S. Patrick Whalen

Common atrial fibrillation risk alleles at 4q25 predict recurrence after catheter-based atrial fibrillation ablation

BACKGROUND Common single nucleotide polymorphisms at chromosome 4q25 (rs2200733, rs10033464) are associated with both lone and typical atrial fibrillation (AF). Risk alleles at 4q25 have recently been shown to predict recurrence of AF after ablation in a population of predominately lone AF, but lone AF represents only 5%-30% of AF cases. OBJECTIVE To test the hypothesis that 4q25 AF risk alleles can predict response to AF ablation in the majority of AF cases. METHODS Patients enrolled in the Vanderbilt AF Registry underwent 378 catheter-based AF ablations (median age 60 years; 71% men; 89% typical AF) between 2004 and 2011. The primary end point was time to recurrence of any nonsinus atrial tachyarrhythmia (atrial tachycardia, atrial flutter, or AF). RESULTS Two-hundred atrial tachycardia, atrial flutter, or AF recurrences (53%) were observed. In multivariable analysis, the rs2200733 risk allele predicted a 24% shorter recurrence-free time (survival time ratio 0.76; 95% confidence interval [CI] 0.6-0.95; P = .016) compared with wild type. The heterozygous haplotype demonstrated a 21% shorter recurrence-free time (survival time ratio 0.79; 95% CI 0.62-0.99) and the homozygous risk allele carriers a 39% shorter recurrence-free time (survival time ratio 0.61; 95% CI 0.37-1.0; P = .037). CONCLUSIONS Risk alleles at the 4q25 loci predict impaired clinical response to AF ablation in a population of patients with predominately typical AF. Our findings suggest that the rs2200733 polymorphism may hold promise as an objectively measured patient characteristic that can be used as a clinical tool for selecting patients for AF ablation.

Common Genetic Variants and Response to Atrial Fibrillation Ablation

Background—Common single nucleotide polymorphisms (SNPs) at chromosomes 4q25 (rs2200733, rs10033464 near PITX2), 1q21 (rs13376333 in KCNN3), and 16q22 (rs7193343 in ZFHX3) have consistently been associated with the risk of atrial fibrillation (AF). Single-center studies have shown that 4q25 risk alleles predict recurrence of AF after catheter ablation of AF. Here, we performed a meta-analysis to test the hypothesis that these 4 AF susceptibility SNPs modulate response to AF ablation. Methods and Results—Patients underwent de novo AF ablation between 2008 and 2012 at Vanderbilt University, the Heart Center Leipzig, and Massachusetts General Hospital. The primary outcome was 12-month recurrence, defined as an episode of AF, atrial flutter, or atrial tachycardia lasting >30 seconds after a 3-month blanking period. Multivariable analysis of the individual cohorts using a Cox proportional hazards model was performed. Summary statistics from the 3 centers were analyzed using fixed effects meta-analysis. A total of 991 patients were included (Vanderbilt University, 245; Heart Center Leipzig, 659; and Massachusetts General Hospital, 87). The overall single procedure 12-month recurrence rate was 42%. The overall risk allele frequency for these SNPs ranged from 12% to 35%. Using a dominant genetic model, the 4q25 SNP, rs2200733, predicted a 1.4-fold increased risk of recurrence (adjusted hazard ratio,1.3 [95% confidence intervals, 1.1–1.6]; P=0.011). The remaining SNPs, rs10033464 (4q25), rs13376333 (1q21), and rs7193343 (16q22) were not significantly associated with recurrence. Conclusions—Among the 3 genetic loci most strongly associated with AF, the chromosome 4q25 SNP rs2200733 is significantly associated with recurrence of atrial arrhythmias after catheter ablation for AF.

Relation of morbid obesity and female gender to risk of procedural complications in patients undergoing atrial fibrillation ablation.

Obese patients with atrial fibrillation (AF) are frequently treated with AF ablation. We sought to examine whether a body mass index (BMI) threshold exists beyond which the odds of experiencing a complication from AF ablation increases. All patients enrolled in the Vanderbilt AF Registry who underwent catheter-based AF ablation from May 1999 to February 2012 were included. Major complications were recorded. Morbid obesity was defined as a BMI >40 kg/m(2) and examined in multivariable analysis. A total of 35 complications (6.8%) occurred in 512 ablations. Morbidly obese patients experienced a greater rate of complications (6 of 42, 14.3%) than the nonmorbidly obese (29 of 470, 6.2%; p = 0.046). Using a discrete BMI cutoff, the odds of complications increased 3.1-fold in those with morbid obesity (odds ratio [OR] 3.1, 95% confidence interval [CI] 1.1 to 8.4, p = 0.03) and 2.1-fold for female gender (OR 2.1, 95% CI 1.04 to 4.38, p = 0.04). With BMI as a continuous variable, the odds of complications increased by 5% per 1 unit increase in BMI (OR 1.05, 95% CI 1.0 to 1.11, p = 0.05), and the increase for female gender was 2.2-fold (OR 2.2, 95% CI 1.1 to 4.6, p = 0.03). In conclusion, morbid obesity represents a BMI threshold above which the odds of complications with AF ablation increase significantly. The increase in complications appears to be driven primarily by events in women, suggesting that morbidly obese women are a special population when considering AF ablation.

