Electrical storm presages nonsudden death: the antiarrhythmics versus implantable defibrillators (AVID) trial.

BACKGROUND: Electrical storm, multiple temporally related episodes of ventricular tachycardia (VT) or ventricular fibrillation (VF), is a frequent problem among recipients of implantable cardioverter defibrillators (ICDs). However, insufficient data exist regarding its prognostic significance. METHODS AND RESULTS: This analysis includes 457 patients who received an ICD in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial and who were followed for 31 +/- 13 months. Electrical storm was defined as > or = 3 separate episodes of VT/VF within 24 hours. Characteristics and survival of patients surviving electrical storm (n = 90), those with VT/VF unrelated to electrical storm (n = 184), and the remaining patients (n = 183) were compared. The 3 groups differed in terms of ejection fraction, index arrhythmia, revascularization status, and baseline medication use. Survival was evaluated using time-dependent Cox modeling. Electrical storm occurred 9.2 +/- 11.5 months after ICD implantation, and most episodes (86%) were due to VT. Electrical storm was a significant risk factor for subsequent death, independent of ejection fraction and other prognostic variables (relative risk [RR], 2.4; 95% confidence interval [CI], 1.3 to 4.2; P = 0.003), but VT/VF unrelated to electrical storm was not (RR, 1.0; 95% CI, 0.6 to 1.7; P = 0.9). The risk of death was greatest 3 months after electrical storm (RR, 5.4; 95% Cl, 2.4 to 12.3; P = 0.0001) and diminished beyond this time (RR, 1.9; 95% CI, 1.0 to 3.6; P=0.04). CONCLUSIONS: Electrical storm is an important, independent marker for subsequent death among ICD recipients, particularly in the first 3 months after its occurrence. However, the development of VT/VF unrelated to electrical storm does not seem to be associated with an increased risk of subsequent death.

Inactivation of a ventricular tachycardia preventive algorithm during automatic mode switching for atrial tachyarrhythmia.

A patient with a dual chamber implantable defibrillator and pause dependent VT in whom a rate smoothing algorithm failed to operate during automatic mode switching due to device idiosyncrasy is reported. Preventive measures are discussed.

Lethal ventricular arrhythmias following one-step pacemaker reprogramming for rapid tracking of atrial tachyarrhythmias.

An abrupt decrease in the pacing rate in patients with dual-chamber pacemakers tracking atrial tachyarrhythmias carries a high risk of malignant ventricular arrhythmia. The pacing rate should be reduced by multistep programming over several days.

Do baseline characteristics accurately discriminate between patients likely versus unlikely to benefit from implantable defibrillator therapy? Evaluation of the Canadian implantable defibrillator study implantable cardioverter defibrillatory efficacy score in the antiarrhythmics versus implantable defibrillators trial.

OBJECTIVE: Our purpose was to evaluate whether baseline characteristics predictive of implantable cardioverter defibrillator (ICD) efficacy in the Canadian Implantable Defibrillator Study (CIDS) are predictive in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. BACKGROUND: ICD therapy is superior to antiarrhythmic drug use in patients with life-threatening arrhythmias. However, identification of subgroups most likely to benefit from ICD therapy may be useful. Data from CIDS suggest that 3 characteristics (age > or =70 years, ejection fraction [EF] < or =0.35, and New York Heart Association class >II) can be combined to reliably categorize patients as likely (> or =2 characteristics) versus unlikely to benefit (<2 characteristics) from ICD therapy. METHODS: The utility of the CIDS categorization of ICD efficacy was assessed by Kaplan-Meier analysis and Cox hazards modeling. The accuracy of the CIDS score was formally tested by evaluating for interaction between categorization of benefit and treatment in a Cox model. RESULTS: ICD therapy was associated with a significantly lower risk of death in the 320 patients categorized as likely to benefit (relative risk [RR] 0.57, 95% confidence interval [CI] 0.37-0.88, P =.01) and a trend toward a lower risk of death in the 689 patients categorized as unlikely to benefit (RR 0.70, 95% CI 0.48-1.03, P =.07). Categorization of benefit was imperfect, as evidenced by a lack of statistical interaction (P =.5). Although 32 of the 42 deaths prevented by ICD therapy in AVID were in patients categorized as likely to benefit, all 42 of these patients had EF values < or =0.35. Neither advanced age nor poorer functional class predicted ICD efficacy in AVID. CONCLUSION: Of the 3 characteristics identified to predict ICD efficacy in CIDS, only depressed EF predicted ICD efficacy in AVID. Thus physicians faced with limited resources might elect to consider ICD therapy over antiarrhythmic drug use in patients with severely depressed EF values.

Concealed accessory pathway manifesting clinically only after pacemaker implantation.

