Repeat cryoablation as a redo procedure for atrial fibrillation ablation: Is it a good choice?

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Medtronic Inc.

Introduction

Catheter ablation of atrial fibrillation, both cryoablation and radiofrequency pulmonary vein isolation, have demonstrated to be safe and effective techniques for treating symptomatic atrial fibrillation as a first procedure. However, about one in three patients may face a redo procedure due to AF recurrence. The most suitable technique for redo is unknown.

Purpose

The aim of this study is to assess the efficacy of cryoballoon AF ablation as a redo technique in patients with prior cryoballoon or radiofrequency AF ablation.

Methods

We analyzed a nation-wide real-world cryoablation registry (RECABA) and compared patients who were referred for a first cryoballoon AF ablation procedure with those who had previously undergone cryoballoon or radiofrequency pulmonary vein isolation. The primary endpoint was AF recurrence during the first year after a 3-month blanking period. We performed survival analysis and built univariate and multivariate cox regression models.

Results

From 1742 patients, 1625 had a 12-month follow-up visit. 1551 (95.45%) underwent a first cryoballoon ablation, whereas 33 (2.03%) had a previous CB ablation performed and 41 (2.52%) a previous RF ablation.

Mean age was 58.6 ±10.4 years and 511 (31.5%) were women. 463 (28.5%) had persistent atrial fibrillation and there were no major clinical differences between groups.

Prior-CB group had a higher share of veins without electrogram visualization, with a median of 100% (IQR 75%-100%), compared to prior-RF group (median 67%, IQR 25%-75%) and first procedure group (median 25%, IQR 0%-50%). Kruskal-Wallis test Chi2=54.35, p<0.0001.

12-month Kaplan–Meier estimate of freedom from AF recurrence after the blanking period was 78.5% (95% CI 76.2% - 80.7%) in the first procedure group, 61.0% (95% CI 41.4% - 75.8%) in the prior-CB and 89.2% (95% CI 73.6% - 95.9%) in the prior-RF group. Log-rank test Chi2=17.49, p<0.0001.

Multivariate cox regression analysis pointed female sex, persistent AF, and prior-CB ablation as independent predictors of AF recurrence. The adjusted HR for AF recurrence of prior-CB ablation vs first-CB ablation was 3.13 (95% CI 1.82 -5.40) and for prior-RF vs first CB-ablation was 1.01 (95% CI 0.51 – 1.97).

Conclusion

Repeat cryoballoon AF ablation shows higher rates of AF recurrences compared to first CB procedures or after prior RF ablation. These data suggest that patients with AF recurrence after CB-ablation have worse arrhythmic outcomes and may benefit from other ablation techniques after a recurrence.

Spanish registry of cardiac resynchronization therapy in adults with congenital heart disease (RETRACCA): clinical outcomes at one year follow-up

Funding Acknowledgements

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Spanish Society of Cardiology

Background

There are limited data about the impact of cardiac resynchronization therapy (CRT) in adults with congenital heart disease (CHD) with conflicting results in patients (P) with systemic right ventricle (SRV).

Objectives

We analyzed the one-year outcomes of adults with CHD implanted with CRT and the impact of CRT in P with SRV as compared with systemic left ventricle (SLV).

Methods

Data were analyzed from the Spanish Registry of CRT in adults with CHD (RETRACCA). This is an observational, ambispective (66 % retrospective), multicenter Registry, including 74 adults with CHD implanted with a CRT device from 6 Spanish centers from 2007 to 2021. Ventricular function was assessed by echocardiography and graded on a four-point ordinal scale. Response to CRT was defined as an improvement in NYHA functional class and/or systemic ventricular ejection fraction by at least one category. In addition to changes in functional class and ventricular function, other outcomes analyzed included mortality, heart transplantation and CRT-related complications.

