ARRHYTHMOGENIC RIGHT VENTRICULAR DYSPLASIA: A CLINICAL MODEL FOR THE STUDY OF CHRONIC VENTRICULAR TACHYCARDIA

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Arrhythmogenic right ventricular dysplasia (ARVD) is a recently individualised clinical entity which sometimes presents with episodes of ventricular tachycardia (VT). These attacks may be resistant to anti-arrhythmic therapy and new therapeutic approaches have been developed for the treatment of this condition. These new methods are mainly surgical, based on the analysis of electrical activation of the heart in sinus rhythm and during VT. This approach has increased our understanding of the physiophathology of VT, not only in the context of ARVD, but also in the most commonly encountered clinical setting of VT, after myocardial infarction. Electrophysiological study of the epicardial activation of the dysplastic zones has demonstrated the presence of delayed potentials recorded after the end of the QRS complex. This can be explained by the histopathology of these issues. ARVD is characterised histologically by partial degeneration of the myocardial wall. Most of the muscle fibers are replaced by fatty tissue in the middle of which some healthy fibers survive. These changes are mainly observed in the intramyocardial and subepicardial layers, the subendocardium being almost normal. Strands of isolated muscle fibers within the non-conducting fatty degeneration may lead to very delayed activation with respect to the adjacent healthy tissues. The propagation of activation is delayed as it passes through this plexiform structure and in the zones adjacent to healthy muscle were reentry phenomena may arise. In ARVD, these changes are mainly located over the right ventricle, so explaining the right ventricular origin of most forms of VT observed in this condition. However, we have also observed a case which suggested an isolated arrhythmogenic left ventricular dyplasia. Epicardial mapping localizes the point of origin of VT in zones situated between the slow and normally conducting tissues. Simple ventriculotomy, a full thickness section of the ventricular wall, at the point of epicardial breakthrough of the VT prevents recurrence in the great majority of patients. The same pathophysiological concepts may be applied to VT complicating myocardial infarction but in this situation the myocardial fibers capable of slowly conducting the activation are isolated with in the fibrous tissue in the border zone of the infarct. The point of origin of VT is usually within the interventricular septum with a point of epicardial breakthrough which could be located some distance away. Different surgical techniques have been developed to deal with this condition. Encircling endocardial ventriculotomy isolates the arrhythmogenic zone from the rest of the healthy tissues by tracing an incision all around the arrhythmogenic border zone. Subendo-cardial excision could be performed at the point of origin of the abnormal activation. Cryoablation seems a less aggressive procedure. These new surgical techniques of managing resistant VT complicating myocardial infarction have given improved results by comparison with previous methods (aneurysm-ectomy, myocardial revascularization) which were not based on electrophy-siological concepts. More selective techniques like close chest ventricular tachycardia fulguration is a promising method currently on the way of development to manage recurrent VT of any etiology with minor damage to myocardial function.
社団法人日本循環器学会の論文
1984-06-20

ARRHYTHMOGENIC RIGHT VENTRICULAR DYSPLASIA: A CLINICAL MODEL FOR THE STUDY OF CHRONIC VENTRICULAR TACHYCARDIA

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