Meta-analysis of p-wave dispersion values in healthy individuals: the influence of clinical characteristics

The Effect of Glycemic Status on P Wave Dispersion

Background and aim The growing number of people with diabetes mellitus (DM) across the world is a public health concern. The diabetes epidemic involves enormous health costs to the patients, their careers, and society at large. Cardiovascular diseases such as atrial fibrillation (AF) often develop in the diabetic population. An increase in the P wave dispersion (PWD) has been established as an independent risk factor for the occurrence of AF, hence the present study was conducted to establish a possible relationship between PWD and the glycemic status of the individual to predict the occurrence of AF ahead of clinical symptomology. Methodology A comparative cross-sectional study was conducted at a tertiary care hospital after obtaining approval from the institutional ethics committee and written consent of each study subject. The main steps included the selection and categorization of the study population based on their glycemic status, collection of demographic data, performing ECGs calculating PWD using digital calipers, and recording the data systematically for evaluation. Results In this study, 234 patients with a mean age of 53.3 ± 13.1 years were studied, of which 121 (51.7%) were male and 113 (48.29%) were female. The 234 patients were divided into four groups based on their glycemic status - 74 uncontrolled DM patients (31.62%), 51 type 2 DM (T2DM) patients (21.78%), 56 prediabetes patients (23.93%), and 53 patients in the control group (22.64%; not a known case of diabetes with normal HbA1c and fasting blood sugar (FBS) levels). Minimal correlation was observed between FBS with PWD (r value 0.175) and age with PWD (r value 0.161), but statistical significance was observed only between age and PWD (p-value 0.014). The difference in means between the four different study groups was found to be not statistically significant (p-value- 0.104); hence, no intergroup variation was noted. Conclusion Advancing age and higher fasting blood sugars have shown minimal correlation with widening P-wave dispersion. With further studies involving larger populations, this can be a promising aid in identifying PWD as a probable early predictor of atrial arrhythmias among diabetic patients.

The prognostic value of P-wave dispersion and left atrial functions assessed with three-dimensional echocardiography in patients with cirrhosis

BACKGROUND

Cirrhotic cardiomyopathy (CCM) is a well-known entity. The aim of this study was to compare left atrial three-dimensional (3D) volume and P-wave dispersion (PWd) in patients with cirrhosis and a healthy population. The secondary purpose was to assess the left phasic volumes and reservoir functions with 3D echocardiography for the prediction of an increased risk of poor outcomes in patients with cirrhosis.

METHODS

The study included 50 patients with cirrhosis and 43 healthy control subjects without atrial fibrillation. All patients were assessed with two-dimensional (2D), 3D, and tissue Doppler transthoracic echocardiography. The PWd was calculated using a 12-lead surface electrocardiogram (ECG). Cirrhotic patients were followed up for 2.5 years for the evaluation of poor outcomes and the development of atrial fibrillation.

RESULTS

Patients with cirrhosis were observed to have significantly higher left atrial phasic volumes such as minimal left atrial volume (3D-LAVmin, P = 0.004) and indexed LAVmin (3D-LAVImin, P = 0.0001), and significantly decreased left atrial reservoir functions such as left atrial emptying volume (3D-LAEV, P = 0,001), left atrial ejection fraction (3D-LAEF, P = 0,001) on 3D echocardiography. PWd was determined to be significantly longer in the cirrhotic group compared with the control group (P = 0.003). In the 2.5-year follow-up period, poor outcomes occurred in 34 patients (22 patients died, six patients had liver transplantation, six patients developed atrial fibrillation/AHRE episodes). In Cox regression analysis, the MELD score (HR, 1.16 (1.06-1.26), P = 0.001) and 3D-LAVImin (HR, 0.95 (0.86-1.00), P = 0.040) were significantly associated with all-cause mortality. Cirrhotic patients with LAVImin of >15 ml/m2 were seen to have poor survival (long rank P = 0.033).

CONCLUSION

The results of this study showed that patients with cirrhosis had higher left atrial volume, longer PWd and worse diastolic functions compared with the control group. Higher disease severity scores were associated with left atrial function and volume. In addition, left atrial volume measured with 3DE was a strong predictor of future adverse events, and minimal left atrial volumes had a higher prognostic value than any other left atrial function indices.

