Catecholaminergic polymorphic ventricular tachycardia detected by an insertable loop recorder in a pediatric patient with exercise syncopal episodes.

Syncope is a common clinical problem that occurs at all ages and is particularly prevalent in childhood and adolescence. The evaluation of syncope is best approached using the history and physical examination, electrocardiogram and risk stratification to guide further diagnostic tests. Syncope associated with exercise or exertion must be considered dangerous, it can be a predictor of sudden cardiac death and therefore it must be taken seriously. The insertable loop recorder has been proven to be useful in the diagnosis of recurrent syncope in adult patients in whom the cause of the syncope cannot be found by other noninvasive means. We report the first known case of cathecolaminergic polymorphic ventricular tachycardia detected by an insertable loop recorder in a 5-year-old boy with a syncopal history and no structural heart disease.

Analysis of the degree of QRS fusion necessary for its visual detection: importance for the recognition of transient entrainment.

BACKGROUND: Fixed fusion is the hallmark for the demonstration of transient entrainment. However, the degree of accuracy of its recognition on the surface ECG is unknown. The purpose of the present study was to evaluate the ability to detect fusion in the QRS complex. METHODS AND RESULTS: While pacing the ventricles at a fixed rate, a model of ventricular fusion was created by introducing late extra stimuli at a second site. In this model, the presence and degree of fusion are known. Pacing sites were the RV apex, outflow tract, and left ventricle in various configurations. We analyzed 433 QRS complexes with different degrees of fusion (or no fusion) in 21 patients. Each QRS was "read" by three investigators blinded to intracardiac recordings but having a reference QRS with no fusion. There was a statistically significant correlation between the degree of fusion and its recognition. Fusion was detected with a sensitivity of 75% and a specificity of 87%. Fusion was accurately detected in all configurations only when >22% of the QRS was fused. In patients with organic left ventricular disease, fusion was better recognized when the driving pacing site was the left ventricle than when it was a right ventricular site. The interobserver agreement was moderate between two pairs of observers and only fair between the remaining pair. CONCLUSIONS: Our results suggest that an accurate detection of ventricular fusion can only be accomplished when fusion occurs during a significant proportion of the QRS duration. The potential lack of recognition of minor degrees of fusion may produce underdetection of transient entrainment.

[Radiofrequency catheter ablation of ventricular tachycardia in patients without apparent structural cardiopathy]. / Ablación con catéter mediante radiofrecuencia de taquicardias ventriculares en pacientes sin cardiopatía estructural aparente.

BACKGROUND AND PURPOSE: It has been suggested that the efficacy of radiofrequency ablation of idiopathic ventricular tachycardia (VT) is dependent on the site of VT origin, with the efficacy being greater for VTs originating from right ventricle. The electrophysiologic characteristic and the results of radiofrequency catheter ablation of ventricular tachycardia in patients without structural heart disease are reported. Special emphasis was focused to the differences observed in the pace and activating mapping between VTs originating in the right ventricle and those originating from the left ventricle and its possible implications for radiofrequency efficacy. METHODS AND RESULTS: 14 consecutive patients with idiopathic VT (7 women and 7 men, mean age 35 +/- 16 years), 8 originating in the right ventricle (RV) and 6 in the left ventricle (LTV), underwent catheter ablation using radiofrequency energy. The observation of entrainment with fusion in all LV VT suggested that the electrophysiologic mechanism was a reentry, meanwhile the RV VT were due to focal non-reentrant mechanisms. Sites for radiofrequency energy delivery were selected on the basis of pace and activation mapping in all patients less in two patients with incessant VT in whom only activation mapping was performed. 14 VT were mapped. The activation mapping demonstrated isolated presystolic electrograms in the point of origin in all VT arising from the LV. However in RV tachycardias there was continuous activity between presystolic and systolic electrograms, although the prematurity of these electrograms was similar (31 +/- 16 ms vs 33 +/- 9 ms; p = 0.77). Radiofrequency was successful in eliminating 93% of TV (100% RV TV vs 83% LV TV; p = 0.23). No complications were observed. CONCLUSIONS: The results of this study suggest that radiofrequency ablation is highly successful either in right and left ventricles idiopathic tachycardias when pace and activation mapping are used complementary.

Identification of concealed posteroseptal Kent pathways by comparison of ventriculoatrial intervals from apical and posterobasal right ventricular sites.