Results

68 P completed one year of follow-up. Table 1 shows the baseline characteristics of the P prior to CRT. The two main indications for CRT were depressed systolic function of the systemic ventricle with more than 40 % ventricular pacing (69 %) and severely depressed systolic function of systemic ventricle, NYHA FC II-IV and QRS > 150 (18 %). Sixty percent of P received a CRT-ICD, whereas 40 % received a CRT-pacemaker. The approach for CRT system implantation was transvenous in 70 % of the patients, mixed in 21 % and fully epicardial in 9 %. Overall, 43 out of 68 patients (75 %) responded to CRT either by improvement of NYHA FC (56 %) and/or systemic ventricular function (41 %). Compared with baseline, CRT was associated with significant improvement in NYHA FC (p<0.001; figure 1), QRS duration (169±31 vs 150±29; p=0.005), and systemic ventricle systolic function (severe or moderate 80 % vs 58 %; p=0.04). Percentage of responders was similar among patients with a SLV (73 %) and with SRV (81 %; p=0.51). Only pre-implant NYHA FC III-IV was predictive of a positive response in the univariate analysis (OR 3.82; 95 % CI 1.03-14.18). Seven complications occurred at implant (10 %). During the follow-up, there were 8 complications in 7 P: 2 P had heart transplantation, 3 P required hospital admission for decompensation of heart failure, 2 P presented pocket infections and 1 lead malfunction. No differences in complication rates were observed between the systemic LV and systemic RV subgroups.

Conclusions

In this series, at one-year follow-up, CRT resulted in improvement in functional class and/or systemic ventricular function in 75 % of P with adult CHD. The percentages of responders and complications were similar among patients with SLV or SRV.

An electrocardiographic diagnostic model for differentiating right from left ventricular outflow tract arrythmias origin

Background/Introduction

Several ECG signs have been proposed to discern the focal origin of ventricular outflow tract arrhythmias with a transition ≥V3. Their independent predictive value is unclear.

Purpose

The aim of the study is to establish a predictive model of independent ECG parameters to obtain an acute success in right-sided catheter ablation of isolated premature ventricular contractions (PVCs) or ventricular tachycardia (VT) from the ventricular outflow tract with a transition ≥V3.

Methods

We included 122 patients (62 women, mean age 54±16 years) with documented PVCs or VT showing a lower axis and predominantly negative QRS complexes in V1 and V2 who underwent ablation between January 2014 and June 2020. The achievement of acute ablation success from right endocardial positions was assessed. We performed a predictive model by multivariate logistic regression analysis including the following ECG variables associated with a right origin of the ventricular focus in previous studies: Transitional Zone (TZ) index, V2 transition ratio, V2S / V3R index, R-wave duration index, R/S-wave amplitude index in V2, variable coupling interval, and the presence of QS morphology in lead I.

Results

Two independent predictive ECG variables were identified: the V2S / V3R index (odds ratio 1.223; 95% CI, 1.024–1.460; p=0.026) and a coupling interval variability >60 ms (odds ratio 0.307; 95% CI, 0.129 - 0.731; p=0.008). The area under the curve of this model was 0.733 (Picture 1). Arrhythmias with transition in V3 present a greater electroanatomic overlap and, therefore, a higher probability of right failure (59.3% vs 73.5% in arrhythmias with transitions after V3). In these, the V2 transition ratio is useful to predict the origin of the ectopy.

Conclusion

Two easily identifiable ECG variables (the V2S / V3R index and coupling interval variability >60 ms) predict the acute success of a right-sided approach in the ablation of focal ventricular arrhythmias with predominantly negative QRS complexes in V1 and V2.

Funding Acknowledgement

Type of funding sources: None. Predictive accuracy of the ECG model

Long-term outcomes among a cohort of 4296 implantable cardioverter-defibrillator patients: insights from the UMBRELLA study

Background

Large observational real-world studies describing modern implantable cardioverter-defibrillator (ICD) populations with long-term follow-up are lacking.

