In normal condition during ventricular systole, the left ventricle is the first to begin contracting, but the right ventricle is the first to expel blood. How can you explain this difference? There are two different reasons! And in dilated cardiomyopathy of the left ventricle, the ventricle can become enormously enlarged. Explain why this might lead to regurgitation of blood through the mitral valve (blood flowing from the ventricle back into the left atrium) during ventricular systole.