ECG basics: Transition point скачать в хорошем качестве

ECG basics: Transition point

Normally, the R wave amplitude increases from lead V1 to lead V5 or V6. The S wave amplitude decreases from lead V1 or V2 to lead V6. Normally, amplitudes of the R wave and S wave are equal in lead V3 or V4. This is called a ‘transition point’ or ‘transition zone’. The transition point may shift toward the left ventricular leads and may be seen in leads V5 or V6. This is called clockwise rotation. This condition is often observed in pulmonary emphysema, dilated cardiomyopathy, and intraventricular conduction abnormalities. The transitional point may shift toward the right ventricular leads and may be seen in leads V1 or V2. This condition is called counterclockwise rotation. It may be observed in right ventricular hypertrophy, posterior myocardial infarction, WPW syndrome, and hypertrophic cardiomyopathy. In the case of the clockwise rotation, the deep S wave in lead V6 is called ‘persistent’. Normal R wave progression in the precordial leads is of great importance. Poor R wave progression may be the only sign of the anterior myocardial infarction. In this case, the R wave amplitude in leads from V1 to V3 (often in lead V4) is low. Some authors define this condition by R wave amplitude not more than 3 mm in lead V3. Other important causes of the poor R wave progression include lead misplacement, dextrocardia, mediastinal shift, left ventricular hypertrophy, and dilated cardiomyopathy.