Design of comparative clinical studies of percutaneous transluminal coronary angioplasty using estimates from the
Insights
Designing a trial for percutaneous transluminal coronary angioplasty (PTCA) requires careful outcome selection. Mortality alone is insufficient; combined endpoints or functional measures like angina relief are more feasible for evaluating PTCA effectiveness.
Area of Science:
- Cardiovascular Medicine
- Clinical Trial Design
- Interventional Cardiology
Background:
- Percutaneous transluminal coronary angioplasty (PTCA) is a common intervention for coronary artery disease (CAD).
- Establishing the optimal design for prospective randomized trials comparing PTCA with conventional therapies is crucial for evidence-based practice.
Purpose of the Study:
- To discuss the design considerations for a prospective randomized trial of PTCA.
- To identify suitable patient populations and appropriate control therapies for PTCA trials.
- To evaluate potential outcome measures for comparing PTCA with control therapies.
Main Methods:
- Proposed patient candidates with proximal subtotal occlusion of one or more coronary vessels.
- Suggested control therapies: medical for 1-vessel CAD, medical/surgical for 2-vessel CAD, surgical for 3-vessel CAD.
- Evaluation of 10 outcome criteria (e.g., mortality, angina, MI, quality of life) against 9 desirable attributes.
Main Results:
- A trial solely on mortality is infeasible due to large sample size requirements.
- A combined death/myocardial infarction endpoint necessitates approximately 1,000 patients for multivessel CAD.
- Trials focusing on return to work (~950 patients) or pain relief (~500 patients) require substantial patient numbers.
Conclusions:
- Trial design for PTCA must balance feasibility with clinical significance.
- Outcome measures beyond mortality, such as functional status and symptom relief, are critical for PTCA evaluation.
- Sample size calculations highlight the need for efficient endpoint selection in PTCA trials.
Abstract:
The design of a prospective randomized trial of PTCA is discussed. It is suggested that patients with proximal subtotal occlusion of 1 or more vessels may be candidates for such a trial. Medical therapy as a control of 1-vessel CAD, medical or surgical therapy as a control for 2-vessel CAD (with 1 dilatable vessel) cases and surgical therapy as a control for 3-vessel CAD are most congruent with current practice. Possible criteria for comparison of PTCA with a control therapy include vital status, angina with daily activities, angina upon maximal exercise testing, MI, hospitalization, work status, cost, follow-up angiographic assessment, follow-up radionuclide ventriculography, measurement of immediate anatomic or hemodynamic change during initial treatment and quality-of-life indexes. These 10 measures are evaluated with respect to 9 desirable attributes for outcome criteria: the importance of the quantity measured, reproducibility, accuracy, low influence of investigator bias, low influence of subject bias, the measure is inexpensive and easy to obtain, sufficient occurrence to detect important differences, convenient to patients and measuring impairment due to disease. Examination of data from the Coronary Artery Surgery Study suggests that (1) a trial based on mortality alone is not feasible (because of a needed sample size in the thousands); (2) a trial using a combined death and/or MI end point would need approximately 1,000 cases even for patients with multivessel CAD; (3) approximately 950 patients would be needed in a trial to evaluate return to work (within 10%); (4) a trial based on pain relief (within 15% of the control group) would need 500 subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
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