Stress recovery index for risk stratification of asymptomatic patients following coronary bypass surgery.
OBJECTIVE
To prospectively assess the prognostic value of the stress recovery index (SRI) following coronary bypass surgery.


METHODS
Two hundred seventy-eight patients who had undergone coronary bypass surgery and participated in a secondary prevention program were exercise tested and prospectively followed up for a median of 36 months. Cardiac death, nonfatal infarction, and need for further revascularization were target end points. SRI, defined as the difference in absolute values between the area of heart rate-adjusted ST-segment depression during exercise and recovery, was derived in all. Clinical data, resting ejection fraction, and exercise testing data of patients were entered into a sequential Cox model; SRI was entered last. Model validation was performed by bootstrap adjusted by the degree of optimism in estimates. Survival curves were set up using Kaplan-Meier method and compared by the log-rank test.


RESULTS
SRI was the only significant and independent prognostic indicator (hazard ratio, 0.68; 95% confidence interval, 0.53 to 0.89) and increased the prognostic power of the model on top of clinical and exercise testing variables, as demonstrated by the significant (p = 0.01) increase of the area under the receiver operating characteristic curve of the risk function. Survival analysis showed ascending SRI quartiles to identify a significant (p = 0.001) increase in event-free survival.


CONCLUSIONS
SRI is of value in predicting outcome after coronary bypass surgery and provides additional prognostic information over clinical and exercise testing data.
Bigi
Riccardo
R
Cardiology, Department of Medical and Surgical Sciences, S. Paolo Hospital, Via A. di Rudinì 8, 20142 Milan, Italy. Riccardo.Bigi@unimi.it
Gregori
Dario
D
Cortigiani
Lauro
L
Colombo
Paola
P
Fiorentini
Cesare
C
D000368:Aged; D001026:Coronary Artery Bypass; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012372:ROC Curve; D020127:Recovery of Function / Q000502:physiology*; D016019:Survival Analysis