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Background: Rhythm disturbances are frequent after Fontan operations. Arrhythmias related to reduced heart rate variability (HRV) have been described in various cardiovascular diseases., Methods: We attempted to investigate HRV in 12 patients who underwent Fontan operation (age 11.4 +/- 3 years). Results were compared to a control group of 13 children matched for age, sex and heart rate (10.4 +/- 3 years). All patients underwent 24-hour Holter monitoring. The following time domain indexes were calculated: mean duration of RR intervals, standard deviation of all RR intervals (SD), square root of the mean squared differences of successive RR intervals (r-MSSD), percentage of differences between adjacent RR intervals > 50 msec (pNN50). The following frequency domain indexes were calculated: total power (TP), low frequency (LF), high frequency (HF), LF/HF ratio., Results: The following indexes were significantly reduced in Fontan patients: SD (p < 0.0001), r-MSSD (p < 0.0001), pNN50 (p = 0.0002), TP (p < 0.0001), LF (p < 0.0001), HF (p = 0.0001). LF/HF increased significantly (p = 0.04). No differences were detected according to the type of operation (cavopulmonary connection vs atriopulmonary connection) or clinical status., Conclusions: Patients with Fontan circulation had a significantly reduced HRV and particularly abnormal sympatho-vagal balance. Surgery on the caval veins and the atria alters the intracardiac ganglia that are abundant at the cavo-atrial junction and in the myocardium of the right atrium. Abnormalities of HRV in Fontan patients may act as a co-factor in the initiation of arrhythmia in these patients.

A normal lung is supplied by a pulmonary artery branching from the pulmonary trunk. Major aorto-pulmonary collateral arteries (MAPCAs) are found in combination with various congenital heart malformations such as pulmonary atresia with ventricular septal defect (PA-VSD). Now that MAPCAs are used for unifocalization in patients with PA-VSD, the question arises as to whether the morphologic criteria of these collateral arteries could help to provide better results. We compared the morphology of the pulmonary vascular bed, the origin, course and connections of the MAPCAs in 40 consecutive infants with PA-VSD with or without 22q deletion (del22q11.2.). All underwent echocardiographic evaluation and catheterization. Identification of del22q11.2. was performed by FISH study. Del22q11.2. was identified in 16 pts (40%); the presence of MAPCAs was significantly higher in patients with del22q11.2. (9/16 vs 3/24, p = 0.01). While complex morphology of MAPCAs, anastomoses with the central pulmonary artery outside the lung and absent ductus arteriosus were associated with del22q11.2, confluence of the pulmonary arteries was not a relevant phenotypic difference. The size of the right and left pulmonary arteries expressed as a standard deviation difference of the normal range for body surface area was -4.2 (quartiles -3.1/-1.8) for PA-VSD with del22q11.2. and -2.6 (quartiles -5.3/-2.9) for PA-VSD without del22q11.2. (p = 0.02). The difference between measured and theoretical Nakata index was -373 +/- 94 for PA-VSD with del22q11.2. vs. -245 +/- 93 for PA-VSD without del22q11.2. (p = 0.0002). A specific pulmonary vascular bed phenotype could be defined in patients with PA-VSD with del22q11.2. deletion: MAPCAs with complex loop morphology and small but confluent central pulmonary arteries. These findings indicate a different timing of the faulty development pathway of the pulmonary vascular bed in patients with and without del22q11.2. This phenotype difference may help our understanding of maldevelopment and facilitate decisions concerning the suitability of these arteries for unifocalization procedures.