Role of nitrates after acute myocardial infarction

Recent advances on the development of NO-releasing molecules (NORMs) for biomedical applications

Nitric oxide (NO) is an important biological messenger as well as a signaling molecule that participates in a broad range of physiological events and therapeutic applications in biological systems. However, due to its very short half-life in physiological conditions, its therapeutic applications are restricted. Efforts have been made to develop an enormous number of NO-releasing molecules (NORMs) and motifs for NO delivery to the target tissues. These NORMs involve organic nitrate, nitrite, nitro compounds, transition metal nitrosyls, and several nanomaterials. The controlled release of NO from these NORMs to the specific site requires several external stimuli like light, sound, pH, heat, enzyme, etc. Herein, we have provided a comprehensive review of the biochemistry of nitric oxide, recent advancements in NO-releasing materials with the appropriate stimuli of NO release, and their biomedical applications in cancer and other disease control.

New lipophilic organic nitrates: candidates for chronic skin disease therapy

Organic nitrates are widely used, but their chronic efficacy is blunted due to the development of tolerance. The properties of new tolerance free organic nitrates were studied. Their lipophilicity profile and passive diffusion across polydimethylsiloxane membrane and pig ear-skin, and their efficacy in tissue regeneration using HaCaT keratinocytes were evaluated. The permeation results show that these nitrates have a suitable profile for NO topical administration on the skin. Furthermore, the derivatives with higher NO release exerted a pro-healing effect on HaCaT cells. This new class of organic nitrates might be a promising strategy for the chronic treatment of skin pathologies.

Heart Failure Complicating Acute Mtyocardial Infarction

Factors predisposing the older person with acute myocardial infarction (MI) to develop heart failure (HF) include an increased prevalence of MI, multivessel coronary artery disease, decreased left ventricular (LV) contractile reserve, impairment of LV diastolic relaxation, increased hypertension, LV hypertrophy, diabetes mellitus, valvular heart disease, and renal insufficiency. HF associated with acute MI should be treated with a loop diuretic. The use of nitrates, angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, aldosterone antagonists, beta-blockers, digoxin, and positive inotropic drugs; treatment of arrhythmias and mechanical complications; and indications for use of implantable cardioverter-defibrillators and cardiac resynchronization is discussed.

Continuous long-term dosing with oral slow-release isosorbide dinitrate does not reduce incidence of cardiac events in patients with healed myocardial infarction

BACKGROUND

In the short term, isosorbide dinitrate (ISDN) is considered to be therapeutically effective. The long-term effects of treatment with slow-release ISDN are less clear.

HYPOTHESIS

The study was undertaken to investigate the effects of continuous, long-term dosing with oral slow-release ISDN on the incidence of cardiac events in patients with healed myocardial infarction (MI). The study was carried out in accordance with the intention-to-treat principle.

METHODS

In all, 1.102 in- and outpatients, of either gender, with healed MI were randomly divided into groups treated with ISDN (n = 470) and not treated with ISDN (n = 632). Patients in the ISDN group received a continuous regimen of 20 mg of oral, long-acting ISDN three times a day, after meals. The mean observation period was 15.0 +/- 18.5 months. The primary endpoints were nonfatal and fatal recurrent MI, death from congestive heart failure, and sudden death.

RESULTS

There were no significant differences in the baseline characteristics of the patients in the ISDN and no-treatment groups; nevertheless, significantly more patients in the ISDN group experienced cardiac events. In the ISDN group, 35 patients (7.4%) experienced cardiac events during the observation period, versus only 28 patients (4.4%) in the no-treatment group (p < 0.05; odds ratio 1.74; 95% confidence interval 1.04-2.90).

CONCLUSION

Continuous long-term dosing with oral, slow-release ISDN does not reduce and probably increases the incidence of cardiac events among patients with healed MI.

Heart Failure–Complicating Acute Myocardial Infarction

This article addresses issues related to acute myocardial infarction (MI) complicated by heart failure, particularly in elderly patients. Findings have shown that acute MI complicated by congestive heart failure (CHF) is associated with a high mortality, and that women with acute MI are more likely to be older and to develop CHF than men with acute MI. In general, management of CHF complicating acute MI is similar in older and younger patients. Actions discussed include hemodynamic monitoring; the administration of oxygen; and the use of morphine, diuretics, nitroglycerin, angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, spironolactone, beta-blockers, calcium channel blockers, magnesium, digoxin, and positive inotropic drugs. The article also discusses measures for treating arrhythmias and for diagnosing mechanical complications.

