Age- and sex-related atrial electrophysiologic and structural changes

Immune cells and arrhythmias

Cardiac arrhythmias are a significant cause of morbidity and mortality worldwide. Emerging evidence has demonstrated that resident and infiltrating cardiac immune cells play direct, mechanistic roles in arrhythmia onset and progression. In this review, we provide a comprehensive summary and expert commentary on the role of each immune cell subtype in the pathogenesis of atrial and ventricular arrhythmias.

The Aging Heart: A Molecular and Clinical Challenge

Aging is associated with an increasing burden of morbidity, especially for cardiovascular diseases (CVDs). General cardiovascular risk factors, ischemic heart diseases, heart failure, arrhythmias, and cardiomyopathies present a significant prevalence in older people, and are characterized by peculiar clinical manifestations that have distinct features compared with the same conditions in a younger population. Remarkably, the aging heart phenotype in both healthy individuals and patients with CVD reflects modifications at the cellular level. An improvement in the knowledge of the physiological and pathological molecular mechanisms underlying cardiac aging could improve clinical management of older patients and offer new therapeutic targets.

Biatrial Volumetric Assessment by Non-ECG-Gated CT Pulmonary Angiography Correlated with Transthoracic Echocardiography in Patients with Normal Diastology

Atrial size is a predictor of cardiovascular mortality. Non-ECG-gated computed tomography pulmonary angiography (CTPA) is a common test for cardiopulmonary evaluation but normative values for biatrial volumes are lacking. We derived normal CT biatrial volumes using manual and semiautomated segmentation with contemporaneous transthoracic echocardiography (TTE) to confirm normal diastology. Thirty-five consecutive cases in sinus rhythm with no history of cardio-vascular, renal, or pulmonary disease and normal diastolic function were selected. Planimetric CTPA measurements were compared to TTE volumes measured using area length method. TTE and CTPA derived normal LAVi and RAVi were 27 + 5 and 20 + 6 mL/m², and 30 + 8 and 29 + 9 mL/m², respectively. Bland-Altman analysis revealed an underestimation of biatrial volumes by TTE. TTE-CT mean biases for LAV and RAV were -5.7 + 12.0 mL and -16.2 + 14.8 mL, respectively. The CT intraclass correlation coefficients (ICC 95% CI) for LA and RA volumes were 0.99 (0.96-1.00) and 0.96 (0.76-0.99), respectively. There was excellent correlation (p < 0.001) between the semiautomated and manual measurements for LA (r 0.99, 95% CI 0.98-0.99) and RA (r 0.99, 95% CI 0.99-1.00). Atrial volumetric assessment on CTPA is easy and reproducible and can provide additional metric in cardiopulmonary assessment.

Connexin Lateralization Contributes to Male Susceptibility to Atrial Fibrillation

Men have a higher risk of developing atrial fibrillation (AF) than women, though the reason for this is unknown. Here, we compared atrial electrical and structural properties in male and female mice and explored the contribution of sex hormones. Cellular electrophysiological studies revealed that action potential configuration, Na+ and K+ currents were similar in atrial myocytes from male and female mice (4–5 months). Immunofluorescence showed that male atrial myocytes had more lateralization of connexins 40 (63 ± 4%) and 43 (66 ± 4%) than females (Cx40: 45 ± 4%, p = 0.006; Cx43: 44 ± 4%, p = 0.002), with no difference in mRNA expression. Atrial mass was significantly higher in males. Atrial myocyte dimensions were also larger in males. Atrial fibrosis was low and similar between sexes. Orchiectomy (ORC) abolished sex differences in AF susceptibility (M: 65%; ORC: 38%, p = 0.050) by reducing connexin lateralization and myocyte dimensions. Ovariectomy (OVX) did not influence AF susceptibility (F: 42%; OVX: 33%). This study shows that prior to the development of age-related remodeling, male mice have more connexin lateralization and larger atria and atrial myocyte than females. Orchiectomy reduced AF susceptibility in males by decreasing connexin lateralization and atrial myocyte size, supporting a role for androgens. These sex differences in AF substrates may contribute to male predisposition to AF.