Purpose

To assess the incidence of arrhythmias in a cohort of contemporary patients undergoing ICD implant from 2005 and 2017 and to analyze the arrhythmic risk and mortality according to their clinical profiles.

Methods

UMBRELLA (NTC01561144) is a prospective, multicentre, nationwide study of ICD patients followed by remote monitoring. All device information was automatically stored through the remote monitoring system and a blinded review of all the stored arrhythmic episodes was performed. The study outcomes were first appropriate ICD therapy and all-cause death.

Results

The study population consisted of 4296 patients (61.9±12.9 years, ischaemic cardiomyopathy (ICM): n=2150, dilated cardiomyopathy (DCM): n=1166, valvular heart disease (VHD): n=119, hypertrophic cardiomyopathy (HCM): n=294, arrhythmogenic right ventricular cardiomyopathy (ARVC): n=71, Brugada syndrome (BS): n=143, long QT syndrome (LQTS): n=43, and adult congenital heart disease (ACHD): n=60)). Primary prevention (PP) was the main indication (n=2758).

During a mean follow-up of 46.6±27.3 months, 16,067 episodes of sustained ventricular arrhythmia (SVA) occurred in 1344 patients. Appropriate ICD therapy was delivered to 85.7% (n=13,767) episodes of SVA in 1173 patients (27.3% of population). A higher risk of first appropriate ICD therapy was observed in VHD (HR: 1.94, 95% CI: 1.43–2.62), ARVC (HR: 1.84, 95% CI: 1.28–2.66), ICM (HR: 1.51, 95% CI: 1.29–1.78), and DCM (HR: 1.28, 95% CI: 1.07–1.53) whereas patients with HCM (HR: 0.72, 95% CI: 0.54–0.96) and BS (HR: 0.25, 95% CI: 0.14–0.45) were at significantly lower risk (Figure 1A). In multivariate analysis (Table 1), age, gender, atrial fibrillation (AF), secondary prevention, LVEF ≤35%, and QRS width emerged as clinical predictors of appropriate ICD therapy, whereas CRT-D correlated with lower risk. An independently higher risk was found in DCM, VHD, and ARVC, and a lower risk in BS patients.

At follow-up, 590 deaths (13.4% of population) were reported. Patients with ICM (HR 3.90, 95% CI: 2.58–5.90), DCM (HR 3.33, CI 95%: 2.18–5.10), and VHD (HR 3.97, CI 95%: 2.25–6.99) had worse prognoses and it was significantly better in BS patients (HR 0.11, 95% CI: 0.01–0.67, p=0.017) (Figure 1B). In multivariate analysis, age, gender, AF, renal failure, diabetes and reduced LVEF, emerged as independent predictors of all-cause death (Table 1).

Conclusions

Irrespective of the aetiology, contemporary ICD patients with an arrhythmic substrate derived from left ventricular systolic dysfunction had a similar risk of ICD life-saving interventions and death.

Funding Acknowledgement

Type of funding sources: None. Table 1Figure 1

2397Lesion-specific risk for sudden cardiac death or life-threatening ventricular arrhythmias in adult congenital heart disease

Background

Risk models for primary prevention strategies in adult congenital heart disease (ACHD) must incorporate the heterogeneous risk for sudden cardiac death (SCD) and life-threatening ventricular arrhythmias (LTVA) as stratified by underlying lesion.

Objectives

To determine lesion-specific risk for SCD and LTVA in ACHD.

Methods

We analyzed 3311 ACHD patients (50% males) prospectively followed-up for 37510 person/years. SCD cases were confirmed by means of the Spanish National Death Registry. In addition, we identified all cases of resuscitated cardiac arrest or ventricular tachycardia requiring cardioversion. According to the incidence rate of the composite end-point of SCD and LTVA, lesions were stratified into four groups of risk. Cumulative freedom from SCD or LTVA in patients at high, moderate, low and very low risk were compared by using Cox regression model with left truncation. The c-index of this lesion-specific risk stratification was calculated by using the β-coefficients. The discriminative ability of this lesion-specific risk stratification was also tested in an external cohort of 203 SCD-LTVA cases and 2287 controls from 20 different centers.

