A fibrilação atrial (FA) é um dos tipos mais freqüentes de arritmia cardíaca e é caracterizada principalmente pela aleatoriedade na ocorrência dos batimentos do coração. Sob este aspecto, a fibrilação atrial pode ser considerada um processo estocástico e por isso tem sido freqüentemente modelada através de cadeias de Markov. Seguindo trabalhos anteriores sobre este tópico, este trabalho modela seqüências temporais de batimentos cardíacos como um processo markoviano de três estados para detecção automática de FA. O modelo foi treinado e desenvolvido através dos sinais da base de dados MIT-BIH. Outro método mais consolidado na detecção de FA, denominado \"Razão RR\", também foi implementado, com o objetivo de comparar os resultados do Modelo Markoviano. A avaliação de desempenho para ambos os métodos implementados fo i realizada medindo-se a sensibilidade (Se) e o valor preditivo positivo (+P) para a detecção de FA. Estes dois métodos - Modelos Markovianos e \"Razão RR\" - tiveram seus coeficientes e limiares otimizados com o objetivo de maximizar, ao mesmo tempo, os valores de Se e +P. Após a otimização, ambos os métodos foram testados com uma nova base de dados, independente da base de dados de desenvolvimento. Os resultados obtidos com a base de dados de teste foram Se=84,940% e +P=81,579%, consolidando os Modelos Markoviano s para detecção de batimentos aleatórios. / Atrial fibrillation (AF) is one of the most common cardiac arrhythmia and it is mainly characterized by the presence of random RR intervals. In this way, atrial fibrillation has been studied as a stochastic process and it has been often modeled through Markov chains. Following previous studies on this subject, this work models time sequences of heartbeats as a three states Markov process for AF automatic detection. The model was trained and developed using signals from MIT-BIH database. Another consolidated method for AF detection, called \"RR Ratios\", was also applied to compare Markov Model\'s results. The performance evaluation of both methods was measured through sensitivity (Se) and positive predictive (+P) for AF detection. These two methods - Markov Model and \"RR Ratio\" - had their coefficients and thresholds optimized in order to maximize the values of Se and +P at the same time. After optimization, both methods were tested with another database, independent of development database. The obtained results were Se = 84,940% and +P = 81,579%, consolidating Markov Models for detecting random heartbeats.

BACKGROUND: Atrial fibrillation (AF) is the most common cardiac arrhythmia, and previous studies have focused on the epidemiology, mechanisms and risk factors for this global disease (Ryder and Benjamin 1999). Various studies have examined the mechanism, epidemiology, and risk factors for AF. One of the most common triggers for AF is believed to be premature atrial contractions (PACs) usually arising from the pulmonary veins of the left atrium, but the relationship between AF and premature ventricular complexes (PVCs) is not well understood. Studies investigating the triggers of premature beats in both the atria and ventricles are similar, so it is possible that treatment for one arrhythmia may affect the incidence of another. It is hypothesized that due to commonly shared mechanisms of triggered activity or automaticity between PACs and PVCs, and shared risk factors, that patients with AF undergoing treatment with catheter ablation may be prone to develop PVCs. OBJECTIVE: To investigate the incidence of clinically detected PVCs among patients undergoing catheter ablation for AF, and clinical predictors of PVC development in this cohort of patients. We also aim to evaluate if incident PVC detection is associated with recurrent AF following AF ablation in a cohort of 317 patients receiving treatment at a single academic medical center. METHODS: A total of 375 patients undergoing AF ablation from 2009-2012 were reviewed, and patients that underwent repeat ablations were excluded, yielding 317 patients for analysis. T-tests and Chi-squared analyses were used in univariate analyses to test for significance between characteristics of AF patients who did and did not develop PVCs. Kaplan-Meier analyses and Cox proportional hazards models were used for univariate and multivariate survival analyses, respectively, to assess the risks of incident PVC development. RESULTS: Of 317 patients with AF undergoing pulmonary vein isolation (PVI) ablation, 36.3% developed clinically detectable PVCs following ablation. A history of clinically evident PVC prior to catheter ablation for AF was associated with an 80% increase in risk of incident PVC development (HR=1.83, 95% CI 1.02-3.26, p=0.041). Additionally, a history of prior angioplasty, stent, or percutaneous coronary intervention (PCI) was associated with a 73% decreased risk of incident PVCs (HR=0.27, 95% CI 0.08-0.88, p=0.03). In patients with a history of PVC prior to ablation, or who developed PVCs after ablation, there was no significant difference in the risk of AF recurrence (HR=1.01, 95% CI 0.70-1.46, p=0.96; and HR=1.09, 95% CI 0.78-1.53, p=0.60, respectively). CONCLUSIONS: Over 1 in 3 patients develop clinically detected PVCs following catheter ablation. Predictors of incident PVC development include a history of PVC, whereas a history of angioplasty, stent, or PCI was associated with less incident PVC development. Furthermore, there was no significant association between both a history of PVC or incident PVC and risk of recurrent AF following ablation.

