Coronary artery surgery study revisited. Limitation of the intent-to-treat principle.
In the two recent 10-year follow-up Coronary Artery Surgery Study (CASS) reportsl-2 in this issue of Circulation, different analyses have been used: intent-to-treat analysis-ignoring a major amount of crossover to surgery-and examining the effect only while on the assigned treatment. The justification is presumed to be that with death and myocardial infarction as end points it is more prudent to adhere to the intent-to-treat principle, assessing the preventive aspect, whereas to evaluate the efficacy of a treatment in relieving symptoms or improving quality of life, the censored analysis examining the actual treatment employed is more relevant. Thus, we have two approaches, neither of which is entirely satisfactory, given the circumstances. With both groups (surgical and medical therapies) receiving medical treatment and a 40% crossover to surgery by medical-therapy patients based on clinical condition and accepted indications for surgery, it is difficult to sort out with confidence the impacts of the two therapies under consideration. The frequency of crossover surgery can be regarded as an outcome if it can be accepted that this indicates a failure of medical therapy. However, no criteria for this were specified in the design of CASS, so it is difficult to judge whether the option for surgery represents a real need or the application of conventional wisdom and hence a self-fulfilling prophesy. The management of patients with coronary disease has changed dramatically during the past several decades. Because absence or abolition of symptoms is no guarantee against coronary attacks and sudden death, the goals are now to prevent attacks and prolong life even when symptoms are absent. Medical therapy has now improved so that it is seldom impossible to relieve angina. The use of p-blockers, calcium antagonists, long-acting nitrates, and aspirin and intervention against coronary risk factors have The opinions expressed in this editorial comment are not necessarily those of the editors or of the American Heart Association. enabled physicians to treat patients for longer periods without resorting to revascularization. Along with these improvements in medical options there have been advances in revascularization procedures , now including coronary angioplasty. Also, improved myocardial preservation techniques have made coronary artery bypass graft (CABG) surgery a reasonable, safe procedure, and the increasing use of internal mammary artery grafts and supplementary platelet-active drugs have extended long-term graft patency. Revascularization for patients whose symptoms cannot be controlled by antianginal therapy or who cannot tolerate the medications required seems justified. Surgery in …