Electrocardiographic manifestation of the middle fibers/septal fascicle block: a consensus report

Quadrifascicular?

“…1 from that article has been widely reproduced and indeed appears as an illustration in the article on "Middle-fibers/ septal fascicle block" in this issue of the Journal. 2 Demoulin and Kulbertus correlated their anatomical findings with the electrophysiological results of Durrer et al 6 in that "3 endocardial areas of the left ventricle were synchronously excited 0 to 5 milliseconds after the start of left ventricular cavity potential. These 3 islands of initial excitation may reasonably be assumed to correspond to the termination areas of the three main parts of the left bundle-branch system."…”

Unusual Conduction Disorder: Left Posterior Fascicular Block + Left Septal Fascicular Block

“…In the absence of RVH/RVE, latero-basal myocardial infarction, right bundle branch block, type A Wolff-Parkinson-White pattern, obstructive and nonobstructive forms of hypertrophic cardiomyopahty, endomiocardial fibrosis, muscular dystrophy, and dextroposition; it strongly suggests left septal fascicular block (LSFB). 1,2 The combination of LPFB + LSFB has not been properly documented yet and this is the first report that confirms this association. 3 The postoperative ECG (Fig.…”

Delay in or block of conduction through the middle (septal) fibers of the left bundle branch: can it be recognized on the body surface electrocardiogram?

“…If depolarization of enough of the IVS resulted via septal branches of the RBB in LSFB, there might be minimal consequences on the magnitude or direction of mid-to-late QRS forces. Development of prominent anterior mid-to-late QRS forces would be most likely, if activation of the IVS via RBB septal fibers was delayed or minimal, and as pointed out by Bayes de Luna et al, 5 some examples in the literature purporting to be LSFB may have just been variants of right bundle-branch block. The latter authors, unfortunately, did not extend their review to include the possible changes LSFB might cause when combined with other left or right fascicular blocks.…”