Use of microelectrode near-field signals to determine catheter contact.

BACKGROUND: The utility of standard distal bipolar electrograms (sEGMs) for assessing catheter-tissue contact may be obscured by the presence of far-field signals. Microelectrode electrograms (mEGMs) may overcome this limitation. METHODS: We compared 5 mEGM characteristics (amplitude, frequency content, temporal signal variability, presence of injury current, and amplitude differential between bipoles) with the sEGM for determining tissue contact in 20 patients undergoing ablation of typical atrial flutter. Visualization of catheter-tissue contact by intracardiac echocardiography (ICE) served as the gold standard for assessing contact. Correlation between electrograms and ICE-verified contact level was reported as percent concordance. RESULTS: Three of 5 mEGM characteristics demonstrated significantly better concordance with ICE-verified contact level than the sEGM (52% concordance with ICE): mEGM frequency content (59% concordance with ICE, P < .001 for comparison with sEGM); mEGM amplitude (concordance 59%, P < .001); and mEGM presence of injury current (56% concordance, P = .001). Concordance of amplitude differential between mEGM bipoles with ICE (49%) was not significantly different than the sEGM (P = .638) whereas mEGM temporal variability (39%) was significantly worse than the sEGM. Using a median of all 5 mEGM characteristics provided additive information (concordance with ICE 64%) and was significantly better than all of the individual mEGM characteristics except frequency content (P = .976). CONCLUSION: Microelectrode EGMs (in particular frequency content, amplitude, and presence of injury current) can improve real-time assessment of catheter contact compared to the use of standard bipolar EGMs. Broader use of mEGMs may enhance ablation efficacy.

Clinical and anatomic predictors of need for repeat atrial fibrillation ablation.

AIM: To identify predictors of need for repeat procedures after initial atrial fibrillation (AF) ablation. METHODS: We identified a cohort undergoing first time AF ablation at our institution from January 2004 to February 2014 who had cardiac magnetic resonance (CMR) imaging performed prior to ablation. Clinical variables and anatomic characteristics (determined from CMR) were assessed as predictors of need for repeat ablation. The decision regarding need for and timing of repeat ablation was at the discretion of the treating physician. RESULTS: From a cohort of 331 patients, 142 patients (43%) underwent repeat ablation at a mean of 13.6 ± 18.4 mo after the index procedure. Both male gender (81% vs 71%, P = 0.05) and lower ejection fraction (57.4% ± 10.3% vs 59.8% ± 9.4%, P = 0.04) were associated with need for repeat ablation. On pre-ablation CMR, mean pulmonary vein (PV) diameters were significantly larger in all four PVs among patients requiring repeat procedures. In multivariate analysis, increased right superior PV diameter significantly predicted need for repeat ablation (odds ratio 1.08 per millimeter increase in diameter, 95%CI: 1.00-1.16, P = 0.05). There were also trends toward significance for increased left and right inferior PV sizes among those requiring repeat procedures. CONCLUSION: Increased PV size predicts the need for repeat AF ablation, with each millimeter increase in PV diameter associated with an approximately 5%-10% increased risk of requiring repeat procedures.

Pulmonary Vein Remodeling Following Atrial Fibrillation Ablation: Implications For The Radiographic Diagnosis Of Pulmonary Vein Stenosis.

Background: Pulmonary vein (PV) reverse remodeling has been recognized following atrial fibrillation (AF) ablation. However, the extent of physiologic reverse remodeling after AF ablation and the potential impact of reverse remodeling on the radiographic diagnosis of PV stenosis have not been well characterized. Methods: From January 2004 to February 2014, 186 patients underwent paired cardiac magnetic resonance imaging (MRI) to delineate PV orifice dimensions before and after (mean 109 ± 61 days) an initial AF ablation. Results: Negative remodeling of the PV orifice cross sectional area occurred in 67.8% of veins with a mean reduction in area of 21.0 ± 14.1%, and positive remodeling was seen in the remaining PVs with an increase in area of 22.1 ± 23.4% compared to baseline. No PVs demonstrated a reduction in cross-sectional area of > 75% (maximum reduction observed was 58%). Negative remodeling of the PV long axis dimension was observed in 55.2% of veins with a mean reduction of 14.6 ± 9.2% compared to pre-ablation and positive remodeling was observed in 25.3% of PVs with a mean increase in diameter of 14.7 ± 12.6%. Only 1 PV demonstrated a reduction in orifice diameter of > 50%. There were no clinically evident or suspected cases of PV stenosis in this cohort. Conclusions: Negative remodeling of the PV orifice area was noted in the majority of PVs following AF ablation. However, in almost all cases, the extent of negative remodeling was well below commonly used thresholds for the radiographic diagnosis of PV stenosis.

Pulmonary vein anatomy assessed by cardiac magnetic resonance imaging in patients undergoing initial atrial fibrillation ablation: implications for novel ablation technologies.

