Cardiothoracic Ratio as an Index of Natural Course of Isolated Ventricular Septal Defect

The cardiothoracic ratio (CTR) in patients with isolated ventricular septal defect (VSD) decreases with increasing age. This relationship with age is of a second degree polynomial and goes best with logarithm of age, and is statistically very significant. Thirty-three % of the total variation of CTR in VSD is explained only by the age factor. The decrease of CTR before age 2 is 2.4 %per year, while it decreases to 0.39 % per year after age 2. This significant decrease in CTR is an index showing the decrease in left to right shunt, and was observed in all hemodynamic classes. The presented regressions of CTR with age give insight to the expected decrease of CTR as well as to the degree of left to right shunt, thereby serving as a practical method in the indication for surgical closure.