CONTROL OF VENTRICULAR RATE BY INTERATRIAL SEPTAL INCISION AND CRISTA-TERMINALIS MYOTOMY IN THE PATIENTS WITH ATRIAL-FIBRILLATION UNDERGOING MITRAL-VALVE REPLACEMENT

The aim of the study was to analyze the effect of surgical moderation of conduction from the atrium to the atrio-ventricular (AV) node on ve ntricular response in 30 patients with atrial fibrillation (AF) underg oing mitral valve replacement (MVR). Besides the usual diagnostics, ec hocardiographic evaluation of the size of the left atrium was performe d in all patients, as a parameter of stability of rhythm conversion by drugs. Surgical treatment was applied exclusively in cases where, jud ging by these parameters, there was little chance for drug treatment t o be effective. All patients (mean age 50 years) had severe mitral val ve disease (NYHA III and IV), chronic AF and irregular ventricular rat e, and underwent mitral valve replacement with mechanical valve. The p atients were divided into three groups of ten patients each. In group I: MVR was combined with interatrial septal incision (IASI) to study t he effect of the moderation of conduction from the interatrial septum to the AV node; in group II: after MVR, IASI was combined with crista terminalis myotomy (CTM) to study the additional effect of the moderat ion of conduction along the crista terminalis to the AV node; in group III (control): MVR was performed through left atriotomy, without anti arrhythmic incisions. Ventricular response was studied in two phases: In the immediate postoperative period (up to 7 days), using continuous electrocardiographic (ECG) monitoring, and 2 months postoperatively, using 24 h Holter monitoring with the results compared to a preoperati ve 24 h recording. Postoperative AF occurred in all patients. In the i mmediate postoperative period, IASI (group 1) produced a moderate vent ricular response, but a more profound effect was achieved when IASI wa s combined with CTM (group 2). Alteration of the conduction from atriu m to AV node, produced by the surgical division of two main atrionodal routes resulted in a slow ventricular response warranting temporary p acemaker support to the 7th postoperative day. In two patients nodoven tricular bradycardia still existed 2 months after surgery, necessitati ng ventricular rate response (VVIR) pacemaker implantation. Twenty-fou r hour Holter analyses performed 2 months postoperatively showed that IASI (group 1) no longer had any effect on the ventricular response. T he antiarrhythmic effect of IASI in producing a moderate ventricular r esponse in the immediate postoperative period was transitory only. Int eratrial septal incision combined with CTM had a prolonged antiarrhyth mic effect up to 2 months after the operation. With this procedure, po stoperative 24 h ventricular rate changes showed a smaller grade of os cillation, less irregularity and lower average values compared to a pr eoperative 24 h Holter study.