Evolving Concepts in Cardiac Physiologic Pacing in the Era of Conduction System Pacing.

Cardiac physiologic pacing (CPP) has become a well-established therapy for patients with cardiomyopathy (left ventricular ejection fraction <35%) in the presence of a left bundle branch block. In addition, CPP can be highly beneficial in patients with pacing-induced cardiomyopathy and patients with existing cardiomyopathy expected to have a right ventricular pacing burden of >40%. The benefits of CPP with traditional biventricular pacing are only realized if adequate resynchronization can be achieved. However, left ventricular lead implantation can be limited by individual anatomic variation within the coronary venous system and can be adversely affected by underlying abnormal myocardial substrate (i.e., scar tissue), especially if located within the basal lateral wall. In the last 7 years the investigation of conduction system pacing (CSP) and its potential salutary benefits are being realized and have led to a rapid evolution in the field of cardiac resynchronization pacing. However, supportive evidence for CSP for patients eligible for cardiac resynchronization remains limited compared with data available for biventricular cardiac resynchronization, mostly derived from leading CSP investigative centers. In this review, we perform an up-to-date comprehensive review of the available literature on CPP.

Wide area circumferential ablation for pulmonary vein isolation using radiofrequency versus laser balloon ablation.

Background: Persistent atrial fibrillation (AF) is associated with high recurrence rates of AF and atypical atrial flutters or tachycardia (AFT) postablation. Laser balloon (LB) ablation of the pulmonary vein (PV) ostia has similar efficacy as radiofrequency wide area circumferential ablation (RF-WACA); however, an approach of LB wide area circumferential ablation (LB-WACA) may further improve success rates. Objective: To evaluate freedom from atrial tachyarrhythmia (AFT/AF) recurrence postablation using RF-WACA versus LB-WACA in persistent AF patients. Methods: This was a retrospective multicenter study. Patients were followed for up to 24 months via office visits, Holter, and/or device monitoring. The primary endpoint was freedom from AFT/AF after a single ablation procedure. Secondary endpoints included freedom from AF, freedom from AFT, first-pass isolation of all PVs, and procedural complications. Results: Two hundred and four patients were studied (LB-WACA: n = 103; RF-WACA: n = 101). Patients' baseline characteristics were similar except patients in the RF-WACA group were older (64 vs. 68, p = .03). First-pass isolation was achieved more often during LBA (LB-WACA: 88% vs. RF-WACA 75%; p = .04). Procedure (p = .36), LA dwell (p = .41), and fluoroscopy (p = .44) time were similar. The mean follow-up was 506 ± 279 days. Sixty-six patients had arrhythmic events including 24 AFT and 59 AF recurrences. LB-WACA group had higher arrhythmia-free survival (p = .009) after single ablation procedures. In the multivariate Cox regression model, RF-WACA was associated with a higher recurrence of AFT compared with LB-WACA (Adjusted HR 3.16 [95% CI: 1.13-8.83]; p = .03). Conclusions: LB-WACA was associated with higher freedom from atrial arrhythmias mostly driven by the lower occurrence of AFT compared with RF-WACA.

Clinical outcomes of left bundle branch area pacing compared to right ventricular pacing: Results from the Geisinger-Rush Conduction System Pacing Registry.

BACKGROUND: Left bundle branch area pacing (LBBAP) has been shown to be a feasible option for patients requiring ventricular pacing. OBJECTIVE: The purpose of this study was to compare clinical outcomes between LBBAP and RVP among patients undergoing pacemaker implantation METHODS: This observational registry included patients who underwent pacemaker implantations with LBBAP or RVP for bradycardia indications between April 2018 and October 2020. The primary composite outcome included all-cause mortality, heart failure hospitalization (HFH), or upgrade to biventricular pacing. Secondary outcomes included the composite endpoint among patients with a prespecified burden of ventricular pacing and individual outcomes. RESULTS: A total of 703 patients met inclusion criteria (321 LBBAP and 382 RVP). QRS duration during LBBAP was similar to baseline (121 ± 23 ms vs 117 ± 30 ms; P = .302) and was narrower compared to RVP (121 ± 23 ms vs 156 ± 27 ms; P <.001). The primary composite outcome was significantly lower with LBBAP (10.0%) compared to RVP (23.3%) (hazard ratio [HR] 0.46; 95%T confidence interval [CI] 0.306-0.695; P <.001). Among patients with ventricular pacing burden >20%, LBBAP was associated with significant reduction in the primary outcome compared to RVP (8.4% vs 26.1%; HR 0.32; 95% CI 0.187-0.540; P <.001). LBBAP was also associated with significant reduction in mortality (7.8% vs 15%; HR 0.59; P = .03) and HFH (3.7% vs 10.5%; HR 0.38; P = .004). CONCLUSION: LBBAP resulted in improved clinical outcomes compared to RVP. Higher burden of ventricular pacing (>20%) was the primary driver of these outcome differences.

