Screening for Rare Coding Variants That Associate With the QTc Interval in Iceland.

Background Long-QT syndrome (LQTS) is a cardiac repolarization abnormality that can lead to sudden cardiac death. The most common causes are rare coding variants in the genes KCNQ1, KCNH2, and SCN5A. The data on LQTS epidemiology are limited, and information on expressivity and penetrance of pathogenic variants is sparse. Methods and Results We screened for rare coding variants associated with the corrected QT (QTc) interval in Iceland. We explored the frequency of the identified variants, their penetrance, and their association with severe events. Twelve variants were associated with the QTc interval. Five in KCNQ1, 3 in KCNH2, 2 in cardiomyopathy genes MYBPC3 and PKP2, and 2 in genes where coding variants have not been associated with the QTc interval, ISOC1 and MYOM2. The combined carrier frequency of the 8 variants in the previously known LQTS genes was 530 per 100 000 individuals (1:190). p.Tyr315Cys and p.Leu273Phe in KCNQ1 were associated with having a mean QTc interval longer than 500 ms (P=4.2×10-7; odds ratio [OR], 38.6; P=8.4×10-10, OR, 26.5; respectively), and p.Leu273Phe was associated with sudden cardiac death (P=0.0034; OR, 2.99). p.Val215Met in KCNQ1 was carried by 1 in 280 Icelanders, had a smaller effect on the QTc interval (P=1.8×10-44; effect, 22.8 ms), and did not associate with severe clinical events. Conclusions The carrier frequency of associating variants in LQTS genes was higher than previous estimates of the prevalence of LQTS. The variants have variable effects on the QTc interval, and carriers of p.Tyr315Cys and p.Leu273Phe have a more severe disease than carriers of p.Val215Met. These data could lead to improved identification, risk stratification, and a more precise clinical approach to those with QTc prolongation.

Early cardiomyopathy without severe metabolic dysregulation in a patient with cblB-type methylmalonic acidemia.

BACKGROUND: Cardiomyopathy is a known complication of organic acidemias but generally thought to be secondary to poor metabolic control. METHODS: Our patient was found through biochemical testing and Sanger sequencing to harbor an Icelandic founder mutation: NM_052845.4(MMAB):c.571C > T(p.Arg191Trp), leading to an early presentation (4 h after birth) of cblB-type methylmalonic acidemia (MMA). Biochemical testing of this patient suggested B-12-responsiveness and thus the patient was treated with cyanocobalamin throughout life. Informed parental consent was obtained for this report. RESULTS: Our patient had three metabolic decompensations in her life (at birth, at 1 month, and at 5 months). The first decompensation was probably linked to stress of delivery, second to rhinovirus infection, and third by co-infection of norovirus and enterovirus. At 3 months, the patient was noted to be tachypneic, although this was attributed to her underlying metabolic acidosis. At 5 months and 10 days, the patient was admitted with minor flu-like symptoms but developed severe diarrhea in hospital and upon rehydration had cardiac decompensation and was found to have undiagnosed dilated cardiomyopathy. Although, patient was treated aggressively with dextrose, hemodialysis, levocarnitine, and vasoactive agents, there was limited response to medications to treat cardiac failure, and eventually the patient passed away before turning 6 months old. CONCLUSIONS: Other than these three mild decompensations, patient had very good metabolic control, thus demonstrating that even without frequent metabolic decompensation, cardiomyopathy can be an observed phenotype in cblB-type MMA even very early in life, suggesting that this phenotype may be independent of metabolic control.

Congenital aortic stenosis due to unicuspid unicommissural aortic valve: a case report.

