A very late systolic click can occur in patients with idiopathic non-obstructive cardiomyopathy and severe left ventricular dysfunction, contrasting with the mid-systolic clicks typically seen in structurally normal hearts.
Two patients with seriously impaired left ventricular function, abnormal left ventricular conduction on the electrocardiogram, mitral regurgitation, and a very late systolic click are reported. Idiopathic non-obstructive cardiomyopathy seemed to be the cause of the left ventricular dysfunction in both cases. The mitral valve was anatomically normal at the time of operation in one patient, except for dilatation of the annulus, and the mitral regurgitation appeared to be secondary to left ventricular failure. The very late timing of the mitral systolic clicks in these two patients may be related to a large left ventricular end-diastolic volume and impaired left ventricular function, or to an abnormal sequence of excitation of the left ventricle. The timing of the late systolic click in these patients is in contrast to that in patients with mid systolic clicks, hearts of normal size, and little cardiac disability.
Mercer et al. (Tue,) studied this question.