Areas with complex fractionated atrial electrograms recorded after pulmonary vein isolation represent normal voltage and conduction velocity in sinus rhythm.

AIMS: Although complex fractionated atrial electrograms (CFAEs) are purported to represent critical sites for atrial fibrillation (AF) perpetuation, the mechanism and the significance of CFAE in the genesis of AF remain poorly understood. This study evaluated the relationship between CFAE and areas of abnormal atrial tissue defined by low-voltage electrograms (LVE) and signal average of the P-wave (SAPW). METHODS AND RESULTS: Complex fractionated atrial electrogram maps were obtained after pulmonary vein isolation in 15 patients with persistent AF. Patients were then cardioverted and voltage/activation maps were acquired in normal sinus rhythm (NSR). Total left atrium (LA), CFAE and LVE areas were measured as % of total LA area (mean ± SD). Conduction velocities of normal, LVE and CFAE areas were also measured during NSR. Patients underwent signal averaged ECG of the P-wave in NSR within 24 h of the procedure. Complex fractionated atrial electrograms areas accounted for 33 ± 24% of total LA. In NSR, only 12 ± 10% of LA area had LVE. There was no anatomic correlation between CFAE sites and LVE; the area of overlap between CFAE and LVE was only 1.6 ± 1.5%. Conduction velocity was faster in CFAE areas (2.3 ± 1.4 m/s) than in normal voltage areas (1.3 ± 0.3 m/s), and LVE areas (1.1 ± 0.7 m/s, P = 0.06). A positive correlation was only found between LVE areas and SAPW duration (r = 0.7, P = 0.04). CONCLUSION: Areas of CFAEs correspond to areas of normal atrial voltage and normal conduction velocity during NSR. Complex fractionated atrial electrogram probably represents the response of normal healthy atrial tissue to rapid pulmonary vein activation.

Mechanical esophageal displacement during catheter ablation for atrial fibrillation.

OBJECTIVE: To determine the feasibility and safety of esophageal displacement during atrial fibrillation (AF) ablation, to prevent thermal injury. BACKGROUND: Patients undergoing AF ablation are at risk of esophageal thermal injury, which ranges from superficial ulceration, to gastroparesis, to the rare but catastrophic atrioesophageal fistula. A common approach to avoid damage is luminal esophageal temperature (LET) monitoring; however, (1) temperature rises mandate interruptions in energy delivery that interrupt workflow and potentially decrease procedural efficacy, and (2) esophageal fistulas have been reported even with LET monitoring. METHODS: A cohort of 20 consecutive patients undergoing radiofrequency (RF) (16 patients) or laser balloon (4 patients) ablation of AF under general anesthesia. After barium instillation, the esophagus was deviated using an endotracheal stylet placed within a thoracic chest tube. LET monitoring was used during catheter ablation. Upper GI endoscopy was performed prior to discharge. RESULTS: At the pulmonary vein level, leftward deviation measured 2.8 ± 1.6 cm (range: 0.4-5.7) and rightward deviation 2.8 ± 1.8 cm (range: 0.5-4.9). The temperature rose to >38.5 °C in 3/20 (15%) patients. In these 3 patients, there was an average of 2 applications/patient that recorded temperatures >38.5 °C. No patient had a temperature rise > 40 °C. Endoscopy revealed no esophageal ulceration from thermal injury in 18/19 (95%) patients; the sole patient with a thermally mediated ulceration had an unusual esophageal diverticulum fully across the posterior left atrium. Twelve patients (63%) exhibited trauma related to instrumentation with no clinical sequelae. CONCLUSIONS: Mechanical esophageal deviation is feasible and allows for uninterrupted energy delivery along the posterior wall during catheter ablation of AF.

Activation and entrainment mapping of hemodynamically unstable ventricular tachycardia using a percutaneous left ventricular assist device.

