First-in-man clinical implantation and acute pacing performance of a novel subxiphoidal pacemaker system.

BACKGROUND: Intravascular cardiac pacemakers are an established therapy for bradycardic indications. Recently, a new class of leadless pacemakers have mitigated some of the complications related to pacemaker leads. In this study, we evaluate the implantation and performance of a novel extravascular technology that delivers epicardial pacing through a subxiphoidal approach. METHODS: Fifteen patients undergoing non-emergent open-heart surgery were enrolled. A midline incision was made just below the xiphoid process, and substernal tunneling was used to create a pocket for the device and to access the anterior pericardium over the right ventricle. The test device (Calyan Technologies, Oakdale, MN) was temporarily inserted underneath the ribcage and clipped to the xiphoid process. The sensing and pacing electrode (FlexArm) was positioned on the anterior pericardium. Ventricular sensing and pacing capture thresholds were measured. RESULTS: The test device was successfully implanted in all 15 patients. There were no device or procedure-related adverse events. The first five implanted patients had no pacing capture at maximum stimulation intensity. Design changes were made to the device, including different electrode size and shape, and successful ventricular capture was achieved in 9 of the subsequent 10 patients. In these patients, pacing threshold was 3.8 ± 1.6 mA with a pulse width of 0.5 ms. All devices were successfully explanted at the end of the procedure. CONCLUSIONS: In a first-in-human experience with a novel extravascular pacemaker, this study demonstrated the feasibility of pericardial ventricular pacing via a subxiphoidal approach. Further chronic studies are required to evaluate the safety and performance of this novel pacing technology.

Safety and performance of a novel subxiphoidal pacemaker system.

BACKGROUND: Traditional cardiac pacemakers commonly have a range of complications related to the presence of intracardiac leads. A new class of extravascular and leadless pacemakers has recently emerged with the potential to mitigate these complications and expand access to cardiac pacing. The objective of this study is to evaluate the implantation, short-term chronic safety, and performance of a novel subxiphoidal extracardiac pacemaker. METHODS: Normal Yorkshire Cross swine (n = 16) were implanted with the subxiphoidal pacemaker. The pacemaker was inserted through a midline chest incision and clipped to the underside of the sternum, with the stimulation electrode placed on the anterior pericardium. Animals were chronically paced and followed for 90 days post-implant, with periodic measurement of pacing capture threshold (PCT) and electrode impedance. RESULTS: All 16 animals were successfully implanted with the study device. At implant, a consistent average PCT of 2.2 ± 0.4 V at a pulse width of 1.0 ms was observed in all animals, with an average implant impedance of 648 ± 44 Ω. Chronic pacing was programmed at a rate of 60 bpm, an amplitude of 3.4 ± 0.7 V, and a pulse width of 1.0 ms. PCT rose to 4.6 ± 0.8 V at 14 days and stabilized; at 90 days, PCT was 3.8 ± 1.2 V and electrode impedance was 533 ± 105 Ω. All implanted animals completed the study with no clinically significant findings, no clinically significant abnormalities, and with no adverse events that affected animal welfare. CONCLUSIONS: This study demonstrated the safety and feasibility of a novel subxiphoidal extracardiac pacemaker to deliver short-term chronic extravascular therapy. Further studies are required to assess the safety, feasibility, and long-term chronic pacing performance in human subjects.

Epicardial ablation of ventricular tachycardia in ischemic cardiomyopathy: A review and local experience.

Myocardial scar in ischemic cardiomyopathy is predominantly endocardial, however, between 5% and 15% of these patients have an arrhythmogenic epicardial substrate. Percutaneous epicardial ablation should be considered in patients with ICM and VT especially if they failed an endocardial ablation. Simultaneous epicardial and endocardial ablation of VT in ICM may reduce short- and medium-term VT recurrence compared with an endocardial only approach. Cardiac imaging could be used to help guide patient selection for a combined epi-endo approach. Complications related to epicardial access can happen in up to 7% of patients. Epicardial ablation in these patients should be referred to experienced tertiary centers. We review the literature and share interesting cases.

