January 1, 1999Japanese Circulation JournalOpen Access

Beneficial Effects of Heart Rate Reduction on Cardiac Mechanics and Energetics in Patients With Left Ventricular Dysfunction

Q: What is the clinical evidence from this study?

Population: Left ventricular dysfunction (n=14). Intervention: Zatebradine (heart rate reduction) vs. Basal condition (spontaneous sinus rhythm). Primary outcome: Mechanical efficiency (EW/MVO2) (p=<0.05).

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Key result

Zatebradine-induced heart rate reduction improved mechanical efficiency from 25.9% to 29.7% (p<0.05) without decreasing myocardial contractility in patients with left ventricular dysfunction.

Why the study?

Does heart rate modulation via atrial pacing or zatebradine alter cardiac mechanics and energetics in patients with moderate left ventricular dysfunction?

Structured PICO

Does heart rate modulation via atrial pacing or zatebradine alter cardiac mechanics and energetics in patients with moderate left ventricular dysfunction?

Population

14 patients (mean age 55 years, 21% female) with moderate left ventricular dysfunction undergoing cardiac catheterization, evaluated acutely under basal, tachycardia, and bradycardia conditions.

Intervention

Sequential interventions: 1) Heart rate increased by 20% using atrial pacing for at least 15 minutes; 2) Heart rate decreased by 16% using zatebradine 7.5 mg oral, assessed 30 minutes after administration.

Comparator

Basal condition (spontaneous sinus rhythm) prior to interventions.

Outcome

Cardiac mechanics and energetics, specifically external work (EW), myocardial oxygen consumption (MVO2), and mechanical efficiency (EW/MVO2).surrogate

Main Result

Absolute Event Rate: 29.7% vs 25.9%

p-value: p=<0.05

In patients with moderate left ventricular dysfunction, mild bradycardia induced by zatebradine improves mechanical efficiency without depressing contractility, whereas pacing-induced tachycardia worsens cardiac energetics.

Limitations

Study performed without autonomic blockade, so reflex sympathetic stimulation cannot be excluded.
Patients had mild to moderate heart failure; results might differ in patients with severe heart failure and limited preload reserve.
Focused only on short-term effects on cardiac mechanics and energetics, which does not imply long-term mortality improvement.
Small sample size of 14 patients.
Precise mechanism of zatebradine's negative chronotropic action is somewhat controversial.
Patients had mild to moderate, not severe, heart failure, so results may not apply to severely depressed hearts.
Unclear if further heart rate reduction would be beneficial.
Unclear if MVO2 might alter over a wider range of heart rate changes.
Focused on short-term effects; does not imply long-term mortality benefit.

Discussion

No takes yet. Share an insight, caveat, or question.

Implication

Mild bradycardia may improve energetics in LV dysfunction without harming contractility; leaves open outcome benefits in larger trials.

Cite This Study

Shinke et al. (1999) studied Left ventricular dysfunction (n=14). Zatebradine (heart rate reduction) vs. Basal condition (spontaneous sinus rhythm) was evaluated on Mechanical efficiency (EW/MVO2) (p=<0.05). Zatebradine-induced heart rate reduction improved mechanical efficiency from 25.9% to 29.7% (p<0.05) without decreasing myocardial contractility in patients with left ventricular dysfunction.

synapsesocial.com/papers/6a22e6b34a4edab11060658b https://doi.org/10.1253/jcj.63.957

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Beneficial Effects of Heart Rate Reduction on Cardiac Mechanics and Energetics in Patients With Left Ventricular Dysfunction

Structured PICO

Main Result

Limitations

Discussion

Implication

Cite This Study

Beneficial Effects of Heart Rate Reduction on Cardiac Mechanics and Energetics in Patients With Left Ventricular Dysfunction

Structured PICO

Main Result

Limitations

Discussion

Implication

Cite This Study

Also Consider

Also Consider