Heart-Failure–Complicating Acute Myocardial Infarction

This article addresses issues related to acute myocardial infarction(MI) complicated by heart failure, particularly in elderly patients. Findings have shown that acute MI complicated by congestive heart failure (CHF) is associated with a high mortality, and that women with acute MI are more likely to be older and to develop CHF than men with acute MI. In general, management of CHF-complicating acute MI is similar in older and younger patients. Actions discussed include hemodynamic monitoring; the administration of oxygen; and the use of morphine, diuretics, nitroglycerin,angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, spironolactone, beta-blockers, calcium channel blockers, magnesium, digoxin, and positive inotropic drugs. The article also discusses measures for treating arrhythmias and for diagnosing mechanical complications.

Eccentric Dosing of Nitrates Does Not Increase Cardiac Events in Patients with Healed Myocardial Infarction

This study was performed to investigate the risk of cardiac events by eccentric or continuous dosing of nitrates in patients with healed myocardial infarction. A total of 573 patients with healed myocardial infarction were assigned to one of two groups: a nitrate-treatment (n =239) and a nontreatment (n =334) group. The nitrate-treatment group was further subdivided into a group receiving eccentric dosing of nitrates (n =153) and a group receiving continuous dosing of nitrates (n =86). The mean observation period was 11.2+/-8.2 months. The cardiac events investigated were nonfatal and fatal recurrent myocardial infarction, death from congestive heart failure, sudden death, worsening angina and rebound angina. Baseline characteristics were also compared among the three groups to determine any effects on outcome. Among the patients receiving eccentric or continuous dosing of nitrates, the rates of cardiac events were 12.7/1,000 person.year and 67.4/1,000 person.year, respectively, whereas the rate was 19.7/1,000 person.year in the nontreated patients. The incidence of cardiac events was significantly greater in patients receiving continuous dosing of nitrates than in the nontreated patients (p <0.05). Continuous dosing of nitrates thus increases cardiac events, and while eccentric dosing of nitrates does not increase them, it is also not effective at preventing them in patients with healed myocardial infarction.

Long-term, continuous treatment with both oral and transdermal nitrates increases cardiac events in healed myocardial infarction patients

This study was performed to investigate the effects of continuous dosing of oral, transdermal (patch), and a combination of the two with nitrate treatments on cardiac events in patients with healed myocardial infarction. In total, 1,291 patients with healed myocardial infarction were assigned 2 groups: treatment with nitrates (n=713) or nontreatment (n=578). Nitrate treatment was subdivided into 3 groups: patch group (n=149), oral group (n=504), and combination group (n=60). The mean observation period was 17.4 +/- 21.1 months. Primary end points were nonfatal and fatal recurrent myocardial infarction, death from congestive heart failure, and sudden death. Baseline characteristics were also compared among the 4 groups to determine any effects on outcome. Among the patients with patch, oral, and combination groups, cardiac events occurred 3.4%, 6.7%, 10.0%, respectively, whereas only 2.9% of the patients treated without nitrates had cardiac events. The incidence of cardiac events was significantly greater in patients with oral nitrates and combination groups compared to patients without nitrates (p<0.01, respectively). Continuous dosing of long-term treatment with both oral and transdermal nitrates increased cardiac events in healed myocardial infarction patients.

Heart failure complicating acute myocardial infarction

Older people with congestive heart failure associated with acute myocardial infarction should be treated with loop diuretic therapy. Class I indications for the use of early intravenous beta blockade in patients with acute myocardial infarction are patients without a contraindication to beta blockers who can be treated within 12 hours of onset of myocardial infarction; patients with continuing or recurrent ischemic pain; and patients with tachyarrythmias, such as atrial fibrillation with a rapid ventricular rate. Class I indications for the use of angiotensin-converting enzyme inhibitors during acute myocardial infarction are (1) patients within the first 24 hours of onset of a suspected acute myocardial infarction with ST segment elevation in two or more anterior precordial leads or with clinical heart failure in the absence of significant hypotension or contraindications to the use of angiotensin-converting enzyme inhibitors, (2) patients with myocardial infarction and a left ventricular ejection fraction of less then 40%, (3) and patients with clinical heart failure on the basis of systolic pump dysfunction during and after convalescence from acute myocardial infarction. No class I indications exist for using calcium channel blockers or magnesium during acute myocardial infarction.

Opportunities for the treatment of erectile dysfunction by modulation of the NO axis--alternatives to sildenafil citrate

Erectile function in man depends upon a complex interaction of psychogenic, neurologic, hormonal and vascular factors, and therefore the management of erectile dysfunction (ED) reflects this complexity of control. Therapeutic options include psychological and non-pharmacological approaches as well as drug treatments. The effectiveness of the type-5 cGMP phosphodiesterase inhibitor sildenafil citrate (Viagra) confirms the pivotal role of the NO-cGMP axis in promoting and maintaining erection. Although widely acclaimed, sildenafil leaves many questions unanswered, especially regarding its susceptibility to pharmacokinetic drug interactions, and its safety in patients with ischaemic heart disease and those taking nitrates. In view of the epidemiological link between erectile dysfunction and cardiovascular disease in the elderly, this limitation might have much broader implications. The presently available scientific documentation, although less extensive, indicates that NO donors, such as topically applied nitroglycerin (GTN; for example, 1-2 puffs of an ordinary GTN spray applied to the shaft of the penis), might be a reasonable alternative. Further larger-scale research on the efficacy and tolerability of topical GTN is needed to establish its full therapeutic potential in the treatment of erectile dysfunction.

