BRIEF REPORT

Catheter ablation in Patients with Electrical storm. The Calm after the Tempest

Ablación por catéter en pacientes con tormenta eléctrica. La calma tras la tempestad

 

CLAUDIO HADID^{MTSAC, 1, 2, 3, 4}, DAMIÁN AZOCAR^{MTSAC, 3}, DARÍO DI TORO^{MTSAC, 1, 2}, SEBASTIÁN GALLINO†, 4, SERGIO DUBNER^{MTSAC, 3}, CARLOS LABADET^{MTSAC, 1, 2 3}

Hospital General de Agudos “Dr. Cosme Argerich”. Electrophysiology Section, Cardiology Division

^MTSAC Full Member of the Argentine Society of Cardiology

^† To apply as Full Member of the Argentine Society of Cardiology

¹ Hospital General de Agudos “Dr. Cosme Argerich”. Buenos Aires, Argentina
² Hospital Universitario CEMIC. Buenos Aires, Argentina
³ Clínica y Maternidad Suizo-Argentina. Buenos Aires, Argentina
⁴ Instituto Médico Quirúrgico Garat. Concordia, Entre Ríos, Argentina

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ABSTRACT

Background: Catheter ablation (CA) has been shown to be effective in patients with recurrent ventricular tachycardia (VT); how-ever, its role in patients with electrical storm (ES) has not been studied in randomized trials. Objective: The aim of this study was to analyze ES cases treated with CA.
Methods: This was a retrospective analysis of patients treated with CA for ES due to sustained monomorphic VT (SMVT). Procedure success was defined as lack of inducible VT at the end of ablation, partial success as the induction of non-clinical VT and failure as inducible clinical V T.
Results:Sixteen procedures were performed in 14 patients: 10 successful, 3 partially successful and 3 failures. All patients were free from ventricular arrhythmia immediately after ablation. Ten patients (71.4%) were free from VT and 86.7% free from ES [8 (3-30)-month follow-up]. Five patients (35.7%) died from causes unrelated to arrhythmia.
Conclusions: Catheter ablation is associated with acute suppression of VT in all patients with ES due to SMVT and with a recurrence-free outcome in most of them.

Key words: Electrical Storm - Catheter Ablation - Ventricular Tachycardia

RESUMEN

Introducción: La ablación por catéter (AC) ha demostrado que es beneficiosa en pacientes con taquicardia ventricular (TV) recur­rente, pero su rol en pacientes con tormenta eléctrica (TE) no se ha estudiado en ensayos aleatorizados. Objetivo: Analizar los casos de TE tratados con AC.
Material y métodos: Análisis retrospectivo de pacientes con TE debida a TV monomorfa sostenida (TVMS) tratados mediante AC. Se definió éxito del procedimiento a la ausencia de TV inducible al final de la ablación, éxito parcial a la inducción de TV no clínica y no éxito a la inducibilidad de la TV clínica.
Resultados:Se realizaron 16 procedimientos en 14 pacientes: 10 exitosos, 3 éxito parcial y 3 no exitosos. Todos los pacientes evolucionaron sin arritmia ventricular inmediatamente posablación. Diez pacientes (71,4%) evolucionaron sin TV y el 86,7% sin TE [seguimiento 8 (3-30) meses]. Cinco pacientes (35,7%) murieron de causa no arrítmica.
Conclusiones: La AC se asocia con una supresión aguda de la TV en todos los pacientes con TE debida a TVMS y con una evolución sin recurrencia en la mayoría de ellos.

Palabras clave: Tormenta eléctrica - Ablación por catéter - Taquicardia ventricular

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Abbreviations

 

AAD	Antiarrhythmic drugs	ICD       Implantable cardioverter defibrillator
AF	Atrial fibrilation	LVEF     Left ventricular ejection fraction
CA	Catheter ablation	SMVT Sustained monomorphic ventricular tachycardia
Es	Electrical storm	VT        Ventricular tachycardia

 

INTRODUCTION

The implantable cardioverter defibrillator (ICD) significantly improves survival of patients with sustained ventricular arrhythmia, but the recurrence of ventricular tachycardia (VT) or ventricular fibrillation (VF) still remains a cause of death. (1, 2) Electrical storm (ES) is characterized by 3 episodes of VT/VF (sepa-rated by >5 minutes) in 24 hours, requiring intervention for its interruption (usually ICD discharge). (3) It is more common in patients with ICD as second-ary prevention and is associated with poor short- and midterm prognosis. (4-6) It is a sometimes dramatic clinical situation, in which recurrent VT/VF episodes, the necessary discharges to interrupt them and the intravenous administration of antiarrhythmic drugs (AAD), detrimental to cardiac function, contribute to rapid clinical deterioration. Catheter ablation (CA) has proven to be beneficial in patients with recurrent VT, but its role in patients with ES has not been studied in randomized trials. The aim of this study was to analyze ES cases due to sustained monomorphic VT (SMVT) treated with CA.