BACKGROUND: Novel atrial fibrillation (AF) ablation tools have been designed to facilitate "single-shot" pulmonary vein (PV) isolation using multi-electrode or balloon-based catheters. However, in contrast to point-by-point radiofrequency ablation, these tools may be more dependent on suitable PV anatomy to achieve circumferential PV isolation. METHODS: Three hundred and twenty-two patients underwent gadolinium-enhanced cardiac magnetic resonance angiography to delineate PV anatomy prior to initial AF ablation. Long (a) and short (b) axis measurements of the PV orifice were used to calculate the eccentricity index of the PV ostium. RESULTS: Long axis dimensions of the left superior PV were 18.2 ± 3.3 mm, left inferior PV 17.7 ± 3.9 mm, right superior PV (RSPV) 20.4 ± 4.3, and right inferior PV 18.7 ± 4.7 mm. The long axis dimension of the RSPV was significantly larger than other PVs (p < 0.001). Forty-two patients (13 %) had at least one PV with a long axis dimension >25 mm and 16 patients (5 %) had at least one PV with a long axis dimension >28 mm. Left-sided PV ostia were significantly more ellipse-shaped than the right-sided PVs, which tended to be more spherical. A significant positive correlation was noted between increasing PV size and increased orifice eccentricity. CONCLUSIONS: In this large cohort undergoing initial AF ablation, over 10 % of patients had at least one standard PV with a dimension >25 mm. Additionally, significant differences were noted between left- and right-sided veins with regard to orifice eccentricity. These findings have implications for the design of AF ablation tools and may account for differential isolation rates between PVs noted in some recent studies of novel ablation technologies.

Predictors of Long-Term Survival Following Transvenous Extraction of Defibrillator Leads.

BACKGROUND: Little data exist on long-term outcomes following extraction of implantable cardioverter defibrillator (ICD) leads, particularly for noninfectious indications. We sought to identify predictors of long-term survival after ICD lead extraction. METHODS: We retrospectively reviewed ICD lead extractions at our institution (n = 508). Procedural outcomes and long-term survival were ascertained by medical records review. RESULTS: Indication for lead extraction was infection in 32.5% and lead failure in 61.8%. Mean dwell time of the oldest extracted lead was 5.1 ± 5.9 years. Complete procedural success was achieved in 96.5% of cases. Major procedure-related complications occurred in 1.6% with six periprocedural deaths. During a mean follow-up of 866 ± 798 days, survival was significantly worse among patients with infection as the indication for extraction. At 1 year after extraction, survival among those with infection was 88.2%, compared to 95.0% in the lead failure cohort (P < 0.001). Procedural failure was a significant predictor of long-term mortality, even after excluding periprocedural deaths. In multivariate models, the presence of chronic kidney disease, increased number of leads requiring extraction, lower ejection fraction, and procedural failure were predictors of mortality. CONCLUSION: Despite high rates of procedural success, infectious indication for ICD lead extraction is associated with increased long-term mortality. In contrast, among patients undergoing extraction for lead failure, long-term survival was excellent. The presence of procedural failure was a significant predictor of long-term mortality. Further studies will be necessary to better understand the mechanisms by which procedural failure may adversely impact long-term outcomes.

Pulse Generator Exchange Does Not Accelerate the Rate of Electrical Failure in a Recalled Small Caliber ICD Lead.

BACKGROUND: St. Jude Riata/Riata ST defibrillator leads (St. Jude Medical, Sylmar, CA, USA) were recalled by the Food and Drug Administration in 2011 for an increased rate of failure. More than 227,000 leads were implanted and at least 79,000 patients still have active Riata leads. Studies have examined clinical predictors of lead failure in Riata leads, but none have addressed the effect of implantable cardioverter defibrillator (ICD) generator exchange on lead failure. The purpose of this study is to assess the effect of ICD generator exchange on the rate of electrical failure in the Riata lead at 1 year. METHODS: A retrospective chart review was conducted in patients who underwent implantation of a Riata/Riata ST lead at one center. Patients with a functioning Riata lead (with/without externalized conductor) at the time of ICD exchange were compared to controls with Riata leads implanted for a comparable amount of time who did not undergo generator replacement. RESULTS: Riata leads were implanted in 1,042 patients prior to the recall and 153 of these patients underwent generator exchange without lead replacement. Conductor externalization was noted in 21.5% of Riata leads in the ICD exchange cohort, which was not different from the control group (19.2%; P = 0.32). Two leads failed in the first year after generator replacement (1.5%) which did not significantly differ from the control group (2.0%; P = 0.57). At change-out, 54% received a commanded shock (18.6 ± 0.9 J) that did not result in any change in the high-voltage lead impedance (46.1 ± 1.1 ohms). CONCLUSIONS: Conductor externalization was seen frequently in our cohort of patients. ICD generator exchange did not accelerate the rate of Riata lead failure at 1 year. Although both the control and the change-out cohorts failed at a rate much greater than nonrecalled leads, generator exchange did not appear to add to the problem.