Supraventricular arrhythmia in mitral valve prolapse : Predictive value of P-wave dispersion and atrial conduction time

BACKGROUND

The incidence of supraventricular arrhythmia (SVA) is high in patients with mitral valve prolapse (MVP). The purpose of our study was to determine the role of parameters showing atrial conduction heterogeneity such as P‑wave dispersion (PWD) and atrial electromechanical delay (AEMD) in predicting the development of SVA in MVP patients.

METHODS

A total of 76 patients with MVP (56 female, 20 male) were included in the study. The patients were divided into two groups according to the presence or absence of SVA: 36 patients were allocated to the non-SVA group and 40 patients to the SVA group. Heart rate variability (HRV), PWD, and AEMD values were determined and compared.

RESULTS

The PWD was found to be higher in the SVA group. Interatrial EMD was 32.00 ms (25.00-35.00) in patients with SVA while it was 18.00 ms in patients without SVA (11.00-23.75); the intra-atrial EMD was 17.0 ms (10.00-20.00) in patients with SVA whereas it was 10.00 ms (4.00-14.00) in patients without SVA. Lower HRV was found in the SVA group.

CONCLUSION

In the SVA group, PWD and AEMD were increased while HRV values were decreased. Noninvasive parameters may help predict the presence and incidence of SVA during the follow-up of this group of patients.

Utility of P-Wave Dispersion in the Prediction of Atrial Fibrillation

Prevention is important in the case of the most common sustained arrhythmia-atrial fibrillation, with the intention of obtaining both medical and economic benefits. Electrocardiographic parameters have been tested as predictors of atrial fibrillation in different settings, and indices of P-wave have been assiduously studied.Increased P-wave dispersion has been described in different illnesses and correlated with several echocardiographic and clinical parameters. Several studies have demonstrated the relationship between P-wave dispersion with the first episode or paroxysmal atrial fibrillation, as well as with the recurrence of atrial fibrillation after conversion to sinus rhythm. Despite of some critics, the current evidencesentitleus to continue studying P-wave dispersion and use it for identifying patients with risk for atrial fibrillation.

Effect of Aging on Left Atrial Compliance and Electromechanical Properties in Subjects Without Structural Heart Disease

Aging is associated with changes in left atrial (LA) structure and function. The present study aimed at describing the effect of aging on LA properties in a large cohort of subjects without structural heart disease. We divided 386 subjects (mean age 58 years [range 16 to 91]; 188 men [49%]) clinically referred for echocardiography according to age groups. The P-wave dispersion (PWD), reflecting total atrial conduction time, was measured on a 12-lead surface electrocardiogram as the difference between maximum and minimum P-wave duration. The PA-TDI duration reflecting the total atrial conduction time was measured on tissue Doppler imaging (TDI) as the time between onset of P wave on surface electrocardiogram to peak A'-wave velocity. Two-dimensional speckle-tracking echocardiography was used to assess LA reservoir function, reflecting LA compliance. In the overall population, mean PWD, PA-TDI, and LA reservoir strain were 43 ± 12 ms, 129 ± 27 ms, and 36 ± 13%, respectively. Increasing age was independently associated with prolonged PWD (β = 0.161; p <0.001), PA-TDI (β = 0.476; p <0.001), and reduced LA reservoir strain (β = -0.259; <0.001), suggesting age-related fibrotic changes of the LA myocardium. The association between age and LA reservoir strain was modulated by body mass index (β = -0.582; p <0.001) and LA volume index (β = -0.117; p = 0.014). In conclusion, aging is associated with longer PWD and PA-TDI duration along with a decrease in LA reservoir function. Obesity and larger LA volumes are independently associated with reduced LA compliance.

Effects of Nasal Septum Deviation and Septoplasty on Cardiac Arrhythmia Risk

OBJECTIVE

Upper airway obstruction (UAO) can result in cardiac complications, including arrhythmias and sudden cardiac death. Nasal septum deviation (NSD) is a common cause of UAO. The aim of this study was to assess the risk of cardiac arrhythmias in patients with NSD. To assess this risk, we measured noninvasive indicators of atrial arrhythmia (P-wave dispersion [Pd]) and ventricular arrhythmia (corrected QT dispersion [QTcd]) and compared these values between NSD patients and healthy subjects.

STUDY DESIGN

Prospective study.

SETTINGS

Tertiary referral center.

