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.

Bipolar Electroporation Across the Interventricular Septum: Electrophysiological, Imaging, and Histopathological Characteristics.

BACKGROUND: Pulsed electric field (PEF) ablation is an emerging modality for the treatment of cardiac arrhythmias. Data regarding effects on the interventricular septum are limited, and the optimal delivery protocol and electrode configuration remain undefined. OBJECTIVES: This study sought to evaluate the electrophysiological, imaging, and histological characteristics of bipolar direct-current PEF delivered across the interventricular septum. METHODS: PEF was applied between identical solid-tip ablation catheters positioned on either side of the septum in a chronic canine model. Intracardiac and surface electrophysiological data were recorded following delivery. In 4 animals, cardiac magnetic resonance (CMR) was performed early (6 ± 2 days) and late (30 ± 2 days) postablation. After 4 weeks of survival, cardiac specimens were sectioned for histopathological analysis. RESULTS: In 8 canines, PEF was delivered in 27 separate septal sites (45 ± 17 J/site) with either microsecond or nanosecond PEF. Acute complications included transient complete atrioventricular block in 5 animals (63%) after delivery at the anterobasal septum, with right bundle branch block persisting in 3 (38%). Ventricular fibrillation occurred in 1 animal during microsecond but not nanosecond PEF. Postprocedural CMR showed prominent edema and significant left ventricular systolic dysfunction, which recovered with late imaging. At 4 weeks, 36 individual well-demarcated lesions were demonstrated by CMR and histopathology. Lesion depth measured by histology was 2.6 ± 2.1 mm (maximum 10.9 mm and near transmural). CONCLUSIONS: Bipolar PEF ablation of the interventricular septum is feasible and can produce near transmural lesions. Myocardial stunning, edema, and conduction system injury may occur transiently. Further studies are required to optimize safe delivery and efficacious lesions.

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.

Ventricular nanosecond pulsed electric field delivery using active fixation leads: a proof-of-concept preclinical study.

BACKGROUND: Mid-myocardial ventricular arrhythmias are challenging to treat. Cardiac electroporation via pulsed electric fields (PEFs) offers significant promise. We therefore tested PEF delivery using screw-in pacemaker leads as proof-of-concept. METHODS: In 5 canine models, we applied nanosecond PEF (pulse width 300 ns) across the right ventricular (RV) septum using a single lead bipolar configuration (n = 2) and between two leads (n = 3). We recorded electrograms (EGMs) prior to, immediately post, and 5 min after PEF. Cardiac magnetic resonance imaging (cMRI) and histopathology were performed at 2 weeks and 1 month. RESULTS: Nanosecond PEF induced minimal extracardiac stimulation and frequent ventricular ectopy that terminated post-treatment; no canines died with PEF delivery. With 1 lead, energy delivery ranged from 0.64 to 7.28 J. Transient ST elevations were seen post-PEF. No myocardial delayed enhancement (MDE) was seen on cMRI. No lesions were noted on the RV septum at autopsy. With 2 leads, energy delivery ranged from 56.3 to 144.9 J. Persistent ST elevations and marked EGM amplitude decreases developed post-PEF. MDE was seen along the septum 2 weeks and 1 month post-PEF. There were discrete fibrotic lesions along the septum; pathology revealed dense connective tissue with < 5% residual cardiomyocytes. CONCLUSIONS: Ventricular electroporation is feasible and safe with an active fixation device. Reversible changes were seen with lower energy PEF delivery, whereas durable lesions were created at higher energies. Central illustration: pulsed electric field delivery into ventricular myocardium with active fixation leads.

The 12-lead electrocardiogram as a biomarker of biological age.

