The Electrocardiogram in Ventricular Septal Defect

Abstract

One hundred and nineteen cases of ventricular septal defect in infancy and childhood have been reviewed, with special reference to the electrocardiogram. The changes in the electrocardiogram were related to the hemodynamics found at cardiac catheterization, and particularly the pulmonary to systemic blood flow ratios, pulmonary artery pressures, and oximetry. They were also studied in relation to the groups of cases that obviously had a low pulmonary vascular resistance with or without diastolic loading of the left ventricle. Survival of a patient following closure of the defect with a drop in pulmonary artery pressure was also taken as a sign that the pulmonary vascular resistance was not excessive. The patients with clinical and hemodynamic evidence of a high pulmonary vascular resistance were also evaluated in relation to the electrocardiogram. The information obtained from the electrocardiogram may be graded according to degree of severity: (a) normal electrocardiogram, (b) left ventricular loading, (c) combined loading, (d) isolated right ventricular loading. These groups may be further graded depending on the diminishing number of signs listed below.^1-7 A detailed review of these four groups in relation to the following criteria may allow one to identify a low or only moderately raised pulmonary vascular resistance, or one that is sufficiently moderate to permit successful corrective surgery in the pediatric age group: 1. An R in V₆ over 20 mm. 2. A Q in V₆ of 4 mm. or over. 3. An S in V₁ over 25 mm. 4. A Q in V₆ of 2 mm. or more when associated with evidence of right ventricular loading. 5. An axis of less than 90°. 6. Counterclockwise vector. 7. Broad notched P waves in standard leads I or II, with late inversion in V₁. As a rule, several of these criteria occur together, but even if only one of them is present, one may conclude that the pulmonary vascular resistance is not excessive. Further support to this conclusion is evident if any of the above 7 items are accompanied by one or more of the following: (x) a pulmonary blood flow that is twice systemic, (y) an absence of reversal of flow through the defect either at rest or with exercise, (z) an age under 7 years. Among the 119 infants and children with ventricular septal defect, over 90 per cent appeared to have a sufficiently low pulmonary vascular resistance to be operable provided the surgical technic is adequate and provided complete heart block does not occur. Age appears to be an important factor in assessing the likelihood of success at surgery. Only an exceptional case shows hemodynamic findings indicating inoperability before the age of 7 years. During the first year of life many cases of ventricular septal defect have signs of left ventricular loading appear or increase, suggesting a favorable trend in the pulmonary vascular resistance. Until surgical technic makes operation more readily feasible in infancy, the optimum age of correction would appear to be between 2 and 7 years.