Premature Ventricular Complexes: Benign versus Malignant - How to approach?

Premature Ventricular Complexes (PVCs) refer to electrical activity arising from ventricles resulting in ventricular contraction independent of the native rhythm. PVCs by themselves are common in the general population but based on the origin of the PVCs, either related to anatomical or electrical substrate, the disease process has a widely varied presentation and prognosis. The clinical presentation of symptoms may vary from being extremely benign, or very severe (malignant). Benign PVCs include those that are asymptomatic or induce very mild symptoms including palpitations, lightheadedness, chest discomfort, or the sensation of skipped beats. The middle range of PVCs present as heart failure or heart failure complicated by PVCs. The malignant variety may present as syncope, or sudden cardiac death. In this review we describe the multiple facets of PVC presentation and strategies of clinical management.

Ripple Frequency Determined via a Novel Algorithm Is Associated With Atrial Fibrillation Termination and Freedom From Atrial Fibrillation.

Background: Persistent atrial fibrillation (AF) is a complex arrhythmia, and attaining freedom from AF with ablation has been challenging. Objectives: This study evaluated a novel CARTO software algorithm based on the CARTO Ripple map for AF termination and 18-month freedom from AF. Methods: Consecutive patients who underwent first-time ablation for persistent AF were included. A high-density Ripple map was created using a Pentaray catheter. Following PVI, ablation was performed at locations with rapid Ripple activations, a protocol previously described by us. Patients were followed for 18 months to assess rhythm outcomes. A retrospective analysis was performed using the CARTO Ripple frequency software algorithm. The Ripple frequency algorithm quantifies amplitude changes in the bipolar electrogram. Results: A total of 115 AF maps were analyzed from 84 patients (mean age 65.9 years, 63.1% men). The top quartile of Ripple frequency corresponded to a visual reference with 96.7% sensitivity and 91.1% specificity. AF terminated during ablation in 88.1% of patients: pulmonary vein antrum alone (14.9%) or pulmonary vein plus nonantral sites (85.1%). The top quartile of Ripple frequency was present in nonantral areas associated with AF termination with 90.2% sensitivity and 86.5% specificity. After 14.0 ± 6.5 months and 1.2 ± 0.4 ablations, 78 (92.9%) of 84 patients were free of AF, and 79.8% were free of any atrial arrhythmia. Conclusion: A novel algorithm for automated analysis of CARTO Ripple frequency demonstrated good sensitivity and specificity for detecting atrial regions in persistent AF in which ablation is associated with frequent AF termination and freedom from AF during follow-up.

Catheter ablation of ventricular tachycardia in patients with prior cardiac surgery: An analysis from the International VT Ablation Center Collaborative Group.

INTRODUCTION: Patients with prior cardiac surgery may represent a subgroup of patients with ventricular tachycardia (VT) that may be more difficult to control with catheter ablation. METHODS: We evaluated 1901 patients with ischemic and nonischemic cardiomyopathy who underwent VT ablation at 12 centers. Clinical characteristics and VT radiofrequency ablation procedural outcomes were assessed and compared between those with and without prior cardiac surgery. Kaplan-Meier analysis was used to estimate freedom from recurrent VT and survival. RESULTS: There were 578 subjects (30.4%) with prior cardiac surgery identified in the cohort. Those with prior cardiac surgery were older (66.4 ± 11.0 years vs. 60.5 ± 13.9 years, p < .01), with lower left ventricular ejection fraction (30.2 ± 11.5% vs. 34.8 ± 13.6%, p < .01) and more ischemic heart disease (82.5% vs. 39.3%, p < .01) but less likely to undergo epicardial mapping or ablation (9.0% vs. 38.1%, p<.01) compared to those without prior surgery. When epicardial mapping was performed, a significantly greater proportion required surgical intervention for access (19/52 [36.5%] vs. 14/504 [2.8%]; p < .01). Procedural complications, including epicardial access-related complications, were lower (5.7% vs. 7.0%, p < .01) in patients with versus without prior cardiac surgery. VT-free survival (75.1% vs. 74.1%, p = .805) and survival (86.5% vs. 87.9%, p = .397) were not different between those with and without prior heart surgery, regardless of etiology of cardiomyopathy. VT recurrence was associated with increased mortality in patients with and without prior cardiac surgery. CONCLUSION: Despite different clinical characteristics and fewer epicardial procedures, the safety and efficacy of VT ablation in patients with prior cardiac surgery is similar to others in this cohort. The incremental yield of epicardial mapping in predominant ischemic cardiomyopathy population prior heart surgery may be low but appears safe in experienced centers.

