Affiliation:
1. the First Department of Internal Medicine, Kobe University School of Medicine, Kobe, Japan.
Abstract
Background
The negative chronotropic effect of β-blocking agents is likely to provide hemodynamic and energetic advantages. However, the negative chronotropic effect on cardiac energetics observed on the initiation of β-blockade therapy has not been fully elucidated.
Methods and Results
In 18 patients with heart failure, left ventricular pressure and volume, external work (EW), myocardial oxygen consumption per beat (total V̇
o
2
), mechanical efficiency (EW/total V̇
o
2
), and V̇
o
2
for nonmechanical work (total V̇
o
2
−2·EW) were measured with the use of conductance catheter and Webster catheter at the following three states: under control conditions and after β-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 β-blockade with pacing and returned to the control level after pacing was stopped. Total V̇
o
2
did not change during β-blockade with or without pacing, whereas V̇
o
2
for nonmechanical work increased with pacing and returned to the control level after pacing was stopped. As a result, mechanical efficiency decreased during β-blockade with pacing and returned to the control level after pacing was stopped.
Conclusions
The negative chronotropic effect of a β-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 β-blockade therapy.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Physiology (medical),Cardiology and Cardiovascular Medicine
Cited by
38 articles.
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