Impact of Voltage Mapping to Guide Whether to Perform Ablation of the Posterior Wall in Patients With Persistent Atrial Fibrillation.

BACKGROUND: Fibrosis as a substrate for atrial fibrillation (AF) has been shown in numerous preclinical models. Voltage mapping enables in vivo assessment of scar in the left atrium (LA), which can be targeted with catheter ablation. OBJECTIVE: We hypothesized that using the presence or absence of low voltage to guide ablation beyond pulmonary vein antral isolation (PVAI) will improve atrial arrhythmia (AF/AT)-free survival in persistent AF. METHODS AND RESULTS: Single-center retrospective analysis of 2 AF ablation strategies: (1) standard ablation (SA) versus (2) voltage-guided ablation (VGA). PVAI was performed in both groups. With SA, additional lesions beyond PVAI were performed at the discretion of the operator. With VGA, additional lesions to isolate the LA posterior wall were performed if voltage mapping of this region in sinus rhythm showed scar (LA voltage < 0.5 mV). AF-/AT-free endpoint was defined as no sustained AF/AT seen off antiarrhythmic medications after a 2-month postablation blanking period. Seventy-six patients underwent SA and 65 underwent VGA. Patients were well matched for comorbidities, LVEF, and left atrial size. Posterior wall ablation was performed in 57% of patient with SA compared to 42% with VGA. VGA ablation increased 1-year AF-/AT-free survival in patients when compared to SA (80% vs. 57%; P = 0.005). In a multivariate analysis, VGA was the only independent predictor of AF-/AT-free survival (hazard ratio of 0.30; P = 0.002). CONCLUSIONS: The presence of LA posterior wall scar may be an important ablation target in persistent AF. A prospective randomized trial is needed to confirm these data.

Does manual T-wave window adjustment affect microvolt T-wave alternans results in patients with structural heart disease?

INTRODUCTION: Microvolt T-wave alternans (MTWA) analysis can identify patients at low risk of sudden cardiac death who might not benefit from an implantable cardioverter-defibrillator (ICD). Current spectral methodology for performing MTWA analysis may "miss" part of the T-wave in patients with QT prolongation. The value of T-wave window adjustment in patients with structural heart disease has not been studied. METHODS: We assembled MTWA data from 5 prior prospective studies including 170 patients with reduced left ventricular ejection fraction, adjusted the T-wave window to include the entire T-wave, and reanalyzed MTWA. RESULTS: Of 170 patients, 43% required T-wave window adjustment. Only 3 of 170 patients (1.8%) had a clinically significant change in MTWA results. CONCLUSIONS: In 98.2% of patients, T-wave window adjustment did not improve the accuracy of MTWA analysis. Spectral MTWA as currently implemented remains effective for identifying patients with structural heart disease unlikely to benefit from ICD therapy.

Atrial fibrillation symptom reduction and improved quality of life following the hybrid convergent procedure: a CONVERGE trial subanalysis.

Background: CONVERGE was a prospective, multicenter, randomized controlled trial that evaluated the safety of Hybrid Atrial Fibrillation Convergent (HC) and compared its effectiveness to endocardial catheter ablation (CA) for the treatment of persistent atrial fibrillation (PersAF) and longstanding PersAF (LSPAF). In 2020, we reported that CONVERGE met its primary safety and effectiveness endpoints. The primary objective of the present study is to report CONVERGE trial results for quality of life (QOL) and Class I/III anti-arrhythmic drug (AAD) utilization following HC. Methods: Eligible patients had drug-refractory symptomatic PersAF or LSPAF and a left atrium diameter ≤6.0 cm. Enrolled patients were randomized 2:1 to receive HC or CA. Atrial Fibrillation Severity Scale (AFSS) and the 36-Item Short Form Health Survey (SF-36) were assessed at baseline and 12 months; statistical comparison was performed using paired t-tests. AAD utilization at baseline through 12 and 18 months post-procedure was evaluated; statistical comparison was performed using McNemar's tests. Results: A total of 153 patients were treated with either HC (n=102) or CA (n=51). Of the 102 HC patients, 38 had LSPAF. AFSS and SF-36 Mental and Physical Component scores were significantly improved at 12 months versus baseline with HC overall and for the subset of LSPAF patients treated with either HC or CA. The proportion of HC patients (n=102) who used Class I /III AADs at 12 and 18 months was significantly less (33.3% and 36.3%, respectively) than baseline (84.3%; P<0.001). In LSPAF patients who underwent HC (n=38), AADs use was 29.0% through 18 months follow-up versus 71.1% at baseline (P<0.001). Conclusions: HC reduced AF symptoms, significantly improved QOL, and reduced AAD use in patients with PersAF and LSPAF. ClinicalTrialsgov Identifier: NCT01984346.

