Nitrates in Heart Failure

Transcriptional profiles associated with aging and middle age-onset caloric restriction in mouse hearts

To provide a global analysis of gene expression in the aging heart, we monitored the expression of 9,977 genes simultaneously in 5- and 30-month-old male B6C3F(1) mice by using high-density oligonucleotide microarrays and several statistical techniques. Aging was associated with transcriptional alterations consistent with a metabolic shift from fatty acid to carbohydrate metabolism, increased expression of extracellular matrix genes, and reduced protein synthesis. Caloric restriction (CR) started at 14 months of age resulted in a 19% global inhibition of age-related changes in gene expression. Interestingly, CR also resulted in alterations in gene expression consistent with preserved fatty acid metabolism, reduced endogenous DNA damage, decreased innate immune activity, apoptosis modulation, and a marked cytoskeletal reorganization. These observations provide evidence that aging of the heart is associated with specific transcriptional alterations, and that CR initiated in middle age may retard heart aging by inducing a profound transcriptional reprogramming.

The role of organic nitrates in the treatment of heart failure

Nitrates have been widely used in the treatment of patients with chronic congestive heart failure. Although the use of these drugs has not been approved by the Food and Drug Administration, multiple studies have shown their favorable effects. Organic nitrates have been shown to have a beneficial effect on ischemia, hemodynamic profile, magnitude of a mitral regurgitation, endothelial function, and cardiac remodeling. These drugs, when used in combination with hydralazine, have improved exercise capacity and survival. Recent studies have shown that the use of nitrates in patients already treated with standard heart failure therapy, including angiotensin converting enzyme (ACE) inhibitors, resulted in hemodynamic improvement, marked enhancement of exercise tolerance, reduction of left ventricular size, and augmentation of systolic function. These data suggest a role for organic nitrates as an adjunctive therapy to ACE inhibitors in patients with chronic heart failure and for nitrates in combination with hydralazine as an alternative treatment in patients who are intolerant to ACE inhibitors.

Nitrates in the treatment of congestive heart failure

Nitrates have been widely used for the treatment of patients with chronic congestive heart failure. Although the use of these drugs has not been evaluated by large-scale studies traditionally used for evaluation of new therapy, multiple studies over the years have demonstrated their favorable effects. Organic nitrates have been shown to have a beneficial effect on ischemia, hemodynamic profile, magnitude of mitral regurgitation, endothelial function, and cardiac remodeling. These drugs alone or in combination with hydralazine have improved exercise capacity, maximal oxygen consumption, cardiac function, and survival. The use of nitrates in patients with heart failure has been limited by reduced responsiveness (resistance) and early development of tolerance. Nitrate resistance is due to reduced vascular response and results in the need to use a larger dose of any nitrate preparation when used for the treatment of patients with heart failure compared to patients without heart failure. Recent information suggests that nitrate tolerance is caused by increased levels of superoxide at the vascular wall, which leads to reduced nitric oxide level and to increased sensitivity to vasoconstrictive mechanisms, such as endothelin and angiotensin II. Intermittent dosing of nitrates allowing a 12-hour nitrate-free interval is effective in preventing nitrate tolerance and is, therefore, recommended. Recent information suggests that augmentation of nitrate dose by the use of an escalating dose regimen and a concomitant use of hydralazine can prevent or overcome the effect of nitrate tolerance in patients with heart failure.

Prevention of tolerance to hemodynamic effects of nitrates with concomitant use of hydralazine in patients with chronic heart failure

OBJECTIVES

This study was designed to determine the effect of oral hydralazine on the development of nitrate tolerance in patients with chronic congestive heart failure.

BACKGROUND

Early development of nitrate tolerance with either continuous administration of intravenous or topical nitrate preparations or frequent dosing of oral nitrates leads to significant attenuation of nitrate-mediated hemodynamic and anti-ischemic effects. In recent animal experiments, prevention of nitroglycerin-induced hemodynamic tolerance with a concomitant use of hydralazine was demonstrated. This finding may have important clinical relevance.

METHODS

Twenty-eight patients with chronic heart failure due to left ventricular systolic dysfunction were randomized to receive either a continuous infusion (24 h) of nitroglycerin alone (group I, 14 patients) or concomitantly with oral hydralazine (75 mg four times a day [group II, 14 patients]). The effect of nitroglycerin in each group was evaluated by analysis of variance for repeated measures. The power of the analysis to detect a 5.4-mm Hg (20%) change in mean pulmonary artery wedge pressure was 90%.

RESULTS

Baseline hemodynamic variables as well as the initial hemodynamic response to nitroglycerin were comparable in both groups. Compared with the initial response to nitroglycerin, a significant attenuation of effect was found in group I at 24 h in mean (+/- SE) pulmonary artery pressure (27 +/- 4% vs. 10 +/- 3%, p < 0.05) and mean pulmonary artery wedge pressure (40 +/- 4% vs. 16 +/- 4%, p < 0.05). In group II, conversely, oral hydralazine prevented nitroglycerin-induced hemodynamic tolerance and resulted in a persistent effect on mean pulmonary artery and wedge pressures throughout the study period (31 +/- 3% vs. 27 +/- 4%, p = 0.13 and 37 +/- 4% vs. 34 +/- 6%, p = 0.40, respectively). In addition, the initial effect on blood pressure was attenuated at 24 h in group I (5 +/- 2% vs. 12 +/- 3%, p < 0.05) but not in group II (15 +/- 3% vs. 17 +/- 2%, p = 0.46).

CONCLUSIONS

In patients with chronic heart failure due to left ventricular systolic dysfunction, the concomitant use of oral hydralazine prevents early development of nitrate tolerance and results in a persistent nitrate-mediated hemodynamic effect on systemic and pulmonary artery and left ventricular filling pressures. These data may support the concurrent use of hydralazine in patients with heart failure treated with organic nitrates.