determining the end-systolic and end-diastolic pressure-volume relationships in a murine heart failure model and transesophageal pacing

使用心房起搏方案探索 HR 依赖性心脏功能

Heart failure represents a leading cause of hospitalization and death across the globe, and heart failure with preserved ejection fraction (HFpEF) accounts for around 50% of all heart failure diagnoses. HFpEF is characterized by diastolic dysfunction and impaired exercise tolerance, and the associated hemodynamic abnormalities, such as diastolic dysfunction, can be clearly detected through exercise-stressed hemodynamic testing or MRI scans1,2.
In experimental models, however, available modalities for assessing the physiological abnormalities related to HFpEF are limited3,4. Treadmill exercise testing (TMT) is used to determine running time and distance, which might reflect exercise-stress cardiac hemodynamics; however, this method is susceptible to interference from extraneous variables such as the body weight, skeletal muscle strength, and mental status.
To circumvent these limitations, we have devised an atrial-pacing protocol that detects subtle but crucial changes in diastolic performance based on the heart rate (HR) and have validated its usefulness in a mouse model of HFpEF5. Several physiological factors contribute to exercise-related cardiac function, including the sympathetic nerve and catecholamine response, peripheral vasodilation, the endothelial response, and the heart rate6. Among these, however, the HR-pressure relationship (also called the Bowditch effect) is known as a critical determinant of cardiac physiological features7,8,9.
The protocol involves performing a conventional pressure-volume analysis at baseline to assess the systolic and diastolic function, including parameters such as the rate of pressure development (dp/dt), the end-systolic pressure-volume relationship (ESPVR), and the end-diastolic pressure-volume relationship (EDPVR). However, it should be noted that these parameters are influenced by the HR, which can vary between animals due to differences in their intrinsic heart rate. Additionally, the effects of anesthesia on the HR should also be considered. To address this, the HR was standardized by administering atrial pacing concomitantly with ivabradine, and cardiac parameter measurements were performed at incremental heart rates. Notably, the HR-dependent cardiac response distinguished HFpEF mice from the control group mice, while no significant differences were observed in the baseline PV loop measurements (using the intrinsic heart rate)5.
While this pacing protocol may seem relatively complicated, its success rate exceeds 90% when it is well understood. This protocol would provide a useful way to study the underlying mechanisms of diastolic dysfunction in HFpEF mouse models and help in the development of new treatments for this condition.

作者聚焦：通过新型心房起搏方法研究小鼠模型中的 HR 依赖性心脏功能 

用于评估小鼠心力衰竭模型心率依赖性舒张功能的起搏控制程序

The heart rate-related relationship is important for determining cardiac characteristics, particularly, in HFpEF. This protocol aims to assess heart rate-dependent cardiac function. Any experimental models, available modalities for assessing heart rate-related cardiac function, are limited to treadmill exercise testing.The treadmill test, however, is influenced by variables such as body weight. To overcome these limitations, we have developed around atrial-pacing protocol to detect subtle, yet significant changes in the later performance that are linked to heart rate. Our protocol offers a variable tool for identifying cardiac dysfunction, manifested by heart rate changes.It also presents a number approach to studying diastolic dysfunction in mirroring heart failure models, particularly in HFpEF.

Watch this Scientific Journal Video about Determining the End-Systolic and End-Diastolic Pressure-Volume Relationships in a Murine Heart Failure Model and Transesophageal Pacing at JoVE.com

