HealthDay News — The prognostic value of lower heart rate thresholds (defined as the percentage of age-predicted maximal heart rate achieved, or ppMHR) is attenuated for patients on beta-blocker therapy (BBT), according to a study published in the December 1 issue of The American Journal of Cardiology.

Rupert K. Hung, MD, from the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease in Baltimore, and colleagues conducted a retrospective cohort study involving 64,549 adults without congestive heart failure or atrial fibrillation who underwent clinician-referred exercise stress testing, with median follow-up of 10.6 years. The authors examined the effect of BBT, ppMHR, and estimated exercise capacity on mortality. 

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The researchers identified 9,259 deaths during follow-up. BBT correlated with an 8% lower adjusted achieved ppMHR (91 versus 83% for no BBT versus BBT). There was an inverse correlation for ppMHR with all-cause mortality, with significant attenuation by BBT (per 10% ppMHR, hazard ratio: no BBT, 0.80 versus BBT, 0.89). The adjusted mortality rate was similar for patients on BBT who achieved 65% ppMHR versus those not on BBT who achieved 85% ppMHR. The prognostic value of ppMHR was further attenuated by estimated exercise capacity (per 10% ppMHR, hazard ratio: no BBT, 0.88 versus BBT, 0.95).

“In conclusion, the prognostic value of ppMHR was significantly attenuated by BBT,” the authors write. “For patients on BBT, a lower threshold of 65% ppMHR may be considered for determining worsened prognosis.”

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