Hybrid epicardial-endocardial ablation for long-standing persistent atrial fibrillation: A subanalysis of the CONVERGE Trial.

Background: Favorable clinical outcomes are difficult to achieve in long-standing persistent atrial fibrillation (LSPAF) with catheter ablation (CA). The CONVERGE (Convergence of Epicardial and Endocardial Ablation for the Treatment of Symptomatic Persistent Atrial FIbrillation) trial evaluated the effectiveness of hybrid convergent (HC) ablation vs endocardial CA. Objective: The study sought to evaluate the safety and effectiveness of HC vs CA in the LSPAF subgroup from the CONVERGE trial. Methods: The CONVERGE trial was a prospective, multicenter, randomized trial that enrolled 153 patients at 27 sites. A post hoc analysis was performed on LSPAF patients. The primary effectiveness was freedom from atrial arrhythmias off new or increased dose of previously failed or intolerant antiarrhythmic drugs (AADs) through 12 months. The primary safety endpoint was major adverse event incidence through 30 days with HC. Key secondary effectiveness measures included (1) percent of patients achieving ≥90% AF burden reduction vs baseline and (2) AF freedom. Results: Sixty-five patients (42.5% of total enrollment) had LSPAF; 38 in HC and 27 in CA. Primary effectiveness was 65.8% (95% confidence interval [CI] 50.7%-80.9%) with HC vs 37.0% (95% CI 5.1%-52.4%) with CA (P = .022). Through 18 months, these rates were 60.5% (95% CI 50.0%-76.1%) with HC vs 25.9% (95% CI 9.4%-42.5%) with CA (P = .006). Secondary effectiveness rates were higher than CA with HC at 12 and 18 months. Freedom from atrial arrhythmias off AADs was 52.6% (95% CI 36.8%-68.5%) and 47.4% (95% CI 31.5%-63.2%) with HC at 12 and 18 months vs 25.9% (95% CI 9.4%-42.5%) and 22.2% (95% CI 6.5%-37.9%) with CA, respectively (12 months: P = .031; 18 months: P = .038). Three (7.9%) major adverse events occurred within 30 days of HC. Conclusion: Post hoc analysis demonstrated effectiveness and acceptable safety of HC compared with CA in LSPAF.

Quantitative electrocardiography for predicting postoperative atrial fibrillation after cardiac surgery.

BACKGROUND: Atrial fibrillation (AF) after cardiac surgery is a common marker of poor outcomes. Quantitative electrocardiographic (ECG) measurements may be valuable predictors of postoperative AF. METHODS: We evaluated clinical and ECG predictors of postoperative AF in 13,356 patients who underwent cardiac surgery in sinus rhythm. RESULTS: A total of 4724 patients (35%) developed postoperative AF. P-wave amplitude in leads aVR and V(1) were the strongest ECG predictors. A less negative P-wave amplitude in lead aVR was associated with increased risk for postoperative AF (odds ratio, 1.46; 95% confidence interval, 1.32-1.61), as was a more positive or a more negative P-wave amplitude in lead V(1) (odds ratio, 1.25; 95% confidence interval, 1.16-1.36) after adjusting for clinical and procedural predictors of postoperative AF. Reclassification analysis showed a 7% discrimination improvement (P < .0001). CONCLUSIONS: P-wave amplitude in lead aVR and lead V(1) are powerful predictors of postoperative AF and, in combination with other clinical predictors, can guide application of prophylactic interventions.

Role of microvolt T-wave alternans in assessment of arrhythmia vulnerability among patients with heart failure and systolic dysfunction: primary results from the T-wave alternans sudden cardiac death in heart failure trial substudy.

