The impact of supraventricular arrhythmias on the outcomes of guideline-compliant implantable cardioverter defibrillator programming.

INTRODUCTION: Several implantable cardioverter defibrillators (ICD) programming strategies are applied to minimize ICD therapy, especially unnecessary therapies from supraventricular arrhythmias (SVA). However, it remains unknown whether these optimal programming recommendations only benefit those with SVAs or have any detrimental effects from delayed therapy on those without SVAs. This study aims to assess the impact of SVA on the outcomes of ICD programming based on 2015 HRS/EHRA/APHRS/SOLAECE expert consensus statement and 2019 focused update on optimal ICD programming and testing guidelines. METHODS: Consecutive patients who underwent ICD insertion for primary prevention were classified into four groups based on SVA status and ICD programming: (1) guideline-concordant group (GC) with SVA, (2) GC without SVA, (3) nonguideline concordant group (NGC) with SVA, and (4) NGC without SVA. Cox proportional hazard models were analyzed for freedom from ICD therapies, shock, and mortality. RESULTS: Seven hundred and seventy-two patients (median age, 64 years) were enrolled. ICD therapies were the most frequent in NGC with SVA (24.0%), followed by NGC without SVA (19.9%), GC without SVA (11.6%), and GC with SVA (8.1%). Guideline concordant programming was associated with 68% ICD therapy reduction (HR 0.32, p = .007) and 67% ICD shock reduction (HR 0.33, p = .030) in SVA patients and 44% ICD therapy reduction in those without SVA (HR 0.56, p = .030). CONCLUSION: Programming ICDs in primary prevention patients based on current guidelines reduces therapy burden without increasing mortality in both SVA and non-SVA patients. A greater magnitude of reduced ICD therapy was found in those with supraventricular arrhythmias.

Effect of Irrigant Characteristics on Lesion Formation After Radiofrequency Energy Delivery Using Ablation Catheters with Actively Cooled Tips.

BACKGROUND: The delivery of radiofrequency (RF) energy through irrigated ablation catheters may be affected by irrigant osmolarity and by catheter position. We sought to characterize lesion formation characteristics using different irrigants in both open and closed irrigated catheter. METHODS: An ex vivo model consisting of viable bovine myocardium and a submersible load cell was assembled in a circulating saline bath at 37°C. An externally irrigated ablation catheter and a closed irrigated catheter were positioned with 10 g of force in both perpendicular and parallel positions. A series of ablation lesions using different irrigants were delivered using a constant rate of irrigation (30 cc/min) at 50 W. Potential clinical applicability was evaluated in vivo by targeting porcine epicardium with different irrigants during open irrigation ablation and assessing lesion sizes. RESULTS: Ablation in the perpendicular position produced significantly larger lesions for all irrigants, compared to their respective parallel position ablation. For both open and closed irrigated ablation, half normal saline (HNS) ablation created larger lesions than normal saline (NS), and dextrose water (D5W) lesions were significantly larger than both HNS and NS lesions. Steam pops were mostly observed in the perpendicular position, and the rate of steam pops was statistically higher only for open irrigated D5W, but not for HNS, when compared to NS. Both open and closed irrigated ablation with D5W and HNS in the parallel position created larger lesions than parallel NS ablation without causing more steam pops. In an in vivo porcine model, open irrigated ablation with D5W created larger lesions compared to standard NS irrigation. CONCLUSIONS: In ex vivo and in vivo models, decreased osmolarity and charge density increased RF energy delivery to tissue, resulting in larger lesions for both open and closed irrigated ablations. A perpendicular catheter position created larger lesions across all irrigants for both open and closed irrigation ablation. The incidence of steam pops was observed more frequently with high power open irrigated using D5W, especially if the catheter was in a perpendicular position. Further research is required to evaluate any clinical role for using different irrigants with an externally irrigated catheter.

Carbon nanotube facilitation of myocardial ablation with radiofrequency energy.

