[Anti-tachycardia surgery in ventricular arrhythmia]

Abstract

Recurrent sustained ventricular tachycardia (VT) is associated predominantly with ischemic heart disease, mostly in the chronic phase after myocardial infarction. Potentially life-threatening and drug-refractory ventricular tachycardias are called malignant VT. In the Federal Republic of Germany, VT develops in about 3,000 to 5,000 patients per year from the 100,000 who survive a myocardial infarction. About 10% of these patients prove to be medically-refractory or additionally are considered candidates for aneurysmectomy or coronary revascularization. Overall, for the Federal Republic of Germany, there is a need for approximately 500 to 1000 antitachycardia operations each year. The morphologic substrate for malignant VT are ischemically-damaged inhomogeneously-structured arrhythmogenic areas. The morphology results in electrical inhomogeneity which predisposes to electrophysiologic reentry phenomena. NATURAL HISTORY: The survival rate of patients with malignant VT who are not surgically treated is 70% at one year and 20 to 40% at four years (Figure 1). In those in whom the tachycardia can be medically controlled, the prognosis is 10.5 times more favorable than in those with medically-refractory arrhythmias. In one study of 45 patients with recurrent, sustained VT, only 20% of those with medical refractoriness were free of renewed arrhythmic events after 30 weeks as compared to 90% whose treatment had been designated effective (p less than 0.0004) (Figure 2). According to a further study, for patients with drug-refractory VT, the probability for sudden death within four years was 55% as compared with 5% for those with medically-controlled VT (p less than 0.0002).

Surgical treatment: The concept of surgical treatment of malignant VT encompasses delineation of the arrhythmogenic area by means of endocardial mapping and surgical ablation. Arrhythmogenic areas are located mostly in the transition zone between the viable muscle and an aneurysm at the left ventricular endomyocardial septum. With mapping, by means of local measurements of activity times, impulse spread throughout the heart can be recorded in a cartographic system. The left ventricular endocardial activation should be determined during sinus rhythm and tachycardia and, with normothermic extracorporeal circulation the left ventricle is incised, mostly in the aneurysmatic antero-apical area, prior to sequential interrogation of the endocardial surface (Figure 3). As an alternative to point-for-point mapping, by means of multi-terminal electrodes, electrocardiograms can be obtained simultaneously from multiple positions. During tachycardia, the earliest activation can be found in the arrhythmogenic area (Figure 4); during sinus rhythm, in these areas, delayed, low-amplitude and fragmented signals are present (Figure 5). Macroscopically, endomyocardial fibrosis is a common finding. The arrhythmogenic morphologic substrate is either reduced or rendered a homogeneous scar without electrical activity. In this regard, techniques for endomyocardial resection have been described by Harken and Josephson. As an alternative procedure. Guiraudon introduced the encircling endomyocardial resection with which the pathologic reentry circuit can be blocked and the microvascular blood flow to arrhythmogenic areas eliminated. One modification, the partial encircling resection, appears to yield comparable effectiveness with less damage to left ventricular function (Figure 6).(ABSTRACT TRUNCATED AT 400 WORDS)