BACKGROUND: Unicuspid unicommissural aortic valve is an extremely rare congenital anomaly that usually presents in adulthood but can rarely present in infancy. We report a 17-year-old patient with congenital aortic stenosis secondary to unicuspid unicommissural aortic valve that was successfully treated with aortic valve replacement. CASE PRESENTATION: The patient was diagnosed with aortic stenosis after a murmur was heard in the newborn nursery and subsequently underwent aortic balloon valvuloplasty 6 weeks after birth. He had been regularly followed up since and underwent numerous cardiac catheterizations, including another aortic balloon valvuloplasty at age 13. During follow-up at age 17, the patient presented with symptomatic severe aortic stenosis and mild left ventricular hypertrophy. Aortic valve replacement was planned since the patient was nearly adult-sized and to reduce the risk of cardiac decompensation. During the operation an unicuspid unicommissural aortic valve was revealed. The patient recovered well post-operatively. He was discharged 5 days after the surgery in good condition and was completely symptom-free at follow-up 6 weeks later. CONCLUSIONS: Unicuspid aortic valve is a rare congenital anomaly that can cause congenital aortic stenosis. It is seldom diagnosed pre-operatively but should be suspected in infants presenting with aortic stenosis.

A frameshift deletion in the sarcomere gene MYL4 causes early-onset familial atrial fibrillation.

AIMS: Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in man, causing substantial morbidity and mortality with a major worldwide public health impact. It is increasingly recognized as a highly heritable condition. This study aimed to determine genetic risk factors for early-onset AF. METHODS AND RESULTS: We sequenced the whole genomes of 8453 Icelanders and imputed genotypes of the 25.5 million sequence variants we discovered into 1799 Icelanders with early-onset AF (diagnosed before 60 years of age) and 337 453 controls. Each sequence variant was tested for association based on multiplicative and recessive inheritance models. We discovered a rare frameshift deletion in the myosin MYL4 gene (c.234delC) that associates with early-onset AF under a recessive mode of inheritance (allelic frequency = 0.58%). We found eight homozygous carriers of the mutation, all of whom had early-onset AF. Six of the homozygotes were diagnosed by the age of 30 and the remaining two in their 50s. Three of the homozygotes had received pacemaker implantations due to sick sinus syndrome, three had suffered an ischemic stroke, and one suffered sudden cardiac death. CONCLUSIONS: Through a population approach we found a loss of function mutation in the myosin gene MYL4 that, in the homozygous state, is completely penetrant for early-onset AF. The finding may provide novel mechanistic insight into the pathophysiology of this complex arrhythmia.

Large-scale whole-genome sequencing of the Icelandic population.

Here we describe the insights gained from sequencing the whole genomes of 2,636 Icelanders to a median depth of 20×. We found 20 million SNPs and 1.5 million insertions-deletions (indels). We describe the density and frequency spectra of sequence variants in relation to their functional annotation, gene position, pathway and conservation score. We demonstrate an excess of homozygosity and rare protein-coding variants in Iceland. We imputed these variants into 104,220 individuals down to a minor allele frequency of 0.1% and found a recessive frameshift mutation in MYL4 that causes early-onset atrial fibrillation, several mutations in ABCB4 that increase risk of liver diseases and an intronic variant in GNAS associating with increased thyroid-stimulating hormone levels when maternally inherited. These data provide a study design that can be used to determine how variation in the sequence of the human genome gives rise to human diversity.

[Pulmonary embolism in a teenage girl]. / Blóðsegarek til lungna hjá unglingsstúlku - sjúkratilfelli.

Pulmonary embolism is an uncommon but potentially life threatening disease in children and adolescents. The clinical findings can be similar to other more common conditions such as pneumonia. Therefore high level of suspicion is required for early and accurate diagnosis. Most children have at least one underlying risk factor, either inherited or acquired. Computed tomography is the most widely used method in diagnosing pulmonary embolism. Anticoagulation is the mainstay of therapy for pulmonary embolism, however, acute surgery may be required for removal of the embolism. We report a case of pulmonary embolism in a teenage girl with serious circulatory failure where emergency surgery was needed.

[A case report - Severe electrolyte disturbances in an eight week old boy]. / Sjúkratilfelli - lífshaettulegar truflanir á blódsöltum hjá átta vikna dreng.

Hyponatremia is the most common electrolyte abnormality in children and underlying causes are many. It is most often caused by excessive salt loss from the gut but is also associated with severe systemic disorders in which there is actual or apparent aldosterone deficiency, such as congenital adrenal hyperplasia (CAH), which is the most common inherited disorder of aldosterone synthesis, and pseudohypoaldosteronism (PHA). Abscent aldosterone activity also leads to hyperkalemia which is characteristic for PHA and can result in life threatening arrythmias. This is a case report about a boy presenting with life threatening electrolyte disturbances in conjunction with PHA resulting from pyelonephritis and vesicoureteral reflux.

