B. Lefort

Carnitine deficiency induces a short QT syndrome

BACKGROUND Short QT syndrome is associated with an increased risk of cardiac arrhythmias and unexpected sudden death. Until now, only mutations in genes encoding the cardiac potassium and calcium channels have been implicated in early T-wave repolarization. OBJECTIVE The purpose of this study was to confirm a relationship between a short QT syndrome and carnitine deficiency. METHODS We report 3 patients affected by primary systemic carnitine deficiency and an associated short QT syndrome. Ventricular fibrillation during early adulthood was the initial symptom in 1 case. To confirm the relationship between carnitine, short QT syndrome, and arrhythmias, we used a mouse model of carnitine deficiency induced by long-term subcutaneous perfusion of MET88. RESULTS MET88-treated mice developed cardiac hypertrophy associated with a remodeling of the mitochondrial network. The continuous monitoring of electrocardiograms confirmed a shortening of the QT interval, which was negatively correlated with the plasma carnitine concentration. As in humans, such alterations coincided with the genesis of ventricular premature beats and ventricular tachycardia and fibrillation. CONCLUSION Altogether, these results suggest that long-chain fatty acid metabolism influence the morphology and the electrical function of the heart.

Association Between Tetralogy of Fallot and Tracheobronchial Branching Abnormalities: A New Clue for Pathogenesis?

Background In our practice, we noticed an increased frequency of tracheobronchial branching abnormalities (TBAs) in patients with tetralogy of Fallot (ToF). This study aimed to determine whether an association exists between congenital TBAs and ToF with or without pulmonary atresia. Methods and Results The frequency of TBAs on chest computed tomography was assessed in 55 patients with ToF without pulmonary atresia, 34 patients with ToF with pulmonary arteria, and 100 control patients. We then looked for a possible association between TBAs and pulmonary artery branch hypoplasia, the presence of major aortopulmonary collateral arteries, and the presence of the chromosome 22q11 deletion. TBAs were significantly more frequent in patients with ToF with or without pulmonary atresia than in the control group (any TBAs, 21% versus 2% [P<0.001]; bronchial situs anomalies, 6% versus 0% [P=0.002]; right tracheal bronchus, 4% versus 0% [P=0.04]; left eparterial bronchus, 8% versus 0% [P=0.005]); and tended to be more frequent in those with ToF without pulmonary atresia than in those with ToF with pulmonary atresia (any TBAs, 27% versus 12% [P=0.11]; left eparterial bronchus, 13% versus 0% [P=0.04]). TBAs were readily multiple (8 patients of 19 with TBA) and concerned essentially the upper lobes. TBAs were not associated with pulmonary branch hypoplasia, major aortopulmonary collateral arteries, or the chromosome 22q11 deletion. Conclusions We demonstrated a significantly increased frequency of tracheobronchial abnormalities in patients with ToF with or without pulmonary atresia compared with a control group. These results suggest an interaction between abnormalities in conotruncal septation and tracheobronchial branching and may provide a new clue to the pathogenesis of conotruncal heart diseases.

Pharmacological inhibition of carnitine palmitoyltransferase 1 restores mitochondrial oxidative phosphorylation in human trifunctional protein deficient fibroblasts

BACKGROUND Mitochondrial Trifunctional Protein deficiency (TFPD) is a severe genetic disease characterized by altered energy metabolism and accumulation of long-chain (LC) acylcarnitines in blood and tissues. This accumulation could impair the mitochondrial oxidative phosphorylation (OxPhos), contributing to the non-optimal outcome despite conventional diet therapy with medium-chain triglycerides (MCT). METHOD Acylcarnitine and OxPhos parameters were measured in TFPD-fibroblasts obtained from 8 children and cultured in medium mimicking fasting (LCFA) or conventional treatment (MCT), with or without Etomoxir (ETX) an inhibitor of carnitine palmitoyltransferase 1 (CPT1) activity, and were compared to results obtained with fibroblasts from 5 healthy-control children. The effects of various acylcarnitines were also tested on control fibroblasts. RESULTS In the LCFA-condition, TFPD-fibroblasts demonstrated a large accumulation of LC-acylcarnitines associated with decreased O2-consumption (63±3% of control, P<0.001) and ATP production (67±5%, P<0.001) without modification of coupling efficiency. A dose-dependent decrease in O2-consumption was reproduced in control fibroblasts by addition of increasing dose of LC-acylcarnitines, while it was almost preserved with MC-acylcarnitines. The MCT-condition reduced LC-acylcarnitine accumulation and partially improved O2-consumption (80±3%, P<0.01) in TFPD-fibroblasts. The addition of ETX in both LCFA- and MCT-conditions normalized acylcarnitine profiles and restored O2-consumption and ATP production at the same levels than control. CONCLUSION Accumulation of LC-acylcarnitines plays a major role in the pathophysiology of TFPD, reducing OxPhos capacities. These deleterious effects could be partially prevented by MCT-therapy and totally corrected by ETX. Inhibition of CPT1 may be view as a new therapeutic target for patients with a severe form of TFPD.

Souffle cardiaque chez l’enfant asymptomatique : quand demander un avis cardiologique ?

Heart murmurs are common in children and adolescents. Although most are innocent, an isolated heart murmur in asymptomatic children may be the sole finding indicating serious heart disease. Historical elements of familial heart disease, cardiovascular symptoms and a well-conducted medical examination can identify children with an increased risk of heart disease. The distinction between an innocent heart murmur and a pathologic heart murmur is not always easy for primary care physicians because most of them have little experience with auscultation searching for congenital heart malformation. Echocardiography provides a definitive diagnosis of heart disease but is not required in case of innocent murmur. Inappropriate pediatric cardiologist and echocardiographic referral leads to useless and expensive examinations, resulting in a work overload for pediatric cardiologists. The objective of this review is to provide the keys to differentiate innocent and pathologic murmurs, and to help physicians decide on the optimal diagnostic strategy.

SFRP CO-02 – Effets des dérivés des acides gras à chaîne longue sur l’énergétique mitochondriale

Objectif Etudier l’effet des derives des acides gras a chaine longue (AGCL) sur l’activite de la chaine respiratoire. Methode La production energetique de la chaine respiratoire a ete mesuree par oxygraphie sur des fibroblastes de patients avec deficit de b-oxydation des AGCL (LCHAD) cultives dans diverses conditions et comparee a des fibroblastes controles (CTRL). Les derives des AGCL ont ete estimes par le profil des acylcarnitines cellulaires. Resultats Les fibroblastes LCHAD avaient une accumulation d’acylcarnitines a chaine longue par rapport aux CTRL. En condition de production d’ATP (etat 3), leur consommation d’oxygene (- 48±18%, p Conclusion L’accumulation de derives des AGCL s’accompagnait d’une alteration reversible de la phosphorylation oxydative dans des fibroblastes LCHAD. Ce mecanisme pourrait jouer un role toxique majeur dans les decompensations des deficits de b-oxydation des AGCL.