Sudden cardiac death and the potential role of beta-adrenoceptor-blocking drugs

Serum lipid physiology and the influence of glaucoma medications

Understanding the effect of serum lipid levels on risk factors for coronary heart disease and how they are influenced by medical therapy may lead to overall better care of the glaucoma patient. Elevated low-density lipoprotein and total cholesterol levels are major risk factors for heart disease. In contrast, high-density lipoprotein (HDL) is protective for heart disease. beta-adrenergic blockers, a class of medicines used to treat glaucoma, may influence serum lipid levels. Oral nonselective beta-adrenergic blockers reduce HDL cholesterol by 19% and increase triglycerides by 20-40%. Furthermore, topical nonselective beta-adrenergic blockers also decrease serum HDL and worsen the total cholesterol/HDL ratio. However, beta-blockers with intrinsic sympathomimetic activity appear to be lipid neutral. At present, there is no clear clinical evidence to indicate that changes in serum lipids with use of topical beta-adrenergic blockers significantly affect the clinical course of the patient. Little information is available for other classes of medicines used topically to treat glaucoma. However, oral preparations of prostaglandins, alpha-adrenergic agonists, angiotensin-converting enzyme inhibitors, and calcium channel blockers do not adversely affect serum lipid levels. Further study is required on newer glaucoma preparations to determine their specific actions on lipid levels. Additionally, further work is required to understand the significance of not only the adverse effect of beta-adrenergic blockers on lipid levels, but their overall effect on long-term cardiac morbidity and mortality.

Sudden cardiac death in patients with hypertension. An association with diuretics and beta-blockers?

The cornerstones of current antihypertensive treatment are diuretics and beta-blockers and the efficacy of these drugs in preventing cardiovascular disease is undisputed. This article focuses on the effect of these 2 drug classes on the incidence of sudden death. Numerous studies have shown that thiazide diuretics have a strong, dosage-dependent potassium-depleting effect, and it has been postulated that this may explain why the reduction in risk of coronary heart disease, observed in hypertension trials, was less pronounced than expected. In 7 trials that included sudden death as an end-point; a pooled risk-ratio of sudden death of 1.5 (95% confidence interval 1.1 to 2.0) was observed when non-potassium-sparing diuretics were compared with placebo. Two recent case-control studies have also strongly indicated that the use of thiazides increases the risk of sudden death. Evidence from trials using potassium-sparing diuretic combinations suggests that these may be better tolerated than thiazide monotherapy. Although it was suggested in the 2 recent case-control studies that recipients of beta-blockers are also at an increased risk of sudden death, further studies are required to confirm this finding, particularly since these drugs have several well-documented cardioprotective effects.

Risk factors for sudden cardiac death in middle-aged British men

BACKGROUND

Risk factors specific to sudden cardiac death (SCD), ie, death within 1 hour after onset of symptoms, have been poorly identified, although recent findings from the present study incriminate heavy drinking and elevated heart rate. This paper examines the relations between a wide range of established and potential risk factors for ischemic heart disease (IHD) and SCD to identify independent risk factors for SCD and factors that might particularly or specifically relate to SCD.

METHODS AND RESULTS

We present a prospective study of a cohort that was drawn from general practices in 24 British towns of 7735 middle-aged men who were followed up for 8 years. During 8 years of follow-up, the men experienced 488 major IHD events (nonfatal and fatal), of which 117 (24%) were classified as SCD. Age, preexisting IHD, arrhythmia, systolic blood pressure, blood cholesterol, elevated heart rate (> or = 90 beats per minute), physical activity (all, P < .05), and, to a lesser extent, smoking (P = .06), HDL cholesterol (P < .07), and elevated hematocrit (> or = 46%, P < .09) emerged as independent risk factors for SCD after adjustment for a wide range of factors. Diabetes was not found to be associated with SCD, and forced expiratory volume in 1 second, body mass index, white blood cell count, and antihypertensive drugs were not associated with risk of SCD after adjustment. When examined in relation to non-sudden IHD deaths and nonfatal myocardial infarction, elevated heart rate, heavy drinking, and arrhythmia emerged as factors that appear to be specific or particular to SCD. These three factors and age and blood cholesterol were associated with an increased risk of SCD in men both with and without preexisting IHD. Physical activity, systolic blood pressure, and current smoking were associated with SCD only in men without preexisting IHD. HDL cholesterol and hematocrit were strong predictors of SCD only in men with preexisting IHD.

CONCLUSIONS

Three risk factors appear to be specific or particular to the risk of SCD, and these and other risk factors operate differently in patients with versus those without preexisting IHD. These findings have implications for the causes and prevention of SCD.

Metoprolol: a pharmacoeconomic and quality-of-life evaluation of its use in hypertension, post-myocardial infarction and dilated cardiomyopathy

Metoprolol is a beta 1-selective adrenoceptor antagonist that is widely used in several indications. A recent investigation has also highlighted a potential role for metoprolol in selected patients with idiopathic dilated cardiomyopathy. Pharmacoeconomic and quality-of-life data for metoprolol are limited to the areas of hypertension, post-myocardial infarction and idiopathic dilated cardiomyopathy. In these settings, metoprolol has shown beneficial effects on morbidity and mortality, or closely-related end-points. Controlled release formulations offer the potential to maximise the confirmed antihypertensive benefits of metoprolol by maintaining clinically effective plasma drug concentrations within a narrow range over a 24-hour interval between doses. Recent data support the use of controlled release metoprolol at the low dose of 50 mg/day. Metoprolol is at least as effective as many other antihypertensive drugs, although compared with thiazide diuretics at relatively high doses in the MAPHY (Metoprolol Atherosclerosis Prevention in Hypertensives) trial, metoprolol was associated with a more favourable effect on mortality. Pharmacoeconomic analysis, also based on the MAPHY trial, indicates that metoprolol is more cost effective than high dose thiazide diuretics in middle-aged men with mild to moderate hypertension. However, the advantage for beta-blockade in this trial is not supported by results of other studies, and the applicability of these data to current medical practice using lower thiazide doses is therefore questionable. Quality of life in patients with mild to moderate hypertension did not deteriorate in most investigations with metoprolol. Furthermore, quality of life was similar for controlled release metoprolol and atenolol. With conventional/matrix-based sustained release metoprolol, quality of life was less satisfactory than with lisinopril but was only marginally different from that with diltiazem (at lower than usual therapeutic doses). Nevertheless, these newer agents have no proven beneficial effect on mortality, and further studies are also warranted with controlled release metoprolol 50 mg/day. When administered post-myocardial infarction, conventional metoprolol was associated with significant improvements in quality of life and was cost saving over a 3-year period. Significant improvements in quality of life were also evident for metoprolol-treated patients with idiopathic dilated cardiomyopathy. In summary, available data support the continued extensive usage of metoprolol as treatment for hypertension and as therapy post-myocardial infarction. Pharmacoeconomic data supporting an advantage for metoprolol over high dose thiazides in hypertension needs further assessment in settings reflecting usual general practice approaches to managing patients with hypertension, while differences in quality of life between metoprolol and other antihypertensive agents appear to be marginal.(ABSTRACT TRUNCATED AT 400 WORDS)