Conventional and right precordial ECGs, creatine kinase, and radionuclide angiography in post-traumatic ventricular dysfunction

Right ventricular infarction due to ischemic heart disease can be diagnosed by a right precordial electrogram or by first-pass radionuclide angiography (FPRNA). Prior FPRNA studies have shown that cardiac dysfunction after blunt chest trauma (myocardial contusion) is most often due to right ventricular dysfunction. We hypothesized that right ventricular dysfunction due to ischemic heart disease and myocardial contusion should produce similar ECG changes due to myocyte disruption. The purpose of our study was to evaluate the diagnostic value of the right precordial electrogram in suspected cardiac contusion. Thirty-five patients with suspected myocardial contusion based on mechanism of injury/clinical findings and no history of clinical heart disease were enrolled prospectively. All patients had conventional ECG, right precordial electrogram, and FPRNA studies. Twenty patients had normal cardiac scans (group 1); percentage of myocardial creatine kinase (CK-MB) was measured in 12 of these patients and was less than 5% in 11. Fifteen patients had abnormal cardiac scans (wall motion abnormality and/or decreased right ventricular ejection fraction) (mean, 34% ± 7% [SD]; normal, > 40%) (group 2); percentage of CK-MB was measured in 13 of 15 patients and was less than 5% in all 13. Conventional ECGs and right precordial electrograms in all patients were analyzed for differences in heart rate, PR interval, QRS duration, corrected QT interval, and the axis of the frontal and horizontal plane QRS complex and ST segment. There were no significant differences between group 1 and group 2 patients. No patient with myocardial contusion diagnosed by FPRNA had elevated ST segments in V4R through V6R or a percentage CK-MB of more than 5%. We conclude that in suspected myocardial contusion, the surface ECG, including right precordial leads, and CK-MB determinations are of no diagnostic value. The absence of ECG (potassium leakage) and CK-MB changes (CK leakage), despite evidence of right ventricular dysfunction after contusion, suggests that myocardial dysfunction is not the result of cellular injury/membrane disruption. Right ventricular dysfunction may be due to mechanical “stunning” of the myocardium and not myocyte injury and biochemical stunning as documented in ischemic heart disease.