Epicardial Ablation via Arterial and Venous Systems.

The intracoronary artery and venous routes provide unique roadmaps for mapping and interventions for ventricular arrhythmias and certain atrial arrhythmias. The unique anatomic location of these vessels on the epicardial surface enables mapping/interventions without the need to access the pericardial space. These anatomic routes also track deep into certain intramural regions, with interventions that are not accessible from either epicardial or endocardial routes. To map smaller vessels, multipolar catheters and wires are used to record local electrograms. Endocardial/epicardial ablation at adjacent sites is sometimes required to enhance successful outcomes. This article describes tools, techniques, and site-specific mapping and interventions.

QTc dispersion as a novel marker in identifying patients requiring an epicardial approach for ablation of scar mediated ventricular tachycardia.

INTRODUCTION: Epicardial exit sites of ventricular tachycardia (VT) are frequently encountered during VT ablation requiring an epicardial ablation approach for successful elimination of VT. We sought to assess the utility of repolarization markers in identifying individuals requiring an epicardial ablation approach in addition to an endocardial approach. METHODS: 32 patients who underwent successful ablation for scar mediated VT were included in the study. Fourteen patients who required a combined endocardial and epicardial VT ablation were defined as epicardial VT group (Epi) whereas 18 patients who were successfully ablated from the endocardium alone constituted the endocardial VT group (Endo). Repolarization markers during sinus rhythm were compared between the two groups. RESULTS: A higher QTc max and QTc dispersion were seen in the Epi group compared to Endo group (479 ± 34 vs 449 ± 20, p = 0.008 and 63 ± 13 vs 38 ± 8, p = 0.001, respectively). Ts-p and Ts-p/Tp-e were higher in the Epi group (166 ± 23 vs 143 ± 23, p = 0.008 and 1.55 ± 0.26 vs 1.3 ± 0.21, p < 0.005). On multivariate regression, QTc dispersion was an independent predictor of the need for an epicardial approach to ablation. A QTc dispersion more than 51.5 msec identified individuals requiring a combined epicardial and endocardial approach to ablation with a sensitivity of 92.9% and a specificity of 100%. CONCLUSIONS: Patients requiring an epicardial ablation have a higher QTc dispersion. A value greater than 51.5 msec reliably differentiates between the two groups with high sensitivity and specificity.

Permanent Pacemaker Lead Insertion Connected to an External Pacemaker Generator for Temporary Pacing After Transcatheter Aortic Valve Implantation.

