Endocardial catheter mapping was performed in 18 patients with left bundle branch block (LBBB). Four patients had no organic heart disease (group I), six had cardiomyopathy (group II), and eight had coronary artery disease and previous infarction (group III). Twelve patients had one septal site of left ventricular endocardial breakthrough, while six had two left ventricular endocardial breakthr...

In this review we present evidence from many experimental studies which challenge the concept of predestination of His bundle fibers. Using both intra- and extracellular His bundle pacing in the context of atrio-ventricular block and the development of bundle branch blocks these experimental studies provide the underlying mechanisms for the recent clinical findings showing the benefits of perma...

Electrophysiological studies (His bundle recordings and atrial stimulation) were performed in nine patients who manifested periods of both right and left bundle branch block (RBBB and LBBB). In seven of the patients, alternating bundle branch block appeared to reflect intermittent or chronic bundle branch block superimposed on incomplete (but electrocardiographically complete) block of the cont...

The tracings of two patients with acute myocardial infarction showing complete right bundle branch block and alternating block in the divisions of the left branch are presented. Both developed a type II (Mobitz) block which was attributed to a simultaneous interruption of conduction in the three main intraventricular tracts (trifascicular block). Left divisional blocks produced specific changes...

Right bundle-branch block occurred in 42.8% and left anterior hemiblock in 35% of 14 patients after surgical replacement of the tricuspid valve. The combination of RBBB with left anterior hemiblock is caused by injury to the branching portion of the bundle of His or more likely, by a lesion involving the pseudobifurcation. This study provides further proof that left anterior hemiblock may be pr...

A 52-year-old woman underwent an electrophysiologic prtKedure because of a 30-year history of recurrent episodes of paroxysmal tachycardia. The baseline sinus cycle length wa.s 600 msec and the QRS complexes had a left bundle branch block configuration, with a QRS duration of 120 msec. The atrial-His (AH) and His-ventricular (HV) intervals were 90 and 20 msec, respectively. Programmed atrial st...

Biventricular pacing has been used to treat patients with symptomatic heart failure, systolic left ventricular dysfunction and intraventricular conduction delays. This modality is usually reserved for the treatment of patients with a left bundle branch block pattern on electrocardiogram. We report the successful use of biventricular pacing in a patient with heart failure and a right bundle bran...

A cohort of 1,960 white men aged 40 to 56 years without initial apparent heart disease and with 11 years of annual rest electrocardiograms and 20 year mortality data was followed in the Chicago Western Electric Company Study. Incomplete right bundle branch block was found in 134 men (6.8%) at entry. During follow-up, 222 men developed such block, an incidence rate of 13.6%. Left axis deviation ...

A case of 70-year-old woman with ischemic heart disease is presented. The electrocardiogram showed atrial fibrillation and a tachycardia-dependent, left bundle branch block. A number of intermediate QRS patterns from normal intraventricular conduction to complete left bundle branch block were seen, and the transition was gradual. Increasing grades of aberrance were seen following a shorter prec...

Bundle branch block is a common cause of a widened QRS complex, and, as indicated in Table 1, different mechanisms may be responsible. Three are rate related and one is based upon retrograde invasion into the bundle branch. Those four mechanisms lead to the intermittent appearance of a bundle branch block pattern. Most commonly, bundle branch block is continuously present, so-called fixed bundl...