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Right Bundle-Branch Block and Left Anterior Fascicular Block (Left Anterior Hemiblock) Following Tricuspid Valve Replacement By V. ARAVINDAKSHAN, M.D., MARCELO V. ELIZARI, M.D., AND MAURIcIo B. ROSENBAUM, M.D. Downloaded from http://circ.ahajournals.org/ by guest on April 29, 2017 SUMMARY 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 produced by a "central" lesion of the conduction system. An attempt was made to re-define the relationships of the bundle of His and bundle branches to the membranous septum and septal leaflet of the tricuspid valve and to correlate the site of surgical injury with the type of conduction disturbances produced. Additional Indexing Words: Atrioventricular block Bundle of His Pseudobifurcation Tricuspid valves are being replaced with increasing frequency for rheumatic and traumatic disease as well as for Ebstein's anomaly. 1-15 However, comprehensive studies of conduction disturbances following tricuspid valve replacement have not been reported. The purposes of this study were threefold: The first was to assess the overall incidence of the different conduction disturbances resulting from tricuspid valve replacement; the second was to correlate the type of conduction disturbance with the site of injury, and the third was to clarify why the anterior division of the left bundle branch (LBB), which is a left ventricular structure, may be injured in a surgical procedure done from the right side of the heart. T HE frequent occurrence of conduction disturbances following intracardiac surgery is well documented.1-4 Appreciation, early in the era of open heart surgery, of the close relationship of the conduction system to the postero-inferior margin of the membranous septum resulted in a rapid diminution of the incidence of postoperative atrioventricular (A-V) block following repair of high ventricular septal defects.5 The incidence of right bundle-branch block (RBBB), however, remains high,6 and recently, it has been shown that left anterior hemiblock7-9 may also occur after repair of high ventricular defects.6 10 From the Cardiovascular Division, Department of Medicine, University of Kentucky College of Medicine, Lexington, Kentucky. Supported by Cardiology Training Grant HE 05771 from the National Institutes of Health, U. S. Public Health Service. Work was done during Dr. Aravindakshan's tenure of a research fellowship from the Kentucky Heart Association and during Dr. Rosenbaum's visiting professorship at the University of Kentucky. Received June 9, 1970; accepted for publication July 23, 1970. Circulation, Volume XLII, November 1970 Surgical heart block Methods The case records and ECGs of 15 patients who survived tricuspid valve replacement at the University of Kentucky Medical Center between the years 1966 and 1968 were analyzed. There were eight females and seven males. Two patients had traumatic tricuspid insufficiency. The remaining 13 had rheumatic heart disease. In the 895 ARAVINDAKSHAN ET AL. 896 Table 1 Incidence of Conduction Disturbances Type of conduction disturbance No. of patients Comments Complete A-V block 1 Temporary complete A-V block and subsequent I-V conduction disturbance 2 Patient died 3 days after operation. Presence or absence of I-V conduction disturbances undetermined. I-V conduction disturbances present on ECGs taken after recovery of A-V conduction I-V conduction disturbances only No conduction disturbances Total 6 6 15 Table 2 Cases Showing I-V Conduction Disturbances Following Tricuspid Valve Replacement Downloaded from http://circ.ahajournals.org/ by guest on April 29, 2017 Case Age (yr) 1 2 3 4 5 6 7 8 44 44 29 29 38 59 35 17 Sex Valves replaced F M F F M F F M M, T M, T A, M, T A, M, T T M, T M, T A,M,T Mean QRS axis Preoperative Postoperative +900 Indeterminate Indeterminate -800 +1050 - 600 +600 - 600 +30° -100° +1050 +1000 +1000 +1000 +300 +450 Conduction disturbances Preoperative Postoperative IRBBB IRBB