Incidence of atrial fibrillation and its effects on long-term follow-up outcomes in patients undergoing primary percutaneous coronary intervention for ST-elevation myocardial infarction

OBJECTIVE

The incidence of atrial fibrillation (AF) in patients with ST segment elevation myocardial infarction (STEMI) varies between 7% and 21%, and most of these studies were in the thrombolytic era. However, the frequency of new-onset AF during the primary percutaneous coronary intervention (PCI) period is still unclear. We aimed to investigate the frequency of new-onset AF and its effects on long-term clinical events in patients undergoing primary PCI.

METHODS

A total of 1,603 patients who were diagnosed with STEMI and underwent primary PCI were included in the study. All the patients were monitored for at least 48 hours after the procedure. The primary endpoint of the study was defined as new-onset AF during hospitalization.

RESULTS

The median follow-up period of our study was 44 months. New-onset AF developed in 85 (6.1%) patients. CHADs-VASc > 2, KILLIP > 2, and left atrial diameter were found to be independent predictors for the development of new-onset AF. In the AF (+) group, the all-cause and in-hospital mortality rates were found to be significantly higher. New-onset AF development in patients with STEMI was detected as an independent predictor of in-hospital mortality.

CONCLUSION

In the era of primary percutaneous transluminal coronary angioplasty, new-onset AF rates were found to be lower than the literature data. In addition, new-onset AF was found to be a predictor of in-hospital mortality, and deaths occurred mostly in the early period. Therefore, close follow-up of these patients in the early period and re-evaluation in terms of AF burden when the patient becomes stable are important.

Clinical and biological determinants of P-wave duration: cross-sectional data from the population-based CoLaus|PsyCoLaus study

OBJECTIVES

P-wave duration (PWD) is associated with the development of atrial arrhythmias, cardiovascular and all-cause mortality. With this study, we aimed to assess the distribution and determinants of PWD in the general population.

DESIGN

Cross-sectional study using data collected between 2014 and 2016.

SETTING

In the population-based cohort CoLaus|PsyCoLaus, Lausanne, Switzerland, we used 12-lead ECGs to measure PWD. Potential demographic, clinical and biological determinants of PWD were collected by questionnaire, anthropometry, blood pressure measurement and biological assays.

PARTICIPANTS

Data from 3459 participants (55% women, 62±10 years, 93% Caucasian) were included. Participants were excluded if they presented with (1) no sinus rhythm or paced rhythm on the study ECG or Wolff-Parkinson-White ECG pattern; (2) missing or non-interpretable ECG; and (3) missing phenotypic data.

PRIMARY OUTCOME MEASURE

Determine (1) the PWD distribution and (2) the demographic, clinical and biological determinants of PWD in a large population-based cohort.

RESULTS

Median and IQR of PWD was 112 (102-120) ms . In the multivariable analyses, PWD was significantly associated with age (p<0.001) and height (p<0.001), with an adjusted regression coefficient (95% CI) of 0.29 ms/years (0.23 to 0.36) and 0.32 ms/cm (0.28 to 0.37), respectively. PWD, given thereafter in ms with adjusted mean±SE, was significantly (p<0.05) associated with (a) gender (woman 110.0±0.4; man 112.1±0.4), (b) body mass index (normal 110.1±0.4; overweight 110.9±0.4; obese 113.0±0.5), (c) abdominal obesity (no 110.5±0.3; yes 111.7±0.4) and (d) hypertension (no 110.4±0.3; yes 111.7±0.4).

CONCLUSION

PWD is positively associated with age, height, male gender, obesity markers and hypertension. Clinical interpretation of PWD should take these factors into consideration.

