Response of the left ventricle to nitroglycerin in patients with and without mitral regurgitation

Vasoactive drugs in chronic regurgitant lesions of the mitral and aortic valves

This review examines the results of vasodilator therapy in patients with chronic regurgitant lesions of the aortic and mitral valves. The analysis includes those studies which provide data on hemodynamic measurements, left ventricular systolic function, ventricular volumes and regurgitant flow. In patients with chronic aortic or mitral regurgitation, the short-term administration of nitroprusside, hydralazine, nifedipine or an angiotensin-converting enzyme (ACE) inhibitor produces salutary hemodynamic effects. The major difference in the response to combined preload and afterload reduction (i.e., nitroprusside) in patients with aortic versus mitral regurgitation was that forward stroke volume generally increased and ejection fraction remained unchanged in mitral regurgitation, whereas ejection fraction generally increased and forward stroke volume remained unchanged in aortic regurgitation. These observations suggest that a reciprocal relation between regurgitant and forward flow characterizes the response to preload and afterload reduction in mitral regurgitation (through a preload-dependent dynamic regurgitant orifice), whereas correction of afterload mismatch dominates the response in aortic regurgitation. In studies of long-term vasodilator therapy in patients with chronic aortic regurgitation, a reduction in left ventricular volumes and regurgitant fraction, with or without an increase in ejection fraction, has been observed during treatment with hydralazine, nifedipine and ACE inhibitors. Patients with the largest, sickest hearts generally benefit the most from treatment with vasoactive drugs. Nonetheless, favorable ventricular remodeling has been reported in asymptomatic patients, and long-term nifedipine use has delayed the need for operation in asymptomatic patients with chronic aortic regurgitation. For patients with chronic mitral regurgitation, definition of the etiology of the lesion is a prerequisite for choosing appropriate therapy. Excluding patients with obstructive hypertrophic cardiomyopathy and mitral valve prolapse, and some with fixed-orifice (i.e., rheumatic) mitral regurgitation, the signal importance of preload reduction suggests that the preferred long-term therapy for symptomatic chronic mitral regurgitation is an ACE inhibitor. There are no long-term studies that support the use of vasodilator therapy in asymptomatic patients with chronic mitral regurgitation.

Effects of isosorbide dinitrate on rheumatic and non-rheumatic mitral regurgitation

Isosorbide dinitrate was given to seven patients with isolated mitral regurgitation (three cases of rheumatic origin, four non-rheumatic) to assess its hemodynamic effects. The pulmonary capillary pressure, left ventricular end-diastolic pressure, left ventricular end-diastolic volume index, and the aortic pressure were all significantly reduced. The heart rate was significantly increased, while the systemic vascular resistance and the left ventricular contractility index were unchanged. The regurgitant flow increased by an average of 72.2% in the rheumatic group, but decreased by an average of 4.8% in the non-rheumatic group (p < 0.05). The forward cardiac output decreased slightly in both groups, but the difference was not significant (NS). It appears that isosorbide dinitrate has a more detrimental effect on cases of mitral regurgitation of rheumatic origin than on those of non-rheumatic origin. We suggest the difference in the responses is a consequence of the dynamic nature of the regurgitant orifice in the non-rheumatic group and the static nature of the orifice in the rheumatic group.

Dynamics of mitral regurgitation during nitroglycerin therapy: a Doppler echocardiographic study

Seven patients with decompensated chronic heart failure and functional mitral regurgitation were studied before and during administration of nitroglycerin at a mean dose of 42 micrograms/min (range 20 to 90 micrograms/min). Forward aortic flow obtained by pulsed Doppler increased significantly from 35 +/- 8 to 45 +/- 9 ml/beat (p less than 0.001) and correlated well with the cardiac output measured by thermodilution technique (r = 0.8). Whereas regurgitant mitral volume calculated from the difference between echocardiographic total stroke volume and forward aortic flow decreased significantly from 19 +/- 9 to 3 +/- 3 ml/beat (p less than 0.001), peak velocity of mitral regurgitant flow increased from 4.1 +/- 0.9 to 4.4 +/- 1.0 m/sec (p less than 0.05). The decrease in effective mitral regurgitation area derived from a modified Gorlin formula average 80%. Accordingly, in patients with decompensated chronic heart failure and functional mitral regurgitation, nitroglycerin decreases mitral regurgitant area substantially, and thus almost abolishes mitral regurgitation despite an increase in systolic pressure gradient between left ventricle and atrium. Moreover, the increase in forward flow can be entirely accounted for by the reduction in mitral regurgitant flow.

