Vectorcardiographic Changes During Intracoronary Injections

To determine mechanisms of myocardial toxicity of radiopaque media and to correlate specifically induced changes in the composition of coronary artery blood with changes in the surface electrocardiogram, simultaneous recordings were made from Frank leads X, Y, and Z during intracoronary injections of radiopaque media and special test solutions. The study group consisted of 19 patients, 29 to 64 years of age, with either abnormal or normal-appearing coronary vessels on cineangiography. Recordings were analyzed with an electronic integrator, an oscilloscope, and directly from photographic tracings.With injections of sodium-containing radiopaque media into the right coronary system, the spatial mean T vector increased in magnitude and deviated to the left and superiorly. With injections into the left coronary system, the T vector increased in magnitude and shifted to the right, downward, and anteriorly. Changes in the QRS complex were less constant but, when present, consisted of slight prolongation of the QRS duration and shift of the QRS vector toward the area of myocardium perfused by the coronary system injected.Similar T-vector changes could be produced by intracoronary injections of saline solutions, but minimal or no changes were observed with injections of hypertonic mannitol, Ringer's solution, hypoxic blood, plasma, and 5% dextrose in water.It is concluded that the T-wave changes are caused by regional prolongation of the repolarization process, presumably due to extracellular sodium excess or sodium-calcium antagonism. Delay of the repolarization process and the resulting potential difference may be responsible for re-entrant excitation and the ventricular arrhythmias observed during coronary angiography.