METHODS

A review was done of all patients with structural heart dis-ease who presented with ES due to SMVT treated with CA between December 2010 and November 2014. Ablation and follow-up clinical data were analyzed. Procedural success was defined as the absence of inducible VT at the end of the procedure; partial success as induced VT different only from clinical VT and no success as induced clinical VT (the term clinical VT refers to spontaneous VT presented by the pa-tient before ablation).

statistical analysis

Discrete variables were expressed as percentages and con-tinuous variables as median and interquartile range (25%-75%). The paired-sample Wilcoxon signed-rank test was used to compare continuous variables. A p value <0.05 was considered statistically significant. SPSS v.20-Statistics soft­ware package was used for statistical analyses.

Ethical considerations

The protocol was assessed and approved by the Institutional Review Committee.

RESULTS

Fourteen patients (13 men) with mean age 64.5 years (56 to 71.2) and 27.5% (22-37) left ventricular ejection fraction (LVEF) were analyzed. The etiology of the heart disease was coronary (n=6), chagasic (n=4), hypertensive (n=2) and idiopathic (n=2). All patients had an implanted ICD (3 single chamber, 8 dual chamber and 3 biventricular) as secondary (13 patients) or primary (1) prevention of sudden death.

All patients had SMVT, with 475 ms cycle length (382-560). Two patients presented with 2 clinical VT with dif-ferent morphology. Patients had 24.5 (15-29) stored VT epi-sodes and received 9 (6-17) ICD discharges during the 5 days prior to CA, except for 1 patient who presented with ES one month before the procedure (Figure 1A ).

Sixteen CA procedures were performed (2 patients need-ed a second procedure): 2 with fluoroscopic guidance and 14 with three-dimensional mapping system (13 EnSite-NAVX, St. Jude Medical, 1 CartoXP, Biosense-Webster). Cardiac ab-lation was performed with 8-mm-tip ablation catheter in 6 cases and 3.5-mm-tip externally irrigated catheter in 10 cases using retroaortic (12), transeptal (3) or double (1) approach. Ablation was guided by electrophysiological mapping dur-ing VT in 10 cases or by anatomical substrate due to poorly tolerated VT in 6 cases. For substrate ablation, regions of diseased tissue (local electrocardiogram voltage between 0.5 mV and 1.5 mV) and scar tissue (<0.5 mV) were identified during sinus rhythm or continuous ventricular stimulation. Radiofrequency was applied in areas with scar-related tissue that topographically coincided with VT origin (according to ECG) and in which abnormal electrograms were recorded (late, fractionated). Although poorly accurate in reentrant arrhythmias, local stimulation (pacemapping) can reproduce VT morphology if the ablation catheter is positioned at the exit site of the VT circuit, thus guiding radiofrequency ap-plications. Activation mapping was performed during VT to determine the VT circuit and its relationship with myocardi-al scars, and ventricular overstimulation during tachycardia to restore entrainment and evaluate its response. Entrain-ment maneuvers were performed when presystolic or meso-diastolic potentials were registered during VT. Sites where entrainment with concealed fusion was achieved (QRS dur-ing entrainment equal to QRS during VT) accompanied by a post-stimulation interval equal to the VT cycle±30 ms, and/ or spike stimulation to QRS interval equal to the local elec-trogram to QRS interval during VT±20 ms, were considered suitable to apply radiofrequency. The two last parameters indicate that the ablation catheter is positioned within the VT circuit and the concealed fusion is consistent with a critical zone of the circuit, “surrounded” by scar tissue. (7) In 8/10 procedures guided by electrophysiological mapping (performed with three-dimensional navigation) substrate ablation was added before ending the procedure (Table 1).
Fig. 1. a. List of VT episodes stored in the cardioverter defibrillator obtained at the end of follow-up (patient 3). Note the absence of arrhythmia after ablation performed on 11/26/2010. B: Voltage map (EnSite-Navx) showing scar area at baseline posterolater-al level in patients with Chagas cardiomyopathy (patient 3). In the bottom panel VT disruption is observed during radiofrequency application in that region

