Management of electrical instability after ICD implantation

A Challenging Case of Electrical Storm in an Implantable Cardioverter Defibrillator Patient

Implantable cardioverter defibrillators (ICD) have become indispensable in managing life-threatening ventricular arrhythmias. On average, 50%-70% of the patients receive a device-based therapy within the first two years post implantation. A few patients experience the electrical storm (ES). ES is a syndrome of recurrent ventricular tachycardia or fibrillation occurring two or more times in a 24-hour period, calling for the need of electrical cardioversion or defibrillation to stabilize the patient. We present the case of a patient with severe cardiomyopathy who presented with resistant ES after failing to respond initially to conventional medications like amiodarone and lidocaine. Propofol infusion was not an option due to his severe cardiomyopathy and hypotensive shock state. Aggressive treatment with intravenous medications stabilized his ES and he was eventually transferred to an outside facility for ventricular tachycardia ablation.

[Electrical storm: definition, prevalence, causes and prognostic implications]

BACKGROUND

Electrical storm (ES) represents a state of cardiac electrical instability which manifests by multiple episodes of ventricular tachyarrhythmia (VT) within a short time. In patients with an implantable cardioverter-defibrillator (ICD), ES is best defined as ≥ 3 appropriate VT detections in 24 h, treated by antitachycardia pacing or shock. The number of shocks and inappropriate detections are irrelevant for the definition. Within a period of 3 years ES occurred in approximately 25 % of ICD patients with secondary prophylaxis indications of sudden cardiac death. Although the definition includes minor arrhythmic events, ES frequently consists of up to 50 VTs. Potential triggers found in 20-65 % of patients include new/deteriorated heart failure, diarrhea/hypokalemia, changes in antiarrhythmic medication, association with other illnesses, and psychological stress. In most patients ES consists of monomorphic VT indicating the presence of reentry while ventricular fibrillation indicating acute ischemia is rare.

MATERIAL AND METHODS

ES seems to have a low immediate mortality (1 %) but frequently (50-80 %) leads to hospitalization. Long-term prognostic implications of ES are unclear. The key intervention in ES is a reduction of the elevated sympathetic tone by beta blockers and also frequently sedation. Amiodarone i.v. is highly efficient in ES while class I antiarrhythmic drugs are usually unsuccessful. Substrate mapping and VT ablation may be useful in treatment and prevention of ES. Prevention of ES requires ICD programming systematically avoiding unnecessary shocks by long VT detection and numerous attempts of antitachycardia pacing before shock therapy which can fuel the sympathetic tone and prolong ES.

A case of aborted sudden cardiac death and consequent extreme electrical storm secondary to a metastatic cardiac tumor

We report a 43-year-old man with an implantable cardioverter defibrillator for aborted sudden cardiac death. He represents in extreme electrical storm with 111 different ventricular fibrillation episodes. Successful treatment was achieved with multiple antiarrhythmic agents, mechanical ventilation, external shocks, and ultimately overdrive pacing. A cardiac magnetic resonance scan revealed two cardiac lesions that were later diagnosed as metastatic fibrosarcoma. This case highlights two very important and increasingly common cardiological dilemmas: the management of extreme electrical storm and the role of magnetic resonance imaging in aborted cardiac death patients with an apparent "normal" heart.

Recurrent ventricular arrhythmia storms in the age of implantable cardioverter defibrillator therapy: a comprehensive review

Rapidly recurrent ventricular arrhythmia is not an infrequent clinical entity in the era of implantable cardioverter defibrillator therapy. Clinical presentation can vary dramatically, from multiple defibrillator shocks with hemodynamic instability, to asymptomatic delivery of anti-tachycardia pacing. Although some investigators have reported disparate prognostic implications with electrical storm, in larger trials of both primary and secondary defibrillator populations, electrical storm appears to be a harbinger of cardiac death with a notably high mortality early post event. While acute cessation of electrical storm is generally achievable with medical therapy, it is critical to recognize that the causes for subsequent mortality are often not arrhythmic in nature. Thus, the challenge for cardiovascular practitioners is to maximize substrate based therapy and modification to not only prevent further episodes of electrical storm and possibly curtail the considerable risk of subsequent cardiac mortality.

Electrical storm in patients with an implanted defibrillator: a matter of definition

The term "electrical storm" (ES) indicates a state of cardiac electrical instability manifested by several episodes of ventricular tachyarrhythmias (VTs) within a short time. In patients with an implantable cardioverter defibrillator (ICD), ES is best defined as 3 appropriate VT detections in 24 h, treated by antitachycardia pacing, shock or eventually untreated but sustained in a VT monitoring zone. The number of shocks and inappropriate detections are irrelevant for the definition. ES occurs in approximately 25% of ICD patients within 3 years, with typically 5-55 individual VTs within one storm. Potential triggers can be found in approximately 66% of patients and include new/worsened heart failure, changes in antiarrhythmic medication, context with other illness, psychological stress, diarrhea, and hypokalemia. In most patients, ES consists of monomorphic VT indicating the presence of reentry while ventricular fibrillation indicating acute ischemia is rare. ES seems to have a low immediate mortality (1%) but frequently (50-80%) leads to hospitalization. Long-term prognostic implications of ES are unclear. The key intervention in ES is reduction of the elevated sympathetic tone by beta blockers and frequently benzodiazepines. Amiodarone i.v. has also been successful and azimilide seems promising while class I antiarrhythmic drugs are usually unsuccessful. Substrate mapping and VT ablation may be useful in treatment and prevention of ES. Prevention of ES requires ICD programming systematically avoiding unnecessary shocks (long VT detection, antitachycardia pacing where ever possible) which otherwise can fuel the sympathetic tone and prolong ES.