Electrocardiographic characteristics and ablation of ventricular arrhythmias originating from the basal inferoseptal area.

AIMS: Ventricular arrhythmias (VAs) from the basal inferoseptal (BIS) area are rare and can pose unique challenges during catheter ablation (CA) due to the anatomic complexity. The study sought to describe the electrocardiographic and clinical characteristics of VAs originating from the BIS area. METHODS AND RESULTS: Patients with VAs and successful ablation at the BIS area from 2016 to 2020 were included. The 12-lead electrocardiogram (ECG), intracardiac findings, and outcomes were analysed. Of 482 patients with VAs referred for CA, 17 (3.5%) had successful ablation at BIS area. There were 12 males, mean age was 66.7 ± 9 years, 82% had ejection fraction <50%. Mean baseline premature ventricular complex burden was 28.6 ± 9%. All patients had a leftward superior axis. Left bundle branch block (LBBB) with early transition in V2 was noted in eight patients and right bundle branch block (RBBB) in nine patients. Detailed mapping of the right ventricle (RV) was performed in 15 patients (88%), coronary sinus (CS)/middle cardiac vein (MCV) in 13 (76%), right atrium (RA) adjacent to the inferoseptal process (ISP) of left ventricle (LV) in 5 (29%), ISP-LV in 13 (76%), and epicardium in 2 (12%). Successful ablation site was in LV in 10 (59%), RV in 2 (12%), CS/MCV in 1 (6%), RA in 1 (6%), and epicardium in 2 (12%). Fifteen patients (88%) required mapping in at least two chambers (range 2-5) and seven patients (41%) required ablation in at least two chambers (range 2-3). CONCLUSIONS: Ventricular arrhythmias originating in the BIS are uncommon. The most common ECG patterns were leftward superior axis, LBBB with transition in V2 or RBBB. The VA foci can be endocardial or epicardial and meticulous mapping/ablation from multiple chambers is often required to eliminate these foci successfully.

Use of infrared thermography to delineate temperature gradients and critical isotherms during catheter ablation with normal and half normal saline: Implications for safety and efficacy.

BACKGROUND: Radiofrequency (RF) ablation with half-normal saline (HNS) has shown promise as a bail-out strategy following failed ventricular tachycardia ablation using standard approaches. OBJECTIVE: To use a novel infrared thermal imaging (ITI) model to evaluate biophysical and lesion characteristics during RF ablation using normal saline (NS) and HNS irrigation. METHODS: Left ventricular strips of myocardium were excised from fresh porcine hearts. RF ablation was performed using an open-irrigated ablation catheter (Thermocool ST/SF) with NS (n = 75) and HNS (n = 75) irrigation using different power settings (40/50 W), RF durations (30/60 s), contact force of 10-15 g, and flow rate of 15 ml/min. RF lesions were recorded using an infrared thermal camera and border zone, lethal, 100° isotherms were matched with necrotic borders after 2% triphenyltetrazolium chloride staining. Lesion dimensions and isotherms (mm2 ) were measured. RESULTS: In total, 150 lesions were delivered. HNS lesions were deeper (6.4 ± 1.1 vs. 5.7 ±0.8 mm; p = .03), and larger in volume (633 ± 153 vs. 468 ± 107 mm3 ; p = .007) than NS lesions. Steam pops (SPs) occurred during 19/75 lesions (25%) in the NS group and 32/75 lesions (43%) in the HNS group (p = .34). Lethal (57.8 ± 6.5 vs. 36.0 ± 3.9 mm2 ; p = .001) and 100°C isotherm areas (16.9 ± 6.9 vs. 3.8 ± 4.2 mm2 ; p = .003) areas were larger and were reached earlier in the HNS group. CONCLUSIONS: RFA using HNS created larger lesions than NS irrigation but led to more frequent SPs. The presence of earlier lethal isotherms and temperature rises above 100°C on ITI suggest a potentially narrower therapeutic-safety window with HNS.

Admission respiratory status predicts mortality in COVID-19.

