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The beta-receptor, atheroma and cardiovascular damage
1ICI Chemical Industries plc, Pharmaceuticals, Division, Macclesfield, Cheshire, U.K.
Insights
Beta-blockers offer cardiovascular protection by reducing myocardial damage in hyperadrenergic states and limiting atheroma formation. They benefit various conditions, including angina and hypertension, reducing risks of heart attack and stroke.
Area of Science:
- Cardiology
- Pharmacology
- Cardiovascular Medicine
Background:
- Hyperadrenergic states are closely linked to myocardial ischemia, necrosis, infarction, and sudden cardiac death.
- Persistent high catecholamine levels may promote atheroma formation through increased vascular permeability and abnormal blood flow.
- Beta-blockers are hypothesized to provide cardiovascular protection due to their effects on catecholamine activity.
Purpose of the Study:
- To review the cardiovascular protective effects of beta-blockers.
- To explore the mechanisms by which beta-blockers may prevent atheroma formation and reduce cardiovascular events.
- To summarize the benefits of beta-blockers in various cardiovascular conditions.
Main Methods:
- Review of existing literature on beta-blockers, hyperadrenergic states, and cardiovascular disease.
- Analysis of animal data regarding beta-blockers and atheromatous plaque formation.
- Synthesis of clinical trial data on beta-blocker efficacy in hypertension, angina, and myocardial infarction.
Main Results:
- Animal studies suggest beta-blockers retard atheroma formation, potentially via reduced heart rate, calcium influx, and lipoprotein permeability.
- Beta-blockers benefit conditions like silent ischemia, unstable angina, and stress-induced myocardial necrosis.
- Clinical data show reduced coronary deaths and myocardial infarctions in hypertensive patients treated with beta-blockers, with varying effects based on drug selectivity and patient characteristics.
Conclusions:
- Acute beta-blockade limits cardiovascular damage in hyperadrenergic states, including myocardial infarction.
- Chronic beta-blockade inhibits atheroma formation in animals and beneficially influences the incidence of stroke and myocardial infarction in humans.
- Beta-blockers are valuable in managing a spectrum of cardiovascular conditions linked to atheroma and myocardial necrosis.
Abstract:
In man a close interrelationship exists between hyperadrenergic states, myocardial ischemia, necrosis, infarction and sudden cardiac death. Persistent high catecholamine levels may also be associated with increased vascular endothelial turnover and permeability to calcium and lipoproteins, increased blood velocity, abnormal blood flow patterns and atheroma formation. There are thus good reasons to predict a cardiovascular protective effect of beta-blockers. Animal data indicate that in spite of apparently adverse plasma lipoprotein changes beta-blockers retard atheromatous plaque formation under conditions of high cholesterol diet with or without stress. A slow heart rate, as well as a reduction in calcium influx and inhibition of both esterification of arterial wall cholesterol (by ACAT) and endothelial permeability to lipoproteins, may be central to this process. Beta-blockers benefit a spectrum of conditions related to the atheromatous process and myocardial necrosis. These are silent ischemia; stable (including mixed), unstable and preinfarction angina; periinfarction events (including myocardial rupture and dissection of the ascending aorta); and myocardial necrosis associated with stress conditions such as head injuries and subarachnoid hemorrhage. In one study coronary deaths in hypertensive men, particularly in smokers, were significantly reduced by metoprolol (a beta 1-selective blocker) compared to a diuretic. In contrast in the MRC study of mild hypertension only nonsmoking men with mild to moderate hypertension who received a nonselective beta-blocker appeared to experience fewer myocardial infarctions. Recent clinical data showed that moderate-severe hypertensives who were optimally controlled by atenolol-based treatment over a 10-year period were less likely to die from myocardial infarction than those suboptimally controlled, irrespective of a rise in serum triglyceride levels. Thus the net effect of acute beta-blockade in hyperadrenergic states, including myocardial infarction, is to limit cardiovascular damage. Chronic beta-blockade inhibits atheroma formation (in animals) and beneficially modifies the incidence of stroke and myocardial infarction, which in man are the long-term consequences of hypertension.