Transplanted fetal cardiomyocytes as cardiac pacemaker.

BACKGROUND: While morphologic integration of transplanted fetal cardiomyocytes into the ventricular myocardium is a well-known fact, no studies have yet shown transplanted cells to coherently contribute to contraction and electrical excitation of the host myocardium. The aim of this study was to prove the hypothesis that by transplanting cardiomyocytes with a higher intrinsic rhythmic rate into the myocardium of the left ventricle, these cells could act as an ectopic pacemaker by functional coupling with host cardiomyocytes. METHODS AND RESULTS: Dissociated fetal canine atrial cardiomyocytes including sinus nodal cells were delivered into the free wall of the left ventricle of adult canine X-linked muscular dystrophy dogs (n=2). These dogs fail to express Dystrophin in both cardiac and skeletal muscle. In the control group (n=2) fetal skin fibroblasts were used for grafting. A total of 3-4 weeks after transplantation the dogs underwent catheter ablation of the atrioventricular node (AV-node) and subsequent electrophysiological mapping studies. Transplanted cells were identified by Dystrophin immunoreactivity, indicating survival and morphological integration in the recipient heart. The expression of Connexin 43 between donor and recipient cells suggested formation of gap junctions between injected and host cardiomyocytes. After catheter ablation of the AV-node, a ventricular escape rhythm emerged driving the pace of the heart and originating from the labeled transplantation site. This effect could not be observed in the control group (n=2). CONCLUSIONS: The results constitute the first observation of phenomena indicating electrical and mechanical coupling between allogeneic donor cardiomyocytes and recipient myocardium in-vivo. Further experiments are necessary to evaluate the technique as a potential therapy for atrioventricular block.

Dual-loop circuits in postoperative atrial macro re-entrant tachycardias.

BACKGROUND: Patients may develop dual-loop re-entrant atrial arrhythmias late after open-heart surgery, and mapping and catheter ablation remain challenging despite computer-assisted mapping techniques. OBJECTIVES: The purpose of the study was to demonstrate the prevalence and characteristics of dual-loop re-entrant arrhythmias, and to define the optimal mapping and ablation strategy. METHODS: 40 consecutive patients (mean (SD) age 52 (12) years) with intra-atrial re-entrant tachycardia (IART) after open-heart surgery (with an incision of the right atrial free wall) were studied. Dual-loop IART was defined as the presence of two simultaneous atrial circuits. After an abrupt tachycardia change during radiofrequency ablation, electrical disconnection of the targeted re-entry isthmus from the remaining circuit was demonstrated by entrainment mapping. Furthermore, the second circuit loop was localised using electroanatomical mapping and/or entrainment mapping. RESULTS: Dual-loop IART was demonstrated in eight (20%, 5 patients with congenital heart disease, 3 with acquired heart disease) patients. Dual-loop IART included an isthmus-dependant atrial flutter combined with a re-entry related to the atriotomy scar. The diagnosis of dual-loop IART required the comparison of entrainment mapping before and after tachycardia modification. Overall, 35 patients had successful radiofrequency ablation (88%). Success rates were lower in patients with dual-loop IART than in patients without dual-loop IART. Ablation failures in three patients with dual-loop IART were related to the inability to properly transect the second tachycardia isthmus in the right atrial free wall. CONCLUSIONS: Dual-loop IART is relatively common after heart surgery involving a right atriotomy. Abrupt tachycardia change and specific entrainment mapping manoeuvres demonstrate these circuits. Electroanatomical mapping appears to be important to assist catheter ablation of periatriotomy circuits.

Bundle branch re-entry ventricular tachycardia in a patient with complete heart block.

A 58-year-old male patient presented episodes of palpitations in the context of atrioventricular block treated by a dual-chamber pacemaker. Clinical and electrophysiological studies identified the tachyarrhythmia to be bundle branch re-entrant ventricular tachycardia, which was successfully treated by radiofrequency ablation of the proximal right bundle branch.

Impact of arrhythmias on health-related quality of life in adults with congenital cardiac disease.

BACKGROUND: Health-related quality of life in adults with congenital cardiac disease appears to be impaired, but the determinants of this alteration remain largely unknown. The aim of our study was to examine the impact of arrhythmias on quality of life in patients late after the atrial redirection operation for transposition, or after complete correction of tetralogy of Fallot. PATIENTS AND METHODS: We enrolled 32 patients with transposition, and 35 patients with tetralogy of Fallot, in a prospective study. Quality of life was assessed using RAND-36 questionnaires. Quality of life data were compared with those of an age-matched control population. Patients underwent 24-hour and 7-day electrocardiographic recordings, echocardiography, and exercise testing. RESULTS: Patients without arrhythmias had quality of life comparable to that of the general population. All 8 domains in the questionnaire showed scores 22 to 51 percent lower in 12 patients with atrial tachyarrhythmias, and/or sinus nodal dysfunction, requiring insertion of a pacemaker in comparison with 55 patients without arrhythmias. In patients with transposition, low scores were not only associated with arrhythmias, but also correlated with impaired exercise capacity. CONCLUSIONS: Atrial tachyarrhythmias, and sinus nodal dysfunction, requiring insertion of a pacemaker, were associated with impaired quality of life in adults late after atrial surgical correction of transposition or correction of tetralogy of Fallot.