The 2020 Canadian Cardiovascular Society/Canadian Heart Rhythm Society Comprehensive Guidelines for the Management of Atrial Fibrillation

The Canadian Cardiovascular Society (CCS) atrial fibrillation (AF) guidelines program was developed to aid clinicians in the management of these complex patients, as well as to provide direction to policy makers and health care systems regarding related issues. The most recent comprehensive CCS AF guidelines update was published in 2010. Since then, periodic updates were published dealing with rapidly changing areas. However, since 2010 a large number of developments had accumulated in a wide range of areas, motivating the committee to complete a thorough guideline review. The 2020 iteration of the CCS AF guidelines represents a comprehensive renewal that integrates, updates, and replaces the past decade of guidelines, recommendations, and practical tips. It is intended to be used by practicing clinicians across all disciplines who care for patients with AF. The Grading of Recommendations, Assessment, Development and Evaluations (GRADE) system was used to evaluate recommendation strength and the quality of evidence. Areas of focus include: AF classification and definitions, epidemiology, pathophysiology, clinical evaluation, screening and opportunistic AF detection, detection and management of modifiable risk factors, integrated approach to AF management, stroke prevention, arrhythmia management, sex differences, and AF in special populations. Extensive use is made of tables and figures to synthesize important material and present key concepts. This document should be an important aid for knowledge translation and a tool to help improve clinical management of this important and challenging arrhythmia.

Predictor of enhanced mortality in patients with multimorbidity and atrial fibrillation in an acute hospital setting

BACKGROUND

Patients with atrial fibrillation (AF) admitted to hospital commonly have comorbidities. Few studies have attempted to determine factors prognostic of mortality in hospitalized AF patients with multimorbidity.

AIM

To identify factors associated with mortality in hospitalized AF patients.

DESIGN

Retrospective cohort study.

METHODS

Patients with multimorbidity (≥2 chronic diseases), with or without AF, discharged from Lugo hospital (Spain) between 1 January 2000 and 31 December 2015. Data were extracted from hospital medical records.

RESULTS

Of 74 220 patients (170 978 hospitalizations), 52 939 had multimorbidity (14 181 had AF; 38 758 no AF) and were included in our study. Patients with AF were older (mean ± standard deviation 78.6 ± 10.0 vs. 71.9 ± 14.2 years) and had a higher mortality rate (27.1 vs. 20.5%) than those without AF. Gender (female), age, stroke and congestive heart failure (CHF), but not AF, were independently associated with mortality. AF significantly increased the mortality risk in women [relative risk (RR) 1.091; 95% confidence interval (CI) 1.021-1.165; P = 0.010] and in those aged >80 years (RR 1.153; 95% CI, 1.1-1.2; P < 0.001). CHF independently increased the risk of mortality across all age groups (RR 1.496; 95% CI 1.422-1.574; P < 0.001).

CONCLUSIONS

Hospitalized patients with AF have a higher mortality rate than those without AF. The prognostic significance of AF changes with age and gender while CHF is associated with the greatest risk of death.

Diagnostic accuracy of left atrial remodelling and natriuretic peptide levels for preclinical heart failure

AIMS

Left atrial (LA) remodelling is an important predictor of cardiovascular events of heart failure (HF) and atrial fibrillation. Data regarding diagnostic value of LA remodelling on diastolic dysfunction (DD) and preclinical HF remain largely unexplored.

