Effect of intravenous propranolol or verapamil on infant orthodromic reciprocating tachycardia

Management of infants, children, and adolescents with paroxysmal supraventricular tachycardia

Several acceptable options are available for the successful management of children either with an acute PSVT episode or with ongoing episodes. These options include the "no treatment" management approach. Although an example of an algorithm used in one center is provided for this Medical Progress article, other algorithms also are successfully practiced among pediatric cardiologists together with primary care pediatricians. Current and ongoing updated data related to the important factors of presenting symptoms, natural history, results of the treatment options, and the risk/ benefit ratios of the treatment options are essential when one is choosing the specific management approach.

Conversion of paroxysmal supraventricular tachycardia in a child with a slow verapamil infusion: case report and literature review

The investigators present the case of a 12-month-old female with Down's syndrome and an endocardial cushion defect who presented acutely ill in paroxysmal supraventricular tachycardia (PSVT). Unsuccessful vagal maneuvers were followed by a slow intravenous infusion of verapamil, during which the rhythm converted. The discussion which follows highlights the many issues to be addressed in the acute management of pediatric PSVT including the varied presentations, underlying etiologies, differential diagnosis, electrocardiographic findings, electrophysiologic mechanisms, and prognosis. The literature review concludes with a discussion of the many different therapies available for pediatric PSVT including vagal maneuvers, cardioversion, overdrive pacing, and pharmacologic therapies. In particular, the relative merits of verapamil and adenosine are discussed.

Cardiovascular and antiarrhythmic effects of esmolol in children

This prospective study evaluated the cardiovascular and antiarrhythmic effects of esmolol, an intravenous beta-blocker with an extremely short half-life. Twenty patients (aged 2 to 16 years) underwent diagnostic electrophysiologic studies at rest and during beta-blockade induced with esmolol. An initial dose of 600 micrograms/kg was infused for 2 minutes and followed by an infusion of 200 micrograms/kg per minute. The dosage was increased by 50 to 100 micrograms/kg per minute every 5 to 10 minutes until a reduction of greater than 10% in either heart rate or mean blood pressure was seen. The dosage required to achieve beta-blockade ranged from 300 to 1000 micrograms/kg per minute (mean 550 micrograms/kg per minute). Electrophysiologic effects included a decrease in the rate of sinoatrial node discharge and delay in conduction through the atrioventricular node. There was no effect on His-Purkinje conduction. Atrial and ventricular effective refractory periods were unchanged. In six patients with supraventricular tachycardia, esmolol prevented induction of tachycardia in four and slowed the rate of the tachycardia in two. In four patients with ventricular tachycardia, clinical findings were improved in three and unchanged in one. Heart rate and blood pressure returned to near baseline values 10 minutes after the esmolol infusion was stopped. Adverse ventricular electrophysiologic effects were observed in two patients with biopsy evidence of myocarditis. No other adverse effects were seen. We conclude that the effects of esmolol in children are similar to those of other beta-blockers and that it is useful in the evaluation and management of pediatric tachyarrhythmias. The weight-adjusted dosage required to induce beta-blockade in children is larger than the adult dosage, and the effects of esmolol dissipate rapidly.

Ventriculoatrial intervals during narrow complex reentrant tachycardia in children

Ventriculoatrial (VA) intervals during narrow complex tachycardia were measured in a pediatric population. The VA intervals were similar to those in adults but were slightly shorter. In the pediatric subjects values less than 60 msec excluded the participation of an accessory pathway in the tachycardia circuit. Three out of 11 patients with atrioventricular nodal reentrant tachycardia (AVNRT) had VA values greater than or equal to 70 msec, while 5 of 28 patients with orthodromic reciprocating tachycardia (ORT) had values less than or equal to 70 msec. Using a cut-off value of 70 msec as the sole criteria to distinguish between ORT and AVNRT could lead to errors in classification of the underlying mechanism of the tachycardia.

Evaluation and management of supraventricular tachycardia in children

Emergency physicians may be called on to resuscitate acute complications in pediatric patients with congenital heart disease. Supraventricular tachycardia, with or without hemodynamic decompensation, is one of the most serious complications. We present the case of a 22-month-old boy with a history of single ventricle who presented to our institution with a history of syncope and hemodynamically stable supraventricular tachycardia. Initial attempts at pharmacologic conversion with propranolol and verapamil failed. The arrhythmia was terminated in response to an IV fluid bolus and dopamine infusion and probably resulted from a combination of anemia, hypovolemia, and impaired contractility. Appropriate evaluation and management relating to the cre of acute supraventricular tachycardia in children are discussed.

Antiarrhythmic actions of diltiazem during experimental atrioventricular reentrant tachycardias. Importance of use-dependent calcium channel-blocking properties

The purpose of this study was to determine if the known frequency-dependent effects of diltiazem on inward calcium current result in selective actions during supraventricular tachycardia. These effects were evaluated by use of an experimental model of orthodromic atrioventricular reentrant tachycardia (AVRT). AVRT was induced in 15 dogs over a wide range of retrograde conduction times before and after two doses of diltiazem. Diltiazem produced a tachycardia-related suppression of atrioventricular nodal conduction resulting in greater efficacy for faster than for slower AVRTs. The degree of slowing for tachycardias that remained inducible after diltiazem administration was greater for AVRTs with a rapid initial rate (dose 1, 29%; dose 2, 40%) than for slower AVRTs (dose 1, 11%, p less than 0.01; dose 2, 18%, p less than 0.001). Rate-dependent AVRT slowing occurred because of a time-dependent phase of AH interval prolongation after the onset of tachycardia, which was observed only after diltiazem administration. to further clarify the mechanism of diltiazem's selective actions against faster tachycardias, its effects on the minimum pathway for reentry, or wavelength, were examined in four dogs. The ratio of refractory period to revolution time (RP/RT), an index of wavelength, was measured for each AVRT before and after diltiazem administration. Diltiazem increased the positive slope of the relation between RP/RT and the AVRT rate threefold compared with control (p less than 0.05). This rate-dependent effect prevented AVRT when RP/RT became greater than unity. In conclusion, rate-dependent atrioventricular node depression by diltiazem results in greater tachycardia slowing and higher rates of termination during atrioventricular reentrant tachycardias with faster initial rates and shorter retrograde conduction intervals.