确定小鼠心力衰竭模型和经食管起搏中的收缩末期和舒张末期压力-容积关系

首先，将麻醉的动物放置在手术区域，确保手术部位得到充分的剃须和消毒。接下来，通过标准外科手术正确放置电导导管。要记录和分析基线压力量或 PV 回路，请在实验室图表软件中选择基线参数，然后单击立即分析按钮。选择基线选项。打开血流动力学表并选择平均值数据。通过使用镊子压缩 IVC 进行下腔静脉或 IVC 闭塞。在软件中，手动选择左心室压和容积都降低的IVC闭塞点。然后，通过选择闭塞选项，然后单击“立即分析”按钮，记录至少 20 个心动周期的 PV 循环，而 IVC 保持闭塞状态。要进行经食管起搏，请将 2 法式四极电极导管插入食管。将导管连接到脉冲刺激器，然后继续确定心房捕获阈值。为了将心率减慢到每分钟 400 次以下，腹膜内注射每公斤 20 毫克伊伐布雷定。稳定后，获取 20 个连续心动周期的 PV 环，同时以每分钟 400 至 700 次的不同速率起搏心脏。基线PV环数据显示，对照组和HFpEF小鼠之间的舒张期参数（如弛豫时间常数，最小压力变化率和舒张末期压力容积关系或EDPVR）没有显着差异。然而，HFpEF小鼠表现出较高的血压和动脉弹性蛋白，在心室收缩期间表现出典型的山形PV环。该PV环路与心室肌肉直接接触压力传感器引起的尖峰不同。值得注意的是，使用心房起搏，可以清楚地区分对照小鼠和HFpEF小鼠之间的舒张功能。在对照组中，弛豫时间常数和EDPVR均随着起搏率的增加而改善。而在HFpEF组中，随着心率随着心房起搏的增加，弛豫时间常数和EDPVR均恶化。

determining-end-systolic-end-diastolic-pressure-volume-relationships

Research

JoVE Journal

Biology

Determining the End-Systolic and End-Diastolic Pressure-Volume Relationships in a Murine Heart Failure Model and Transesophageal Pacing

127 次观看.  The University of Tokyo Hospital. 首先，将麻醉的动物放置在手术区域，确保手术部位得到充分的剃须和消毒。接下来，通过标准外科手术正确放置电导导管。要记录和分析基线压力量或 PV 回路，请在实验室图表软件中选择基线参数，然后单击立即分析按钮。选择基线选项。打开血流动力学表并选择平均值数据。通过使用镊子压缩 IVC 进行下腔静脉或 IVC 闭塞。在软件中，手动选择左心室压和容积?...

视频: 确定小鼠心力衰竭模型和经食管起搏中的收缩末期和舒张末期压力-容积关系

A Pacing-Controlled Procedure for the Assessment of Heart Rate-Dependent Diastolic Functions in Murine Heart Failure Models

Heart failure with preserved ejection fraction (HFpEF) is a condition characterized by diastolic dysfunction and exercise intolerance. While exercise-stressed hemodynamic tests or MRI can be used to detect diastolic dysfunction and diagnose HFpEF in humans, such modalities are limited in basic research using mouse models. A treadmill exercise test is commonly used for this purpose in mice, but its results can be influenced by body weight, skeletal muscle strength, and mental state. Here, we describe an atrial-pacing protocol to detect heart rate (HR)-dependent changes in diastolic performance and validate its usefulness in a mouse model of HFpEF. The method involves anesthetizing, intubating, and performing pressure-volume (PV) loop analysis concomitant with atrial pacing. In this work, a conductance catheter was inserted via a left ventricular apical approach, and an atrial pacing catheter was placed in the esophagus. Baseline PV loops were collected before the HR was slowed with ivabradine. PV loops were collected and analyzed at HR increments ranging from 400 bpm to 700 bpm via atrial pacing. Using this protocol, we clearly demonstrated HR-dependent diastolic impairment in a metabolically induced HFpEF model. Both the relaxation time constant (Tau) and the end-diastolic pressure-volume relationship (EDPVR) worsened as the HR increased compared to control mice. In conclusion, this atrial pacing-controlled protocol is useful for detecting HR-dependent cardiac dysfunctions. It provides a new way to study the underlying mechanisms of diastolic dysfunction in HFpEF mouse models and may help develop new treatments for this condition.

The present protocol describes obtaining the pressure-volume relationship through transesophageal pacing, which serves as a valuable tool in evaluating diastolic function&#160;in mouse models of heart failure.

Heart failure with preserved ejection fraction (HFpEF) is a condition characterized by diastolic dysfunction and exercise intolerance. While ...

