Ultrasonographic examination of the heart in sheep

Right parasternal echocardiographic reference values in the healthy male Iranian Shall sheep

BACKGROUND

Among the large animals, the heart of sheep is functionally and structurally very similar to the human heart. In research, sheep are used as an animal model to study the process of cardiac disease pathogenesis and treatment. Therefore, determining the normal values of the heart structures of sheep with echocardiography is of particular emphasis. The purpose of the present research is to define the normal echocardiography values of heart in Iranian Shall breed sheep.

MATERIALS AND METHODS

In 20 healthy Iranian Shall male sheep weighing 30-35 kg and aged 4-6 months, standing echocardiography was done from the right parasternal approach concentrated on the 3rd to 5th intercostal spaces by 2.5-5 MHz phased array transducer in the longitudinal and transverse views by B-mode, M-mode and Doppler systems. In M-mode echocardiographic, the parameters of interventricular septal, left ventricular internal diameter, left ventricular free wall, right ventricular free wall and right ventricular internal diameter in diastole and systole as well as end point septal separation, ejection fraction (EF) slope, aortic root diameter, left atrial appendage, left atrial diameter/aortic valve diameter, left ventricular ejection time, fractional shortening, end-diastolic volume, end-systolic volume, EF, stroke volume and cardiac output and in pulsed-wave spectral Doppler echocardiographic, the parameters of mitral valve maximum velocity (Vmax), mitral valve mean velocity (Vmean), mitral valve maximum pressure gradient (PGmax), mitral valve mean pressure gradient (PGmean), mitral valve velocity time integral (VTI), mitral valve E-wave (MV-E), MV-E pressure gradient, mitral valve A-wave (MV-A), MV-A pressure gradient, aortic Vmax, aortic valve Vmean, aortic valve PGmax, aortic valve PGmean, aortic valve VTI, left ventricular outflow tract (LVOT)-Vmax, LVOT-Vmean were measured.

RESULTS

All the sheep in this study were healthy and had no signs of heart disease. In this study, the parameters of M-mode and spectral Doppler echocardiographic were assessed and recognized in Iranian Shall sheep. The results demonstrated the parameters of echocardiographic could be dependably determined in Shall sheep which, established normal reference values for these parameters and left ventricular function indices in healthy Shall sheep. These results can be beneficial in appropriate imagination, recognition and measuring cardiac structures.

CONCLUSION

This study can be exerted as a reference for the assessment and diagnosis of heart diseases in sheep medicine and human cardiovascular research in sheep experimental models.

Ovine Model of Ischemic Mitral Regurgitation

Ischemic mitral regurgitation (IMR) is a common complication of ischemic heart disease that doubles mortality after myocardial infarction and is a major driving factor increasing heart failure. IMR is caused by left ventricular (LV) remodeling which displaces the papillary muscles that tether the mitral valve leaflets and restrict their closure. IMR frequently recurs even after surgical treatment. Failed repair associates with lack of reduction or increase in LV remodeling, and increased heart failure and related readmissions. Understanding mechanistic and molecular mechanisms of IMR has largely attributed to the development of large animal models. Newly developed therapeutic interventions targeted to the primary causes can also be tested in these models. The sheep is one of the most suitable models for the development of IMR. In this chapter, we describe the protocols for inducing IMR in sheep using surgical ligation of obtuse marginal branches. After successful posterior myocardial infarction involving posterior papillary muscle, animals develop significant mitral regurgitation around 2 months after the surgery.