Vectorcardiographic manifestations of experimental right ventricular necrosis

This study was carried out to evaluate the possible usefulness of the VCG in the diagnosis of right ventricular necrosis. Myocardial necrosis was produced by injecting 40% formalin into the ventricular walls of 21 open-chest mongrel dogs. The injections were made in the inferior wall of the left ventricle in eight dogs (Group A) and in the inferior wall of the right ventricle in 13 dogs (Group B). Analysis of vectorcardiographic QRS loops obtained before and two hours after the injections revealed that both left and right ventricular necrosis resulted in a decrease in: maximum inferior amplitude, inferior amplitude at 10 and 20 msec. and maximum frontal plane angle. In Group A, six dogs had counterclockwise initial forces in the frontal plane before the injections and these became clockwise following the injections. In Group B, nine dogs had counterclockwise initial forces in the frontal plane before the injections and these remained counterclockwise following the injections. The only consistent QRS change in scalar ECGs that occurred after the injections was the development of small Q waves in the six dogs in Group A that manifested clockwise initial forces in the frontal plane. The VCG performed in serial fashion may be more sensitive than the 12 lead ECG for detecting right ventricular inferior wall necrosis in the experimental animal. Application of these findings to the diagnosis of myocardial infarction in humans requires further investigation.