In a systematic review and random effects meta-analysis, we evaluated whether obesity is associated with postoperative atrial fibrillation (POAF) in patients undergoing cardiac surgery. Eighteen observational studies that excluded patients with preoperative AF were selected until December 2011 (n=36,147). Obese patients had a modest higher risk of POAF in comparison to non-obese (OR 1.12, 95%CI 1.04-1.21, p=0.002). The association between obesity and POAF did not vary substantially by type of cardiac surgery, study design or year of publication. POAF was significantly associated with higher risk of stroke, respiratory failure, and operative mortality. / Revisión por pares

Atrial Fibrillation (AF) is rare amongst young people whilst epidemic in the elderly. Whilst much is known about the pathophysiology of AF, the mechanisms underlying the vulnerability to AF amongst older people in incompletely understood. Young (< 18 months, first quintile of life) and old (> 8 years, last quintile of life) Welsh mountain sheep were used to investigate changes in atrial electrophysiology with age. Old sheep were more vulnerable to induced AF than young sheep. On the surface ECG, p-wave duration increased with age suggesting increasing atrial size. The corrected sinus node recovery time increased with age, suggesting deteriorating sinus node function. These findings confirmed the validity of sheep as a model for human ageing. In isolated atrial myocytes, action potentials (APs) were recorded using the perforated patch clamp technique. AP duration increased with age, and an increase in AP amplitude was also seen at the lowest stimulation rates. Right atrial AP durations were prolonged compared to those from left atrial myocytes, and the inter-atrial difference was similar between old and young. However, when right atrial monophasic APs were recorded from anaesthetised sheep in vivo, no difference in AP duration was seen between age groups. Alternans occurred at lower stimulation rates in old compared to young myocytes and was of greater magnitude. These age-related differences were present in isolated myocytes and in vivo. Alternans mechanisms were explored by simultaneously recording APs and intracellular calcium concentration. Atrial alternans was driven by alternans of Ca2+ cycling at low stimulation rates. However, despite disabling Ca2+ cycling using thapsigargin, alternans could still be elicited from myocytes during rapid stimulation. Right atrial conduction velocity (CV) was assessed in vivo and found to increase with age. A key determinant of CV, the Na+ current INa was investigated using the whole cell patch clamp technique. INa increased with age in left atrial myocytes and recovered faster from inactivation. Protein expression was investigated using Western blotting. Expression of the Na+ channel α-subunit did not change with age. The gap junction protein Cx43 was expressed less in older subjects, but Cx40 expression was similar. This work has cast light on several aspects of atrial electrophysiology in which the effects of age have not been thoroughly investigated. The longer cellular APs seen with age decrease the wavelength of potential re-entrant circuits which could be seen as protective against AF. However, AP prolongation is also associated with afterdepolarisations which could serve to trigger AF. The increase in alternans behaviour may set the stage for wavebreak, leading to re-entrant circuit formation. The increase in CV was surprising and might be seen as protective against AF as it increases arrhythmia wavelength, and is likely to be caused by the increased INa.

Sickle cell trait (SCT), sickle cell disease’s carrier status, is a common genetic variant found in many people of African, South Asian, Middle Eastern and Mediterranean descent. While overall considered a benign carrier status, it has been associated with an increased risk of several diseases, including exertional rhabdomyolysis (ER), and chronic kidney disease. While epidemiological evidence links SCT with ER, the actual pathophysiological mechanism less understood. Additionally, while there is an increased prevalence of atrial fibrillation (AF) documented in people with sickle cell disease, studies in individuals with SCT are lacking. The objectives of this thesis are twofold: The first chapter is a literature review of studies to examine the physiological mechanisms linking SCT and exertional rhabdomyolysis. The second chapter is original research into the associations of SCT with AF. The first chapter reviews studies that identify aggravating factors that may promote ER. It then reviews observed pathophysiological changes in people with SCT that may increase the risk of ER. It summarizes studies that assess mitigating factors that decrease the risk of ER. It then presents a postulated pathway of mechanisms that associate SCT with ER. The second chapter uses data from African-American participants in the REasons for Geographic and Racial Differences in Stroke (REGARDS) study to assess the association of SCT with prevalent AF (by electrocardiogram or medical history) using logistic regression models adjusting for age, sex, income, education, history of stroke, myocardial infarction, diabetes, hypertension, and chronic kidney disease. In 10,409 participants with baseline ECG data and genotyping, 778 (7.5%) had SCT and 811 (7.8%) had prevalent AF. After adjusting for age, sex, education and income, SCT was associated with AF, OR 1.32 (95% CI 1.03-1.70). SCT remained associated with prevalent AF after adjusting for potential factors on the causal pathway such as hypertension and chronic kidney disease suggesting alternate mechanisms for the increased risk. SCT was associated with a higher prevalence of AF and a non-significantly higher incident AF over a 9.2 year period independent of AF risk factors.

