditioning with Lactate-enriched Blood for Cardioprotection in ST-segment Elevation Myocardial Infarction

The beneficial effects of reperfusion therapy for ST-segment elevation myocardial infarction (STEMI) is attenuated by reperfusion injury. No approach has been proven successful in preventing this injury in the clinical setting to date. Meanwhile, a novel approach for cardioprotection in patients with STEMI, i.e., postconditioning with lactate-enriched blood (PCLeB), has recently been reported. PCLeB is a modification of the original protocol of postconditioning, aimed at increasing the delay in the recovery from tissue acidosis produced during ischemia. This was sought to achieve controlled reperfusion with tissue oxygenation and minimal lactate washout. In this modified postconditioning protocol, the duration of each brief reperfusion is gradually increased in a stepwise manner from 10 to 60 s. Each brief ischemic period lasts for 60 s. At the end of each brief reperfusion, injection of lactated Ringer&#39;s solution (20&#8211;30 mL) is performed directly into the culprit coronary artery immediately before the balloon inflation and the balloon is quickly inflated at the lesion site, so that the lactate is trapped inside the ischemic myocardium during each brief repetitive ischemic period. After seven cycles of balloon inflation and deflation, full reperfusion is performed. Stenting is performed thereafter, and the percutaneous coronary intervention is completed. Excellent in-hospital and 6 month outcomes in a limited number of patients with STEMI treated using PCLeB have already been reported. This method article provides a detailed description of each step of the PCLeB procedures.

Herein, we present a protocol for postconditioning with lactate-enriched blood, which is a novel approach for cardioprotection. This protocol comprises&#160;intermittent reperfusion and timely coronary injections of lactated Ringer&#39;s solution. This can be applied to ST-segment elevation myocardial infarction patients who undergo primary percutaneous coronary intervention.

The beneficial effects of reperfusion therapy for ST-segment elevation myocardial infarction (STEMI) is attenuated by reperfusion injury. No approach has ...

Predicting Amputation using Local Circulating Mononuclear Progenitor Cells in Angioplasty-treated Patients with Critical Limb Ischemia

Critical limb ischemia (CLI) represents an advanced stage of the peripheral arterial disease. Angioplasty improves the blood flow to the lower limb; however, some patients irreversibly progress to limb amputation. The extent of vascular damage and the mechanisms of vascular repair are factors affecting post-angioplasty outcome. Mononuclear Progenitor Cells (MPCs) are reactive to vascular damage and repair, with the ability to reflect vascular diseases. The present protocol describes quantification of MPCs obtained from blood circulation from vessel close to the angioplasty site, as well as its relationship with endothelial dysfunction and its predictive ability for limb amputation in the next 30 days after angioplasty in patients with CLI.

Lower limb amputation may occur even after angioplasty of obstructed vessels in Critical Limb Ischemia (CLI). Mononuclear Progenitor Cells (MPCs) reflect vascular repair. The present protocol describes the quantification of MPCs from circulation close to angioplasty, and its relationship with endothelial dysfunction and prediction of lower limb amputation.

Critical limb ischemia (CLI) represents an advanced stage of the peripheral arterial disease. Angioplasty improves the blood flow to the lower limb; ...

Operating Transverse Aortic Constriction with Absorbable Suture to Obtain Transient Myocardial Hypertrophy

Based on twice transverse aortic constrictions (TACs) in mice, it is proved that myocardial hypertrophic preconditioning (MHP) could attenuate cardiomyocyte hypertrophy and slow down progression to heart failure. For novices, however, the MHP model is usually quite difficult to establish because of the technical obstacles in ventilator operation, opening the chest repeatedly, and bleeding caused by debanding. To facilitate this model, to increase the surgical success rate and to reduce the incidence of bleeding, we switched to absorbable sutures for the first TAC combing with a ventilator-free technique. Using a 2-week absorbable suture, we demonstrated that this procedure could cause significant myocardial hypertrophy in 2 weeks; and 4 weeks after surgery, myocardial hypertrophy was almost completely regressed to the baseline. Using this protocol, the operators could master the MHP model easily with a lower operation mortality.

This protocol presents an improved method to obtain transient myocardial hypertrophy with absorbable suture, simulating left ventricular hypertrophy decrease after removing pressure overload. It could be valuable for the studies on myocardial hypertrophic preconditioning.

Based on twice transverse aortic constrictions (TACs) in mice, it is proved that myocardial hypertrophic preconditioning (MHP) could attenuate ...

