Effects of nitrate therapy on ventricular remodeling and function

Acute ischemic syndromes. Adjunctive therapy

The acute coronary syndromes (ACS) represent a heterogeneous group of patients along a continuum of risk from unstable angina to non-ST-segment elevation myocardial infarction. ACS is a term that has been used to describe the constellation of clinical symptoms that represent acute myocardial ischemia. This article reviews the adjunctive medications that are used during emergency cardiovasculare care for the early management of patients experiencing the ACS. The adjunctive therapies are divided into early immediate treatment and then subsequent management in the acute care setting.

Efficacy of pretreatment with the angiotensin II type 1 receptor blocker UP269-6 and losartan in the dog: effect on hemodynamics and ischemia-reperfusion

BACKGROUND

Whether pretreatment with the novel oral angiotensin II (AngII) type 1 receptor (AT(1)R) antagonist UP269-6 (UP) can produce more effective AT(1)R blockade than losartan (LN) for cardioprotection during ischemia-reperfusion (IR) in the dog has not been determined.

METHODS AND MATERIALS

We compared the effect of UP (n = 5) and LN (n = 5) on serial in vivo hemodynamics, AngII pressor responses, and left ventricular (LV) volumes and function (echocardiograms) during escalation to optimal oral dosage over 7 days (day 0 to day 6), and acute IR (15 minutes ischemia, 30 minutes reperfusion) and ex vivo AT(1)R protein (Western immunoblots) with additional sham (n = 5) and IR (n = 5) controls on day 6. Compared with LN, UP produced greater vasodepression and decrease in diastolic volume during dose escalation and greater inhibition of the AngII pressor response over the range of escalating concentrations (0.05, 0.10, 0.25, and 0.50 microg/kg) on day 6. Acute IR after UP pretreatment resulted in less increase in LV filling pressure and LV diastolic and systolic volumes and greater ejection fraction, although UP and LN had similar effects on AT(1)R protein.

CONCLUSION

Pretreatment with UP269-6 over 7 days produces more effective pharmacological AT(1)R blockade and cardioprotection after acute IR than LN in the dog.

Role of nitrates for the therapy of coronary artery disease patients in the years beyond 2000

Vasodilator therapy with nitrates has been used for almost a century to bring relief to patients suffering from angina. The acute anti-ischemic effects of nitro-vasodilators for the treatment and prevention of anginal attacks is unquestioned. In addition, nitrates are administered in order to reduce symptomatic and silent ischemic episodes, in patients with proven coronary heart disease who exert ST segment alterations on Holter monitoring. The reduction in total ischemic burden may result in an improved prognosis with regard to infarct prevention and possible prevention of deterioration of left ventricular function due to repetitive episodes of myocardial ischemia. In patients with unstable angina, administration of nitrates significantly diminishes ischemic episodes and reduces the number of clinically symptomatic anginal attacks. The prevention of left ventricular dilatation in patients within the first few days and months following acute myocardial infarction may be due to the reduced preload. In patients with heart failure, preload reduction with nitrates and afterload reduction with hydralazine was tested versus angiotensin converting enzyme (ACE) inhibitors. However, unfortunately, very few data are available concerning the combination therapy of ACE inhibitors and nitrates in heart failure and following acute myocardial infarction. Long-term continuous administration of high doses of nitrates may cause nitrate tolerance, thus reducing the vasodilator potency of these drugs. Since nitrates were introduced into medical therapy many decades before randomized controlled trials were performed, and evidence-based medicine became the basic principal for medical therapy, there are still indications and situations where the full therapeutic potential of nitrates is not being fully appreciated. During recent decades, other anti-ischemic drugs, i.e., beta-receptor agonists and calcium channel blockers, were introduced into the clinical setting and contributed to an optimized therapy for patients with coronary heart disease. Nevertheless, due to their proven and unsurmounted symptomatic efficacy, nitrates will remain one of the cornerstones of acute and long-term therapy of patients with coronary heart disease far beyond the year 2000.

