Comparative evaluation of isosorbide-5-mononitrate and nitroglycerin in chronic congestive heart failure

Pulmonary Hypertension with Left Heart Disease: Prevalence, Temporal Shifts in Etiologies and Outcome

INTRODUCTION

Pulmonary hypertension has many causes. While it is conventionally thought that the most prevalent is left heart disease, little information about its proportion, causes, and implications on outcome is available.

METHODS

Between 1993 and 2015, 12,115 of 66,949 (18%) first adult transthoracic echocardiograms were found to have tricuspid incompetence gradient ≥40 mm Hg, a pulmonary hypertension surrogate. Left heart disease was identified in 8306 (69%) and included valve malfunction in 4115 (49%), left ventricular systolic dysfunction in 2557 (31%), and diastolic dysfunction in 1776 (21%). Patients with left heart disease, as compared with those without left heart disease, were of similar age, fewer were females (50% vs 63% P <.0001), and they had higher tricuspid incompetence gradient (median 48 mm Hg [interquartile range 43, 55] vs 46 mm Hg [42, 54] P <.0001). In reviewing trends over 20 years, the relative proportions of systolic dysfunction decreased and diastolic dysfunction increased (P for trend <.001), while valve malfunction remained the most prevalent cause of pulmonary hypertension with left heart disease. Independent predictors of mortality were age (hazard ratio [HR] 1.05; 95% CI, 1.04-1.05; P <.0001), tricuspid incompetence gradient (HR 1.02; 95% CI, 1.01-1.02, P <.0001 per mm Hg increase), and female sex (HR 0.87; 95% CI, 0.83-0.91, P <.0001).

RESULTS

Overall, left heart disease was not an independent risk factor for mortality (HR 1.04; 95% CI, 0.99-1.09; P = .110), but patients with left ventricular systolic dysfunction and with combined systolic dysfunction and valve malfunction had increased mortality compared with patients with pulmonary hypertension but without left heart disease (HR 1.30; 95% CI, 1.20-1.42 and HR 1.44; 95% CI, 1.33-1.55, respectively; P <.0001 for both).

CONCLUSIONS

Pulmonary hypertension was found to be associated with left heart disease in 69% of patients. Among these patients, valve malfunction and diastolic dysfunction emerged as prominent causes. Left ventricular dysfunction carries additional risk to patients with pulmonary hypertension.

Pulmonary Hypertension Associated with Left-Sided Heart Disease

Pulmonary hypertension (PH) denotes a poor prognosis in patients with left-sided heart disease. No study has demonstrated long-term benefit from PH drugs such as prostanoids, endothelin antagonists, and phosphodiesterase-5 inhibitors. In some cases, cautious use of PH drugs may be indicated. However, theoretic and practical concerns limit any formal recommendations.

Mechanisms of action of nitrates

Glyceryl trinitrate, isosorbide dinitrate, and isosorbide-5-mononitrate are organic nitrate esters commonly used in the treatment of angina pectoris, myocardial infarction, and congestive heart failure. Organic nitrate esters have a direct relaxant effect on vascular smooth muscles, and the dilation of coronary vessels improves oxygen supply to the myocardium. The dilation of peripheral veins, and in higher doses peripheral arteries, reduces preload and afterload, and thereby lowers myocardial oxygen consumption. Inhibition of platelet aggregation is another effect that is probably of therapeutic value. Effects on the central nervous system and the myocardium have been shown but not scrutinized for therapeutic importance. Both the relaxing effect on vascular smooth muscle and the effect on platelets are considered to be due to a stimulation of soluble guanylate cyclase by nitric oxide derived from the organic nitrate ester molecule through metabolization catalyzed by enzymes such as glutathione S-transferase, cytochrome P-450, and possibly esterases. The cyclic GMP produced by the guanylate cyclase acts via cGMP-dependent protein kinase. Ultimately, through various processes, the protein kinase lowers intracellular calcium; an increased uptake to and a decreased release from intracellular stores seem to be particularly important.

Intravenous isosorbide-5-mononitrate in the treatment of acute myocardial infarction

The action of isorsorbide-5-mononitrate (IS-5-MN) infusion (range 6.0 to 10.0 mg/hour) was studied in 24 patients with and without acute heart failure (hemodynamic subsets I to IV) during acute myocardial infarction. Hemodynamic measurements were performed by right-sided cardiac catheterization. Intravenous IS-5-MN demonstrated significant hemodynamic effects compared with baseline values. In subsets I and II, a decrease in pulmonary wedge pressure (PWP) and in cardiac index (CI), without significant changes in heart rate, mean arterial pressure or systemic vascular resistance index were demonstrated. In subsets III and IV, a major increase in CI and a decrease in systemic vascular resistance index, as well as a decrease in PWP were found. Again no changes occurred in mean arterial pressure and heart rate. The dosage was similar in subsets I to IV (8.0, 7.9, 7.8 and 7.3 mg/hour); thus, the differences in the responses could not be attributed to dosage. It appears that several different patterns of hemodynamic IS-5-MN action exist, assuming that IS-5-MN operates on preload and afterload levels. The action of IS-5-MN mechanisms seems to be dependent on an initial hemodynamic subset. No patient had any deleterious hemodynamic effects. A decrease in CI in subsets I and II was not of clinical importance with these dosages. No nitrate tolerance during 9.0 hours of continuous therapy appeared.(ABSTRACT TRUNCATED AT 250 WORDS)

Nitrates: why and how should they be used today? Current status of the clinical usefulness of nitroglycerin, isosorbide dinitrate and isosorbide-5-mononitrate

Nitrates are highly effective both in terminating acute attacks of angina pectoris and in the prophylaxis of symptomatic and asymptomatic myocardial ischemia. Preload reduction by venodilatation is the prevailing mechanism of nitrates in patients with chronic stable angina and is the unique feature distinguishing them from beta and calcium-channel blockers. Nitrates dilate coronary arteries not only in pre- and poststenotic vessels, but also in eccentric lesions. In patients with endothelial dysfunction, nitrates seem to be the physiological substitute for endothelium-derived relaxing factor. During the past decade, however, there has been substantial evidence of a clinically relevant loss of the anti-ischemic effects ("nitrate tolerance"). Many studies with oral dosing of isosorbide dinitrate or isosorbide-5-mononitrate at least three times daily have proven nitrate tolerance in patients with coronary artery disease and/or congestive heart failure. Complete loss of anti-ischemic effects after repetitive, continuous patch attachments has also been found. As we first showed in 1983, intermittent therapy with once-daily ingestion of high-dose sustained-release isosorbide dinitrate was successful in preventing the development of tolerance. Similarly, tolerance to isosorbide-5-mononitrate also does not develop when it is ingested once daily. It is now generally accepted that a daily low-nitrate interval is required to prevent tolerance development. Although the minimal patch-free interval required to prevent tolerance needs further investigation, a 12-h patch-free interval should prevent tolerance in most patients. The prolonged duration of action of once-daily high-dosage administration of sustained-release formulations, the improved patient compliance with a single daily administration, and the increased likelihood of maximal anti-ischemic effects are important reasons for recommending high single daily doses of isosorbide dinitrate or isosorbide-5-mononitrate.