Effect of acute amiodarone loading on energy requirements for biphasic ventricular defibrillation

Evaluation of defibrillation safety margin in modern implantable cardioverter defibrillators after administration of amiodarone

AIM

The adjunctive medication with amiodarone plays a major role in patients with an implantable cardioverter defibrillator (ICD). Amiodarone as class III antiarrhythmic drug may significantly alter the defibrillation threshold (DFT). Conflicting results exist on the clinical relevance of a DFT rise on amiodarone. The only prospective study on this issue included only a small number of patients on amiodarone. The purpose of this study was to assess the safety and clinical relevance of repeat defibrillator testing after initiation of amiodarone in modern defibrillator systems.

METHODS AND RESULTS

We assessed risks and clinical consequences of retesting defibrillation safety margin after initiation of amiodarone in 130 consecutive patients. All patients underwent intraoperative testing at the time of first ICD implantation. A repeated VF induction and defibrillator test (by protocol with a single shock and 10 J safety margin) after a total dose of at least 10 g amiodarone 4-6 weeks after initiation of medication was performed. DFT testing after initiation of amiodarone was safe as there were no complications that led to a prolonged hospital stay. In 4 of 114 patients with a left-sided device (1.6%) and 3 of 7 patients with a right-sided device (42.8%), a 10 J safety margin could not be achieved. As a result 4 patients (3.1% of study collective) had a revision of the system.

CONCLUSION

Repeat defibrillation testing after administration of amiodarone therapy rarely fails in patients with left-sided devices. We observed a higher test failure in patients with a device in the right-subpectoral position although this subgroup was small. Repeat defibrillator testing is safe as no relevant complications were observed.

Sotalol as adjunctive therapy to implantable cardioverter-defibrillators in heart failure patients

The number of heart failure patients with implantable cardioverter-defibrillators is rising. Common issues encountered in this population are high defibrillation thresholds and inappropriate shocks. In order to resolve these problems, the addition of a class III antiarrhythmic such as sotalol is often considered. Given the emerging issue of polypharmacy and medication compliance in the heart failure population, the question of the efficacy of sotalol in reducing inappropriate shocks, defibrillation thresholds, and its ability to replace conventional beta-blockers is often raised. Current literature review suggests that sotalol is a useful adjunct to the contemporary heart failure regimen. It has the ability to reduce inappropriate shocks and defibrillation thresholds, but appears not to fully reproduce the pleiotropic beneficial effects of the beta-blockers more commonly employed for their mortality/remodeling benefits in heart failure patients.

Testing the Implantable Cardioverter-Defibrillator After Implantation?Is It Necessary?

The results of intraoperative and postoperative predischarge implantable cardioverter-defibrillator (ICD) testing of 211 consecutive patients, starting at 15 J and requiring two successful terminations of induced VT/VF with a relative defibrillation safety margin (DSM) of >10 J, were reviewed. The aim was to define the type of intraoperative response that would make postoperative predischarge testing unnecessary. The intraoperative responses were divided into three types: A, a DSM > or =10 J and an absolute energy level of < or =20 J; B, a DSM of > or =10 J and an absolute energy level of >20 J; and C, a DSM <10 J and an absolute energy level of >20 J. At operation, the responses to defibrillation were A, 88.6%; B, 7.1%; and C, 4.3%. Accepting an A response only would leave 11.4% of the patients for postoperative testing. The positive and negative predictive values for diagnosing a postoperative C response were 0.78 and 0.97, respectively. Similarly, the predictive values for diagnosing a postoperative B or C response were 0.71 and 0.97, respectively. The postoperative testing responses were A, 89.1%; B, 4.3%; and C, 6.6%. In summary, an intraoperative A response was sufficient to make a postoperative defibrillation testing unnecessary, while it was found that intraoperative B and C responders should undergo postoperative testing. Applying these criteria, approximately 90% of the patients could be discharged without any postoperative induction test.

