Reduction in shock burden with catheter ablation versus escalated antiarrhythmic drug therapy: Insights from the VANISH trial

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): 1. Canadian Institutes of Health Research (CIHR)

2. Additional financial support from St. Jude Medical and Biosense Webster

Background

Recurrent shocks for ventricular tachycardia (VT) are associated with an increased risk of heart failure and mortality and have a negative influence on quality of life. Catheter ablation has been shown to improve VT event-free survival in patients with antiarrhythmic drug (AAD)-refractory VT and prior myocardial infarction (MI); however, the effects of ablation on shock burden has yet to be investigated.

Purpose

Our primary objectives were to compare the shock-treated VT event burden and appropriate shock burden following randomization to treatment with either catheter ablation or escalated AAD therapy among VT patients with prior MI in the Ventricular tachycardia AblatioN versus escalated antiarrhythmic drug therapy in Ischemic Heart disease (VANISH) randomized trial.

Methods

Recurrent event analyses were performed using the intention-to-treat population of the VANISH trial. Shock-treated VT event burden was defined as the total number of VT events treated with ≥1 appropriate internal or external shocks. Appropriate shock burden was defined as the total number of appropriate internal and external shocks delivered, regardless of the number of VT events. All VT events and implantable cardioverter defibrillator (ICD) therapies were adjudicated by reviewers blinded to the treatment allocation. Three recurrent event models were used to compare the shock burden between treatment arms (Anderson-Gill (AG), Frailty, and Prentice, Williams, and Peterson Total Time (PWP-TT). Each model clustered by patient and accounted for competing risk of death with the Fine and Gray sub-distributions hazards model.

Results

Of the 259 patients enrolled in the VANISH trial [median age 69.8 (IQR 63.0-74.2) years, 7.0% women], 132 patients were randomized to ablation and 129 patients to escalated AAD therapy. Over a median follow-up of 23.4 (IQR 14.7-40.4) months, there were 138 shock-treated VT events [39.07 (95% CI 33.14-46.07) shock-treated VT events per 100 person-years] in the ablation arm and 218 shock-treated VT events [64.60 (95% CI 56.49–73.84) shock-treated VT events per 100 person-years] in the escalated AAD therapy arm (Figure 1). Ablation patients had a 40% lower shock-treated VT event burden (ie. number of shock-treated VT events) compared to patients randomized to escalated AAD therapy [Figure 1; AG HR 0.60 (95% 0.38-0.95)]. Further, there was also a statistically significant reduction in the appropriate shock burden (i.e. number of appropriate shocks) among ablation patients (169 appropriate shocks) compared to escalated AAD therapy patients (266 appropriate shocks) [Figure 1; AG HR 0.61 (95% CI 0.37-0.96)]. All results were consistent between the 3 recurrent event models.

Conclusion

Among patients with AAD-refractory VT and a prior MI, catheter ablation reduced shock-treated VT event burden and appropriate shock burden compared to escalated AAD therapy.

Comparative effectiveness of ventricular tachycardia ablation versus escalated antiarrhythmic drug therapy by location of myocardial infarction: A sub-study of the VANISH trial

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): Fonds de recherché du Québec-Santé (FRQS) [post doctoral award for Dr. Samuel)

BACKGROUND

Complexity of ventricular tachycardia (VT) substrate, efficiency of lesion formation, and the size and thickness of infarction area border zones differ based on location of myocardial infarctions (MI). These differences may translate into heterogeneity in risk of events and effectiveness of treatments for VT. Small observational studies suggest that VT from inferior infarctions have higher risk of early recurrence despite smaller infarct areas. However, differential effectiveness of VT treatments based on location of MI not been definitively established.

PURPOSE

The objective of this sub-study of the Ventricular tachycardia AblatioN versus escalated antiarrhythmic drug therapy in ISchemic Heart disease (VANISH) randomized trial was to compare the effectiveness of VT ablation by location of MI in reducing the composite endpoint of all-cause mortality, VT storm, or appropriate ICD therapy when compared to escalated pharmacological therapy in VT patients with a prior MI.

METHODS

VANISH participants were categorized into 3 subgroups based on MI location: 1. Inferior (may also have MI in other locations); 2. Non-inferior (no inferior MI, all patients not in group 1); and 3. Anterior (may also have MI in other locations). Inverse probability of treatment weighting was used to balance baseline characteristics (ie. age, sex, comorbidities, medications, and the location of additional infarctions) between patients randomized to ablation or escalated therapy within each subgroup. Weighted Cox proportional hazards models were calculated separately for each subgroup.