Results

71 patients experienced an event (53 SCD, 18 LTVA). Patients at highest risk (incidence rate >1%) were those with Rastelli procedure, severe coronary abnormalities, complex Fallot and cyanotic patients, either Eisenmenger or non-Eisenmenger; at moderate risk (incidence rate 0.25–1.0%) non-complex Fallot, Mustard/Senning repair, Fontan procedures and congenitally corrected transposition; at low risk (incidence rate 0.1–0.25%) Ebstein anomaly and left heart lesions; and at very low risk (incidence rate <0.1%) left-to-right shunts and right ventricular outflow lesions. The discriminative ability in a multicenter external cohort was excellent (c-index ranged from 0.748 to 0.819 by center).

Lesion-specific risk and C-index

Conclusions

A lesion-specific risk stratification based on the incidence rate of SCD and LTVA was performed and validated. This approach could result in a more individualized risk assessment.

Acknowledgement/Funding

Instituto de Salud Carlos III, Ministerio de Economía y Competividad, Spain (Exp PI14/02099 and PI17/01327) and co-financed by FEDER

PREVENTION-ACHD: PRospEctiVE study on implaNTable cardioverter-defibrillator therapy and suddeN cardiac death in Adults with Congenital Heart Disease; Rationale and Design

BACKGROUND

Many adult congenital heart disease (ACHD) patients are at risk of sudden cardiac death (SCD). An implantable cardioverter-defibrillator (ICD) may prevent SCD, but the evidence for primary prevention indications is still unsatisfactory.

STUDY DESIGN

PREVENTION-ACHD is a prospective study with which we aim to prospectively validate a new risk score model for primary prevention of SCD in ACHD patients, as well as the currently existing guideline recommendations. Patients are screened using a novel risk score to predict SCD as well as current ICD indications according to an international Consensus Statement. Patients are followed up for two years. The primary endpoint is the occurrence of SCD and sustained ventricular arrhythmias. The Study was registered at ClinicalTrials.gov (NCT03957824).

CONCLUSION

PREVENTION-ACHD is the first prospective study on SCD in ACHD patients. In the light of a growing and aging population of patients with more severe congenital heart defects, more robust clinical evidence on primary prevention of SCD is urgently needed.

[Characteristics of suicides in Navarra by gender (2010-2013)]

OBJECTIVE

To determine the number of suicides and the main social and demographic characteristics, time frames and methods involved during the period 2010-2013 in Navarra by gender.

METHODS

A study of the Electronic Clinical Records provided by Navarra's Healthcare Service in which suicides in Navarra are detailed.

RESULTS

One hundred and eighty individuals committed suicide. The number of suicides remained stable: 41 in 2010, 51 in 2011 and 44 in 2012 and 2013. Seventy-five point four percent were males (n=136) and 24.6 % (n=44) were females. In the 13 to 26 age group, 12 (92.3%) out of 13 suicides were committed by males. In terms of employment status, 49.3% (n=70) were pensioners. The highest rate of suicides was reached in summer (n=71) and spring (n=39). Monday was the day with the highest rate of suicides (n=37) and the time period between 8:00 and 12:00 hours was when the highest number of suicides (n=80) took place. The most usual ways of committing suicide were hanging (n=80), falling from a height (n=41) and pharmacological overdose (n=23). Males used violent methods more frequently. It is necessary to highlight the fact that in some of the sociodemographic characteristics there was up to 60% of cases without enough information.

CONCLUSION

The results obtained show some specific features of the phenomenon of suicide in Navarra that should be considered for its prevention. Furthermore, the implementation of effective protocols of data collection is recommended to develop prevention strategies.