BACKGROUND: The use of carbon nanotubes (CNTs) in oncology has been proposed for the purpose of sensitizing tumors to radiofrequency (RF) ablation. We hypothesize that myocardial tissue infiltrated with CNTs will improve thermal conductivity of RF heating and lead to altered ablation lesion characteristics. METHODS: An ex vivo model consisting of viable bovine myocardium, a circulating saline bath at 37 °C, a submersible load cell, and a deflectable sheath was assembled. A 4-mm nonirrigated ablation catheter was positioned with 10 gm of force over bovine myocardium infiltrated with CNTs, 0.9% saline, or sham injections. A series of ablation lesions were delivered at 20 and 50 W, and lesion volumes were acquired by analyzing tissue sections with a digital micrometer. Tissue temperature analyses at 3 and 5 mm depths were also performed. RESULTS: Myocardial tissue treated with CNTs resulted in significantly larger lesions at both low and high power settings. The electrical impedance was increased in CNT treated tissue with a greater impedance change observed in the CNT infiltrated myocardium. The thermal conductivity of heat generated by application of RF in the tissue was altered by the presence of CNTs, resulting in higher temperatures at 3 and 5 mm depths for both 20 and 50 W. CONCLUSIONS: Myocardial tissue treated with CNTs resulted in significantly larger lesions at both low and high power settings. The electrical and thermal conductivity of heat generated by application of RF in myocardial tissue was altered by the presence of CNTs. Further research is needed to assess the in vivo applicability for this concept of facilitated ablation with CNTs.

Programming of implantable cardioverter defibrillators for primary prevention: outcomes at centers with high vs. low concordance with guidelines.

BACKGROUND: While ICD therapy reduction programming strategies are recommended in current multi-society guidelines, concerns remain about a possible trade-off between the benefits of ICD therapy reduction and failure to treat episodes of ventricular arrhythmias. The study is to evaluate the outcomes of primary prevention patients followed in centers with high and low concordance with the 2015 HRS/EHRA/APHRS/SOLAECE expert consensus statement and 2019 focused update on optimal ICD programming and testing guidelines. METHODS: Consecutive patients with primary prevention ICD implantation from two centers between 2014 and 2016 were included. One center was classified as high guideline concordance center (HGC) with 47% (146/310) of patients with initial ICD concordant with the guidelines, and the other center was classified as low guideline concordance center (LGC) with only 1% (2/178) of patients with guideline-concordant initial ICD programming. Cox proportional hazard models were used to assess risk of first ICD therapy (ATP or shock), first ICD shock, and mortality. RESULTS: A total of 488 patients were included (mean age, 66 ± 13 years). During a mean follow-up of 1.9 ± 0.9 years, patients followed at HGC were 63% less likely to receive any ICD therapy (adjusted HR [aHR] 0.37, 95% CI 0.42-0.99). There were no significant differences in the rate of first ICD shock (aHR 0.72, 95% CI 0.34-1.52) or mortality (aHR 1.19, 95% CI, 0.47-3.05). CONCLUSIONS: Compared to primary prevention patients followed at LGC, primary prevention ICD patients followed at HGC received a significantly lower rate of ICD therapy, mainly from ATP reduction, without a difference in mortality during follow-up.

Recurrent biventricular takotsubo cardiomyopathy with fatal outcome.

A woman in her 60s presented initially with nausea, vomiting and abdominal pain. She rapidly progressed to respiratory failure requiring intubation. ECG demonstrated no significant ST segment changes. Troponin I and brain natriuretic peptide were elevated. Chest CT angiography demonstrated small non-occlusive segmental pulmonary emboli. Transthoracic echocardiogram findings suggested biventricular takotsubo cardiomyopathy (TCM) with left ventricular ejection fraction of less than 20%. She improved with aggressive management and was discharged on carvedilol, lisinopril, atorvastatin and apixaban. Follow-up echocardiogram revealed complete resolution of the left and right ventricular wall motion abnormalities at 9 weeks. She had symptoms recurrence after 7 months from the initial presentation. Repeated echocardiogram was consistent with biventricular TCM recurrence. Despite aggressive medical therapy, multiorgan failure developed and patient care was later transitioned to palliative care.

Programming implantable cardioverter-defibrillator in primary prevention: Guideline concordance and outcomes.