RESULTS

Of 259 patients enrolled in the VANISH trial [median age 69.8 (IQR 63.0-74.2) years, 7.0% women], 135 had an inferior MI, 124 a non-inferior MI, and 83 an anterior MI. Among patients with an inferior MI, no statistically significant difference in the primary outcome was detected between patients randomized to ablation or escalated therapy [aHR 0.78 (95% CI 0.51-1.20)]. In contrast, patients with non-inferior MIs had a statistically significant reduction in the incidence of the primary outcome with ablation [aHR 0.48 (95% CI 0.27-0.86)]; which was of greater magnitude than the reduction observed in the overall results of the VANISH trial [HR 0.72 (95% CI 0.53-0.98)]. In addition, a trend towards a reduction in the primary outcome with ablation was detected in patients with anterior MIs [aHR 0.50 (95% CI 0.23-1.09)].

CONCLUSION

The effectiveness of VT ablation versus escalated pharmacological therapy varies based on the location of the MI. Patients with MI scars located only in non-inferior regions of the ventricles derive greater benefit from VT ablation in reducing VT-related events. Further studies are required to explore reasons for this finding and to assess the impact of VT treatment strategies based on MI location in optimizing outcomes.

915ATP efficacy on terminating ventricular tachycardia by device type, indication, and ventricular median cycle length

Funding Acknowledgements

Medtronic

OnBehalf

PainFree SST

Background

Anti-tachycardia Pacing (ATP) is an established therapy that terminates VT without the need for painful ICD shocks. Here we use the data from PainFree SST clinical trial to evaluate the ATP success rate by device type, indication and MCL. 

Methods

Spontaneous episodes that were detected by ICD or CRT-D devices in the VT, fast VT and VF zones were included in the analysis. Episodes successfully terminated by ATP were deemed as having ATP success. Using the GEE method, ATP success rate and its 95% CI were calculated for device types, indications and ventricular MCL. 

Results

Of the 2770 enrolled patients (79% male, average age 65 years), 1699 (61%) were implanted with an ICD and 1071 (39%) with a CRT-D system; 1917 (69%) were reported as primary prevention and 847 (31%) were secondary prevention patients. For all MVT episodes, the ATP success rate was similar between ICD and CRT-D devices (82.3% vs 80.3%, p = 0.74). Patients with secondary prevention had a higher ATP success rate compared to those with primary prevention but the difference was not statistically significant (84.4% vs 76.8%, p = 0.16). Regardless of device type and indication, ATP success rate was significantly higher in the slower VTs (MCL ≥ 320 ms) compared to the faster VTs (MCL ≥ 240 to < 320 ms) (89.2% vs 73.7%, p < 0.0001). 

Conclusion

We found that ATP had a greater than 80% rate of success for terminating ventricular tachycardias overall. Slower VTs was significantly associated with a higher ATP success rate regardless of device type and indication compared to faster VTs. For faster VTs with a MCL ≥ 240 to < 320 ms, the ATP success rate was still successful at terminating VT more than 70% of the time.

Table 1. ATP Success Rates - No. of Enrolled Subjects (% of total) No. of Episodes Analyzed for ATP Success (No. of Subjects) GEE-estimated ATP Success Rate (95% CI) P-value* Overall 2770 (100%) 2277 (376) 81.5% (78.4%, 84.2%) - Device Type - - - 0.7440 ICD 1699 (61.3%) 1484 (229) 82.3% (78.3%, 85.6%) - CRT-D 1071 (38.7%) 793 (147) 80.3% (75.0%, 84.6%) - Indication - - - 0.1609 Primary Prevention 1917 (69.2%) 631 (160) 76.8% (71.2%, 81.6%) - Secondary Prevention 847 (30.6%) 1615 (212) 84.4% (80.7%, 87.6%) - Median Cycle Length - - - <0.0001 (>/=) 240 ms and < 320 ms - 861 (257) 73.7% (69.2%, 77.7%) - (>/=) 320 ms - 1416 (209) 89.2% (85.7%, 91.9%) - * Per a GEE main effect model for all episodes where device type, indication and median cycle length were considered.

Cesium chloride induced ventricular arrhythmias in dogs: three-dimensional activation patterns and their relation to the cesium dose applied

INTRODUCTION

Cesium chloride has widely been used in experimental models to produce various ventricular arrhythmias. The study was designed to evaluate whether type and mechanism of these arrhythmias are dose-dependent.

METHODS

In 7 dogs with acute AV-block, 60 pins containing 4 bipolar electrodes each were inserted into both ventricles to provide 240 endo-, epi- and midmyocardial recording sites. A computerized mapping system was used to determine three-dimensional activation patterns of ventricular arrhythmias induced by three injections of 1 mmol/kg cesium chloride at 20 minute intervals.

RESULTS

Out of all arrhythmias induced, 25 ventricular extrasystoles, 31 monomorphic and 47 polymorphic ventricular tachycardias were mapped. Nonsustained ventricular tachycardias were readily inducible by a single bolus of cesium chloride, whereas sustained episodes required repetitive injections (1.45 +/- 0.61 vs. 2.61 +/- 0.57 doses, p < 0.05). Polymorphic tachycardias were observed more commonly than monomorphic tachycardias (87 vs. 31). Initiation and maintenance of cesium induced arrhythmias were exclusively based on focal mechanisms originating from the subendocardium, irrespective of morphology and dosage. All monomorphic arrhythmias were caused by repetitive firing of single immobile foci located in either the right or the left ventricle. Bi- and multifocal mechanisms, however, were found to underlie the polymorphic episodes.