METHODS AND RESULTS

We assessed LA dimension (LAD) in 8368 consecutive asymptomatic Asians (mean age: 49.7, 38.9% women) and related such measure to updated American Society of Echocardiography (ASE) DD criteria and newly revised N-terminal pro-brain natriuretic peptide (NT-proBNP) cut-off (≥125 pg/mL) and HF with preserved ejection fraction criteria incorporating NT-proBNP and echocardiography parameters by the European Society of Cardiology (ESC). LAD and indexed LAD (LADi) were both inversely correlated with myocardial relaxation e' and positively associated with indexed LA volume, left ventricular E/e', and tricuspid regurgitation velocity (all P < 0.001) and showed significantly graded increase across ASE-defined 'normal', 'inconclusive', and 'DD' categories (30.9, 34.4, and 36.5 mm; 16.7, 19.1, and 20.6 mm/m² , for LAD/LADi, both P for trend: <0.001, respectively). Substantial differences of LAD/LADi (31.3 vs. 33.6 mm/16.7 vs. 19.2 mm/m² , both P < 0.001) between ESC low and high HF probability using NT-proBNP cut-off were also observed. Multivariate linear and logistic models demonstrated that LAD set at 34 mm was independently associated with ASE-defined diastolic indices, DD existence, and elevated NT-proBNP (all P < 0.05). The use of LAD further yielded high diagnostic accuracy in DD (area under receiving operative characteristic curve: 0.77, 95% confidence interval [0.73, 0.80]; negative predictive value: 97.9%) and in ESC-recommended HF with preserved ejection fraction criteria (area under receiving operative characteristic curve: 0.70, 95% confidence interval [0.65, 0.75]; negative predictive value: 98.7%) with high predictive value in LA remodelling (>34 mL/m² ; positive predictive value: 96%) and well-discriminated ESC-recommended NT-proBNP (≥125 pg/mL, LAD: 37 mm) for HF.

CONCLUSIONS

Single utilization of atrial remodelling is highly useful for ruling out presence of DD and provides practical threshold for identifying preclinical HF based on most updated guidelines.

Sex Differences in Cardiovascular Risk Factors for Dementia

Dementia, characterized by a progressive cognitive decline and a cumulative inability to behave independently, is highly associated with other diseases. Various cardiovascular disorders, such as coronary artery disease and atrial fibrillation, are well-known risk factors for dementia. Currently, increasing evidence suggests that sex factors may play an important role in the pathogenesis of diseases, including cardiovascular disease and dementia. Recent studies show that nearly two-thirds of patients diagnosed with Alzheimer’s disease are women; however, the incidence difference between men and women remains vague. Therefore, studies are needed to investigate sex-specific differences, which can help understand the pathophysiology of dementia and identify potential therapeutic targets for both sexes. In the present review, we summarize sex differences in the prevalence and incidence of dementia by subtypes. This review also describes sex differences in the risk factors of dementia and examines the impact of risk factors on the incidence of dementia in both sexes.

Prediction of atrial fibrillation development and progression: Current perspectives

Atrial fibrillation (AF) is the most common arrhythmia in clinical practice. Several conventional and novel predictors of AF development and progression (from paroxysmal to persistent and permanent types) have been reported. The most important predictor of AF progression is possibly the arrhythmia itself. The electrical, mechanical and structural remodeling determines the perpetuation of AF and the progression from paroxysmal to persistent and permanent forms. Common clinical scores such as the hypertension, age ≥ 75 years, transient ischemic attack or stroke, chronic obstructive pulmonary disease, and heart failure and the congestive heart failure, hypertension, age ≥ 75 years, diabetes mellitus, stroke/transient ischemic attack, vascular disease, age 65-74 years, sex category scores as well as biomarkers related to inflammation may also add important information on this topic. There is now increasing evidence that even in patients with so-called lone or idiopathic AF, the arrhythmia is the manifestation of a structural atrial disease which has recently been defined and described as fibrotic atrial cardiomyopathy. Fibrosis results from a broad range of factors related to AF inducing pathologies such as cell stretch, neurohumoral activation, and oxidative stress. The extent of fibrosis as detected either by late gadolinium enhancement-magnetic resonance imaging or electroanatomic voltage mapping may guide the therapeutic approach based on the arrhythmia substrate. The knowledge of these risk factors may not only delay arrhythmia progression, but also reduce the arrhythmia burden in patients with first detected AF. The present review highlights on the conventional and novel risk factors of development and progression of AF.