New concepts and drugs in the treatment of congestive heart failure

This article seeks to make clear the basic differences in the treatment of heart failure between therapeutic maneuvers that are aimed at improving the mechanical loading conditions of the heart and those that are aimed at augmenting the fundamental contractile or inotropic state of the myocardium. Emphasis is placed on recognizing that treatment expectations must be viewed within an age- or maturity-dependent framework, since a diminished margin of cardiocirculatory reserve exists in the smallest and youngest patients that limits the extent of benefit that may be derived from diverse treatment approaches.

Vasodilator and inotropic therapy for severe chronic heart failure: passion and skepticism

Although substantial progress has been made in the last 5 years in the development of vasodilator and inotropic drugs for the management of patients with severe chronic heart failure, much of the enthusiasm that surrounded the introduction of many of these agents has subsequently been tempered by reports of drug failure or adverse reactions. In this review and analysis, currently available vasodilator and inotropic agents are critically and comparatively evaluated to assess their respective advantages and limitations. It is apparent that the ability of most of these drugs to produce substantial clinical benefits in patients with severe heart failure has probably been overstated. Therapy fails to achieve the desired clinical results all too frequently, possibly as the result of: the choice of an ineffective drug; the administration of an effective drug in subtherapeutic doses; the administration of an effective drug to improperly selected patients; the failure of initial hemodynamic benefits to be sustained; the occurrence of severe or serious adverse reactions; and the failure to alter concomitant therapy appropriately. The present analysis indicates that there is no uniformly effective or safe vasodilator or inotropic drug for patients with severe heart failure; all agents have important limitations. Of the available therapeutic choices, however, long-term converting enzyme inhibition appears to produce more consistent hemodynamic and clinical benefits with an acceptable degree of adverse reactions than other pharmacologic approaches for the management of these severely ill patients.

Vasodilator therapy in chronic congestive heart failure

Vasodilator agents are relatively new additions to the armamentarium for the management of patients with congestive heart failure. Myocardial failure, irrespective of the aetiology, tends to create a vicious cycle characterised by reduced cardiac output and elevated systemic vascular resistance, which further decrease cardiac output by increasing left ventricular ejection impedance. The rationale for the use of vasodilators is to interrupt the vicious cycle by decreasing the left ventricular ejection impedance by peripheral vasodilatation. Although most vasodilator agents produce qualitatively similar haemodynamic responses, quantitatively their haemodynamic effects differ considerably. Knowledge of the haemodynamic effects of the various vasodilators helps in the selection of a particular drug for the management of such patients. This article reviews the mechanisms of action, haemodynamic effects, pharmacokinetics, clinical usage and adverse effects of non-parenteral vasodilator agents currently available for the management of patients with chronic heart failure.

New perspectives on therapeutic application of nitrates as vasodilator agents for severe chronic heart failure

Although nitrates produce marked decreases in ventricular filling pressures in patients with severe heart failure, their therapeutic value has long been believed to be limited because they were thought to exert minimal arterial dilating effects. Recently, however, new conceptual approaches to vasodilator drugs have been developed that have challenged this traditional view. These new perspectives indicate that nitrates exert dilator actions on both the arterial and venous circulations, and reduce both preload and afterload; such balanced circulatory responses are particularly evident when large doses of these drugs are used. Cardiac output increases markedly with nitrates in patients with a greatly increased systemic vascular resistance before treatment or with significant mitral regurgitation. The major reason for the limited increases in cardiac output noted in previous studies is the inclusion of patients with heart failure whose pretreatment values for cardiac output were within normal limits; in these persons nitrates markedly activate neurohumoral vasoconstrictor mechanisms that counteract the arterial dilating actions of these drugs. Long-term nitrate therapy attenuates exercise-induced increases in pulmonary venous pressures, which permit patients to undergo repeated submaximal exercise with fewer symptoms; this improves physical conditioning and exercise capacity, even in the absence of drug-related changes in cardiac output. The long-term hemodynamic and clinical benefits of nitrates in heart failure have been confirmed by two independent randomized double-blind placebo-controlled clinical trials.

A profile of intravenous nitroglycerin use in cardiopulmonary bypass surgery

We studied the indications for use, time to onset of effect, approximate effective concentration and therapeutic success of commercially prepared intravenous nitroglycerin (NTG) in 50 patients undergoing cardiopulmonary bypass (CPB) surgery. Nitroglycerin was used to treat systemic or pulmonary hypertension, myocardial ischaemia and ventricular failure. Twenty-one patients had more than one indication for NTG use. Nineteen of 22 patients with pulmonary hypertension, 12 of 13 patients with ischaemic changes, and 13 of 15 patients with ventricular failure improved during intravenous NTG administration. Hypertension during CPB was ameliorated in only six of ten instances. The time to onset of effect ranged from 4.1 +/- 0.8 to 7.8 +/- 2.8 minutes and the mean approximate effective NTG concentration varied from 1.7 +/- 0.3 to 2.9 +/- 0.7 micrograms . kg-1.min-1 (doses only approximate due to our use of an infusion system which absorbs NTG). Complications from intravenous NTG administration were not seen. We conclude that this NTG preparation facilitates treatment of prebypass hypertension, pulmonary hypertension, myocardial ischaemia and ventricular failure but is less effective for the treatment of hypertension during CPB.

