Long term follow up study of prognostic significance of exercise duration during treadmill stress test in patients with stable coronary heart disease

Abstract

Treadmill stress tests provide useful noninvasive prognostic information in patients with coronary heart disease (CHD). The present study has prospectively analysed the long term prognostic value of exercise tolerance as measured by exercise time during treadmill stress test in 335 consecutive patients with stable CHD. 161 had exercise time of 6 minutes or less (mean 4.58 +/- 1.54 minutes) on a modified protocol (Group A) and 174 had exercise time of more than 6 minutes (mean 9.30 +/- 0.74 minutes)(Group B). Both groups were matched for major coronary risk factors (hypertension, smoking, diabetes and cholesterol levels) and type of drug therapy (betablockers, nifedipine, diuretics and aspirin). The patients have been followed up for upto 9 years with a mean of 6.28 +/- 2.99 years (Group A) and 7.87 +/- 1.98 years (Group B). Actuarial analysis shows that the overall survival after dropout due to death or coronary artery bypass surgery was significantly lower in group A [dropouts = 66 (41.0%)] than in Group B [dropouts = 19 (10.9%)] (Logrank test = 39.94, p < 0.001). The mortality was significantly higher in Group A with 58 deaths (36.0%) as compared to Group B with 16 deaths (9.2%) (x2 = 34.98, p < 0.001). The crude death rate was 5.73% per year in Group A as compared to 1.17% per year in Group B. The incidence of sudden deaths was also higher in Group A with 28(17.4%) instances as compared to 5(2.9%) in Group B (x2 = 19.85, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)