Induction of Myocardial Infarction and Myocardial Ischemia-Reperfusion Injury in Mice

Acute myocardial infarction is a common cardiovascular disease with high mortality. Myocardial reperfusion injury can counteract the beneficial effects of heart reflow and induce secondary myocardial injury. A simple and reproducible model of myocardial infarction and myocardial ischemia-reperfusion injury is a good tool for researchers. Here, a customizable method to create a myocardial infarction (MI) model and MIRI by precision ligation of the left anterior descending coronary artery (LAD) through micromanipulation is described. Accurate and reproducible ligature positioning of the LAD helps obtain consistent results for heart injury. ST-segment changes can help to identify model accuracy. The serum level of cardiac troponin T (cTnT) is used to assess the myocardial injury, cardiac ultrasound is employed to evaluate the myocardial systolic function, and Evans-Blue/triphenyl tetrazolium chloride staining is used to measure infarct size. In general, this protocol reduces procedure duration, ensures controllable infarct size, and improves mouse survival.

Here we describe a simple and reproducible method that can induce myocardial infarction or myocardial ischemia-reperfusion injury in mice by precision ligation of the left anterior descending coronary artery through micromanipulation.

Acute myocardial infarction is a common cardiovascular disease with high mortality. Myocardial reperfusion injury can counteract the beneficial effects of ...

Improved Rodent Model of Myocardial Ischemia and Reperfusion Injury

Myocardial ischemia and reperfusion injury (MIRI), induced by coronary heart disease (CHD), causes damage to the cardiomyocytes. Furthermore, evidence suggests that thrombolytic therapy or primary percutaneous coronary intervention (PPCI) does not prevent reperfusion injury. There is still no ideal animal model for MIRI. This study aims to improve the MIRI model in rats to make surgery easier and more feasible. A unique method for establishing MIRI is developed by using a soft tube during a key step of the ischemic period. To explore this method, thirty rats were randomly divided into three groups: sham group (n = 10); experimental model group (n = 10); and existing model group (n = 10). Findings of triphenyltetrazolium chloride staining, electrocardiography, and percent survival are compared to determine the accuracies and survival rates of the operations. Based on the study results, it has been concluded that the improved surgery method is associated with a higher survival rate, elevated ST-T segment, and larger infarct size, which is expected to mimic the pathology of MIRI better.

Myocardial ischemia-reperfusion model of rat heart is improved by using a self-made retractor, polyvinyl chloride tube, and a unique knotting method. Electrocardiogram, triphenyltetrazolium chloride and histological staining, and percent survival analysis results showed that the improved model group has higher success and survival rates than the already existing model group.

Myocardial ischemia and reperfusion injury (MIRI), induced by coronary heart disease (CHD), causes damage to the cardiomyocytes. Furthermore, evidence ...

Adjunctive Exosome Therapy: Enhancing Myocardial Recovery Post-CABG Surgery

Surgical Porcine Model of Chronic Myocardial Ischemia Treated by Exosome-laden Collagen Patch and Off-pump Coronary Artery Bypass Graft

Chronic myocardial ischemia resulting from progressive coronary artery stenosis leads to hibernating myocardium (HIB), defined as myocardium that adapts to reduced oxygen availability by reducing metabolic activity, thereby preventing irreversible cardiomyocyte injury and infarction. This is distinct from myocardial infarction, as HIB has the potential for recovery with revascularization. Patients with significant coronary artery disease (CAD) experience chronic ischemia, which puts them at risk for heart failure and sudden death. The standard surgical intervention for severe CAD is coronary artery bypass graft surgery (CABG), but it has been shown to be an imperfect therapy, yet no adjunctive therapies exist to recover myocytes adapted to chronic ischemia. To address this gap, a surgical model of HIB using porcine that is amenable to CABG and mimics the clinical scenario was used. The model involves two surgeries. The first operation involves implanting a 1.5 mm rigid constrictor on the left anterior descending (LAD) artery. As the animal grows, the constrictor gradually causes significant stenosis resulting in reduced regional systolic function. Once the stenosis reaches 80%, the myocardial flow and function are impaired, creating HIB. An off-pump CABG is then performed with the left internal mammary artery (LIMA) to revascularize the ischemic region. The animal recovers for one month to allow for optimal myocardial improvement prior to sacrifice. This allows for physiologic and tissue studies of different treatment groups. This animal model demonstrates that cardiac function remains impaired despite CABG, suggesting the need for novel adjunctive interventions. In this study, a collagen patch embedded with mesenchymal stem cell (MSC)-derived exosomes was developed, which can be surgically applied to the epicardial surface distal to LIMA anastomosis. The material conforms to the epicardium, is absorbable, and provides the scaffold for the sustained release of signaling factors. This regenerative therapy can stimulate myocardial recovery that does not respond to revascularization alone. This model translates to the clinical arena by providing means of physiological and mechanistic explorations regarding recovery in HIB.

Author Spotlight: Enhancing Coronary Artery Revascularization

This study presents a surgical porcine model of chronic myocardial ischemia due to progressive coronary artery stenosis, resulting in impaired cardiac function without infarction. Following ischemia, animals undergo off-pump coronary artery bypass graft with epicardial placement of stem cells-derived exosomes-laden collagen patch. This adjunctive therapy improves myocardial function and recovery.

Chronic myocardial ischemia resulting from progressive coronary artery stenosis leads to hibernating myocardium (HIB), defined as myocardium that adapts ...