Coronary heart disease: treadmill exercise score helps to predict four year survival.

Clinical bottom line (level 1a)

  1. 99% of patients with suspected coronary artery disease who are considered low risk on the treadmill exercise score, will be alive at four years.
  2. 95% of patients considered moderate risk on the exercise treadmill score, will be alive at four years.
  3. 79% of patients considered high risk will be alive at four years.
Mark et al: New England Journal of Medicine 1991; 325 (12): 849-853
Expires July 2003

The study

Prospective cohort study with objective outcomes, adjusted for confounding factors, validated in an independent set of patients.

Setting: university medical centre, USA

613 patients (aged mean 54 years, 67% male) outpatients referred to the cardiac noninvasive diagnostic unit with suspected coronary disease who had a treadmill test as part of their clinical evaluation

Excluded if
  • undergone cardiac catheterisation already
  • evidence of serious valvular, congenital or cardiomyopathic disease
  • uninterpretable ST-segment response

Cox proportional hazards model was used to adjust for confounding factors.

98% followed for mean 4 years
Outcomes studied: 
  • survival in low risk group 
  • survival with moderate risk 
  • survival with high risk
  • Patients had a standard treadmill test, and during this time three ECG leads were continually monitored. Exercise was continued until the development of limiting symptoms, abnormalities of rhythm or blood pressure, or marked and progressive ST-segment deviation.
  • The treadmill score was calculated as: duration of exercise in minutes -(5 x maximal net ST-segment deviation during or after exercise, mm)- (4 x treadmill angina index). The angina index has a value of 0 if the patients had no angina during exercise, 1 if the patient had nonlimiting angina and 2 if the patient stopped due to angina. High risk was defined as <-10, moderate risk as -10 to 4, and low risk > or =5.
  • The prognostic treadmill score was derived on a similar population of inpatients in the same institution.

The evidence

outcome time to outcome number of patients/total number %
(95% CI)
survival in low risk group mean 4 years 375/379 98.9%
(97.9% to 100%)
survival with moderate risk mean 4 years 200/211 94.8%
(91.8% to 97.8%)
survival with high risk mean 4 years 18/23 78.3%
(61.4% to 95.1%)

Comments

  1. The results from this validation set correspond well to those of the test set.
  2. Does not appear very useful, given the very low proportion of out-patients with a high risk score. Would these have been (quite obviously) the high-risk patients?

Citation

  1. Mark DB, Shaw L, Harrell FE, et al: Prognostic value of a treadmill exercise score in outpatients with suspected coronary artery disease. New England Journal of Medicine 1991; 325 (12): 849-853
Contributor: Clare Wotton and Bob Phillips, January 2000
Reviewer:

Clinical Question.
Patient coronary artery disease
Intervention or Exposure treadmill exercise score
Outcome predicting death from cardiovascular events