Long-term nitrate treatment increases cardiac events in patients with healed myocardial infarction. Secondary Prevention Group

BACKGROUND

Nitrates dilate coronary arteries, ameliorate myocardial ischemia, minimize left ventricular remodeling, and reduce mortality in patients with acute myocardial infarction. However, the effects of long-term treatment with nitrates on cardiac events in patients with healed myocardial infarction are not known.

METHODS AND RESULTS

A total of 1,002 patients with healed myocardial infarction (789 male and 213 female) were randomly divided into 2 groups: treatment with nitrates or nontreatment. The mean observation period was 18.0 +/- 19.9 months. Primary end points were nonfatal and fatal recurrent myocardial infarction, death from congestive heart failure, and sudden death. Baseline characteristics of the 2 groups were also compared to determine any effects on outcome. Among the 621 cases treated with nitrates, 41 cases (6.6%) experienced cardiac events during the observation period, whereas only 12 of the 381 cases that were not treated with nitrates (3.1%) had cardiac events. This difference was statistically significant (p < 0.05; odds ratio 2.17; 95% confidence interval 1.13-4.19). There were no differences in the incidence of noncardiac death or being lost to follow-up between the 2 groups. Although the precise mechanism of this increase in the occurrence of cardiac events by long-term treatment with nitrates is not clear, nitrate tolerance with possible rebound and neurohormonal effects may be involved.

CONCLUSION

Long-term treatment with nitrates increased cardiac events in patients with healed myocardial infarction.

Haemodynamic evaluation of two regimens of molsidomine in patients with chronic congestive heart failure

We investigated the extent and duration of the haemodynamic effects of two regimens of molsidomine, i.e. two tablets of a standard regimen consisting of 4 mg given 6 h apart and one tablet of 16 mg in sustained-release form once daily in 13 patients with chronic congestive heart failure using a placebo-controlled, randomized, double-blind and crossover protocol over a period of 12 h. Both regimens significantly affected systolic, mean and diastolic pulmonary arterial pressure (reductions of up to 15%), right atrial pressure (reductions of up to 35%) and total pulmonary resistance (reductions of up to 18%). The lower dose achieved its maximum action after about 1 h and remained effective for 2 h, whereas the higher dose in sustained-release form showed maximal efficacy at 2 h and remained active even at 12 h. In contrast, only minor changes in arterial blood pressure, systemic vascular resistance and cardiac output were observed on both regimens, almost exclusively at 2 h. Heart rate was not affected by either of the regimens tested. Neither regimen led to any untoward adverse effects. Thus, molsidomine is a potent vasodilating agent which, apart from its effects on preload, also acts on pulmonary arterial and right atrial pressures, leaving systemic circulation largely unaffected on the regimens tested. Administered on its own, it is therefore suitable for treatment of congestive heart failure.

Acute myocardial infarction. Then and now

Dramatic changes in the management of acute myocardial infarction (AMI) have occurred in the past decade. While previous management strategies were primarily supportive, current strategies focus on achieving and maintaining patency of the infarct-related artery restoring blood flow to jeopardized myocytes, preserving left ventricular function, and preventing recurrences and complications in addition to promoting healing. Restoration of blood flow can be achieved pharmacologically with thrombolytic agents or mechanically with percutaneous transluminal coronary angioplasty (PTCA). Early use of antiplatelet agents and anticoagulants helps maintain patency of the infarct-related arteries and prevents thromboembolic complications. Administration of beta-blockers and angiotensin enzyme inhibitors are more specific means of conserving myocardium and preserving ventricular function. Additionally, several strategies for preventing arrhythmias such as prophylactic lidocaine use and routine long-term suppression of premature ventricular contractions with antiarrhythmic drugs are no longer routinely advocated. Basically, in the era prior to the eighth decade of this century, the primary direction of the therapeutic strategy for AMI was to reduce the oxygen demands in the infarcted myocardium; whereas in the subsequent years, the emphasis shifts to improvement in oxygen delivery, via thrombolysis, PTCA, and coronary artery bypass graft surgery. These interventional changes, when added to greater sophistication in the use of drugs to reduce oxygen demands, resulted in significant lowering of myocardial mortality.