Reappraisal of classical electrocardiographic criteria in detecting accessory pathways with a strict para-Hisian location

BACKGROUND

Identification of electrocardiographic (ECG) criteria for para-Hisian accessory pathways (APs) is based on a small series of patients. The presence of a negative delta wave in leads V(1) and V(2) has been suggested as an ECG marker of this AP location.

OBJECTIVE

To validate these ECG findings in a large series of patients with strict invasive criteria for that location.

METHODS

We included 105 patients (39 women, 66 men; mean age 26 ± 12 years, range 5-82 years) with an ECG pattern compatible with preexcitation through an anteroseptal or midseptal AP following established ECG criteria. A para-Hisian AP was defined when the location of its successful catheter ablation coincided with either the largest recordable His bundle electrogram or a His bundle potential of>0.1 mV. Patients without that definition were included in the control group.

RESULTS

A para-Hisian location of the AP was found in 52 patients. AP locations of the remaining 53 patients (control group) were anteroseptal (n = 39), midseptal (n = 9), and fasciculoventricular (n = 5). A negative delta wave in leads V(1) and V(2) was observed in 13 patients with para-Hisian APs (sensitivity 25%; specificity 92%). However, the sum of initial r-wave amplitudes in those leads was<0.5 mV in 44 of the patients with para-Hisian APs and in 13 patients of the control group (sensitivity 85%; specificity 75.5%; area under receiver-operator characteristic curve 0.85).

CONCLUSIONS

The presence of negative delta waves in leads V(1) and V(2) indicates a poor sensitivity and high specificity to detect APs with a strict definition of para-Hisian location. The sum of initial r-wave amplitudes in those ECG leads could be a useful, adjunctive marker in the noninvasive identification of these challenging APs.

Decremental atriofascicular accessory pathway with bidirectional conduction: delineation of atrial and ventricular insertion by radiofrequency current application

A 17-year-old girl with a corrected complex congenital heart disease and recurrent episodes of supraventricular tachycardia was referred for catheter ablation. Electrophysiologic studies revealed the presence of an accessory pathway (AP) with bidirectional conduction and decremental properties. We demonstrated a course parallel to the node-His AV conduction system. Transient abolition of the bidirectional conduction through the AP was obtained by radiofrequency application to the ventricular insertion located in the distal right bundle branch and to the atrial insertion, located in the mid-anterior atrial septum. Radiofrequency application at the low anterior atrial septum, above the His bundle, successfully abolished AP conduction without affecting AV nodal conduction. Demonstration of the course and insertions of the AP, its bidirectional decremental conduction properties, and the association with a complex congenital heart disease are exceptional and interesting findings and raise the possibility of an accessory AV node with a parallel conduction pathway to the right bundle branch.

Bundle-branch reentry and the postpacing interval after entrainment by right ventricular apex stimulation: a new approach to elucidate the mechanism of wide-QRS-complex tachycardia with atrioventricular dissociation

BACKGROUND

Diagnosis of bundle-branch reentry ventricular tachycardia (BBR-VT) by the standard approach is challenging, and this may lead to nonrecognition of this tachycardia mechanism. Because the postpacing interval (PPI) after entrainment has been correlated with the distance from the pacing site to the reentrant circuit, BBR-VT entrainment by pacing from the right ventricular apex (RVA) should result in a PPI similar to the tachycardia cycle length (TCL). This factor may differentiate BBR-VT from other mechanisms of wide-QRS-complex tachycardia with AV dissociation, such as myocardial reentrant VT (MR-VT) or AV nodal reentrant tachycardia (AVNRT), in which the circuit is usually located away from the RVA.

