Early angiotensin converting enzyme inhibitor therapy enhances the benefits of late coronary artery reperfusion on infarct expansion

Prevention of remodeling in congestive heart failure due to myocardial infarction by blockade of the renin–angiotensin system

Ventricular remodeling subsequent to myocardial infarction (MI) is a complex process and is considered to be a major determinant of the clinical course of congestive heart failure (CHF). Emerging evidence suggests that activation of the renin-angiotensin system (RAS) plays an important role in post-MI ventricular remodeling; however, it is becoming clear that this is one of several neurohumoral systems that are activated in CHF. Blockade of RAS by angiotensin-converting enzyme inhibitors or angiotensin II type 1 receptor antagonists attenuates the ventricular dysfunction, but the effects of individual drugs in reducing the morbidity and mortality in CHF patients are variable. Furthermore, there is a difference of opinion as to the time of initiation of therapy with RAS blockers after the onset of MI. Since blockade of RAS partially improves cardiac function, it is suggested that a combination therapy involving RAS blockers (angiotensin-converting enzyme inhibitors or angiotensin II type 1 receptor antagonists) and agents that affect other neurohumoral systems may prove useful for improved treatment of CHF. Although activation of RAS has been shown to promote oxidative stress in experimental studies, the use of antioxidant therapy in CHF patients is controversial. Recent experimental studies have shown that ventricular remodeling in CHF is associated with remodeling of subcellular organelles such as sarcolemma, sarcoplasmic reticulum, myofibrils and extracellular matrix in terms of their molecular structure and composition. Since attenuation of remodeling in one and/or more subcellular organelles by different agents may prevent the progression of CHF, it is a challenge to develop specific drugs affecting molecular mechanisms associated with subcellular remodeling for the improved therapy of CHF.

Captopril and its time of administration in myocardial ischaemic-reperfusion injury

The present study was designed to investigate the role of captopril in an in vivo model of myocardial ischaemic-reperfusion injury with respect to its time of administration. In open-chest pentobarbitone anaesthetized cats, the left anterior descending coronary artery was occluded for 15 min followed by 60 min of reperfusion. Vehicle (saline) or captopril (4 mg kg(-1)) was administered 10 min before instituting ischaemia (pre-treatment) or 5 min before reperfusion (post-treatment). In the vehicle-treated group, ischaemic-reperfusion injury (IRI) was evidenced by enhanced plasma renin activity, depression of global haemodynamic function (mean arterial pressure, left ventricular-end-diastolic-pressure, peak positive and negative dP/dt) along with depletion of myocardial high energy phosphate (HEP) compounds. Oxidant stress in IRI was evidenced by raised levels of myocardial thiobarbituric acid reactive substances (TBARS) and depletion of endogenous myocardial antioxidants (glutathione, superoxide dismutase and catalase). Pre-treatment with captopril prevented (i) loss of myocardial haemodynamic function, (ii) rise in TBARS and (iii) depletion of myocardial HEP compounds. However, in the post-treatment group, only partial recovery of myocardial haemodynamic function, with no significant reduction in TBARS, was observed. Glutathione, superoxide dismutase and catalase were unaffected by either treatment schedules. The results of the present study suggest that captopril is more effective in attenuating ischaemic-reperfusion injury when administered before ischaemia rather than before reperfusion.