Ten (62.5%) CA were successful, in 3 (18.8%) partial success was obtained and 3 (18.8%) were unsuccessful (2 of them were second procedures). Only one complication (femo­ral pseudoaneurysm resolved with mechanical compression) was observed. All patients recovered without ventricular ar-rhythmia immediately after ablation. (Figure 1 B)

Follow up

After 8 (3-30) follow-up months, 10 patients (71.4%) remain free from VT/VF. The remaining 4 patients presented VT re-currence at 10 days, and 6, 10 and 16 months. In 3 cases, CA was successful and 1 was unsuccessful. Two of them re-curred as ES and underwent a second procedure, resulting in 85.7% of patients without ES at follow-up. A non-signif-icant increase in LVEF after CA (43% vs. 27.5%; p=0.066) was observed.

Five patients (35.7%) died: 4 due to heart failure and 1 due to endocarditis 4 months post-ablation. Only one of them had presented recurrence and no death was caused by arrhythmia.

DISCUSSION

To our knowledge, this is the first report of a series of pa-tients with ES treated with CA in our country. The results of this study show that CA allows immediate remission of the VT/VF episodes (main objective of ablation in patients with ES) in all patients with ES due to SMVT and a mid-term out-come without ES in 85.7% of cases, and without ventricular arrhythmia in 7 out of 10 patients. The detrimental effect of the incessant VT and ICD discharges on ventricular function worsens the hemodynamic status of these patients and pro­motes more arrhythmic events, creating a “vicious circle” effect. Suppressing acute episodes of VT/VF achieved with CA could contribute to stop the progression of the hemodynamic deterioration that may lead these patients to death in a few days. The mortality observed in our series (35% in the midterm) reflects the severity of patients with ES and is similar to that published internationally. (6, 8, 9) Four patients had VT/VF during follow-up without arrhythmic mortality. This recurrence rate (28.6%) is comparable to that reported in other series (10, 11) and may be favored, in part, by the progression of the heart disease.

Table 1. Patient characteristics

 

Electrical storm has been identified as an independent risk factor for death, compared with patients with history of VT/VF without ES and patients without history of VT. (6) There are some communications about the benefits of CA in these patients, although with no reduction in mortality. Carbucicchio et al. reported a survival rate of 92% without ES and of 66% without VT in 95 patients treated with CA. (10) In another series of 50 patients treated with CA, 84% remained free from ES episodes and 48% with no VT recur-rence with more than one ablation procedure. (8) In both studies, ES recurrence was associated with higher mortality.

As in our series, another study evaluated ES cases only due to VTMS, although in patients with nonischemic cardio-myopathy. (11) On longer follow-up, they reported 61.5% of patients free from VT. The recurrence rate was significantly higher after ablation with partial success. We found no relationship between the outcome of ablation and recurrence or death.

A recent study retrospectively compared CA or conservative treatment in 52 patients with ES due to SMVT. (9) Cardiac ablation reduced the recurrence of ES only in patients with LVEF >25%. Postablation AAD prescription was not associated with lower ES recurrence. Interestingly, the au-thors did not report ventricular arrhythmia-free survival during follow-up.

limitations

This is a retrospective study of patients with ES only due to VTMS without comparing with a control group. We have no information regarding medically treated patients and those treated with polymorphic VT or V F. Follow-up time is short. However, we believe that the central objective of CA in these patients is to stop VT episodes and interrupt the ES status. In addition to achieving an immediate remission of arrhythmic events in all patients, 71.4% remains without VT/VF in the follow-up period.

Finally, although ICD programming was not standardized, a monitoring area for the detection of slow VT in all post-ablation patients was added. Notwithstanding, there have been episodes of VT ignored by the ICD, a fact which cannot be ruled out.

CONCLUSIONS

Cardiac ablation is associated with acute VT/VF suppression in all patients with ES due to SMVT and with recurrence-free outcome in most of them. Information from randomized studies is required regarding its use in patients with ES. Meanwhile, CA should be considered of great utility in the treatment of this serious clinical condition.

Conficts of interest

None declared

(See the authors’ conflict of interest forms in the web/Supplementary material)

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