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  IN THIS Article
 ::  Abstract
 ::  Introduction
 ::  Case report
 ::  Discussion
 ::  Acknowledgment
 ::  References

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Year : 1991  |  Volume : 37  |  Issue : 1  |  Page : 58-61

Congenital intermittent atrio-ventricular dissociation in tetralogy of Fallot (a case report).

Department of Paediatrics, K.E.M. Hospital, Parel, Bombay, Maharashtra.

Correspondence Address:
Department of Paediatrics, K.E.M. Hospital, Parel, Bombay, Maharashtra.

  ::  Abstract

A case of tetralogy of fallot with congenital intermittent atrioventricular dissociation is reported. A review of standard postgraduate books of cardiology fails to describe this condition, thus showing its extreme rarity. The therapeutic dilemma in treating such a case is also discussed.

How to cite this article:
Karande S C, Sheth S S, Dalvi B V, Lahiri K, Shah M D. Congenital intermittent atrio-ventricular dissociation in tetralogy of Fallot (a case report). J Postgrad Med 1991;37:58-61

How to cite this URL:
Karande S C, Sheth S S, Dalvi B V, Lahiri K, Shah M D. Congenital intermittent atrio-ventricular dissociation in tetralogy of Fallot (a case report). J Postgrad Med [serial online] 1991 [cited 2023 Jun 5];37:58-61. Available from:

  ::   Introduction Top

Congenital heart disease occurs in 0.8% of all five births. Tetralogy of Fallot (TOF) accounts for 10% of all forms of congenital heart disease and is the most common cardiac malformation responsible for cyanosis after one year of age[3]. Frequency of congenital complete heart block is about 4 per 10,000 births [8]. This case report describes an unusual association of TOF with atrio-ventricular (AV) dissociation.

  ::   Case report Top

A 7-year-old girl was brought with complaints of cyanosis since the age of 1 year, and repeated squatting episodes for the last 3 years. She had no syncopeal attacks or symptoms suggestive of congestive cardiac failure. There was no history of recent mumps, diphtheria or rheumatic fever. She was on no medication at the time of presentation. Her birth history and milestones were normal.
On examination, her pulse was found to be irregular with a rate of 52/min. Her other vital parameters were normal. She had central cyanosis and grade III clubbing. Jugular venous pulse showed intermittent cannon waves. Cardiovascular examination revealed a left para-sternal bulge, a well felt apex beat in the 4th left intercostal space in the mid-clavicular line and a grade 4/6 ejection systolic murmur in the pulmonary area with a single second heart sound.
Hematological and biochemical investigations were normal. Anti- streptolysin O titre was not significant. X-ray chest showed a cardiothoracic ratio of 60% with a right aortic arch and pulmonary oligemia. ECG showed varying P-P and R-R intervals suggestive of intermittent sinus arrests with transient A-V dissociation. At other times, normally conducted sinus beats were seen. P wave axis was +45?, QRS. axis was +110?, with evidence of right ventricular hypertrophy and QRS transition in lead V2. The duration of the QRS. complex was less than 80 msec (See [Figure:1] and [Figure:2]).
Two dimensional echocardiogram revealed a large subaortic ventricular septal defect with 50% aortic override and Mitral aortic continuity. There was evidence of subvalvular and valvular pulmonary stenosis with good sized main pulmonary artery and its branches. Cardiac Catheterization confirmed the 2 echo findings.
The child was not given propranolol in view of the A-V dissociation. She was advised early complete surgical repair of TOF with pacemaker implantation.