Gender differences in electrophysiological characteristics of idiopathic ventricular tachycardia originating from right ventricular outflow tract

It has become increasingly apparent in recent years that there are important differences of many cardiovascular disorders including ventricular tachycardias in men and women. Nevertheless, so far just few studies have addressed possible gender differences in electrophysiological characteristics of idiopathic ventricular tachycardia from right ventricular outflow tract (RVOT-VT), other than epidemiological ones. This study explored possible gender differences in electrophysiological characteristics and catheter ablation outcome in RVOT-VT patients. Ninety-three patients (mean age 38.7+/-15.5 years, 30 males) with idiopathic RVOT-VT were enrolled and analyzed in our study. Male patients had longer QRS width (99.9+/-19.4 ms vs. 88.4+/-20.7 ms, p=0.02). Female patients had lower right ventricular mean voltage (3.0+/-0.7 mV vs. 3.7+/-0.9 mV, p=0.03), and more low voltage zone over the right ventricular outflow tract free wall (27.0 % vs. 6.7 %, p=0.02). Eighty-one patients passed catheter ablation (23 males). The acute success rate, repeated catheter ablation rate and VT recurrence rate were similar in both genders. The present study provides evidence of the gender differences in electrophysiological findings in patients with idiopathic RVOT-VT. Studies on gender-specific differences in arrhythmia could lead to a better understanding of its mechanism(s) and provide valuable information for the development of optimal treatment strategies.

Atrial fibrillation in the elderly: a review

Atrial fibrillation (AF) is common in the elderly population. Elderly patients with AF are often asymptomatic, may have atypical presentation or may present with heart failure or thromboembolic complications. The optimal management strategy of AF in the elderly population is challenging. We present an overview of AF in elderly patients, in particular addressing the pros and cons of various management strategies, and provide a practical approach within the guidelines.

Evaluation of right atrium-to-right ventricle diameter ratio on computed tomography pulmonary angiography: Prediction of adverse outcome and 30-day mortality

OBJECTIVE

The aim of this study was to examine the association between right atrium (RA) and right ventricle (RV) diameters on computed tomography (CT) pulmonary angiography in response to acute pulmonary embolism (APE), in addition to 30-day mortality and adverse outcomes in patients with APE.

METHODS

This retrospective study was accepted by the institutional ethics committee. From January 2013 to March 2014, 79 hospitalized adult patients with symptomatic APE were included. Inclusion criteria were a CT pulmonary angiography positive for pulmonary embolism, availability of patient records, and a follow-up of at least 30 days. A review of patient records and images was performed. The maximum diameters of the heart chambers were measured on a reconstructed four-chamber heart view, and the vascular obstruction index was calculated on CT pulmonary angiography.

RESULTS

There were statistically significant relationships in both the RA/RV diameter ratio and the RV/left ventricle (LV) diameter ratio between patients with and without adverse outcomes (p<0.001 and 0.002, respectively). Furthermore, there was a statistically significant difference in the RA/RV diameter ratio, but not in the RV/LV diameter ratio, between those with and without 30-day mortality (p=0.002 and 0.148, respectively).

CONCLUSIONS

Measurement of the RA/RV diameter ratio may be an alternative and useful method for predicting 30-day mortality and adverse outcome in patients with APE.

P-wave morphology is associated with echocardiographic response to cardiac resynchronization therapy in MADIT-CRT patients

BACKGROUND

In this study we hypothesized that signs of atypical atrial activation would be associated with cardiac resynchronization therapy (CRT) response in patients with mildly symptomatic heart failure (CHF), left ventricular dysfunction, and wide QRS complex.

METHODS

Patients included in the CRT-D arm in MADIT-CRT were studied (n = 892). Unfiltered signal-averaged P waves were analyzed to determine orthogonal P-wave morphology (typical morphologies were predefined as having positive signals in Leads X and Y and a negative or negative-positive signal in Lead Z. All other patterns were classified as atypical). The association between P-wave morphology and data on echocardiographic response at 1 year was analyzed.