BACKGROUND: Inappropriate therapy is a common adverse effect in patients with an implantable cardioverter-defibrillator (ICD) that may be prevented by appropriate programming. OBJECTIVE: The purpose of this study was to assess the outcomes of device programming based on a 2015 HRS/EHRA/APHRS/SOLAECE expert consensus statement and a 2019 focused update on optimal ICD programming and testing. METHODS: Consecutive patients who underwent ICD insertion for primary prevention from 2014-2016 at 3 centers were included in the retrospective analysis. Patients were classified into 2 groups based on the tachycardia programming at the time of implant: guideline concordant group (GC) and non-guideline concordant group (NGC). Kaplan-Meier analysis and Cox proportional hazard models were used to estimate freedom from ICD therapy (antitachycardia pacing or shock), ICD shock, and death. RESULTS: A total of 772 patients were included in the study (mean age 63.3 ± 13.8 years). Of this total, 258 patients (33.4%) were in the GC group and 514 patients (66.6%) were in the NGC group. During mean follow-up of 2.02 ± 0.91 years, guideline concordant programming was associated with a 53% reduction in ICD therapy (P <.01) and 50% reduction in ICD shock (P = .02). There were no significant differences in mortality (6% in GC group vs11% in NGC group; P = .22). CONCLUSION: Only one-third of the studied population had an ICD device programmed in concordance with current guidelines. ICD programming based on the current guidelines was associated with a significantly lower rate of ICD therapy and shock without changes in mortality during intermediate-term follow-up.

Transient Left Atrial Appendage Inversion During Transcatheter Closure Device Placement.

A 72-year-old female patient underwent left atrial appendage closure. During recapture of the occlusion device, transient inversion of the appendageal wall occurred. We describe the mechanism with real-time imaging and share our experience of handling this situation. To the best of our knowledge, this is the first case report of this unique recapture complication.

Amiodarone-induced Hyponatremia: A Case Report and a Review of the Literature.

Amiodarone is a widely used medication for controlling various types of cardiac arrhythmias. Nonetheless, it carries several known adverse effects that may preclude its use or necessitate discontinuation. Hyponatremia resulting from amiodarone is rarely reported, and its incidence is unknown. We present a case of severe hyponatremia secondary to amiodarone therapy and a review of the literature.

Noninvasive predictors of perioperative atrial arrhythmias in patients with tetralogy of Fallot undergoing pulmonary valve replacement.

BACKGROUND: Patients with tetralogy of Fallot (TOF) have increased risk of atrial arrhythmias. HYPOTHESIS: A measure of atrial dispersion, the P-wave vector magnitude (Pvm), can identify patients at risk for perioperative atrial flutter (AFL) or intra-atrial re-entrant tachycardia (IART) in a large TOF cohort. METHODS: We performed a blinded, retrospective analysis of 158 TOF patients undergoing pulmonary valve replacement between 1997 and 2015. History of AFL/IART was documented using electrocardiogram, Holter monitor, exercise stress test, implanted cardiac device, and electrophysiology study. P-R intervals, Pvm, QRS duration, and QRS vector magnitude were assessed from resting sinus-rhythm 12-lead electrocardiograms and identification of those with AFL/IART was determined. RESULTS: Fourteen patients (8.9%) were found to have AFL/IART. Pvm, QRS duration, and QRS vector magnitude significantly differentiated those with AFL/IART from those without on univariate analysis: 0.09 ± 0.04 vs 0.18 ± 0.07 mV, 161.3 ± 21.9 vs 137.7 ± 31.4 ms, and 1.2 (interquartile range, 1.0-1.2) vs 1.6 mV (1.0-2.3), respectively (P < 0.05 for each). The Pvm had the highest area under the ROC curve (0.88) and was the only significant predictor on multivariate analysis, with odds ratio of 0.02 (95% confidence interval: 0.01-0.53). P-R duration, MRI volumes, and right-heart hemodynamics did not significantly differentiate those with vs those without AFL/IART. CONCLUSIONS: In TOF patients undergoing pulmonary valve replacement, Pvm has significant value in predicting those with perioperative AFL/IART. These clinical features may help further evaluate TOF patients at risk for perioperative atrial arrhythmias. Prospective studies are warranted.

Noninvasive Predictors of Ventricular Arrhythmias in Patients With Tetralogy of Fallot Undergoing Pulmonary Valve Replacement.

