Risk of arrhythmic events after alcohol septal ablation for hypertrophic cardiomyopathy using continuous implantable cardiac monitoring

Looking Back at 30 Years of Alcohol Septal Ablation and Looking Forward to the Future

In the 30 years since Dr Sigwart's first pioneering procedures, alcohol septal ablation (ASA) has become the standard catheterisation procedure to reduce or eliminate obstruction in the left ventricular outflow tract. This procedure reduces the pressure gradient by 70%-80%, and only 10%-20% of patients have a residual gradient > 30 mm Hg after ASA. The mortality rate of the procedure is < 1%, and ∼ 10% of patients require permanent pacemaker implantation for higher degrees of atrioventricular block. Given the potential risks, ASA should be performed only in centres with extensive experience in the treatment of hypertrophic cardiomyopathy and with comprehensive therapeutic options, including myectomy. In the future, ASA is likely to be increasingly complemented by catheter-based mitral valve repair, which will increase its efficacy.

Percutaneous Intramyocardial Septal Radiofrequency Ablation in Patients With Drug-Refractory Hypertrophic Obstructive Cardiomyopathy

Importance

Patients with hypertrophic obstructive cardiomyopathy (HOCM) and drug-refractory symptoms and outflow gradients have limited nonsurgical treatment options. The feasibility of percutaneous intramyocardial septal radiofrequency ablation (PIMSRA) has been reported previously; however, procedural and medium-term outcomes are unknown.

Objective

To describe the safety and medium-term outcomes of PIMSRA in a large patient cohort with drug-refractory HOCM.

Design, Setting, and Participants

This was a single-arm, open-label study of PIMSRA in patients with drug-refractory HOCM. Patients presenting to the Xijing Hospital in Xi'an, China, between October 2016 to June 2020 with hypertrophic cardiomyopathy. Of 1314 patients presenting with HOCM, 244 fulfilled inclusion criteria of severe resting/provoked outflow gradients of 50 mm Hg or higher, and symptoms of New York Heart Association functional class of II or higher refractory to maximum tolerated medications. After discussion among the heart team, 40 patients underwent surgical or alcohol septal reduction therapy and 4 required treatment of significant coronary artery disease.

Interventions

PIMSRA performed in patients.

Main Outcomes and Measures

The primary outcome was 30-day major adverse clinical events: death, emergency surgery, severe effusion requiring intervention, procedure-related stroke, bleeding, and stroke. Secondary outcomes included 30-day technical success and 90-day improvement in outflow obstruction.

Results

The mean (SD) age of 200 patients was 46.9 (14.0) years, and 125 (62.5%) were men. Resting or provoked left ventricular outflow tract gradients were 50 mm Hg or higher. The median (IQR) follow-up for all patients was 19 (6-50) months. Thirty-day major adverse clinical events rate was 10.5% (n = 21): there were 2 in-hospital/30-day deaths (1.0%), 7 patients (3.5%) with pericardial effusion requiring mini-thoracotomy, 12 patients (6%) with pericardial effusion requiring pericardiocentesis, and no bleeding or strokes. Other periprocedural complications included permanent right bundle branch block in 5 patients (2.5%), resuscitated ventricular fibrillation in 2 (1.0%), and septal branch aneurysm in 2 (1.0%). There were no permanent pacemaker implantations. At follow-up, maximum septal thickness was reduced from a mean (SD) of 24.0 (5.1) mm to 17.3 (4.4) mm (P < .001), and left ventricular outflow tract gradient was decreased from a mean (SD) of 79.0 (53.0) mm Hg to 14.0 (24.0) mm Hg (P < .001). Overall, 190 patients (96%) with HOCM were in New York Heart Association functional class I or II at last follow-up.

Conclusions and Relevance

This study found that PIMSRA in patients with drug-refractory HOCM may be an effective procedure for relief of left ventricular outflow tract obstruction and symptoms with acceptable complication rates. These results are encouraging and support the design of a randomized clinical trial against well-established septal reduction therapies.

Arrhythmia monitoring for risk stratification in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiomyopathy, presenting significant clinical heterogeneity. Arrhythmia risk stratification and detection are critical components in the evaluation and management of all cases of HCM. The 2020 American Heart Association/American College of Cardiology HCM guidelines provide new recommendations for periodic 24-48-hour ambulatory electrocardiogram monitoring to screen for atrial and ventricular arrhythmias. A strategy of more frequent or prolonged monitoring would lead to earlier arrhythmia recognition and the potential for appropriate treatment. However, whether such a strategy in patients with HCM results in improved outcomes is not yet established. The available evidence, knowledge gaps, and potential merits of such an approach are reviewed. Cardiac implantable electronic devices provide an opportunity for early arrhythmia detection, with the potential to enable early management strategies in order to improve outcomes.

