Assessing the Risks Associated with MRI in Patients with a Pacemaker or Defibrillator.

BACKGROUND: The presence of a cardiovascular implantable electronic device has long been a contraindication for the performance of magnetic resonance imaging (MRI). We established a prospective registry to determine the risks associated with MRI at a magnetic field strength of 1.5 tesla for patients who had a pacemaker or implantable cardioverter-defibrillator (ICD) that was "non-MRI-conditional" (i.e., not approved by the Food and Drug Administration for MRI scanning). METHODS: Patients in the registry were referred for clinically indicated nonthoracic MRI at a field strength of 1.5 tesla. Devices were interrogated before and after MRI with the use of a standardized protocol and were appropriately reprogrammed before the scanning. The primary end points were death, generator or lead failure, induced arrhythmia, loss of capture, or electrical reset during the scanning. The secondary end points were changes in device settings. RESULTS: MRI was performed in 1000 cases in which patients had a pacemaker and in 500 cases in which patients had an ICD. No deaths, lead failures, losses of capture, or ventricular arrhythmias occurred during MRI. One ICD generator could not be interrogated after MRI and required immediate replacement; the device had not been appropriately programmed per protocol before the MRI. We observed six cases of self-terminating atrial fibrillation or flutter and six cases of partial electrical reset. Changes in lead impedance, pacing threshold, battery voltage, and P-wave and R-wave amplitude exceeded prespecified thresholds in a small number of cases. Repeat MRI was not associated with an increase in adverse events. CONCLUSIONS: In this study, device or lead failure did not occur in any patient with a non-MRI-conditional pacemaker or ICD who underwent clinically indicated nonthoracic MRI at 1.5 tesla, was appropriately screened, and had the device reprogrammed in accordance with the prespecified protocol. (Funded by St. Jude Medical and others; MagnaSafe ClinicalTrials.gov number, NCT00907361 .).

Brugada-type patterns are easily observed in high precordial lead ECGs in collegiate athletes.

BACKGROUND: Displacement of ECG leads can result in unwarranted findings. We assessed the frequency of Brugada-type patterns in athletes when precordial leads were purposely placed upward. METHODS: Four hundred ninety-one collegiate athletes underwent two ECGs: one with standard leads, one with V1 and V2 along the 2nd intercostal space. A positive Brugada-type pattern was defined as ST elevation in V1 or V2 consistent with a Type 1, 2, or 3 pattern in the high-lead ECG. A control group was comprised of 181 outpatients. RESULTS: No Type 1 patterns were seen. In 58 athletes (11.8%), a Brugada-type 2 or 3 pattern was observed. Those with Brugada-type 2 or 3 patterns were more likely male, taller, and heavier. In the control group, 18 (9.9%) had Brugada-type 2 or 3 patterns and were more likely male. CONCLUSIONS: Proper lead positioning is essential to avoid unwarranted diagnosis of a Brugada-type ECG, especially in taller, heavier male athletes.

Challenges and Outcomes of Posterior Wall Isolation for Ablation of Atrial Fibrillation.

BACKGROUND: The left atrial posterior wall (PW) often contains sites required for maintenance of atrial fibrillation (AF). Electrical isolation of the PW is an important feature of all open surgeries for AF. This study assessed the ability of current ablation techniques to achieve PW isolation (PWI) and its effect on recurrent AF. METHODS AND RESULTS: Fifty-seven consecutive patients with persistent or high-burden paroxysmal AF underwent catheter ablation, which was performed using an endocardial-only (30) or a hybrid endocardial-epicardial procedure (27). The catheter ablation lesion set included pulmonary vein antral isolation and a box lesion on the PW (roof and posterior lines). Success in creating the box lesion was assessed as electrical silence of the PW (voltage <0.1 mV) and exit block in the PW with electrical capture. Cox proportional hazards models were used for analysis of AF recurrence. PWI was achieved in 21 patients (36.8%), more often in patients undergoing hybrid ablation than endocardial ablation alone (51.9% versus 23.3%, P=0.05). Twelve patients underwent redo ablation. Five of 12 had a successful procedural PWI, but all had PW reconnection at the redo procedure. Over a median follow-up of 302 days, 56.1% of the patients were free of atrial arrhythmias. No parameter including procedural PWI was a statistically significant predictor of recurrent atrial arrhythmias. CONCLUSIONS: PWI during catheter ablation for AF is difficult to achieve, especially with endocardial ablation alone. Procedural achievement of PWI in this group of patients was not associated with a reduction in recurrent atrial arrhythmias, but reconnection of the PW was common.

Device therapies: new indications and future directions.