[Fetal echocardiography in Iceland 2003-2007; indications and outcomes]. / Fósturhjartaómskodanir á Islandi 2003-2007; ábendingar og útkoma.

OBJECTIVE: The aim of the study was to evaluate the indications and outcomes of fetal echo (FE) and determine which indication has the highest detection rate for congenital heart disease (CHD). METHODS: The referral indications and results of FE performed in Iceland during 2003-2007 were reviewed. Information regarding gestational age at diagnosis, nuchal translucency, pregnancy outcome, autopsy results and postnatal diagnosis were obtained from medical records. RESULTS: During the five year period 1187 FE were performed. Structural heart defect was diagnosed in 73 fetuses. The most common referral indication was family history of CHD (631;53.2%) which led to diagnosis of 18 heart defects prenatally (2.9%). The second most common referral indication was increased nuchal translucency (159) and abnormal cardiac findings were present in 16 cases (10.1%). A total of 30 women were referred for FE because of abnormal four chamber view (AFCV) which resulted in the diagnosis of 22 (73.3%) major heart defects, either incompatible with life or requiring immediate intervention after birth. Other indications led mostly to the diagnoses of minor defects. CONCLUSIONS: AFCV is the most important predictor for diagnosis of structural heart defects. 2,5% were referred for FE due to AFCV which led to diagnosis of 30% of all heart defects, all of which were major. Key words: fetal echocardiography, indications, congenital heart disease.

[Surgery for coarctation of the aorta in Iceland 1990-2006]. / Arangur skurdadgerda vid medfaeddri ósaedarthrengingu hjá börnum á Islandi 1990-2006.

BACKGROUND AND AIMS: Coarctation of the aorta (CoA) is a congenital narrowing of the aorta, distal to the origin of the left subclavian artery. Treatment consists of surgical excision but balloon angioplasty is also a treatment option for selected patients. The aim of this study was to evaluate surgical outcome in children operated for CoA in Iceland. MATERIAL AND METHODS: All Icelandic children (<18 yrs.) operated for CoA in Iceland between 1990 and 2006. Patients operated abroad (n=17) or managed conservatively (n=12) were excluded. Mean follow up period was 8.5 +/- 4.3 years. RESULTS: Of 67 children diagnosed with CoA, 38 were operated on in Iceland (mean age 36 +/- 58 months, and 22 male and 16 female patients), 10 required immediate surgery for cardiac failure and eight were diagnosed incidentally. Extended end-to-end anastomosis was the most common procedure (n=31). Subclavian-flap aortoplasty was performed in seven patients. Average operation time was 134 min. and mean aortic closure time was 21 +/- 9 min. Hypertension (58%) and heart failure (11%) were the most common postoperative complications. Recoarctation developed 35 +/- 56 months after surgery in seven patients (18%) and was successfully treated with balloon angioplasty. There were no operative deaths and no patients developed paraplegia. One patient suffered an ischemic injury to the brachial plexus. Today all of the patients are alive, except for one patient that died four months after surgery from heart failure. CONCLUSION: Majority of Icelandic patients with CoA are operated on in Iceland with excellent outcome, both regarding short term complications and long term survival.

[Pediatric life support]. / Endurlífgun á börnum.

Diseases which result in respiratory failure or hypotension are the most common cause of cardiac arrest in children. Whereas heart diseases are the most common cause of cardiac arrest in adults, they are uncommon cause in children. Accidents are the most common cause of out-of-hospital cardiac arrest. Prompt and skilled resuscitation efforts are important for favourable resuscitation outcome. This article provides guidelines for resuscitation in children from one month of age for health care providers. They are mainly based of recently published International Liaison Committee on Resuscitation (ILCOR) guidelines on resuscitation in children.

[Tetralogy of fallot in iceland from 1968 to 2001.].