Physiologic and pharmacologic determinants of vasodilator response: a conceptual framework for rational drug therapy for chronic heart failure

This article has attempted to summarize the increasing number of pharmacologic and physiologic variables that are being recognized as important determinants in the response to vasodilator therapy in patients with severe chronic heart failure. It is apparent that a careful consideration of many factors is necessary before proper selection of a specific drug can be made for a specific patient, since not all patients with refractory heart failure demonstrate beneficial hemodynamic and clinical responses to all agents. Each patient presents us with a unique set of physiologic variables; each drug has its own advantages and limitations. Identification of those subgroups of patients most likely to benefit from a specific agent or combination of agents is a major goal for future research. Although a number of hemodynamic variables can be made to improve acutely with a wide variety of vasodilator drugs, well tolerated sustained meaningful clinical benefits are probably observed in relatively few patients. Rational and successful vasodilator therapy is possible only through a highly individualized approach.

Effects of oral hydralazine on rest and exercise hemodynamics in patients with aortic or mitral regurgitation and left ventricular dysfunction

The hemodynamic effects of afterload reduction were studied at rest and during two levels of upright exercise in patients with aortic or mitral regurgitation and left ventricular dysfunction. Eleven patients underwent invasive hemodynamic monitoring before and after 50-70 mg of oral hydralazine was given ever 6 h for 48 h. At rest, heart rate and mean arterial pressure after hydralazine were unchanged from control. During exercise, there was no significant change in heart rate, but mean arterial pressure fell significantly during the first level of exercise. Systemic vascular resistance was elevated before hydralazine and was significantly reduced after treatment at both exercise levels. After hydralazine, the resting oxygen consumption was significantly elevated at rest but was unchanged during exercise, the arteriovenous oxygen difference was significantly narrowed at both rest and exercise, and the pulmonary capillary wedge pressure was also significantly lower at both rest and exercise. In this select group of patients who are not candidates for surgical valve replacement, chronic afterload reduction with oral hydralazine may result in increased cardiac performance, decreased pulmonary congestion, reduced myocardial oxygen demands, and improvement in resting and/or exertional symptoms.

Quantification of valve regurgitation by radionuclide angiography before and after valve replacement surgery

Radionuclide gated cardiac blood pool imaging was used to quantify the severity of valve regurgitation in 20 patients, by calculating the ratio of left ventricular to right ventricular stroke counts (end-diastolic minus end-systolic counts in right and left ventricular regions of interest). This ratio (the stroke index ratio) was substantially higher in patients with aortic and mitral regurgitation (3.91 +/- 1.45) than in a control group of 10 patients without regurgitation (1.32 +/- 0.15), p less than 0.001. The stroke index ratio correlated closely (r = 0.947) with measurements of regurgitant fraction derived from simultaneous determinations of total and forward stroke volumes during cardiac catheterization. After aortic and mitral valve replacement in 18 patients, the stroke index ratio decreased from 4.03 +/- 1.46 to 1.38 +/- 0.23 (p less than 0.001), a value not significantly different from that observed in patients without regurgitation. All three patients with residual postoperative regurgitation had a stroke index ratio greater than 2 standard deviations above the mean values for the control group (greater than 1.62), whereas the remaining 15 patients, who had no evidence of regurgitation, had values within the normal range. Therefore, radionuclide gated blood pool scanning provides a noninvasive method of quantifying valve regurgitation and assessing the results of medical or surgical interventions.

Effect of nitroglycerin ointment on hemodynamics in patients with mitral insufficiency

A reduction in impedance or afterload produces beneficial hemodynamic effects in patients with mitral regurgitation. This mechanism has been studied via intravenous infusion of nitroprusside, phentolamine, and hydralazine. But there is little information on the effect of nitroglycerin ointment in patients with mitral insufficiency. Thus 6 patients with mitral insufficiency underwent right and left heart catheterization. After the control hemodynamic measurements were recorded, a 2 1/2-inch strip of 2% nitroglycerin ointment was applied to the chest for half an hour. Pressure recordings and cardiac output were then repeated. The control cardiac index fell from 2.79 to a treatment value of 2.05 L/min/m2 (P < 0.01), while the stroke index also decreased from 29 to 22 ml/beat/m2 (P < 0.05). There was a nonsignificant increase in peripheral resistance. Thus nitroglycerin ointment can be detrimental when given to patients with mitral insufficiency.