BACKGROUND: Outcomes after transcatheter aortic valve implantation (TAVI) have been demonstrated to be at least equivalent in the short term compared to surgical valve implantation (SAVI). However, Conduction abnormalities are more common after TAVI than SAVI and the need for permanent pacemaker implantation is more common after TAVI with the currently commercially available self-expanding valves than after SAVI. Temporary pacemaker implantation may be associated with inability to ambulate, lead migration or perforation and infection. Depending on the monitoring system, some arrhythmias may not be detected. We examined the feasibility and safety of permanent pacemaker lead implantation connected to an external generator in patients undergoing TAVI at our institution. METHODS: This is a retrospective analysis of consecutive patients (between April 1st 2014 and April 30th 2016) at a single center without permanent pacemaker at the time of TAVI who underwent implantation of a permanent pacemaker lead after TAVI connected to an external generator. Focus was the examination of feasibility and safety of our aforementioned approach. In addition, data analysis was performed separating patients into two groups depending on whether (group 1) or not (group 2) permanent pacemaker implantation was ultimately needed. RESULTS: Per our institutional protocol, all consecutive 114 patients underwent insertion of a permanent pacemaker lead after TAVI connected to an external generator. There was one pericardial effusion on postoperative day one that may have been related to the left ventricular wire for TAVI valve delivery. However, perforation due to the pacemaker lead cannot be excluded. Specifically, no access site complications, lead dislodgments or infections occurred. All patients were able to ambulate after the procedure without delay. The permanent pacemaker lead remained in place on average for 4.3 days in group 1 (n = 10) and 4.4 days in group 2 (n = 104) (variance of 3.8 and 3.4 days respectively, [minimum/maximum 0/11 days and 1 and 12 days]). Of the ten patients (9%) who required permanent pacemaker implantation, 8 had a complete atrioventricular block and two had tachy-brady arrhythmias in the context of atrial fibrillation. None of the baseline characteristics including baseline conduction abnormalities were predictors for PPI. CONCLUSION: Implantation of a permanent pacemaker lead connected to an external generator is feasible and safe and could be a better option than implantation of a temporary lead connected to an external generator. It may allow earlier ambulation and facilitate monitoring.

Characteristics and periodicity of sustained ventricular tachyarrhythmia events in a population of military veterans with implantable cardioverter defibrillator.

PURPOSE: Circadian patterns of ventricular tachyarrhythmias (VTAs) in ICD patients from SCD-HeFT and MADIT-CRT have yielded differing results. The aim was to investigate VTA patterns in a large population of military veterans with ICD. METHODS: This retrospective study analyzed biorhythm periodicity of sustained VTAs (≤ 300 ms). Findings were derived from the Veterans Affairs (VA) National Cardiac Device Surveillance database encompassing January 1, 2005, to December 31, 2017. RESULTS: The patient population comprised 1559 consecutive patients with 17,039 VTAs. There were 763 patients with clinical information with the mean age of 67.8 ± 9 years old and 99% male. An hourly non-uniform VTA distribution with a bimodal pattern and a predominant afternoon peak was seen (χ2 = 5057, P < 0.0001). VTAs treated successfully by anti-tachycardia pacing (ATP) showed a bimodal pattern with even distributions. VTAs treated by ICD shocks showed a bimodal pattern with a predominant afternoon peak. The duration of VTA peaks was increased from 13.5 to 17 h with increasing daylight time from 9.9 to 14.5 h. The weekly VTA distribution showed a significant septadian pattern with lowest frequency on weekend and highest on weekdays (χ2 = 4840, P < 0.0001). No annual periodicity and monthly periodicity were seen. CONCLUSIONS: Sustained VTA events exhibited a circadian rhythm in a large population of military veterans with ICD/CRT-D; specifically, a bimodal pattern with a predominant afternoon peak was observed. Further, the majority of VTA episodes treated by ICD shock occurred in the afternoon, and the duration of VTA peak lengthened with increased duration of daylight time.

Impact of defibrillation threshold testing on burden of heart failure hospitalizations.

Background: Defibrillation threshold testing (DT) following implantable cardioverter defibrillator (ICD) implantation has not shown to improve mortality. However, the impact of DT on burden of heart failure (HF) hospitalisations has not been well defined.Methods: We studied retrospectively consecutive patients who underwent ICD implantation or generator change between 2008 and 2014. Primary outcome was burden of HF hospitalisations within 30 days following implantation. Secondary outcomes were mortality, stroke, and ICD shock within 30 days and one-year mortality.Results: Three hundred and eleven of 501 patients (62%) were in DT+ group versus 190 (38%) were in DT- group. The percentage of new implantations was higher in DT+ group than in DT- group (69% vs 39%, p < .001) but the distributions of NYHA function classes were similar between two groups. The burden of HF hospitalisations at 30-days was significantly higher in DT+ group than in DT- group (17.4% vs 4.7%, HR 0.842, 95% CI 0.774-0.915, p < .0001). No difference in mortality, stroke or ICD shocks was found between two groups at 30 days and mortality at 1 year.Conclusions: DT after new ICD or generator replacement was associated with increased HF hospitalisation rates at 30 days after ICD implant in a non-trial HF population. However, there was no association between DT and mortality, stroke and ICD shocks at 30 days or mortality at 1 year. The increased burden of HF hospitalisation in this observational study requires validation by randomised studies.