  ::   Discussion Top

TOF with congential A-V dissociation has not been reported. The ventricular septal defect (VSD) in TOF is large, about the size of the aortic orifice and it lies beneath the aortic valve, more anteriorly than the usual VSD[5]. The pathway of the bundle of His in tetralogy patients has been reported in detail by Feldt et al[2] The main bundle is closely related to the poster- inferior margin of the defect. It runs along its inferior margin, on the left side of the summit of the ventricular septum. Hence, conduction disturbances both transient and permanent, including complete A-V block, can occur after corrective surgery[4]. Permanent complete heart block following surgery is treated by implanting a pacemaker.
Congenital A-V block is probably the result of defect in the main stem of the bundle of His[1]. Seventy per cent cases have no other evidence of heart disease. Associated cardiac malformations include "corrected" transposition of the great arteries, common AV canal, endocardial fibroelastosis, single ventricle, and patent ductus arteriosus. Isolated VSD is seldom associated with complete heart block[1]. Temporary heart block is seen with mumps, diphtheria, rheumatic fever and drugs, such as, digoxin or quinidine. The commonest acquired cause of complete heart block in childhood is post-operative, especially following a repair of VSD or TOF. Most of the congenital complete A-V blocks are asymptomatic. The ventricular rate is usually 45 to 60/min, and mean age for recognition is 4.9 years[6]. However, if heart rate falls below 40/min, dizziness, syncopeal attacks and congestive cardiac failure can occur. Since congenital complete heart block is most often of suprahisian variety[8], the ORS complexes in the ECG are narrow as seen in our case. It requires no treatment, unless syncope or unremitting congestive cardiac failure develops.
Ponce et al[7] have said that propranolol is useful to prevent or reduce the frequency of cyanotic spells if corrective surgery has to be delayed for any reason, such as a poor socio-economic status, which is, more often than not, a rule in our country. In our case, propranolol could not be used to control cyanotic episodes since it would have worsened the bradycardia and heart block. Thus, early corrective surgery for TOF with pacemaker implantation becomes mandatory in spite of various financial constraints. Fortunately, this child was 7 years old and early corrective surgery was available. But at a very young age, when total correction is not possible at many centres in our country, such a situation can cause a therapeutic dilemma. ? blockers with intrinsic sympathomimetic activity (e.g. oxprenolol, pindolol, alprenolol) may be the best alternative under such circumstances.

  ::   Acknowledgment Top

We thank the Dean, King Edward Memorial Hospital and Seth GS Medical College for allowing us to publish this case report.

  ::   References Top

1. Behrman RE, Vaughan VC, Nelson WE. Disturbances of rate and rhythm of the heart. In: "Nelson Textbook of Pediatrics". 13th Edition. Philadelphia: WB Saunders Company; 1987, pp 1004-1010.  Back to cited text no. 1    
2.Feldt RH, DuShane JW, Titus JL. The anatomy of the atrioventricular conduction systcm in ventricular septal defect and tetralogy of Fallot: correlations with the electrocardiogram and vectorcardiogram. Circulation 1966; 34:774-782.  Back to cited text no. 2    
3.Friedman WF. In: "Heart Disease. A Text-book of Cardiovascular Medicine." Editor: E. Braunwald, 3rd Edition, Philadelphia: WB Saunders Company; 1988, pp 946-948.  Back to cited text no. 3    
4.Fryda RJ, Kaplan S, Helmsworth JA. Post-operative complete heart block in children. Brit Heart J 1971; 33:456-462.  Back to cited text no. 4    
5.Jordan SC, Scott O. In: "Heart Disease in Pediatrics". 2nd Edition. London: Butterworths; 1981, pp 159-169.  Back to cited text no. 5    
6.Olley PM. In: "Heart Disease in Infancy and Childhood". JD Keith, RD Rowe, P. Vlad, editors. 3rd Edition, New York: Macmillan Publishing Co. Inc.; 1978, pp 289-292.  Back to cited text no. 6    
7.Ponce FE, Williams LC, Webb HM, Riopel DA, Hohn AR. Propranolol palliation of Tetralogy of Fallot: experience with long-term drug treatment in Pediatric patients. Pediatrics 1973; 52:100-108.  Back to cited text no. 7    
8.Roberts N, Gelband H. Arrhythmias. In: "Heart Disease in Infants, Children and Adolescents". AJ Moss, FH Adams GC, editors. Emmanouilides, 2nd Edition. Baltimore: The Williams and Wilkins Company; 1977, pp 676-693.   Back to cited text no. 8    

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Online since 12th February '04
2004 - Journal of Postgraduate Medicine
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