SUBJECTS AND METHODS

This study included 53 consecutive patients who had underwent septoplasty due to marked NSD. Electrocardiographic records were used to determine Pd and QTcd values preoperatively and 6 months postoperatively. Fifty-three consecutive age- and sex-matched subjects without any UAO were also examined as a control group.

RESULTS

Preoperative Pd and QTcd values were significantly higher in NSD patients than in the control group (Pd: 57.40 ± 14.21 vs 34.11 ± 7.12 milliseconds, P < .001; QTcd: 81.77 ± 16.39 vs 50.25 ± 11.51 milliseconds, P < .001, respectively). In addition, Pd and QTcd values were significantly greater in preoperative NSD patients when compared with the same patients postoperatively (Pd: 57.40 ± 14.21 vs 36.32 ± 8.9 milliseconds, P = .013; QTcd: 81.77 ± 16.39 vs 55.76 ± 11.4 milliseconds, P = .012, respectively).

CONCLUSION

In conclusion, NSD patients are at risk for both atrial and ventricular cardiac arrhythmias; however, septoplasty in these patients can relieve UAO and reduce the risk of arrhythmias.

The Effect of Synthetic Cannabinoids on P-Wave Dispersion: An Observational Study

OBJECTIVE

The aim of this study was to investigate the effect of synthetic cannabinoids (SC) on P-wave dispersion (PD) in patients who consume SC.

MATERIALS AND METHODS

The study population included 72 patients who consumed SC and 36 age- and sex-matched healthy controls. The severity of addiction was detected using the addiction profile index (BAPI). The PD was measured by 12-lead ECG obtained upon admission to hospital. Statistical analyses were performed using the SPSS v20.0 statistical software package.

RESULTS

The mean age of the patients and controls was 26.9 ± 7.0 and 26.3 ± 6.5 years, respectively. Mean duration of SC consumption was 1.7 ± 0.7 years. Mean BAPI score of patients who consumed SC was 12.8 ± 3.4. Patients who consumed SC had a significantly higher PD value than controls (37.7 ± 11.5 vs. 30.6 ± 6.4 ms, p < 0.001). The BAPI score was significantly correlated with PD value (r = 0.675, p < 0.001). In the linear regression model that included PD value, age and heart rate, PD value was significantly and independently correlated with BAPI score (r2 of the model = 0.339; p < 0.001).

CONCLUSIONS

In this study, patients who consumed SC had significantly higher PD values than controls, and the BAPI score correlated with the PD value. Hence SC consumption could lead to an increased risk of cardiovascular disease through prolonged PD. We recommend the use of the simple and inexpensive ECG to assess cardiovascular risk in patients who consume SC.

Longitudinal evaluation of P-wave dispersion and P-wave maximum in children after transcatheter device closure of secundum atrial septal defect

Transcatheter device closure of the secundum atrial septal defect (ASD) in children prevents atrial arrhythmias in older age. However, the benefits of favourable atrial electrocardiographic markers in these children remain elusive. We aimed to review the electrocardiographic markers of atrial activity in a longitudinal fashion. We retrospectively reviewed longitudinal data of all children who underwent transcatheter device closure at the National University Hospital between 2004 and 2013. The inclusion criteria included the presence of a secundum-type ASD with left to right shunt and evidence of increased right ventricular volume load (Q p/Q s ratio >1.5 and/or right ventricular dilatation). A total of 25 patients with a mean follow-up of 44.7 ± 33.47 (7.3-117.4) months were included. P maximum and P dispersion decreased at 2 months, P amplitude at 1 week and remained so until last follow-up. A positive trend was seen with a correlation coefficient of +0.12 for P maximum, +0.08 for P dispersion and 0.34 for P amplitude. There was a higher baseline P amplitude and P dispersion in patients who were older than 10 years and a non-significant trend to support an increase in both P maximum (71.0 ± 8.8 vs. 73.2 ± 12.7), P dispersion (17.0 ± 6.5 vs. 22.0 ± 11.3) and P amplitude (0.88 ± 0.25 vs. 1.02 ± 0.23) in patients with an ASD more than 15 mm compared with an ASD <15 mm. There is reduction in both P maximum and P dispersion as early as 2 months, which persisted on follow-up. Earlier closure may result in more favourable electrocardiographic results.

