Early versus delayed angiotensin-converting enzyme inhibition in experimental chronic heart failure. Effects on survival, hemodynamics, and cardiovascular remodeling

BACKGROUND

The efficacy of ACE inhibitors in congestive heart failure (CHF) might be affected by the pathophysiological status present at the onset of treatment. We compared in a rat model the effects of ACE inhibition (lisinopril, 10 mg.kg-1.d-1) initiated early (1 week) or late (3 months) after myocardial infarction (i.e., at time points corresponding to moderate or severe CHF without or with established cardiac remodeling).

METHODS AND RESULTS

Survival was improved by early treatment at 3 months (from 76% to 95%) and by both early and delayed treatment at 9 months (placebo, 28%; early, 90%; delayed, 61%). Delayed treatment was initiated in a more severe pathophysiological context of CHF than early treatment, illustrated in untreated rats by higher left ventricular (LV) end-diastolic and central venous pressures and by increased LV weight and LV cavity circumference. After 9 months, early and delayed treatments reduced systolic, LV end-diastolic, and central venous pressures. Both treatments also similarly decreased LV weight, LV cavity circumference, and LV collagen density.

CONCLUSIONS

In this rat model of CHF, early and delayed ACE inhibitor treatments both increase survival and exert similar beneficial effects on cardiac hemodynamics and remodeling. Although early treatment prevents the development of ventricular dysfunction and remodeling, delayed treatment is capable of reversing cardiac hypertrophy and remodeling, as well as ventricular dysfunction. Thus, ACE inhibitors exert marked beneficial effects even when treatment is initiated late into the evolution of heart failure (ie, at a time of established ventricular dysfunction and remodeling).

Response of large and small vessels to alpha and beta adrenoceptor stimulation in heart failure: effect of angiotensin converting enzyme inhibition

The increased sympathetic drive in chronic heart failure (CHF) might provoke vascular adrenoceptor desensitization, which, together with endothelial dysfunction, could contribute to the altered vasomotor tone seen in CHF. We investigated 1) whether CHF alters the responses mediated by alpha and beta adrenoceptors in small and large peripheral arteries, and 2) the effect of angiotensin-converting enzyme (ACE) inhibition. Rats with CHF (coronary artery ligation) were treated with placebo or the ACE inhibitor lisinopril (10 mg/kg/d) starting 7 days after ligation. Responses to phenylephrine (alpha 1 agonist), salbutamol (beta 2 agonist) as well as acetylcholine (endothelium-dependent), were assessed after 3 months in isolated and pressurized segments of the abdominal aorta, the femoral and the mesenteric arteries. In animals with hemodynamic signs of CHF, neither the vasoconstrictor responses to phenylephrine nor the vasodilator response to salbutamol were affected. In contrast, the dilator response to acetylcholine of both small arteries, but not that of the aorta, was impaired. Furthermore, CHF did not modify vessel structure. While lisinopril did not modify the responses to adrenergic agonists, it normalized the response to acetylcholine. Furthermore, ACE inhibition reduced vascular media cross sectional area and collagen density. Thus, the unchanged arterial responsiveness to adrenoceptor agonists does not indicate any vascular adrenoceptor desensitization, while endothelial dependent vasodilation of small arteries is impaired in CHF. ACE inhibition does not modify the response to adrenergic stimuli, prevents endothelial dysfunction and induces both cardiac and vascular remodeling, which probably contribute to the effect ACE inhibitors have on exercise tolerance and survival.

[Combination therapy in cardiovascular diseases other than hypertension]

As in hypertension, the addition of a second active drug is believed to enhance treatment efficacy; however, the extent to which a combination of two low-dose drugs outperforms conventional monotherapy remains uncertain. Established treatments of angina comprises nitrates compounds, beta-blockers and calcium antagonists, which are often given in combination. Beta-blockers are major players in this field as they inhibit the tachycardia induced by nitrates and calcium antagonists; there is therefore a pathophysiological justification for their use in combination therapy, supported by repeated confirmation of positive clinical effect. The most widely chosen calcium antagonists are dihydropyridines; verapamil may impair conduction. However, it is not clear whether combination enhances the effects of the individual antianginal substances. Diuretics are for most clinicians the keystone treatment of heart failure; diuretics are often combined with other drugs, e.g. amiloride and spironolactone. The latter also have a beneficial effect on myocardial structure (myocardium/collagen ratio). ACE-inhibitors are of proven clinical efficacy, and, in addition, have a beneficial effect on survival. They combine well with diuretics: because the diuretic stimulates renin release, the ACE-inhibitor can be given at a lower dose (enhancement of effect). There are, however, certain drawbacks (hypotension, hyperkalemia with antialdosterones). The results of combining ACE-inhibitors with calcium antagonists and beta-blockers await investigation. The ISIS studies demonstrated the advantages of combining beta-blockers, thrombolysis and aspirin in acute infarction. ACE-inhibitors have recently been added to the regimen with a positive effect (extended survival), especially in the presence of a decreased ejection fraction (SAVE, AIRE, GISSI 3 and ISIS 4 studies).(ABSTRACT TRUNCATED AT 250 WORDS)

[The ATLAS study (Assessment of Treatment with Lisinopril and Survival); justification and objectives]

Treatment with ACE inhibitors has improved the prognosis of cardiac failure (CF). The results of CONSENSUS I, SOLVD and V HEFT II show clinical improvement and longer survival with this therapeutic class of drugs. However, the search for the optimal dosage was not undertaken in these trials (a standard dose was fixed at the onset, average dose of enalapril from 15 to 20 mg/day). In clinical practice, patients are prescribed lower doses of ACE inhibitors (enalapril: 7.5 mg/day) than the averages used in large scale trials. In order to optimise the use of ACE inhibitors, the ATLAS study (Assessment of Treatment with Lisinopril and Survival) was undertaken with the precise objective of comparing two dosages (2.5 to 5 mg/day vs 32.5 to 35 mg/day) of lisinopril on the morbidity and mortality of patients with CF. This international, multicenter, randomised, double-blind parallel group trial aims to include 3,000 patients over 18 years of age with NYHA Classes II, III and IV, and an ejection fraction < or = 30% and to follow them up for 3 to 4.5 years. Nearly 30 French centres will participate in this trial. After an initial, open period of evaluation of tolerance (5 mg to 15 mg/day of lisinopril in France), the patients will be randomised to two groups. After randomisation, all patients will receive 5 mg per day of lisinopril. The "high dose" group will receive 20 mg/day for two weeks, then 30 mg/day in addition to the "open dosage". In cases of intolerance, the dosage may be reduced to 20 mg/day or 10 mg/day, or the drug may be withdrawn.(ABSTRACT TRUNCATED AT 250 WORDS)