METHODS AND RESULTS

Transient entrainment by RVA pacing was attempted in 18 consecutive BBR-VTs and finally achieved in 13. Results were compared with those found in 59 consecutive MR-VTs and 50 consecutive AVNRTs. The mean PPI-TCL difference was significantly (P:<0.0001) shorter in the BBR-VT group (9+/-11 ms) than in the MR-VT (109+/-48 ms) and the AVNRT (150+/-29 ms) groups. No BBR-VT showed a PPI-TCL >30 ms (range -12 to 24 ms). Except for 2 MR-VTs, no MR-VT (range 21 to 211 ms) or AVNRT (range 100 to 215 ms) showed a PPI-TCL <30 ms.

CONCLUSIONS

A PPI-TCL >30 ms, after entrainment by RVA stimulation, makes BBR-VT unlikely. Conversely, a PPI-TCL <30 ms is suggestive of BBR-VT but should lead to further investigation by use of conventional criteria.

Ablation of idiopathic ventricular tachycardia by bipolar radiofrequency current application between the left aortic sinus and the left ventricle

BACKGROUND

Failure to ablate idiopathic ventricular outflow tract tachycardia by radiofrequency current is not uncommon and suggests that non-standard approaches may be required to map and suppress idiopathic ventricular tachyarrhythmias in some patients.

METHODS AND RESULTS

Left and right ventricular activation and pace mapping proved inadequate for radiofrequency application in a patient with idiopathic ventricular outflow tract tachycardia. Presystolic activity was recorded at the left aortic sinus of Valsalva, and the QRS complex recorded at this location during pacing showed few differences compared with that recorded during tachycardia. Radiofrequency current application at this site transiently suppressed the tachycardia. Following new mapping of the left ventricle outflow tract, radiofrequency application just below the aortic valve in close proximity to the previous aortic application site transiently abolished the arrhythmia. Finally, bipolar radiofrequency application between the distal electrode of the aortic catheter and the distal electrode of a second catheter placed in the left ventricular subaortic area permanently suppressed the tachycardia.

CONCLUSION

Bipolar radiofrequency application between the aortic sinus of Valsalva and the left ventricle could be an alternative approach in occasional patients with idiopathic ventricular outflow tract tachycardia resistant to conventional left ventricular and aortic root unipolar radiofrequency application.

[Cardioinhibitory vagal response not related to pain, and induced by radiofrequency application during ablation of right posteroseptal accessory pathway]

Inappropriate sinus tachycardia is the most common arrhythmia induced by radiofrequency energy delivery in the posteroseptal area. It has been suggested that this could be secondary to parasymphathetic nerve injury. We report a patient with extreme sinus bradycardia and PR interval prolongation induced by radiofrequency energy delivered in the coronary sinus ostium area, but not related to any other stimulus. The most probable mechanism of the disorder was transient stimulation of the vagal afferent nerve fibers located in this anatomical area.

[Oblique orientation of the accessory pathway demonstrated by radiofrequency application]

Activation mapping of atrial and ventricular insertion has suggested an oblique orientation of some accessory pathways. However, this aspect has not been demonstrated by radiofrequency application. This report presents two patients with Wolff-Parkinson-White syndrome and an accessory pathway with bidirectional conduction and oblique orientation. The accessory pathway oblique orientation was demonstrated by transient and permanent conduction abolition following radiofrequency application in two separate ventricular and atrial sites. These findings may explain the failure to ablate accessory pathway by radiofrequency application in the ventricular side of the mitral annulus guided by retrograde atrial activation occasionally observed in patients with a concealed accessory pathway.

[Sudden cardiac death out of the hospital and early defibrillation]