COVID-19 has significant case fatality. Glucocorticoids are the only treatment shown to improve survival, but only among patients requiring supplemental oxygen. WHO advises patients to seek medical care for "trouble breathing," but hypoxemic patients frequently have no respiratory symptoms. Our cohort study of hospitalized COVID-19 patients shows that respiratory symptoms are uncommon and not associated with mortality. By contrast, objective signs of respiratory compromise-oxygen saturation and respiratory rate-are associated with markedly elevated mortality. Our findings support expanding guidelines to include at-home assessment of oxygen saturation and respiratory rate in order to expedite life-saving treatments patients to high-risk COVID-19 patients.

Spectrum of arrhythmogenic substrate post minimally invasive maze surgery in patients with recurrent.

BACKGROUND: Advancements in minimally invasive surgical ablation (MISA) have focused on improving pulmonary vein isolation. Additional ablation targets have been developed (such as posterior wall isolation). The mid- and long-term effects of current techniques (including electrophysiologic findings and recurrent arrhythmia mechanisms) have not previously been reported. METHODS: Twenty eight patients with recurrent atrial arrhythmias after bipolar clamp ablation of the pulmonary vein antrum, ganglionated plexi, posterior wall isolation (roof and floor lines to create a posterior box), and ligament of Marshall ligation/cauterization and left atrial appendage clipping underwent follow up electrophysiology study including left atrial mapping an average of 2.3 years postoperatively. RESULTS: Atrial fibrillation was the most common recurrent arrhythmia (n = 18) followed by micro-reentrant atrial tachycardia (n = 5), macro-reentry left atrial flutter (n = 3), and typical cavo-tricuspid isthmus atrial flutter (n = 2). Eighty six of 112 (77%) PVs mapped were electrically isolated, 16 (57%) patients had all four pulmonary veins (PVs) isolated. The posterior wall (PW) was completely isolated in only four (14%) patients, seven (25%) patients had normal PW voltage, while 17 (61%) patients had abnormal delayed or fractionated electrograms in the posterior wall (incomplete isolation). Abnormal PW electrograms were more frequently found in patients with complex recurrent left atrial arrhythmia (micro-reentry or left atrial macro-reentry flutter). CONCLUSION: With current surgical techniques PV isolation has improved, but PW isolation remains challenging. Incomplete PW isolation may produce arrhythmogenic substrate.

Cryoballoon Ablation and Bipolar Voltage Mapping in Patients With Left Atrial Appendage Occlusion Devices.

Left atrial appendage occlusion is utilized as a second line therapy to long-term oral anticoagulation in appropriately selected patients with atrial fibrillation (AF). We examined the feasibility of cryoballoon (CB) pulmonary vein isolation (PVI) subsequent to Watchman device implantation. The study prospectively identified patients with Watchman devices (>90 days old) who underwent CB-PVI ablation between 2018 and 2019. Twelve consecutive patients (male 50%; mean age 71 ± 9 years; CHA2DS2-VASc score 3.4 ± 1.1) underwent CB-PVI procedures after Watchman device implantation (mean 182 ± 82 days). Acute PVI was achieved in 100% of patients. All patients had evidence of complete (n = 9) or partial (n = 3) endothelialization of the surface of the Watchman device with conductive tissue properties demonstrated during electrophysiologic testing. There were no major procedure-related complications including death, stroke, pericardial effusion, device dislodgment, device thrombus, or new or increasing peri-device leak. Mean peri-device leak size (45-day postimplant: 0.06 ± 0.09 mm vs Post-PVI: 0.04 ± 0.06 mm; p = 0.61) remained unchanged. Two patients had recurrence of AF after the 90-day blanking period (13.2 ± 6.6 months). One patient underwent a redo ablation procedure for recurrent AF. This pilot study suggests the potential feasibility of CB-PVI ablation in patients with chronic Watchman left atrial appendage occlusion devices. Larger prospective studies are needed to confirm the clinical efficacy and safety of this approach.

Proarrhythmic effect of automatic threshold testing algorithm in dual chamber devices.

