Delayed improvement inexercise capacity after cardioversion ofatrial fibrillation tosinus rhythm

SUMMARY Insome patients symptomsimprove after therestoration ofsinus rhythmfromatrial fibrillation. Toassessthesize andmechanism ofsuchchange, exercise capacity andpulsed Doppler left ventricular inflow velocities were assessed in20patients withestablished atrial fibrillation. Treadmill exercise capacity was assessed bymeasuring maximal oxygen consumption and anaerobic threshold before andon day1and28daysafter elective DC cardioversion. Therelative contribution ofatrial contraction to left ventricular filling was determined byrelating the maximumheight oftheA wave tothemaximumheight oftheEwave (A/E) oftheDoppler velocity timecurve.Cardioversion was successful in14patients. Maximaloxygen consumption and anaerobic threshold were unchanged on day1andincreased byday28inall14patients. The percentageimprovement was inversely related tothebaseline values; however, theabsolute improvement was small inall patients. Themean A/Eratio increased significantly fromday1today 28inall14patients. Thustherestoration ofsinus rhythm was associated witha delayed improvement inexercise capacity that may inpartbeduetoa slowimprovement inatrial contractility andpeakcardiac outputafter cardioversion.