Non-pharmaceutical Interventions for Hypertrophic Cardiomyopathy: A Mini Review

Hypertrophic cardiomyopathy is an inherited cardiovascular disease, and 70% of patients have left ventricular outflow tract obstruction. Ventricular septal myectomy has been the gold standard treatment for most patients with refractory symptoms. Due to higher mortality associated with medical facilities with less experience, alcohol septal ablation has been accepted as an alternative to conventional surgical myectomy. It offers lower all-cause in-hospital complications and mortality, which could be potentially more preferable for patients with serious comorbidities. In recent years, radiofrequency ablation, providing another option with reproducibility and a low risk of permanent atrioventricular block, has become an effective invasive treatment to relieve left ventricular outflow tract obstruction. Moreover, substantial progress has been made in gene therapy for hypertrophic cardiomyopathy. The principal objective of this review is to present recent advances in non-pharmaceutical interventions in hypertrophic cardiomyopathy.

Bluetooth-enabled implantable cardiac monitors and two-way smartphone communication for patients with hypertrophic cardiomyopathy

Background

Sudden cardiac death (SCD) risk stratification in hypertrophic cardiomyopathy (HCM) currently relies on arrhythmic burden quantification by 24 or 48-hour Holter monitoring. Whether this approach adequately captures arrhythmic burden, compared with longer-term continuous monitoring, is unclear. We sought to assess the long-term incidence of nonsustained ventricular tachycardia (NSVT) in HCM patients at low or moderate SCD risk, using implantable cardiac monitors (ICMs) paired with a novel Bluetooth-enabled 2-way communication platform.

Methods

This prospective, single-arm, observational study enrolled 33 HCM patients. Patients were implanted with an Abbott (Chicago, IL) Confirm Rx ICM and monitored using a protocolized care pathway.

Results

A total of 20 patients (60.6%) had ≥ 1 episode of NSVT recorded on the ICM, the majority of whom had previous Holter monitors that did not identify NSVT (60%, n = 12). A total of 71 episodes of NSVT were detected. Median time to first NSVT detection was 76.5 days (range: 0-553 days). A total of 19 patients underwent primary prevention implantable cardioverter defibrillator implantation during an average follow-up of 544 days (range: 42-925 days). A total of 172,112 automatic transmissions were received, and 65 (0.04%) required clinical follow-up. A total of 325 manual transmissions were received and managed. A total of 14 manual transmissions (4.3%) required follow-up, whereas 311 (95.7%) were managed solely with a text message.

Conclusions

Surveillance and reporting systems utilizing 2-way communication enabled by novel ICMs are feasible and allow remote management of patients with HCM. Prolonged monitoring with ICMs identified more patients with nonsustained arrythmias than did standard Holter monitoring. In many cases, this information impacted both SCD risk stratification and patient management.

High-intensity ultrasound catheter ablation achieves deep mid-myocardial lesions in vivo

BACKGROUND

Radiofrequency ablation of epicardial and mid-myocardial ventricular arrhythmias is limited by lesion depth.

OBJECTIVE

The purpose of this study was to generate deep mid-interventricular septal (IVS) lesions using high-intensity ultrasound (US) from an endocardial catheter-based approach.

METHODS

Irrigated US catheters (12 F) were fabricated with 3 × 5 mm transducers of 5.0, 6.5, and 8.0 MHz frequencies and compared in an ex vivo perfused myocardial ablation model. In vivo septal ablation in swine (n = 12) was performed via femoral venous access to the right ventricle. Lesions were characterized by echocardiography, cardiac magnetic resonance imaging, and electroanatomic voltage mapping pre- and post-ablation, and at 30 days. Four animals were euthanized immediately post-ablation to compare acute and chronic lesion histology and gross pathology.

RESULTS

In ex vivo models, maximal lesion depth and volume was achieved by 6.5 MHz catheters, which were used in vivo. Lesion depth by gross pathology was similar post-ablation (10.8 mm; 95% confidence interval [CI] 9.9-12.4 mm) and at 30 days (11.2 mm; 95% CI 10.6-12.4 mm) (P = .56). Lesion volume decreased post-ablation to 30 days (from 255 [95% CI 198-440] to 162 [95% CI 133-234] mm³; P = .05), yet transmurality increased from 58% (95% CI 50%-76%) to 81% (95% CI 74%-93%), attributable to a reduction in IVS thickness (from 16.0 ± 1.7 to 10.6 ± 2.4 mm; P = .007). Magnetic resonance imaging confirmed dense septal ablation by delayed enhancement, with increased T1 time post-ablation and at 30 days and increased T2 time only post-ablation. Voltage mapping of both sides of IVS demonstrated reduced unipolar (but not bipolar) voltage along the IVS.

CONCLUSION

High-intensity US catheter ablation may be an effective treatment of mid-myocardial or epicardial ventricular arrhythmias from an endocardial approach.