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This study aimed to evaluate the incidence of cardiac disorders among children with mid-exertional syncope evaluated by a paediatric cardiologist, determine how often a diagnosis was not established, and define potential predictors to differentiate cardiac from non-cardiac causes.
We carried out a single-centre, retrospective review of children who presented for cardiac evaluation due to a history of exertional syncope between 1999 and 2012. Inclusion criteria included the following: (1) age ⩽18 years; (2) mid-exertional syncope; (3) electrocardiogram, echocardiogram and an exercise stress test, electrophysiology study, or tilt test, with exception of long QT, which did not require additional testing; and (4) evaluation by a paediatric cardiologist. Mid-exertional syncope was defined as loss of consciousness in the midst of active physical activity. Patients with peri-exertional syncope immediately surrounding but not during active physical exertion were excluded.
A total of 60 patients met the criteria for mid-exertional syncope; 32 (53%) were diagnosed with cardiac syncope and 28 with non-cardiac syncope. A majority of cardiac patients were diagnosed with an electrical myopathy, the most common being Long QT syndrome. In nearly half of the patients, a diagnosis could not be established or syncope was felt to be vasovagal in nature. Neither the type of exertional activity nor the symptoms or lack of symptoms occurring before, immediately preceding, and after the syncopal event differentiated those with or without a cardiac diagnosis.
Children with mid-exertional syncope are at risk for cardiac disease and warrant evaluation. Reported symptoms may not differentiate benign causes from life-threatening disease.
QTc prolongation has been reported in adults following cardiopulmonary bypass; however, this phenomenon has not been studied in children with congenital cardiac disease. This study's aim was to formally assess QTc in children undergoing cardiac surgery.
Pre-operative and post-operative electrocardiograms during hospital stays were prospectively analysed on 107 consecutive patients under 18 years of age undergoing cardiac surgery. QTc was measured manually in leads II, V4, and V5. Measurements of 440 and 480 milliseconds were used to categorise patients. Peri-procedural data included bypass and cross-clamp time, medications, and electrolyte measurements. Outcome data included arrhythmias, length of mechanical ventilation, and hospital stay. Patients with post-operative new bundle branch block or ventricularly paced rhythm were excluded.
In all, 59 children were included, out of which 26 had new QTc over 440 milliseconds and 6 of 59 had new QTc over 480 milliseconds post-operatively. The mean increase in post-operative QTc was 25 milliseconds, p=0.0001. QTc over 480 was associated with longer cross-clamp time, p=0.003. Other risk factors were not associated with post-operative QTc prolongation. This phenomenon was transient with normalisation occurring in 67% of patients over 60 hours on average. One patient with post-operative QTc over 440 milliseconds developed ventricular tachycardia. There was no correlation between prolonged QTc and duration of mechanical ventilation, or hospital stay.
A significant number of children undergoing cardiac surgery showed transient QTc prolongation. The precise aetiology of QT prolongation was not discerned, though new QTc over 480 milliseconds was associated with longer cross-clamp time. In this cohort, transient QTc prolongation was not associated with adverse sequela.
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