Potential additional indicators for pacemaker requirement in isolated congenital atrioventricular block.

Low heart rate is the predominantly used indication for pacemaker intervention in patients with isolated congenital atrioventricular block (CAVB). The aim of this study was to compare the difference in heart rates recorded with ECG and Holter monitoring between paced (PM) and nonpaced (NPM) patients with isolated CAVB before pacemaker implantation to identify additional predictors for future PM need. Retrospective evaluation of atrial and ventricular rates (electrocardiography) and minimal and maximal (Holter) heart rates in 129 CAVB patients prior to PM implantation (n = 93) was performed, and results are expressed in V adjusted for age and sex. The average V score for the atrial rate was 0.51 (n = 50) in the PM group and 0.60 (n = 22) in the NPM group (not-significant). The average z score for the ventricular (average) rate was -0.91 (n = 83) in the PM group and -0.93 (n = 33) in the NPM group (not-significant). Minimal heart rate was -0.94 (n = 61) in the PM group and -0.86 (n = 25) in the NPM group (not significant). Maximal heart rate was -0.96 (n = 61) in the PM group and -0.95 (n = 26) in the NPM group (not significant). Initial recordings of the average heart rate and the minimal and maximal heart rate recorded during Holter monitoring do not seem to predict future pacemaker need in patients with CAVB. Studies with exercise stress tests are needed to confirm these findings.

Endocardial and epicardial steroid lead pacing in the neonatal and paediatric age group.

AIM: To compare the performance of steroid eluting epicardial and endocardial leads in infants and children requiring permanent pacing. METHODS: Evaluation of pacing and sensing characteristics, impedances, and longevity of 159 steroid eluting leads implanted in 95 children. Group A consisted of 24 children weighing less than 15 kg with 15 endocardial leads (five atrial, 10 ventricular) and 19 epicardial leads (five atrial, 14 ventricular). Group B consisted of 71 children weighing more than 15 kg with 106 endocardial leads (56 atrial, 58 ventricular) and 19 epicardial leads (nine atrial, 10 ventricular). RESULTS: Group A: Stimulation thresholds were lower for ventricular endocardial leads at implant (mean (SD) 0.84 (0.54) v 1.59 (0.64) V, p < 0.014) and at two year follow up (ventricular 0.64 (0.24) v 1.65 (0.69) V, p < 0.003). Impedance and sensing thresholds did not differ significantly at implant and follow up. Group B: Stimulation thresholds were lower for ventricular endocardial leads at implant (0.72 (0.48) v 1.48 (0.58) V, p < 0.001) and at follow up (0.88 (0.46) v 1.55 (0.96) V, p < 0.009). Impedance did not differ. Sensing thresholds were also better for ventricular endocardial leads at follow up (9.1 (5.2) v 14.2 (6.4) mV, p < 0.02). Complications requiring intervention occurred in both groups (n = 7 for endocardial v n = 18 for epicardial leads). CONCLUSIONS: Endocardial and epicardial steroid eluting leads have comparable performance in the paediatric population.

Preterm infants with paroxysmal supraventricular tachycardia: presentation, response to therapy, and outcome.

OBJECTIVES: We investigated the clinical course of preterm infants with paroxysmal supraventricular tachycardia in comparison to their term counterparts. BACKGROUND: Paroxysmal supraventricular tachycardia (PSVT) is the most common arrhythmia in childhood. It is known to cause significant morbidity and rarely mortality, most commonly in infants. Yet, there is minimal information in the literature on preterm infants with PSVT. METHODS: Retrospective review of 40 infants, 26 term and 14 preterm, less than three months of age who presented with PSVT from January 1990 to January 1999. We compared the severity of first clinical presentation, in-hospital response to long-term medications, and outcome after discharge. RESULTS: Symptomatic severity on presentation was not different between preterm and term infants. Preterm infants required fewer medication trials (p=0.01) and had no recurrences after discharge in contrast with 43 % recurrence in the term infants (p<0.0001). No preterm infants had Wolff-Parkinson-White syndrome (WPW) in contrast to 42 % of term infants (p=0.003). Term infants with WPW were more symptomatic (p=0.01), required more medications (p=0.004), but had a similar recurrence frequency as terms infants without WPW (p=0.95). Excluding infants with WPW, preterm infants were more severely symptomatic (p=0.02), yet no longer was there a difference in response to first medication trial (p=0.30). CONCLUSIONS: We found that preterm infants with PSVT are as severely symptomatic on presentation, require fewer medications for adequate in-hospital control, and have fewer recurrences than their term counterparts. Unexpectedly, preterm infants did not present with WPW. The presence of WPW only in the term infants may account for differences in the clinical course between preterm and term infants.

Dilated cardiomyopathy in isolated congenital complete atrioventricular block: early and long-term risk in children.

OBJECTIVES: We sought to identify the risk factors predicting the development of dilated cardiomyopathy (DCM) in patients with isolated congenital complete atrioventricular block (CCAVB). BACKGROUND: Recently evidence has emerged that a subset of patients with CCAVB develop DCM. METHODS: This was a retrospective study of 149 patients with CCAVB who had heart size and left ventricular (LV) function assessed by echocardiography and chest radiography over a follow-up period of 10 +/- 7 years. RESULTS: Nine patients developed DCM at the age of 6.5 +/- 5 years. No definite cause could be identified. In these nine patients, CCAVB was diagnosed in eight at 23 +/- 2.3 weeks gestation and in one at birth. Maternal SSA/SSB antibodies were confirmed in seven of the nine patients. Pacemakers were implanted in eight patients in the first month and in one patient at five years of age. The initial left ventricular end-diastolic dimension (LVEDD) was in the 96th +/- 2.6 percentile and the cardiothoracic (CT) ratio was 64 +/- 3.8% in the nine patients who developed DCM, and differed significantly in patients with CCAVB (p < 0.005) who did not develop DCM. The LVEDD and CT ratio did not decrease in the patients with CCAVB and DCM, but decreased significantly in the patients with CCAVB without DCM (p < 0.001) once pacing was initiated. Two patients with DCM died within two months of diagnosis; one patient is neurologically compromised; two patients received a heart transplant; and four patients are listed for heart transplantation. CONCLUSIONS: Isolated CCAVB is associated with a long-term risk for the development of DCM. Risk factors may be SSA/SSB antibodies, increased heart size at initial evaluation and the absence of pacemaker-associated improvement.