CONCLUSIONS

Although there is a dose-dependence as to the sustenance of mono- or polymorphic tachycardias, this does not reflect on the three-dimensional activation pattern of cesium induced arrhythmias, which are due to mono- or multifocal activation originating from the subendocardium.

Echocardiographic Fourier phase and amplitude imaging for quantification of ischemic regional wall asynergy: an experimental study using coronary microembolization in dogs

OBJECTIVES

This study investigated whether echocardiographic Fourier phase and amplitude imaging can be used to evaluate ischemia-related regional wall asynergy.

BACKGROUND

Because myocardial ischemia delays the onset and peak of endocardial inward motion and reduces its magnitude, Fourier phase and amplitude analysis of two-dimensional echocardiograms may be used to evaluate regional wall motion abnormalities objectively by analyzing temporal sequence and magnitude of endocardial motion.

METHODS

Digital cine loops of left ventricular long- and short-axis views were obtained in six anesthetized dogs at baseline and 1 to 30 min after coronary microembolization and were mathematically transformed using a first-harmonic Fourier algorithm to obtain phase angles and amplitudes of endocardial segments. Mean phase angles and amplitudes were compared with visual wall motion analysis based on a scoring system and quantitative analysis based on segmental fractional area shortening derived from planimetry.

RESULTS

Microembolization delayed segmental phase angles by 47 +/- 44 degrees in mild to moderate hypokinesia (fractional shortening [mean +/- SD] 41 +/- 13%) and by 77 +/- 63 degrees in severe hypokinesia (fractional shortening 13 +/- 5%) and reduced segmental amplitudes from 80 +/- 36 gray level intensity at baseline to 53 +/- 34 in segments developing mild to moderate hypokinesia, and from 93 +/- 36 to 35 +/- 28 gray level intensity in segments developing severe hypokinesia. Shifts in segmental phase angles correlated better with dynamic shifts in segmental fractional area shortening than did changes in wall motion score (r = -0.65 vs. r = 0.52, p < 0.001).

CONCLUSIONS

Echocardiographic Fourier phase imaging can be used to evaluate ischemia-related regional wall asynergy, displaying contraction sequence and magnitude in a simple, objective format.

Advances in follow-up techniques for implantable defibrillators

The complexity of newer implantable defibrillators has made device follow-up increasingly more intricate. Extensive data-logging capacity provides specific information on recorded events, which facilitates more accurate determination of patient arrhythmias. This helps the clinician judge whether the device is detecting and treating arrhythmias appropriately, or whether false sensing of external signals or supraventricular rhythms is occurring. There is also a record of the efficacy of delivered therapy from the device that helps in optimizing subsequent programming. Programming itself has become much more complicated, with multiple independently programmable therapy zones, each with numerous available therapeutic modalities. In addition, defibrillator status information has been improved. Accurate battery voltage measurements give a reasonable estimate of remaining device life, and pace/sense and shock lead impedances can be measured to provide information on total system integrity. Together, these advances allow more specific programming of the device to the individual patient's condition but require increasing experience and expertise of the physician.

Acute efficacy and chronic follow-up of patients with non-thoracotomy third generation implantable defibrillators

Non-thoracotomy implantation of implantable cardioverter defibrillators (ICDs) has simplified the process of device insertion, promising to decrease associated procedural complications while providing sudden death protection at least equal to epicardial systems. This study presents the acute and chronic results of 110 patients who underwent attempted non-thoracotomy ICD implantation with the Medtronic Transvene lead system and PCD model 7217 or 7219. Of the 110 patients attempted, 100 (91%) had the system successfully implanted without the need for an epicardial patch. One patient died 1 week postoperatively of septic shock related to the implantation (0.9% perioperative mortality). During follow-up of 16 +/- 11 months, 45% of the patients had an event detected as ventricular tachycardia; 26% of these detections were felt clinically to be due to supraventricular rhythms. Of the remainder, 87% were successfully treated with the first VT therapy, and 98% were terminated by the final therapy; 66% of the patients had at least one episode of ventricular fibrillation, of which 5% were felt to be inappropriate detections; 85% of the appropriate episodes were successfully treated with the first VF therapy, and all were converted by the final therapy. Total mortality at 6, 12, and 24 months was 3%, 11%, and 19% respectively. Only one patient had sudden cardiac death, occurring at 13 months postimplant. Overall, the non-thoracotomy lead system for this ICD displayed infrequent implant complications and proved to be reliable at terminating arrhythmias and maintaining a low rate of sudden cardiac death in this high risk population.