Postexercise Systolic Time Intervals in the Midsystolic Click Syndrome

Abstract

Postexercise systolic time intervals (STI) were measured in ten patients (PMV group) with auscultatory evidence of the midsystolic click syndrome (i.e. one or more systolic nonejection clicks alone or in association with a late systolic murmur), and compared to eight age-matched volunteers (control group) with no evidence of heart disease. Following measurement of supine STIs, the subjects pedalled an upright bicycle ergometer at progressive work loads until a target heart rate (HR) representing 85% of the age-adjusted maximum was attained, or an abnormal end point was noted. Immediately postexercise, a repeat measurement of STIs, was obtained. A shortened or unchanged postexercise left ventricular ejection time corrected for HR (ΔLVETc) and a marked shortening of total electromechanical systole after exercise (ΔQS2c) constituted a normal STI response to stress testing and was noted in all control subjects. All of the PMV group exhibited evidence of left ventricular dysfunction characterized by a prolonged ΔLVETc. It is concluded that an abnormal STI response to exercise consistent with left ventricular dysfunction can be demonstrated in patients with prolapse of the mitral valve by the response of the STI.