BACKGROUND: Sudden cardiac death remains a leading cause of mortality despite advances in medical treatment for the prevention of ischemic heart disease and heart failure. Recent studies showed a benefit of implantable cardioverter defibrillator implantation, but appropriate shocks for ventricular tachyarrhythmias were noted only in a minority of patients during 4 to 5 years of follow-up. Accordingly, better risk stratification is needed to optimize patient selection. In this regard, microvolt T-wave alternans (TWA) has emerged as a potentially useful measure of arrhythmia vulnerability, but it has not been evaluated previously in a prospective, randomized trial of implantable cardioverter defibrillator therapy. METHODS AND RESULTS: This investigation was a prospective substudy of the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) that included 490 patients at 37 clinical sites. TWA tests were classified by blinded readers as positive (37%), negative (22%), or indeterminate (41%) by standard criteria. The composite primary end point was the first occurrence of any of the following events: sudden cardiac death, sustained ventricular tachycardia/fibrillation, or appropriate implantable cardioverter defibrillator discharge. During a median follow-up of 30 months, no significant differences in event rates were found between TWA-positive or -negative patients (hazard ratio 1.24, 95% confidence interval 0.60 to 2.59, P=0.56) or TWA-negative and nonnegative (positive and indeterminate) subjects (hazard ratio 1.28, 95% confidence interval 0.65 to 2.53, P=0.46). Similar results were obtained with the inclusion or exclusion of patients randomized to amiodarone in the analyses. CONCLUSIONS: TWA testing did not predict arrhythmic events or mortality in SCD-HeFT, although a small reduction in events (20% to 25%) among TWA-negative patients cannot be excluded given the sample size of this study. Accordingly, these results suggest that TWA is not useful as an aid in clinical decision making on implantable cardioverter defibrillator therapy among patients with heart failure and left ventricular systolic dysfunction.

Basic Principles of Cardiac Electrophysiology.

This article represents an overview of the basic concepts of cardiac electrophysiology. This relatively new field became a subspecialty of cardiology in the mid-1990s due to the rapid development of equipment that allowed the study and cure of cardiac arrhythmias percutaneously. Simultaneously, technology provided the field with percutaneous cardiac implantable electronic devices designed to protect patients from life-threatening bradyarrhythmias and tachyarrhythmias. Recently, the field has focused on the ablative treatment of atrial fibrillation, the most common arrhythmia facing an aging population, and the diagnosis and management of many inherited arrhythmias through advances in understanding of their genetic cause.

The Electrocardiogram: Still a Useful Tool in the Primary Care Office.

A 12-lead electrocardiogram (ECG) is the most commonly ordered cardiac test. Although data are not robust, guidelines recommend against performing an ECG in patients who are asymptomatic, even if they have a higher risk of developing cardiovascular disease in the long term. Conversely, patients with cardiac symptoms, including chest pain, dyspnea, palpitation, and syncope, should have an ECG performed in the office. Computerized algorithms exist ubiquitously to guide interpretation, but they can be the source of erroneous information. A stepwise approach is given to guide the primary care physician's approach to the systematic interpretation of ECG tracings.

Inherited Cardiac Arrhythmias and Channelopathies.

With recent advances in genetic diagnostics, many inherited diseases, which can cause life-threatening arrhythmias, are being better characterized. Many of these diseases are caused by genetic disorders that affect the function of the ion channels that regulate the action potential or the function of important cardiac muscle regulatory proteins. This article summarizes the diseases that we have learned about, such as the long QT syndrome, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia. The article examines the diagnosis, genetic screening of patients and their relatives, management, and referral to a specialist for further therapy.

Arrhythmias in Congenital Heart Disease.

Cardiac defects are the most common congenital defects, accounting for approximately 9 per 1000 births. Patients with structural heart disease related to congenital diseases are prone to develop intrinsic rhythm abnormalities as a result of altered physiology. In addition, they are at an increased risk of developing acquired arrhythmias secondary to the nature of surgical interventions done to improve physiologic function in the setting of these defects. Arrhythmia management and risk stratification pose particularly complex challenges to clinicians managing this population.

Tachyarrhythmias and Bradyarrhythmias: Differential Diagnosis and Initial Management in the Primary Care Office.

Tachyarrhythmias and bradyarrhythmias are often seen in the outpatient setting. Patients can present minimally symptomatic or in extremis. Accurate diagnosis of the rhythm, plus a detailed clinical history, are critical for best management and optimal outcome. A 12-lead electrocardiogram is the cornerstone for diagnosis. Practitioners must identify patients who need immediate transport to an emergency department versus those who can safely wait for an outpatient specialty referral. This article reviews how to accurately diagnose and differentiate the most common tachyarrhythmias and bradyarrhythmias, the associated symptoms, and important concepts for the initial steps in the office management of such arrhythmias.

Perioperative heart-type fatty acid binding protein levels in atrial fibrillation after cardiac surgery.

