Left Posterior Fascicular Block in Canine and Primate Hearts

Watt, Thomas B.; Pruitt, Raymond D.

doi:10.1161/01.cir.40.5.677

Cited by 37 publications

(6 citation statements)

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“…Functional specificity of common bundle tracts might be obscured, however, by the syncytial nature of the specialized conduction pathways which form the peripheral Purkinje network. In earlier studies on the effects of septal lacerations on ventricular excitation (1)(2)(3)(4)(5), the lesions were designed to sever the connections of a major segment of that network not only with the main left bundle branch but also with the remainder of the network. That a properly placed small circumscribed lesion interrupting anterior fascicles of the left branch can evoke changes of left anterior fascicular block detectable in both direct and indirect electrocardiographic leads is supported by the final experiment reported in this paper (see Results).…”

Section: Discussionmentioning

confidence: 99%

“…• In both canine and primate hearts, interruption of some, but not all, of the fibers in the left bundle branch and its terminal fascicular network at midseptal level delays excitation of that portion of the left ventricular wall supplied by the interrupted fibers (1)(2)(3)(4). This delay is reflected in specific, characteristic electrocardiographic changes in direct epicardial leads.…”

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confidence: 99%

“…Such combined block frequently is associated with fibrosis in the anterolateral portion of the ventricular septum (9,12) and often coincides with or precedes some degree of atrioventricular block (7,9,10). Left posterior fascicular block causes less dramatic alteration of QRS form and is, therefore, more difficult to identify, especially in the presence of right bundle branch block (4).…”

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confidence: 99%

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Focal Lesions in the Canine Bundle of His: THEIR EFFECT ON VENTRICULAR EXCITATION

Watt

Pruitt

1972

Circulation Research

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The alterations in ventricular excitation resulting from production of discrete punctate electrocautery lesions in the canine bundle of His were studied. Electrocardiographs changes were correlated with lesions identified anatomically by microscopic examination of the atrioventricular bundle. Although partial or complete atrioventricular block developed from lesions at several levels of the atrioventricular bundle, changes in the form of the QRS complex appeared only when lesions involved the distal portion of the bundle. Such QRS changes were recorded in 21 of 32 instances when the lesion involved the branching portion of the common bundle but in none of 6 instances when the lesion involved only the nonbranching portion of the common bundle. This study, then, provides evidence for functionally distinct longitudinal fascicles only within the distal portion of the common bundle. The syncytial character of the terminal fascicular (Purkinje) network may minimize the electrocardiographic evidence for such functional specificity within the common bundle. KEY WORDS atrioventricular blockPurldnje fibers partial bundle branch block fascicular block focal lesions intraventricular conduction disturbances bundle of His electrocardiographic changes Sections perpendicular to the long axis of the bundle of His show features identifying index planes employed to locate longitudinally electrocautery lesions. Arrows indicate critical regions in each portion of illustration. A: most distal section of proximal bundle still not separated from atrial septum by continuous strand of fibrous tissue B: Most proximal section of midportion of bundle. Bundle is separated by continuous strand of fibrous tissue (arrow) from atrial septum. This section is defined as the proximal index plane. C: Last section of common bundle not showing a continuous strand of conduction fibers Unking common bundle with left branch. The top arrow indicates lower end of strand of fibers emerging from common bundle, Circulation Research, Vol. XXXI, Ociobtr 1972 at CONS CALIFORNIA DIG LIB on July 3, 2015 http://circres.ahajournals.org/ Downloaded from and the bottom arrow indicates upper end of strand of fibers entering the posterior left branch. D: Left branch fibers form continuous strand with common bundle (arrow). This section is defined as the distal index plane. The bar in the center of the figure represents 1 mm.

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Section: Discussionmentioning

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Focal Lesions in the Canine Bundle of His: THEIR EFFECT ON VENTRICULAR EXCITATION

Watt

Pruitt

1972

Circulation Research

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“…OTHER CRITERIA OF LEFT POSTERIOR FASCICULAR BLOCK According to Watt and Pruitt (1969) and Medrano et al (1972) the QRS duration can be slightly increased by about 10 ms, in isolated left posterior fascicular block. In group A of this series, the mean QRS duration was 97 ms.…”

Section: Presumptive Criteria Of Left Posterior Fascicular Blockmentioning

confidence: 99%

Spatial Frank vectorcardiogram in left posterior fascicular block. Criteria and correlation with clinical and electrocardiographic data.

Brohet¹,

Arnaud²

1977

Heart

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Computer processing of spatial QRS parameters (Frank vectorcardiogram) was used to study left posterior fascicular block. The best set of vectorcardiographic criteria was sought in order to characterise the classic pattern of left posterior fascicular block. Using these criteria, 18 cases were selected from a group of 4600 patients and 340 healthy subjects; isolated left posterior fascicular block was seen in 10 cases, and was associated with right bundle-branch block in 8 cases. It is shown that some external factors can influence the aspect of the spatial QRS loop in left posterior fascicular block: cardiomegaly tends to produce a superior displacement of the main QRS forces: right bundle-branch block enhances the superior displacement of the initial forces and shifts the main QRS forces more anteriorly and to the right. The 'masquerading effect' of the left posterior fascicular block on a concomitant inferior myocardial infarct was also shown. The most important diagnostic feature was the opposite direction of the initial forces (left anterosuperior) and the maximal vector (right postero-inferior): the angle between these two vectors averaged 152 degrees. Other criteria, such as the direction of rotation or the axis of the frontal loop, the vertical direction of the spatial loop, the presence of a Q wave in leads II, III, and aVF of the electrocardiogram, are not mandatory for the diagnosis of left posterior fascicular block.

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“…Theoretically, mechanical disruption involving the anatomic pathway of the left posterior division of the left bundle branch could result in an isolated LPFB without associated RBBB. Such occurrence is well documented in the animal laboratory (Watt and Pruitt, 1969), but has not been described in humans. We present in this report two cases of acute inferior wall myocardial infarction complicated by ventricular septal rupture associated with the development of isolated LPFB.…”

Section: Introductionmentioning

confidence: 97%

Isolated left posterior fascicular block associated with acquired ventricular septal Defect

Rokey

Chahine

1984

Clinical Cardiology

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Summary:Isolated left posterior fascicular block in the absence of associated right bundle-branch block is a rare electrocardiograpic finding. In view of its anatomy and the fact that it receives a dual blood supply, the posterior fascicle of the left bundle branch appears to be less vulnerable than the anterior fascicle or the right bundle. Mechanical disruption of the posterior fascicle can produce isolated left posterior fascicular block. This has been demonstrated in animal models. However, such occurence has not been noted in humans. We present two cases of inferior wall myocardial infarction, complicated by rupture of the inferior septum, resulting in isolated left posterior fascicular block. The development of isolated left posterior fascicular block complicating myocardial infarction may, therefore, serve to alert to the possible underlying septal rupture.

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Left Posterior Fascicular Block in Canine and Primate Hearts

Cited by 37 publications

References 7 publications

Focal Lesions in the Canine Bundle of His: THEIR EFFECT ON VENTRICULAR EXCITATION

Focal Lesions in the Canine Bundle of His: THEIR EFFECT ON VENTRICULAR EXCITATION

Spatial Frank vectorcardiogram in left posterior fascicular block. Criteria and correlation with clinical and electrocardiographic data.

Isolated left posterior fascicular block associated with acquired ventricular septal Defect

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