BACKGROUND: The differential diagnosis of supraventricular tachycardia with concentric atrial activation usually requires the inducibility of sustained tachycardia and needs a complex and time-consuming electrophysiological evaluation. To develop a simple test to establish if ventriculoatrial conduction uses a posteroseptal accessory pathway or the normal conduction system, we compared the ventriculoatrial intervals during right ventricular pacing from apical and posterobasal sites. METHODS AND RESULTS: Continuous pacing was performed from an apical and a posterobasal right ventricular site in 34 patients with retrograde conduction over the normal conduction system (group A) and in 22 patients with conduction over a posteroseptal accessory pathway (group B). During apical pacing, ventriculoatrial intervals in group A (176 +/- 40 milliseconds) were not significantly different than those in group B (197 +/- 47 milliseconds, P = NS). During posterobasal pacing, group B patients had significantly shorter ventriculoatrial intervals than group A patients (158 +/- 46 versus 197 +/- 39 milliseconds, P < .01). The difference between the ventriculoatrial interval obtained during apical pacing and that obtained during posterobasal pacing (ventriculoatrial index) discriminated between the two groups without overlapping: It was positive in all group B patients (39 +/- 19; range, +10 to +70 milliseconds) and negative in all except two group A patients (-21 +/- 13; range, -50 to +5 milliseconds; P < .001). CONCLUSIONS: This ventriculoatrial index can identify accurately and in the absence of tachycardia whether concentric retrograde conduction is proceeding over a posteroseptal accessory pathway or over the normal conduction system.

Ventricular fusion during resetting and entrainment of orthodromic supraventricular tachycardia involving septal accessory pathways. Implications for the differential diagnosis with atrioventricular nodal reentry.

BACKGROUND: Ventricular fusion during transient entrainment of orthodromic atrioventricular reciprocating tachycardias (OAVRT) was originally found to be absent and recently observed only with left ventricular stimulation. However, previous studies were restricted to cases with a left free wall accessory pathway. The hypothesis of the present study was that fusion is likely during resetting and entrainment of OAVRT with right ventricular stimulation if the accessory pathway is septally located, since its insertion is relatively close to the stimulation site. This phenomenon can help in the differential diagnosis with atrioventricular nodal reentry (AVNR). METHODS AND RESULTS: We performed programmed right ventricular stimulation during regular inducible supraventricular tachycardia with concentric atrial activation in 44 patients--20 with OAVRT and 24 with AVNR. Fusion in the ECG morphology of extrastimuli producing resetting was observed in 19 of 19 OAVRT but in 0 of 11 AVNR reset (P < .001). Transient entrainment was demonstrated in all 31 cases undergoing rapid ventricular pacing (14 OAVRT and 17 AVNR). Entrainment with fusion occurred in 13 of 14 OAVRT and in 0 of 17 AVNR (P < .001). Fusion was critically dependent on the coupling intervals or pacing rates, sometimes having a narrow window for its observation. CONCLUSIONS: The relative proximity (conduction time) among pacing site, site of entrance to a reentrant circuit, and site of exit from the circuit to the paced chamber are critical for the occurrence of fusion during resetting and/or entrainment. The presence or absence of fusion during these phenomena can help in the differential diagnosis of certain supraventricular tachycardias.

Treatment of ventricular arrhythmias in patients with hypertrophic cardiomyopathy.

In patients with hypertrophic cardiomyopathy, asymptomatic episodes of non-sustained ventricular tachycardia are frequent and of prognostic significance for sudden cardiac death in adults, particularly in those whose consciousness is impaired. Low-dose amiodarone, found to be beneficial in mildly symptomatic non-sustained ventricular tachycardia, but detrimental in a subgroup with prominent non-arrhythmic symptoms, could be an alternative to an electrophysiological approach in patients with syncope but preserved functional capacity. In cardiac arrest survivors, an electrophysiological approach seems preferable to empiric amiodarone, together with implantation of a defibrillator, at least in those in whom inducible arrhythmias cannot be suppressed.

Prognostic significance of ventricular arrhythmias in the presence of pathological left ventricular hypertrophy.

It is well known that pathological left ventricular hypertrophy, either primary or secondary to cardiac overload, is associated with a high incidence of ventricular arrhythmias and sudden death, and that asymptomatic ventricular arrhythmias seem to be related to a high incidence of sudden death in patients with hypertrophic cardiomyopathy and ischaemic heart disease. However, this association has not been prospectively evaluated in patients with hypertensive LVH, where other factors, such as myocardial ischaemia, can play an important role. More studies are needed in this respect before establishing therapeutic implications.