Drugs and the heart. II. Nitrates

Nitrate therapy today

A review of nitrate therapy including a short summary of their physiological effects is presented. Both cardiac and non-cardiac indications are reviewed including esophageal spasm, spasm of bile ducts and urinary tract, Raynaud's disease, pulmonary hypertensive disorders, portal hypertension, bronchial asthma, and effect on arrhythmias.

Topical nitroglycerin prevents the pressor response to tracheal intubation and sternotomy in patients undergoing coronary artery bypass graft surgery

Thirty adult patients who underwent coronary artery bypass graft surgery were allocated randomly to one of two equal groups to receive either 2% nitroglycerin, or a placebo ointment, applied topically over an area of 5 cm by 10 cm, in a double-blind manner, 1 h before induction of anaesthesia. Premedication consisted of oral diazepam 5-10 mg, intramuscular morphine 0.2 mg.kg-1 and promethazine 0.4 mg.kg-1. Anaesthesia was induced with morphine 0.15-0.2 mg.kg-1 and thiopentone 3-5 mg.kg-1. Laryngoscopy and tracheal intubation were facilitated by suxamethonium 1.5 mg.kg-1, and pancuronium 0.1 mg.kg-1 was used for subsequent muscle relaxation. Anaesthesia was maintained with 0.5% halothane and 40% oxygen in nitrous oxide. A significant increase in blood pressure occurred during and after laryngoscopy and tracheal intubation, and following midline sternotomy in the control group. These changes were absent in patients pretreated with topical nitroglycerin. The nitroglycerin group also maintained a lower rate-pressure product than the control group. We conclude that topical nitroglycerin is a simple and useful pretreatment to prevent the pressor response to tracheal intubation and midline sternotomy in patients undergoing coronary artery bypass graft surgery.

Mechanisms of action and efficacy of nitrates in heart failure

Nitrates exert hemodynamic and possibly nonhemodynamic effects that result in reduced cardiac filling pressures, increased cardiac output, reduced pulmonary vascular pressures, and improvement in symptoms and exercise tolerance in patients with heart failure. Combined with hydralazine, chronic oral administration of isosorbide dinitrate has been demonstrated to improve survival when added to digoxin and diuretic therapy. A long-term improvement in left ventricular ejection fraction in these clinical studies has raised the possibility that the nitrates may be acting at least in part by inhibiting left ventricular remodeling. The precise role of nitrates and the optimal dosing regimen in the therapeutic armamentarium for heart failure, particularly in patients already treated with a converting enzyme inhibitor, remains to be established.

The haemodynamic effects of sublingual nitroglycerin spray in severe left ventricular failure

The use of sublingual nitroglycerin spray has been studied in twenty patients referred to our Intensive Care Unit for further treatment of severe left ventricular failure. Within five minutes of spray administration significant falls in pulmonary artery occlusion pressure, mean arterial pressure, heart rate, right atrial pressure and systemic vascular resistance occurred. Similarly significant increases in cardiac index, stroke volume index and left ventricular stroke work index were found. These results show a considerable improvement in the haemodynamic parameters of invasively monitored patients and we believe that its administration undoubtedly "buys time" for the critically ill patient. However, we would caution against its routine use at present in view of the potential problem of hypotension, until further information is available.

Nitrates in congestive heart failure

An important role for nitrates in the treatment of patients with congestive heart failure has been demonstrated. By dilating the venous and arterial vasculature, they improve hemodynamics as well as exercise tolerance. Attenuation of nitrate action that occurs with chronic therapy can be minimized by following certain treatment strategies.

Emergency treatment of severe cardiogenic pulmonary edema with intravenous isosorbide-5-mononitrate

Intravenous isosorbide-5-mononitrate (IS-5-MN) was administered to 24 patients, mean age 73, with severe respiratory distress after pulmonary edema and acute left heart failure. The condition was due to ischemic cardiopathy in 18 patients (4 with acute myocardial infarctions), congestive cardiomyopathy in 3, hypertensive cardiopathy in 2, and mitral valvular disease in 1. Therapy consisted of an intravenous (i.v.) bolus dose of IS-5-MN, followed by a continuous infusion (mean 8 mg/hour over 24 hours) of i.v. furosemide and additional oxygen. Clinical data were recorded as well as blood gas values and repeated chest radiographs. All patients survived and improved markedly; only 6 needed mechanical ventilation. Most patients had fast respiratory relief, with no untoward reaction, except a brief decrease of blood pressure in a ventilated patient taking morphine. These data indicate that i.v. IS-5-MN is effective and safe for the management of severe acute cardiogenic pulmonary edema.

