Pietro Ragonese

Amiodarone Used Alone or in Combination with Propranolol: A Very Effective Therapy for Tachyarrhythmias in Infants and Children

Abstract. The aim of the study was to evaluate the efficacy of amiodarone used alone or in combination with propranolol in infants and children affected by life-threatening or drug-resistant tachyarrhythmias. The study included 27 children (median age 3 months), affected by life-threatening and/or drug-resistant supraventricular or ventricular tachyarrhythmias. The loading dose of amiodarone was 10–20 mg/kg/day and the maintenance dose ranged between 3 and 20 mg/kg/day. When amiodarone was ineffective, propranolol was added at a dosage of 2–4 mg/kg/day. The study population was divided into two groups: group A was composed of patients <1 year and group B of patients >1 year. The effectiveness of the therapy was assessed by clinical evaluation, Holter monitoring, exercise testing, and, in patients with reentry tachycardias, electrophysiological testing. Amiodarone used alone was effective or partially effective in 4/14 (28%) patients in group A and in 11/13 (85%) patients in group B (p < 0.006). Among amiodarone-resistant patients, the combined therapy with propranolol was effective in 8/10 patients in group A and 2/2 patients in group B. Therefore, amiodarone used alone or in combination with propranolol was effective in 25/27 (93%) patients. During the follow-up (20.5 ± 13 months) there were no arrhythmic effects but side effects were noted in 5/27 (18.5%) patients. Amiodarone seems to be an effective drug in the control of the life-threatening and/or drug-resistant supraventricular and ventricular tachyarrhythmias in children. The addition of propranolol can significantly enhance the success rate of this class III drug, especially in the treatment of reentry tachycardias due to accessory pathways.

Reciprocating supraventricular tachycardia in children: Low rate at rest as a major factor related to propensity to syncope during exercise

Reciprocating supraventricular tachycardia may have several clinical presentations, with symptoms often more severe during exercise or emotional stress. This study shows by using transesophageal atrial pacing, the factors related to syncope during exercise. Between May 1989 and June 1994, transesophageal atrial pacing was performed at rest and during exercise in 75 children aged > 6 years with suspected or documented episodes of paroxysmal supraventricular tachycardia. Reciprocating supraventricular tachycardia could be induced both at rest and during exercise in 22 patients (8 girls, 14 boys; mean age 10.6 +/- 2.7 years, range 7 to 15 years) with ventriculoatrial interval < 70 msec in 11 patients and > 70 msec in 11. At rest, all patients had palpitations caused by the induction of tachycardia. After conversion to sinus rhythm, when tachycardia was induced during exercise, symptoms did not change in 14 patients (group A), whereas symptoms worsened (presyncope) in eight (group B). The statistical analysis showed a significant difference of mean reciprocating supraventricular tachycardia rate at rest between the two groups (group A, 211 +/- 23 beats/min; group B, 173 +/- 33 beats/min; p = 0.0057) and reciprocating supraventricular tachycardia rate variation from rest to exercise (group A, 62 +/- 18 beats/min; group B, 105 +/- 24 beats/min; p = 0.0001). These data suggest that children with low tachycardia rate during normal activities may have syncope more frequently, independently of the tachycardia rate during exercise or emotional stress.

Tachycardias in children originating in the right ventricular outflow tract: lack of clinical features predicting the presence and severity of the histopathological substrate.

The aim was to determine whether the clinical features of tachycardias originating from the right ventricular outflow tract in children with an apparently normal heart could predict the presence and the severity of the histopathological substrate. Thirteen children (median age 6 years; range 6 months-12 years) with tachycardia originating from the right ventricular outflow tract of apparently normal hearts, were assessed by echocardiography, heart catheterization with angiography, endomyocardial biopsy (13 patients) and magnetic resonance imaging (MRI) (nine patients). Tachycardia was symptomatic in six and sustained in nine. Endomyocardial biopsy and MRI revealed acute myocarditis in five patients (38%), fatty infiltration of the right ventricle in two (15%), and minor histologic abnormalities in three (23%). Myocarditis was diagnosed in three of nine patients with sustained ventricular tachycardia, as opposed to two of four with non-sustained tachycardia (p = NS); in three of six symptomatic versus two of seven asymptomatic patients (p = NS); and in two of eight patients in whom ventricular tachycardia was induced during exercise testing as opposed to one of three in which it was not inducible (p = NS). A histopathological substrate was found in six of nine patients with sustained ventricular tachycardia, and in all four with non-sustained tachycardia (p = NS); in five of six patients with symptoms versus five of seven asymptomatic patients (p = NS); and in five of eight with inducible ventricular tachycardia during exercise testing versus all three in whom it was not inducible (p = NS). The mean rate of tachycardia was 184+/-39 beats min(-1) in patients with myocarditis, as opposed to 171+/-48 in patients without myocarditis (p = NS); and 163+/-33 in patients with a histopathological substrate compared with 210+/-65 in patients without a histopathological substrate (p = NS). It is concluded that a histopathological substrate is present in the greater majority of children affected by the so-called right ventricular outflow tract tachycardia, but that the clinical features of the tachycardia do not predict the presence and the severity of this histopathological substrate.