At the present time, the relatively high atrial stimulation threshold and the low and often unstable P wave amplitude are the main concerns in atrial pacing. As a further contribution to the solution of this problem we used a screw-in atrial lead in 16 patients. During the implantation, atrial mapping was performed in order to establish the position with the best electrical performance. The acute threshold for voltage at a pulse duration of 1 ms averaged 0.49 +/- 0.18 Volt. The acute peak-to-peak P wave amplitude averaged 4.6 mV +/- 1.3. No complication occurred at the time of the implantation. Follow-up periods averaged 12 months. No dislocation or bleeding was observed during a follow-up period of up to 28 months. Using this lead together with intraoperative atrial mapping, it is possible to achieve an acute strength-duration relationship in the atrium at a level similar to that in the ventricle. The results of this study demonstrate that intraoperative mapping is an important stein in enhancing the safety margins and long-term performance of atrial pacing.
From November 1977 to January 1981, 10 consecutive patients underwent intracardiac repair of the complete atrioventricular canal at our institution. Ages ranged from 14 months to 4.5 years (mean age 20 months). Four patients were predominantly of type A, while 6 were predominantly of type C according to Rastelli's classification. Three patients had associated cardiac anomalies (2 tetralogy of Fallot and one parachute mitral valve). Standard repair and correction of the associated anomalies were performed under cold cardioplegic cardiac arrest and deep hypothermia with low-flow perfusion or circulatory arrest. Two patients died early postoperatively in severe renal failure and one died 6.5 months postoperatively in cardiac failure due to progressive mitral valve incompetence. One patient, with parachute mitral valve, was reoperated and the mitral valve was replaced because of persistent mitral insufficiency. The patients were followed up for a period of 4 to 35 months (mean 14 months) with a total of 112 patient months. The result of the operation was very good and all patients with retarded growth curve preoperatively showed a marked acceleration of their growth curve after operation. The operative results in this group of patients are independent of age and weight at the time of operation but appear to be influenced by associated cardiac anomalies and by the quality and quantity of atrioventricular valve tissue available for reconstruction.
Electrode fracture is a serious late complication of pacemaker implantation. This complication was observed in 33 patients within 3 years whereby the interval between electrode implantation and fracture was on average 35 (12--113) months. The cause lay partly in the electrodes themselves--in all cases singly wound spiral electrodes--and partly in technical deficiencies in the extrathoracic loop formation. Attention is drawn to the fact that fracture has never occurred in the Elema electrode type 588 used routinely by the authors.
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