Noninvasive Programmed Ventricular Stimulation-Guided Management Following Ventricular Tachycardia Ablation

One-year outcomes after stereotactic body radiotherapy for refractory ventricular tachycardia

BACKGROUND

Cardiac stereotactic body radiotherapy (SBRT) has emerged as a promising noninvasive treatment for refractory ventricular tachycardia (VT).

OBJECTIVE

The purpose of this study was to describe the safety and effectiveness of SBRT for VT in refractory to extensive ablation.

METHODS

After maximal medical and ablation therapy, patients were enrolled in a prospective registry. Available electrophysiological and imaging data were integrated to generate a plan target volume. All SBRTs were planned with a single 25 Gy fraction using respiratory motion mitigation strategies. Clinical outcomes at 6 weeks, 6 months, and 12 months were analyzed and compared with the 6 months prior to treatment. VT burden (implantable cardioverter-defibrillator [ICD] shocks and antitachycardia pacing sequences) as well as clinical and safety outcomes were the main outcomes.

RESULTS

Fifteen patients were enrolled and underwent planning. Fourteen (93%) underwent treatment, with 12 (80%) surviving to the end of the 6-week period and 10 (67%) surviving to 12 months. From 6 week to 12 months, there was recurrence of VT, which resulted in either appropriate antitachycardia pacing or ICD shocks in 33% (4 of 12). There were significant reductions in treated VT at 6 weeks to 6 months (98%) and at 12 months (99%) compared to the 6 months before treatment. There was a nonsignificant trend toward lower amiodarone dose at 12 months. Four deaths occurred after treatment, with no changes in ventricular function.

CONCLUSION

For a select group of high-risk patients with VT refractory to standard therapy, SBRT is associated with a reduction in VT and appropriate ICD therapies over 1 year.

Electrical Storm Has Worse Prognosis Compared to Sustained Ventricular Tachycardia after VT Ablation

Background: Electrical storm (ES) represents a serious heart rhythm disorder. This study investigates the impact of ES on acute ablation success and long-term outcomes after VT ablation compared to non-ES patients. Methods: In this large single-centre study, patients presenting with ES and undergoing VT ablation from June 2018 to April 2021 were compared to patients undergoing VT ablation due to ventricular tachyarrhythmias but without ES. The primary prognostic outcome was VT recurrence, and secondary endpoints were rehospitalization rates and cardiovascular mortality, all after a median follow-up of 22 months. Results: A total of 311 patients underwent a first VT ablation due to ventricular tachyarrhythmias and were included (63 ± 14 years; 86% male). Of these, 108 presented with ES. In the ES cohort, dilated cardiomyopathy as underlying heart disease was significantly higher (p = 0.008). Major complications were equal across both groups (all p > 0.05). Ablation of the clinical VT was achieved in 94% of all patients (p > 0.05). Noninducibility of any VT was achieved in 91% without ES and in 76% with ES (p = 0.001). Patients with ES revealed increased VT recurrence rates during follow-up (65% vs. 40%; log rank p = 0.001; HR 1.841, 95% CI 1.289–2.628; p = 0.001). Furthermore, ES patients suffered from increased rehospitalization rates (73% vs. 48%; log rank p = 0.001; HR 1.948, 95% CI 1.415–2.682; p = 0.001) and cardiovascular mortality (18% vs. 9%; log rank p = 0.045; HR 1.948, 95% CI 1.004–3.780; p = 0.049). After multivariable adjustment, ES was a strong independent predictor of VT recurrence and rehospitalization rates, but not for mortality. In a propensity score-matched cohort, patients with ES still had a higher risk of VT recurrences and rehospitalizations compared to non-ES patients. Conclusions: VT ablation in patients with ES is challenging and these patients reveal the highest risk for recurrent VTs, rehospitalization and cardiovascular mortality. These patients need close follow-ups and optimal guideline-directed therapy.