A 66-year-old man with coronary artery disease and persistent left superior vena cava received a DDDR pacemaker for symptomatic 2:1 heart block. There was no previous history of tachyarrhythmias. Endless loop tachycardia and repetitive nonreentrant ventriculoatrial synchrony occurred afterwards and were triggered by a late coupled atrial premature beat. ECGs suggested a concealed left posterior accessory pathway that was confirmed during electrophysiological study. Effective palliation was achieved with extension of the PVARP and enabling noncompetitive atrial pacing operation.

Inappropriate pacing due to autoperpetuation of the ventricular rate stabilization algorithm: a manifestation of T wave oversensing by ICDs.

Preventive pacing algorithms designed to eliminate the pause that follows a premature ventricular depolarization have been incorporated in current implantable defibrillators. We report a patient in whom intermittent T wave oversensing frequently invoked the ventricular rate stabilization algorithm and resulted in periods of inappropriate VVI pacing. The problem was solved by decreasing the maximum sensitivity from 0.3 mV to 0.45 mV. Implant testing had revealed adequate sensing of ventricular fibrillation with a maximum sensitivity of 1.2 mV.

Emergencies related to implantable cardioverter-defibrillators.

Implantable cardioverter-defibrillators (ICDs) have become the dominant therapeutic modality for patients with life-threatening ventricular arrhythmias. ICDs are implanted using techniques similar to standard pacemaker implantation. They not only provide high-energy shocks for ventricular fibrillation and rapid ventricular tachycardia, but also provide antitachycardia pacing for monomorphic ventricular tachycardia and antibradycardia pacing. Devices incorporating an atrial lead allow dual-chamber pacing and better discrimination between ventricular and supraventricular tachyarrhythmias. Intensivists are increasingly likely to encounter patients with ICDs. Electrosurgery can be safely performed in ICD patients as long as the device is deactivated before the procedure and reactivated and reassessed immediately afterward. Prompt and skilled intervention can prove to be life-saving in patients presenting with ICD-related emergencies, including lack of response to ventricular tachyarrhythmias, pacing failure, and multiple shocks. Recognition and treatment of tachyarrhythmia can be temporarily disabled by placing a magnet on top of an ICD. The presence of an ICD should not deter standard resuscitation techniques. Multiple ICD discharges in a short period of time constitute a serious situation. Causes include ventricular electrical storm, inefficient defibrillation, nonsustained ventricular tachycardia, and inappropriate shocks caused by supraventricular tachyarrhythmias or oversensing of signals. ICD system infection requires hardware removal and intravenous antibiotic therapy. Deactivation of an ICD with the consent of the patient or relatives is reasonable and ethical in terminally ill patients.

Defibrillator implantation via the iliac vein.

We describe a 23-year-old patient with idiopathic dilated cardiomyopathy in whom an implantable cardioverter defibrillator was implanted via the right external iliac vein. Addition of a subcutaneous patch was required to obtain an adequate safety margin for defibrillation.

Negative T waves shortly after ST-elevation acute myocardial infarction are a powerful marker for improved survival rate.

BACKGROUND: Recent studies have reported that negative T waves in the setting of acute coronary events are associated with Thrombolysis In Myocardial Infarction flow grade 3 in the infarct-related artery and with improved parameters of ventricular function rather than with ischemia. METHODS: Patients enrolled in the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO-I) angiographic substudy (ie, patients with acute infarction randomly assigned to one of 4 thrombolytic regimens who then underwent coronary angiography) were included in this study if they survived at least 24 hours and had no confounding electrocardiographic factors (n = 1505). RESULTS: More patients had negative T waves develop (NT group, n = 938 [62%]) than not (PT group, n = 567 [38%]). Peak creatine kinase MB, time to thrombolysis, and randomization to accelerated alteplase were no different between the groups. Thirty days after admission, 12 patients in the NT group had died versus 25 patients in the PT group (1.3% vs. 4.4%; P <.001; odds ratio for negative T waves 0.28; 95% confidence interval 0.14-0.56). The difference persisted when only patients who survived at least 3 days were analyzed. After adjusting for relevant covariates (including presence of new Q waves in the follow-up electrocardiogram), negative T waves were an independent predictor for survival (P =. 007; odds ratio for negative T waves 0.38; 95% confidence interval 0. 18-0.78). Patients in the NT group were 35% more likely to have achieved patency of the infarct-related artery, although this difference was not statistically significant. CONCLUSIONS: Negative T waves shortly after acute myocardial infarction treated with thrombolysis were markers for improved 30-day survival rate. This finding merits prospective testing.

Determinants of outcome in patients with sustained ventricular tachyarrhythmias: the antiarrhythmics versus implantable defibrillators (AVID) study registry.

