Effects of simultaneous insertion of 66 plunge needle electrodes on myocardial activation, function, and structure

Transmural recordings using plunge needle electrodes are useful in mapping ventricular tachyarrhythmia, but they interfere with activation sequences or damage the myocardium. This study evaluated the effects of insertion of 66 transmural needles on myocardial activation, structure, and function. Epicardial maps were performed at thoracotomy using a 40-electrode plaque in five mongrel dogs. Sixty-six transmural plunge needles were introduced into the anterior aspect of the septum and left ventricle. Transmural maps of unipolar electrograms were recorded every 15 minutes via 124 electrodes over a 2-hour period. Epicardial maps were repeated after the needles were removed. All recordings were performed during sinus rhythm and ventricular pacing at 300- and 200-ms cycle lengths. Gated heart pool studies were performed preoperatively and 2 weeks after thoracotomy. Programmed ventricular stimulation was performed 2 weeks after thoracotomy. In total, 15,996 electrograms were analyzed. Maximum negative dV/dt of each electrogram and the activation time at each electrode did not change significantly over the 2 hours of needle insertion. After removal of the needles, epicardial maps were unchanged compared to before needle insertion. Mean left ventricular ejection fraction 2 weeks after needle insertion was 59% versus 58% before needle insertion (P=0.9). No dogs had inducible ventricular tachycardia. Histology showed contraction bands of 0.8-mm diameter adjacent to the needle tracks but no scarring. Insertion of 66 closely spaced plunge needles did not distort epicardial or transmural maps. Multiple needles did not result in myocardial scarring, left ventricular dysfunction, or predispose to ventricular tachycardia.