Analysis of the P wave with signal averaging to assess the risk of atrial fibrillation after coronary artery bypass surgery

Temporary autonomic modulation with botulinum toxin type A to reduce atrial fibrillation after cardiac surgery

BACKGROUND

Postoperative atrial fibrillation (POAF) frequently complicates cardiac surgery and is associated with worse outcomes. The cardiac autonomic nervous system is implicated in the pathogenesis of POAF.

OBJECTIVE

The purpose of this study was to determine the efficacy and safety of selective cardiac autonomic modulation in preventing POAF.

METHODS

In this randomized, double-blind, placebo-controlled trial, adults undergoing cardiac surgery were randomized 1:1 to intraoperative injection of 250 units onabotulinumtoxinA (botulinum toxin type A [BoNTA]) or placebo into epicardial fat pads. The study was powered to detect a 40% reduction in relative risk of POAF. Time to first episode of in-hospital POAF was the primary outcome, evaluated in patients receiving injection. Additionally, incidence of POAF, length of stay (LOS), and adverse events were examined.

RESULTS

The trial assigned 145 patients to injection, 15 of whom were dropped before treatment, leaving 130 patients for analysis. Overall, 36.5% (23/63) of BoNTA-treated patients developed POAF compared with 47.8% (32/67) of placebo-treated patients. The time-to-event analysis revealed a hazard ratio of 0.69 (95% confidence interval 0.41-1.19; P = .18) for the BoNTA vs placebo arm. There were no significant differences in postoperative hospital LOS (median [interquartile range] 6.0 [3.4] vs 6.2 [3.7] days; P = .51) or adverse events prolonging LOS (27/63 [42.9%] vs 30/67 [44.8%]; P = .83) in patients receiving BoNTA vs placebo.

CONCLUSION

Epicardial injection of onabotulinumtoxinA was without discernible adverse effects, but we failed to detect a significant difference in risk of POAF. Future large-scale studies of epicardial onabotulinumtoxinA injection as a potential POAF prevention strategy should be designed to study smaller, but clinically meaningful, treatment effects.

Preoperative P-wave duration as a predictor of atrial fibrillation after coronary artery bypass grafting: A prospective cohort study with meta-analysis

Objectives

Methods

Results

Conclusion

A clinical approach to arrhythmias revisited in 2018 : From ECG over noninvasive and invasive electrophysiology to advanced imaging

Understanding arrhythmias and their treatment is not always easy. The current straightforward approach with catheter ablation and device therapy is an amazing achievement, but does not make management of underlying or other cardiac disease and pharmacological therapy unnecessary. The goal of this paper is to describe how much of the knowledge of the 1980s and early 1990s can and should still be applied in the modern treatment of patients with arrhythmias. After an introduction, this review will focus on paroxysmal atrial fibrillation and a prototype of ‘idiopathic’ ventricular arrhythmias, two diseases with a striking similarity, and will discuss the arrhythmogenesis. The ECG continues to play an important role in diagnostics. Both diseases are associated with a structurally normal heart; the autonomic nervous system plays an important role in triggering arrhythmias at both the atrial and ventricular level.

Predicting the risk of atrial fibrillation after coronary artery bypass surgery

Atrial fibrillation (AF) is the most common arrhythmia, with an incidence of 17-33%, after coronary artery bypass grafting (CABG) and it increases the cost of operative treatment. beta-Blocker therapy reduces markedly the incidence of postoperative AF. The more effective preventive methods, e.g. amiodarone therapy or atrial pacing, are not cost-effective for all the patients. Thus, identification of patients at high risk of AF after CABG would be helpful. This review summarizes the predictors of postoperative AF and the current methods for risk stratification. In summary, identification of the patients at high risk of postoperative AF remains a challenge. The clinical usefulness of most of the conventional factors, e.g. age or history of AF, is low. Even attempts to build logistic regression models based on the pre- and intraoperative variables have failed to provide powerful predictors for postoperative AF after CABG. From the new predictors, the P-wave duration in signal-averaged ECG looks promising. Sensitivity and negative predictive value are high, positive predictive value remains low, which limits its usefulness. Contrary, even detailed analysis of standard 12-lead ECG or measure of heart rate variability has failed to provide useful information for risk stratification. A new method for risk stratification has been developed in our centre. The diagnostic accuracy of high-rate atrial pacing seems to be sufficient to identify a group of patients to whom prophylactic treatment could be proactively targeted. Further experience is, however, warranted to verify significance of this method in everyday clinical practice.

