Fascicular Blocks: Update 2019

Figures

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  Fig. (1A). A: Staining of the left bundle branch [LBB], its divisions and the Purkinje network of a child who died at 2 days of age as a consequence of respiratory distress. The LBB system shows the typical configuration. The posterior division (D) is twice as wide as the anterior one (C), which, before reaching the posterior papillary muscle, gives off a distinct strand that covers the mid and posterior third of the lower septum. Both divisions are amply interconnected by the Purkinje network. (A): aorta; (B): LBB; (E): mitral valve. From Spach MS et al. [8]. (A higher resolution / colour version of this figure is available in the electronic copy of the article).

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  Fig. (1B). B: Demonstration of the left bundle branch (LBB), stained with iodine solution, of a normal young man’s heart. LBB emerges beneath the aortic valve and descends along the septum. After the short run, it gives origin to the anterior (AD) and posterior (PD) divisions, which are clearly seen heading for their respective papillary muscles. APM: anterior papillary muscle; PPM: posterior papillary muscle. The size and distribution of the divisions of the LBB are strikingly similar to those shown in Figure 1A. From Uhley HN and Rivkin LM [9]. (A higher resolution / colour version of this figure is available in the electronic copy of the article).

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  Fig. (2). Trifascicular block recorded from a 58-year-old man with severe coronary artery disease and an anteroseptal myocardial infarction. A: RBBB with LAH: AQRS -75°; QRS interval 0.13 sec; PR interval 0.16 sec. B: RBBB with LPH; AQRS + 110°; QRS interval 0.13 sec; PR interval 0.26 sec. C: both types of AQRS occur in the same tracing. The PR interval is longer when RBBB with LPH is present. See text for further description.

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  Fig. (3). Experimental LAH in a monkey heart. Left panel: A: Control tracing. B: LAH provoked after a gentle injury of the anterior division. The main QRS forces were oriented superiorly to the left and a Q1S3 develops. Right panel: C: The ECG of intermittent LAH of a patient with Steinert disease. In every lead, the first beat shows normal conduction and the second, LAH. Right bottom panel: D: The vectorcardiogram shows normal conduction (top) and LAH (bottom). See the text for further details.

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  Fig. (4). Left panel: Experimental LPH in a monkey heart (same animal as in Figure 3). A: Control tracing obtained after recovery of the previous injury. B: LPH caused by injuring the posterior division of the LBB. The main QRS forces were oriented inferiorly and to the right disclosing an S1Q3 pattern; C: C1: a 61-year-old man without apparent heart disease. The AQRS is ≈ +50° and the ECG tracing is normal. C2: a year later, the AQRS shifted to + 110° and except for the change of the electrical axis, the ECG may be considered normal. C3: The vectorcardiogram depicts the typical wide open clockwise-rotated loop in the frontal plane, whose initial forces are oriented superiorly and to the left and the terminal QRS forces inferiorly and to the right (≈ + 100°). The ECG and vectorcardiogram of LPH are the exact mirror picture of LAH in the standard and unipolar leads.

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  Fig. (5). Continuous strips of lead V1 obtained during carotid sinus massage from a patient with intermittent RBBB. The numbers indicate the RR intervals in hundreds of a second. After the longer pauses, RBBB entirely disappears and when the intervals get progressively shorter, high degrees of RBBB occur. It is to be noted that before reaching the pattern of complete RBBB, there are four QRS complexes showing prominent anteriorly directed forces with a narrow complex, which could be interpreted as a mid septal fascicular block.

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  Fig. (6). A: Diafragmatic sketches of the LBB system in twenty human hearts. The drawings represent “as closely as possible the location and width of the various left bundle ramifications” obtained by serial sections of the septum in the plane parallel to the atrioventricular ring. B: Four human LBB systems dissected and separated from the heart, which represent the main prototypes of our material. In every case, anterior and posterior divisions are observed. The bottom left LBB shows a medial septal fascicle emerging from a wide posterior division, a pattern that can also be observed in the examples of 6.A.