Name: assessment of right ventricular structure and function in mouse model of pulmonary artery constriction by transthoracic echocardiography
Uploaded: 2014-02-03T14:45:00
Description: Watch this Scientific Journal Video about Assessment of Right Ventricular Structure and Function in Mouse Model of Pulmonary Artery Constriction by Transthoracic Echocardiography at JoVE.com

We thank Fred Roberts and Chris White for exemplary technical support. We thank Brigham Women&#8217;s Hospital Cardiovascular Physiology Core for providing with the instrumentation and the funds for this work. This work was supported in part by NHLBI grants HL093148, HL086967, and HL 088533(RL), K99HL107642 and the Ellison Foundation (SC).

Surgical Procedure
<ol>
	<li>Obtain 8 week-old male C57BL/6 mice and acclimate for one week before any experimental procedures are performed.</li>
	<li>Prior to imaging, pulmonary artery occlusion is performed as described previously14&#160;in accordance with AVMA guidelines and approved IACUC protocols. 
	Echocardiographic Images Acquisition and Measurements 
	All abbreviations used are summarized in Table 1.</li>
</ol>
1. Parasternal Long Axi...

<ol>
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We demonstrate that TTE provides a sensitive and reproducible methodology for routine assessment of RV structure and function in mice. Before the advent of TTE, studies of the RV largely focused on RVSP measurement via right heart catheterization, a terminal and invasive procedure6,9,11,17.
Prior reports have described a variety of techniques for performing right heart measurements3,4,11,17-19. However, the majority of previous studies reported RV size and structural data...

Historically, prognostic assessment of heart failure has focused on the LV, which is easy to image via echocardiography. Numerous studies on LV structure and function using echocardiography have led to the establishment of normal values for LV structure and function1,5,6. Measurements of LV size and systolic function obtained from two-dimensional and Color Doppler images are of great importance as they allow visual delineation of compartments and geometry in great detail for the LV7. M-Mode is often used for measuring LV dimensions and fractional shortening (FS) in mice. Inter-observer and intra-observer variability are low for diameter measurements using this mode, but wall thickness measurements tend to be quite variable7. Pulsed Doppler with color (PW or Color Doppler) has been used to evaluate valvular regurgitation8,9.
Similar to LV, the RV plays an important role and is a significant predictor of morbidity and mortality in patients afflicted with cardiopulmonary disease1,7,10. However, echocardiographic evaluation of RV is inherently challenging due to its complex shape5,11 and its retrosternal position that blocks the ultrasound waves8,9. RV is a crescent shaped structure wrapping around the LV and has a complex anatomy with thin walls that are accustomed to low pressure and resistance to pulmonary vasculature6. To overcome elevated vascular resistance (PVR), the RV first increases in size and undergoes hypertrophies. In chronic diseases like pulmonary hypertension or pulmonary vascular disease, RV undergoes progressive dilatation, eventually resulting in the deterioration of systolic and diastolic function4,5,10.
Echocardiography plays an important role in the screening and diagnosis of PAH despite some limitations present in its clinical diagnostic capability. The main advantage of TTE lies in that it is noninvasive and that it can be performed on lightly sedated, or even conscious animals9. TTE also provides a reasonable estimate of PA pressures, as well as an ongoing assessment of changes in RV structure and function12,13. Due to technical advances in TTE, which include the development of high-frequency mechanical probes, allowing axial resolution of approximately 50 &#956;m at a depth of 5-12 mm, high frame rates (greater than 300 frame/sec), and high sampling rates, echocardiography is a choice tool for imaging the rapidly contracting small sized mouse heart8,11.
Longitudinal monitoring of RV function using multiple views, including 2-dimensional (2D) short and long axis, M-mode and Doppler acoustic windows provide complementary information of RV anatomy and function. Collectively, this methodology permits complete longitudinal assessment of RV hemodynamics in physiology and pathological setting4,7.
Herein, we provide a detailed step-by-step methodology of using noninvasive TTE to characterize RV anatomical and functional changes secondary to PAC in mice.