Background: We have demonstrated that a neural network is able to predict a person's age from the electrocardiogram (ECG) [artificial intelligence (AI) ECG age]. However, some discrepancies were observed between ECG-derived and chronological ages. We assessed whether the difference between AI ECG and chronological age (Age-Gap) represents biological ageing and predicts long-term outcomes. Methods and results: We previously developed a convolutional neural network to predict chronological age from ECGs. In this study, we used the network to analyse standard digital 12-lead ECGs in a cohort of 25 144 subjects ≥30 years who had primary care outpatient visits from 1997 to 2003. Subjects with coronary artery disease, stroke, and atrial fibrillation were excluded. We tested whether Age-Gap was correlated with total and cardiovascular mortality. Of 25 144 subjects tested (54% females, 95% Caucasian) followed for 12.4 ± 5.3 years, the mean chronological age was 53.7 ± 11.6 years and ECG-derived age was 54.6 ± 11 years (R 2 = 0.79, P < 0.0001). The mean Age-Gap was small at 0.88 ± 7.4 years. Compared to those whose ECG-derived age was within 1 standard deviation (SD) of their chronological age, patients with Age-Gap ≥1 SD had higher all-cause and cardiovascular disease (CVD) mortality. Conversely, subjects whose Age-Gap was ≤1 SD had lower all-cause and CVD mortality. Results were unchanged after adjusting for CVD risk factors and other survival influencing factors. Conclusion: The difference between AI ECG and chronological age is an independent predictor of all-cause and cardiovascular mortality. Discrepancies between these possibly reflect disease independent biological ageing.

Implications of Neurological Status on Defibrillator Therapy and Long-Term Mortality of Sudden Cardiac Arrest Survivors.

OBJECTIVES: This study sought to investigate the impact of the neurological status of sudden cardiac arrest (SCA) survivors on implantable cardioverter-defibrillator (ICD) insertion and long-term mortality. BACKGROUND: The neurological status of SCA survivors may impact the decision to insert an ICD insertion and influence long-term survival. METHODS: In 1,433 survivors of SCA between 2002 and 2012, we examined the neurological status immediately after the arrest using the Pittsburgh Cardiac Arrest Category (PCAC) and prior to hospital discharge using the cerebral performance category (CPC) score. Patients were followed up to the endpoints of ICD implantation and all-cause mortality. RESULTS: Over a median follow-up period of 3.6 years, 389 (27%) patients received an ICD, and 674 (47%) died. The PCAC (adjusted hazard ratio [HR]: 0.79; 95% confidence interval [CI]: 0.69 to 0.90) and CPC (adjusted HR: 0.73; 95% CI: 0.64 to 0.84) scores were highly predictive of the time to ICD insertion and of all-cause mortality (PCAC score, adjusted HR: 1.39; 95% CI: 1.24 to 1.57; CPC score, adjusted HR: 2.03; 95% CI: 1.77 to 2.34). ICD therapy was associated with better survival even after adjusting for neurological status (HR: 0.56; 95% CI: 0.43 to 0.73). A significant proportion of patients in the worse CPC categories had a >1-year survival after the index SCA. CONCLUSIONS: In SCA survivors, worse neurological performance was associated with lower likelihood of ICD insertion and higher mortality. ICD insertion was associated with improved survival even after accounting for neurological performance. ICD discussion should therefore not be omitted in these patients.

Derivation and validation of a new score to predict long-term survival after sudden cardiac arrest.

BACKGROUND: There is insufficient information about the long-term prognosis of sudden cardiac arrest (SCA) survivors. We therefore derived a clinical score (Sudden Cardiac Arrest-mortality score, SCA-MS) that predicts long-term mortality in patients surviving to hospital discharge and validated it in an independent cohort of SCA survivors. METHODS: A total of 1433 SCA survivors data were collected, who were discharged from the hospitals of the University of Pittsburgh Medical Center between 2002 and 2012. The overall cohort was randomly divided into two near equal cohorts used for the derivation and validation of the SCA-MS, respectively. RESULTS: The derivation cohort included 768 patients and identified serum potassium level>4.2 mg/dL at admission, the presence of atrial fibrillation at any time during the index hospitalization, and the presence of asystole or pulseless electrical activity as the initial documented rhythm as independent predictors of long-term mortality. Based on the multivariable modeling result, one point was assigned to each one of these variables to create the SCA-MS that ranged from 0 to 3. In the validation cohort, the SCA-MS was predictive of long-term mortality (hazards ratio = 1.69, 95% confidence interval 1.50-1.91, P < 0.001) per 1-point increment in the SCA-MS. CONCLUSIONS: We describe a new clinical score that predicts long-term survival after SCA based on serum potassium levels at the admission, presence of atrial fibrillation, and documented rhythm of SCA.

