Final answer:
Patients with ECG left bundle branch block (LBBB) have a high false-positive rate with exercise stress tests because LBBB can mimic the ECG changes seen during exercise stress testing.
Step-by-step explanation:
Patients with electrocardiographic (ECG) left bundle branch block (LBBB) have a high false-positive rate with exercise stress tests because LBBB can mimic the ECG changes seen during exercise stress testing. LBBB can cause abnormalities in the QRS complex, which is the part of the ECG that represents ventricular depolarization. During exercise stress tests, the heart rate and workload are increased, which can further exaggerate the abnormal QRS complex in patients with LBBB, leading to a false-positive result.