Giuliano Bosi

Prevalence of the Congenital Long-QT Syndrome

Background— The prevalence of genetic arrhythmogenic diseases is unknown. For the long-QT syndrome (LQTS), figures ranging from 1:20 000 to 1:5000 were published, but none was based on actual data. Our objective was to define the prevalence of LQTS. Methods and Results— In 18 maternity hospitals, an ECG was performed in 44 596 infants 15 to 25 days old (43 080 whites). In infants with a corrected QT interval (QTc) >450 ms, the ECG was repeated within 1 to 2 weeks. Genetic analysis, by screening 7 LQTS genes, was performed in 28 of 31 (90%) and in 14 of 28 infants (50%) with, respectively, a QTc >470 ms or between 461 and 470 ms. A QTc of 451 to 460, 461 to 470, and >470 ms was observed in 177 (0.41%), 28 (0.06%), and 31 infants (0.07%). Among genotyped infants, disease-causing mutations were found in 12 of 28 (43%) with a QTc >470 ms and in 4 of 14 (29%) with a QTc of 461 to 470 ms. One genotype-negative infant (QTc 482 ms) was diagnosed as affected by LQTS on clinical grounds. Among family members of genotype-positive infants, 51% were found to carry disease-causing mutations. In total, 17 of 43 080 white infants were affected by LQTS, demonstrating a prevalence of at least 1:2534 apparently healthy live births (95% confidence interval, 1:1583 to 1:4350). Conclusions— This study provides the first data-based estimate of the prevalence of LQTS among whites. On the basis of the nongenotyped infants with QTc between 451 and 470 ms, we advance the hypothesis that this prevalence might be close to 1:2000. ECG-guided molecular screening can identify most infants affected by LQTS and unmask affected relatives, thus allowing effective preventive measures.

A Novel Form of Short QT Syndrome (SQT3) Is Caused by a Mutation in the KCNJ2 Gene

Short QT syndrome (SQTS) leads to an abbreviated QTc interval and predisposes patients to life-threatening arrhythmias. To date, two forms of the disease have been identified: SQT1, caused by a gain of function substitution in the HERG (IKr) channel, and SQT2, caused by a gain of function substitution in the KvLQT1 (IKs) channel. Here we identify a new variant, “SQT3”, which has a unique ECG phenotype characterized by asymmetrical T waves, and a defect in the gene coding for the inwardly rectifying Kir2.1 (IK1) channel. The affected members of a single family had a G514A substitution in the KCNJ2 gene that resulted in a change from aspartic acid to asparagine at position 172 (D172N). Whole-cell patch-clamp studies of the heterologously expressed human D172N channel demonstrated a larger outward IK1 than the wild-type (P<0.05) at potentials between −75 mV and −45 mV, with the peak current being shifted in the former with respect to the latter (WT, −75 mV; D172N, −65 mV). Coexpression of WT and mutant channels to mimic the heterozygous condition of the proband yielded an outward current that was intermediate between WT and D172N. In computer simulations using a human ventricular myocyte model the increased outward IK1 greatly accelerated the final phase of repolarization, and shortened the action potential duration. Hence, unlike the known mutations in the two other SQTS forms (N588K in HERG and V307L in KvLQT1), simulations using the D172N and WT/D172N mutations fully accounted for the ECG phenotype of tall and asymmetrically shaped T waves. Although we were unable to test for inducibility of arrhythmia susceptibility due to lack of patients’ consent, our computer simulations predict a steeper steady-state restitution curve for the D172N and WT/D172N mutation, compared with WT or to HERG or KvLQT1 mutations, which may predispose SQT3 patients to a greater risk of reentrant arrhythmias.

The natural history of cardiac rhabdomyoma with and without tuberous sclerosis

The aim of the present study is to contribute to the knowledge of the natural history of cardiac rhabdomyoma in children with and without tuberous sclerosis. In a retrospective study, 33 children with cardiac rhabdomyoma were collected from three pediatric cardiology centres. In 30/33 patients tuberous sclerosis was associated. High prevalence of cardiac rhabdomyoma was found in infancy, with 21/23 detected before the age of 1 year, and 11/33 before 1 month of age. Cardiac manifestations were present in 19 patients: cardiac rhythm disturbances were detected in 13; in 6/33 a Wolff‐Parkinson‐White syndrome was documented, of which 4 presented paroxysmal arrhythmias. Obstructive or regurgitative phenomena were present in 5; and in 2 patients surgical removal proved necessary. With the exception of one tumoural mass in the right atrium, all 77 tumours were located somewhere in the ventricles, including at atrioventricular valve level. Because of spontaneous regression of most of the tumoural masses, treatment should at first be symptomatic, while surgical removal is required only in life‐threatening conditions, as documented in 2 of our 33 patients.