Is there a role for antiarrhythmic drugs in patients with implantable defibrillators?

With remarkable advancement in technology and clinical research, implantable cardioverter defibrillators (ICDs) have replaced antiarrhythmic drugs as the preferred modality for both primary and secondary prevention of arrhythmic deaths. However, concomitant use of antiarrhythmics in patients with ICDs remains common, often for prevention or reduction of appropriate and inappropriate shocks caused by ventricular and supraventricular arrhythmias, respectively. The role of empiric antiarrhythmic therapy in this patient population remains less clearly defined, with conflicting information from various small randomized trials. Use of antiarrhythmic drugs in the ICD patient population not only can cause potentially serious side effects but can also interact or interfere with the ICD device function. In addition, the effect on survival in patients with ICDs is not well characterized. Given the many potential side effects, drug-device interactions, unclear survival effect, and lack of convincing clinical data supporting its use, empiric antiarrhythmic therapy in the ICD patient population cannot be recommended at this time.

Japanese randomized trial for investigation of a combined therapy of amiodarone and implantable cardioverter defibrillator in patients with ventricular tachycardia and fibrillation: the Nippon ICD Plus Pharmachologic Option Necessity study design

BACKGROUND

Implantable cardioverter-defibrillators (ICDs) are the most effective therapy in reducing the mortality of patients with life-threatening ventricular tachyarrhythmias. However, the ICD cannot prevent the recurrence of tachycarida attacks and that limits the clinical usefulness of them. The Nippon ICD Plus Pharmachologic Option Necessity (NIPPON) trial was designed as the first prospective randomized study to test the hypothesis whether amiodarone could improve the patient's clinical outcome by reducing the amount of ICD therapy in the Japanese patient population.

METHODS AND RESULTS

Approximately 400 patients with organic heart disease and spontaneous episode(s) of sustained ventricular tachycardia/fibrillation (VT/VF) will be randomly assigned to one of 2 groups; the amiodarone group and non-amiodarone group. Both groups of patients will be followed at least for 24 months. The end-point committee will adjudicate events in a blinded fashion. The primary end-points of this study are determination of the appropriate therapy from the ICD and alteration of the assigned treatment because of its harmful effects and/or frequent ICD therapies.

CONCLUSION

The NIPPON study is expected to confirm our understanding of the prognostic and therapeutic usefulness of adjuvant amiodarone therapy for patients with an ICD and with a history of sustained VT/VF.

Amiodarone Therapy in Patients Implanted With Cardioverter-Defibrillator for Life-Threatening Ventricular Arrhythmias

BACKGROUND

Whether amiodarone can improve the patient's clinical outcome by reducing implantable cardioverter-defibrillator (ICD) therapy deliveries for ventricular tachycardia or fibrillation (VT/VF) has not been clearly evaluated.

METHODS AND RESULTS

A total of 507 patients with VT/VF due to organic heart disease who had ICDs implanted were enrolled in this study. The patients were divided into 3 groups: Amiodarone (n=247), Class I anti-arrhythmic drug (n=103) and CONTROL (n=157) groups, and the total cause mortality and arrhythmic event free survival rates were evaluated between the groups. The mean follow-up period was 38+/-27 months. The left ventricular ejection fraction was significantly decreased in the Amiodarone group (Amiodarone: 37+/-15%; Class I: 39+/-16%;

CONTROL

44+/-17%). The mortality and arrhythmic events were significantly higher in the Class I group than the Amiodarone group (p<0.05), but there was no significant difference between the Amiodarone and CONTROL groups (arrhythmic event free rate at 5 years: Amiodarone: 53%; Class I: 35%;

CONTROL

48%; 5 year survival: 86%, 74% and 77%, respectively). Side effects from amiodarone were found in 12% of the patients, but no fatal events were observed.

CONCLUSIONS

The present study could not demonstrate the benefit of amiodarone in ICD patients, probably due to a significant clinical bias exerted in selecting this drug.