The study population consisted of 11 consecutive patients with severe chronic mitral regurgitation by clinical criteria who underwent supine rest and exercise radionuclide angiography for clinical indications at the Mayo Clinic over a two-year period. There were seven men and four women, ages 43-81 (mean 58 ±11). Eight patients had mitral valve prolapse, two had rheumatic heart disease, and in one patient the severe MR resulted from subacute bacterial endocarditis. All had mild-to-moderate symptoms by clinical criteria (four were considered New York Heart Assocation class 1, four were in class 2, and three were in class 3). review
The following were grounds for exclusion: 1) other valvular heart disease; 2) known coronary artery disease (prior myocardial infarction or definite angina pectoris); 3) congenital heart disease; 4) significant conduction system disease (bundle branch block or pacemaker dependency); 5) atrial or ventricular dysrhythmias; 6) resting left ventricular ejection fraction ^0.50; and 7) resting regional wall motion abnormalities. Most importantly, none of these patients was receiving vasodilators at the time of the study or during the month prior to the study, although four patients were receiving digitalis prepara* tions, four diuretics, two anti-dysrhythmic therapy, and one was taking a very low dose of propranolol (20 mg daily).
The patients were exercised by supine bicycle ergometry (Quinton Instruments). Three ECG leads were monitored continuously and a standard 15-lead ECG was recorded every minute to monitor ST-segment changes. The blood pressure in the right arm was measured by cuff every three minutes. The standard exercise began at a workload of 300 kg-m/min and was increased every three minutes in increments of300 kg-m/min. The protocol was modified occasionally at the discretion of the monitoring physician. Symptom-limited exercise tests were performed with exercise terminated at one of the following end-points: 1) moderate angina; 2) serious dysrhythmias; 3) marked dyspnea or fatigue; or 4) ^2 mm ST-segment depression.