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Effect of beta-blockade on low heart rate-related ischemia during mental stress
C N Bairey1, D S Krantz, V DeQuattro
1Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California 90048.
Insights
Beta-blockers like metoprolol effectively reduce exercise-induced ischemia in coronary artery disease patients. However, their effect on mental stress-induced ischemia is variable, potentially due to unblocked blood pressure increases.
Area of Science:
- Cardiology
- Pharmacology
Background:
- Coronary artery disease (CAD) can lead to myocardial ischemia, often exacerbated by stress.
- Beta-adrenergic blockade is a standard treatment for CAD, but its effects on stress-induced ischemia, particularly from mental stress, require further investigation.
Purpose of the Study:
- To investigate the impact of beta-adrenergic blockade with metoprolol on ischemia triggered by mental stress versus exercise in patients with CAD.
- To compare the heart rate thresholds for ischemia during mental stress and exercise under placebo and metoprolol treatment.
Main Methods:
- A double-blind, randomized crossover trial involving 19 CAD patients.
- Patients underwent serial mental stress and bicycle exercise tests during placebo and metoprolol (100 mg twice daily) administration.
- Myocardial ischemia was assessed via wall motion abnormalities.
Main Results:
- Mental stress induced ischemia at significantly lower heart rates than exercise during placebo (81 vs. 123 bpm).
- Metoprolol reduced exercise-induced ischemia but had a variable effect on mental stress-induced ischemia, with 50% improving and 29% worsening.
- Metoprolol did not consistently block mental stress-induced blood pressure elevations, and this lack of effect correlated with worsened ischemia in some patients.
Conclusions:
- Beta-blockade shows variable efficacy in mitigating mental stress-induced ischemia in CAD patients.
- The inconsistent response may be linked to metoprolol's limited effect on mental stress-induced blood pressure surges and potential influences on coronary vasomotor tone.
- Patients with more easily inducible ischemia may experience less benefit or even worsening of ischemia during mental stress under beta-blockade.
Abstract:
To explore the effect of beta-adrenergic blockade on low heart rate-related (mental stress) ischemia, 19 patients with coronary artery disease were randomized into a double-blind crossover trial of metoprolol, 100 mg twice daily, and underwent serial mental stress/bicycle exercise studies. Mental stress-induced wall motion abnormalities occurred at a lower heart rate than exercise-induced wall motion abnormalities during placebo administration (81 +/- 16 vs. 123 +/- 20 beats/min, p less than 0.05). Metoprolol reduced the mean magnitude of exercise-induced wall motion abnormalities (2.8 +/- 2.0 vs. 1.6 +/- 2.4, p = 0.003); improvement was related to the magnitude of hemodynamic beta-blockade effect. Metoprolol did not significantly reduce the mean magnitude of mental stress-induced wall motion abnormalities (3.0 +/- 2.2 vs. 2.6 +/- 2.2), although individual responses predominantly either improved (50%) or worsened (29%). Unlike exercise, the magnitude of hemodynamic beta-blockade did not predict mental stress response and metoprolol did not block mental stress-induced blood pressure elevations. Patients with abolition of exercise-induced ischemia were more likely to have reduction of mental stress-induced ischemia. Patients whose ischemia worsened with metoprolol during mental stress had more easily inducible ischemia, as assessed by exercise-induced placebo wall motion abnormality, chest pain and prior myocardial infarction. Beta-blockade was associated with a lowering of ischemia-related hemodynamic thresholds compared with placebo. These results suggest that beta-blockade has a variable effect on low heart rate-related ischemia that may be due to a lack of effect on mental stress-induced blood pressure elevation in patients with easily induced ischemia or to effects on coronary vasomotor tone, or both.