Left Ventricular Volume Changes After Amyl Nitrite and Nitroglycerin in Man as Measured by Ultrasound

The therapeutic effect of nitrites in myocardial ischemia is considered to be due in part to a reduction of left ventricular volume but measurement of this parameter in man has been difficult. The technique of echocardiography was used to measure changes in left ventricular end-diastolic volume (LVEDV) and end-systolic volume (LVESV) after administration of amyl nitrite (AN) and nitroglycerin (NG) in 20 normal subjects. Control LVEDV was 131 ± 8 ml (mean ±SEM) and LVESV 30 ± 2 ml. After AN, LVEDV fell 18 ± 2% (P < 0.001) and LVESV by 57 ± 3% (P < 0.001) in 15 sec to 1 min. Heart rate (HR) rose from 68 ± 3 to 108 ± 4 beats/min at 1 min and blood pressure (BP) fell from 119/69 ± 3/2 to 99/47 ± 4/3 mm Hg. Following NG, LVEDV fell 11 ± 2% (P < 0.001) and LVESV 21 ± 3% (P < 0.001) within 2-5 min. HR rose from 65 ± 2 to 72 ± 3 beats/min and BP fell from 111/67 ± 3/2 to 102/70 ± 5/2 mm Hg at 3 min. Cardiac output increased from 6.9 ± 0.3 to 11 ± 0.9 L/min 30 sec after AN while no significant change occurred with NG. Stroke volume decreased from 101 ± 6 to 93 ± 5 ml/beat 5 min after NG while no significant change occurred after AN. This study has shown that both AN and NG produce significant decreases in LVEDV and LVESV which may contribute to their beneficial effects in myocardial ischemia.