Pacing threshold spikes months and years after implant.

To determine patterns of variation in chronic pacing thresholds, we made 4,942 threshold measurements in 257 patients with 312 leads, at times from implant to 295 months (median 17 months) including 1,053 determinations in 46 children less than 12 years old. Motivation was late sudden death in two single-ventricle pacemaker-dependent children with multiple possible death causes. At stimulus duration 0.5 +/- 0.04 msec, mean of the thresholds, measured 1 month or more after implant, was 1.3 +/- 0.66 volts (V) for endocardial electrodes and 2.8 +/- 1.39 V for epicardially applied electrodes. Highest mean thresholds were in the 6 to 12-year-old age group. In 34 leads studied at implant, again within a month and for at least three years thereafter, time of maximum threshold occurred after one month in 59%, independent of lead type or patient age. Of 107 leads with five or more measurements after 3 months use, gradual increase in threshold continued after 3 months in 24%. An additional 21% had at least one threshold that exceeded the post-three-months individual patient lead mean by three standard deviations. Most striking was the occurrence of transient several-volt increases and decreases in threshold as late as 8 years after lead implantation in at least three children. These temporary changes were detected initially transtelephonically by the vario method of threshold measurement. They occurred during minor illnesses such as summer colds, yet similar illnesses also occurred without threshold elevation. We suggest further study of pacing threshold variations in highly pacemaker-dependent children whose cardiac anatomy makes use of epicardial electrodes necessary.

Corrective repair of complete atrioventricular canal defects and major associated cardiac anomalies.

Twenty-nine patients with balanced forms of complete atrioventricular (AV) canal defects and tetralogy of Fallot in 12, double-outlet right ventricle (DORV) in 10, and additional anomalies associated with atrial isomerism in 7 underwent corrective repair. Age ranged from 39 days to 24 years (median, 3.7 years). Repair included reconstruction of the common AV valve in 25 patients and prosthetic valve replacement in 4. Construction of an intraventricular tunnel connecting the left ventricle with the aorta was accomplished in 23 of 25 patients with ventriculoarterial concordant or double-outlet connections. In 2 patients with situs inversus and associated DORV and in 4 patients in the isomerism group who had ventriculoarterial discordant connections, repair included intraatrial venous diversion by a modified Senning procedure in 2, a modified Mustard venous switch in 1, and a tailored atrial baffle in 3. A valved extracardiac conduit was required for repair in 4 patients. Partial anomalous systemic venous connection was repaired in 7 patients and total anomalous pulmonary venous connection, in 5. There was 1 hospital death (3%) and 3 late deaths (11%). There was 1 (3.6%) reoperation to replace an incompetent right (systemic) AV valve 17 months postoperatively, and each of the 25 surviving patients was in New York Heart Association Functional Class I (80%) or II (20%) at follow-up.

Transatrial-transpulmonary repair of tetralogy of Fallot.

Classical tetralogy of Fallot was repaired by a transatrial-transpulmonary approach in 61 of 70 patients treated surgically on one surgical service between July 1981 and December 1985. Their ages ranged from 2.5 months to 57 years (mean 52.9 +/- 104.2 months). The ventricular septal defect was closed through the right atrium and tricuspid valve in 60 patients and via the pulmonary artery in one patient with a subpulmonary defect. A pulmonary arteriotomy was made in 38 patients to expose the stenotic pulmonary valve for valvotomy and to begin the infundibular mobilization and resection. It was extended through a small pulmonary anulus primarily in 15 patients and secondarily in one, a minimal distance upon the right ventricular infundibulum to enlarge the outflow tract to 2 standard deviations larger than the mean normal pulmonary valve anulus diameter. There were no hospital or late deaths or reoperations among the entire group. The mean postrepair peak right ventricular/left ventricular pressure measured in the operating room was 0.52 +/- 0.165 for the entire group of 61 patients which indicates similar relief of pulmonary stenosis to that obtained by the classical transventricular repair. At follow-up between 2.3 and 53.8 months (mean 22.6) each patient was in New York Heart Association Class I and without cardiac medication. Postoperative cardiac catheterization studies performed in nine patients between 4 and 28 months after operation showed no residual ventricular septal defects and a mean peak right/left ventricular pressure of 0.42 +/- 0.13. This series indicates that successful repair of tetralogy of Fallot can be accomplished in most patients by a transatrial-transpulmonary approach, which may provide improved right ventricular function over the long term.