BACKGROUND: The prognosis of patients with sustained ventricular tachyarrhythmias varies according to clinical characteristics. We sought to identify predictors of survival in a large population of patients with documented sustained ventricular tachyarrhythmias not related to reversible or correctable causes included in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Registry. METHODS AND RESULTS: We analyzed the impact of 36 demographic, clinical, and discharge treatment variables on the outcome for 3559 patients. Survival status was assessed with the use of the National Death Index. Multivariate analyses were performed with the use of the Cox proportional hazards model. After a mean follow-up of 17 +/- 12 months, 631 patients died. Actuarial survival was 0.86 (95% confidence interval [CI] 0.85 to 0.88), 0.79 (95% CI 0.78 to 0.81), and 0.72 (95% CI 0.70 to 0.74) at 1, 2, and 3 years. Multivariate predictors of worse survival included older age, severe left ventricular dysfunction, lower systolic blood pressure, history of congestive heart failure, diabetes, smoking or atrial fibrillation, and preexistent pacemaker. The hemodynamic impact of the qualifying arrhythmia was not a predictor of outcome. Defibrillator implantation and hospital discharge while the patient was taking a beta-blocker or an angiotensin-converting enzyme inhibitor were associated with better prognosis. CONCLUSIONS: Despite therapeutic advances, the mortality rates of patients with sustained ventricular tachyarrhythmias remain high. Prognosis depends on the severity of underlying heart disease, as reflected by the extent of left ventricular dysfunction and the presence of heart failure. Well-tolerated ventricular tachycardia in patients with structural heart disease does not carry a significantly better prognosis than ventricular tachyarrhythmia with more severe hemodynamic consequences.

Interference with cardiac pacing.

Most exposures to electromagnetic interference are transient and pose no threat to patients with pacemakers and implantable cardioverter defibrillators. Prolonged exposure may be catastrophic in pacemaker dependent patients. New technologies (wireless phones, electronic antitheft surveillance) are safe if proper precautions are takes. Radiofrequency ablation requires concomitant temporary pacing. MR imaging remains contraindicated in patients with these devices until further study is undertaken.

The right ventricular tachycardias.

A variety of tachycardias originate from the right ventricle or use right ventricular structures as part of their circuit. They are characterized by a left bundle branch block pattern. Many of these tachycardias are relatively easy targets for radiofrequency catheter ablation. Ventricular tachycardia (VT) is the most common manifestation of arrhythmogenic right ventricular dysplasia, an often familial disease that can cause sudden death. Catheter ablation, antiarrhythmic drugs, or an implantable cardioverter-defibrillator may be used as therapy. Idiopathic right ventricular tachycardia has a benign course. It most often arises from the septal region of the right ventricular outflow tract. It commonly presents as nonsustained, repetitive monomorphic VT. The success rate of catheter ablation is greater than 90%. Bundle branch reentry occurs in patients with cardiomyopathy and His-Purkinje disease. It uses the right bundle branch anterogradely and the left bundle branch retrogradely. The QRS is very similar during VT and sinus rhythm. It can be cured by catheter ablation of the right bundle branch. VT seldom originates from the right ventricle in patients with coronary artery disease, idiopathic cardiomyopathy, or myocarditis. Atriofascicular (so-called Mahaim) fibers can sustain antidromic AV reentrant tachycardia. They represent an accessory AV node and His-Purkinje-like conduction system with atrial insertion in the right free wall near the tricuspid annulus and distal insertion directly into the right bundle branch. The accessory connection is ablated at the level of the tricuspid ring.

Which is the optimal testing method for identifying an AV delay that allows intrinsic conduction?

It is desirable to maintain normal, conducted ventricular activation in patients with dual-chamber pacemakers and preserved atrioventricular (AV) conduction. The shortest AV delay resulting in consistent ventricular inhibition (avoiding ventricular pseudofusion) was determined by a conventional incremental (inside-out) technique vs the alternate decremental (outside-in) technique in 20 such patients. Determinations were made in VDD mode in 20 patients and DDD mode (approximately 10 beats/min faster than the intrinsic rate) in 19. In VDD mode, the shortest AV delay avoiding ventricular pseudofusion was never found during inside-out testing. It was identical with both methods in 10 patients (50%), and shorter by 10-80 ms (mean 20 +/- 20 ms) with the outside-in method in the remaining 10 (P = 0.004). In DDD mode, the shortest AV delay resulting in consistent ventricular inhibition was found only once during inside-out testing. It was the same with both methods in 13 patients (68%), and shorter by 10-20 ms (mean 14 +/- 5 ms) with the outside-in method in the remaining 5 (26%, P = 0.18; Fisher's exact test). The shortest sensed AV delay preventing ventricular pseudofusion is most likely to be found with a decremental method (outside-in). In rare patients, it identifies AV delays resulting in inhibition, while ventricular pacing persists at longer programmable AV delays with the conventional inside-out approach.