Practice Variation Among Canadian Pediatric Cardiologists in Medical Management of Dilated Ascending Aorta in Patients With Bicuspid Aortic Valve.

BACKGROUND: Medical therapy is often prescribed to reduce the rate of aortic dilatation and prevent aortic dissection in patients with bicuspid aortic valve (BAV) despite a lack of evidence. We conducted an anonymous survey to gain insight into Canadian clinical practice regarding medical therapy used to slow the progression of aortic dilatation in patients with BAV. METHODS: A questionnaire was sent to 115 paediatric cardiologists and 18 adult congenital heart disease specialists in Canada. RESULTS: Ninety of 113 paediatric cardiologists (80%) completing the questionnaire reported prescribing medication to reduce the rate of aortic dilatation. Some 75% (61/81) of them reported prescribing medications on the basis of aortic size z scores, and 78% (48/61) considered medication at a z score between ≥ 2 and < 5. The remaining 25% of responders (20/81) reported prescribing medications on the basis of absolute aortic diameter, and 80% (16/20) of them considered initiating medical therapy at an aortic diameter > 40 mm to < 50 mm. For practical purposes, however, 40% of respondents (45/113) would not or rarely consider medical therapy for this indication because of variation in the threshold for initiating treatment. Ten of 14 adult congenital heart disease specialists' responses (71%), reported prescribing medications who were excluded because of missing data. CONCLUSION: The majority of Canadian paediatric cardiologists reported prescribing medications to slow the rate of aortic dilatation in patients with BAV. However, there is heterogeneity in the criteria to prescribe medical therapy. A multicenter randomized controlled trial is needed to establish the role of medical therapy in this patient population.

INTRODUCTION: En dépit du manque de données probantes, un traitement médical est souvent prescrit pour réduire le taux de dilatation aortique et prévenir la dissection aortique chez les patients ayant une bicuspidie aortique (BA). Nous avons mené une enquête anonyme pour avoir un aperçu de la pratique clinique au Canada en ce qui concerne le traitement médical utilisé pour ralentir la progression de la dilatation aortique chez les patients ayant une BA. MÉTHODES: Nous avons envoyé un questionnaire à 115 cardiologues en pédiatrie et à 18 spécialistes en cardiopathie congénitale de l'adulte du Canada. RÉSULTATS: Quatre-vingt-dix des 113 cardiologues en pédiatrie (80 %) ayant rempli le questionnaire ont signalé prescrire des médicaments pour réduire le taux de dilatation aortique. Certains d'entre eux, soit 75 % (61/81) ont signalé prescrire des médicaments en fonction du Z-score de la taille aortique, et 78 % (48/61) ont envisagé de prescrire les médicaments lorsque le Z-score était entre ≥ 2 et < 5. Les 25 % de répondants restants (20/81) ont signalé prescrire des médicaments en fonction du diamètre aortique absolu, et 80 % (16/20) d'entre eux ont envisagé de faire commencer le traitement médical lorsque le diamètre aortique était entre > 40 mm et < 50 mm. Concrètement, toutefois, 40 % des répondants (45/113) n'ont pas envisagé ou ont rarement envisagé de prescrire un traitement médical pour cette indication en raison de la variation dans le seuil de mise en place du traitement. Dix des 14 réponses (71 %) des spécialistes de la cardiopathie congénitale de l'adulte ont signalé prescrire des médicaments qui étaient exclus en raison de données manquantes. CONCLUSION: La majorité des cardiologues en pédiatrie du Canada ont signalé prescrire des médicaments pour ralentir le taux de dilatation aortique chez les patients ayant une BA. Toutefois, les critères utilisés pour prescrire un traitement médical sont hétérogènes. Un essai clinique multicentrique et à répartition aléatoire est nécessaire pour déterminer le rôle du traitement médical dans cette population de patients.

Dexamethasone given to premature infants and cardiac diastolic function in early childhood.

