Severe type of ventricular arrhythmia was noticed after Cabrol's operation more frequently than usual reperfusion arrhythmia. Nine patients received Cabrol's operation and 2 of Bentall's were divided into 2 groups according to the occurrence of postsurgical ventricular arrhythmia (Lown's classification grade 0-3: 5 cases, grade 4 A-5: 6 cases), and then the factors contributed to the arrhythmia were analyzed. There were no significant differences between the 2 groups on the point of the characteristics of the cases with or without emergent surgery for, such as ruptured or dissecting thoracic aortic aneurysms or other complicated lesions, the degree of surgical damage, or preoperative cardiac function. The only significant difference between the groups was the angle overheading to the central point of left coronary orifice anastomosed with intermediate tube from the extensive line of the prosthetic flange obtained in the left anterior oblique views on the angiography. The mean value of the angle of the severe group (grade 4 A-5) was 41 +/- 6.8 degrees (mean +/- SD) and significantly acute than the angle of the other group (grade 0-3: 57 +/- 6.4 degrees). This fact suggested that the main reason of the ventricular arrhythmia was coronary ischemia caused by compression of the intermediate tube after formation of massive hematoma within the aneurysmal capsule wrapped over the composite graft.