OBJECTIVES: This study sought to test the hypothesis that a vectorcardiographic parameter, the QRS vector magnitude (QRSVm), can risk stratify those patients at risk for sustained spontaneous ventricular arrhythmias (VAs) or ventricular arrhythmia inducibility (VAI) in a large cohort of patients with tetralogy of Fallot (TOF). BACKGROUND: Patients with TOF have an increased risk of VAs, but predicting those at risk can often be challenging. METHODS: Blinded retrospective analyses of 177 TOF patients undergoing pulmonary valve replacement (PVR) between 1997 and 2015 were performed. VAI was evaluated by programmed electrical stimulation in 48 patients. QRS intervals and QRSVm voltage measurements were assessed from resting 12-lead electrocardiograms, and risk of VA was determined. Clinical characteristics, including imaging and cardiac catheterizations, were used for other modality comparisons. RESULTS: Sustained spontaneous VA occurred in 12 patients and inducible VA in 18 patients. Age and QRSVm were significant univariate predictors of VA. QRSVm was the only independent predictor of VAI (p < 0.001). Using a root mean square QRS value of 1.24 mV, the positive and negative predictive values were 47.9% and 97.8%, respectively, for spontaneous sustained VA. For VAI, using a QRSVm cutoff of 1.31 mV, positive and negative predictive values were 63.0% and 95.3%, respectively. CONCLUSIONS: In TOF patients undergoing PVR, older age was associated with increased spontaneous VA risk. Lower QRSVm predicted spontaneous VA or VAI risk with high negative predictive values. QRSVm is the only independent predictor of VAI. These clinical features may help further risk stratify TOF patients requiring therapies to prevent sudden death.

Impact of Alcohol Consumption on Atrial Fibrillation Outcomes Following Pulmonary Vein Isolation.

BACKGROUND: Moderate to heavy alcohol use has been shown to be associated with increased atrial fibrillation (AF) incidence. However, the relationship between alcohol use and AF recurrence after pulmonary vein isolation (PVI) is not well known. OBJECTIVE: We sought to study the impact of different alcohol consumption levels on outcomes after AF ablation. METHODS: A retrospective analysis was performed of 226 consecutive patients undergoing first time PVI for AF. Clinical data were collected including alcohol intake classified into 3 groups: none-rare (< 1 drink/ week), moderate (1-7 drinks/ week), and heavy (> 7 drinks/ week). Patients were followed for recurrences within the first 3 months (blanking period; early recurrence) and after 3 months up to 1 year (late recurrence) after the ablation. RESULTS: Paroxysmal and persistent AF had early recurrence rates of 29.1% and 32.2%, and late recurrence rates of 30.2% and 44.1%, respectively. The none-rare alcohol group had a higher frequency of diabetes mellitus (p=0.007). Neither moderate or heavy alcohol consumption, in reference to the none-rare group, was significantly predictive of early or late AF recurrence on adjusted multivariate logistic regression analysis (p>0.05). CONCLUSION: Despite known associations between alcohol and incidence of AF, alcohol consumption is not associated with early or late AF recurrence after PVI in this cohort.

Enhanced Radiofrequency Ablation With Magnetically Directed Metallic Nanoparticles.

BACKGROUND: Remote heating of metal located near a radiofrequency ablation source has been previously demonstrated. Therefore, ablation of cardiac tissue treated with metallic nanoparticles may improve local radiofrequency heating and lead to larger ablation lesions. We sought to evaluate the effect of magnetic nanoparticles on tissue sensitivity to radiofrequency energy. METHODS AND RESULTS: Ablation was performed using an ablation catheter positioned with 10 g of force over prepared ex vivo specimens. Tissue temperatures were measured and lesion volumes were acquired. An in vivo porcine thigh model was used to study systemically delivered magnetically guided iron oxide (FeO) nanoparticles during radiofrequency application. Magnetic resonance imaging and histological staining of ablated tissue were subsequently performed as a part of ablation lesion analysis. Ablation of ex vivo myocardial tissue treated with metallic nanoparticles resulted in significantly larger lesions with greater impedance changes and evidence of increased thermal conductivity within the tissue. Magnet-guided localization of FeO nanoparticles within porcine thigh preps was demonstrated by magnetic resonance imaging and iron staining. Irrigated ablation in the regions with greater FeO, after FeO infusion and magnetic guidance, created larger lesions without a greater incidence of steam pops. CONCLUSIONS: Metal nanoparticle infiltration resulted in significantly larger ablation lesions with altered electric and thermal conductivity. In vivo magnetic guidance of FeO nanoparticles allowed for facilitated radiofrequency ablation without direct infiltration into the targeted tissue. Further research is needed to assess the clinical applicability of this ablation strategy using metallic nanoparticles for the treatment of cardiac arrhythmias.

Effects of radiofrequency energy delivered through partially insulated metallic catheter tips on myocardial tissue heating and ablation lesion characteristics.