Implantable Defibrillator Therapy in Cardiac Arrest Survivors With a Reversible Cause.

BACKGROUND: Current guidelines recommend implantable cardioverter-defibrillator (ICD) therapy in survivors of sudden cardiac arrest (SCA), except in those with completely reversible causes. We sought to examine the impact of ICD therapy on mortality in survivors of SCA associated with reversible causes. METHODS AND RESULTS: We evaluated the records of 1433 patients managed at our institution between 2000 and 2012 who were discharged alive after SCA. A reversible and correctable cause was identified in 792 (55%) patients. Reversible SCA cause was defined as significant electrolyte or metabolic abnormality, evidence of acute myocardial infarction or ischemia, recent initiation of antiarrhythmic drug or illicit drug use, or other reversible circumstances. Of the 792 SCA survivors because of a reversible and correctable cause (age 61±15 years, 40% women), 207 (26%) patients received an ICD after their index SCA. During a mean follow-up of 3.8±3.1 years, 319 (40%) patients died. ICD implantation was highly associated with lower all-cause mortality (P<0.001) even after correcting for unbalanced baseline characteristics (P<0.001). In subgroup analyses, only patients whose SCA was not associated with myocardial infarction extracted benefit from ICD (P<0.001). CONCLUSIONS: In survivors of SCA because of a reversible and correctable cause, ICD therapy is associated with lower all-cause mortality except if the SCA was because of myocardial infarction. These data deserve further investigation in a prospective multicenter randomized controlled trial, as they may have important and immediate clinical implications.

Effect of body mass index on survival after sudden cardiac arrest.

BACKGROUND: Although elevated body mass index (BMI) is a risk factor for cardiac disease, patients with elevated BMI have better survival in the context of severe illness, a phenomenon termed the "obesity paradox." HYPOTHESIS: Higher BMI is associated with lower mortality in sudden cardiac arrest (SCA) survivors. METHODS: Data were collected on 1433 post-SCA patients, discharged alive from the hospitals of the University of Pittsburgh Medical Center between 2002 and 2012. Of those, 1298 patients with documented BMI during the index hospitalization and follow-up data constituted the study cohort. RESULTS: In the overall cohort, 30 patients were underweight (BMI <18.5 kg/m2 ), 312 had normal weight (BMI 18.5-24.9 kg/m2 ), 417 were overweight (BMI 25.0-29.9 kg/m2 ), and 539 were obese (BMI ≥30 kg/m2 ). As expected, the prevalence of coronary artery disease, myocardial infarction, diabetes mellitus, and hypertension increased significantly with increasing BMI. Over a median follow-up of 3.6 years, 602 (46%) patients died. Despite higher prevalence of cardiovascular comorbidities in more obese patients, a higher BMI was associated with lower all-cause mortality on univariate analysis (hazard ratio: 0.86 per increase by 1 BMI category, 95% confidence interval: 0.78-0.94, P = 0.002) and multivariate analysis after adjusting for unbalanced baseline comorbidities (hazard ratio: 0.86 per increase by 1 BMI category, 95% confidence interval: 0.77-0.96, P = 0.009). CONCLUSIONS: Higher BMI is associated with lower all-cause mortality in survivors of SCA, suggesting that the obesity paradox applies to the post-arrest population. Further investigation into its mechanisms may inform the management of post-SCA patients.