None RBBB None None None IRBBB Abbreviations: A = aortic valve; M = mitral valve; T = tricuspid valve; RBBB IRBBB - incomplete right bundle-branch block: LAH = left anterior hemiblock. two patients with traumatic tricuspid incompetence only the tricuspid valve was replaced. In eight, both mitral and tricuspid, and in five, mitral, tricuspid, and aortic valves were replaced. One patient with complete A-V block died without recovering A-V conduction; therefore, intraventricular (I-V) conduction disturbances (RBBB and left anterior hemiblock) could be evaluated in only 14 patients. Criteria for RBBB were a slow terminal QRS force directed anteriorly and to the right, and a QRS duration of 0.12 sec or more. Block was termed "incomplete" when QRS duration was less than 0.12 sec. Left anterior hemiblock was diagnosed when the AQRS became -450 or more.7-9 Left anterior hemiblock in the presence of RBBB wvas recognized when the axis of the QRS deflection (AQRS) became oriented superiorly between -60 and -120°, with a q1-S3 pattern and a very small r/S ratio in lead II.7 10, 16, 17 Results The incidence of conduction disturbances in the 15 patients are listed in table 1. Three of the 15 patients (20%) developed complete A-V = LAH and IRBBB LAH and RBBB LAH and IRBBB LAH and RBBB LAH and RBBB IRBBB IRBBB RBBB right bundle-branch block; block during operation and were paced. Two of these recovered A-V conduction a few hours later; the third patient died after 3 days without recovering A-V conduction. An immediate postoperative tracing was not available to determine the width of the QRS complex of the idioventricular beats in any of these three cases. Eight patients developed IV conduction disturbances, and in the remaining six patients neither A-V nor I-V conduction disturbances were observed in the postoperative ECGs. The I-V conduction disturbances are listed in table 2. Five patients developed left anterior hemiblock and six RBBB (incomplete in three). In all instances of left anterior hemiblock RBBB was also present (fig. 1). However, in two (cases 1 and 4), the degree of RBBB was not appreciably greater than before opeartion (fig. 2), and in one (case 3), left anterior hemiblock was transient and lasted less than 2 weeks (fig. 3). In case 1, Circalation, Volume XLIl November 1970 :>*_;fm+4s RBBB AND LEFT ANTERIOR FASCICULAR BLOCK O*W 897 t .. A 4 41W Pre-or. 4 i: -e v i F. 4 t _. '4 11 I aVR III alF aVL PostPr2wWy V % v2 +..+ - -t J ._r ft i 1~ _ lii - +t . _ trr, . ---4 - .0e -44'.rv - a v4 *F :. _ wsa _ S _aJw V5 V6 d rOtI'< --4 -,.. Downloaded from http://circ.ahajournals.org/ by guest on April 29, 2017 Figure 1 Case 2. T:he preoperative tracings showc an indeterminate mnean QRS axis, severe right ventricular hypertrophy, and a small degree of incomplete RBBB. The postoperative ECG is characteristic of RBBB with left anterior hemiblock. Note the change in the direction of the initial (HRS forces, with the appearance of a Q wave in leads I and aV1J, and the disappearance of q front leads III and aVF. These ECG changes have persisted. B.J.C. [I,41 Pre-o p ftt TIN Vil If-fllf --1,11M 1 t; INH110 11 Jill ttluLl1, 1-IR II .111 - eiI.,t on fl 1111 ft' I -tl 4ii |. W * .1 T it W .4 I:< -;: aVF aVL Ii it ti litil 1. V ;mj 1W;Oll Eii t-s,s ,, j.... ,!HI t. 11111l nmII .,2 i,.. [m. 1'' mu . - ,.+ [161l VI V2 V3 [ti-- V/2 V4 ,'. -,tH L; *1 ....:I. i. Ut 'I'''''I t l -1 Fi :.-,:I .1, 1Ii !.4 0; 11t4 .. - 1i.hlb 4H11 1,-i RMRI 01iiotq , $; ll4 ~I1J .V rt !1 -i. 14 -,:a7a Tn 7<1' dii .4114ft 11IT&. q,-, aVR it 414 i11 I IR Is Utt Post-op III 11 III I HR R'llill It 11 I I Hli; Ff F ..1-T" +R:I -. .Ir. HI$. f-t r 1 ttt N4. llt4'IlTV t1+ li 1,;uI XM~~~~~~~~~~~~~~~~ 1 lt~~~~~~~~~~~~~~~~~~~~1 llitiXtF r--tP «T '44 rrarTr -. Figure 2 Case 4. The preoperative tracings show an AQRS about +60', left ventricular hypertrophy, and RBBB with a QRS interval of 0.12 sec. The postoperative ECG shows, in addition, a high degree of left anterior hemiblock with deep S waves in leads II and IIl (as commonly seen i7i the presence of severe left ventricuilar hypertrophy). The AQRS has shifted to -60°. The degree of RBBB has nIot chaniged appreciably. These ECG changes have persisted. at Circulation, Volume XLII, November 1970 898 ARAVINDAKSHAN ET AL. E.B. Pre-op 1 I .. III ..... .... aVR aVL dVF VI*I Vnax W2 3 V V17 4 VA 'TY VI 01 V4 V5 V6 V4 V5 V6 +H+UH+H44++il H H4i-+ 2days Rost-op ........ Downloaded from http://circ.ahajournals.org/ by guest on April 29, 2017 I 2weeks Pbst-op 11 Ni aVR c/L dVF V1 V2 11 111 aVL aVR dVF V1 V2 1~~~~~~~~~~~~~~~ I V3 Figure 3 Case 3. The preoperative tracings show an AQRS at about +105° and biventricular hypertrophy. ECGs taken on the first and second postoperative days were characteristic of RBBB with left anterior hemiblock. The AQRS shifted to -60°. However, left anterior hemiblock was transient, and a third ECG on the 13th postoperative day showed ontly incomplete RBBB. The AQRS shifted back to about +1200. The patient died the next day. complete heart block occurred in the immediate postoperative period, and the left anterior hemiblock pattern emerged when normal A-V conduction was restored. In case 6, incomplete RBBB was seen after recovery from complete A-V block which lasted a day. In case 7, incomplete RBBB appeared in the immediate postoperative tracing but was not present in the ECGs taken 1 mo and 2 mo later. However, complete RBBB was seen in the tracing taken after 9 mo. Discussion Involvement of the anterior division of the LBB during tricuspid valve replacement may seem enigmatic, but appreciation of the anatomic relationships of the conduction system provides a reasonable explanation. The relationships of the conduction system to the tricuspid valve are illustrated in figures 4 and 5. The bundle of His comprises two segments: "penetrating" and "branching."4 7,17 21 The penetrating portion is protected within the rigid structure of the central fibrous body and is only a few millimeters superior to the insertion of the septal leaflet of the tricuspid valve. The branching portion extends from the point where the most posterior fibers of the LBB originate from the main bundle to the point marking the origin of the RBB and the most anterior fibers of the LBB. This segment of the bundle is precisely at the level of insertion of the septal leaflet of the tricuspid valve. There is no true bifurcation of the bundle of His in the human heart, but rather a branching segment from which the RBB and the two divisions of the LBB arise. The bundle Circulation, Volume XLII, November 1970 RBBB AND LEFT ANTERIOR FASCICULAR BLOCK Downloaded from http://circ.ahajournals.org/ by guest on April 29, 2017 Figure 4 Relationships of tricuspid valve to the conduction system in the human heart. Photograph taken from the right side, under the dissecting microscope (reduced from x10). The membranous septum (MS) has been separated from the muscular septum and the tricuspid valve has been removed, except for the insertion of the septal leaflet (T). The conduction system has been dissected. The right bundle branch (RBB) appears as direct contin-uation of the bundle of His, which is from the oval-shaped structure of the A-V node (AVN). HB indicates the penetrating portion of the butndle. The two arrows indicate the limits of the branching portion, from which the left bundle branch (LBB) is given ofF. The inferior arrow also points to the pseudobifurcatiotn of the bundle of His into a right bu-ndle branch and anterior part of the left bundle branch a seen to arise of His gives off the fibers of the LBB almost perpendicularly in an orderly and sequential fashion. After the posterior fibers have been given off, the bundle contains only the fibers of the RBB and the anterior division of the LBB. What appears in some microscopic sections as a bifurcation (fig. 5) is in fact the point at which the RBB separates from the most anterior fibers of the LBB. This "pseudobifurcation"0'17,22 is only a few millimeters below the insertion of the septal leaflet of the tricuspid valve. A small lesion at this site may produce RBBB and left anterior hemiblock simultaneously. It should be stressed that the RBB is a direct continuation of the bundle of His after all the fibers of the LBB have been given off. The, initial segment of the RBB is located a few millimeters below the insertion of the septal leaflet of the tricuspid valve. Although the RBB is Circulation, Volume XLII, November 1970 899 considered a right ventricular structure and the LBB and its two divisions are considered left ventricular structures, all three are centrally located in the upper part of the muscular septum and within the thin fibrous sheath of the membranous septum and, therefore, can be involved in pathologic processes stemming from either side of the heart. Depending upon the site and extent of injury (fig. 6) to the conducting system, five types of conduction disturbances may be expected after tricuspid valve replacement: (1) Monofascicular complete A-V block with a narrow QRS complex due to a lesion of the penetrating portion of the bundle of His. (2) Complete A-V block with a wide QRS complex due to an extensive lesion of the branching portion. This has been termed a "proximal" form of bifascicular block.22 Un fortunately, no postoperative tracings of our cases with complete A-V block showing idioventricular beats were available to test these two possibilities. (3) RBBB with left anterior hemiblock due to a lesion limited to the branching portion after the posterior fibers of the LBB have been given off, or more likely, to a lesion of the pseudobifurcation (site 3 and 3' of fig. 6). This occurred in five of our 14 cases. (4) RBBB alone due to a lesion of the initial segment of the RBB and this was seen in three of our cases, and (5) left anterior hemiblock alone due to a lesion of the proximal end of the anterior division of the LBB. An example of left anterior hemiblock alone, however, was not seen in our cases. This type of correlation of the site of injury to the ECG manifestations is an oversimplification because surgical injury is often diffuse and involves more than one area, but nonetheless our data are consistent with such correlations. Condorelli23 obtained RBBB in canine hearts by partial transection of the bundle of His (probably at the level of the branching portion). Sciacca and Sangiorgi24 demonstrated conduction disturbances which we would classify as left anterior hemiblock after partial transection of the bundle of His in the area of insertion of the septal leaflet of the 900 ARAVINDAKSHAN ET AL. Downloaded from http://circ.ahajournals.org/ by guest on April 29, 2017 Figure 5 Serial sections of the conducction system in a normal human heart. The diagram at bottom right shows the level of sections 1 to 5; the solid black indicates the A-V node, bundle of His, main LBB, and the thin anterior division and thicker posterior division. The parallel interrutpted lines correspond to the RBB. (1) The arrow points to the penetrating portion of the bundle within the central fibrous body. (2) Branching portion (upper arrow). The fibers given off toward the left (left arrow) correspond to the posterior part of the LBB. On the right, insertion of the septal leaflet of the tricuspid valve. (3) Pseudobifurcation of the bundle of His into the RBB and most anterior part of the LBB, just atop the summit of the muscular septum. (4) Terminal part of the pseudobifurcation. (5) Distal portion of the RBB. tricuspid valve (fig. 3A and 3B of reference 24). The site of injury in these canine experiments23'24 was comparable to those in our surgical cases, and thus the work of Sciacca and Sangiorgi24 supports our thesis that left anterior hemiblock was caused by a central lesion in our cases. It has been suggested that fibers destined to form the RBB and LBB are already differentiated in the lower third of the bundle of His.23-23 