Best Practices for the Catheter Ablation of Ventricular Arrhythmias

Techniques for catheter ablation have evolved to effectively treat a range of ventricular arrhythmias. Pre-operative electrocardiographic and cardiac imaging data are very useful in understanding the arrhythmogenic substrate and can guide mapping and ablation. In this review, we focus on best practices for catheter ablation, with emphasis on tailoring ablation strategies, based on the presence or absence of structural heart disease, underlying clinical status, and hemodynamic stability of the ventricular arrhythmia. We discuss steps to make ablation safe and prevent complications, and techniques to improve the efficacy of ablation, including optimal use of electroanatomical mapping algorithms, energy delivery, intracardiac echocardiography, and selective use of mechanical circulatory support.

Monomorphic VT Non-Inducibility after Electrical Storm Ablation Reduces Mortality and Recurrences

Background: Electrical storm (ES) is defined by clustering episodes of ventricular tachycardia (VT) and is associated with severe long-term outcomes. We sought to evaluate the prognostic impact of radiofrequency catheter ablation (RFCA) in ES as assessed by aggressive programmed ventricular stimulation (PVS). Methods: Single-center retrospective longitudinal study with 82 consecutive ES patients referred for RFCA with a median follow-up (IQR 25−75%) of 45.43 months (15−69.86). All-cause mortality and VT recurrences were assessed in relation to RFCA outcomes defined by 4-extrastimuli PVS: Class 1—no ventricular arrhythmia; Class 2—no sustained monomorphic VTs (mVT) inducible, but non-sustained mVTs, polymorphic VTs, or VF inducible; Class 3—clinical VT non-inducible, other sustained mVTs inducible; and Class 4—clinical VT inducible. Results: Class 1, Class 2, Class 3, and Class 4 were achieved in 56.1%, 13.4%, 23.2%, and 7.4% of cases, respectively. The combined outcome of Class 1 + Class 2 (no sustained monomorphic VT inducible) led to improved survival (log-rank p < 0.001) and reduced VT recurrence (log-rank p < 0.001). Residual monomorphic VT inducibility (HR 6.262 (95% CI: 2.165−18.108, p = 0.001), NYHA IV heart failure symptoms (HR 20.519 (95% CI: 1.623−259.345), p = 0.02)), and age (HR 1.009 (95% CI: 1.041−1.160), p = 0.001)) independently predicted death during follow-up. LVEF was not predictive of death (HR 1.003 (95% CI: 0.946−1.063) or recurrences (HR 0.988 (95% CI: 0.955−1.021)). Conclusions: Non-inducibility for sustained mVTs after aggressive PVS post-RFCA leads to improved survival in ES, independently of LVEF.

Newer Methods for VT Ablation and When to Use Them

Radiofrequency (RF) catheter ablation has long been an important therapy for ventricular tachycardia and frequent symptomatic premature ventricular beats and nonsustained arrhythmias when antiarrhythmic drugs fail to suppress the arrhythmias. It is increasingly used in preference to antiarrhythmic drugs, sparing the patient drug adverse effects. Ablation success varies with the underlying heart disease and type of arrhythmia, being very effective for patients without structural heart disease, less in structural heart disease. Failure occurs when a target for ablation cannot be identified, or ablation lesions fail to reach and abolish the arrhythmia substrate that may be extensive, intramural or subepicardial in location. Approaches to improving ablation lesion creation are modifications to RF ablation and emerging investigational techniques. Easily implemented modifications to RF methods include manipulating the size and location of the cutaneous dispersive electrode, increasing RF delivery duration, and use of lower tonicity catheter irrigation (usually 0.45% saline). When catheters can be placed on either side of culprit substrate RF can be delivered in a bipolar or simultaneous unipolar configuration that can be successful. Catheters with extendable/retractable irrigated needles for RF delivery are under investigation in clinical trials. Cryoablation is potentially useful in specific situations when maintaining contact is difficult. Transvascular ethanol ablation and stereotactic radioablation have both shown promise for arrhythmias that fail other ablation strategies. Although substantial clinical progress has been achieved, further improvement is clearly needed. With ability to increase ablation lesion size, continued careful evaluation of safety, which has been excellent for standard RF ablation, remains important.

