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Are we misunderstanding beta-blockers.

Cruickshank JM

Cambridge University, Long Melford, Suffolk CO10 9DE, United Kingdom. johndtl@aol.com

In myocardial ischaemia and heart failure, beta-blockers with intrinsic sympathomimetic activity (ISA) e.g. pindolol, xamoterol, bucindolol, nebivolol, have performed poorly in reducing morbidity and mortality. In both indications beta-1 blockade is the vital active ingredient. Beta-1 blockade (bisoprolol) is now an alternative first-line choice to Ace-inhibition in the treatment of heart failure. The therapeutic role of beta-blockers in hypertension is less well understood, particularly since the new recommendations in the UK from the NICE committee stating that: 1. beta-blockers are no longer preferred as a routine initial therapy, 2. the combination with diuretics is discouraged due to the risk of induced diabetes, and 3. in younger patients first-choice initial therapy should be an ACE-inhibitor. Recent data from the Framingham Heart Study and other epidemiological studies have indicated that the development of diastolic hypertension in younger subjects is closely linked to weight-increase and an increase in peripheral resistance; such subjects have a high adrenergic drive and cardiac output. In contrast, elderly systolic hypertension mostly arises de novo via poor vascular compliance. Thus in younger, probably overweight, hypertensives (including diabetics) first-line beta-blockade has performed well in preventing myocardial infarction (a fact hidden by meta-analyses that do not take age into account). Conversely, in elderly hypertensives first-line beta-blockade (atenolol) has performed poorly in reducing cardiovascular risk (due to partial beta-2 blockade atenolol evokes metabolic disturbance and does not improve vascular compliance, or effectively lower central aortic pressure or reverse left ventricular hypertrophy). Thus beta-blockers like atenolol are ill-equipped for first-line therapy in elderly hypertension. Some beta-blockers, e.g. bisoprolol (up to 10 mg/day is highly beta-1 selective) and nebivolol (beta-2/3 intrinsic sympathomimetic activity), do improve vascular compliance and cause no metabolic disturbance. Beta-blockers as second-line to low-dose diuretics (which, by improving vascular compliance and increasing sympathetic nerve activity, create an optimal environment for beta-blockade) in elderly hypertension (including diabetics) have performed well in reducing cardiovascular events (this combination has the added bonus of reducing the risk of bone fracture by about 30%). Meta-analyses which include studies where it is unclear whether a diuretic or beta-blocker was a first-line therapy will dilute the benefit stemming from first-line diuretic/second-line beta-blockade. Hypertensives (of all ages) with ischaemia are well suited to beta-blockade.

Published 9 July 2007 in Int J Cardiol, 120(1): 10-27.
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