The Wolff-Parkinson-White syndrome in childhood

Clinical and electrophysiologic evolution of the Wolff-Parkinson-White syndrome in children: impact on approaches to management

There is less certainty about the recommendations for radio-frequency ablation as a therapeutic option for Wolff-Parkinson-White syndrome in children as opposed to adults because of the different natural history and the age-related risks of ablation. To help decision-making, we evaluated the long term clinical evolution and electrophysiologic characteristics of pre-excitation in our series of children and young adults. We reviewed the clinical course of 109 patients below the age of 18 years who had been followed up over a period of 9+4 years, with a range from one to 27 years. This corresponded to 986 patient-years. We examined also the electrophysiologic data from 98 of those patients who underwent a transesophageal study. At the discovery of pre-excitation, 59% of patients were asymptomatic, while 29% developed supraventricular tachycardia during follow-up. The peak incidence of the onset of supraventricular tachycardia occurred during infancy. These patients had the highest incidence of subsequent spontaneous disappearance of the tachycardia (53%), such a favourable evolution being encountered in only 12% of patients in whom the abnormal rhythm first appeared after 12 years of age. Chronic medical treatment was required in 47% of patients, and proved completely effective in 45% of cases. The potential to induce atrial fibrillation, and the incidence pre-excitation considered to be high risk, with the shortest pre-excited RR interval equal to or less than 220 msec, was lowest in the group of patients aged less than 6 years of age, and highest in those older than 12 years of age (p <0.001). Pathways producing arrhythmia with high risk were more common in symptomatic (29%) than in asymptomatic patients (7%) (p<0.001). No mortality occurred. On the basis of our findings, we suggest that ablation should be avoided before the age of 5 or 6 years. Thereafter, the procedure should become the first line of treatment for symptomatic patients older than 12 years of age.

Recognition and management of childhood cardiac arrhythmias

Cardiac arrhythmias are common in children, but most of them are benign and do not signify underlying heart disease. However, the main tachyarrhythmias (SVT and VT) can cause cardiovascular collapse, and should therefore be treated promptly. Drug treatment is generally effective and is appropriate in stable patients. DC shock is the treatment of choice in patients with compromised circulation. There is a wide array of antiarrhythmic drugs and though they are generally safe, most of them have the potential for serious adverse effects. Hence, there is a need to exercise caution and balanced judgement in prescribing them. It is perhaps best for the general duty paediatric staff to be familiar with a select few, and stick to them if possible. Management of most cases of cardiac arrhythmia in children is within the competence of non-cardiologist paediatric staff. But in some instances cardiology referral will be required, either for further investigations, for decision regarding longterm drug therapy, or for more technical management modalities.

Orthodromic reciprocating tachycardia and heart failure in a dog with a concealed posteroseptal accessory pathway

A 4-month-old male Labrador Retriever was presented for recurrent bouts of pulmonary edema associated with tachycardia. Initial physical examination and echocardiography were unremarkable, and the electrocardiogram revealed only an intraventricular conduction disturbance. Subsequent recordings showed paroxysmal supraventricular tachycardia (SVT) (340 beats/min), which consistently produced pulmonary edema. The supraventricular tachycardia was unresponsive to adenosine, esmolol, and propranolol; was variable and transiently responsive to various vagal maneuvers and precordial thumps; and was always responsive to IV diltiazem. Multiple life-threatening episodes of SVT occurred, however, despite the chronic administration of oral diltiazem, propranolol, and procainamide. Diastolic cardiac dysfunction was documented by Doppler echocardiography and was thought to contribute to the development of pulmonary edema. A subsequent electrophysiologic study confirmed the presence of an atrioventricular posteroseptal accessory pathway that participated in orthodromic reciprocating tachycardia. This pathway was determined to conduct only in the retrograde direction ("concealed accessory pathway"). Intraoperative IV procainamide titration terminated the arrhythmia, which could not be reinduced when procainamide blood concentration approximated 20 micrograms/dL. Increasing the oral procainamide dose to achieve such plasma concentrations was successful in eliminating orthodromic reciprocating tachycardia, preventing heart failure, and returning Doppler indices of diastolic function to normal.

Cardiac evaluation of infants. The first year of life

Many structural congenital heart defects present at birth, and most are diagnosed by 1 year of age. Arrhythmias also are common during this time and may be particularly problematic. Identification of infants who may have a serious underlying congenital heart defect is important because many require prompt medical and surgical treatment. This article is a guide to the clinical findings that may assist the practitioner in the evaluation of infants with potential cardiac problems.