This early differentiation and a lesion of the main bundle need not be invoked to explain RBBB and left anterior hemiblock in our cases since both fascicles have a short common pathway where a localized lesion (site 3', fig. 6) would cause RBBB and left anterior hemiblock. Injury to the distal portion of the anterior division of the left bundle is unlikely to have been the cause of left anterior hemiblock in our cases. Conduction disturbances were a common and significant complication of tricuspid valve replacement even in our retrospective study in which the true increase was probably underestimated because complete ECGs were not always available early in the postoperative period. C:rculation, Volume XL11! Nov ember 1970 RBBB AND LEFT ANTERIOR FASCICULAR BLOCK Downloaded from http://circ.ahajournals.org/ by guest on April 29, 2017 Figure 6 Diagriammatic representation of the conduction sysand the five sites which may be injured durinig tricuspid valve replacement. A lesion at 1 will callse monofascicuilar complete heart block with a n2arrotw QRS complex; at 2, complete heart block with a wide 3', RBBB w;ith left anterior QRS complex; at 3 tem or hemiblock; at 4, RBBB alone, and at 5, left hemiblock alone. For fturther descr iption T insertion of the septal leaflet of the anterior see text. tricuspid valve. It may be argued that injury of the conduction system was associated with aortic or mitral valve replacement and not tricuspid valve replacement. Conduction disturbances as a result of mitral valve replacement alone are virtually unknown. A high incidence of complete A-V block was repo rted in the early experience of aortic valve replacement.28 Subsequently, the incidence diminished because of improved appreciation of the relationships of the bundle of His to the commissure between the right coronary and noncoronary aortic cusps. In two of our five cases in which RBBB and left anterior hemiblock occurred, the aortic valve also had been replaced, and it is possible that left anterior hemiblock resulted from the trauma of this procedure. In the two cases in which both mitral and tricuspid valves were replaced, and in the case in which only the tricuspid valve was replaced, it is hard to conceive that RBBB and left anterior hemiblock resulted from anything other than Circulation, Volume XLII, November 1970 901 direct injury of the conduction system during tricuspid valve replacement. Complete A-V block produced at the time of surgery adversely affects the surgical result. Block of the RBB alone or in combination with block of the anterior division of the LBB causes no immediate concern, but the longterm prognosis has yet to be determined. Left anterior hemiblock and RBBB may lead, in time, to complete A-V block.7'17 22, 27, 28 This progression has not been documented in surgical RBBB with left anterior hemiblock, but total dependence of A-V conduction upon the posterior division of the LBB may increase the risk of complete heart block in later life. Therefore, surgical attention should be directed not only to the avoidance of damage to the main bundle, but also the right bundle and left anterior division. Acknowledgment The authors gratefully acknowledge the helpful critical review of the manuscript by Drs. Ralph Shabetai and Leonard Gettes. References 1. REEMTSMA K, DELGADO JP, CRiEEcH 0 JR: Heart block following intracardiac surgery: Localization of conduction tissuie injury. J Thorac Cardiovasc Surg 39: 688, 1960 2. GADBOYS HL, LITWAK RS: Experimental and clinical aspects of surgical heart block. Progr Cardiovasc Dis 6: 566, 1964 3. MCGOON DC, ONGLEY PA, KIRKLIN JW: Surgical heart block. Amer J Med 37: 749, 1964 4. HUDSON REB: Surgical pathology of the conducting system of the heart. Brit Heart J 29: 646, 1967 5. Trrus JL, DAUGHERTY GW, KIRKLIN JW, ET AL: Lesions of the atrio-ventricular conducting system after repair of ventricular septal defect. Relation to heart block. Circulation 28: 82, 1963 JJ, HALLIDIE-SNSITH KA: Conduction disturbances before and after surgical closure of ventricular septal defect. Amer Heart J 77: 123, 1969 7. ROSENBAUM MB, ELIZARI MV, LAZZARI JO: Los Hemibloqueos. Buenos Aires, Ed. Paidos, 6. KULBERTUS HE, COYNE 1968 8. ROSENBAUM MB: Types of left buindle branch block and their clinical significance. J Electrocardiol 2: 197, 1969 ARAVINDAKSHAN ET AL. 902 9. ROSENBAUM MB, ELIZARI MV, LEVI RJ, ET AL: 10. 