QT and P-wave dispersions in rheumatic heart disease: prospective long-term follow up

BACKGROUND

Simple electrocardiogram (ECG) markers have been used to evaluate conduction times. Acute rheumatic fever (ARF) is an autoimmune disease that affects these conduction times. The aim of this prospective long-term follow-up study was to evaluate QT, QTc and P-wave dispersions in children with ARF and chronic rheumatic heart disease (CRHD).

METHODS

Sixty-four patients with ARF, 33 patients with CRHD and 41 healthy, age- and sex-matched control subjects were included in the study. The ARF patients were divided into two subgroups: carditis and arthritis. Echocardiographic and ECG measurements at the onset of diagnosis and final evaluation were included.

RESULTS

QT, QTc and P-wave dispersions were significantly greater in both the ARF carditis and CRHD groups than the ARF arthritis and control subjects during the initial and final analysis (for all, P < 0.001). There was no significant statistical difference in QT, QTc and P-wave dispersion between the initial and final analysis in each groups. Severity of mitral regurgitation and left atrial enlargement were found to be positively correlated with P-wave dispersion (r = 0.438, P < 0.001; r = 0.127, P < 0.001, respectively). QT, QTc and P-wave dispersion greater than 52, 60 and 57 ms, respectively, had higher sensitivity and specificity for predicting ARF carditis.

CONCLUSION

These ECG measurements can be used in the diagnosis of ARF carditis as minor criteria with modified Jones criteria. In contrast, this increase in the dispersions is permanent in patients with ARF carditis.

Assessment of P-wave dispersion in children with atrial septal aneurysm

BACKGROUND

This was a prospective controlled study to determine the P-wave duration and P-wave dispersion in patients with atrial septal aneurysm.

METHODS

A total of 41 children with atrial septal aneurysm, including 21 boys and 20 girls (mean age 11.85 ± 3.8 years), and 32 controls, including 17 boys and 15 girls (mean age 12.3 ± 2.9 years), were included. P-wave dispersion was calculated from the 12-lead electrocardiogram. Cardiac functions, morphology of the aneurysm, and left atrial diameter were measured using conventional echocardiography. The diagnosis of atrial septal aneurysm was made when the base of the aneurysms with an excursion ratio ≥25% was found on echocardiography.

RESULTS

There was no significant difference between the patient and control groups in demographic, clinical findings, and M-mode echocardiographic parameters. The P-wave dispersion in patients with atrial septal aneurysm was significantly longer compared with the control group (64.4 ± 13.4 ms; p < 0.0001). Similarly, the the maximum duration of the P wave in the patient group was significantly longer compared with the control group (106.1 ± 13.3 ms; p < 0.001). The P-wave duration and dispersion were not correlated with age, gender, systolic and diastolic blood pressure, or m-mode echocardiographic parameters.

CONCLUSIONS

This study shows that P-wave dispersion is delayed in atrial septal aneurysm patients. Prolonged P-wave dispersion was determined to indicate electrical disturbance, and therefore it has an increased electrocardiographic risk of atrial arrhythmia in children with atrial septal aneurysm.

P-wave dispersion: an indicator of cardiac autonomic dysfunction in children with neurocardiogenic syncope

Neurocardiogenic syncope is the most frequent cause of fainting in childhood and adolescence. Although head-up tilt table testing (HUTT) was previously considered as the reference standard in the diagnosis of syncope, in children with a typical history of reflex syncope, normal physical examination, and electrocardiogram (ECG) are sufficient to cease investigation; however, according to recent reports, TT is indicated in patients in whom this diagnosis cannot be proven by initial evaluation. The hypothesis of this study is that P-wave dispersion (PWD) can be a useful electrocardiographic predictor of cardiac autonomic dysfunction in children with vasovagal syncope (VVS). The study was designed prospectively and included 50 children with positive and 50 children with negative HUTT who presented with at least two previous unexplained episodes of syncope as well as 50 sex- and age-matched healthy children as the control group. All standard 12-lead ECGs were obtained in patients and controls, and the difference between maximum and minimum durations of the P wave was defined as the PWD. A total of 100 children with VVS and 50 healthy controls were evaluated for the study. The P maximum values of HUTT-positive (HUTT[+]) patients were significantly greater than those in the HUTT-negative (HUTT[-]) and control groups(p < 0.05). In addition, mean PWD values were 50.2 ± 18.5, 39.6 ± 11.2 and 32.0 ± 11.2 ms in the HUTT(+), HUTT(-), and control groups, respectively. The difference between groups was statistically significant (p < 0.05). We suggest that PWD is an early sign of cardiac autonomic dysfunction in children with neurally mediated syncope and can be used as a noninvasive electrocardiographic test to evaluate orthostatic intolerance syndromes.

