A prognostic scoring system for arm exercise stress testing

Abstract

Objective: Arm exercise stress testing may be an equivalent or better predictor of mortality outcome than pharmacological stress imaging for the ≥50% for patients unable to perform leg exercise. Thus, our objective was to develop an arm exercise ECG stress test scoring system, analogous to the Duke Treadmill Score, for predicting outcome in these individuals.

Methods: In this retrospective observational cohort study, arm exercise ECG stress tests were performed in 443 consecutive veterans aged 64.1 (11.1) years. (mean (SD)) between 1997 and 2002. From multivariate Cox models, arm exercise scores were developed for prediction of 5-year and 12-year all-cause and cardiovascular mortality and 5-year cardiovascular mortality or myocardial infarction (MI).

Results: Arm exercise capacity in resting metabolic equivalents (METs), 1 min heart rate recovery (HRR) and ST segment depression ≥1 mm were the stress test variables independently associated with all-cause and cardiovascular mortality by step-wise Cox analysis (all p<0.01). A score based on the relation HRR (bpm)+7.3×METs-10.5×ST depression (0=no; 1=yes) prognosticated 5-year cardiovascular mortality with a C-statistic of 0.81 before and 0.88 after adjustment for significant demographic and clinical covariates. Arm exercise scores for the other outcome end points yielded C-statistic values of 0.77-0.79 before and 0.82-0.86 after adjustment for significant covariates versus 0.64-0.72 for best fit pharmacological myocardial perfusion imaging models in a cohort of 1730 veterans who were evaluated over the same time period.

Conclusions: Arm exercise scores, analogous to the Duke Treadmill Score, have good power for prediction of mortality or MI in patients who cannot perform leg exercise.

Figure 1

Kaplan–Meier plots of 5 and 12-year all cause (A and C, respectively) and cardiovascular mortality (B and D, respectively) with number of participants at risk and 95% CIs stratified by cut points into high and low-risk groups based on arm exercise scores.

Figure 2

The continuous curvilinear relationship between arm exercise scores and 5-year and 12-year all-cause (A and C, respectively) and cardiovascular survival (B and D, respectively) with associated scatter plots. HRR, heart rate recovery at 1-min postexercise; METs, arm exercise capacity in resting metabolic equivalents; STΔ, ST segment depression either <1 mm (0) or ≥1 mm (1).

Figure 3

Receiver operator curve plots for prognostication of 5-year and 12-year all-cause (A and C, respectively) and cardiovascular mortality (B and D, respectively) with arm exercise scores (Arm Score AUC), best fit model pharmacological myocardial perfusion imaging (MPI) study predictors (perfusion defect number, type and size and the change in heart rate from rest to peak stress; Best fit pharm MPI AUC), and an abnormal versus normal pharmacological MPI result (Abn pharm MPI AUC), for 1730 pharmacological evaluations performed during the same 1997–2002 time interval. AUC, area under the curve.