BACKGROUND: Cardiac radiofrequency (RF) ablation is typically achieved using symmetric catheter tips, which may result in unintended heating adjacent to targeted tissue. Partial insulation may alter lesion geometry and prevent collateral heating. OBJECTIVE: The purpose of this study was to assess partially insulated focused ablation (PIFA). METHODS: Partial insulation using thermally conductive materials was applied to a 4-mm or 8-mm nonirrigated catheter and a 3.5-mm open-irrigated catheter. These PIFA tips, or their noninsulated counterparts, were applied to ex vivo viable bovine myocardium. Ablations were delivered at various powers and under temperature control. Potential clinical applicability was evaluated in vivo by targeting porcine epicardium with irrigated PIFA and assessing its protective effects on the pericardium. RESULTS: PIFA catheters exhibited different properties and produced asymmetric lesions compared with corresponding standard ablation catheters. Temperatures at 3- and 5-mm depths were higher for PIFA catheters, with a temperature increase measured at the catheter tip-tissue interface; however, in temperature control ablation, tip-tissue temperature increases did not limit power delivery. Furthermore, temperatures were lower on the insulated surface and were significantly higher on the noninsulated PIFA side. Impedance changes were significantly larger; more steam pops were observed with PIFA but were mitigated by external irrigation, a larger tip electrode, and use of more thermally conductive insulation. In contrast to standard ablation, open-irrigated PIFA created larger asymmetric lesions in vivo over porcine epicardium, without evidence of pericardial injury. CONCLUSION: PIFA ablation has different characteristics compared with symmetrically conductive ablation. Further research is needed to assess the clinical implications of insulated catheter ablation.

Effect of radiofrequency energy delivery in proximity to metallic medical device components.

BACKGROUND: Radiofrequency (RF) ablation of cardiac arrhythmias is often performed in the presence of metallic materials in the heart. OBJECTIVES: We hypothesize that metal objects in proximity to an RF ablation source can lead to ohmic heating of surrounding tissue. Furthermore, we hypothesize that insulation of the metal can mitigate this RF effect. METHODS: A model consisting of viable bovine myocardium or thermochromic liquid crystal medium, a circulating saline bath at 37°C, and a load cell was used. A 4-mm RF ablation catheter was positioned with 10 g of force over bovine myocardium and placed in proximity to a copper wire, a defibrillator lead, and a circular mapping catheter. RF was applied at 30 W, and tissue temperatures were measured. Ablation near insulated and noninsulated esophageal temperature probes was also performed. RESULTS: Ablation in proximity to metal resulted in higher temperatures. Average maximum distances for observed thermal changes to >45°C for the ± lead were 5.2 ± 0.3 mm and 5.7 ± 0.4 mm when metal was interposed between the catheter and the ground electrode. Presence of an esophageal temperature probe increased temperatures in tissues adjacent to the probe and caused lesions remote to the ablation site. Esophageal probe insulation prevented these tissue temperature increases and injury to nontargeted tissues. CONCLUSION: Effects of RF ablation are potentiated near metallic components of medical devices, leading to significant tissue heating. Further research is needed to assess the safety impact of RF in the myocardium near metallic objects, particularly esophageal temperature probes.

Gadolinium Augmentation of Myocardial Tissue Heating During Radiofrequency Ablation.

OBJECTIVES: This study hypothesized that a metal already commonly used in medical procedures, gadolinium (Gd), will augment radiofrequency (RF) thermal injury and affect cardiac ablation lesions. BACKGROUND: Enhancement of RF ablation using metallic particles has been proposed for ablation of tumors. METHODS: A series of ablation lesions were delivered at variable power using an ex vivo model. Tissue temperatures and lesion characteristics were analyzed. Ablation in a porcine in vivo model after direct needle injection of the myocardium with Gd or after systemic administration of Gd encased in heat sensitive liposomes was also performed and compared to control values. RESULTS: Ablation after Gd infiltration of myocardial tissue resulted in significantly larger lesions at both low- and high-power settings. Larger impedance changes were observed during ablation of Gd-treated myocardium. In vivo ablation using a force-sensing irrigated tip catheter resulted in enhanced lesion sizes after Gd injection without a higher incidence of steam pops or perforation. Systemic administration of liposomal Gd with local release by RF heating did not result in larger ablation sizes. CONCLUSIONS: Gd can be used to enhance RF ablation lesions. In both ex vivo studies with a 4-mm ablation catheter under power control and in vivo findings with an irrigated tip catheter, ablation of myocardium infiltrated with Gd resulted in larger lesions, with altered RF electrical and thermal characteristics. More research is needed to refine the potential for Gd facilitation of RF ablation. The use of systemic heat-sensitive liposomes containing Gd with targeted release by RF heating did not affect lesion size.