BACKGROUND: Postoperative atrial fibrillation (POAF) is common and associated with poor outcomes. Perioperative ischemia can alter arrhythmic substrate. OBJECTIVE: To demonstrate an association between perioperative measurements of heart-type fatty acid binding protein (HT-FABP), a sensitive marker of ischemic myocardial injury. METHODS: Blood samples from 63 inpatients undergoing coronary artery bypass surgery, valve surgery, or both were obtained before and up to 4 days after surgery. Continuous telemetry monitoring was used to detect POAF. Fifty-nine patients had at least 3 HT-FABP measurements. The relationship of enzyme-linked immunosorbent assay-measured HT-FABP with POAF was assessed by using joint logistic regression adjusted for age and surgery type. RESULTS: Thirty-five patients (55%) developed POAF; these were, on average, older (69.3±10 years vs 60±11 years; P = .0019), with a higher prevalence of heart failure (43% vs 17%; P = .034), chronic obstructive lung disease (26% vs 4%; P = .017), preoperative calcium channel blocker use (29% vs 7%; P = .031), and more likely to undergo combined surgery (21% vs 11%, P = .049). The joint age- and coronary artery bypass surgery-adjusted model revealed that postoperative but not preoperative HT-FABP levels predicted POAF (coefficient 1.9±0.87; P = .03). Longer bypass time, prior infarction, and worse renal function were all associated with higher postoperative HT-FABP. CONCLUSIONS: A greater rise of HT-FABP is associated with atrial fibrillation after cardiac surgery, suggesting that ischemic myocardial damage is a contributing underlying mechanism. Interventions that decrease perioperative ischemic injury may also decrease the occurrence of POAF.

Positive predictive value of device-detected atrial high-rate episodes at different rates and durations: an analysis from ASSERT.

BACKGROUND: Pacemakers can automatically identify and catalog atrial high-rate episodes (AHREs). While most AHREs represent true atrial tachyarrhythmia/atrial fibrillation (AT/AF), a review of stored electrograms suggests that a substantial proportion do not. As AHREs may lead to the initiation of oral anticoagulation, it is crucial to understand the relationship between AHREs and true AT/AF. OBJECTIVE: To compare the positive predictive value of AHREs for electrogram-confirmed AT/AF for various atrial rates and episode durations. METHODS: By using data from 2580 patients who participated in the ASymptomatic atrial fibrillation and Stroke Evaluation in pacemaker patients and the AF Reduction atrial pacing Trial, all AHREs >6 minutes and >190 beats/min with available electrograms were reviewed to determine whether they represented true AT/AF. The positive predictive value of these AHREs was assessed for episode durations of 6 minutes, 30 minutes, 6 hours, and 24 hours at atrial rates of 190 and 250 beats/min. RESULTS: Of 5769 AHREs >6 minutes and >190 beats/min, 82.7% were true AT/AF and 17.3% were false positives (predominantly due to repetitive non-re-entrant ventriculoatrial synchrony). False positives dropped to 6.8%, 3.3%, and 1.8% when the threshold duration was increased to 30 minutes, 6 hours, and 24 hours, respectively. Increasing the threshold heart rate to 250 beats/min added little to the positive predictive value when longer threshold durations were used. CONCLUSIONS: By using a cutoff of >6 minutes and >190 beats/min, the rate of false-positive AHREs is 17.3%, making physician review of electrograms essential. For AHREs lasting >6 hours, the rate of false positives is 3.3%, making physician review less crucial.

Influence of race on atrial fibrillation after cardiac surgery.

BACKGROUND: Despite having fewer risk factors for atrial fibrillation (AF), white patients have a greater prevalence of AF in the community than black patients, and a genetic basis has been postulated. However, it is unknown whether occurrence of new-onset AF after cardiac surgery is different in white versus black patients, and secondarily, other non-Caucasian patients. METHODS AND RESULTS: From 1995 through 2005, 20 282 white, 1323 black, and 1919 other non-Caucasian patients in sinus rhythm underwent coronary artery bypass grafting with or without valve surgery. To adjust for clinical and socioeconomic confounders, we performed propensity-adjusted analyses; 7093 white patients (35%) had postoperative AF, compared with 255 (22%) black patients and 550 (29%) other non-Caucasians (P<0.0001). Whites were older than black patients, had higher socioeconomic position, and greater left atrial size but were less likely to have hypertension or congestive heart failure. In 847 propensity-matched patient pairs, postoperative AF occurred more frequently in white than in black patients (odds ratio, 1.74; 95% confidence interval, 1.7-1.78). Other than higher occurrence of bradycardia requiring pacing and reintubation in white patients, occurrence of other postoperative complications, hospital mortality, and length of postoperative stay were similar. Age and valvular surgery were the strongest predictors of AF irrespective of race. CONCLUSIONS: White patients had a markedly higher risk of postoperative AF than black and other non-Caucasian patients. The cause for racial differences of arrhythmic risk is unknown, but a genetic predisposition is plausible. Our results have implications for risk stratification and mechanistic understanding of postoperative AF.

