The clinical significance of exercise-induced left ventricular wall motion abnormality occurring at a low heart rate

We studied the relationship between the heart rate at the time of onset of exercise-induced wall motion abnormality and the severity of coronary artery disease in 89 patients who underwent exercise oquilibrium radionuclide ventriculography as part of their svaluation for coronary artery disease. Segmental wall motion was scored with a five-point system (3 = normal; -1 = dyskinesis); a decrease of one score defined the onset of wall motion abnormality. The onset of wall motion abnormality at ≤70% of maximal predicted heart rate had 100% predictive accuracy for coronary artery disease and higher sensitivity than the onset of ischemic ST segment depression at similar heart rate during exercise: 36% (25 of 69 patients with coronary disease) vs 19% (13 of 69 pationts), p = 0.01. Wall motion abnormality occurring at ≤70% of maximal predicted heart rate was present in 49% of patients (23 of 47) with critical stenosis (≥90% luminal diameter narrowing), and in only 5% of patients (2 of 42) without such severe stenosis, p < 0.001. The sensitivity of exercise-induced wall motion abnormality occurring at a low heart rate for the presence of severe coronary artery disease was similar to that of a deterioration in wall motion by more than two scores during exercise (49% vs 53%) or an absolute decrease of ≥5% in exercise left ventricular ejection fraction (49% vs 45%). However, the early onset of wall motion abnormality was more specific for the identification of patients with critical stenosis than deterioration of exercise wall motion by two or more scores (95% vs 71%, p < 0.01) and decrease in ejection fraction (95% vs 79%, p < 0.05). Therefore, the onset of exercise-induced wall motion abnormality at ≤70% maximal predicted heart rate is a relatively infrequent but strong predictor of coronary artery stenosis, implies severe disease, and is superior to exercise ECG in predicting disease presence and severity.