Role of nitrates in congestive heart failure

The systemic vasoconstriction that is characteristic of patients with congestive heart failure involves arteriolar constriction, reduction in arterial compliance and reduction in venous capacitance, all of which contribute to the increased impedance and increased preload that aggravate the hemodynamic abnormality. Nitrates are effective in increasing arterial compliance and venous capacitance and thus have a favorable acute hemodynamic effect in heart failure. Long-term studies suggest that this favorable effect is maintained in response to high dose oral isosorbide dinitrate therapy and that it is associated with relief of symptoms and improved exercise tolerance. When combined with hydralazine, isosorbide dinitrate therapy has been shown in the Veterans Administration study to prolong survival in patients with class II and III congestive heart failure. Therefore, long-term nitrate therapy appears to have an important potential in patients with heart failure. It may now be appropriate to use nitrates not only to relieve symptoms, but also to improve long-term outlook in this syndrome.

Comparison of transdermal nitrate and isosorbide dinitrate in chronic stable angina

The effects of transdermal nitrate (TN) (Transiderm-Nitro TTS, Geigy Pharmaceuticals, one 10 cm2 patch daily) and oral isosorbide dinitrate (ISDN) (Sorbitrate, Stuart Pharmaceuticals, 10 mg three times daily) were compared in a group of 20 patients with chronic stable angina pectoris. Treadmill exercise duration was prolonged from a median time of 365 s to 428 s after ISDN (P less than 0.05), but was unchanged after TN. The difference between the active treatments was not significant. Weekly consumption of glyceryl trinitrate (GTN) increased during treatment with TN from a median value of 5.5 to 6.3 (P less than 0.05). A decrease was observed after ISDN (7.8 to 3.9, P = NS), and the difference between the drugs was significant (P less than 0.01). Systolic arterial pressure was significantly lower during the ISDN than during the TN treatment period in both the supine (135 +/- 5 vs 128 +/- 5 mm Hg; P less than 0.05) and standing positions (134 +/- 5 vs 122 +/- 5 mm Hg; P less than 0.05). No change in weekly attack rate, the degree of ST depression at angina on treadmill testing, or the number of episodes of ST depression recorded during a 24 h period by Holter monitoring was observed after either drug. In this study, an antianginal effect was demonstrated for ISDN but not for TN. It is suggested that the dose of TN may have been inadequate to demonstrate such an effect, and further studies using a higher dose schedule will be required.

The effect of intranasally administered nitroglycerin on the blood pressure response to laryngoscopy and intubation in patients undergoing coronary artery by-pass surgery

The effect of intranasally administered nitroglycerin (NTG) on the cardiovascular response to laryngoscopy and intubation was studied. Thirty patients scheduled to undergo coronary artery by-pass surgery under thiopentone, enflurane and pancuronium anaesthesia were randomly divided into three groups. Group I received lignocaine 1.5 mg/kg i.v. prior to laryngoscopy and intubation (control group). Group II received lignocaine 1.5 mg/kg i.v. and in addition 2 mg nitroglycerin (NTG) was given intranasally. Group III received only 2 mg NTG intranasally. In Group I laryngoscopy and intubation caused a significant increase in mean arterial pressure (MAP) (P less than 0.01), heart rate (HR) (P less than 0.01) and rate pressure product (RPP) (P less than 0.01) compared to preoxygenation values. In Group II and III MAP and RPP remained unchanged, whereas HR increased (P less than 0.01 and P less than 0.01 respectively). It can be concluded that intranasally administered NTG effectively attenuates the pressor response to laryngoscopy and intubation in patients presenting for coronary artery by-pass surgery and that it is more effective and convenient method than intravenous lignocaine.

Selection of optimal drug therapy for the patient with angina pectoris

The development of new drugs, especially beta-blocking and calcium entry-blocking agents, has greatly facilitated the medical treatment of angina pectoris. The specific needs of each patient should dictate the appropriate treatment of angina pectoris. Angina may occur in patients who have various concomitant disorders such as hypertension, diabetes mellitus, peripheral vascular disease, chronic obstructive pulmonary disease, or arrhythmias, and the physician must take these factors into account when a drug regimen is prescribed. Individual drugs should be chosen on the basis of specifically desired pharmacologic effects, and the dosages should be gradually adjusted according to the patient's response. Although a therapeutic regimen should be selected primarily on the basis of efficacy, the physician must also attempt to recommend a simple and cost-effective program.

