Age, Hypertension, and Exercise Capacity are Independently Associated with Likelihood of Multi-Vessel Disease in Patients Referred for Treadmill Exercise Testing: The Intermediate-High-Workload Treadmill Score (IHWTS)

Abstract

Background: To identify factors that increase the specificity of the treadmill exercise test (TMET), and develop a novel scoring system which accounts for functional capacity to aid in determining the need for further testing.

Methods: We retrospectively evaluated the electronic health records of 600 patients who had positive TMET results and follow-up stress echocardiography from 1-January-2004, through 31-December-2016. Correlations between clinical and aerobic variables and multivessel disease (MVD) were determined. Duke Treadmill Score (DTS) was calculated and compared with a novel scoring system titled the Intermediate-High-Workload Treadmill Score (IHWTS) that used variables associated with MVD.

Results: In total, 124 of 600 patients (21%) had coronary catheterization, and 51 of these patients (41%) had MVD. Mean (SD) DTS was -2.10 (6.3) among patients with MVD vs -0.16 (5) among patients without MVD (p = 0.06). Mean (SD) functional aerobic capacity (FAC) was 76% (20%) among patients with MVD vs 90% (21%) among patients without MVD (p $<$ 0.001). Mean (SD) metabolic equivalent (MET) was 7 (2) among patients with MVD vs 8 (2) among patients without MVD (p = 0.002). Only 6 (12%) of patients with MVD achieved 9 MET or greater on TMET. DTS less than 4 did not distinguish between patients with and without MVD (p = 0.67). Age, hypertension and FAC were independently associated with MVD (all p $<$ 0.05).

Conclusions: Our novel scoring system IHWTS utilized age, hypertension, and FAC appeared comparable to DTS to risk-stratify patients regardless of baseline symptoms. Clinical parameters such as hypertension along with exercise functional capacity should be considered when evaluating a positive TMET result in patients that achieve an intermediate-high workload $>$ 5 Metabolic Equivalents (METs).

Keywords: Intermediate-High-Workload Treadmill Score; coronary artery disease; exercise testing; preventive medicine.

Fig. 1.

Receiver operating characteristic curves of the Duke Treadmill Score and the High-Workload Treadmill Score. The Intermediate-High-Workload Treadmill Score took into account age, hypertension, and functional aerobic capacity. ROC, receiver operating curves.