OBJECTIVES: Our goal was to investigate the effects of percutaneous left ventricular assist device (pLVAD) support during catheter ablation of unstable ventricular tachycardia (VT). BACKGROUND: Mechanical cardiac support during ablation of unstable VT is being increasingly used, but there is little available information on the potential hemodynamic benefits. METHODS: Twenty-three consecutive procedures in 22 patients (ischemic, n = 11) with structural heart disease and hemodynamically unstable VT were performed with either pLVAD support (n = 10) or no pLVAD support (intra-aortic balloon pump counterpulsation, n = 6; no support, n = 7). Procedural monitoring included vital signs, left atrial pressure, arterial blood pressure, cerebral perfusion/oximetry, VT characteristics, and ablation outcomes. RESULTS: The pLVAD group was maintained in VT significantly longer than the non-pLVAD group (66.7 min vs. 27.5 min; p = 0.03) and required fewer early terminations of sustained VT for hemodynamic instability (1.0 vs. 4.0; p = 0.001). More patients in the pLVAD group had at least 1 VT termination during ablation than non-pLVAD patients (9 of 10 [90%] vs. 5 of 13 [38%]; p = 0.03). There were no differences between groups in duration of cerebral deoxygenation, hypotension or perioperative changes in left atrial pressure, brain natriuretic peptide levels, lactic acid, or renal function. CONCLUSIONS: In patients with scar-related VT undergoing catheter ablation, pLVAD support was able to safely maintain end-organ perfusion despite extended periods of hemodynamically unstable VT. Randomized studies are necessary to determine whether this enhanced ability to perform entrainment and activation mapping will translate into a higher rate of clinical success.

The electrical substrate of vagal atrial fibrillation as assessed by the signal-averaged electrocardiogram of the P wave.

BACKGROUND: The autonomic nervous system is thought to be involved in the initiation of atrial fibrillation (AF). However, there is a distinct entity of vagal AF characterized by episodes occurring at rest, postprandially, or during sleep. The purpose of this study was to compare intraatrial conduction in patients with vagally mediated AF to those with nonvagal AF, using the signal-averaged electrocardiogram (SAECG) of P wave. METHODS: SAECG of P wave was performed in 58 patients with AF using the Marquette Medical System, and the mean filtered P-wave duration (SAPW) was measured. Nine patients were categorized as having pure vagal AF (Group I), and 42 patients as having nonvagal AF (Group II); the remaining seven patients were excluded from analysis because of incomplete data. RESULTS: The patients in Group I were significantly younger and more likely to have paroxysmal lone AF, as compared to those in Group II. There was no significant difference in left atrial size and left ventricular function in the two groups. The mean SAPW was significantly shorter in Group I when compared to Group II (118 +/- 5 ms vs 149 +/- 39 ms, P < 0.001). Whereas all patients in Group I had a normal SAPW, 79% of patients in Group II had an abnormal SAPW (P < 0.001). A normal SAPW was significantly predictive of vagal AF independent of other co-variables. CONCLUSIONS: (1) Patients with vagal AF are younger, and invariably have paroxysmal lone AF. (2) SAPW is normal and significantly shorter in vagal AF when compared to patients with nonvagal AF. (3) This suggests that those in the vagal AF population have normal intraatrial conduction, which has implications for AF ablation in these patients.

Laser lead extraction and baffle stenting to facilitate dual chamber implantable defibrillator upgrade in a patient with L-transposition of the great arteries status-post Senning/Rastelli repair: a case report and review of literature.

A case of successful laser extraction of a defibrillator lead with baffle stenting in a 15-year-old boy with dextrocardia, L-transposition, ventricular septal defect, and pulmonic stenosis status-post Senning/Rastelli repair is presented. Six-month follow-up revealed a significant increase in exercise tolerance and maximum oxygen consumption (VO(2)max).

Risk stratification of sudden cardiac death in hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is the most common hereditary cardiac condition and the leading cause of sudden cardiac death (SCD) in young adults. Given that SCD can be the first and most devastating clinical expression of HCM, identifying individuals at high risk is paramount. Determining an individual's risk for HCM-related SCD requires a thorough understanding of the recognized risk factors, of which there are seven established or 'major' and five 'possible'. Major risk factors can be identified by thoroughly reviewing a patient's personal medical history and noninvasive cardiovascular testing. The presence of major risk factors identify patients who are at high enough risk of SCD to warrant consideration of an implantable cardioverter-defibrillator; whereas the absence of any major risk factors provides considerable reassurance to both patient and physician. The risk of HCM-related SCD in patients with no major risk factors is, however, not zero. Possible risk factors gain importance in the presence of an isolated major risk factor. Here, we provide a contemporary review of established and possible risk factors for HCM-related SCD. We also examine microvolt T-wave alternans and cardiovascular MRI as emerging risk stratification tools that could further hone our ability to accurately identify the high-risk patient.