Echocardiography to understand remodeling and to assess prognosis after acute myocardial infarction

Ventricular remodeling indicates a dynamic process, starting with and after acute myocardial infarction, as a result of structural and functional modifications which involve acutely and chronically both the infarcted and noninfarcted zones of the left ventricle. The most effective way to prevent or minimize post-MI cardiac remodeling is to limit the extent of the initial insult. This can be partly achieved by early myocardial reperfusion obtained by different strategies including thrombolysis. In 6405 patients of the GISSI-3 trial, 2D echocardiographic studies were available at predischarge, at 6 weeks and at 6 months after the infarction. The increase in left ventricular volumes over time was reduced by 6-week lisinopril treatment. Patients randomized to lisinopril had smaller volume also at 6 months, after withdrawal of treatment at 6 weeks. Important prognostic indications can also be derived from predischarge echocardiography, since larger quartiles of left ventricular volumes and lower quartile of ejection fraction indicates higher risk of mortality and non-fatal congestive heart failure in the 6 months after the index event, even in the relatively low risk general population of infarcts of the GISSI-3.

Plasma brain natriuretic peptide is a biochemical marker for the prediction of progressive ventricular remodeling after acute myocardial infarction

To investigate the relation between plasma brain natriuretic peptide (BNP) and progressive ventricular remodeling, we measured plasma BNP and atrial natriuretic peptide (ANP) in 30 patients with acute myocardial infarction on days 2, 7, 14, and 30 after the onset. Left ventricular end-diastolic volume index (EDVI), end-systolic volume index (ESVI), and ejection fraction (EF) on admission and 1 month after the onset were assessed by left ventriculography. Changes in EDVI (deltaEDVI), ESVI (deltaESVI), and EF (deltaEF) were obtained by subtracting respective acute-phase values from corresponding chronic-phase values. Plasma ANP on days 2 and 7 showed only weak correlations with deltaEDVI (r = 0.48 and 0.54; both p < 0.01), whereas plasma BNP on day 7 more closely correlated with deltaEDVI (r = 0.77; p < 0.001). When study patients were divided into two groups according to plasma BNP on day 7, the group with BNP higher than 100 pg/ml showed greater increases in left ventricular volume and less improvement in EF compared with the other group with BNP lower than 100 pg/ml (deltaEDVI = 10.4 +/- 8 vs -3.4 +/- 9 ml/m2, deltaESVI = 6.2 +/- 7 vs -4.9 +/- 5 ml/m2, and deltaEF = 1.0% +/- 4% vs 4.9% +/- 5%; p < 0.05, respectively). Multiple regression analysis revealed that only plasma BNP on day 7, but not ANP, peak creatine phosphokinase level, left ventricular end-diastolic pressure, or acute-phase EF, correlated independently with deltaEDVI (p < 0.01). These results suggest that plasma BNP may be a simple and useful biochemical marker for the prediction of progressive ventricular remodeling within the first 30 days of 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.

Effect of nitrates on myocardial remodeling after acute myocardial infarction

Nitrates are effective for the therapy of acute coronary syndromes, including acute myocardial infarction. Their application in acute infarction has established that vasodilators are beneficial provided hypotension is avoided. Nitrates limit early ventricular remodeling in infarction. New dosing strategies and formulations that permit chronic use after infarction with less tolerance might limit late remodeling. Over the last decade, the demonstrated effectiveness of angiotensin-converting enzyme (ACE) inhibitors in limiting ventricular dilation postinfarction has generated controversy over the usefulness of nitrates for that indication. The uncertainty has been intensified by 2 large mortality trials that tested both agents as adjuncts to conventional therapy. These trials were not designed to test whether nitrates might limit remodeling. Mechanistic experimental and clinical studies that tested whether nitrates or ACE inhibitors could effectively limit ventricular remodeling showed that both improved remodeling endpoints. However, experimental studies raise some concern about the decrease in infarct collagen associated with ACE inhibition and emphasize the fact that final outcome represents a balance of effects. That nitrates do not decrease infarct collagen could be important. Nitrate-induced early recruitment of ventricular function after late reperfusion of acute infarction might also be important. In the mortality trials, >50% of patients received open-label nitrates as per indication. Thus, the trial results to date do not suggest that nitrates are ineffective for remodeling, but rather that ACE inhibitors can confer added benefit. There has been no large clinical trial to test the efficacy of nitrates for remodeling as there has been for ACE inhibitors.