Dynamic High-density Functional Substrate Mapping Improves Outcomes in Ischaemic Ventricular Tachycardia Ablation: Sense Protocol Functional Substrate Mapping and Other Functional Mapping Techniques

Post-infarct-related ventricular tachycardia (VT) occurs due to reentry over surviving fibres within ventricular scar tissue. The mapping and ablation of patients in VT remains a challenge when VT is poorly tolerated and in cases in which VT is non-sustained or not inducible. Conventional substrate mapping techniques are limited by the ambiguity of substrate characterisation methods and the variety of mapping tools, which may record signals differently based on their bipolar spacing and electrode size. Real world data suggest that outcomes from VT ablation remain poor in terms of freedom from recurrent therapy using conventional techniques. Functional substrate mapping techniques, such as single extrastimulus protocol mapping, identify regions of unmasked delayed potentials, which, by nature of their dynamic and functional components, may play a critical role in sustaining VT. These methods may improve substrate mapping of VT, potentially making ablation safer and more reproducible, and thereby improving the outcomes. Further large-scale studies are needed.

Arrhythmic Risk Profile and Outcomes of Patients Undergoing Cardiac Sympathetic Denervation for Recurrent Monomorphic Ventricular Tachycardia After Ablation

Background

Cardiac sympathetic denervation (CSD) has been used as a bailout strategy for refractory ventricular tachycardia (VT). Risk of VT recurrence in patients with scar‐related monomorphic VT referred for CSD and the extent to which CSD can modify this risk is unknown. We aimed to quantify arrhythmia recurrence risk and impact of CSD in this population.

Methods and Results

Adjusted competing risk time to event models were developed to adjust for risk of VT recurrence and sustained VT/implantable cardioverter–defibrillator shocks after VT ablation based on patient comorbidities at the time of VT ablation. Adjusted VT and implantable cardioverter–defibrillator shock recurrence rates were estimated for the subgroup who subsequently required CSD after ablation. The expected adjusted recurrence rates were then compared with the observed rates after CSD. Data from 381 patients with scar‐mediated monomorphic VT who underwent VT ablation were analyzed, excluding patients with polymorphic VT. Sixty eight patients underwent CSD for recurrent VT. CSD reduced the expected adjusted VT recurrence rate by 36% (expected rate of 5.61 versus observed rate of 3.58 per 100 person‐months, P=0.01) and the sustained VT/implantable cardioverter–defibrillator shock rates by 34% (expected rate of 4.34 versus observed 2.85 per 100 person‐months, P=0.03). The median number of sustained VT/implantable cardioverter–defibrillator shocks in the year before versus the year after CSD was reduced by 90% (10 versus 1, P<0.0001).

Conclusions

Patients referred for CSD for refractory scar‐mediated monomorphic VT are at a higher risk of VT recurrence after ablation as compared with those not requiring CSD, mostly because of their cardiac comorbidities. CSD significantly reduced both the expected risk of recurrences and VT burden.

Noninvasive programmed stimulation in the setting of ventricular tachycardia catheter ablation

In the setting of catheter ablation of ventricular tachycardia (VT), invasive programmed ventricular stimulation (PVS) is considered an important tool to assess the (residual) inducibility of ventricular arrhythmias and determine the acute success of the procedure. In patients with cardiovascular implantable electronic devices, noninvasive programmed stimulation via implantable cardioverter-defibrillator (ICD) leads can be an alternative to the invasive PVS with intracardiac catheters. The advantages of noninvasive programmed stimulation include preprocedure planning of the electrophysiology procedure to ensure optimal conditions for successful catheter ablation of VT. Following the procedure, noninvasive programmed stimulation has been shown to be used as a guide for repeat early ablation, to offer better programming of ICD, to offer prognostic value regarding the VT recurrence, and to guide antiarrhythmic drug therapy. The noninvasive nature of noninvasive programmed stimulation makes it an attractive alternative to PVS in patients with ICD who have not undergone catheter ablation of VT to obtain prognostic value regarding the occurrence of VT.