Compared with placebo, β-blockers decrease the risk of stroke by only 19% when used to treat primary hypertension—about half the decrease in risk determined by some previous studies that proved highly influential in the creation of treatment guidelines, according to a metaanalysis of randomized trials involving 105,951 patients.
The metaanalysis also showed that the risk of stroke is 16% higher with β-blocker treatment than with other medications, and that β-blockers offer no advantage in preventing myocardial infarction, reported Dr. Lars Hjalmar Lindholm of Umeå (Sweden) University Hospital, and colleagues (Lancet 2005;366:1545–53).
Considering that other antihypertensives, such as thiazide diuretics and ACE inhibitors, are as effective in reducing blood pressure as are β-blockers, are as inexpensive, and provide greater decreases in the risk of stroke, the authors concluded that β-blockers should not remain the first choice in the treatment of primary hypertension.
In an editorial, Dr. D. Gareth Beevers of City Hospital, Birmingham, England, suggested that many guidelines committees will have to rethink their endorsement of β-blockers for the first-line treatment of primary hypertension. He also said that the National Heart, Lung, and Blood Institute will have to rethink proposals to use β-blockers in long-term outcome studies of the treatment of systolic hypertension (Lancet 2005;366:1510–2).
But Dr. Beevers cautioned that widespread dissemination of this new metaanalysis in the popular media may encourage patients to discontinue β-blockers abruptly. Sudden discontinuation can result in rebound angina and can precipitate myocardial infarction.
Furthermore, some patients, such as those who have an anxiety disorder in addition to hypertension, may experience some symptomatic relief from β-blockers in addition to the antihypertensive effects.
If a physician decides to discontinue a patient's β-blocker, the best strategy would be to do this by down-titration while substituting alternative antihypertensive drugs.
The authors of the metaanalysis speculated on the reasons that β-blockers are less effective than other classes of drugs in reducing the risk of strokes in spite of the fact that they are just as effective in reducing blood pressure.
They noted that although β-blocker treatment reduces brachial blood pressure, it does not reduce central systolic blood pressure as much as ACE inhibitors, diuretics, and calcium antagonists. Regression of left ventricular hypertrophy is more closely associated with patients' central blood pressure than with their brachial blood pressure, the authors asserted.