CRT treatment should be considered in lieu of CCM in patients with left bundle branch block ( LBBB ) and a QRS duration of over 120 ms, or when the QRS duration is greater than 150 ms and independent of LBBB.
32.
Other EKG signs include a right bundle branch block as well as T wave inversions in the anterior leads, which are " thought to be the consequence of an ischemic phenomenon due to low cardiac output in the context of RV dilation and strain ."
33.
A subset of individuals with the triad of first-degree heart block, right bundle branch block, and either left anterior fascicular block or left posterior fascicular block ( known as trifascicular block ) may be at an increased risk of progression to complete heart block.
34.
People with bundle branch blocks may still be quite active, and may have nothing more remarkable than an abnormal appearance to their ECG . However, when bundle blocks are complex and diffuse in the bundle systems, or associated with additional and significant ventricular muscle damage, they may be a sign of serious underlying heart disease.
35.
A mnemonic to distinguish between ECG signatures of left bundle branch block ( LBBB ) and right, is WiLLiaM MaRRoW; i . e ., with LBBB, there is a W in lead V1 and an M in lead V6, whereas, with RBBB, there is an M in V1 and a W in V6.
36.
Although Tawara's monograph had demonstrated that the branches of the bundle of His may transmit cardiac action potentials to the ventricles, the functional proof for his observation was not provided until 1910, when Hans Eppinger and Carl Julius Rothberger showed that cutting off both branches to induce a bilateral bundle branch block results in a complete heart block.
37.
ECG findings associated with pulmonary emboli may suggest worse prognosis since the six findings identified with RV strain on ECG ( heart rate > 100 beats per minute, S1Q3T3, inverted T waves in leads V1-V4, ST elevation in aVR, complete right bundle branch block, and atrial fibrillation ) are associated with increased risk of circulatory shock and death.
