Nanostim leadless pacemaker retrieval and simultaneous micra leadless pacemaker replacement: a single-center experience.

PURPOSE: The leadless pacemaker (LP) is a promising new technology in pacing therapy that avoids a generator pocket and transvenous lead-related complications. However, extraction experience with simultaneous re-implant of a leadless device remains limited. We sought to study the outcomes of Nanostim LP retrieval and simultaneous reimplantation of Micra LP. METHODS: Patients undergoing retrieval of the Nanostim LP and receiving a Micra LP implant between 2016 and 2018 at Mayo Clinic (Rochester, MN) were studied. The procedural and outcome data were collected from the electronic medical record. RESULTS: Nine patients underwent attempted Nanostim LP retrieval and 6 of these simultaneously received a Micra LP reimplant. All retrievals were considered chronic due to implant durations of > 1 year. Extraction procedures were completed with a success rate of 89% and simultaneous reimplantations were performed successfully in all cases with no major complications. Newly implanted Micra LP device function was normal at follow-up. Factors such as duration of device implant and device positioning appeared to impact ease of extraction. CONCLUSIONS: Retrieval of the Nanostim LP system and simultaneous replacement with an alternate Micra leadless device appears to be a feasible approach.

Ventricular dyssynchrony assessment using ultra-high frequency ECG technique.

PURPOSE: The aim of this proof-of-concept study is to introduce new high-dynamic ECG technique with potential to detect temporal-spatial distribution of ventricular electrical depolarization and to assess the level of ventricular dyssynchrony. METHODS: 5-kHz 12-lead ECG data was collected. The amplitude envelopes of the QRS were computed in an ultra-high frequency band of 500-1000 Hz and were averaged (UHFQRS). UHFQRS V lead maps were compiled, and numerical descriptor identifying ventricular dyssynchrony (UHFDYS) was detected. RESULTS: An electrical UHFQRS maps describe the ventricular dyssynchrony distribution in resolution of milliseconds and correlate with strain rate results obtained by speckle tracking echocardiography. The effect of biventricular stimulation is demonstrated by the UHFQRS morphology and by the UHFDYS descriptor in selected examples. CONCLUSIONS: UHFQRS offers a new and simple technique for assessing electrical activation patterns in ventricular dyssynchrony with a temporal-spatial resolution that cannot be obtained by processing standard surface ECG. The main clinical potential of UHFQRS lies in the identification of differences in electrical activation among CRT candidates and detection of improvements in electrical synchrony in patients with biventricular pacing.

Effects of stepwise denervation of the stellate ganglion: Novel insights from an acute canine study.

BACKGROUND: The stellate ganglion (SG) is important for cardiac autonomic control. SG modification is an option for treating refractory ventricular tachyarrhythmias. The optimal extent of left- and right-sided SG denervation necessary for antiarrhythmic effect, however, remains to be learned. OBJECTIVE: The purpose of this study was to evaluate the effects of stepwise SG denervation on hemodynamic and electrophysiological parameters in dogs. METHODS: After sequential left and right thoracotomy in 8 healthy dogs, the SG was exposed by dissection. Two pacing wires were placed in the upper SG to deliver high-frequency stimulation. The lower SG, ansae subclaviae, and upper SG were removed in a stepwise manner. The same protocol was performed on the right side. Blood pressure (BP), heart rate, and electrophysiological parameters were recorded at baseline and after 5 minutes of stimulation. RESULTS: Systolic and diastolic BP significantly increased during stimulation of the upper left SG. The mean increase in systolic BP from baseline was 49.4 ± 26.6 mm Hg (P = .007), 25.5 ± 14.1 mm Hg after the lower SG was removed (P = .02), and 8.6 ± 3.4 mm Hg after resection of the ipsilateral ansae subclaviae (P = .048). Heart rate and other electrophysiological parameters did not change significantly. After the complete removal of the left SG, systolic BP increased by 34.0 ± 17.6 mm Hg (P = .005) after stimulation of the right SG. CONCLUSION: Sympathetic output remains after the lower SG is removed, and sympathetic output from the right SG remains after the complete resection of the left SG and ansae subclaviae. Thus, some patients who undergo left SG denervation can still have significant sympathetic response via right SG regulation.

Electroporation ablation of bronchial smooth muscle cells: A novel non-thermal asthma therapy.

OBJECTIVE: Asthma is a common disease which places significant burden on the US healthcare system and which can be associated with significant patient morbidity and mortality. Current medical therapies are costly and not curative. A new approach for a more permanent asthma treatment is the use of radiofrequency ablation. However, this radiofrequency approach is thermal-based and can result in deleterious effects to the airways, such as stenosis or ulceration. We describe a novel, improved therapeutic approach for smooth muscle ablation using non-thermal DC electroporation ablation. METHODS: We developed and tested prototype electroporation ablation devices that access the airways both endoscopically and via a bronchoscope. We tested the feasibility of this approach and demonstrated proof-of-concept in 2 mongrel dogs. In order to assess for smooth muscle function, we performed functional studies pre and post ablation with methacholine challenge to assess for airway reversibility. We also evaluated bronchial lesions via direct vision with bronchoscopy. RESULTS: We developed novel electroporation catheters to delivery energy to the bronchial smooth muscle through an endoscopic approach. We tested these catheters in 2 acute canine studies and successfully demonstrated the ability to destroy smooth muscle tissue via novel prototypes and saline irrigation for widespread non-thermal electroporation ablation. Our functional studies demonstrate the efficacy of this approach. CONCLUSION: We report a novel method for non-thermal bronchial smooth muscle ablation using novel prototypes and electroporation with normal saline. These early findings require further evaluation in larger, chronic canine studies to assess for use as a potential curative therapy.