Left Atrial Hypertension After Repeated Catheter Ablations for Atrial Fibrillation

To the Editor: Catheter ablation is an important treatment for recurrent, symptomatic atrial fibrillation (AF). The original procedure targeted focal triggers of AF arising from within the pulmonary veins (PVs). This technique generated minimal left atrial (LA) scar but was complicated by the

Lead Thrombi Associated with Externalized Cables on Riata ICD Leads: A Case Series

St. Jude Riata family ICD leads are subject to an FDA class I recall due to insulation failure, cable extrusions, and a high rate of electrical failures. We present multiple cases of large intravascular thrombus formation adherent to externalized conductor cables on Riata leads. Our observations highlight a previously unknown risk of large or calcified thrombus formation involving externalized conductors. We suggest that these leads should be screened for thrombi prior to potential lead extraction to determine the safest approach. Serial echocardiography may help detect progressive thrombus formation. The role of systemic anticoagulation for prevention or treatment of these thrombi remains unclear.

Efficacy of a Bio-Absorbable Antibacterial Envelope to Prevent Cardiac Implantable Electronic Device Infections in High-Risk Subjects.

Cardiac implantable electronic device (CIED) infections are potentially preventable complications associated with high morbidity, mortality, and cost. A recently developed bio‐absorbable antibacterial envelope (TYRX™‐A) might prevent CIED infections in high‐risk subjects. However, data regarding safety and efficacy have not been published.

Comparative Outcomes of Transvenous Extraction of Sprint Fidelis and Riata Defibrillator Leads: A Single Center Experience

The FDA has issued class I advisories for Medtronic Sprint Fidelis® and St. Jude Medical RiataTM ICD lead families. Transvenous RiataTM ICD lead extraction is typically considered higher risk than Fidelis® extraction, based on longer duration from implant, presence of externalized conductors and lack of silicone backfill in the SVC and RV coils. However, published data comparing procedural outcomes between these leads are limited.

High-Risk Lead Removal by Planned Sequential Transvenous Laser Extraction and Minimally Invasive Right Thoracotomy

Transvenous pacemaker or implantable cardioverter defibrillator (ICD) lead extraction via mechanical or excimer laser sheath is typically safe and effective. Longer duration from implant, presence of large vegetations or thrombi, fractured leads, and prior failed extraction are risk factors predicting higher complication rates or incomplete or failed lead removal. Techniques developed for minimally invasive valve surgery were used in conjunction with laser extraction to refine a “hybrid” technique for lead extraction. We assessed the outcomes of high‐risk lead extraction using this hybrid lead extraction technique.

Adhesive Epicardial Corticosteroids Prevent Postoperative Atrial Fibrillation

Background—Postoperative atrial fibrillation remains a common cause of morbidity. Although epicardial drug delivery can increase efficacy and reduce side effects, it is impractical for postoperative atrial fibrillation because pericardial bleeding/effusion and drainage cause rapid drug elimination. Fibrin glue sprayed on the epicardium is vigorously adherent, allowing an admixed drug to remain in contact with the heart. The purpose of the present study was to evaluate a novel corticosteroid-fibrin glue mixture applied to the atrial epicardium at the time of surgery for prevention of postoperative atrial tachyarrhythmias. Methods and Results—Talc was instilled into the pericardium in 15 dogs to simulate postoperative inflammation. Pacemakers were implanted to monitor arrhythmias. A mixture of triamcinolone and fibrin glue (Tisseel) was sprayed onto the atria of the treatment animals (n=9), whereas control animals (n=6) received Tisseel or nothing. After 1 week, pacemaker interrogation quantified postoperative atrial tachyarrhythmias (atrial rate >200 bpm) burden. Excised hearts underwent histological examination and tensile strength testing. postoperative atrial tachyarrhythmias occurred in 100% of control animals but only 33% of treatment animals (P=0.027). The median time (25th percentile, 75th percentile) in tachycardia was 5.5 hours (2.7, 12.6) per day in the control group, compared with 0 hours (0, 0.2) in the treatment group (P=0.001). Severe inflammation was present in 6 of 6 control animals and 1 of 9 treatment animals (P=0.001). The tensile strength of a healing left atriotomy was not significantly different between groups. Steroid levels at the time the animals were killed were very low (median of 0.22 &mgr;g/dL [0.18, 0.23]). Conclusions—A mixture of triamcinolone and fibrin glue sprayed onto the atria reduced postoperative atrial tachyarrhythmias and reduced inflammatory cell infiltration. There was no change in the tensile strength of a healing atriotomy and plasma steroid levels were low. Clinical trials of this approach are warranted.

Staged versus Simultaneous Thoracoscopic Hybrid Ablation for Persistent Atrial Fibrillation Does Not Affect Time to Recurrence of Atrial Arrhythmia.

Totally thoracoscopic (TT) epicardial ablation combined with endocardial catheter ablation is an emerging treatment for persistent AF. The effects of timing of the TT and endocardial portion on AT/AF recurrence are not known.