Atrial Fibrillation in the Elderly: The Role of Sub-Clinical Isolated Cardiac Amyloidosis.

Amyloid infiltration of the atrium is described in patients with valvular heart disease and is associated with an increased risk for atrial fibrillation(AF) while amyloid deposits in the ventricles is increasingly being diagnosed in patients with HFpEF. The role of amyloid deposits in patients with AF without valvular heart disease, which represents the most common form of AF globally, is undefined. In this study, we sought to assess the prevalence of sub-clinical isolated cardiac amyloidosis (ICA) at autopsy and the odds of AF in these patients. A total of 1083 patients were included in the study and 3.1% of patients were found to have asymptomatic ICA. Patients with ICA were older and had a higher odds of AF independent of age and CHA2DS2VASc score. Amongst patients with AF, those with ICA were more likely to have persistent forms of AF and had a lower sinus rhythm P-wave amplitude. Further studies are required to further define this entity, identify imaging modalities to aid in antemortem diagnosis of ICA and to establish the optimal management strategies in these patients.

Increased baseline ECG R-R dispersion predicts improvement in systolic function after atrial fibrillation ablation.

Background: Atrial fibrillation (AF) is associated with left ventricular (LV) systolic dysfunction which may improve after AF ablation. We hypothesised that increased ventricular irregularity, as measured by R-R dispersion on the baseline ECG, would predict improvement in the left ventricular ejection fraction (LVEF) after AF ablation. Methods: Patients with LVEF <50% at two US centres (2007-2016), having both a preablation and postablation echocardiogram or cardiac MRI, were included. LVEF improvement was defined as absolute increase in LVEF by >7.5%. Multivariable logistic regression (restricted to echocardiographic/ECG variables) was performed to evaluate predictors of LVEF improvement. Results: Fifty-two patients were included in this study. LVEF improved in 30 patients (58%) and was unchanged/worsened in 22 patients (42%). Those with versus without LVEF improvement had an increased baseline R-R dispersion (645±155 ms vs 537±154 ms, p=0.02, respectively). The average baseline heart rate in all patients was 93 beats per minute. After multivariable logistic regression, increased R-R dispersion (OR 1.59, 95% CI 1.00 to 2.55, p=0.03) predicted LVEF improvement. Conclusions: Increased R-R dispersion on ECG was independently associated with improved systolic function after AF ablation. This broadens the existing knowledge of arrhythmia-induced cardiomyopathy, demonstrating that irregular electrical activation (as measured by increased R-R dispersion on ECG) is associated with a cardiomyopathy capable of improving after AF ablation.

An unyielding valve leading to venous spasm during pacemaker implantation: a case report.

BACKGROUND: Subclavian venous spasm is an uncommon complication during permanent pacemaker implantation. The exact aetiology of subclavian venous spasm is not clear but has been suggested to be due to either mechanical irritation of the vein during needle puncture or due to chemical irritation from contrast injection. Here, we report a case of an unyielding subclavian vein valve that impeded guidewire advancement and the repeated guidewire manipulation led to venous spasm. CASE SUMMARY: A 45-year-old woman with a history of surgical repair of Tetrology of Fallot in childhood presented with symptomatic bifascicular block and underwent a permanent pacemaker implantation. A subclavian venogram done prior to the procedure showed a prominent valve in the distal portion of the vein. Following venous puncture, guidewire advancement was impeded by the prominent valve. The resulting guidewire manipulation led to subclavian venous spasm necessitating a medial subclavian venous puncture and access. DISCUSSION: Prolonged mechanical irritation of the vein during pacemaker implantation may lead to venous spasm impeding pacemaker implantation. Early identification of an impeding valve and obtaining access medial to the valve may help prevent this uncommon complication.