<table border="0" cellpadding="0" cellspacing="0" width="609">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="61">
			<td height="61" style="height:61px;width:157px;">High Frequency Ultrasound</td>
			<td style="width:108px;">FUJIFILM VisualSonics, Inc.</td>
			<td style="width:96px;">Vevo 2100</td>
			<td style="width:248px;"></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:157px;">High-frequency Mechanical Transducer</td>
			<td style="width:108px;">FUJIFILM VisualSonics, Inc.</td>
			<td style="width:96px;">MS250, MS550D, MS400</td>
			<td style="width:248px;"></td>
		</tr>
		<tr height="67">
			<td height="67" style="height:67px;width:157px;">Millar Mikro Pressure Catheter</td>
			<td style="width:108px;">Millar</td>
			<td style="width:96px;">SPR-1000</td>
			<td style="width:248px;"></td>
		</tr>
	</tbody>
</table>

assessment of right ventricular structure and function in mouse model of pulmonary artery constriction by transthoracic echocardiography

Emerging clinical data support the notion that RV dysfunction is critical to the pathogenesis of cardiovascular disease and heart failure1-3. Moreover, the RV is significantly affected in pulmonary diseases such as pulmonary artery hypertension (PAH). In addition, the RV is remarkably sensitive to cardiac pathologies, including left ventricular (LV) dysfunction, valvular disease or RV infarction4. To understand the role of RV in the pathogenesis of cardiac diseases, a reliable and noninvasive method to access the RV structurally and functionally is essential.
A noninvasive trans-thoracic echocardiography (TTE) based methodology was established and validated for monitoring dynamic changes in RV structure and function in adult mice. To impose RV stress, we employed a surgical model of pulmonary artery constriction (PAC) and measured the RV response over a 7-day period using a high-frequency ultrasound microimaging system. Sham operated mice were used as controls. Images were acquired in lightly anesthetized mice at baseline (before surgery), day 0 (immediately post-surgery), day 3, and day 7 (post-surgery). Data was analyzed offline using software.
Several acoustic windows (B, M, and Color Doppler modes), which can be consistently obtained in mice, allowed for reliable and reproducible measurement of RV structure (including RV wall thickness, end-diastolic&#160;and end-systolic dimensions), and function (fractional area change, fractional shortening, PA peak velocity, and peak pressure gradient) in normal mice and following PAC.
Using this method, the pressure-gradient resulting from PAC was accurately measured in real-time using Color Doppler mode and was comparable to direct pressure measurements performed with a Millar high-fidelity microtip catheter. Taken together, these data demonstrate that RV measurements obtained from various complimentary views using echocardiography are reliable, reproducible and can provide insights regarding RV structure and function. This method will enable a better understanding of the role of RV cardiac dysfunction.

In this study, baseline echocardiography was performed 48 hr&#160;prior to surgery. Mice were randomized into two groups. Mice received pulmonary artery occlusions (PAC) and sham operations (Sham). Echocardiography was performed at day 0, 3, and 7 following surgical procedure.&#160; The animals were euthanized immediately following the last echocardiography and hearts were harvested for histological assessment.&#160;Catheterization was conducted in subgroup (n=3 and 2 for day 0 and 7, respectively) of PAC mice to measure...

Watch this Scientific Journal Video about Assessment of Right Ventricular Structure and Function in Mouse Model of Pulmonary Artery Constriction by Transthoracic Echocardiography at JoVE.com

Assessment of Right Ventricular Structure and Function in Mouse Model of Pulmonary Artery Constriction by Transthoracic Echocardiography

Right ventricle (RV) dysfunction is critical to the pathogenesis of cardiovascular disease, yet limited methodologies are available for its evaluation. Recent advances in ultrasound imaging provide a noninvasive and accurate option for longitudinal RV study. Herein, we detail a step-by-step echocardiographic method using a murine model of RV pressure overload.

Emerging clinical data support the notion that RV dysfunction is critical to the pathogenesis of cardiovascular disease and heart failure1-3. Moreover, ...

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