科研

生物学

Instrument and Animal Preparation for Catheterization in a Murine Heart Failure Model

To begin, place a conductance catheter in normal saline, then connect it to an MPVS module, comprising the PowerLab 8/35 and a pressure volume unit. Electronically calibrate the pressure and volume by recording the predetermined pressure and volume parameters on the MPVS module. For the murine heart failure model, anesthetize the animal, and ensure that the surgical site is adequately shaved and disinfected.Expose the trachea and insert an endotracheal tube into it. Locate the internal jugular vein beneath the sternocleidomastoid muscle. Then insert a central venous catheter consisting of PE10 Silastic connected to a 30 gauge needle into the jugular vein.Administer a bolus infusion of five to six microliters per gram of body weight of 10%Albumin in sodium chloride for about three minutes. Follow this with a constant infusion rate of five to 10 microliters per minute.

小鼠心力衰竭模型导管插入术的器械和动物准备

Surgical Procedure for Left Ventricular Catheterization (Open Chest Approach) in a Murine Heart Failure Model

To begin, place the anesthetized animal in the surgical area, ensuring that the surgical site is adequately shaved and disinfected. Make a horizontal incision below the xiphoid process, measuring two to three centimeters in length. Then, use blunt scissors to separate the skin from the chest wall.Using electrical cautery, make lateral cuts on both sides through the chest wall. Cut through the diaphragm to expose the heart. Gently remove the pericardium from the heart using forceps.Next, insert a 27 gauge needle into the apex of the left ventricle, then retro greatly insert a conductance catheter into the left ventricle via the puncture hole, and adjust the catheter position until obtaining a square shaped pressure volume loop.

小鼠心力衰竭模型中左心室导管插入术（开胸入路）的外科手术

To begin, place the anesthetized animal in the surgical area, ensuring that the surgical site is adequately shaved and disinfected. Next, properly place the conductance catheter through standard surgical procedures. To record and analyze the baseline pressure volume or PV loop, in the lab chart software, select the baseline parameters, then click the Analyze Now button.Select the baseline option. Open the hemodynamic table and select the average data. Perform inferior vena cava or IVC occlusion by compressing the IVC using forceps.In the software, manually select the point of occlusion of IVC where both left ventricular pressure and volume decrease. Then record the PV loop for at least 20 cardiac cycles while the IVC remains occluded by selecting the occlusion option and then clicking the Analyze Now button. To perform transesophageal pacing, insert a 2-French tetrapolar electrode catheter into the esophagus.Connect the catheter to a pulse stimulator, then proceed to determine the atrial capture threshold. To slow the heart rate below 400 beats per minute, administer 20 milligrams per kilogram of ivabradine intraperitoneally. Following stabilization, acquire 20 continuous cardiac cycles of PV loops while pacing the heart at different rates from 400 to 700 beats per minute.The baseline PV loop data showed no significant differences in diastolic parameters, such as the relaxation time constant, the minimum rate of pressure change, and the end diastolic pressure volume relationship, or EDPVR, between the control and HFpEF mice. However, the HFpEF mice exhibited higher blood pressure and arterial elastins, demonstrating a typical mountain-shaped PV loop during ventricular systole. This PV loop was distinguishable from a spike caused by direct contact of the ventricular muscle on the pressure transducer.Notably, using atrial pacing, the diastolic function could be clearly distinguished between the control and HFpEF mice. In the control group, both the relaxation time constant and EDPVR improved as the pacing rate increased. Whereas in the HFpEF group, both the relaxation time constant and EDPVR worsened as the heart rate increased with atrial pacing.

Saline Calibration and Aortic Flow Calibration in a Murine Heart Failure Model

To begin, place the anesthetized animal in the surgical area, ensuring that the surgical site is adequately shaved and disinfected. Catheterize the animal through standard surgical procedures. Next, hold the ventilator and administer 5 to 10 microliters of hypertonic saline solution intravenously through the central venous catheter.During the saline injection, record the changes in pressure and volume, and utilize power lab to calculate the VP value. To avoid disrupting the volume signal, position the mouse on its left side, then make a lateral thoracotomy towards the spine between the third and fifth thoracic vertebrae. Gently dissect a small part of the descending aorta using forceps, then place a vascular flow probe over the aorta to measure the cardiac output.