RESULTS

Atypical P-wave morphology was found in 21% (n = 186) of the patients at baseline. Patients with atypical P-wave morphology were more often female (31% vs. 24%, P = 0.025), had lower BMI (28 ± 5 kg/m(2) vs. 29 ± 5 kg/m(2) , P = 0.008), had more ischemic CHF (60% vs. 52%, P = 0.026) and had smaller left atrial volumes (90 ± 20 mL vs. 94 ± 22 mL, P = 0.034). Atypical P-wave morphology at baseline was associated with superior response to CRT at 1 year with a larger reduction in left ventricular end-diastolic volume (-23 ± 12% vs. -20 ± 11%, P = 0.009), left ventricular end-systolic volume (-36 ± 16% vs. -31 ± 16%, P = 0.006), and left atrial volume (-31 ± 12% vs. -27 ± 12%, P = 0.005), with a slightly larger absolute increase in left ventricular ejection fraction (LVEF) (12 ± 5% vs. 11 ± 5%, P = 0.009). These associations were found to be independent of traditional predictors.

CONCLUSION

The presence of atypical P-wave morphology recorded is independently associated with a favorable echocardiographic cardiac remodeling response to CRT.

The clinical profile and pathophysiology of atrial fibrillation: relationships among clinical features, epidemiology, and mechanisms

Atrial fibrillation (AF) is the most common arrhythmia (estimated lifetime risk, 22%-26%). The aim of this article is to review the clinical epidemiological features of AF and to relate them to underlying mechanisms. Long-established risk factors for AF include aging, male sex, hypertension, valve disease, left ventricular dysfunction, obesity, and alcohol consumption. Emerging risk factors include prehypertension, increased pulse pressure, obstructive sleep apnea, high-level physical training, diastolic dysfunction, predisposing gene variants, hypertrophic cardiomyopathy, and congenital heart disease. Potential risk factors are coronary artery disease, kidney disease, systemic inflammation, pericardial fat, and tobacco use. AF has substantial population health consequences, including impaired quality of life, increased hospitalization rates, stroke occurrence, and increased medical costs. The pathophysiology of AF centers around 4 general types of disturbances that promote ectopic firing and reentrant mechanisms, and include the following: (1) ion channel dysfunction, (2) Ca(2+)-handling abnormalities, (3) structural remodeling, and (4) autonomic neural dysregulation. Aging, hypertension, valve disease, heart failure, myocardial infarction, obesity, smoking, diabetes mellitus, thyroid dysfunction, and endurance exercise training all cause structural remodeling. Heart failure and prior atrial infarction also cause Ca(2+)-handling abnormalities that lead to focal ectopic firing via delayed afterdepolarizations/triggered activity. Neural dysregulation is central to atrial arrhythmogenesis associated with endurance exercise training and occlusive coronary artery disease. Monogenic causes of AF typically promote the arrhythmia via ion channel dysfunction, but the mechanisms of the more common polygenic risk factors are still poorly understood and under intense investigation. Better recognition of the clinical epidemiology of AF, as well as an improved appreciation of the underlying mechanisms, is needed to develop improved methods for AF prevention and management.

Mechanisms of arrhythmias and conduction disorders in older adults

Aging is associated with an increased prevalence of cardiac arrhythmias, which contribute to higher morbidity and mortality in the elderly. The frequency of cardiac arrhythmias, particularly atrial fibrillation and ventricular tachyarrhythmia, is projected to increase as the population ages, greatly impacting health care resource utilization. Several clinical factors associated with the risk of arrhythmias have been identified in the population, yet the molecular bases for the increased predisposition to arrhythmogenesis in the elderly are not fully understood. This review highlights the epidemiology of cardiac dysrhythmias, changes in cardiac structure and function associated with aging, and the basis for arrhythmogenesis in the elderly.

Atrial electromechanical coupling interval and P-wave dispersion in healthy elderly

BACKGROUND AND AIMS

The aim of our study was to investigate the potential effect of natural aging on atrial fibrillation (AF) by means of electrocardiographic P-wave analysis and measurement of the transthoracic echocardiographic electromechanical coupling interval (EMC).