Microvolt T-wave alternans and electrophysiologic testing predict distinct arrhythmia substrates: implications for identifying patients at risk for sudden cardiac death.

BACKGROUND: Better risk stratification of patients receiving an implantable cardioverter-defibrillator (ICD) for primary prevention of sudden cardiac death (SCD) is needed. Although microvolt T-wave alternans (MTWA) and electrophysiologic study (EPS) are independent markers for SCD, the Alternans Before Cardioverter Defibrillator (ABCD) trial found the combination to be more predictive than either test alone. OBJECTIVE: The purpose of this study was to test the hypothesis that EPS and MTWA measure different elements of the arrhythmogenic substrate and, therefore, predict distinct arrhythmia outcomes. METHODS: The ABCD trial enrolled 566 patients with ischemic cardiomyopathy, left ventricular ejection fraction (LVEF) 0.30. CONCLUSION: The study data suggest that EPS and MTWA identify distinct arrhythmogenic substrates and, when used in combination, may better predict the complex electroanatomic substrates that underlie the risk for SCD.

Risk Stratification for Sudden Cardiac Death: The Need to Go Beyond the Left Ventricular Ejection Fraction.

Sudden cardiac death (SCD) accounts for as many as 450,000 deaths yearly in the United States. Over the last 15 years, many clinical trials have established the effectiveness of an implantable cardioverter-defibrillator (ICD) in reducing sudden and total mortality in patients with structural heart disease. However, controversy remains about exactly how to identify the patients most likely to benefit from an ICD, as well as those who may safely do without an ICD implant. The first primary prevention ICD trials used an abnormal electrophysiological study in addition to a low left ventricular ejection fraction (LVEF) as high-risk markers for SCD. More recent ICD trials selected patients based on the presence of a low LVEF alone. Ideally, noninvasive electrophysiological markers that more directly reflect arrhythmia substrates may better identify patients for prophylactic ICD implant. Several of these markers have been associated with the risk of SCD, but all have yielded contradictory outcome results or have not been tested prospectively. This review focuses on the most promising tests to date, their clinical significance, and their possible use to improve efficacy and efficiency of risk stratification for SCD.

The ABCD (Alternans Before Cardioverter Defibrillator) Trial: strategies using T-wave alternans to improve efficiency of sudden cardiac death prevention.

OBJECTIVES: Because risk stratification with electrophysiological study (EPS) improves efficiency but is invasive, we sought to determine whether noninvasive microvolt T-wave alternans (MTWA) testing could identify patients who benefit from implantable cardioverter-defibrillators (ICDs) as well as EPS. BACKGROUND: Prevention of sudden cardiac death on the basis of left ventricular ejection fraction (LVEF) alone is inefficient, because most ICDs never deliver therapy. METHODS: The ABCD (Alternans Before Cardioverter Defibrillator) trial is a multicenter prospective study that enrolled patients with ischemic cardiomyopathy (LVEF < or =0.40) and nonsustained ventricular tachycardia. All patients underwent MTWA and EPS. ICDs were mandated if either test was positive. RESULTS: Of 566 patients followed for a median of 1.9 years, 39 (7.5%) met the primary end point of appropriate ICD discharge or sudden death at 1 year. As hypothesized, primary analysis showed that MTWA achieved 1-year positive (9%) and negative (95%) predictive values that were comparable to EPS (11% and 95%, respectively). In addition, secondary analysis showed that at the pre-specified 1-year end point, event rates were significantly higher in patients with both a positive MTWA-directed strategy (hazard ratio: 2.1, p = 0.03) and a positive EPS-directed strategy (hazard ratio: 2.4, p = 0.007). Moreover, the event rate in patients with both negative MTWA test and EPS was lower than in those with 2 positive tests (2% vs. 12%; p = 0.017). CONCLUSIONS: The ABCD study is the first trial to use MTWA to guide prophylactic ICD insertion. Risk stratification strategies using noninvasive MTWA versus invasive EPS are comparable at 1 year and complementary when applied in combination. Strategies employing MTWA, EPS, or both might identify subsets of patients least likely to benefit from ICD insertion. (Study to Compare TWA Test and EPS Test for Predicting Patients at Risk for Life-Threatening Heart Rhythms [ABCD Study]; NCT00187291).