The effects of wenxin keli on p-wave dispersion and maintenance of sinus rhythm in patients with paroxysmal atrial fibrillation: a meta-analysis of randomized controlled trials

Objective. To evaluate the beneficial and adverse effects of Wenxin Keli (WXKL), alone or combined with Western medicine, on P-wave dispersion (Pd) and maintenance of sinus rhythm for the treatment of paroxysmal atrial fibrillation (PAF). Methods. Seven major electronic databases were searched to retrieve randomized controlled trials (RCTs) designed to evaluate the clinical effectiveness of WXKL, alone or combined with Western medicine, for PAF, with Pd or maintenance rate of sinus rhythm as the main outcome measure. The methodological quality of the included studies was assessed using criteria from the Cochrane Handbook for Systematic Review of Interventions, version 5.1.0, and analysed using RevMan 5.1.0 software. Results. Fourteen RCTs of WXKL were included. The methodological quality of the trials was generally evaluated as low. The results of meta-analysis showed that WXKL, alone or combined with Western medicine, was more effective in Pd and the maintenance of sinus rhythm, compared with no medicine or Western medicine alone, in patients with PAF or PAF complicated by other diseases. Seven of the trials reported adverse events, indicating that the safety of WXKL is still uncertain. Conclusions. WXKL, alone or combined with Western medicine, appears to be more effective in improving Pd as well as maintenance of sinus rhythm in patients with PAF and its complications.

A novel electrocardiographic index for the diagnosis of diastolic dysfunction

Background

Although the assessment of diastolic dysfunction (DD) is an integral part of routine cardiologic examinations, little is known about associated electrocardiographic (ECG) changes. Our aim was to investigate a potential role of ECG indices for the recognition of patients with DD.

Methods and Results

ECG parameters correlating with echocardiographic findings of DD were retrospectively assessed in a derivation group of 172 individuals (83 controls with normal diastolic function, 89 patients with DD) and their diagnostic performance was tested in a validation group of 50 controls and 50 patients. The patient group with a DD Grade 1 and 2 showed longer QTc (422±24ms and 434±32ms vs. 409±25ms, p<0.0005) and shorter Tend–P and Tend–Q intervals, reflecting the electrical and mechanical diastole (240±78ms and 276±108ms vs. 373±110ms, p<0.0001; 409±85ms and 447±115ms vs. 526±119ms, p<0.0001). The PQ–interval was significantly longer in the patient group (169±28ms and 171±38ms vs. 153±22ms, p<0.005). After adjusting for possible confounders, a novel index (Tend–P/[PQxAge]) showed a high performance for the recognition of DD, stayed robust in the validation group (sensitivity 82%, specificity 93%, positive predictive value 93%, negative predictive value 82%, accuracy 88%) and proved a substantial added value when combined with the indexed left atrial volume (LAESVI, sensitivity 90%, specificity 92%, positive predictive value 95%, negative predictive value 86%, accuracy 91%).

Conclusions

A novel electrocardiographic index Tend–P/(PQxAge) demonstrates a high diagnostic accuracy for the diagnosis of DD and yields a substantial added value when combined with the LAESVI.

How valuable is P-wave dispersion in the determination of carboxyhemoglobin levels?

Objective:

To determine whether or not wave/interval dispersions in electrocardiography (ECG) are increased, and to define whether wave and interval dispersions are correlated with carboxyhemoglobin (COHb) levels.

Methods:

ECG, complete blood count, and biochemical parameters were taken from 87 patients with carbon monoxide (CO) poisoning as well as 90 control patients with similar age, gender, and body mass index distribution. COHb levels were recorded in CO-poisoning patients. The COHb levels and the relationships with ECG parameters were studied.