Reverse electrical remodeling of the atria post cardioversion in patients who remain in sinus rhythm assessed by signal averaging of the P-wave.

OBJECTIVES: This study was designed to determine whether the signal-averaged electrocardiogram of the P-wave (SAPW) is an independent predictor of recurrence of atrial fibrillation (AF) post cardioversion (CV), and to assess atrial remodeling using SAPW. BACKGROUND: There are limited electrophysiologic data to predict the recurrence of AF post-CV. The electrical remodeling that occurs post-CV is poorly understood. METHODS: Sixty-four patients with persistent AF undergoing CV were prospectively enrolled. SAPW parameters were measured the day of CV and repeated at 1 month. These SAPW parameters were compared to other baseline indices for the recurrence of AF. RESULTS: Sixty patients (94%) had successful CV. At 1 month, 22 (37%) maintained sinus rhythm (SR). The SAPW total duration decreased significantly in those who remained in SR (159 ms +/- 19 to 146 ms +/- 17; P < 0.0001). Only the duration of AF (46 +/- 50 days vs 147 +/- 227 days, P = 0.03) and the presence of left ventricular hypertrophy (LVH, 12% vs 65%, P = 0.0006) were significantly associated with recurrence of AF. Atrial size strongly correlated with the SAPW duration in patients who remained in SR (R(2)= 0.67, P = 0.003) but not in those who returned to AF (R(2)= 0.11, P = 0.65). CONCLUSIONS: Atrial electrical reverse remodeling occurs in patients with AF who maintain SR post-CV. This remodeling is likely inversely related to the duration of AF and LVH. SAPW duration does not predict recurrence of AF post-CV.

Evaluation and management of patients after implantable cardioverter-defibrillator shock.

CONTEXT: There has been a tremendous increase in the use of implantable cardioverter-defibrillators (ICDs) after several large clinical trials demonstrated their ability to effectively reduce mortality in selected populations of patients with cardiac disease. Thus, the nonelectrophysiologist will often encounter patients who have received an ICD shock. OBJECTIVE: To assess options for the evaluation and management of patients who have received an ICD shock. EVIDENCE ACQUISITION: Literature search using the PubMed and MEDLINE databases to identify articles published from January 1990 to September 2006, using the Medical Subject Headings defibrillators, implantable; defibrillators, implantable/adverse effects; anti-arrhythmic agents; electric countershock; quality of life; tachycardia therapy; algorithm; ventricular tachycardia/diagnosis; and supraventricular tachycardia/diagnosis. Case reports were excluded and articles were limited to those published in English. Scientific statements and guidelines from the American College of Cardiology, the American Heart Association, and the Heart Rhythm Society were also reviewed, as were the reference lists of retrieved articles, to identify any additional articles for inclusion. EVIDENCE SYNTHESIS: There are multiple causes of both appropriate and inappropriate ICD shocks. Irrespective of appropriateness, receiving ICD shocks substantially impairs a patient's quality of life. A variety of techniques are available using ICD programming to reliably limit the occurrence of appropriate or inappropriate ICD shocks. Antiarrhythmic medications can also effectively reduce the occurrence of shocks. CONCLUSIONS: Through the use of effective ICD programming and antiarrhythmic medications, the occurrence of ICD shocks can be reduced while maintaining the lifesaving ability of the ICD. A basic understanding of the range of available options is fundamental for evaluation and management of the patient who has received an ICD shock.

Risk stratification of individuals with the Brugada electrocardiogram: a meta-analysis.

