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Differential antianginal responsiveness to acebutolol
Insights
This study found that acebutolol, a cardioselective beta-blocker, significantly improved exercise performance in patients with coronary insufficiency and angina. However, patient response varied, with some showing substantial benefits while others did not.
Area of Science:
- Cardiology
- Pharmacology
Background:
- Coronary insufficiency and angina represent significant cardiovascular challenges.
- Cardioselective beta-blockers are used to manage these conditions.
Purpose of the Study:
- To evaluate the efficacy of acebutolol, a new cardioselective beta-blocker, in patients with coronary insufficiency and angina.
- To assess the impact of different acebutolol dosages on exercise performance and anginal symptoms.
Main Methods:
- A double-blind, randomized study involving six males with documented coronary insufficiency.
- Patients underwent graded treadmill exercise tests after ingesting 0, 200, or 400 mg of acebutolol.
- Performance was measured by time to angina/ECG changes, peak heart rate, peak double product, and peak oxygen consumption.
Main Results:
- All measured performance criteria improved with both 200 mg and 400 mg doses of acebutolol, with greater improvement at the higher dose.
- A significant interaction between acebutolol dose and patient response category was observed.
- Patient responsiveness was correlated with placebo performance and other individual factors.
Conclusions:
- Acebutolol demonstrated significant beneficial effects in responders across all evaluated criteria.
- Patients were categorized into distinct responder and non-responder groups.
- Individual factors, including baseline performance, influenced patient sensitivity to acebutolol.
Abstract:
Six unselected males suffering from documented coronary insufficiency and grade II to III angina were submitted to graded multistage treadmill exercise test on 3 separate occasions, 3.5 hours after ingestion of either 0, 200 or 400 mg of acebutolol, a new cardioselective beta-blocker. Control measures included the random allocation to 6 balanced sequences of administration, the rigid standardisation of double-blind experimental conditions and measurements, and two types of variance analysis (latin-square and split-plot). Performance was evaluated by measuring time elapsed before occurrence of anginal pain and ECG changes, peak heart rate, peak double product (heart rate x systolic pressure), and peak oxygen consumption. The mean values for all 5 criteria showed improvement with the 200 mg dose of acebutolol, and even more so with 400 mg, but this overall effect resulted mainly from the excellent response of 3 of the patients. When patients were grouped into 2 categories of responders and non-responders, a significant Dose x Category interaction was found for all criteria. Furthermore, maximal response under acebutolol was negatively correlated with values under placebo (0 mg); this correlation reached significance for peak heart rate and peak double product. It is concluded that (a) in responders, the beneficial effect of acebutolol was significant on all 5 criteria (p less than 0.05), (b) patients definitely fell into 2 categories of responsiveness and (c) the sensitivity of responders was partly linked to their performance under placebo and partly to unidentified individual factors.