Are intraventricular gradients a cause of false positive treadmill exercise tests?

BACKGROUND: Treadmill exercise testing has low specificity for the detection of significant epicardial coronary artery disease (CAD). A possible mechanism to explain some of the false positives is transient subendocardial ischemia induced by intraventricular gradients (IVG) during stress. The development of IVG during dobutamine stress echocardiography (DSE) occurs in 8-38% of non-selected populations.

OBJECTIVES: To determine: 1. the prevalence of IVG in a selected population of false positives on treadmill stress testing; 2. whether this prevalence is different from that described for non-selected populations; 3. whether patient characteristics are related to the presence of IVG; 4. the relation between the presence of IVG and the occurrence of ECG abnormalities, symptoms and blood pressure.

METHODS AND RESULTS: We evaluated 50 consecutive patients with false positive treadmill stress tests (normal CT coronary angiography, nuclear perfusion tests or angiography) with DSE (2D and Doppler evaluation). All DSE exams were negative for ischemia. Stress-induced IVG was seen in 34 of the 50 patients (68%) and 16 patients (32%) did not develop IVG (p<0.05). The prevalence of IVG in our selected population (68%) was significantly higher than that described for non-selected populations (8-38%) (p<0.001). Most patient characteristics (gender, age, risk factors for CAD, treatment with beta-blockers/calcium antagonists, significant valvular disease/left ventricular hypertrophy [LVH], symptoms, and blood pressure during stress) were not statistically associated with the prevalence of IVG (p>0.05). However, the presence of IVG was associated with the occurrence of ischemic ST depression during dobutamine stress echo (p<0.05).

CONCLUSIONS: 1. The prevalence of IVG during dobutamine stress echocardiography in a selected population of false positives on treadmill stress testing is very high, occurring in more than two-thirds of patients. 2. This prevalence is significantly higher than that described for non-selected populations. 3. Age, gender, risk factors for CAD, treatment with beta-blockers/calcium channel antagonists, significant valvular disesase/LVH, symptoms and blood pressure during stress were not associated with the presence or absence of IVG. 4. The presence of IVG is associated with the occurrence of ischemic ST changes during dobutamine stress echocardiography.