Effect of isosorbide dinitrate on submaximal exercise capacity of patients with chronic left ventricular failure

Hydralazine and nitrates alone or combined for the management of chronic heart failure: A systematic review

BACKGROUND

Hydralazine (H) and nitrates (Ns), when combined, reduced morbidity and mortality in some trials of chronic heart failure (CHF). It is unclear whether either agent used alone provides similar benefits. We aimed to evaluate the effects of H and/or N in patients with CHF.

METHODS

A systematic review of randomised trials assessing the effects of H and N in CHF. For meta-analysis, only the endpoints of all-cause mortality and cardiovascular mortality were considered.

RESULTS

In seven trials evaluating H&N in 2626 patients, combination therapy reduced all-cause mortality (OR 0.72; 95% CI 0.55-0.95; p=0.02), and cardiovascular mortality (OR 0.75; 95% CI 0.57-0.99; p=0.04) compared to placebo. However, when compared to angiotensin converting enzyme inhibitors (ACEIs), combination therapy was associated with higher all-cause mortality (OR 1.35; 95% CI 1.03-1.76; p=0.03), and cardiovascular mortality (OR 1.37; 95% CI 1.04-1.81; p=0.03). For N alone, ten trials including 375 patients reported all-cause mortality and showed a trend to harm (13 deaths in those assigned to nitrates and 7 to placebo; OR 2.13; 95% CI 0.88-5.13; p=0.09). For H alone, three trials showed no difference in all-cause mortality compared to placebo (OR 0.96; 95% CI 0.37-2.47; p=0.93), and two trials suggested inferiority to ACEI (OR 2.28; 95% CI 1.03-5.04; p=0.04).

CONCLUSIONS

Compared to placebo, H&N reduces mortality in patients with CHF. Whether race or background therapy influences benefit is uncertain, but on direct comparison H&N appears inferior to ACEI. There is little evidence to support the use of either drug alone in CHF.

A randomized pilot study of aortic waveform guided therapy in chronic heart failure

BACKGROUND

Medication treatment decisions in heart failure (HF) are currently informed by measurements of brachial artery pressure, but ventricular afterload is more accurately represented by central aortic pressure, which differs from brachial pressure. We sought to determine whether aggressive titration of vasoactive medicines beyond goal-directed heart failure medical therapy (GDMT) based upon aortic pressure improves exercise capacity and cardiovascular structure-function.

METHODS AND RESULTS

Subjects with chronic HF (n=50) underwent cardiopulmonary exercise testing, echocardiography, and arterial tonometry to measure aortic pressure and augmentation index, and were then randomized to aortic pressure-guided treatment (active, n=23) or conventional therapy (control, n=27). Subjects returned for 6 monthly visits wherein GDMT was first optimized. Additional vasoactive therapies were then sequentially added with the goal to reduce aortic augmentation index to 0% (active) or if brachial pressure remained elevated (control). Subjects randomized to active treatment experienced greater improvement in peak oxygen consumption compared with controls (1.37±3.76 versus -0.65±2.21 mL min(-1) kg(-1), P=0.025) though reductions in aortic augmentation index were similar (-7±9% versus -5±6%, P=0.46). Forward stroke volume increased while arterial elastance and left ventricular volumes decreased in all participants, with no between-group difference. Subjects randomized to active treatment were more likely to receive additional vasoactive therapies including nitrates, aldosterone antagonists and hydralazine, with no increased risk of hypotension or worsening renal function.

CONCLUSIONS

Maximization of goal-directed medical therapy in heart failure patients may enhance afterload reduction and lead to reverse remodeling, while additional medicine titration based upon aortic pressure data improves exercise capacity in patients with heart failure.

Nitrates in congestive heart failure

Nitrates are commonly used in the therapy of congestive heart failure (CHF). They exert beneficial hemodynamic effects by decreasing left ventricular filling pressure and systemic vascular resistance while modestly improving cardiac output. The improvement in left ventricular function caused by nitrates is the result of combined reduction in outflow resistance and mitral regurgitation, while decreased pericardial constraint and subendocardial ischemia may also contribute to the process. With continuous nitrate administration, complete arterial tolerance develops, while venous tolerance appears to be only partial. The major mechanism of tolerance is loss of vascular smooth muscle sensitivity to nitrates. An increase in total blood volume occurring during the first few hours of an acute administration may partly contribute to tolerance. The importance of reflex neurohumoral activation is controversial; although it may contribute to tolerance in CHF, its role does not appear to be major. Chronic continuous nitrate therapy in CHF improves submaximal and maximal exercise tolerance. In combination therapy with hydralazine, isosorbide dinitrate reduces mortality, although to a lesser extent than the angiotensin converting enzyme inhibitor enalapril. Intravenous or sublingual nitrates are first-line agents in the therapy of acute pulmonary edema. In severe CHF, refractory to standard medical therapy, a short course of intravenous nitroglycerin, with or without inotropic agents, can help break the vicious spiral of CHF. Because tolerance occurs without nitrate-free intervals and until an optimal schedule of administration is determined, it makes good sense to include a nightly nitrate-free interval when prescribing nitrates for CHF in order to maintain maximal benefit during the hours of activity.

Role of isosorbide dinitrate in management of chronic congestive heart failure

Congestive heart failure is accompanied by a number of compensatory mechanisms that may overshoot the mark. Among these are excessive arteriolar and venous constriction. Nitrates are effective in producing venodilation, redistributing blood from the chest to the periphery, and lowering right and left atrial pressures. Although oral isosorbide dinitrate is effective in producing acute beneficial hemodynamic effects, it usually does not increase exercise tolerance in the short term. Prolonged administration, however, does increase exercise tolerance and improve clinical class. Isosorbide dinitrate can be effectively combined with an arteriolar dilator such as hydralazine, which increases cardiac output. Such vasodilator therapy is symptomatically effective in patients with heart failure, although there is no evidence to date to suggest a prolongation of life.

Relation of right ventricular ejection fraction to exercise capacity in chronic left ventricular failure

Although the left ventricle is traditionally viewed as the heart's main pumping chamber, no correlation has been shown between left ventricular (LV) ejection fraction (EF) at rest and exercise capacity in patients with chronic LV failure. Because vasodilators with venodilating activity increase exercise capacity more than predominant arterial dilators in patients with LV failure, right ventricular (RV) function may relate to exercise capacity in these patients. In 25 patients with chronic LV failure, caused by coronary artery disease in 12 patients and idiopathic dilated cardiomyopathy in 13 patients, RVEF and LVEF at rest were measured by radionuclide angiography. Maximal upright bicycle exercise testing was also performed to determine maximal oxygen consumption, which averaged only 13 +/- 4 ml/min/kg. The LVEF at rest was 26 +/- 10% and did not correlate with maximal oxygen consumption (r = 0.08). However, the RVEF was 41 +/- 12% and correlated with maximal oxygen consumption (r = 0.70, p less than 0.001) in the same patients. The correlation was stronger (r = 0.88) in patients with coronary artery disease than in those with idiopathic dilated cardiomyopathy (r = 0.60). Thus, RVEF at rest is more predictive of exercise capacity than LVEF in the same patients with chronic LV failure. These results are consistent with the clinical observation that only venodilating agents increase exercise capacity of patients with chronic LV failure.