1 1. 12. 13. Downloaded from http://circ.ahajournals.org/ by guest on April 29, 2017 14. 15. 16. 17. 18. Five cases of intermittent left anterior hemiblock. Amer J Cardiol 23: 1, 1969 ROSENBAUM MB, CoRRADO G, OLIVERI R, ET AL: Right bundle branch block with left anterior hemiblock surgically induced in tetralogy of Fallot: Relationship to the mechanism of the electrocardiographic changes in endocardial cushion defects. Amer J Cardiol 26: 12, 1970 BARNARD CN, ScHRIRE V: Surgical correction of Ebstein's malformation with prosthetic tricuspid valve. Surgery 54: 302, 1963 STARR A, HERR R, WOOD J: Tricuspid replacement for acquired valve disease. Surg Gynec Obstet 122: 1295, 1966 GANNON PG, GRONDIN C, MOLINA E, ET AL: Tricuspid valve replacement in rheumatic valvular disease and Ebstein's malformation: Clinical experience with 34 cases. (Abst) Amer J Cardiol 21: 98, 1968 MACRUZ R, TRANCHESI J, EBAID M, ET AL: Ebstein's disease: Electrovectorcardiographic and radiologic correlations. Amer J Cardiol 21: 653, 1968 SHABETAI R, ARAVINDAKSHAN V, DANIELSON G, ET AL: Traumatic hemopericardium with tricuspid incompetence. J Thorac Cardiovasc Surg 57: 296, 1969 ROSENBAUM MB: Types of right bundle branch block and their clinical significance. J Electrocardiol 1: 221, 1968 ROSENBAUM MB, ELIZARI MV, LAZZARI JO: The Hemiblocks: New Concepts of Intraventricular Conduction Based on Human Anatomical, Physiological and Clinical Studies. Tampa Tracings, In Press LEV M, WDRAN J, ERICKSON EE: A method for the histopathologic study of the atrioventricular node, bundle and bundle branches in the human heart. Circulation 4: 863, 1951 19. LEV M: Anatomic basis for atrio-ventricular block. Amer J Med 37: 742, 1964 20. WIDRAN J, LEV M: Dissection of the atrioventricular node, bundle and bundle branches in the human heart. Circulation 4: 863, 1951 21. HUDSON REB: The human conducting system and its examination. J Clin Path 16: 492, 1963 22. ROSENBAUM MB, ELIZARI MV, KRETZ A, ET AL: Anatomical basis of A-V conduction disturbances. Geriatrics. In Press 23. CONDORELLI L: Schenkelblock durch Lasion des Tawaraknotens. Verh Deutsch Ges Kreislaufforsch 5: 292, 1932 24. SCIACCA A, SANGIORGI M: Trouble de la conduction intraventriculaire droit du a la lesion du tronc commun du faisceau de His (etude experimentale). Acta Cardiol 12: 486, 1957 25. WATT TB JR, WILLIAMS E, JONES MJ, ET AL: Focal block clues to the functional anatomy of the His bundle. (Abstr) J Electrocardiol 2: 218, 1969 26. GANNON PG, SELLERS RD, KANJUH VI, ET AL: Complete heart block following replacement of the aortic valve. Circulation 33 (suppl I): I152, 1966 27. LASSER RP, HAFT JI, FRIEDBERG CK: Relationship of right bundle branch-block and marked left axis deviation (with left parietal or periinfarction block) to complete heart block and syncope. Circulation 37: 429, 1968 28. ROTHFELD EL, ZUCKER IR, Tiu R, ET AL: The electrocardiographic syndrome of superior axis and right bundle branch block. Dis Chest 55: 306, 1969 Circulation, Volume XLII, November 1970 Right Bundle-Branch Block and Left Anterior Fascicular Block (Left Anterior Hemiblock) Following Tricuspid Valve Replacement V. ARAVINDAKSHAN, MARCELO V. ELIZARI and MAURICIO B. ROSENBAUM Downloaded from http://circ.ahajournals.org/ by guest on April 29, 2017 Circulation. 1970;42:895-902 doi: 10.1161/01.CIR.42.5.895 Circulation is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231 Copyright © 1970 American Heart Association, Inc. All rights reserved. Print ISSN: 0009-7322. 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