Shift from left to right axis deviation during ischemia

A case report of a patient with persistent left anterior hemiblock admitted with acute ischemic heart disease is described. At effort during follow-up evaluation, the patient complained of retrosternal pain when the heart rate was 124 beats/min. No pathological ST-T changes were demonstrated at this time. At 133 beats/min, the precordial pain increased, the QRS axis displayed a marked shift to the right, and ischemic ST-T depression was recorded. In discussing this unreported phenomenon, it is pointed out that left anterior hemiblock does not necessarily represent an anatomical block of the atrioventricular bundle but may simply reflect a relative delay in conduction. In addition, acute ischemia may change the physiological behavior of the system resulting in slower conduction through the posterior rather than through the anterior atrioventricular bundle. The influence of left anterior and left posterior hemiblock on ischemic ST-T changes and on the coronary flow distribution is discussed.