Epidemiological studies show that left ventricular hypertrophy (LVH) and hypertension (HT) in coronary artery disease (CAD) increases the risk for cardiovascular events including sudden cardiac death (SCD). According to experimental studies myocardial hypertrophy is associated both with altered electrophysiological properties (incl. prolonged repolarization) and increased vulnerability to ischemia. However, human data to support a repolarization related mechanism for the increased SCD risk has not been provided. We therefore studied 187 patients undergoing 3-dimensional vectorcardiographic monitoring during coronary angioplasty. Eight parameters reflecting different aspects of ventricular repolarization were used: (1) the ST segment (ST-VM & STC-VM), (2) the T vector (QRS-T angle, Televation & Tazimuth), and (3) the T vector loop (Tavplan, Teigenv & Tarea). Data collection was performed at rest and at the time of maximum ischemia during coronary occlusion. The patients were divided into 3 groups: 33 patients with ECG-signs of LVH (18 with HT), 54 with HT but without LVH-signs, and 100 patients with neither. CAD patients with LVH not only had the most abnormal baseline repolarization (as expected), but also a significantly more pronounced repolarization response during coronary occlusion, while HT patients had mean parameter values between LVH patients and those without neither HT nor LVH-signs. Because there is a relation between increased SCD risk and repolarization disturbances in various clinical settings, the results of the present study are in agreement with animal data and epidemiological observations, although other factors than disturbed repolarization might be of importance.