Systolic Time Intervals in Mitral Incompetence

¹ Cardiac Unit, Wentworth Hospital and the University of Natal, Durban, South Africa

The systolic time intervals were measured in 17 patients with pure mitral incompetence (MI) in sinus rhythm. These were compared with hemodynamic and angiographic measurements of the severity of mitral regurgitation and the degree of left ventricular dysfunction. Pre-ejection phase (PEP), on an average, was normal in patients with MI, and the patients had normal left ventricular function. Left ventricular ejection time (LVET) was shortened: LVET was related to the forward stroke index (r = +0.81), and the abbreviation of LVET reflected the severity of mitral incompetence. Total electromechanical systole (Q-S₂) was shortened; this was due to the shortened LVET (r = +0.95). The ratio PEP/LVET reflected the left ventricular ejection fraction, but the ratio was increased in patients with severe mitral incompetence due to the shortening of LVET. In a second comparative group of patients with congestive cardiomyopathy (COCM) and MI there was a significant prolongation of PEP and a further reduction in forward stroke index and LVET. In these patients, Q-S₂ was normal and the PEP/LVET ratio was greatly increased.