METHODS

The study comprised 25 healthy individuals aged ≥65 years (group 1) and 25 control subjects <65 years (group 2). The difference between maximum (Pmax) and minimum (Pmin) P-wave durations on 12-lead electrocardiography were defined as P-wave dispersion (PD). Intra- and inter-atrial EMC were measured by tissue Doppler imaging.

RESULTS

Pmax (107.2 ± 3.58 msec vs 100.0 ± 3.56 msec, p<0.001) and PD (43.6 ± 4.98 msec vs 36.5 ± 3.56 msec, p<0.001) were significantly higher in group 1 than in group 2. Left atrial EMC [24.6 (15.20) vs 13.3 (4.50), p<0.001] and inter-atrial EMC [43.2 (16.05) vs 33.3 (4.75), p<0.001] were significantly delayed in group 1 compared with group 2. There was a significant correlation between left atrial diameter, PD, Pmax, left atrial EMC, and inter-atrial EMC.

CONCLUSION

Aging is correlated with increased left atrial size and impaired diastolic relaxation, which may contribute to a greater risk of AF in terms of prolonged PD and atrial EMC.

Importance of evaluating conduction block in radiofrequency ablation for atrial fibrillation

OBJECTIVE

Atrial fibrillation (AF) is the most frequently diagnosed cardiac arrhythmia. Anti-arrhythmic drugs may be used to suppress ectopic foci and interrupt reentry circuits, but are often insufficient to treat recurrent AF and have a number of adverse effects. Alternative therapies, such as catheter and surgical ablation, have been explored. This investigation examines the importance of assessing exit block when performing surgical ablation during beating-heart treatment of AF.

METHODS

This was an evaluation of pooled data from multicenter prospective results obtained in AF patients who received ablation with a new, irrigated, vacuum-integrated device that creates linear lesions during beating-heart/open-chest or minimally invasive, port-access procedures. Electrocardiogram or Holter data were collected intra-operatively and at 1, 3, 6, and 12 months. Outcomes were also evaluated for patients who were or 'were not' tested for exit block following the ablation procedure.

RESULTS

A total of 93 patients were treated (61 open-chest surgeries, 32 port-access procedures). There were no device-related complications and no operative mortality. At 341 days' average follow-up, 71/86 (83%) patients were free from AF, 66/86 (77%) were in sinus rhythm, and 60/86 (70%) were free from AF and off Class I and III anti-arrhythmic drugs (AADs). At 12 months, 23/23 (100%) patients with exit block confirmed were AF free compared with 13/21 (62%) patients with exit block not tested (p≤0.01, Fisher's exact test); 20/23 (87%) were in sinus rhythm compared with 12/21 (57%) patients with exit block not tested (p≤0.05, Fisher's exact test); and 20/23 (87%) were AF free without Class I and III AADs compared with 10/21 (48%) patients with exit block not tested (p≤0.01, Fisher's exact test). Both open-chest and port-access procedures yielded decreases in left-atrial size from baseline to 6 months' follow-up. Patients undergoing port-access procedures also observed an increase in left-ventricular ejection fraction, which was also significant at 6 months.

CONCLUSION

Patients in whom exit block was confirmed following an ablation procedure were more likely to have successful clinical outcomes. Since testing for exit block must be performed on a beating heart, total epicardial beating-heart ablation may provide an important treatment for AF, providing intra-operative feedback indicative of long-term outcomes.

