The revolution in molecular genetics is contributing to the understanding of normal and abnormal cardiovascular development and morphogenesis. Recent investigations have shown that a growing number of congenital heart malformations is due to single gene defects. The combined contribution of clinical and molecular studies is providing the chromosomal map of the genes related to these isolated cardiac defects, and to syndromes characteristically associated with specific cardiac malformations. These advances are relevant to clinical practice, since the accumulated knowledge can improve the quality of management of affected patients.

All infants and children born alive with documented congenital heart disease (excluding those weighing less than 2500 g at birth with a diagnosis of patent arterial duct) within the county of Merseyside between 1979 and 1988 were identified from the combined records of the Liverpool Congenital Malformations Registry and the Cardiac Unit, Royal Liverpool Children‘s Hospital Alder Hey, Liverpool. In total, 1543 cases were disclosed from a live-birth population of 203,880 providing a prevalence rate at birth of 7.57 (95% confidence interval: 7.20–7.96) cases per 1000 livebirths. The overall crude death rate was 18.5% (95% confidence interval: 16.4–20.3). An additional 240 (15.6% [95% confidence interval: 13.8–17.5%]) cases of heart disease not identified by the registry were disclosed from the records of the cardiac unit, demonstrating the unreliability of rates published by monitoring bodies. The annual prevalence rate at birth varied from 6.3 to 9.0 per 1000 livebirths, and seemed to be associated with the impact of new imaging technology. Regional variation was marked (5.3 to 8.9 per 1000 livebirths) and unaccountable in terms of potential morphogenetic mechanism, suggesting inconsistencies in referral of cases. Exclusion of regions of poor ascertainment in the calculation of a revised figure for the prevalence rate at birth suggests that as many as 89 in every 10,000 infants born alive may have structural cardiac anomalies. In conclusion, annual and regional variation of ascertainment in registry studies remains the enemy of an accurate description of the true prevalence rate at birth for congenital heart disease.

Although ventricular septal defect is the most common form of congenital heart disease, its epidemiology is not completely understood. The Baltimore-Washington Infant Study, a case-control study of congenital cardiovascular malformations, enrolled 4,390 case infants during the study period 1981–1989. Ventricular septal defect, the most common malformation, was present in 1,465 (33%) of affected infants. The purpose of this report was to describe the epidemiological characteristics of membranous and muscular ventricular septal defects, the most common types of ventricular septal defects. Membranous ventricular septal defects (n=895) and muscular ventricular septal defects (n=429) accounted for 90% of all ventricular defects. During the study, prevalence increased from 0.9 to 2.1 /1000 live births. Associated non-cardiac defects, such as chromosomal defects, genetic syndromes, and defects of other organs were more common among infants with ventricular septal defect than among control infants, and more common among infants with membranous ventricular defect (20.8%) than among those with muscular defects (7.5%). Infants with ventricular septal defects and non-cardiac defects had increased mortality in comparison to infants with isolated ventricular septal defects or controls. Epidemiological information derived from population-based studies provide valuable data for counseling families and may allow for examination of etiologic factors.

Between 1981 and 1990, 765 symptomatic neonates with major congenital heart malformations were admitted into the Grantham Hospital. This represented an incidence of 10 per 10,000 live births for Hong Kong. The figure was comparable to those reported for Caucasians. Among the 744 Oriental neonates, obstruction of the pulmonary outflow tract occurred most frequently (281, 37.8%), followed by left ventricular outflow tract obstruction (169, 22.7%), left-to-right shunting (115, 15.5%), complete transposition (92, 12.4%), common mixing situations (62,8.3%), and miscellaneous causes (25, 3.3%). When compared with the available reports from the West, Chinese neonates had a high preference for pulmonary outflow tract obstruction (p<0.005), especially the anomaly of pulmonary atresia and intact ventricular septum. This correlated well with cyanosis as the commonest neonatal presentation (64%). Contrary to previous reports that aortic coarctation was rare among Orientals, this abnormality was observed frequently in our study. The rare occurrence of critical aortic valvar stenosis among Chinese, however, was supported by our present analysis. Other lesions, such as left-to-right shunting and complete transposition, showed no significant racial difference in the frequency of occurrence. Such knowledge concerning the pattern of congenital heart disease amongst Oriental neonates can facilitate early diagnosis and timely referral of babies to the appropriate center for management.