Beneficial effects of high-dose diltiazem in patients with persistent effort angina on beta-blockers and nitrates: a randomized, double-blind, placebo-controlled cross-over study

The effects of orally administered diltiazem combined with maximally tolerated doses of beta-blockers and nitrates were assessed in 12 patients, who during stress testing exhibited persistent effort angina and continued objective evidence for inducible myocardial ischemia. Patients performed multistage semisupine exercise on a bicycle ergometer during equilibrium-gated radionuclide angiography after consecutive 2 week treatment periods of placebo or diltiazem 90 mg qid (mean dose 340 mg/day) combined with maximally tolerated propranolol (mean dose 178 mg/day) and isosorbide dinitrate (mean dose 137 mg/day). All medications (including diltiazem or placebo) were administered four times daily for the duration of the study. Diltiazem or placebo was administered according to a double-blind design, with randomized cross-over at the end of each 2 week treatment period. The average number of angina attacks decreased during the double-blind cross-over phase of the trial (7 +/- 7 episodes/week at baseline vs 4 +/- 3 on placebo vs 2 +/- 2 on diltiazem; p = .08). Angina pectoris was abolished during peak exercise in eight of 12 patients on diltiazem (p less than .05 vs placebo). Diltiazem increased total exercise duration from 276 +/- 92 to 310 +/- 78 sec (p less than .005 vs baseline). Diltiazem likewise increased the time to onset of angina from 231 +/- 84 sec at baseline to 305 +/- 77 sec (p less than .005), as well as the time to the onset of 1 mm ischemic ST segment depression (p = .01). Diltiazem decreased heart rate at rest, during submaximal workload, and at peak exercise (p less than .05), and decreased systolic blood pressure at peak exercise only (p less than .05). A significant decline in rate-pressure product at submaximal and peak exercise was noted (p less than .05). At any given workload there was significantly less ST segment depression during submaximal (p = .05) and peak exercise (p less than .025).(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of congestive heart failure by altering loading conditions of the heart

We have not emphasized the traditional approaches to the treatment of congestive heart failure, because there is abundant literature detailing the importance of rest and comfort for the patient, reduction of solute load, and administration of digitalis and diuretics. Instead, we have sought to emphasize the therapeutic interventions that are aimed at changing the mechanical loading conditions of the heart. Treatment expectations must be viewed within an age- or maturity-dependent framework. Thus, when a preterm or full-term newborn infant requires cardiocirculatory support, diminished cardiac reserve limits the benefits derived from diverse treatment methods. This unique fragility of the developing heart and circulation places a premium on the astute manipulation of all of the factors that determine optimum cardiovascular adaptation to stress. Beyond infancy, although cardiovascular reserve increases, it remains imperative to modify therapy by using cardioactive drugs that deal specifically with the separate mechanical and contractile variables to assure optimum survival.

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.

Does alcohol intensify the hemodynamic effects of nitroglycerin?

To evaluate the combined effects of alcohol and nitroglycerin on cardiovascular hemodynamics, M-mode echocardiography and sphygmomanometric blood pressure measurements were performed on two groups of normal subjects, before and after the administration of nitroglycerin, both in the sober state and during alcohol intoxication. In the first part of the study, 0.5 mg of nitroglycerin was given sublingually to 10 healthy volunteers 5-10 minutes after they had ingested 1 g/kg body weight of ethanol within a 30-minute period. Control experiments substituted juice for ethanol. The combined effects of ethanol and nitroglycerin on left ventricular diameters, systolic blood pressure, and wall stress were not significantly different from those of juice and nitroglycerin; heart rate and diastolic blood pressure were increased more (p less than 0.01) by ethanol and nitroglycerin. In the second part of the study, 1.0 mg of nitroglycerin was administered to a second group of 10 healthy volunteers, first in the control state and again 60 minutes after the subjects had ingested 1 g/kg body weight of ethanol within a 60-minute period. Systolic blood pressure and wall stress were significantly lower (p less than 0.01) after ethanol and nitroglycerin than after nitroglycerin before ethanol intake. We conclude that the nitroglycerin-induced reductions in left ventricular preload and afterload are not increased by alcohol during the very early phase of intoxication. However, 1 hour or more after alcohol ingestion nitroglycerin may decrease left ventricular afterload to a level significantly lower than that seen after nitroglycerin in the sober state.(ABSTRACT TRUNCATED AT 250 WORDS)