Gender differences of electrophysiological characteristics in focal atrial tachycardia

Gender differences of supraventricular tachycardias such as atrioventricular nodal re-entry, atrioventricular re-entry, and atrial fibrillation have been reported. There is little evidence of the effect of gender on focal atrial tachycardia (FAT). The study consisted of 298 patients who were referred to this institution for radiofrequency catheter ablation of FAT from October 1992 to April 2008 and included 156 men (52%) and 142 women (48%). Men were significantly older than women (57.9 +/- 18.2 vs 47.2 +/- 19.0 years old, p <0.001). Women had more associated arrhythmias (17.0% vs 28.9%, p = 0.01), mostly due to an increased incidence of atrioventricular nodal re-entrant tachycardia. Men had more cardiovascular co-morbidities (19.9% vs 9.9%, p = 0.02), a mechanism of increased automaticity (19.1% vs 8.1%, p = 0.01), and nonparoxysmal tachycardia (14.7% vs 4.4%, p = 0.01). No gender differences were noted among FAT number, left atrial involvement, shortest tachycardia cycle, success rate of catheter ablation, or recurrence rate of FAT. Mean duration of follow-up was 63.2 +/- 47.5 months. Premenopausal women had a lesser cardiovascular co-morbidity (15.3% vs 4.3%, p = 0.04) and a greater incidence of a mechanism of increased automaticity (13.4% vs 2.9%, p = 0.03). In conclusion, gender differences in electrophysiologic characteristics were noted in FAT.

Prevalence of atrial fibrillation in community-dwelling Japanese aged 40 years or older in Japan: analysis of 41,436 non-employee residents in Kurashiki-city

BACKGROUND

A community-based study was conducted to estimate the prevalence of atrial fibrillation (AF) in Japanese adults aged >or=40 years in Kurashiki-city and to examine associated risk factors.

METHODS AND RESULTS

Adult residents (>or=40-year-old) were examined in the Kurashiki-city Annual Medical Survey (KAMS) provided by the Kurashiki-city Public Health Center from May to December 2006. KAMS consisted of medical interviews, physical examination, blood testing and electrocardiography to assess the presence of AF. All participants were divided into AF and non-AF groups, their clinical characteristics compared, and the risk factors associated with AF investigated. Of 246,246 adult residents, 41,436 (age: 72.1+/-11.3 years; 13,963 men) underwent the KAMS. Estimated overall prevalence of AF was 1.6%. Multivariate analysis demonstrated that AF was independently associated with cardiac disease (odds ratio (OR), 9.00; 95% confidence interval (CI), 7.65-10.6; p<0.001), chronic kidney disease (OR, 1.76; 95%CI, 1.49-2.07; p<0.001), male sex (OR, 1.59; 95%CI, 1.34-1.85; p<0.001), and diabetes mellitus (OR, 1.46; 95%CI, 1.20-1.78; p<0.001). Hypercholesterolemia was highly associated with the absence of AF (OR, 0.54; 95%CI, 0.45-0.64, p<0.001).

CONCLUSIONS

Prevalence of AF in Japan is approximately 1.6%, lower than that in Western populations. Male sex, and cardiac and chronic kidney diseases are associated with the presence of AF.

Atrial cell action potential parameter fitting using genetic algorithms

Understanding of the considerable variation in action potential (AP) shape throughout the heart is necessary to explain normal and pathological cardiac function. Existing mathematical models reproduce typical APs, but not all measured APs, as fitting the sets of non-linear equations is a tedious process. The study describes the integration of a pre-existing mathematical model of an atrial cell AP with a genetic algorithm to provide an automated tool to generate APs for arbitrary cells by fitting ionic channel conductances. Using the Nygren model as the base, the technique was first verified by starting with random values and fitting the Nygren model to itself with an error of only 0.03%. The Courtemanche model, which has a different morphology from that of the Nygren model, was successfully fitted. The AP duration restitution curve generated by the fit matched that of the target model very well. Finally, experimentally recorded APs were reproduced. To match AP duration restitution behaviour properly, it was necessary simultaneously to fit over several stimulation frequencies. Also, fitting of the upstroke was better if the stimulating current pulse replicated that found in situ as opposed to a rectangular pulse. In conclusion, the modelled parameters were successfully able to reproduce any given atrial AP. This tool can be useful for determining parameters in new AP models, reproducing specific APs, as well as determining the locus of drug action by examining changes in conductance values.