The arterial switch operation is the treatment of choice for complete transposition, and for the Taussig-Bing anomaly, with good early and mid-term results. This retrospective study examined the findings obtained at routine follow-up cardiac catheterization after primary arterial switch repair. We catheterized 111 patients after a mean of 16.9 months after surgery. These included 67 patients with an intact ventricular septum, 33 with a ventricular septal defect, and 11 with the Taussig-Bing anomaly. Right ventricular pressures were mildly elevated (mean 33.9±10.2 mm Hg) in the overall group with a mean pressure ratio between right and left ventricles of 0.34±0.1. Of the patients 74% had gradients across the right ventricular outflow tract of under 20 mm Hg, while three (2.7%) had gradients over 30 mm Hg. A significant gradient across the left ventricular outflow tract occurred in one patient (0.9%), while significant neo-aortic stenosis was not seen. The neo-aortic root remained dilated, with mild aortic valvar incompetence being seen in 12%, with none having higher grades of regurgitation. Left ventricular ejection fraction was normal in all patients, while left ventricular end-diastolic pressure was elevated in 38%. Coronary arterial stenosis was not seen, but one patient (0.9%) had left ventricular apical dyskinesia. Overall, therefore, we conclude that cardiac hemodynamics and ventricular systolic function after primary arterial switch are good. Minor gradients to the pulmonary arteries, and mild neo-aortic valvar incompetence were commonly noted. Left ventricular end-diastolic pressure was elevated in over a third of the patients. These subclinical and subtle abnormalities warrant ongoing follow-up to determine their long-term significance.

Adenosine, when given as an intravenous bolus, has been shown to produce atrioventricular nodal block in humans. To examine the effect of adenosine on conduction across both accessory pathways and the atrioventricular node in children, we reviewed our experience with adenosine administered during both atrial and ventricular pacing in 42 patients with atrioventricular resting tachycardia and in eight patients with atrioventricular nodal reentry tachycardia. Adenosine was administered as a mean bolus of 195 μg/kg/dose during both atrial and ventricular pacing, examining antegrade and retrograde conduction before and after radiofrequency ablation. In those patients with persistent or intermittent pre-excitation, anomalous ventricular activation was either unchanged (n=8) or increased (n=11). Retrograde conduction (either through the accessory pathway alone in three, or across both the accessory pathway and the atrioventricular node in 19) persisted in 92% of the 24 patients studied. Adenosine produced either first or third degree antegrade heart block in all patients studied without pre-excitation (those with either dual atrioventricular nodal pathways or concealed accessory pathways). Adenosine produced retrograde block in all of the eight patients with dual atrioventricular nodal pathways. In contrast, retrograde conduction persisted in 82% (14/17) of patients with concealed accessory pathways (p=0.001). When used to examine retrograde conduction, adenosine was a sensitive (82%) and highly specific (producing retrograde atrioventricular block in all patients with dual atrioventricular nodal pathways) predictor of tachycardia supported by a concealed accessory pathway. Adenosine yielded a sensitivity and specificity of 96% and a positive predictive value of 99.5% for the success of ablation of accessory pathways. These data indicate that the pattern of adenosine-induced changes in either antegrade or retrograde atrioventricular conduction, or conduction in both directions, in young patients with supraventricular tachycardia is related to the mechanism of the tachycardia. Adenosine, therefore, is a useful adjunct in the electrophysiologic evaluation of supraventricular tachycardia in children.

Second degree atrioventricular block is uncommon in children. In order to evaluate its outcome, and to find early prognostic factors, we reviewed the history and evolution of 21 children with this arrhythmia discovered on their surface electrocardiogram. Twenty-four-hour monitoring displayed variations in the conduction patterns in almost all children, from long PR interval to complete heart block alternating in the same patient. At follow-up (nine months to 19 years), 13 children (62%) had received implantation of a pacemaker because of progression either to complete atrioventricular block or to severe ventricular bradycardia. Atrioventricular conduction improved on exercise in 11 children, but this did not predict a favorable outcome since four of them required pacing. In contrast, deterioration during sinus acceleration in four patients predicted further aggravation. A supra-Hisian location of the block did not protect against the occurrence of syncope in the two patients who underwent His recordings. Finally, the outcome was not linked to age at diagnosis. Second degree atrioventricular block, therefore, should be considered a serious disease because of its trend to worsen towards complete block and/or severe complications. Close follow-up, including repeated 24-hour monitoring, is the most effective way to unmask such a progression and to avoid its clinical consequences.