Coronary Collateral Circulation: Any Effect on P-Wave Dispersion?

Coronary collateral circulation determines the severity of ischemic myocardial damage. Increased P-wave dispersion is an independent predictor for atrial fibrillation. Consistent evidence is little about the relation between coronary collateral circulation and arrhythmia risk. In this article, the effect of coronary collateral circulation on P-wave dispersion was evaluated. Collateral grade and P-wave dispersion were ascertained in 100 patients with ≥85% diameter stenoses in left anterior descending or right coronary arteries. Left ventricular function score was also determined in all patients. Coronary collateral circulation was absent in 32 patients, whereas 68 patients had coronary collateral circulation. Patients with collateral grade ≥1 had greater left ventricular function score than did patients with collateral grade 0 ( P = .048). However, there was no significant difference between P-wave dispersion of patients with and without coronary collateral circulation ( P = .45). The presence of coronary collateral circulation failed to exert a beneficial decreasing effect on P-wave dispersion.

Atrial gradient as a potential predictor of atrial fibrillation

OBJECTIVES

We tested the utility and comparability of the atrial gradient and atrial ERP as early markers of electrical remodeling and a propensity to atrial fibrillation (AF).

BACKGROUND

Pacing at physiologic rates from the left atrium alters the atrial gradient and is associated with atrial tachyarrhythmias. At these physiologic rates, there is no change in the atrial effective refractory period (ERP).

METHODS

Sixty-one chronically instrumented mongrel dogs in complete heart block were paced from the left or right atrium at 400 to 900 bpm for 46 +/- 3 days. Dogs were monitored weekly and electrophysiologic studies conducted to determine changes in the atrial gradient, ERP, and rhythm.

RESULTS

Rapid atrial pacing was associated with concordant decreases in atrial gradient, ERP, and occurrence of AF. Incidence of AF increased with increasing pacing rate. Although there ultimately was an equal incidence of AF with left atrial and right atrial pacing, the onset of AF occurred earlier with left atrial pacing. As expected, ERP decreased in both atria. Animals with long control ERP did not fibrillate.

CONCLUSIONS

Rapid pacing induces changes in atrial gradient, which can be used as a noninvasive marker of electrical remodeling. AF is accompanied by decreases in atrial gradient and ERP, and the incidence is highest in dogs with short control ERP.

Increases in P-Wave Dispersion Predict Postoperative Atrial Fibrillation After Coronary Artery Bypass Graft Surgery

Atrial fibrillation (AF) is a common complication after coronary artery bypass graft (CABG) surgery. In this study we examined the effect of surgery on atrial electrophysiology as measured by P-wave characteristics and to determine the potential predictive value of P-wave characteristics on the incidences of postoperative AF in patients undergoing CABG surgery. Patients undergoing elective CABG surgery were monitored by continuous electrocardiogram (ECG) telemetry during the in-hospital period until discharge for the occurrence of postoperative AF. Differences in P-wave characteristics (P-wave duration, amplitude, axis, dispersion, PR interval, segment depression, and dispersion) were compared between the pre- and postoperative 12-lead ECG measurements, and also between patients with and without postoperative AF. The association of postoperative AF and potential clinical predictors and P-wave characteristics were determined by multivariate logistic regression. Postoperative AF occurred in 81 (27%) of 300 patients. Univariate analysis showed that patients who subsequently developed postoperative AF compared with those without AF were significantly older (mean age 68 +/- 8 versus 63 +/- 10 yr, P < 0.0001), had a larger body surface area (BSA) (2.03 +/- 0.24 versus 1.92 +/- 0.22 m(2), P = 0.0002), were more likely to have a history of AF (8 of 81 versus 1 of 219, P = 0.003), used preoperative antiarrhythmic medications more frequently (7 of 81 versus 4 of 219, P = 0.01), and had a more frequent rate of return to the operating room for postoperative complications (9 of 81 versus 9 of 219, P = 0.029). Furthermore, the postoperative P-wave duration decreased to a larger extent (mean change -11.3 +/- 0.1 ms versus -8.4 +/- 0.1 ms, P < 0.0001), and the P-wave dispersion increased postoperatively to a larger extent (3.1 +/- 15.5 ms versus -1.6 +/- 14.6 ms, P = 0.028) in those who subsequently developed AF compared with those without AF. Multivariate logistic regression showed age (odds ratio [OR] = 1.1, 95% confidence interval [CI]: 1.06-1.15, P < 0.0001), BSA (OR = 38.1, 95% CI: 8.2-176, P < 0.0001), and an increase in postoperative P-wave dispersion (OR = 1.03, 95% CI: 1.01-1.05, P = 0.01) to be independent predictors of postoperative AF. No surgical factor was identified to be responsible for this postoperative change in atrial electrophysiology.