OBJECTIVES: We performed a meta-analysis of prognostic studies of patients with a Brugada ECG to assess predictors of events. BACKGROUND: The Brugada syndrome is an increasingly recognized cause of idiopathic ventricular fibrillation; however, there is wide variation in the prognosis of patients with the Brugada ECG. METHODS AND RESULTS: We retrieved 30 prospective studies of patients with the Brugada ECG, accumulating data on 1,545 patients. Summary estimates of the relative risk (RR) of events (sudden cardiac death [SCD], syncope, or internal defibrillator shock) for a variety of potential predictors were made using a random-effects model. The overall event rate at an average of 32 months follow-up was 10.0% (95% CI 8.5%, 11.5%). The RR of an event was increased (P < 0.001) among patients with a history of syncope or SCD (RR 3.24 [95% CI 2.13, 4.93]), men compared with women (RR 3.47 [95% CI 1.58, 7.63]), and patients with a spontaneous compared with sodium-channel blocker induced Type I Brugada ECG (RR 4.65 [95% CI 2.25, 9.58]). The RR of events was not significantly increased in patients with a family history of SCD (P = 0.97) or a mutation of the SCN5A gene (P = 0.18). The RR of events was also not significantly increased in patients inducible compared with noninducible by electrophysiologic study (EPS) (RR 1.88 [95% CI 0.62, 5.73], P = 0.27); however, there was significant heterogeneity of the studies included. CONCLUSIONS: Our findings suggest that a history of syncope or SCD, the presence of a spontaneous Type I Brugada ECG, and male gender predict a more malignant natural history. Our findings do not support the use of a family history of SCD, the presence of an SCN5A gene mutation, or EPS to guide the management of patients with a Brugada ECG.

Usefulness of programmed ventricular stimulation in predicting future arrhythmic events in patients with cardiac sarcoidosis.

The utility of programmed ventricular stimulation to predict future arrhythmic events in patients with cardiac sarcoidosis is unknown. Similarly, the long-term benefit of implantable cardioverter-defibrillators (ICDs) in cardiac sarcoidosis has not been established. Thirty-two consecutive patients with cardiac sarcoidosis underwent programmed ventricular stimulation. Patients with spontaneous or inducible sustained ventricular arrhythmias (n = 12) underwent ICD insertion. All study patients were followed for the combined arrhythmic event end point of appropriate ICD therapies or sudden death. Mean length of follow-up to sustained ventricular arrhythmia or sudden death was 32 +/- 30 months. Five of 6 patients (83%) with spontaneous sustained ventricular arrhythmias and 4 of 6 patients (67%) without spontaneous but with inducible sustained ventricular arrhythmias received appropriate ICD therapy. Two of 20 patients (10%) with neither spontaneous nor inducible sustained ventricular arrhythmias experienced sustained ventricular arrhythmias or sudden death. Programmed ventricular stimulation predicted subsequent arrhythmic events in the entire population (relative hazard 4.47, 95% confidence interval [CI] 1.30 to 15.39) and in patients who presented without spontaneous sustained ventricular arrhythmias (relative hazard 6.97, 95% CI 1.27 to 38.27). No patient with an ICD died of a primary arrhythmic event. In patients with spontaneous or inducible sustained ventricular arrhythmias, mean survival from first appropriate ICD therapy to death or cardiac transplant was 60 +/- 46 months, with only 2 patients dying or reaching transplant at study end. In conclusion, programmed ventricular stimulation identifies patients with cardiac sarcoidosis at high risk for future arrhythmic events. ICDs effectively terminate life-threatening arrhythmias in high-risk patients, with significant survival after first appropriate therapy.

Mechanism and therapy of cardiac arrhythmias in adults with congenital heart disease.

Over the past few decades, surgical advances have helped to prolong the lives of many young patients with congenital heart disease (CHD). However, as these patients reach adulthood, they are at risk for many late sequelae of their disease or of their corrective surgery. One of the unique challenges associated with CHD is the high incidence of cardiac arrhythmias that arise from the myocardial substrate created by abnormal pressure/volume changes, septal patches, and suture lines. Medical therapy has proven to be disappointing in treating a majority of these cases. Nonetheless, radiofrequency catheter ablation (RFA), an effective tool in treating atrial and ventricular arrhythmias in structurally normal hearts, has been used to treat arrhythmias in adults with congenital heart disease. This review will discuss some of the common congenital heart diseases in adults and the arrhythmias associated with them, as well as the therapeutic modalities used to treat them. Finally, it will present Mount Sinai Hospital's experience in using RFA for the management of cardiac arrhythmias in adults with congenital heart disease.

