Age-Dependent Effect of β-Blockers in Preventing Vasovagal Syncope
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BACKGROUND: β-blockers have little effectiveness in preventing vasovagal syncope in unselected populations, but they might be effective in older patients. We determined whether β-blockers prevent vasovagal syncope in an age-related fashion. METHODS AND RESULTS: Two populations were studied. A proportional hazards analysis was performed on an observational cohort study of 153 patients with vasovagal syncope, 52 of whom received β-blockers. A multivariable proportional hazards model stratified by center was performed on 208 participants in the randomized Prevention of Syncope Trial (POST), examining the interaction between age group and treatment with metoprolol. Age-specific hazard ratios were estimated for both studies and combined using the inverse variance meta-analytic method. In the cohort study, the hazard ratio for syncope if treated with β-blockers was 1.54 (95% CI, 0.78-3.05) for patients aged <42 years and 0.48 (95% CI, 0.12-1.92) for patients aged ≥ 42 years. In POST, the proportional hazards model showed interactions between age and treatment effect (P=0.026). The hazard ratio for patients aged ≥ 42 years who received metoprolol was 0.53 (95% CI, 0.25-1.10); in patients aged <42 years, the hazard ratio was 1.62 (95% CI, 0.85-3.10). A pooled analysis of both studies yielded an estimate of the hazard ratio of 1.58 (CI, 1.00-2.31) for patients aged <42 years, and the hazard ratio was 0.52 (CI, 0.27-1.01) for patients aged ≥ 42 years. The 2 age groups differed significantly in response to β-blockers (P=0.007). CONCLUSIONS: β-blocker treatment may suppress vasovagal syncope in middle-aged patients aged >42 years.
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