Association of remote ischemic peri-conditioning with reduced incidence of clinical heart failure after primary percutaneous coronary intervention.

BACKGROUND: Clinical heart failure (HF) occurs frequently after ST-segment elevation myocardial infarction (STEMI), and is associated with increased mortality. We assessed the impact of remote ischemic peri-conditioning (RIPC) during inter-facility air medical transport of STEMI patients on clinical HF following primary percutaneous coronary intervention (pPCI). METHODS: Data from Acute Coronary Treatment and Intervention Outcomes Network Registry®-Get With the Guidelines™ (ACTION Registry-GWTG) from two PCI-hospitals that are utilizing RIPC during inter-facility helicopter transport of STEMI patients for pPCI between March, 2013 and September, 2015 were used for this study. The analyses were limited to inter-facility STEMI patients transported by helicopter with LVEF <55% after pPCI. The outcome measures were occurrence of clinical HF and serum level of brain-type natriuretic peptide (BNP). RESULTS: Out of the 150 STEMI patients in this analysis, 92 patients received RIPC and 58 did not. The RIPC and non-RIPC groups were generally similar in demographic and clinical characteristics except for lower incidence of cardiac arrest in the RIPC group (3/92 [3.3%] versus 13/58 [22.4%], p=0.002). STEMI patients who received RIPC were less likely to have in-hospital clinical HF compared to patients who did not receive RIPC (3/92 [3.3%] versus 7/58 [12.1%]; adjusted OR=0.22, 95% CI 0.05-0.92, p=0.038) after adjusting for baseline differences. In subgroup analysis, RIPC was associated with lower BNP (123 [interquartile range, 17.0-310] versus 319 [interquartile range, 106-552], p=0.029). CONCLUSION: RIPC applied during inter-facility air transport of STEMI patients for pPCI is associated with reduced incidence of clinical HF and serum BNP.

Renal Protection Using Remote Ischemic Peri-Conditioning During Inter-Facility Helicopter Transport of Patients With ST-Segment Elevation Myocardial Infarction: A Retrospective Study.

OBJECTIVE: To assess the impact of remote ischemic peri-conditioning (RIPC) during inter-facility air medical transport of ST-segment elevation myocardial infarction (STEMI) patients on the incidence of acute kidney injury (AKI) following primary percutaneous coronary intervention (pPCI). BACKGROUND: STEMI patients who receive pPCI have an increased risk of AKI for which there is no well-defined prophylactic therapy in the setting of emergent pPCI. METHODS: Using the ACTION Registry-GWTG, we evaluated the impact of RIPC applied during inter-facility helicopter transport of STEMI patients from non-PCI capable hospitals to 2 PCI-hospitals in the United States between March, 2013 and September, 2015 on the incidence of AKI following pPCI. AKI was defined as ≥0.3 mg/dL increase in creatinine within 48-72 hours after pPCI. RESULTS: Patients who received RIPC (n = 127), compared to those who did not (n = 92), were less likely to have AKI (11 of 127 patients [8.7%] vs. 17 of 92 patients [18.5%]; adjusted odds ratio = 0.32, 95% CI 0.12-0.85, P = 0.023) and all-cause in-hospital mortality (2 of 127 patients [1.6%] vs. 7 of 92 patients [7.6%]; adjusted odds ratio = 0.14, 95% CI 0.02-0.86, P = 0.034) after adjusting for socio-demographic and clinical characteristics. There was no difference in hospital length of stay (3 days [interquartile range, 2-4] vs. 3 days [interquartile range, 2-5], P = 0.357) between the 2 groups. CONCLUSION: RIPC applied during inter-facility helicopter transport of STEMI patients for pPCI is associated with lower incidence of AKI and in-hospital mortality. The use of RIPC for renal protection in STEMI patients warrants further in depth investigation.