Objective assessment of "cardioprotective" efficacy as a prognostic guide to management of mildly symptomatic revascularizable coronary artery disease
R Lim,
L Dyke,
and
DS Dymond
Department of Cardiology, St. Bartholomew's Hospital, West Smithfield, London, England, United Kingdom.
OBJECTIVES. The concept of "cardioprotection" based on ejection fraction was tested to see whether patients with coronary artery disease in whom medical treatment fails to be cardioprotective can be distinguished from those in whom it is safe to continue such treatment. BACKGROUND. Ejection fraction is of fundamental prognostic importance. Its modification by anti-ischemic medication may allow assessment of cardioprotection from adverse outcome. METHODS. Exercise ejection fraction and the change in ejection fraction from rest to exercise were measured by radionuclide ventriculography with and without background medication in 102 mildly symptomatic patients with coronary artery disease suitable for revascularization but initially treated medically. RESULTS. Over 20 months, 23 patients experienced an adverse event. With medication, exercise ejection fraction increased in patients with and without events. By contrast, the ejection fraction response to exercise improved significantly in the event-free group only; the group with events had a persistent decrease in ejection fraction. By Cox analysis, the ejection fraction response to exercise performed with medication made the most significant independent contribution to event-free survival. Comparison of areas under receiver operating characteristic curves suggested that this index is the most useful clinical measure of cardioprotection. CONCLUSIONS. An exercise-induced decrease in ejection fraction despite anti-ischemic medication implies failure of cardioprotection and a greater short-term risk of adverse outcome and crossover to revascularization in patients initially treated medically. Conversely, a preserved left ventricular performance confers a satisfactory prognosis while continuing with that treatment. Thus, the effect of medication on the ejection fraction response to exercise--a reasonable estimate of its cardioprotective efficacy--may influence the choice of continuing with such treatment or performing early revascularization.