Differences in hemodynamic effects of nitroprusside and prazosin in severe chronic congestive heart failure: evidence for a direct negative chronotropic effect of prazosin

To compare the hemodynamic effects of prazosin and nitroprusside in patients with severe congestive heart failure, nine patients with heart failure refractory to conventional therapy received oral prazosin and intravenous nitroprusside administered so as to produce a similar decrease in left ventricular filling pressure in each patient. By this comparison, both drugs produced similar decreases in mean right atrial pressure, mean pulmonary arterial pressure and systemic and pulmonary vascular resistance. However, with nitroprusside, cardiac index increased more (+0.97 versus +0.73 liters/min per m2, P less than 0.01) and mean arterial pressure decreased less (-13.7 versus -18.3 mm Hg, P less than 0.05) than with prazosin. Both drugs produced similar changes in stroke volume index (+11.7 cc/beat per m2 with nitroprusside and +12.5 with prazosin) and stroke work index (+8.1 g-m/m2 with nitroprusside and +6.6 with prazosin). Therefore, the differences in the hemodynamic responses observed with the two agents were due to the significantly greater decrease in heart rate with prazosin (-8 beats/min) than with nitroprusside (-2 beats/min, P less than 0.05). These clinical data support experimental evidence suggesting that there is a significant negative chronotropic action of prazosin independent of its peripheral vascular effects.

Beneficial effects of hydralazine in severe mitral regurgitation

The severity of mitral regurgitation is, in part, determined by aortic impedance to left ventricular outflow. Sodium nitroprusside acutely decreases regurgitant flow, but the importance of its dual vasodilating effects, the lowering of peripheral vascular resistance and increasing of venous capacitance, is unclear. We studied the hemodynamic response to intravenous hydralazine, which selectively acts on the arteriolar resistance bed, in 10 patients with severe mitral regurgitation. Hydralazine produced a 50% increase in forward stroke volume (22 +/- 2 to 33 +/- 3 ml/m2, P less than 0.001) and a 33% reduction in regurgitant stroke volume (40 +/- 6 to 27 +/- 6 ml/m2, P less than 0.001), with a resultant fall in pulmonary capillary wedge v wave and mean pressures. Unlike nitroprusside, it did not alter left ventricular end-diastolic volume or pressure. Oral hydralazine maintained this hemodynamic improvement for at least 48 hours and, in three patients, provided more sustained clinical improvement. We conclude that hydralazine, by virtue of its selective lowering of aortic impedance, reduces the amount of mitral regurgitation and thus may be a useful mode of interim or chronic therapy in selected patients.

The posterior left atrial echocardiogram of mitral regurgitation

The motion of the posterior wall of the normal left atrium has not been studied systematically. The superoposterior portion of the left atrium is adynamic throughout the cardiac cycle, whereas the inferoposterior portion is displaced posteriorly with left atrial filling during ventricular systole. In the present study, the left atrial diameter (LAD), the left atrial systolic motion (LASM) and the left atrial systolic velocity (LASV), were determined in the following groups of patients: 34 normals; eight patients with either coronary artery disease or aortic stenosis; six patients with aortic insufficiency; and three patients with ventricular septal defect. The results obtained were compared to 15 patients with angiographically documented mitral regurgitation. In the last group, the LAD (4.2 +/- .19 cm) and LASV (12.3 +/- 1.23 cm) and LASM (1.2 +/- 0.4 cm) were significantly greater reflecting the early accentuated filling of the left atrium induced by mitral regurgitation. As well, the product of these three parameters was greater in the mitral regurgitation group (63.2 +/- 7.34 cm3/sec) than in the other groups and patients with mild to moderate regurgitation had a significantly lower value than those with moderate to severe regurgitation (45.7 +/- 4.1 vs 78.5 +/- 10.9, P less than 0.02). The left atrial echocardiogram, therefore, is an aid in the diagnosis of mitral regurgitation and provides a rough index of the severity of the lesion.

Vasodilator treatment for acute and chronic heart failure

The current status of the use of vasodilator drugs in the treatment of acute and chronic heart failure has been reviewed. It is apparent that vasodilator treatment can be used effectively in some patients with heart failure with a beneficial haemodynamics response, and that vasodilator agents are likely to find an important place in the management of such patients. Vasodilator treatment may be associated with complications and must be used with care. Though several nonparenteral vasodilator agents have been investigated, no ideal drug is yet available for the treatment of chronic heart failure. Nevertheless, it is probable that suitable drugs will emerge and find an important place in the management of such patients.

The role of vasodilator therapy in heart failure

This article has attempted to summarize the current status of the therapeutic use of vasodilator drugs in acute and chronic heart failure. It is apparent from the increasing number of publications in this area that this alternative to more standard forms of therapy is likely to find a permanent and important place in the management of patients with heart disease. It should also be apparent that ideal drugs for the therapy of chronic heart failure are not yet available. Nevertheless, it is probable that such drugs will emerge and become at least as important as the routine use of digitalis in such patients.