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

Association between heart rate and cardiovascular death in patients with coronary heart disease: A NHANES-based cohort study

BACKGROUND

Due to the lack of research, this study aimed to assess the association between the specific range of heart rate and cardiovascular (CV) death in coronary heart disease (CHD) patients.

HYPOTHESIS

Heart rate of 70-79 bpm may be associated with reduced risk of CV death in CHD patients.

METHODS

This retrospective cohort study collected the data of CHD patients from the eight cycles of the Health and Nutrition Examination Survey (NHANES). The included patients were divided into four groups: <60, 60-69, 70-79, and ≥80 bpm. The start of follow-up date was the mobile examination center date, the last follow-up date was December 31, 2015. The average follow-up time was 81.70 months, and the longest follow-up time was 200 months. Competing risk models were developed to evaluate the association between heart rate and CV death, with hazard ratios (HRs) and 95% confidence intervals (CIs) calculated.

RESULTS

A total of 1648 patients with CHD were included in this study. CHD patients at heart rate of <60 (HR, 1.35; 95% CI, 1.34-1.36), 60-69 (HR, 1.05; 95% CI, 1.04-1.06) or ≥80 (HR, 1.39; 95% CI, 1.38-1.41) bpm had a higher risk of CV death than those at heart rate of 70-79 bpm.

CONCLUSIONS

Heart rate of <70 or ≥80 bpm was associated with an elevated risk of CV death among CHD patients. Continuous monitoring of heart rate may help to screen for health risks and offer early interventions to corresponding patients.

Impact of surgical weight loss on novel P-wave-related variables which are nominated as predictors of atrial arrhythmias

BACKGROUND

Bariatric surgery has been associated with reduced cardiovascular mortality and morbidity in obese patients. In this study, we aimed to evaluate the alterations of novel P-wave related atrial arrhythmia predictors in patients who achieved effective weight loss with bariatric surgery.

METHODS

The study included 58 patients who underwent bariatric surgery. We measured heart rate, PR, P wave (PW) max, PW min, Average P axis, P wave peak time (PWPT) in lead D2 and lead V1, terminal force in lead V1 (V1TF), and we estimated P wave dispersion (PWdis) interval both pre-operation and 6 months after operation.

RESULTS

Heart rate, PR, PW max, PW min, PWdis, Average P axis, PWPTD2, PWPTV1 and V1TF values, which were close to the upper limit in the pre-op period, showed statistically significant decreases at 6 months after the operation. The most prominent changes were observed in PW dis (51.15 ± 9.70 ms vs. 48.79 ± 9.50 ms, p = .010), PWPTD2 (55.75 ± 6.91 ms vs. 50.59 ± 7.67 ms, p < .001), PWPTV1 (54.10 ± 7.06 ms vs. 48.05 ± 7.64 ms, p < .001) and V1TF (25 [43.1%] vs. 12 [20.7%], p < .001).

CONCLUSIONS

The results of our study indicated that bariatric surgery has positive effects on the regression of ECG parameters which are predictors of atrial arrhythmias, particularly atrial fibrillation (AF).

Drug Therapy for Vagally-Mediated Atrial Fibrillation and Sympatho-Vagal Balance in the Genesis of Atrial Fibrillation: A Review of the Current Literature

Objective

The presence of both sympathetic activation-mediated triggers and parasympathetic activation-mediated substrates are required to initiate and maintain some forms of atrial fibrillation (AF). AF predominantly precipitated by parasympathetic stimulation is known as vagally-mediated AF (VM-AF). The role of novel drugs and molecular targeted gene therapy that modulate the autonomic nervous system are therapeutic options in this unique population with VM-AF. Here, we review the role of the sympatho-vagal balance in the genesis of AF and consider drug therapy for VM-AF.

Methods

In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement, literature search was conducted using the keywords "vagal", "vagal nerve", "vagus", "vagus nerve", and "atrial fibrillation". Retrieved citations were first screened independently by 2 reviewers for inclusion and exclusion criteria.