Rational medical therapy for stable angina pectoris

Important advances in understanding of the pathophysiology and medical treatment of angina pectoris have taken place in the past few years. Angina may occur from increased oxygen demands that cannot be met by a diseased coronary circulation and/or primary decrease in oxygen supply to the heart. Three major categories of pharmacologic agents are used in treating angina. Nitrates remain the first-line approach; they are inexpensive and available in many delivery forms. Beta blockers are also effective in the treatment of angina pectoris, and despite their side effects, are particularly useful in effort angina. The newest agents, the calcium channel blockers, are efficacious in all types of anginal syndromes. Each group of drugs acts differently on the various pathophysiologic mechanisms that contribute to the production of angina. This commentary critically reviews the major groups of anti-anginal drugs and places them in a clinical perspective. Guidelines for choosing an appropriate agent for the treatment of angina are proposed. Special situations, such as angina and hypertension, congestive heart failure, or post-myocardial infarction angina, are discussed with respect to selection of anti-anginal therapy. The proper utilization of nitrates, calcium channel blockers, and beta blockers, alone or in combination, provides a bright future for patients with ischemic heart disease.

A new oral slow release form of isosorbide dinitrate. Effect on the hemodynamics and exercise capacity of patients with angina

To assess the bioavailability of a new oral and slow release form of isosorbide dinitrate (ISDN-SR), we evaluated 12 patients with confirmed coronary artery disease, chronic stable angina pectoris and abnormal maximal exercise tests (angina-limited and associated with greater than or equal to 0.1 mV ST displacement). Each patient was known to have an increased exercise time after 0.4 mg of sublingual nitroglycerin. Patient responses to exercise on the treadmill at two, four, six, and eight hours after the double-blind administration of 40 mg of ISDN-SR were compared to an identical placebo. It is concluded that 40 mg of this slow release form of isosorbide dinitrate is bioavailable for at least eight hours as demonstrated by significantly improved exercise capacity of the majority (64 percent) of angina patients in this study, each of whom demonstrated anginal limitation to exercise and favorable responses to 0.4 mg of sublingual nitroglycerin.

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.

Erythrityl tetranitrate compared with isosorbide dinitrate. Effects on systolic time intervals and nitrate modification of effects of food

The pharmacologic effects of erythrityl tetranitrate (ETN) and isosorbide dinitrate (ISDN) were compared to placebo using systolic time intervals (STI) in a randomized, double-blind study in 15 fasted male volunteers. Sublingual doses of ETN 5 mg, ISDN 5 mg, and placebo were administered to each volunteer at weekly intervals, and measurements of heart rate and STI [pre-ejection period (PEP), left ventricular ejection time (LVET), and PEP/LVET ratio] were made serially for up to 6 hours after each dose. STI were determined using ear densitography. Evaluation of the pharmacologic effects of ETN and ISDN were based on placebo-corrected changes from baseline values. Ejection time index (ETI) [LVET corrected for heart rate] was shortened, but the changes were not statistically significant for either drug. However, after ETN and ISDN, statistically significant (p less than 0.05) changes in PEP and PEP/LVET ratio were demonstrated for up to 240 minutes after dosing. Unexpected marked changes in the baseline corrected PEP/LVET ratio were observed following food at 4 hours after dosing. This suggests increased inotropy during the postprandial period.

Intravenous nitroglycerin for the treatment of angina at rest unresponsive to standard nitrate therapy

Thirty-five patients who had angina at rest that was unresponsive to standard therapy comprised of oral or topical nitrates and beta-blocking drugs were treated with a continuous infusion of intravenous nitroglycerin (IVNTG). The infusion was started at 10 micrograms/min and increased by 10 micrograms/min increments every 5 minutes until an infusion rate of 50 micrograms/min was reached. After each episode of rest angina, the infusion was increased by 50 micrograms/min in the same stepwise manner. Data from a 24-hour baseline control period were compared with those from a 24-hour IVNTG endpoint period at which time the highest IVNTG infusion rate was administered. The average IVNTG infusion rate was 140 +/- 15 micrograms/min. With IVNTG therapy, the number of episodes of angina at rest decreased from 3.5 +/- 0.4 to 0.3 +/- 0.1, sublingual nitroglycerin use decreased from 1.9 +/- 0.3 to 0.4 +/- 0.1 mg/day, and morphine sulfate administration decreased from 5.5 +/- 1.3 to 0.4 +/- 0.2 mg/day (all p less than 0.001). When each patient's response on the endpoint day was analyzed, 25 were defined as complete (no rest angina), 8 as partial (greater than 50% decrease in the number of episodes/day from control values), and 2 as nonresponders. No significant drug-induced adverse effects occurred. IVNTG appears to be effective therapy for angina at rest refractory to standard oral and topical medications.