Results:

Pmax, Pmin, Pd, PRmax, PRmin, PRd, QTmax, QTmin, QTd, cQTmax, cQTmin, cQTd, Tmax, Tmin, and Td in ECG were higher in intoxicated patients than the control group ( p < 0.05 for all). Pearson’s correlation analyses showed moderately significant positive correlations between COHb level and Pmax ( r = 0.224; p = 0.037) and Pd ( r = 0.222; p = 0.039). The receiver–operator characteristic (ROC) curve showed that a Pd value of 38 ms determined by ECG separates patients with a COHb ≥ 20% with area under the ROC curve of 0.78 (95%CI = 0.71–0.83), a sensitivity of 67.9% (95%CI = 59.4–75.6), a specificity of 95% (95%CI = 83.0–99.2], a positive predictive value of 97.9% (95%CI = 92.5–99.7), and a negative predictive value of 46.3% (95%CI = 35.3–57.7.)

Conclusion:

A significant increase in wave/interval dispersions in the ECG of CO-poisoning patients compared with controls may show that not only a part is affected but both atrium and the ventricles as a whole are affected by hypoxic ischemia. When COHb levels of the patients are unavailable, P dispersion on ECG may show CO poisoning level of the patient.

Electrocardiographic P wave changes after thoracoscopic pulmonary vein isolation for atrial fibrillation

BACKGROUND

Changes in P wave duration (PWD) and P wave area (PWA) have been described following catheter ablation for atrial fibrillation (AF). We hypothesize that video-assisted thoracoscopic pulmonary vein isolation (VATS-PVI) for AF results in decrease of PWD, PWA and P wave dispersion, which may resemble reverse electrical remodeling of the atrium after restoration of sinus rhythm.

METHODS

VATS-PVI consisted of PVI and ganglionic plexus ablation in 29 patients (mean age, 59 ± 7 years; 23 males; 17 paroxysmal AF) and additional left atrial lesions in patients with persistent AF. PWD and PWA were measured in ECG lead II, aVF and V2 of ECGs during sinus rhythm before, directly after, and 6 months postprocedure. P wave dispersion was derived from the 12 lead ECG.

RESULTS

Prior to VATS-PVI, PWD did not correlate with left atrial size and no difference in left atrial size was found between patients with paroxysmal or persistent AF (p = 0.27). Following VATS-PVI, PWD initially prolonged in all patients from 115 ± 4.6 ms to 131 ± 3.6 ms (p < 0.01) but shortened to 99 ± 3.2 ms after 6 months (p < 0.01). PWA was 5.60 ± 0.32 mV*ms at baseline, 6.44 ± 0.32 mV*ms post-VATS-PVI (P = NS), and 5.40 ± 0.28 mV*ms after 6 months (p = NS vs. baseline, p < 0.05 vs. post-VATS-PVI). P wave dispersion decreased in the persistent AF group from baseline 67 ± 3.3 to 64 ± 2.5 ms post-VATS-PVI (p = 0.30) and to 61 ± 3.4 ms after 6 months (p < 0.05).

CONCLUSIONS

PWD increases significantly directly after successful VATS-PVI in both groups. There was significant decrease in PWD after 6 months. Similarly, P wave dispersion decreased in the persistent group. These changes suggest an immediate procedure related effect, but the later changes may represent reverse electrical atrial remodeling following cessation of AF.

Medically treated anorexia nervosa is associated with normal P wave parameters

Anorexia nervosa (AN) is an increasingly common medical condition. Some studies have demonstrated an increased prevalence of atrial premature contractions and anatomical changes in AN patients. Our aim was to investigate P wave parameters and P wave dispersion, an electrocardiographic marker for supraventricular arrhythmias, and its effect on AN. The study group included 48 patients with AN, most hospitalized for a few weeks, and a matched control group. All participants underwent 12-lead electrocardiography (ECG) under strict standards. P wave length and P wave dispersion in each patient were computed from a randomly selected beat and an averaged beat, constructed from 7 to 12 beats, included in a 10-s ECG. There were no statistically significant differences found between the groups for minimal, maximal, average P wave duration and P wave dispersion, calculated either from a random beat or averaged beats. In conclusion, medically treated AN patients who have gained weight have normal P wave parameters, and therefore do not appear to have an increased electrocardiographic risk for atrial fibrillation compared with healthy controls. Further studies are required to evaluate the influence of different disease stages, electrolyte imbalance and other medical complications on P wave parameters and risk for supraventricular arrhythmias in AN patients.