Haemodynamic measurements prior to ventricular fibrillation or asystole following experimental coronary occlusion.

Dogs under general anaesthesia were studied following occlusion of a branch of the left circumflex artery produced by wedging a radio-opaque catheter under fluoroscopic control. In two dogs an aluminium-coated steel needle was lodged in place via the catheter. Pressures in the left atrium, left ventricle, pulmonary artery, and right atrium were recorded in nine dogs following this procedure, and in two of these serial cardiac outputs were determined. In four dogs the fatal dysrhythmia was preceded by bursts of ventricular rhythm disturbances without evidence of heart failure, and in one dog sudden fatal ventricular tachycardia occurred without any preceding warning. Flow measurements in one of these dogs showed no fall in output or stroke volume. In two dogs the left ventricular filling pressure gradually rose before the development of ventricular fibrillation. No change in output or stroke volume was shown in one of these dogs. Two dogs developed increasing ventricular irritability together with evidence of left ventricular failure, and in one dog, who was resuscitated from ventricular fibrillation, left ventricular failure leading to death occurred later the same day. Right atrial pressure was shown to be a misleading index of myocardial function, and the only evidence for impending acute circulatory embarrassment was increasing ventricular irritability.