OBJECTIVE: We reviewed our experience regarding tetralogy of Fallot (TOF) in Iceland over a 34 year period from 1968 to 2001. We looked at incidence, diagnosis,treatment and outcome and any changes in these parameters during the study period. MATERIALS AND METHODS: Data were obtained from hospital records containing echocardiographic, cardiac catheterization, surgical and autopsy reports. RESULTS: Forty six children were diagnosed as having TOF during the study period. The incidence was 1:3209 births and male to female ratio 1.2:1. The followup period was from two months to 33 years (median 10.5 years). Thirty seven patients had classic TOF, six had TOF with pulmonal atresia and three had other anatomical variants. Six children had chromosomal abnormalities and another five had physical anomalies outside of the heart. Nine children (24.3%) with classic TOF had a systemic to pulmonary artery shunt placed. Thirty eight (82.6%) of the patients have had corrective cardiac surgery and five in addition are scheduled to undergo such procedure in the near future. Three patients died before corrective surgery. All corecctive operations were carried out abroad. Half of the patients had difficulties following surgery and two (5.3%) died in the immediate post operative period. Of the 46 children born with TOF during the study period, seven (15.2%) have died and three are lost to followup. Corrective heart surgery had been done in four of the seven patients who died. Of the 36 patients alive in whom current information is available, 32 (88.9%) are in good physical condition leading full active lives. Corrective surgery which is planned for the other four is expected to improve their condition. Of 30 patients with classic TOF, two are being treated for arrhythmia and four have had interventional cardiac catheterizations three to 24 years following corrective surgery. In 10 of 30 pateints with classic TOF the most recent echocardiogram showed significant abnormalities. Most commonly this consisted of moderate to severe enlargement of the right ventricle with significant pulmonary valve insufficiency. CONCLUSIONS: TOF is a complex congenital heart defect with high incidence of coexistant chromosomal and physical abnormalities. Progress in recent years regarding surgical treatment and care of these patients in general has dramatically improved outcome.

Congenital cardiac malformations in Iceland from 1990 through 1999.

INTRODUCTION AND BACKGROUND: About 1% of live-born children have congenital malformations of the heart. The aim of our study was to investigate the incidence of such defects in children born in Iceland during a period of 10 years, extending from 1990 through 1999. MATERIALS AND METHODS: Information about the patients was obtained from medical records from two hospitals that cover the whole country, a private clinic of pediatric cardiologists, an echocardiography database, autopsy reports, and death certificates. We investigated the distribution of specific malformations, the age at diagnosis, the symptoms leading to the diagnosis, the source of referral, and treatment and quality of life. RESULTS: Between 1990 and 1999, there were 44,013 live births in Iceland, of which 740 patients were diagnosed with congenital cardiac malformations, accounting for 1.7% of the live-born children. The distribution was made up of 338 patients with ventricular septal defect (45.7%), 90 with atrial septal defect (12.2%), 85 with patency of the arterial duct (11.5%), 48 with pulmonary valvar stenosis (6.5%), 38 with a bicuspid aortic valve (5.1%), 28 with aortic coarctation (3.8%), 22 with tetralogy of Fallot (3.0%), 14 with transposed great arteries (1.9%), 11 with aortic stenosis (1.5%), 10 with atrioventricular septal defect and common atrioventricular orifice (1.4%), 9 with mitral valvar regurgitation (1.2%), 7 with sub-aortic stenosis (0.9%), and 5 with hypoplasia of the left heart (0.7%). Extracardiac anomalies were seen in 89 patients (12.0%). Chromosomal defects were seen in 36 patients, of whom 28 had Down's syndrome. DISCUSSION: The annual incidence of diagnosis of patients with congenital cardiac malformations increased during the period of study. This was noted for minor defects, but the incidence of the major anomalies did not alter. Our observed yearly incidence, at 1.7%, was higher than noted in a previous study covering the years 1985 through 1989, and is also higher than in other population-based studies. The most likely explanation is the fact that access to pediatric cardiologists in Iceland is very good. Diagnosis, registration, and follow-up are conducted by only a few cardiologists, and take place at a single center for pediatric cardiology.

Adenine nucleotide translocator 1 deficiency associated with Sengers syndrome.