BACKGROUND: Operation of auto-threshold testing (ATT) algorithm in current dual chamber cardiac devices require temporary shortening of atrio-ventricular (AV) delay to accurately measure evoked potential (capture) after a pacing pulse. Near simultaneous AV pacing causes atrial pressure elevation and may be associated with atrial arrhythmias. OBJECTIVE: We evaluated the prevalence of atrial arrhythmias induced by ATT in Abbott devices. METHODS: Device clinic records were reviewed at a single center for patients with dual chamber Abbott pacemaker/ICD. ATT-induced atrial fibrillation (AF) cases were defined as new appropriate mode switch episodes while the ATT was operating. The auto-capture test trends were defined as unstable if there were deviations >1 V in capture threshold trend events that did not correlate with routine in-office testing. RESULTS: One hundred and seventy patients were programmed in dual chamber pacing mode. The ventricular ATT was active in 118 patients and of these 78 had true mode switch episodes. Six patients developed AF during ventricular ATT. Three patients had most recorded atrial arrhythmias in close association with ATT (63%, 66%, 100% vs 2%,9%, 33% in other patients with known prior AF). An unstable auto-capture trend curve was seen in 33 patients (6 showing ATT-induced AF) versus 85 patients with stable auto-capture curve and no ATT-induced AF (P = .0001, the χ2 test). CONCLUSION: Ventricular auto-capture algorithm use is associated with induction of AF in dual chamber Abbott devices with a prevalence of over 5%. AF occur more frequently (18%) in patients with erratic ventricular ATT trend results.

Supplemental Radiofrequency Ablation After Acutely Unsuccessful Cryoballoon Pulmonary Vein Isolation is Associated With Increased Risk of Recurrent Atrial Fibrillation.

Background Cryoballoon (CB) ablation is widely performed for pulmonary vein isolation (PVI) in patients with atrial fibrillation (AF). Anatomic variations in patient pulmonary vein (PV) anatomy are believed to impact short- and long-term procedural success of CB PVI. Methods and Results We hypothesized that failure of initial PV isolation with a standard technique (ie, requiring >2 freeze cycles per PV and/or radiofrequency ablation [RFA] to achieve PV isolation) during index CB PVI procedures would be associated with decreased freedom from AF. We examined a cohort of 177 consecutive patients with drug-refractory AF who underwent CB PVI with a 28-mm balloon second-generation CB device. Mean follow-up time was 19±9 months. Forty-three patients had AF recurrence after the 90-day blanking period after ablation. In 40 patients, acute isolation of one or more PVs could not be achieved by CB ablation with the standard technique (single freeze with or without bonus freeze). To obtain complete acute PVI, 15 patients received extra freeze applications, 20 required supplemental RFA, and 5 received both extra freeze applications and supplemental RFA. Multivariate regression analysis revealed supplemental RFA use during index CB PVI procedures was independently associated with a threefold increased risk of AF recurrence (adjusted hazard ratio, 3.01; 1.45-10.87; P=0.003). Conclusions Use of supplemental RFA during CB PVI procedures to assist with isolation of one or more PVs was independently associated with increased risk of AF recurrence. Use of additional freezes to achieve PVI did not increase the risk for recurrent AF.

Fluoroscopy reduction during device implantation by using three-dimensional navigation. A single-center experience.

BACKGROUND AND OBJECTIVES: The use of nonfluoroscopic three-dimensional electroanatomic mapping (3DM) systems reduces radiation exposure during ablation procedures. In this study, we sought to determine the value of 3DM during routine device implant procedures. METHODS: Seventy nonselected patients underwent implantation of a single chamber, dual chamber, or biventricular device guided by Ensite (Abbott Laboratories) to limit fluoroscopy use and compared with 70 consecutive patients, who underwent matching procedures with standard fluoroscopy use (FL) in the period immediately preceding the use of 3DM. The venous anatomy, right atrium, and ventricle and coronary sinus were mapped with 0.035 inch J-wire, quadripolar catheter, and/or angioplasty wire. The leads were advanced under real-time visualization in Ensite. RESULTS: 3DM reduced both fluoroscopy time and dose. Median fluoroscopy time for FL vs 3DM was 5.5 minutes (interquartile range [IQR]: 3.8-8.1) vs 0.9 minutes (IQR: 0.6-1.9) (P < .001) for single chamber devices, 6.3 minutes (IQR: 5.1-7.9) vs 3.3 minutes (IQR: 1.9-4) (P < .001) for dual-chamber devices, and 28.6 minutes (IQR: 19.6-36.2) to 14.7 minutes (IQR: 10.4-22.3) (P = .009) for biventricular devices, respectively. The median air kerma for FL vs 3DM was 15.4 mGy (IQR: 8.1-30.2) vs 4 mGy (IQR: 1.8-8) (P < .001) for single chamber devices, 16 mGy (IQR: 12-18.5) to 9.4 mGy (IQR: 7.5-11.3) (P = .001) for dual-chamber devices, and 324 mGy (IQR: 143-668.7) to 115 mGy (IQR:77-204) (P = .014) for biventricular devices, respectively. There were no procedural complications. At 3-month follow-up, there was no difference in voltage threshold measurements between the groups. CONCLUSION: The use of 3DM leads to significantly reduced fluoroscopy time and fluoroscopy dose during routine device implantation.