Implantation of the Rashkind double umbrella device for closure of the persistently patent arterial duct is now routine in many units. The use of this device in non-ductal positions, however, has been reported in only a limited number of patients, and its impact on the subsequent clinical course has not been established. A retrospective review of all such occlusions, therefore, was undertaken to address the early results and impact on clinical management. From 9/1988 through 2/1994, implantation of a double umbrella device was attempted in 21 patients (eight female, 13 male) with cardiovascular communications other than a persistent arterial duct excluding the intentional fenestrations made in the modified Fontan procedure. Median age at implantation was 2.6 years (three months-12.4 years) and weight was 11.6 kg (4.1–45) kg. Lesions included four ventricular septal defects, an aortopulmonary window, an aortopulmonary collateral artery, an atrial septal defect, four Gore-tex® shunts, and a residual persistent communication between the superior caval vein and the right atrium following either a bidirectional cavopulmonary anastomosis, or a classical Glenn operation. Eight patients underwent occlusion of unintentional residual right-to-left (six) or left-to-right (two) communications following the Fontan procedure. Implantation was accomplished in all without mortality, utilizing either 12 mm (13) or 17 mm (eight) devices. Surgical removal of the device was required in one patient four weeks subsequent to implantation. At latest follow-up (1–66 months, median four months), color-flow Doppler studies revealed complete occlusion in 17 (77%) patients. Implantation of the double umbrella in sites other than the duct is, therefore, feasible and simplified technically with a modification of the delivery system. Such novel applications of transcatheter intervention using double umbrella devices may avoid or complement subsequent surgery.

In recent years, the percutaneous closure of small and medium-sized patent arterial ducts has been achieved using occluding spring coils. We describe our experience in 33 patients with this technique using a snare to facilitate the procedure. All patients had a clinically apparent patent arterial duct and underwent an attempt at transcatheter closure at a mean age of 5.6 years. In one patient, the duct was a residual lesion following surgical ligation, and in three was residual following attempted closure with a Rashkind double-umbrella. The mean narrowest diameter of the ducts was 1.9 mm. The coil embolized in two of the first four patients, and subsequent to that experience we used a snare to improve delivery. Of the 33 patients, implantation was successful in 32 (97%) using one [29 patients] or two [two patients] coils and in one by a combination of a double-umbrella device and an occluding spring coil. The mean fluoroscopic screening time for the whole group was 26.5 minutes, this time decreasing to 18.5 minutes in the last 26 patients [p <0.05]. Color-Doppler echocardiogram performed the morning after placement of the coils has shown residual leaks in nine of 32 patients [28%]. At a mean follow-up of 7.6 months, repeated imaging has shown residual leaks in four of these patients [12.5%]. No patient had a residual continuous murmur immediately following occlusion. Based on our results, we conclude that occlusion of small to medium-sized ducts using coils appears to be effective. The use of a snare to hold and manipulate the coil as it is delivered improves both control of the coil and the accuracy of its placement.

Percutaneous transcatheter embolization of the arterial duct, using new detachable coils, was performed in 19 patients aged from two to 16 years. The minimal ductal diameter ranged from 0.5 to 2.7 mm. We used a 5 mm diameter coil, 8 cm in length and/or an 8 mm diameter coil, which was 10 cm in length. The coil was connected to a delivery wire with a screw system, and could be detached by rotation of the delivery wire. The coil was straightened by inserting a mandril, with loops then being formed by withdrawal of the mandril. In all patients, the coil was advanced retrogradely and either one or two coils were successfully implanted. Implantation was performed in four patients without the catheter entering the pulmonary trunk across the arterial duct. The ductal ampulla was either absent or very small in five patients, so we implanted a coil which had been cut short. Angiography revealed no residual shunting in 14 patients (74%) and trace residual shunting in five patients. Migration of the coils to the pulmonary arteries, or to a systemic artery, did not occur in any patient. Follow-up using Doppler color flow imaging showed complete closure of the arterial duct in all patients (100%), and no turbulence either in the left pulmonary artery or in the descending aorta in any patient. The use of the new detachable coil may improve the accuracy of placement of the device and reduce the incidence of its migration.

We report the case of an infant who developed severe cardiac compromise due to hypertrophic obstructive cardiomyopathy that developed while he was being treated with dexamethasone for bronchopulmonary dysplasia. This case is illustrative, as previous reports have described steroid-induced hypertrophic obstructive cardiomyopathy as being transient and benign. In this infant, the hypertrophic obstructive cardiomyopathy, waxed, waned, waxed, and waned again during two courses of dexamethasone, thus strengthening a causal link with steroid therapy. A high index of suspicion of hypertrophic obstructive cardiomyopathy as the etiology of hypoperfusion in steroid-treated infants with bronchopulmonary dysplasia is important. Serial echocardiographic monitoring of these infants is helpful in identifying cardiac compromise.

The case of a 27-year-old male with Ebstein's malformation combined with a ventricular septal defect is reported. On its right ventricular side the defect was covered by the dysplastic septal tricuspid leaflet, creating a small chamber in continuity with the left ventricle, but without shunt into the remaining components of the right ventricle. The ventricular septal defect and a patent oval foramen were closed operatively after a cerebral embolic event to eliminate probable sources of thromboemboli preventing the inherent risks of life-long anticoagulation for a young patient. Intraoperative morphology confirmed the preoperative findings.