Relationship between decrease in afterload and beneficial effects of ACE inhibitors in experimental cardiac hypertrophy and congestive heart failure

Abstract

The beneficial effect of angiotensin-converting enzyme (ACE) inhibitors on myocardial mass and contractility in hypertension and, possibly, congestive heart failure (CHF) may be related to their ability to induce a decreased afterload. This has been assessed in four experimental models--renovascular hypertension, DOCA-salt hypertension, spontaneously hypertensive rats (SHR) and myocardial infarction (MI)--and in normotensive mature rats. In renovascular hypertension, ACE inhibitors normalized blood pressure as well as left ventricular hypertrophy and hypocontractility. In the DOCA-salt model, blockade of the renin-angiotensin system by ACE inhibitors did not decrease blood pressure and therefore had no effect on cardiac mass and contractility. In the SHR model, the arterial smooth muscle cell is functionally and structurally abnormal; as a result, cardiac overload led, over time, to a terminal, decompensated phase of CHF. ACE inhibitors, by decreasing blood pressure, reversed cardiac hypertrophy, hyperfibrosis and atrial natriuretic factor (ANF) oversecretion and prevented overload and time-induced CHF. In the MI model, ACE inhibitors decreased blood pressure and thereby decreased overload and reversed cardiac hypertrophy, hypocontractility, hyperfibrosis and ANF oversecretion. In normal ageing, heart function and structure are modified over time. ACE inhibitors, by blocking a 'normal' signal upstream, allowed a 'normal' effector system to decrease blood pressure and prevented the development of age-dependent cardiac hypertrophy.