Evaluation of Ventricular Tachycardia with Respect to Syncope in Patients with Old Myocardial Infarction, Dilated Cardiomyopathy and No Overt Heart Disease : 53th Annual Scientific Session of the Japanese Circulation Society

The incidence and the direct cause of syncope in ventricular tachycardia (VT) among patients with old myocardial infarction (OMI, n = 48), dilated cardiomyopathy (DCM, n = 18) and no evidence of heart disease (IVT, n=43) were compared. The presence or absence of syncope in each patient was surveyed by a standardized questionaire and a variety of electrocardiographic parameters for aggravating arrhythmias were measured. Syncope occurred in 19 of 43 OMI patients (40%). in 5 of 18 DCM patients (28%) and 6 of 43 IVT patients (14%) and significantly more often in OMI than IVT (p<0.01). Ventricular fibrillation (VF) was confirmed in 14 of the 19 OMI patients with syncope, in 3 of the 5 DCM patients with syncope and 1 of 6 IVT patients with syncope. The incidence of VF was significantly higher in OMI than in IVT (p<0.01). Mean VT cycle lengths (VTRR'm) in OMI patients with and without syncope were 0.35±0.07 sec and 0.42±0.10 sec. respectively (p<0.05). VTRR'ms in DCM patients with and without syncope were 0._3±0.10 sec and 0.42±0.10 sec, respectivrly (NS). VTRR'ms in IVT patients with and without syncope were 0.27±0.04 sec and 0.41±0.10 sec, respectively (p<0.01). The results show that the high frequency of VT rate was the main cause of syncope in IVT. while VF was the main cause of syncope in OMI. There were no significant differences in the coupling interval, prematurity index, vulnerability index and QTc between groups with and without syncope in any of the underlying diseases. There were also no significant differences in the ejection fraction between the 2 groups. Therefore, it is considered that there is a diffrence in the direct cause of syncope between VT patients with OMI and IVT. Impaired ventricular function was not an important factor of syncope. Both VF and rapid VT are the main causes of syncope in OMI, while rapid VT is the main cause of syncope in IVT. This may be one of the reasons why IVT patients generally do not experience sudden cardiac death.