Effect ofVentricular Extrasystoles on Closure ofMitral Valve

SUMMARY Mitral valve function was assessed byroentgenvideodensitometry. Mitral reflux was rarewhensingle ventricular ectopic systoles were produced byelectronic stimulation oftheright orleft ventricle atvarious timesinthecardiac cycle. Itwas also rareduring thecompensatory pause after theectopic systole orwiththefollowing postectopic systole. Recurrent ventricular ectopic systoles interposed once per cycle were associated with minorreflux whenintroduced inmid-cycle. Suchextrasystoles occurred lateenough inthecardiac cycle fortheventricle torelax after theprimarysystole andforthe mitral valve toopen before theextrasystole. Theextrasystolic contractions were, however,weakandincapable ofopeningtheaortic valve. Wheninterposed early inthe cardiac cycle, extrasystolic potentiation oftheprimary ventricular contraction occurred, andno or minimal mitral reflux was observed.