The vectorcardiogram in cystic fibrosis. Diagnostic significance and correlation with pulmonary function tests.

One hundred and one children with cystic fibrosis had detailed studies of the vectorcardiograms and pulmonary function tests. The vectorcardiographic diagnoses were (1) right ventricular hypertrophy (14 patients), (2) right ventricular hypertrophv plus abnormally posterior vector (24 patients), (3) abnormally posterior vector (26 patients), (4) low voltage (nine patients), and (5) tracing within normal limits (35 patients). Right ventricular hypertrophy correlated well with a decreased vital capacity. Abnormally posterior vector correlated well with increased residual volume and functional residual capacity. The presence of the abnormally posterior vector was demonstrated to be the major factor in the difficulty in interpreting right ventricular hypertrophy from the electrocardiogram, for a large terminal rightward vector was often too far posterior to be registered as a terminal R in the right chest leads. The Frank system vectorcardiogram was demonstrated to be better able to detect right ventricular hypertrophy than was the cube system vectorcardiogram. This was particularly true in the presence of an abnormally posterior vector. An abnormally leftward 0.01-second vector, if it is anterior, is frequently seen in right ventricular hypertrophy.