Hemodynamic consequences of afterload reduction in patients with valvular abnormalities

Synergistic effect of captopril and dobutamine on left ventricular pressure-volume and pressure-shortening relations in severe cardiac failure

The acute effects of captopril and dobutamine, alone and in combination, on left ventricular contractility were assessed from left ventricular end-systolic pressure-volume and pressure-shortening relations in 6 patients with severe end-stage cardiac failure. Dobutamine was given by constant intravenous infusion on two occasions 48 hours apart, on one of these occasions the patient also received oral captopril in a dose of 37 +/- 12 mg 6-hourly. Pressures and cardiac index were measured, and left ventricular volumes and ejection fraction computed from simultaneously recorded radionuclide ventriculography. Dobutamine alone did not cause a statistically significant increase in stroke index, stroke work index, cardiac index and ejection fraction, although pulmonary capillary wedge pressure and right atrial pressure fell (P less than 0.05). There was no change in systemic or pulmonary vascular resistance nor in arterial blood pressure. Following administration of captopril, diastolic arterial pressure decreased (P less than 0.05), and the dobutamine challenge produced a greater and significant rise in stroke and stroke work index (P less than 0.05) and cardiac index (P less than 0.01). The left ventricular contractile state was unaltered by captopril but appeared to increase with dobutamine and more so during combined therapy with captopril and dobutamine, indicating a synergistic effect of the two drugs when given in combination.

Effect of captopril on left ventricular end-systolic pressure-volume and stress-shortening relations in severe cardiac failure

The effects of captopril on cardiovascular dynamics and left ventricular (LV) contractility were studied in 11 patients with severe congestive heart failure and very poor global LV function. Pressures were measured using a flow-guided catheter, cardiac output by thermodilution, and LV contraction and ejection fraction by simultaneous radionuclide angiography. Ventricular loading conditions were altered by sublingual isosorbide dinitrate to facilitate construction of LV pressure-volume and stress-shortening curves. Captopril decreased mean arterial pressure (p less than 0.02) and systemic vascular resistance, while stroke and cardiac index increased in most patients. Left ventricular ejection fraction increased from 18 +/- 5 to 22 +/- 7% (p less than 0.05), but contractility, assessed from end-systolic pressure-volume and end-systolic pressure-shortening relations, was unchanged or decreased slightly. Heart rate and double product also tended to decrease. In contrast, arteriovenous oxygen difference widened and calculated total oxygen consumption increased during captopril therapy (p less than 0.05). The study showed that captopril improved forward blood flow, total oxygen extraction, and LV ejection fraction following the decrease impedance to LV emptying but not at the expense of an increase in ventricular contractility. This makes captopril an attractive drug for patients with end-stage cardiac failure and a severely damaged myocardium.

Noninvasive assessment of left ventricular wall stress in chronic congestive heart failure patients

Therapy with prazosin can improve the condition of patients with congestive heart failure due to its vasodilating action. Therefore nine patients with volume overloaded left ventricles due to aortic insufficiency and mitral insufficiency received 1 mg. of prazosin four times a day for two weeks. Peak and end-systolic wall stress were estimated using a noninvasive echocardiographic technique. The peak systolic wall stress in this group was 155 x 10(3) dynes/cm2 which is similar to the reported normal value. However, the end systolic wall stress was 101 x 10(3) dynes/cm2 which is much higher than the reported normal values. Following the administration of oral prazosin, the end systolic stress was normalized while the peak systolic stress was reduced below normal. As a result of therapy with prazosin, the ejection fraction, the percentage of change in the minor axis, and the velocity of circumferential fiber shortening significantly increased. Thus, the oral administration of prazosin can improve left ventricular function in patients with mitral insufficiency and aortic insufficiency.

Enhancement of phentolamine by nitrates in patients with congestive heart failure

Phentolamine dilates the resistance bed and to a lesser degree the capacitance bed, while the nitrates have the opposite action. Therefore, in 7 patients with congestive heart failure due to congestive cardiomyopathy, hemodynamic measurements were made using a Swan Ganz thermodilution catheter and cardiac output computer. The patients received 5 mg of an IV infusion of phentolamine administered at 0.3 mg/minute. At the end of the infusion, the pressures and cardiac output were obtained. Then, 2 1/2 inches of nitroglycerin ointment was applied to the chest, and the hemodynamic parameters were obtained 30 minutes later. Phentolamine produced a significant reduction in the right and left ventricular filling pressures and a significant increase in the cardiac output. The hemodynamic effects of phentolamine are known to persist for an hour or longer. The addition of nitroglycerin ointment led to a further reduction in the right and left ventricular filling pressures. Thus, the combination of phentolamine and nitrates can be effectively used in the treatment of congestive heart failure.

Noninvasive assessment of load reduction in chronic congestive heart failure patients

Therapy with phentolamine can improve the condition of patients with congestive heart failure due to the inotropic effect of this drug as well as its vasodilating action. Therefore, 8 patients with volume-overloaded left ventricles due to aortic insufficiency and mitral insufficiency received 50 mg of phentolamine 4 times a day for 2 weeks. Peak and end systolic wall stress were estimated using a noninvasive echocardiographic technique. The peak systolic wall stress in this group was 133 X 10(3) dynes/sq cm, which is similar to the reported normal value. However, the end systolic wall stress was 89 X 19(3) dynes/sq cm, which is much higher than the reported normal values. After PO administration of phentolamine, the end systolic stress was normalized while the peak systolic stress was reduced below normal. As a result of therapy with phentolamine, the ejection fraction, the percentage of change in the minor axis, and the velocity of circumferential fiber shortening significantly increased. Thus, PO administration of phentolamine can improve left ventricular function in patients with mitral insufficiency and aortic insufficiency.