IMPLICATIONS

In addition to clinical factors, such as advanced age and body surface area, we demonstrated that electrophysiologic changes involving an increase in P-wave dispersion postoperatively independently predict atrial fibrillation after coronary artery bypass graft surgery.

Predictors and impact of atrial fibrillation after isolated coronary artery bypass grafting

OBJECTIVE

Although an extensive number of studies have attempted to identify predictors of new-onset atrial fibrillation (AFIB) after coronary artery bypass grafting (CABG), a strong predictive model does not exist. Prior studies have included patients recruited from multiple centers with variant AFIB prevalence rates and those who underwent CABG in combination with other surgical procedures. Also, most studies have focused on pre- and perioperative characteristics, with less attention given to the initial postoperative period. The purpose of this study was to comprehensively examine pre-, peri-, and postoperative characteristics that might predict new-onset AFIB in a large sample of patients undergoing isolated CABG in a single medical center, utilizing data readily available to clinicians in electronic data repositories. In addition, length of stay and selected postoperative complications and disposition were compared in patients with AFIB and no AFIB.

DESIGN

Retrospective, comparative survey.

SETTING

University-affiliated tertiary care hospital.

PATIENTS

Patients with new-onset AFIB who underwent isolated standard CABG or minimally invasive direct vision coronary artery bypass were identified from an electronic clinical data repository.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The prevalence of AFIB in the total sample (n = 814) was 31.9%. Predictors of AFIB included age (p =.0004), number of vessels bypassed (p =.013), vessel location (diagonal [p <.003] or posterior descending artery [p <.001]), and net fluid balance on the operative day (p =.015). Forward stepwise regression analysis produced a model that correctly predicted AFIB in only 24% of cases, with age (14%) and body surface area (9%) providing the most prediction. The incidence of embolic stroke was higher in AFIB (n = 8) vs. no AFIB (n = 4) patients, but stroke preceded AFIB onset in seven of eight cases. Subjects with AFIB had a longer stay (p =.0004), more intensive care unit readmissions (p =.0004), and required more assistance at hospital discharge (p =.017).

CONCLUSIONS

Despite attempts to examine comprehensively predictors of new-onset AFIB, we were unable to identify a robust predictive model. Our findings, in combination with prior work, imply that it may not be feasible to predict the development of new-onset AFIB after CABG using data readily available to the bedside clinician. In this sample, stroke was uncommon and, when it occurred, preceded AFIB in all but one case. As anticipated, AFIB increased length of stay, and patients with this complication required more assistance at discharge.

Detection of inter-atrial conduction defects with unfiltered signal-averaged P-wave ECG in patients with lone atrial fibrillation

AIMS

To demonstrate a possible inter-atrial conduction delay in patients with lone paroxysmal atrial fibrillation (PAF) using 'unfiltered' signal-averaged P-wave ECG (PSAECG) and compare these results with those obtained with conventional filter settings.

