Effects of Pulsed Electric Fields on the Coronary Arteries in Swine.

BACKGROUND: Previous animal studies have shown no significant vascular injury from pulsed electrical field (PEF) ablation. We sought to assess the effect of PEF on swine coronary arteries. METHODS: We performed intracoronary and epicardial (near the coronary artery) PEF ablations in swine pretreated with dual antiplatelet and antiarrhythmic therapy. Intracoronary PEF was delivered using MapiT catheters (Biotronik, Berlin), whereas epicardial PEF was delivered using EPT catheters (Boston Scientific, MA). PEF pulse duration was microseconds (Nanoknife 3.0, Angio Dynamics, NY) or nanoseconds (CellFX, Pulse Biosciences, CA). RESULTS: We performed 39 intracoronary ablations in 10 swine and 20 epicardial-pericoronary ablations in 4 separate swine. Intracoronary PEF was delivered at higher energy compared with epicardial PEF (46 [interquartile range, IQR 20-85] J versus 10 [IQR 10-11] J, P < 0.01). Reversible coronary spasm occurred in 49% intracoronary ablations and 45% epicardial ablations (P=0.80). At the end study, fixed coronary stenosis was demonstrated in 44% intracoronary ablations (80% for microsecond PEF and 18% for nanosecond PEF) and 0% epicardial ablations. Visible hemorrhagic and/or fibrotic myocardial lesions were observed at necropsy with similar frequency between intracoronary and epicardial PEF (45% versus 50%, P=0.70). Nanosecond PEF (49 ablations in 11 swine), when compared with microsecond PEF (10 intracoronary ablations in 3 swine), resulted in lower energy delivery (21 [IQR 10-46] J versus 129 [IQR 24-143] J, P=0.03) and less incidence of fixed coronary stenosis (18% versus 80%, P=0.04). CONCLUSIONS: In the swine model, intracoronary PEF resulted both in significant coronary spasm and fixed coronary stenosis. Epicardial PEF, delivered at lower energy, resulted in reversible spasm but no fixed coronary stenosis.

Open-chest Pulsed Electric Field Ablation of Cardiac Ganglionated Plexi in Acute Canine Models.

This study aimed to evaluate the safety and acute effect on markers of cardiac autonomic tone following pulsed electric fields (PEFs) delivered to epicardial ganglionated plexi (GP) during a cardiac surgical procedure. Ablation of GP as a treatment for atrial fibrillation (AF) has shown promise, but thermal ablation energy sources are limited by the risk of inadvertent collateral tissue injury. In acute canine experiments, median sternotomy was performed to facilitate the identification of 5 epicardial GP regions using an anatomy-guided approach. Each site was targeted with saline-irrigated PEF (1000 V, 100 µs, 10 electrocardiogram [ECG]-synchronized pulse sequences). Atrial effective refractory period (AERP) and local electrogram (EGM) amplitude were measured before and after each treatment. Histology was performed on samples from treatment-adjacent structures. In 5 animals, 30 (n = 2) and 60 (n = 3) pulses were successfully delivered to each of the 5 target sites. There was no difference in local atrial EGM amplitude before and after PEF application at each site (1.83 ± 0.41 vs. 1.92 ± 0.53 mV, P = .72). The mean AERP increased from 97 ± 15 ms at baseline to 115 ± 7 ms following treatment at all sites (18.6% increase; 95% confidence interval, 1.9-35.2; P = .037). There were no sustained ventricular arrhythmias or acute evidence of ischemia following delivery. Histology showed complete preservation of adjacent atrial myocardium, phrenic nerves, pericardium, and esophagus. Use of PEF to target regions rich in cardiac GP in open-chest canine experiments was feasible and effective at acutely altering markers of cardiac autonomic tone.

Current Surgical Risk Scores Overestimate Risk in Minimally Invasive Aortic Valve Replacement.

OBJECTIVE: Risk-scoring systems for surgical aortic valve replacement (AVR) were largely derived from sternotomy cases. We evaluated the accuracy of current risk scores in predicting outcomes after minimally invasive AVR (mini-AVR). Because transcatheter AVR (TAVR) is being considered for use in low-risk patients with aortic stenosis, accurate mini-AVR risk assessment is necessary. METHODS: We reviewed 1,018 consecutive isolated mini-AVR cases (2009 to 2015). After excluding patients with Society of Thoracic Surgeons Predicted Risk of Mortality (STS-PROM) scores ≥4, we calculated each patient's European System for Cardiac Operative Risk Evaluation (EuroSCORE) II, TAVR Risk Score (TAVR-RS), and age, creatinine, and ejection fraction score (ACEF). We compared all 4 scores' accuracy in predicting mini-AVR 30-day mortality by computing each score's observed-to-expected mortality ratio (O:E). Area under the receiver operating characteristic (ROC) curves tested discrimination, and the Hosmer-Lemeshow goodness-of-fit tested calibration. RESULTS: Among 941 patients (mean age, 72 ± 12 years), 6 deaths occurred within 30 days (actual mortality rate, 0.6%). All 4 scoring systems overpredicted expected mortality after mini-AVR: ACEF (1.4%), EuroSCORE II (1.9%), STS-PROM (2.0%), and TAVR-RS (2.1%). STS-PROM best estimated risk for patients with STS-PROM scores 0 to <1 (0.6 O:E), ACEF for patients with STS-PROM scores 2 to <3 (0.6 O:E), and TAVR-RS for patients with STS-PROM scores 3 to <4 (0.7 O:E). ROC curves showed only fair discrimination and calibration across all risk scores. CONCLUSIONS: In low-risk patients who underwent mini-AVR, current surgical scoring systems overpredicted mortality 2-to-3-fold. Alternative dedicated scoring systems for mini-AVR are needed for more accurate outcomes assessment.