[Changes of ventricular activation time in patients with left anterior fascicle block and bifascicular block].

Recognition of left anterior fascicle block is usually a diagnostic problem. Isochrone maps, displaying results of the body surface potential mapping are helpful in solving this problem. The isochrone maps present changes of heart electric field, especially those concerning a pathway of the depolarization front propagation within the heart conduction system. Body surface potential mapping registrations were performed using a Fukuda Denshi cylindrical system, which enables simultaneous recordings of electrocardiographic signals from the 87 leads. The examined group consisted of 29 patients with left anterior fascicle block (LAFB) and complete right bundle branch block (RBBB) complicated by LAFB. The first group consisted of 7 females and 8 males with the mean age of 62 +/- 11.3 yr., and the second group comprised 8 females and 6 males (the mean age: 64 +/- 5.01 yr.). The control group comprised 30 healthy subjects--the mean age of 50.3 +/- 5.63 yr. In all of examined patients, elementary biochemical tests, echocardiography and X-ray chest examinations were performed. In order to obtain a pattern reflecting a depolarization trajectory in the patients' heart, the ventricular activation time maps (VAT) were constructed, using the own software. This kind of maps is more precise than standard electrocardiograms and makes possible monitoring an activity propagation, as well as its velocity within the heart conduction system. In the patients demonstrating left anterior fascicle block, a subendocardial layer of the bottom left surface of the interventricular septum is the earliest stimulated area of heart (similarly, as in normal subjects). Afterwards, the front of stimulation wave crosses the septum from left to right side. In the next phase, the activation comprises right surface of the septum, as well as subendocardial surfaces of right ventricle free walls, however in the free wall of left ventricle, as a result of left anterior fascicle block, the activation spreads through back part of bundle branch. At this moment, isochrone lines arrange in bottom-right-forward direction. Subsequently, the delayed stimulation wave penetrates the anterior and lateral walls. Isochrones on the right torso are directed rightward and upward. In the final phase, the activation spreads over remaining part of the free wall of left ventricle, moving leftward, upward and backward. On isochrone maps, the final stage of activation propagation is seen on whole upper back part of the torso. In patients demonstrating RBBB with LAFB, the stimulation time is notably delayed. As a result of blocking the right ventricle and left anterior fascicle, the stimulation wave goes to the free wall of left ventricle through the back bundle. Isochrones distribution is similar like in left anterior fascicle block. However, different time of stimulation dispersal in downward direction is observed. Next, the wave propagation moves downward and leftward, coming to the anterior and lateral walls. Later on, a stimulation of the remaining part of the left ventricle free wall is observed, and isochrones wander to the heart bottom. Finally, after about 80 ms from the beginning, a delayed stimulation wave reaches the right ventricle, passing around the blocked area and spreading through terminal fibres within right ventricle. In the both examined groups no significant differences in relation to isochrones distribution were observed, therefore the averaged VAT maps were assumed as a reference pattern for the given groups. A pattern of VAT maps distribution and values of ventricular activation time can be useful in the further investigations concerning an analysis of wave propagation in bundle branch blocks.