Results

A total of 14 studies and 3 practice guidelines from 1986-2017 were included. Only two clinical investigations evaluated the effectiveness of disopyramide and sotalol in human subjects with VM-AF. The potential role of antiarrhythmic drugs has been studied in animal models.

Conclusions

Growing evidence suggests that the autonomic nervous system is integral in the development of VM-AF. Novel medications and genetic targets are undergoing investigation with promising results.

Assessing Atrial Fibrillation Substrates by P Wave Analysis: A Comprehensive Review

Atrial fibrillation (AF) is the most common cardiac arrhythmia. Pharmacologic and non-pharmacologic rhythm control strategies impact on AF-related symptoms, while leaving largely unaffected the risk of stroke. Moreover, up to 20% of AF patients are asymptomatic during paroxysmal relapses of arrhythmia, thus underlying the need for early markers to identify at-risk patients and prevent cerebrovascular accidents. Indeed, non-invasive assessment of pre-clinical substrate changes that predispose to AF could provide early identification of at-risk patients and allow for tailored care paths. ECG-derived P wave analysis is a simple-to-use and inexpensive tool that has been successfully employed to detect AF-associated structural and functional atrial changes. Beyond standard electrocardiographic techniques, high resolution signal averaged electrocardiography (SAECG), by recording microvolt amplitude atrial signals, allows more accurate analysis of the P wave and possibly AF risk stratification. This review focuses on the evidence that support P wave analysis to assess AF substrates, predict arrhythmia relapses and guide rhythm-control interventions.

Novel electrocardiography parameter for paroxysmal atrial fibrillation in acute ischaemic stroke patients: P wave peak time

Introduction

In this study, we aimed to investigate the usefulness of P wave peak time (PWPT), a novel ECG parameter, in patients who were diagnosed with acute ischaemic stroke (IS) and had paroxysmal atrial fibrillation (PAF) on Holter monitoring.

Materials and methods

In this retrospective cohort study, we included 90 consecutive patients with acute IS who were admitted to our hospital between January 2017 and July 2019. PWPT was described as the time from the beginning of the P wave to its peak, and it was measured from leads DII and VI. The PAF diagnosis was confirmed if it was detected on the ECG during palpitation or in rhythm during the Holter recordings.

Results

In this study, 34 (37.7%) patients with acute IS were diagnosed with PAF. In multivariate analyses, the independent predictors of PAF were age, PWPT in lead VI and PWPT in lead DII (OR: 1.34, 95% CI 1.15 to 1.56; p<0.001). A receiver operating curve analysis demonstrated that area under the curve values for PWPT in lead DII for PAF were 0.88 (95% CI 0.81 to 0.95, p<0.001). The cut-off value for PWPT in lead DII in predicting PAF was 68.5 ms with a sensitivity of 82.4% and a specificity of 75.0%.

Conclusion

To the best of our knowledge, this is the first study to demonstrate a significant relationship between PWPT in lead DII and PAF among patients with acute IS.

P-wave duration in lead aVR and the risk of atrial fibrillation in hypertension

BACKGROUND

Hypertension entails atrial remodeling that affect P-wave (PW) duration on electrocardiogram (ECG). PW indices (e.g., variance, dispersion, and terminal force) are associated with a higher risk for atrial fibrillation (AF), but their calculation requires multiple measurements of PW duration, limiting their use in clinical practice. We evaluated whether PW duration in specific ECG leads may identify patients with increased susceptibility to AF in a population of hypertensive patients.

METHODS

In a case-control study, AF and control subjects were matched for age, sex, and left atrial (LA) dimensions. PW duration was measured from digitally stored ECGs. Logistic regression was used to assess the association of PW duration and indices with AF.

