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.

Rate-dependent conduction block of the crista terminalis in patients with typical atrial flutter: influence on evaluation of cavotricuspid isthmus conduction block.

BACKGROUND: The crista terminalis (CT) has been identified as the posterior boundary of typical atrial flutter (AFL) in the lateral wall (LW) of the right atrium (RA). To study conduction properties across the CT, rapid pacing was performed at both sides of the CT after bidirectional conduction block was achieved in the cavotricuspid isthmus by radiofrequency catheter ablation. METHODS AND RESULTS: In 22 patients (aged 61+/-7 years) with AFL (cycle length, 234+/-23 ms), CT was identified during AFL by double electrograms recorded between the LW and posterior wall (PW). After the ablation procedure, decremental pacing trains were delivered from 600 ms to 2-to-1 local capture at the LW and PW or coronary sinus ostium (CSO). At least 5 bipolar electrograms were recorded along the CT from the high to the low atrium next to the inferior vena cava. No double electrograms were recorded during sinus rhythm in that area. Complete transversal conduction block all along the CT (detected by the appearance of double electrograms at all recording sites and craniocaudal activation sequence on the side opposite to the pacing site) was observed in all patients during pacing from the PW or CSO (cycle length, 334+/-136 ms), but it was fixed in only 4 patients. During pacing from the LW, complete block appeared at a shorter pacing cycle length (281+/-125 ms; P<0.01) and was fixed in 2 patients. In 3 patients, complete block was not achieved. CONCLUSIONS: These data suggest the presence of rate-dependent transversal conduction block at the crista terminalis in patients with typical AFL. Block is usually observed at longer pacing cycle lengths with PW pacing than with LW pacing. This difference may be a critical determinant of the counterclockwise rotation of typical AFL.

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 from right ventricle late after myocardial infarction.

In summary, this case illustrates how complex VT circuits may be. If the findings of this case are substantiated with additional cases, mapping and radiofrequency energy application from right ventricle would have to be considered in VT with left bundle branch blocks QRS morphology, whenever ablation from the left ventricule is ineffective.

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.

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.

Classification of hypertensive cardiomyopathy.

A clinical pathophysiological classification of hypertensive cardiomyopathy has been established on the basis of the degree to which the heart is affected by chronic, systemic arterial hypertension: Degree I: Asymptomatic patients without left ventricular hypertrophy but with left ventricular diastolic dysfunction according to Doppler mitral inversion relation (E/A < 0.9) or to gamma scintigraphy (peak filling rate reduction < or = 2.7 EDC.s-1. These patients are classified as Group 1. Degree II: Asymptomatic or mildly symptomatic patients (New York Heart Association class I) with echocardiographic left ventricular hypertrophy; classified as Group IIA or IIB according to whether weight-adjusted maximal oxygen uptake is normal or below normal, respectively. Degree III: The basic characteristic is the presence of congestive heart failure with normal ejection fraction (EF > or = 50%). Two subsets can be distinguished on the basis of degree of hypertrophy: Group IIIA, with a mass/volume index > 1.8, and IIIB with a mass/volume index < 1.8. The differences between the two are as follows: patients classified as IIIA had a lower rate of regional ischaemia, a higher ejection fraction, a more frequently audible fourth sound, rarely a third sound and a cardiothoracic ratio < 0.5; IIIB patients had a higher prevalence of regional ischaemia (thallium-positive), a frequently audible third sound and a cardiothoracic ratio > 0.5. Degree IV: This category is characterized by the presence of depressed contractility, which could cause heart failure, by an ejection fraction < 50% and an increase in ventricular volumes. Echocardiography shows increased distance between mitral point E and the septum.

[Right ventricular function and effort tolerance in patients with chronic congestive heart insufficiency. A cross-over double-blind study]. / Función ventricular derecha y tolerancia al esfuerzo en los pacientes con insuficiencia cardíaca congestiva crónica. Estudio cruzado a doble ciego.

We tried to assess the value of both ventricular function changes and its correlation with maximal exercise capacity in patients with chronic heart failure. For this purpose, a double blind crossover study was designed, and the change in the exercise tolerance and both ventricular ejection fraction were evaluated. When compared with digoxin treatment (p less than 0.01) and with a control-period (p less than 0.001), the captopril increases total exercise time significantly. The response of right ventricular ejection fraction was similar. The changes in right ventricular ejection fraction, but not those of left ventricular ejection fraction, correlated with the variations of exercise time (r = 0.67). These facts suggest that right ventricular function is an important determinant of exercise capacity in patients with chronic heart failure and that its behaviour explain, in part, the response to captopril treatment.