Radiofrequency Catheter Ablation for Arrhythmic Storm in Patients with An Implantable Cardioverter Defibrillator

The aim of the study was to analyze the usefulness of RFA in controlling arrhythmic storm due to hemodynamically stable VT in a cohort of patients with an ICD and to evaluate the incidence of arrhythmic storm among patients with an ICD. A group of 13 (3%) of 403 consecutive ICD recipients were submitted to RFA of VT during an arrhythmic storm. Two additional patients were referred from other institutions. Standard criteria were used for VT endocardial ablation. A transcatheter epicardial approach was required in three patients. A total of 18 procedures were performed in 15 patients. A mean of 13.2 +/- 9.7 pulses of RF were delivered. Clinical tachycardia was successfully ablated in 12 (80%) patients. One patient died in incessant VT, 1 patient underwent heart transplant, and 1 was treated with direct current ablation. During a mean follow-up of 12 +/- 17 months, only two patients suffered a single episode of VT. Arrhythmic storm requiring VT ablation was uncommon among patients with an ICD and occurred late after ICD implantation. The arrhythmic episode was successfully controlled in the majority of patients with endocardial or epicardial RFA.

Clusters of ventricular fibrillation in a patient with an implantable cardioverter difibrillator treated with amiodarone

A 44 year-old man with severe left ventricular dysfunction resulting from an old myocardial infarction developed clusters of ventricular fibrillation (VF). Although coronary bypass surgery was performed and heart failure was well controlled, the VF recurred during amiodarone therapy. Despite multiple deliveries of shocks by an implantable cardioverter defibrillator, the electrical storm could not be terminated. Some substrate for rapid ventricular tachyarrhythmias, refractory to class III drugs, can lead to death from arrhythmia.

Clusters of ventricular tachycardias signify impaired survival in patients with idiopathic dilated cardiomyopathy and implantable cardioverter defibrillators

OBJECTIVES

This retrospective study was undertaken to provide data on occurrence, significance and therapy of ventricular tachyarrhythmia (VT) clusters (VTCs) in patients with dilated cardiomyopathy (DCM) and implantable cardioverter defibrillators (ICDs).

BACKGROUND

Data on the clinical significance of VTCs are lacking in patients with DCM and ICDs.

METHODS

Baseline characteristics of 106 consecutive patients with DCM and ICDs were prospectively collected, and chart reviews and episode data retrospectively analyzed. A VTC was defined as > or =3 sustained VTs/24 h.

RESULTS

During a mean follow-up of 33+/-23 months, 73 patients (68.9%) had recurrent VT or ventricular fibrillation (VF), 43 patients (40.6%) suffered only single VTs and 30 patients (28.3%) experienced 52 clusters of VTs. Actuarial survival free of VT or VF was 44.6%, 33.0% and 26.5%, and survival free of VTC was 77.3%, 72.2% and 67.1% after one, two and three years, respectively. Independent predictors of VT clusters were heart failure before ICD implantation (p = 0.033), presenting monomorphic VT (p = 0.044), EF <0.40 (p = 0.014) and inducible mVT, especially with right bundle branch block and superior axis configuration (p<0.001). Survival free of recurrent VTCs was 50.8%, 38.1% and 19.0% after one, two and three years, respectively. Once a VTC had occurred, only 56.7%, 46.4%, 30.9% and 15.5% of patients survived and were not transplanted after one, two, three and four years, respectively. Survival was even more reduced if a VTC was associated with cardiac decompensation: 65.6% and 21.9% after one and two years, respectively.

CONCLUSIONS

Despite antiarrhythmic intervention, clusters of VTs occur and recur frequently in patients with DCM. They signify impaired survival, especially if they are associated with cardiac decompensation, and may be a harbinger of progressive myocardial deterioration rather than a primarily arrhythmic problem. The benefit of ICD therapy may therefore be low in these patients.

Failure of automatic mode switching: recognition and management

Dual chamber pacing is desirable to optimize AV synchrony and to potentially decrease the incidence of supraventricular tachyarrhythmias. Patients with alternating periods of both supraventricular tachyarrhythmias and bradycardia pose a difficult challenge when standard dual chamber pacemakers are implanted. The automatic mode switching mode algorithm was introduced to prevent tracking of paroxysmal supraventricular tachyarrhythmias and avoid the adverse hemodynamic and symptomatic consequences of a rapid ventricular response. In some cases, failure to mode switch may take place when the atrial signal during tachycardia is of insufficient amplitude to be sensed. Failure to mode switch may also occur when the atrial signal periodically occurs in the atrial blanking period(s). In this article, we describe failure to mode switch in seven patients with paroxysmal supraventricular tachyarrhythmias after a Telectronics Meta DDDR 1254 device was implanted. Each patient had paroxysmal atrial flutter and/or atrial fibrillation and presented with either repetitive episodes of oscillation between atrial tracking and mode switching to a nonatrial tracking pacing mode or complete failure to mode switch. Six of seven patients were taking antiarrhythmic drugs that resulted in slowing of the atrial cycle length. Pacemaker reprogramming was required in each case to restore reliable mode switching during subsequent recurrences of the atrial tachyarrhythmias. We conclude that careful pacemaker programming of patients with paroxysmal atrial flutter and the Telectronics Meta DDDR 1254 is necessary when patients are taking an antiarrhythmic drug that slows atrial cycle length.