Sengers syndrome is characterized by congenital cataracts, hypertrophic cardiomyopathy, mitochondrial myopathy, and lactic acidosis, but no abnormalities have been found with routine mitochondrial biochemical diagnostics (the determination of pyruvate oxidation rates and enzyme measurements). In immunoblot analysis, the protein content of the mitochondrial adenine nucleotide translocator 1 (ANT1) was found to be strongly reduced in the muscle tissues of two unrelated patients with Sengers syndrome. In addition, low residual adenine nucleotide translocator activity was detected upon the reconstitution of detergent-solubilized mitochondrial extracts from the patients' skeletal or heart muscle into liposomes. Sequence analysis and linkage analysis showed that ANT1 was not the primary genetic cause of Sengers syndrome. We propose that transcriptional, translational, or posttranslational events are responsible for the ANT1 deficiency associated with the syndrome.

[Congenital heart defects in Iceland 1990-1999.].

OBJECTIVE: About 1% of live born children have congenital heart defects (CHD). Knowledge of the true incidence of CHD is important because of the risk of bacterial endocarditis in patients with heart defects. This knowledge could also serve as a basis for research on the etiology of CHD. The aim of our study was to investigate the incidence of CHD in children born in Iceland during a ten year period, from 1990 to 1999. A similar study on CHD was carried out in Iceland for children born 1985-1989. The incidence of CHD in the present study was compared to the previous and to similar studies from other countries. MATERIAL AND METHODS: Information about the patients were obtained from medical records from two hospitals covering the whole country, a private clinic of pediatric cardiologists, echocardiography database, autopsy reports and death certificates. Distribution of specific heart defects, age at diagnosis, symptoms leading to the diagnosis, referral pattern, treatment and quality of life was investigated. Other congenital defects, chromosomal defects and syndromes in the patients were studied. Premature children with patent ductus arteriosus (PDA) and children with patent foramen ovale (PFO) or atrial septal defect (ASD) smaller than four millimeters were excluded. We also studied the incidence of bicuspid aortic valve (BAV). All diagnoses were confirmed with echocardiography and in some cases cardiac catheterization. RESULTS: Between 1990 and 1999 there were 44,013 live births in Iceland, 740 children were diagnosed with a CHD or 1.7% of live born children. Yearly incidence varied from 1.04% of live births in 1991 to 2.34% in 1997. Male/female ratio was 1/1. The distribution of the defects was following: ventricular septal defect (VSD) 338 (45.7%), ASD 90 (12.2%), PDA 85 (11.5%), valvar pulmonal stenosis 48 (6.5%), BAV 38 (5.1%), coarctation of the aorta 28 (3.8%), tetrology of Fallot 22 (3.0%), transposition of the great arteries 14 (1.9%), aortic stenosis 11 (1.5%), common atrioventricular septal defect 10 (1.4%), mitral valve regurgitation 9 (1.2%), sub-aortic stenosis 7 (0.9%) and hypoplastic left heart syndrome 5 (0.7%). Other defects were less frequent. About 47% of children with CHD were diagnosed either before birth or before discharge from the delivery institution. A cardiac murmur on examination was the most common symptom leading to the diagnosis of CHD, 631 patients (85.3%). Extracardiac anomalies were seen in 89 patients (12.0%). Chromosomal abnormalities were seen in 36 patients of whom 28 had Down's syndrome. The majority or 499 patients have no symptoms but are still in follow-up, 20 patients have daily symptoms and/or receive medical treatment and 27 patients have died. Conslusions: Annual incidence of patients diagnosed with a CHD has increased during the study period. This is observed in minor CHD but the incidence of major defects does not alter. This yearly incidence (1.7%) is higher than in the previous study, where it was 1.1%. The difference can partly be explained by the BAVs, which were excluded in the 1985-1989 study. But the number of CHD diagnosed each year has increased, this being most pronounced in the last three years. The annual incidence in our study is also higher than in other population studies. The most likely explanation for the higher incidence in our study is the fact that access to pediatric cardiologists is very good in Iceland. Diagnosis, registration and follow-up is conducted by only a few cardiologists for the whole nation and takes place at a single pediatric cardiology center. Of 740 patients diagnosed with CHD in the study period 713 are alive. The outcome of the therapy is good and the majority of the patients has no symptoms.