Since most sudden cardiac death victims show neither symptoms before the event nor other signs or risk factors that would have identified them as a high risk population before their cardiac arrest, emergency out-of-hospital medical services must be improved in order to obtain a higher survival in these patients. Early defibrillation is an essential part of the chain of survival that also includes the early identification of the victim, activation of the emergency medical system, immediate arrival of trained personnel who can perform basic cardiopulmonary resuscitation and early initiation of advanced cardiac life support that would raise the survival rate for sudden cardiac arrest victims. Many studies have demonstrated the enormous importance of early defibrillation in patients with a cardiac arrest due to ventricular fibrillation. The most important predictor of survival in these individuals is the time that elapses until electric defibrillation, the longer the time to defbrillation the lower the number of patients who are eventually discharged. Multiple studies have demonstrated that automatic external defibrillation will reduce the time elapsed to defibrillation and thus improve survival. For these reason, public access defibrillation to allow the use of automatic external defibrillators by minimally trained members of the lay public, has received increasing interest on the part of a groving number of companies, cities or countries. The automatic external defibrillaton, as performed by a lay person is being investigated. The liberalization of its application, if is demonstrated to be effective, will need to be accompanied by legal measures to endorse it and appropriate health education, probably during secondary education.

Transient entrainment of bundle-branch reentry by atrial and ventricular stimulation: elucidation of the tachycardia mechanism through analysis of the surface ECG

BACKGROUND

Different responses to entrainment have been reported in relation to the pacing site of a variety of tachycardias. However, transient entrainment of bundle-branch reentrant tachycardia (BBRT) has not been investigated systematically.

METHODS AND RESULTS

We attempted entrainment of 13 BBRTs in 9 patients by pacing first the right ventricle and then the right atrium. The initial pacing cycle length (CL) was 10 ms faster than the tachycardia CL. Subsequent pacing sequences were performed with 5- to 10-ms CL decrements until tachycardia termination or loss of postatropine 1:1 AV conduction. Both full ventricular-paced and AV-conducted QRS complex references were obtained during sinus rhythm pacing from the same sites and with similar CL as during entrainment. Transient entrainment was achieved by ventricular and atrial stimulation in 11 and 8 tachycardias, respectively. Constant fusion was always present during entrainment by ventricular stimulation. There was no change in the QRS complex (orthodromically concealed fusion) during entrainment by atrial stimulation in 6 of 6 tachycardias with left bundle-branch block morphology and in 1 of 2 tachycardias with right bundle-branch block morphology.

CONCLUSIONS

BBRT, especially if it has a left bundle-branch block morphology, can be differentiated from other wide-QRS-complex tachycardia mechanisms through analysis of the ECGs recorded during tachycardia entrainment by atrial and ventricular stimulation. This diagnostic approach may be especially useful when it is difficult to record a stable or sufficiently sized His bundle electrogram or when spontaneous changes in the ventricular CL precede similar changes in the His bundle CL.

Randomized, prospective comparison of four burst pacing algorithms for spontaneous ventricular tachycardia

"Less aggressive" burst stimulation is more effective in terminating spontaneous monomorphic ventricular tachycardia with a lesser acceleration rate. Higher ventricular tachycardia cycle length and use of 91% coupling interval were independent predictors for pacing termination.

Mechanisms of sustained ventricular tachycardia in myotonic dystrophy: implications for catheter ablation

BACKGROUND

Ventricular arrhythmias have been documented and linked to the high incidence of sudden death seen in patients with myotonic dystrophy. However, their precise mechanism is unknown, and their definitive therapy remains to be established.

METHODS AND RESULTS

We studied 6 consecutive patients with myotonic dystrophy and sustained ventricular tachycardia by means of cardiac electrophysiological testing. Particular attention was paid to establish whether bundle-branch reentry was the tachycardia mechanism, and when such was the case, radiofrequency catheter ablation of either the right or left bundle branch was performed. Clinical tachycardia was inducible in all patients and had a bundle-branch reentrant mechanism. In 1 patient, 2 other morphologies of sustained tachycardia were also inducible, neither of which had ever been clinically documented, and both had a bundle-branch reentrant mechanism. Ventricular tachycardia was no longer inducible after bundle-branch ablation, except for a nonclinically documented and nonsustained ventricular tachycardia in the only patient who had apparent structural heart disease.