RESULTS

We enrolled 44 hypertensive AF patients (16 paroxysmal and 28 persistent) and 44 hypertensive controls. AF and control subjects were matched for sex (males, n = 27), age (67 ± 8 years), LA diameter (40 ± 5 mm), and were comparable for left ventricular mass (45 ± 11 g/m(2.7) vs 48 ± 12 g/m(2.7) , P = 0.19), ejection fraction (58 ± 7% in both groups), and prevalence of mild valvular heart disease (7% vs 5%; P = 0.64). PW duration in lead aVR was significantly higher in AF patients as compared with controls (115 ± 18 ms vs 101 ± 14 ms; P < 0.0001) and was the best independent predictor of AF in multivariable logistic regression (PW ≥ 100 ms: RR = 3.7; 95% CI: 1.3-10.3; P = 0.02).

CONCLUSIONS

Simple measurement of PW duration in lead aVR allows effective identification of AF patients in a population of hypertensives. Confirmation of this finding in a larger population would provide a simple and effective risk marker of AF in hypertensive patients.

P-wave morphology: underlying mechanisms and clinical implications

Increasing awareness of atrial fibrillation (AF) and its impact on public health revives interest in identification of noninvasive markers of predisposition to AF and ECG-based risk stratification. P-wave duration is generally accepted as the most reliable noninvasive marker of atrial conduction, and its prolongation has been associated with history of AF. However, patients with paroxysmal AF without structural heart disease may not have any impressive P-wave prolongation, thus suggesting that global conduction slowing is not an obligatory requirement for development of AF. P-wave morphology is therefore drawing increasing attention as it reflects the three-dimensional course of atrial depolarization propagation and detects local conduction disturbances. The factors that determine P-wave appearance include (1) the origin of the sinus rhythm that defines right atrial depolarization vector, (2) localization of left atrial breakthrough that defines left atrial depolarization vector, and (3) the shape and size of atrial chambers. However, it is often difficult to distinguish whether P-wave abnormalities are caused by atrial enlargement or interatrial conduction delay. Recent advances in endocardial mapping technologies have linked certain P-wave morphologies with interatrial conduction patterns and the function of major interatrial conduction routes. The value of P-wave morphology extends beyond cardiac arrhythmias associated with atrial conduction delay and can be used for prediction of clinical outcome of a wide range of cardiovascular disorders, including ischemic heart disease and congestive heart failure.

Alcohol and vagal tone as triggers for paroxysmal atrial fibrillation

Alcohol and vagal activity may be important triggers for paroxysmal atrial fibrillation (PAF), but it remains unknown if these associations occur more often than would be expected by chance alone because of the lack of a comparator group in previous studies. We compared self-reported frequency of these triggers in patients with PAF to those with other supraventricular tachycardias (SVTs). Consecutive consenting patients presenting for electrophysiology procedures at a single university medical center underwent a structured interview regarding arrhythmia triggers. Two hundred twenty-three patients with a documented arrhythmia (133 with PAF and 90 with SVT) completed the survey. After multivariable adjustment, patients with PAF had a 4.42 greater odds (95% confidence interval [CI] 1.35 to 14.44) of reporting alcohol consumption (p = 0.014) and a 2.02 greater odds (95% CI 1.02 to 4.00) of reporting vagal activity (p = 0.044) as an arrhythmia trigger compared to patients with SVT. In patients with PAF, drinking primarily beer was associated with alcohol as a trigger (odds ratio [OR] 4.49, 95% CI 1.41 to 14.28, p = 0.011), whereas younger age (OR 0.68, 95% CI 0.49 to 0.95, p = 0.022) and a family history of AF (OR 5.73, 95% CI 1.21 to 27.23, p = 0.028) each were independently associated with having vagal activity provoke an episode. Patients with PAF and alcohol triggers were more likely to have vagal triggers (OR 10.32, 95% CI 1.05 to 101.42, p = 0.045). In conclusion, alcohol consumption and vagal activity elicit PAF significantly more often than SVT. Alcohol and vagal triggers often were found in the same patients with PAF, raising the possibility that alcohol may precipitate AF by vagal mechanisms.