Outcomes of Catheter Ablation of Ventricular Tachycardia Based on Etiology in Nonischemic Heart Disease: An International Ventricular Tachycardia Ablation Center Collaborative Study.

OBJECTIVES: This study sought to characterize ventricular tachycardia (VT) ablation outcomes across nonischemic cardiomyopathy (NICM) etiologies and adjust these outcomes by patient-related comorbidities that could explain differences in arrhythmia recurrence rates. BACKGROUND: Outcomes of catheter ablation of VT in patients with NICM could be related to etiology of NICM. METHODS: Data from 2,075 patients with structural heart disease referred for catheter ablation of VT from 12 international centers was retrospectively analyzed. Patient characteristics and outcomes were noted for the 6 most common NICM etiologies. Multivariable Cox proportional hazards modeling was used to adjust for potential confounders. RESULTS: Of 780 NICM patients (57 ± 14 years of age, 18% women, left ventricular ejection fraction 37 ± 13%), underlying prevalence was 66% for dilated idiopathic cardiomyopathy (DICM), 13% for arrhythmogenic right ventricular cardiomyopathy (ARVC), 6% for valvular cardiomyopathy, 6% for myocarditis, 4% for hypertrophic cardiomyopathy, and 3% for sarcoidosis. One-year freedom from VT was 69%, and freedom from VT, heart transplantation, and death was 62%. On unadjusted competing risk analysis, VT ablation in ARVC demonstrated superior VT-free survival (82%) versus DICM (p ≤ 0.01). Valvular cardiomyopathy had the poorest unadjusted VT-free survival, at 47% (p < 0.01). After adjusting for comorbidities, including age, heart failure severity, ejection fraction, prior ablation, and antiarrhythmic medication use, myocarditis, ARVC, and DICM demonstrated similar outcomes, whereas hypertrophic cardiomyopathy, valvular cardiomyopathy, and sarcoidosis had the highest risk of VT recurrence. CONCLUSIONS: Catheter ablation of VT in NICM is effective. Etiology of NICM is a significant predictor of outcomes, with ARVC, myocarditis, and DICM having similar but superior outcomes to hypertrophic cardiomyopathy, valvular cardiomyopathy, and sarcoidosis, after adjusting for potential covariates.

A single center experience on the clinical utility evaluation of an insertable cardiac monitor.

BACKGROUND: The evaluation of insertable cardiac monitor (ICM) has been largely on the device performance and safety with only limited studies on the clinical utility. The aim of this study was to evaluate the clinical utility of ICM in patients with a variety of clinical presentations. METHODS: A single-center retrospective study on the clinical utility, as measured by both expected and unexpected clinical useful ICM findings and the initiation of therapeutic interventions, was conducted. RESULTS: Ninety-five consecutive patients (median age 68 years) received ICM Reveal LINQ™ for clinical indications of unexplained syncope (53), cryptogenic stroke (19), unexplained infrequent palpitations (14) and AF management (9). During a median follow-up of 414 days, the causes for unexplained syncope were arrhythmia-related (11.3%), arrhythmia-unrelated (32%) and undetermined (56.6%). Atrial fibrillation in patients with cryptogenic stroke was detected in 31.6% (6/19). The clinical utility occurrence was 48.4% with the expected and incidental (unexpected) clinical utility of 41% and 7.4% patients respectively. Of these, therapeutic interventions based on ICM diagnoses were initiated in 18.9% (18/95) of patients. CONCLUSIONS: ICM (Reveal LINQ™) offers substantial expected and unexpected clinical utility in patients with a variety of clinical presentations. The causes of nearly one third of patients receiving ICM for unexplained syncope were unrelated to cardiac arrhythmia. Nearly one fifth of patients with newly diagnosed arrhythmia from ICM received therapeutic interventions.