Thesis (M.S.)--University of Florida, 2003. / Title from title page of source document. Includes vita. Includes bibliographical references.

Die Ergebnisse dieser Arbeit lassen vermuten, dass die Connexin43 Anordnung an der der Zellmembran humaner Herzmuskelzellen pharmakologisch beeinflussbar ist. Es ist bekannt, dass sich Connexin43 an der polaren und lateralen Zellmembran beim Vorhofflimmern und Sinusrhythmus unterschiedlich anordnet. Während beim Sinusrhythmuspatienten Connexin43 kaum an der lateralen Zellmembran zu finden ist, zeigt sich beim Vorhofflimmern vor allem an der lateralen Zellmembran eine verstärkte Connexin43 Anhäufung. Neben dem Rhythmustyp hat auch β-Adrenozeptorstimulation Einfluss auf die Connexin43 Expression. Aus diesem Grund untersucht die vorliegende Arbeit den Einfluss einer pharmakologischen Blockade der β-Adrenozeptoren durch Betablocker. Dafür wurden 38 die untersuchten Patienten anhand ihres Rhythmustyps, ihrer kardialen Begleiterkrankung und ihrer Pharmakotherapie (Betablocker: ja/nein) unterteilt und neben deren klinischen Daten ihre intraoperativ gewonnenen Herzohrbiopsien immunhistochemisch gefärbt und anschließend ausgewertet. Dabei zeigte sich, dass es zum einen zu einer unterschiedlichen Anordnung von Connexin43 bei den beiden Rhythmustypen kommt. Während beim Sinusrhythmus Connexin43 vor allem polar an der Zellmembran zu finden ist, ist es beim Vorhofflimmern vor allem an den lateralen Zellgrenzen zu finden. Betablockade geht hierbei vor allem beim Patienten mit Vorhofflimmern und Mitralklappenvitium mit einer Reduktion der Lateralisierung und einem positiven Effekt auf die Polarisierung einher.

名古屋大学博士学位論文 学位の種類 : 博士(医学)(課程) 学位授与年月日:平成24年3月26日 櫛山泰規氏の博士論文として提出された

Patienter med förmaksflimmer är en grupp vars symtom ofta underskattas. Symtomen påminner om de som uppkommer vid en hjärtinfarkt med bröstsmärta, hjärtklappning, andnöd och trötthet. Syftet med studien var att belysa hur det kan vara att leva med förmaksflimmer. En litteraturstudie utfördes där vetenskapliga artiklar analyserades och sammanställdes. Resultatet visade att patienternas livskvalitet var kraftigt nedsatt och även anhöriga påverkades. En ökning av ångest och depression sågs vid uppföljning sex och tolv månader efter fastställd diagnos. Informationen och omvårdnaden var bristfällig och ett kunskapsbehov identifierades. Evidensbaserade riktlinjer för omvårdnad och information har utarbetats för denna patientgrupp, men resultatet visade att det inte fanns några utarbetade vårdprogram att tillgå i Sverige. Baskunskaper i omvårdnaden saknades hos personalen som vårdade patienterna. Här ses ett stort behov av omvårdnadsforskning inom området. Ett ökat samarbete mellan forskare och kliniskt verksamma sjuksköterskor behövs för att nya rön ska kunna implementeras i den dagliga vården. / Patients with atrial fibrillation is a group whose symptoms are often underestimated. Symptoms are similar to those arising from a heart attack with chest pain, palpitations, shortness of breath and fatigue. The purpose of this study was to illustrate how it can be to live with atrial fibrillation. A literature review was conducted in which scientific articles were analyzed and summarized. The results showed that patients' quality of life was dramatically reduced and even relatives were affected. An increase in anxiety and depression were seen at follow-up six and twelve months after the established diagnosis. The information and care was poor and the knowledge needs were identified. Evidence-based guidelines for care and information has been prepared for this group of patients, but the result showed that there were no prepared programs of care available in Sweden. Basic knowledge of nursing was missing the nursing staff who cared for the patients. Seen here is a great need for nursing research in the field. Increased cooperation between academics and clinical nurses is needed so that new findings could be implemented in the daily care.

published_or_final_version / Medicine / Master / Master of Research in Medicine