Implantable cardioverter-defibrillator (ICDs), cardiac resynchronization (CRT) and combination (CRT-D) therapy have become an integral part of the management of patients with heart failure with reduced ejection fraction (HFrEF). ICDs treat ventricular arrhythmia and CRTs improve left ventricular systolic function by resynchronizing ventricular contraction. Device therapies (ICD, CRT-D), have been shown to reduce all-cause mortality, including sudden cardiac death. Hospitalizations are reduced with CRT and CRT-D therapy. Major device related complications include device infection, inappropriate shocks, lead malfunction and complications related to extraction of devices. Improvements in device design and implantation have included progressive miniaturization and increasing battery life of the device, optimization of response to CRT, and minimizing inappropriate device therapy. Additionally, better definition of the population with the greatest benefit is an area of active research.

Accuracy of patient perception of their prevailing rhythm: a comparative analysis of monitor data and questionnaire responses in patients with atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) guidelines recommend that symptom relief be a primary goal in management. However, patient perception of their prevailing rhythm is often inaccurate, complicating symptom-targeted treatment. OBJECTIVE: The purpose of this study was to evaluate the accuracy of patient perception of their prevailing rhythm and identify factors that predict inaccuracies. METHODS: Demographic and health status data were captured by questionnaires for 458 outpatients with documented AF. AF burden (%) was captured by 1-week continuous heart monitors. Patients estimated the length and frequency of their AF episodes by completing the AF Symptom Severity questionnaire. Patient reports were compared to AF burden, and outliers were identified and broken into 2 groups: patients with AF burden <10% who indicated near-continuous AF (overestimators) and patients with AF burden >90% who estimated little to no AF (underestimators). Multinomial logistic regression was used to identify predictors of inaccuracies (over- or underestimators). RESULTS: By continuous monitor, 15% of patients were found to be over- or underestimators. Persistent AF, female sex, older age, anxiety, and depression were predictive of inaccurate patient perception. Persistent AF, female sex, and older age were predictive of underestimating, while mood disorders (anxiety and depression) were predictive of overestimating. The prevalence of underestimators was nearly twice that of overestimators. CONCLUSION: Sex, age, and mood disorders are among factors that lead to inaccurate patient perception of their prevailing rhythm in patients with AF. Such modulating factors should be considered when evaluating treatment strategies. Consideration should be given to more liberal use of heart monitors in these patient populations to better target therapy.

Effectiveness of atrial fibrillation monitor characteristics to predict severity of symptoms of atrial fibrillation.

The goal of treatment for atrial fibrillation (AF) is often to control symptoms. It remains unclear whether targets for treatment such as AF rate or AF burden are correlated with AF symptom severity. Two hundred eighty-six patients completed a questionnaire of their general health and well-being, including a detailed AF symptom assessment immediately followed by a 7-day continuous monitor. AF characteristics assessed from the monitor included AF burden, AF rate, sinus rhythm rate, frequency and severity of pauses, and premature atrial contraction or premature ventricular contraction burden. Characteristics were analyzed separately for patients with paroxysmal or persistent AF. Symptom severity was assessed using the University of Toronto Atrial Fibrillation Severity Scale. Monitor characteristics were compared with AF symptom severity. The mean age of the cohort was 61.8 years and the majority of subjects were male (65.4%). Co-morbidities included hypertension (64.5%), sleep apnea (38.4%), congestive heart failure (19.6%), and diabetes (16.4%). In those with persistent or paroxysmal AF, there were no significant predictors of AF symptom severity. Specifically, heart rate in AF or sinus rhythm, AF burden, or premature atrial contraction or premature ventricular contraction burden was not predictive of AF symptom severity. After adjusting for potential cofounders (including age, gender, and co-morbidities), these findings persisted. In conclusion, there is no value in using AF monitor characteristics to predict symptoms in patients with AF.

Effect of left ventricular diastolic dysfunction on outcomes of atrial fibrillation ablation.

Left ventricular diastolic dysfunction (LVDD) is an important pathogenic factor for atrial fibrillation (AF). There are few data on the effect of LVDD on recurrence of AF after catheter ablation. A cohort of 124 patients (59.9 ± 11.7 years, 73.9% male, and 55% with paroxysmal AF) with recalcitrant AF and normal left ventricular systolic function (left ventricular ejection fraction ≥50%) undergoing ablation was studied. Each patient underwent transthoracic echocardiography, and LVDD was meticulously graded using rhythm-independent (AF or sinus rhythm) transmitral and tissue Doppler parameters. Patients underwent catheter ablation of AF using a stepwise protocol. All patients were followed up at 3, 6, and 12 months with recurrent AF (>30 seconds) captured by electrocardiography and/or 7-day monitor. Kaplan-Meier survival analysis and Cox proportional hazards model were used. There was no LVDD in 72 patients (58%), whereas 33 (26.6%), 10 (8.1%), and 9 (7.3%) patients had grades 1, 2, and 3 LVDD, respectively. AF recurred in 49 patients (39.5%) with median time to recurrence of 248 days. Patients with higher grade of LVDD were increasingly more likely to have recurrence (37.5% for no LVDD and 30.3%, 60%, and 66.7% for grades 1, 2, and 3 LVDD, respectively). Significant LVDD (grade 2 or 3) was an independent predictor of recurrence (hazard ratio 2.6, p = 0.009) after adjusting for persistent (vs paroxysmal) AF and left atrial volume. In conclusion, patients with more severe LVDD have a higher risk of AF recurrence after catheter ablation. These patients may derive less benefit from ablation or may require a more extensive ablation approach.