OBJECTIVES: To determine if dexamethasone given to premature infants with bronchopulmonary dysplasia would result in cardiac diastolic dysfunction in early childhood, a topic unstudied in humans. STUDY DESIGN: We compared seven children ages 3 to 8 years born at 26 weeks' gestation and given dexamethasone for bronchopulmonary dysplasia with eight gestation-matched and age-matched control children using echocardiography to assess measures of systolic and diastolic function. All dexamethasone patients had resolved hypertrophic cardiomyopathy. RESULTS: Dexamethasone patients had the same normal τ and isovolumic relaxation time (24.9 ± 2.8 and 54.6 ± 6.3 ms) as control patients (22.1 ± 3.0 and 48.8 ± 6.7 ms). Peak A velocities were the same in dexamethasone patients as in control patients (59.5 ± 15 versus 49.4 ± 5.8 cm/s, P = .10), resulting in unchanged E:A ratios (1.89 ± 0.57 versus 2.15 ± 0.43, P = .22). Peak E velocity and E-wave deceleration times were not different. We found no significant differences in measures of systolic function (heart rate-corrected velocity of circumferential fiber shortening, wall stress, and ejection fraction). Left ventricular mass was the same between the groups confirming resolution of hypertrophic cardiomyopathy. CONCLUSIONS: These data are consistent with normal myocardial relaxation, suggesting that long-term diastolic function is reassuringly normal in children who received dexamethasone as premature infants with resolution of hypertrophic cardiomyopathy.

Patent ductus arteriosus remodels cardiac sensory neuronal chemotransduction.

We sought to determine the capacity of neonatal ventricular sensory nerve endings (neurites) to transduce the cardiac milieu in the presence of cardiovascular pathology. The spontaneous activity generated by nodose ganglion cardiac afferent neurons was identified in situ using extracellular recording techniques in two groups of piglets approximately 2 weeks old: (i). controls that underwent sham operations (n=19 piglets) 2 weeks earlier and (ii). a pathological model of patent ductus arteriosus stented open for about 2 weeks (n=16 piglets). The capacity of ventricular sensory neurites associated with nodose ganglion afferent neurons to transduce local mechanical (including alterations in right or left ventricular volumes) or chemical stimuli was studied in both groups. The average conduction velocity of afferent axons associated with identified neuronal somata was estimated to be 1.5+/-0.6 or 2.9+/-1.3 m s(-1). Ventricular afferent neurons transduced mechanical stimuli similarly in both groups. In control animals, ventricular afferent neurons transduced the following chemicals: the sodium channel modifier veratridine (delta 23+/-7 impulses min(-1)), the P(1)-purinoceptor agonist adenosine (Delta 24+/-8 impulses min(-1)), and the beta-adrenoceptor agonist isoproterenol (delta 18+/-7 impulses min(-1)). On the other hand, patent ductus arteriosus cardiac afferent neurons did not transduce these chemicals. It is concluded that neonatal cardiac afferent neuronal chemosensory-as opposed to mechanosensory-transduction remodels in the presence of a patent ductus arteriosus. The reduced capacity of neonatal cardiac afferent neurons to transduce chemicals in the presence of a patent ductus arteriosus should be taken into account when considering neonatal cardiovascular control in such a state.

Surgery modifies cardiac sensory transduction.

OBJECTIVE: We sought to determine whether cardiac surgery, specifically the placement of an incision within a ventricular wall, affects the capacity of regional cardiac sensory nerve terminals (neurites) to transduce the local cardiac milieu. METHODS: The capacity of sensory neurites in the right ventricular outflow tract associated with afferent neurons in nodose ganglia to transduce their mechanical and chemical milieu was studied in 11 anesthetized pigs before and after performing a local ventriculotomy. RESULTS: Right ventricular outflow tract sensory neurites associated with 23 nodose ganglion afferent neurons were identified that transduced local mechanical deformation along with substance P. The capacity of these sensory neurites to transduce these stimuli was almost totally obtunded after local ventriculotomy. CONCLUSIONS: The capacity of afferent neurons to transduce the cardiac milieu can be modified by cardiac surgical interventions. This may have negative implications with respect to how the entire cardiac neuronal hierarchy transduces alterations in the cardiac milieu postsurgery. This fact should be taken into account when contemplating the placement of cardiac incisions during surgery.