How pacemakers work and simple programming: a primer for the non-electrophysiologist.

Paediatric pacemaker management is challenging because of the small patient size, complex cardiac anatomy, and unique programming considerations. Hardware placement options include epicardial and transvenous systems. When pacemaker malfunction is suspected, a systematic approach is required to determine whether there is malfunction in pacing, sensing, or no output due to hardware problem. In most cases, simple reprogramming may circumvent the problem and allow retention of the pacemaker system.

Postnatal recurrence and transesophageal inducibility of prenatally treated fetal supraventricular tachycardia.

BACKGROUND: Antiarrhythmic treatment of fetal supraventricular tachycardia (SVT) is used to prevent morbidity and mortality. The postnatal management of survivors is often arbitrary and varied. OBJECTIVE: The purpose of this study was to examine the utility of a risk-based postnatal management strategy. METHODS: Sixty-six prenatally treated newborns with fetal long or short ventriculoatrial tachycardia were reviewed. Postnatal diagnoses included atrioventricular reentrant tachycardia, atrial ectopic tachycardia, and permanent junctional reciprocating tachycardia. Unless SVT persisted to birth, early neonatal observation without treatment was recommended. For newborns without spontaneous arrhythmia after ≥2 days of observation, inducibility was tested by transesophageal pacing study (TEPS). Postnatal therapy was advised for spontaneous or inducible SVT. Characteristics associated with these outcomes were analyzed. RESULTS: Twenty-eight patients (42%) experienced SVT at or early after birth, which was associated with fetal long ventriculoatrial tachycardia (odds ratio [OR] 6.8; 95% confidence interval [CI] 1.88-24.57; P = .0029); delayed in utero cardioversion with treatment (median 11 days vs 5.5 days; P < .0001); prenatal treatment with multiple antiarrhythmics (OR 4.42; 95% CI 1.56-12.55; P = .0059); and postnatal atrial ectopic tachycardia/permanent junctional reciprocating (OR 18.0; 95% CI 2.11-153.9; P = .0013). Of the 38 neonates undergoing TEPS, 19 (50%) had inducible tachyarrhythmias. Recurrence of SVT during infancy or childhood was documented in 4 of 6 patients with SVT at birth (66%), 8 of 22 patients with early neonatal SVT (36%), 4 of 19 patients with inducible SVT (21%), and 0 of 19 untreated patients without inducible SVT (0%) (P = .0032). CONCLUSION: The postnatal risk of SVT is related to the arrhythmia mechanism and prenatal treatment response. In newborns without spontaneous SVT, TEPS may be useful to guide the need for postnatal treatment on the basis of SVT inducibility.

QT hysteresis in long-QT syndrome children with exercise testing.

BACKGROUND: Congenital long QT syndrome (LQTS) is an inherited ion channel disorder resulting in abnormal cardiac repolarization that can cause syncope and sudden death associated with a prolonged rate-corrected QT interval and polymorphic ventricular tachycardia. Several studies in adults showed that LQTS patients have altered QT adaptation to heart rate changes compared with normal subjects which forming a "hysteresis loop" in the QT-circle length plot. This study was to observe the QT interval changing during exercise testing in children long QT syndrome (LQTS) patients, explore the new diagnosis methods of LQTS. METHODS: The subjects were divided into 3 groups according to 1993 LQTS diagnostic criteria. Group 1: LQTS group (n = 17) who scored > or = 4 points indicating definite LQTS. Group 2: Middle group (n = 16), patients who have prolonged QT interval but scored 1.5 to 3.5. Group 3: Normal control group (n = 18). The average age of all study population is (12.3 +/- 5.8) years. No case had beta-adrenergic antagonists administration before exercise testing. All subjects were underwent tread mill exercise testing and electrocardiograph in whole exercise testing and recovery were recorded. QT and heart rate changing during whole exercise testing period were recorded. DeltaQT, the QT interval at 1, 2, 4, 6 minutes into recovery subtract from the QT interval at a similar heart rate during exercise, were calculated. RESULTS: In all three groups, QT intervals were shortening with the increasing of heart rate, but QTc had no significant change. DeltaQT at 1 minute ((45 +/- 11) ms), 2 minutes ((37 +/- 15) ms), 4 minutes ((23 +/- 12) ms) into recovery in LQTS group were significantly greater than that of the other two groups (P < 0.05, P < 0.01, P < 0.01, respectively). There was no DeltaQT significant difference between middle group and normal control group at recovery time. During the recovery phase in LQTS group, the QT interval remained shortened despite a decelerating heart rate, forming a hysteresis "loop" in the curve relating the QT interval to the cycle length. CONCLUSIONS: In children LQTS patients, there is significant QT hysteresis loop in the relation of QT interval with heart rate during recovery of exercise testing, which could be useful to the early diagnosis for LQTS.

Hemodynamic effects of sustained postoperative cardiac resynchronization therapy in infants after repair of congenital heart disease: Results of a randomized clinical trial.

BACKGROUND: It is unknown whether continuous cardiac resynchronization therapy (CRT) can lead to sustained improvement in hemodynamics after surgery for congenital heart disease (CHD). OBJECTIVE: We investigated whether CRT improves cardiac index (CI) and blood pressure in infants after biventricular repair of CHD. METHODS: We randomized infants younger than 4 months after biventricular CHD surgery to standard care or standard care plus CRT for 48 hours or until extubation if sooner. Change in the primary outcome of CI and blood pressure over time was compared between groups. For subgroup analysis, QRS duration was considered prolonged if greater than the 98th percentile. RESULTS: Forty-two patients were randomized: 21 controls and 21 patients receiving CRT (median weight 4 kg). There were no identified adverse events from pacing. The change in CI over time was not different between patients receiving CRT and controls, but trended toward improvement in patients with wide QRS who received CRT (n = 9) vs controls with wide QRS (n = 8) (+1.65 (0.86) L/(min·m2); P = .06). Controls with wide QRS experienced the smallest increase in CI (0.33 L/(min·m2)). Blood pressure was significantly higher in infants with wide QRS who received CRT than in controls (+7.14 (3.08) mm Hg; P = .02). Serum lactate level, catecholamine use, ventilation time, and length of intensive care unit stay were similar between the 2 groups. CONCLUSION: CRT improved blood pressure and a trend toward higher CI in infants after repair of biventricular CHD with prolonged QRS duration. These findings warrant further study of CRT to improve postoperative recovery in infants with electrical dyssynchrony.