CONCLUSIONS

A high clinical suspicion of bundle-branch reentrant tachycardia is justified in patients with myotonic dystrophy who exhibit wide QRS complex tachycardia or tachycardia-related symptoms. Because catheter ablation will easily and effectively abolish bundle-branch reentrant tachycardia, myotonic dystrophy should always be considered in patients with sustained ventricular tachycardia. This is especially true if no apparent heart disease is found.

[Current indications for implantable automatic defibrillators]

Since the first implantation in man in 1980 implantable cardioverter defibrillator technology has greatly improved and the number of devices implanted has increased considerably in recent years. Non-thoracotomy lead systems and biphasic shocks are now the approach of choice, offering nearly a 100% success rate. This paper version reviews the current indications for the implantation of implantable cardioverter defibrillator and is an upgraded of an article previously published by the Arrhythmia's Section of the Spanish Society of Cardiology. Recommendations for qualification of centres implanting defibrillators and follow up are also addressed.

Implantable cardioverter defibrillator as therapeutic option for sudden cardiac death secondary to severe coronary vasospasm

We report a case of a patient with angina at rest followed by sudden cardiac death secondary to ventricular fibrillation. Cardiac catheterization did not show significant coronary stenosis but after an acetylcholine test, a severe coronary spasm was induced. Despite intensive medical therapy, vasospasm was not prevented. Finally, the patient received an implantable cardioverter defibrillator (ICD) to avoid the risk of sudden cardiac death. In our opinion, ICD in addition to medical therapy may be useful in patients with sudden cardiac death secondary to coronary vasospasm.

Unipolar mapping and magnetic resonance imaging of "idiopathic" right ventricular outflow tract ectopy

Radiofrequency catheter ablation of symptomatic ventricular ectopy guided by unipolar mapping was successfully accomplished at the right ventricular outflow tract in a patient who did not exhibit apparent structural heart disease. A "QS" morphology with a fast slope of the downstroke deflection at the successful ablation site was observed on the unipolar electrogram. Focal thinning of the lateral wall of the right ventricular outflow tract was shown in the magnetic resonance image, similar to that reported in patients with "idiopathic" right ventricular outflow tract tachycardia.

Mechanism and location of atrial flutter in transplanted hearts: observations during transient entrainment from distant sites

OBJECTIVES

This study was designed to elucidate the location and mechanism of typical atrial flutter in the transplanted heart.

BACKGROUND

Although the F wave morphology in atrial flutter is similar in nontransplanted and transplanted hearts, the surgical incision needed for the atrial anastomosis may create a distinct electrophysiologic substrate of atrial flutter.

METHODS

Entrainment from the lateral wall of the right atrium and interatrial septum was used to determine the location of atrial flutter in five patients with a transplanted heart and six patients with a nontransplanted heart. The difference between the first postpacing interval (FPPI) and the flutter cycle length (FCL) was used as an index of proximity to the circuit.

RESULTS

In the transplant group, the FPPI was equal to the FCL at sites located close to the tricuspid annulus (TA); the mean differences (+/-SD) were 1 +/- 5 and -1 +/- 2 ms at the lateral wall and interatrial septum, respectively. However, from sites close to the surgical incision at the lateral wall and at the interatrial septum, these differences were significantly longer (29 +/- 12 and 27 +/- 9 ms, respectively, p < 0.05). In the nontransplant group, the FPPI was similar to the FCL at points in the lateral wall and interatrial septum close to the TA (mean difference 7 +/- 6 and 6 +/- 11 ms, respectively) and at sites close to the crista terminalis (CT) in the lateral wall (mean difference 4 +/- 4 ms). However, in sites separated from the TA at the interatrial septum the difference was markedly longer (35 +/- 11 ms, p < 0.05).

CONCLUSIONS

Atrial flutter in transplanted hearts may best be explained by macroreentry around the tricuspid ring. In non-transplanted hearts a different structure (perhaps the CT?) may be the basis for atrial flutter at the lateral wall.