Microvolt T-wave alternans for the risk stratification of ventricular tachyarrhythmic events: a meta-analysis.

OBJECTIVES: The objective of this study was to perform a meta-analysis of the predictive value of microvolt T-wave alternans (MTWA) testing for arrhythmic events in a wide variety of populations. BACKGROUND: Previous studies describing the use of MTWA as a predictor of ventricular tachyarrhythmic events have been limited by small sample sizes and disparate populations. METHODS: Prospective studies of the predictive value of exercise-induced MTWA published between January 1990 and December 2004 were retrieved. Data from each article were abstracted independently by two authors using a standardized protocol. Summary estimates of the predictive value of MTWA were made using a random-effects model. RESULTS: Data were accumulated from 19 studies (2,608 subjects) across a wide range of populations. Overall, the positive predictive value of MTWA for arrhythmic events was 19.3% at an average of 21 months' follow-up (95% confidence interval [CI] 17.7% to 21.0%), the negative predictive value was 97.2% (95% CI 96.5% to 97.9%), and the univariate relative risk of an arrhythmic event was 3.77 (95% CI 2.39 to 5.95). There was no difference in predictive value between ischemic and nonischemic heart failure subgroups. The positive predictive value varied depending on the population of patients studied (p < 0.0001). CONCLUSIONS: Microvolt T-wave alternans testing has significant value for the prediction of ventricular tachyarrhythmic events; however, there are significant limitations to its use. The predictive value of MTWA varies significantly depending on the population studied. Careful standardization is needed for what constitutes abnormal MTWA. The incremental prognostic value of MTWA when used with other methods of risk stratification is unclear.

Electrophysiologic interventions in patients with inferior vena cava filters: safety and efficacy of the transfemoral approach.

OBJECTIVES: The purpose of this study was to evaluate the transfemoral venous approach for electrophysiologic interventions in patients with inferior vena cava filters. BACKGROUND: Reports have detailed complications associated with obtaining central venous access in patients with inferior vena cava filters. Accordingly, electrophysiologic interventions have been modified or deferred altogether in such patients. METHODS: Patients requiring interventions with a transfemoral approach who were at least 3 months post filter insertion underwent fluoroscopically guided insertion and withdrawal of electrode catheters with appropriate follow-up. RESULTS: Five patients underwent successful pacing, electrophysiologic study, or radiofrequency ablation using one to three catheters, with no complications attributable to filter placement. CONCLUSIONS: Transfemoral electrophysiologic interventions can be safely undertaken across vena cava filters provided appropriate precautions are taken.

Prevention of sudden cardiac death: the role of the implantable cardioverter-defibrillator.

Sudden cardiac death, usually due to fatal ventricular tachyarrhythmias, results in the loss of 300,000-400,000 lives each year in the United States. Implantable cardioverter-defibrillator therapy has revolutionized both the secondary and, increasingly, the primary prevention of sudden cardiac death. In the last decade, subcutaneous pectoral implantation with transvenous lead placement has lessened perioperative risk considerably, raising the benefit/risk ratio for many candidates. As a consequence, the list of approved indications for implantable cardioverter-defibrillator therapy has expanded rapidly in recent years. Current devices offer tiered therapy utilizing bradycardia pacing, anti-tachycardia pacing, low-energy cardioversion, and high-energy defibrillation. Hybrid therapy, combining device, drugs and radiofrequency catheter ablation as required, has become the standard of care for reducing both appropriate and inappropriate shocks. As implantation rates continue to rise, so will the number of patients presenting with electrical storm. The dilemma of how our society will cope with the enormous projected costs of implantable cardioverter-defibrillator therapy has yet to be resolved.