Abnormal heart-rate response during cardiopulmonary exercise testing identifies cardiac dysfunction in symptomatic patients with non-obstructive coronary artery disease.

BACKGROUND: Symptomatic non-obstructive coronary artery disease is a growing clinical dilemma for which contemporary testing is proving to be of limited clinical utility. New methods are needed to identify cardiac dysfunction.

METHODS AND RESULTS: This is a prospective observational cohort study conducted from December 2013 to August 2015 in two outpatient cardiology clinics (symptomatic cohort) and 24 outpatient practices throughout the US (healthy cohort) with centralized methodology and monitoring to compare heart-rate responses during cardiopulmonary exercise testing (CPET). Participants were 208 consecutive patients (median age, 61; range, 32-86years) with exercise intolerance and without prior heart or lung disease in whom coronary anatomy was defined and 116 healthy subjects (median age, 45; range, 26-66years). Compared to stress ECG, the novel change in heart-rate as a function of work-rate parameter (ΔHR-WR Slope) demonstrated significantly higher sensitivity to detect under-treated atherosclerosis with similar specificity. In men, area under the ROC curve increased from 60% to 94% for non-obstructive CAD and from 64% to 80% for obstructive CAD. In women, AUC increased from 64% to 85% for non-obstructive CAD and from 66% to 90% for obstructive CAD. ΔHR-WR Slope correctly reclassified abnormal studies in the non-obstructive CAD group from 22% to 81%; in the obstructive CAD group from 18% to 84% and in the revascularization group from 35% to 78%.

CONCLUSION: Abnormal heart-rate response during CPET is more effective than stress ECG for identifying under-treated atherosclerosis and may be of utility to identify cardiac dysfunction in symptomatic patients with normal routine cardiac testing.