METHODS AND RESULTS

Twenty one patients with lone PAF and 20 healthy volunteers (control group) were enrolled in the study. An orthogonal lead surface ECG was high-pass filtered at 0.8 Hz, averaged with template matching, and combined into a spatial magnitude ('unfiltered' technique). Results were compared with conventionally filtered (40-300 Hz) PSAECG. The filtered technique revealed no differences in P-wave duration between the two groups (121 +/- 12 vs 128 +/- 15 ms, control and PAF groups respectively, ns). Double-peaked P-wave spatial magnitudes (interpeak distance >30 ms) were revealed in 11 of 21 PAF patients but only in two of 18 controls (P<0.01). The nadir in the spatial magnitude was located significantly later in the PAF group (114 +/- 13 vs 103 +/- 9 ms, P<0.01).

CONCLUSION

'Unfiltered' PSAECG revealed significant differences in orthogonal P-wave morphology in patients with lone PAF, indicating the possibility of an inter-atrial conduction delay, while conventional P-wave duration analysis failed to discriminate between the two groups.

Perioperative clinical predictors of atrial fibrillation occurrence following coronary artery surgery

OBJECTIVE

Atrial fibrillation (AF) is the most frequently encountered arrhythmic complication associated with coronary surgery. The aim of this paper was then to identify the clinical predictors of post-CABG AF occurrence.

METHODS

150 consecutive patients were included in this study and divided into two groups according to the absence (SR group, 104 male and 22 female, age 58.4+/-8.8 years) or presence (AF group, 23 male and 1 female, age 65.4+/-6.3 years) of post-CABG AF. Forty-seven perioperative variables were considered.

RESULTS

After univariate analysis, advanced age (SR vs. AF: 58.4+/-8.8 vs. 65.4+/-6.3, P < 0.001), an increased BMI (SR vs. AF: 26.1+/-2.7 vs. 27.4+/-2.5, P = 0.026), a prior history of paroxysmal AF (SR vs. AF: 3.2% vs. 16.7%, P = 0.028), left atrial enlargement (SR vs. AF: 21.1% vs. 70.8%, P < 0.001) and a more severe coronary artery disease (CAD) (SR vs. AF: no. of diseased vessels: 2.42+/-0.7 vs. 2.91+/-0.3, P = 0.001; three-vessel CAD (54.1% vs. 91.3%, P = 0.002) were the only factors that statistically differed between the groups. Multivariate logistic regression analysis identified left atrial enlargement (P < 0.0001), a prior history of paroxysmal AF (P = 0.007) and a more severe CAD (P = 0.0047) to be independent correlates for AF.

CONCLUSIONS

Post-CABG AF seems to require a well definite anatomical and electrical substrate that is generated by increased left atrial dimensions, a greater extension of coronary lesions and a possible electrical remodeling consequent to prior repetitive episodes of paroxysmal AF.

The role of P wave in prediction of atrial fibrillation after coronary artery surgery

Atrial fibrillation (AF) is a common arrhythmia after coronary artery bypass surgery (CABG). The purpose of this study was to determine the role of P wave duration, amplitude and dispersion in the prediction of AF after CABG. This study included 120 patients undergoing elective CABG. Clinical characteristics, 12-lead electrocardiogram (ECG), echocardiogram and coronary angiogram were obtained in all patients. We measured P wave duration, amplitude and dispersion from 12-lead ECG in each patient. After CABG, all patients were continuously monitored for AF attacks in the intensive care unit and ordinary ward. Our results showed that age greater than 60 years was the strongest predictor of postoperative AF (p<0.01), with a 3.7-fold greater likelihood of developing postoperative AF compared to ages less than 60 years. Gender was another independent predictor of postoperative AF, with men being 3.0 times more likely to develop postoperative AF compared to women (p = 0.03). The presence of prolonged P wave duration (> or =100 ms in lead II) was also an independent predictor (p = 0.04), with 2.9-fold greater risk of developing postoperative AF compared to a P wave duration of less than 100 ms. The P wave dispersion was similar between patients with and without postoperative AF (29+/-15 vs. 33+/-15 mm, p = NS). In conclusion, old age, male gender and prolonged P wave duration were independent predictors of AF after CABG. However, P wave dispersion and amplitude did not provide significant information in the prediction of postoperative AF.