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Negative Chronotropic Effect of β-Blockade Therapy Reduces Myocardial Oxygen Expenditure for Nonmechanical Work

1996; Lippincott Williams & Wilkins; Volume: 94; Issue: 3 Linguagem: Inglês

10.1161/01.cir.94.3.340

1524-4539

Hideyuki Yamakawa, Motoshi Takeuchi, Hideyuki Takaoka, Katsuya Hata, Masuki Mori, Mitsuhiro Yokoyama,

Heart Failure Treatment and Management

The negative chronotropic effect of beta-blocking agents is likely to provide hemodynamic and energetic advantages. However, the negative chronotropic effect on cardiac energetics observed on the initiation of beta-blockade therapy has not been fully elucidated.In 18 patients with heart failure, left ventricular pressure and volume, external work (EW), myocardial oxygen consumption per beat (total Vo2), mechanical efficiency (EW/total Vo2), and Vo2 for nonmechanical work (total Vo2-2.EW) were measured with the use of conductance catheter and Webster catheter at the following three states: under control conditions and after beta-blockade (0.15 +/- 0.07 mg/kg propranolol IV) with and without atrial pacing to keep the heart rate at control levels. Heart rate decreased after atrial pacing was stopped. EW decreased during beta-blockade with pacing and returned to the control level after pacing was stopped. Total Vo2 did not change during beta-blockade with or without pacing, whereas Vo2 for nonmechanical work increased with pacing and returned to the control level after pacing was stopped. As a result, mechanical efficiency decreased during beta-blockade with pacing and returned to the control level after pacing was stopped.The negative chronotropic effect of a beta-blocking agent may offset the mechanoenergetical deterioration resulting from its negative inotropic effect through a reduction in oxygen expenditure for nonmechanical work. These findings suggest that the negative chronotropic effect is an important aspect of beta-blockade therapy.