Concurrent nitroglycerin therapy impairs tissue-type plasminogen activator-induced thrombolysis in patients with acute myocardial infarction

Nitroglycerin given with tissue-type plasminogen activator (t-PA) has been shown to decrease the thrombolytic effect of t-PA in animal models of coronary artery thrombosis. The present study was conducted to determine whether such an interaction between nitroglycerin and t-PA occurs in patients with acute myocardial infarction undergoing thrombolytic treatment. Patients with acute myocardial infarction were treated with t-PA plus saline solution (group 1; n = 11) or t-PA plus nitroglycerin (group 2; n = 36). Stable coronary artery reperfusion assessed by continuous ST-segment monitoring in 2 electrocardiographic leads, and release of creatine kinase occurred in 91% of group 1 patients and in 44% of group 2 patients (95% confidence interval, 14% to 82%; p < 0.02). Plasma levels of t-PA antigen were consistently (p < 0.005) higher in group 1 than in group 2 patients up to 6 hours after t-PA infusion. Conversely, plasminogen activator inhibitor-1 (PAI-1) levels were slightly higher in group 2 than in group 1 patients. These observations indicate that nitroglycerin given with t-PA significantly decreases the plasma t-PA antigen concentrations and impairs the thrombolytic effect of t-PA in patients with acute myocardial infarction.

Nitroglycerin inhibits experimental thrombosis and reocclusion after thrombolysis

Nitroglycerin inhibits platelet aggregation in vitro, but its effect on thrombosis and platelet function in vivo is controversial. This study assessed the effect of nitroglycerin on primary thrombus formation in response to vessel wall injury and secondary thrombus formation, or rethrombosis, after lysis of an existing thrombus. In the first protocol the right carotid artery was instrumented with a flow probe, stenosis, an anodal electrode, and a proximal infusion line. A 300 microA anodal current was used to induce endothelial injury and subsequent thrombotic occlusion of the vessel. Anisoylated plasminogen streptokinase activator complex (APSAC; 0.05 U/kg intraarterially) was injected proximal to the thrombus 30 minutes after occlusion. After APSAC, nitroglycerin (1 microgram/kg/min intraarterially, n = 7) or vehicle (n = 6) was infused proximal to the thrombus for 3 hours. Reocclusion occurred in two of seven nitroglycerin-treated dogs and six of six vehicle-treated dogs (p < 0.05). In the second protocol both carotid arteries were instrumented as described previously. Anodal current (300 microA, 180 minutes) was applied to the right carotid (n = 12) artery to determine control times to occlusion. The left carotid artery served as the test vessel, receiving either nitroglycerin (1 microgram/kg/min intraarterially, n = 6) or trimethaphan (0.05 mg/kg/hr intraarterially, n = 6). Trimethaphan was used to produce controlled hypotension to match the approximately 10% decrease in mean arterial blood pressure that was observed during nitroglycerin infusion. Control arteries and those treated with trimethaphan formed occlusive thrombi in all instances. Nitroglycerin infusion resulted in a lower incidence of occlusion (1 of 6; p < 0.05 vs control value) and inhibited ex vivo platelet aggregation to adenosine diphosphate and arachidonic acid (p < 0.05). Local infusion of nitroglycerin reduced the formation of primary thrombi, independent of the hypotensive effect of the drug, and exerted systemic effects on platelet aggregation. Furthermore, platelet inhibition with nitroglycerin reduced the incidence of secondary thrombus formation (rethrombosis) after thrombolysis. The results suggest that a potential benefit of nitroglycerin therapy may be derived from its ability to inhibit thrombotic events in patients with unstable angina or myocardial infarction.

Effects of nitrate therapy on ventricular remodeling and function

The hypothesis that nitrates might effectively limit left ventricular remodeling and improve function after acute myocardial infarction has been tested in experimental and clinical models, with special attention to the pathophysiologic evolution of remodeling. In 1 clinical study, before the thrombolytic era, the effects of low-dose intravenous nitroglycerin infusion for the first 48 hours during acute myocardial infarction was evaluated in a prospective, randomized, single-blinded, placebo-controlled study of 310 patients (154 nitroglycerin; 156 placebo). Nitroglycerin proved to be safe and produced several benefits compared with placebo: (1) smaller infarct size; (2) less left ventricular dysfunction; (3) less infarct expansion and thinning; (4) better functional status; (5) fewer in-hospital complications such as left ventricular failure, left ventricular thrombus, cardiogenic shock, and infarct extension; and (6) fewer deaths up to 1 year. Two subsequent clinical studies in the thrombolytic era, with low-dose intravenous nitroglycerin infusion during infarction over the first 48 hours followed by buccal nitrate (eccentric dose regimen) or placebo during healing over 6 weeks postinfarction, indicated that prolonged nitrate therapy effectively limited left ventricular remodeling and improved function further compared with placebo.