Use of a closed loop irrigated catheter in epicardial ablation of ventricular tachycardia.

PURPOSE: Catheter ablation of ventricular tachycardia (VT) often requires a combined epicardial and endocardial approach. An open irrigated catheter for epicardial ablation of ventricular tachycardia is commonly used. However, this can be associated with problems of fluid accumulation in the pericardial space necessitating repeated aspirations and interfering with catheter-tissue contact. A closed loop irrigated catheter can be a viable alternative to overcome these problems. We report our first three cases of epicardial VT ablation using a closed loop irrigated ablation catheter (Chilli II, Boston Scientific). METHODS: Catheter ablation of ventricular tachycardia was performed via epicardial and endocardial approaches using a closed loop irrigated ablation catheter (Chilli II, Boston Scientific) and using 3-D mapping with EnSite/NavX system. Patients were routinely followed up after the catheter ablation procedure in clinic for any recurrence of ventricular arrhythmia. RESULTS: We report our first three cases of epicardial VT ablation using a closed loop irrigated ablation catheter. Power delivery was adequate with mean power of 15.2 ± 2.8, 31.1 ± 3.8, and 25.0 ± 3.3 W, respectively, in the three patients. No impedance rises were noted during the lesion formation. There was no recurrence of VT in any of the patients after 3 months of follow-up. CONCLUSIONS: To our knowledge, we report the first case series of epicardial VT ablation using a closed loop irrigated catheter and the EnSite/NavX mapping system. The advantages of closed irrigation, especially in conjunction with impedance-based anatomical mapping, warrant further study of its efficacy in catheter ablation from the pericardial space.

Relation of atrial fibrillation burden and N-terminal pro-brain natriuretic peptide.

Previous studies have noted a correlation between the presence of atrial fibrillation (AF) and elevated brain natriuretic peptide hormone level, although the exact nature of this association is unclear. Understanding the relation between AF and brain natriuretic peptide may enhance care for this patient population. The aim of this study was to establish the relationship between AF burden and N-terminal pro-brain natriuretic peptide (NT-proBNP) level. One hundred eighty-four patients who presented to the University of North Carolina electrophysiology clinic with AF underwent baseline questionnaires, laboratory testing (including NT-proBNP), echocardiography, and 1-week ambulatory rhythm monitoring. Multivariate linear regression was used to determine the association between AF burden and NT-proBNP level. Increased AF burden was associated with increased NT-proBNP level, and this association remained significant after adjusting for possible confounders. Compared with a 0% AF burden, those with an AF burden of 1% to 25% had a nearly 1.5-fold increase (p = 0.102), those with an AF burden of 26% to 99% had a nearly fourfold increase (p <0.001), and those with an AF burden of 100% had a nearly 4.5-fold increase (p <0.001). In conclusion, AF burden as assessed by continuous 1-week ambulatory rhythm monitoring is directly associated with NT-proBNP level. NT-proBNP may act as a useful surrogate for assessing AF burden.

Lone atrial fibrillation is associated with pectus excavatum.

BACKGROUND: Pectus excavatum is a skeletal abnormality that may have cardiac manifestations. OBJECTIVE: To determine whether pectus excavatum is associated with lone atrial fibrillation (AF). METHODS: The pectus severity index (PSI) is the ratio of the lateral diameter of the chest to the distance between the sternum and the spine on computed tomography scan. A normal PSI is ≤2.5 whereas patients with severe pectus excavatum have a PSI >3.25. We calculated the PSI of 220 consecutive patients with AF who underwent radiofrequency catheter ablation from September 2008 to 2012 and compared this to the PSI of 225 controls without a history of AF undergoing chest computed tomography. RESULTS: Mean PSI was higher in patients with lone AF (2.72 ± 0.07) compared to patients with nonlone AF (2.25 ± 0.03) or controls (2.26 ± 0.03) (P < .001). The likelihood of mild, moderate, or severe pectus excavatum was higher in patients with lone AF compared to patients with nonlone AF and controls (P < .001). Patients with lone AF were more than 5 times as likely to have severe pectus excavatum compared to patients with nonlone AF or controls (P < .001) even after adjustment for potential confounders. CONCLUSIONS: Nearly two-thirds of the patients with lone AF have at least mild pectus excavatum and 17% have severe pectus, which is significantly higher than in patients with nonlone AF or controls. This association suggests a potential genetic or mechanical abnormality may be common to the 2 disorders. Our study may provide insight into the pathogenesis of lone AF.