Traumatic heart block and tachyarrhythmia induced by right ventricular impact

The effect of direct impact on the right ventricle was investigated in an anesthetized open-chest canine preparation. At each of five impact sites, direct local loading produced immediate ventricular asystole followed by varying degrees of AV conduction block, lasting 70 +/- 35 seconds. Sinus rhythm temporarily resumed in most cases for 30 +/- 25 seconds before ventricular tachycardia abruptly intervened for 150 +/- 70 seconds. Recovery to sinus rhythm usually followed the ventricular tachycardia. Impact over the ventricular aspect supplied by the right coronary artery above the conduction bundle branches caused a longer period of asystole than impact over other sites. The duration of the delayed tachyarrhythmia was independent of impact site. Denervation of the heart did not influence the conduction block or the tachyarrhythmia. Intravenous injection of propranolol (1.6 mg/kg) did not affect the immediate conduction block but prevented the ventricular tachycardia.