Are gender differences in QTc present at birth

The analysis of 9,725 electrocardiograms recorded on the fourth day of life has shown that gender-related differences in QTc observed in the adult population are not present at birth.

The Italian Multicentric Study on Epidemiology of Congenital Heart Disease: first step of the analysis

We present the aims, methodology and initial results from the Italian Multicentric Study for the registration and follow-up of congenital heart disease. The general aims are to measure the prevalence of congenital heart disease in different geographic areas of Italy, and to assess the survival and outcome of affected babies. During the years 1992 and 1993, eighteen centers for Pediatric Cardiology spread all over the Country enrolled 1445 new babies with congenital cardiac malformations from a population of 341,647 surveyed livebirths. The new cases were registered using the same methodologic criteria of the EUROCAT study in order to evaluate differences and/or similarities between the studies. The prevalence varied between 1.8% and 8.1%; the average being 4.6%. The large range in prevalence is presumed to be related to different customs and hierarchies in flow and referral of patients. We provide total prevalence of individual lesions, and distribution of sentinel cardiac anomalies, in the Italian study and compare them with EUROCAT. Isolated ventricular septal defect is the most common lesion (39%); followed by atrial septal defect (7.5%); pulmonary valvar stenosis (7.3%); atrioventricular septal defects (5.4%); patency of the arterial duct (3.8%); complete transposition (3.7%); tetralogy of Fallot (3.3%); aortic coarctation (2.4%); aortic valvar stenosis (2.2%); and left heart hypoplasia (1.8%). The echographic stratification of ventricular and atrial septal defects, by location and size, was in keeping with the findings of the EUROCAT study. Because of the recent widespread availability of color-Doppler techniques, the stratification of aortic and pulmonary valvar stenosis was an innovative approach in our study. Among the complex cardiovascular anomalies, double inlet ventricle and pulmonary atresia had a proportion of about 2% each; with double outlet right ventricle, common arterial trunk, Ebsteins malformation, tricuspid atresia, interrupted aortic arch and totally anomalous pulmonary venous connection having a proportion ranging from 0.5 to 0.8%. We discuss clinical features, such as frequency of extracardiac anomalies and familial aggregation of congenital heart disease, in comparison with the EUROCAT data.

Doppler and 2D echocardiographic diagnosis of congenital coronary artery fistulae to the right cardiac chambers: Report of 3 cases

We present three cases of coronary artery fistulae to the right cardiac chambers. The first was a 2-day-old neonate in congestive heart failure: 2D and Doppler echocardiography revealed a dilated proximal left coronary artery and a fistulous connection to the right atrium. The other two patients, respectively 4 and 3 years old, were asymptomatic and presented with a continuous heart murmur: a left coronary artery fistula into the right ventricle was detected by ultrasound in one, and a dilated proximal right coronary artery in the other. The diagnosis was confirmed in all three patients. The first patient was operated upon at 18 months of age; the second patient is awaiting surgery, and in the third patient the fistula was ligated at the age of 3 years. The possibility of ultrasound diagnosis without invasive procedures is suggested.

Intrauterine supraventricular tachycardia with a familial history of Lown-Ganong-Levine syndrome

Familial occurrence of the preexcitation syndrome is thought to be uncommon . But reports of the Wolff-Parkinson-White (WPW) syndrome in two or more members of the same family have raised the Possibility of autosontat dominant inheritance [7] . Nevertheless, the exact move of inheritance is unknown and a variable expressivity of the syndrome has been postulated [3] . In 1982, Chia et al . [2] rePorted the singular coexistence of difference preexcitation syndromes in one family : a WPW pattern in the father and in three of his six sons, and the Lown_Ganong-Levine (LGL : short PR interval with normal QRS complex) syndrome in the daughter . We here report a similar occurrence, further supporting the variable expressivity of this condition .