Case studies: Chronic accelerated ventricular rhythm

Accelerated idioventricular rhythm in three newborn infants with congenital heart disease

Accelerated idioventricular rhythm was observed in three newborn infants with congenital heart disease. This ventricular arrhythmia in all of our patients did not alter the clinical features of the congenital heart disease, and it disappeared at the ages of 84 days, 40 days, and 45 days, respectively. This arrhythmia is generally considered to be benign, which also appears to be the case with the newborn infant with congenital heart disease.

Ventricular tachycardia and accelerated ventricular rhythm presenting in the first month of life

Fourteen infants aged less than 1 month presented to our institution during the last 22 years with ventricular tachycardia (VT) or accelerated ventricular rhythm and a structurally normal heart. In 2, VT was associated with long QT syndrome. Both are alive on beta-blocker therapy, 1 with an implanted pacemaker. Twelve infants had accelerated ventricular rhythm, and 2 of these died in the first 2 months of life of unrelated conditions. The other 10 are alive at a median age of 4 years (range 2 months to 11 years), and none were lost to follow-up. Hemodynamic compromise did not occur with accelerated ventricular rhythm. The ventricular rate was very close to the sinus rate in all 12, less than 12% above the sinus rate. The mean QRS duration during accelerated ventricular rhythm was 92.5 ms, and averaged twice the QRS duration during sinus rhythm. Fusion beats were seen in all 12, and there was atrioventricular dissociation with capture beats in 10. In 2, ventriculoatrial conduction was present. Treatment was attempted in 5 of the 10 survivors with accelerated ventricular rhythm, and was thought to be successful in 4. Treatment was later successfully withdrawn in all 5, so that all 10 survivors were free of accelerated ventricular rhythm and were not receiving antiarrhythmic medications at last follow-up. Because of the excellent long-term outcome and the lack of hemodynamic compromise during the rhythm, it seems reasonable to withhold antiarrhythmic therapy in infants with accelerated ventricular rhythm and await resolution of the rhythm.

Accelerated idioventricular rhythm of infundibular origin in patients with a concealed form of arrhythmogenic right ventricular dysplasia

Five apparently healthy people (aged 16-47) presented with recurrent episodes of accelerated idioventricular rhythm characterised by left bundle branch block and right axis deviation. Clinical history, physical findings, basic electrocardiogram, chest x ray, and blood tests were within normal limits in all. Holter monitoring, exercise stress test, and electrophysiological study (in three patients) showed that accelerated idioventricular rhythm was mainly bradycardia dependent, easily suppressed by effort and overdrive pacing, and originated from the outflow tract of the right ventricle. The mechanism could be enhanced automaticity. Data from cross sectional echocardiography (in all patients) and from haemodynamic evaluation (in three) identified structural or wall motion abnormalities of the right ventricle or both without appreciable dilatation of the ventricle. Biopsy specimens of the right ventricular endomyocardium showed fibrosis in one patient, fibrosis and fatty infiltration in the second, and pronounced fatty infiltration in the third. These results show that some patients with accelerated idioventricular rhythm have right ventricular abnormalities that are typical of the localised and concealed forms of arrhythmogenic right ventricular dysplasia.

Accelerated idioventricular rhythm in patients without acute myocardial infarction

Accelerated idioventricular rhythm (AIVR) has been reported in patients with acute myocardial infarction, digitalis excess, and subarachnoid hemorrhage, and in patients with rheumatic, primary myocardial, and hypertensive heart disease. Discovery of AIVR in 2 patients without heart disease led us to review reports from 700 Holter monitor studies. Seven patients without recent myocardial infarction were studied retrospectively. Three of the 7 had no evidence of heart disease; 5 of the 7 had abnormalities of the central nervous system. Examples of AIVR show approximation of the sinus rate and ectopic rate; onset and offset occur abruptly or with sinus rate slowing and fusion beats. One patient remained in AIVR for up to 10 minutes accompanied by retrograde atrial capture. The rhythm's acceleration with exercise suggests that it is under autonomic influence, a phenomenon also seen in CNS stimulation studies in dogs. AIVR occurs infrequently in patients without demonstrable heart disease. Our experience suggests a good prognosis, but further study is needed onthe natural history of AIVR in asymptomatic patients and on the necessity of treatment.