Algoritmos de Detecçao de Taquicardias Incorporado a Desfibriladores Automáticos Implantáveis. 1) Desfibriladores Monocamerais

Diversos algoritmos foram incorporados aos cardioversores-desfibriladores automáticos implantáveis (CDIs) para identificar os distúrbios do ritmo ventricular e, sobretudo, para os diferenciar de taquicardias supraventriculares que nao necessitam terapia. Esses benefícios também sao encontrados nos CDIs bicamerais que têm como benefício a detecçao atrial acoplada à detecçao do ventrículo. O objetivo dos algoritmos é de identificar todas as arritmias ventriculares (sensibilidade de 100%), para que sejam tratadas corretamente. Devem ainda evitar erros de identificaçao de arritmias supraventriculares (especificidade máxima). Infelizmente, nao é possível alcançar 100% de sensibilidade e especificidade. Além disso, todo aumento da especificidade será acompanhado por uma diminuiçao da sensibilidade. Essa diminuiçao de especificidade pode conduzir a falha na detecçao dos distúrbios do ritmo ventricular, e como conseqüência, isto é pior que o tratamento inadequado de uma taquicardia sinusal ou supraventricular

Algoritmos de Detecçao de Taquicardias Incorporado a Desfibriladores Automáticos Implantáveis. 1) Desfibriladores Monocamerais

Diversos algoritmos foram incorporados aos cardioversores-desfibriladores automáticos implantáveis (CDIs) para identificar os distúrbios do ritmo ventricular e, sobretudo, para os diferenciar de taquicardias supraventriculares que nao necessitam terapia. Esses benefícios também sao encontrados nos CDIs bicamerais que têm como benefício a detecçao atrial acoplada à detecçao do ventrículo. O objetivo dos algoritmos é de identificar todas as arritmias ventriculares (sensibilidade de 100%), para que sejam tratadas corretamente. Devem ainda evitar erros de identificaçao de arritmias supraventriculares (especificidade máxima). Infelizmente, nao é possível alcançar 100% de sensibilidade e especificidade. Além disso, todo aumento da especificidade será acompanhado por uma diminuiçao da sensibilidade. Essa diminuiçao de especificidade pode conduzir a falha na detecçao dos distúrbios do ritmo ventricular, e como conseqüência, isto é pior que o tratamento inadequado de uma taquicardia sinusal ou supraventricular

Post-operative atrial fibrillation: a maze of mechanisms

Post-operative atrial fibrillation (POAF) is one of the most frequent complications of cardiac surgery and an important predictor of patient morbidity as well as of prolonged hospitalization. It significantly increases costs for hospitalization. Insights into the pathophysiological factors causing POAF have been provided by both experimental and clinical investigations and show that POAF is ‘multi-factorial’. Facilitating factors in the mechanism of the arrhythmia can be classified as acute factors caused by the surgical intervention and chronic factors related to structural heart disease and ageing of the heart. Furthermore, some proarrhythmic mechanisms specifically occur in the setting of POAF. For example, inflammation and beta-adrenergic activation have been shown to play a prominent role in POAF, while these mechanisms are less important in non-surgical AF. More recently, it has been shown that atrial fibrosis and the presence of an electrophysiological substrate capable of maintaining AF also promote the arrhythmia, indicating that POAF has some proarrhythmic mechanisms in common with other forms of AF. The clinical setting of POAF offers numerous opportunities to study its mechanisms. During cardiac surgery, biopsies can be taken and detailed electrophysiological measurements can be performed. Furthermore, the specific time course of POAF, with the delayed onset and the transient character of the arrhythmia, also provides important insight into its mechanisms

Arrhythmias in Dilated Cardiomyopathy: Diagnosis and Treatment

In patients with dilated cardiomyopathy (DCM), it is possible to find a broad range of bradyrhythmias and tachyarrhythmias. Bradyrhythmias and supraventricular arrhythmias can frequently occur in some familial forms such as lamin A/C mutations. Nonsustained ventricular arrhythmias (VA) are observed in about 40% of patients with DCM, but their prognostic role is not clear, and conflicting data have been published in the last 30 years. Multiple mechanisms can explain atrial and ventricular tachyarrhythmias in DCM. Reentry is associated with slow conduction across surviving muscle bundles within regions of interstitial fibrosis, but other mechanisms can be involved, as nonuniform anisotropy of impulse propagation, ion channel dysfunction, and reduced gap junction function

H015 Initial Heart rate variability could help to identify the patients with myotonic dystrophy at risk of death

Heart rate variability evaluation (HRV) is used to evaluate the prognosis in heart diseases at risk of cardiac mortality. Myotonic dystrophy (MD) is complicated by cardiac involvement. The purpose of the study was to evaluate the prognostic value of HRV determination for the stratification risk in MD.Methods60 asymptomatic patients, 26 men, 34 women, mean age 39±12 years at inclusion, had a MD. The studies were performed at inclusion and repeated 4±2.5 years later. Recording of 24 hour Holter monitoring and measurement of HRV in the time domain was calculated every 5minutes (Elatec system); standard deviation of mean RR intervals (SDNN) was determined. Left ventricular ejection fraction (LVEF) was evaluated by 2D echocardiography.Results1 – General changes of studies: LVEF tended to decrease (63±8, 61.5±19.5 %) (p< 0.06). Mean values of SDNN did not change between the first inclusion (129±41 ms) and the last study (134±51ms).2 – Modifications of studies according to initial data: LVEF was normal in 56 patients at inclusion. And decreased at second study 64±6 %, 61.5±7 % (p<0.01). LVEF was less than 50 % in 4 patients at inclusion and did not change at second study (43.5±7 vs 45±8 %). At inclusion, SDNN was normal in 42 patients (>100 ms) (147±35 ms) and was 148±52 at second study (NS); SDNN was < 100 ms in 2 of them at second study. SDNN was decreased (50 to 100 ms) in 17 patients at inclusion (mean 85±9 ms) and tended to increase at second study (97±34 ms) (NS).3 – Follow-up: Initial SDNN could be predictive of the mortality: four patients died from heart and respiratory failure ; Three had an initial SDNN<100ms (3/17 ; 18 %) and the last one had a normal SDNN (1/42 ; 2 %) (p<0.08).ConclusionsThe modifications of HRV during the follow-up were not useful for the prediction of the adverse events in myotonic dystrophy, although LVEF decreased with time. However, a relatively low HRV at the first evaluation could be predictive of increasing mortality from 2 to 18 %