Cor pulmonale in cystic fibrosis.

A VCG and an orthogonal ECG were done on 66 ambulatory patients with cystic fibrosis. Arteriolized pO2, FEV1/VC and MBC were related to electrocardiographic measurements. In this group of adolescent and young adult patients the most helpful electrocardiographic sign of cor pulmonale is a low voltage representing the left ventricle. The four best indicators from the cardiogram are (1) Rx less than .8 mv; (2) Rx/Sx less than 4.0; (3) Tx less than .4 mv; and (4) MLVF + MLVH less than 2.5 mv. If more than one indicator is found cor pulmonale is likely present. Increased voltage over the right ventricle does not identify patients with cor pulmonale.