Left Bundle Branch Block (LBBB) and STEMI criteria

Left bundle branch block is manifested on the ECG with wide QRS with deep slurred QS complex in V1 and slurred R wave in V6. ST segment and T wave vectors are discordant to the QRS vector, meaning that when the QRS positive as in V6, the ST segment will be depressed and T wave will be inverted. This is known as secondary ST – T abnormality. If the ST segment and T wave are concordant to the QRS, it indicates a primary myocardial abnormality. An elevated ST segment and an upright T wave in V6 with a positive QRS is taken as an evidence of myocardial infarction / ischemia in the presence of left bundle branch block (LBBB). Other evidences of myocardial infarction in the presence of LBBB are typical coved ST elevation, prominent R waves in V1 and Q waves in V6. Usually the initial r wave in V1 and initial q wave in V6 represents initial left to right activation of the interventricular septum. In LBBB, the initial left to right activation of the septum is absent. In the 2004 guidelines for the management of ST segment elevation myocardial infarction (STEMI), new or presumably new LBBB was considered as equivalent to STEMI. Many cases in which catheterization laboratory was activated and emergency angiogram done showed no acute coronary artery occlusion. Hence the 2013 guideline removed this recommendation. But this could lead to denial of reperfusion therapy in those who actually have an acute coronary occlusion with LBBB on ECG. In this situation, Sgarbossa electrocardio...
Source: Cardiophile MD - Category: Cardiology Authors: Tags: ECG / Electrophysiology Selvester 10% RS criteria Sgarbossa criteria Smith 25% S-wave criteria Source Type: blogs