ELECTROCARDIOGRAPHIC CHANGES IN A.S.D.

Abstract

INTRODUCTION:
Among the congenital heart diseases atrial septal defect is the best known, readily recognised, easily and safely correctable anomaly, with left to right shunt at the atrial level. The right ventricle is subjected to volume overload, resulti ng in characteristic electrocardiographic and echocardiographic patterns. The appearance of R in VI in thought to be due to the delayed activat ion of the hypertrophied crista supraventricularis, while complete RBBB is due to a conduction defect in the Right bundle itself. We have studied the QRS duration in thirty six cases of documen— ted secondum A.S.D. and the progression ofQRS duration appears to be an ageing phenomenon.

MATERIAL AND METHODS:

Since February 1975 ninety six patients were studied and operated for A.S.D. in the National Institute of Cardiovascula Diseases, Karachi. Out of these cases the records of eighty two. were available for study. All patients had Cathet erization via Rt. Ante-cubital vein cutdown. Buhi’s type of defect in the membranous septum above the attachment of the tricuspid valve without leaflet fenestration resulting in direct left ventricular Rt. atrial communication.

RESULTS:
Table No. 1 shows the age and sex distribut ion of these cases. •Thirty eight were males and fbrty four were females. The mean age for males was 21 2 and for females it was 21 .4 years. The youngest patient was 6 years old arid eldest was 47 years old. Complete RBBB was present when the duration of QRS was =0.12 seconds and lead VI showed rSR’ or RSR’ pattern and lead I showed broad S waves.

DISCUSSION:

While a patent foramen ovale is very comm only encountered during Cardiac Cath. especially when performed from the leg, it is usually haemo— dynamically insignificant until associated with raised pressure in either atrium. Larger defects in the interatrial septum result in significant left to right shunting and volume overload of Right ventricle. Five distinct anatomical types of atrial septal defects are known (Diagrams I-IV. The development of tall R in Vi has also been attributed to existence of significant pulm onary hypertension in A.S.D. Thus when pressure overload pattern is present in associat ion with A.S.D. then pulmonic stenosis or pulmonary hypertension may be present.