T-wave alternans: desempenho clínico, limitações, metodologias de análise

Reconhecer com precisão indivíduos com maior risco imediato de morte súbita cardíaca (MSC) ainda é uma questão em aberto. A natureza fortuita dos eventos cardiovasculares agudos não parece se adequar ao conhecido modelo de indução de taquicardia/fibrilação ventricular por um gatilho em sincronia a um substrato arritmogênico estático. Quanto ao mecanismo da MSC, uma instabilidade elétrica dinâmica explicaria melhor a raridade da associação simultânea de um gatilho certo a um substrato cardíaco apropriado. Diversos estudos tentaram medir essa instabilidade elétrica cardíaca (ou um equivalente válido) em uma sequência de batimentos cardíacos no ECG. Dentre os mecanismos possíveis podemos citar o prolongamento do QT, dispersão do QT, potenciais tardios, alternância de onda T ou T-wave alternans (TWA), e turbulência da frequência cardíaca. Este artigo se atém em particular ao papel da TWA no panorama atual da estratificação de risco cardíaco. Os achados sobre TWA ainda são heterogêneos, variando de um desempenho prognóstico muito bom até um quase nulo, dependendo da população clínica observada e protocolo clínico usado. Para preencher as atuais lacunas no conhecimento sobre TWA, profissionais médicos e pesquisadores devem explorar melhor as características técnicas das diversas tecnologias disponíveis para a avaliação de TWA e atentar ao fato de que os valores de TWA respondem a diversos outros fatores, além de medicamentos. Informações sobre mecanismos celulares e subcelulares da TWA estão fora do escopo deste artigo, mas são referenciados alguns dos principais trabalhos sobre este tópico, com o intuito de auxiliar no entendimento dos conceitos e fatos cobertos neste artigo.

beta-Blocker Therapy and Mortality of Patients With Chagas Cardiomyopathy A Subanalysis of the REMADHE Prospective Trial

Background-Peculiar aspects of Chagas cardiomyopathy raise concerns about efficacy and safety of sympathetic blockade. We studied the influence of beta-blockers in patients with Chagas cardiomyopathy. Methods and Results-We examined REMADHE trial and grouped patients according to etiology (Chagas versus non-Chagas) and beta-blocker therapy. Primary end point was all-cause mortality or heart transplantation. Altogether 456 patients were studied; 27 (5.9%) were submitted to heart transplantation and 202 (44.3%) died. Chagas etiology was present in 68 (14.9%) patients; they had lower body mass index (24.1+/-4.1 versus 26.3+/-5.1, P=0.001), smaller end-diastolic left ventricle diameter (6.7+/-1.0 mm versus 7.0+/-0.9 mm, P=0.001), smaller proportion of beta-blocker therapy (35.8% versus 68%, P<0.001), and higher proportion of spironolactone therapy (74.6% versus 57.8%, P=0.003). Twenty-four (35.8%) patients with Chagas disease were under beta-blocker therapy and had lower serum sodium (136.6+/-3.1 versus 138.4+/-3.1 mEqs, P=0.05) and lower body mass index (22.5+/-3.3 versus 24.9+/-4.3, P=0.03) compared with those who received beta-blockers. Survival was lower in patients with Chagas heart disease as compared with other etiologies. When only patients under beta-blockers were considered, the survival of patients with Chagas disease was similar to that of other etiologies. The survival of patients with beta-blockers was higher than that of patients without beta-blockers. In Cox regression model, left ventricle end-diastolic diameter (hazard ratio, 1.78; CI, 1.15 to 2.76; P=0.009) and beta-blockers (hazard ratio, 0.37; CI, 0.14 to 0.97; P=0.044) were associated with better survival. Conclusions-Our study suggests that beta-blockers may have beneficial effects on survival of patients with heart failure and Chagas heart disease and warrants further investigation in a prospective, randomized trial.

Positive impact of omega-3 fatty acid supplementation in a dog with drug-resistant epilepsy: A case study

Epilepsy is the most common neurological disorder in both dogs and humans. Although the pharmacological options for treatment of epilepsies have increased. it has been reported that two-thirds of dogs with epilepsy are refractory to antiepileptic drug therapy. To our knowledge, there are no experimental Studies in the literature that show an effect of omega-3 supplementation oil epilepsy in dogs. Our case study describes the effectiveness of daily intake of a moderate amount of fish oil in a case of canine epilepsy. (C) 2009 Elsevier Inc. All rights reserved.

What are the similarities between stress, sudden cardiac death in Gallus gallus and sudden unexpected death in people with epilepsy

Individuals with epilepsy are at higher risk of sudden unexpected death in epilepsy (SUDEP), responsible for 7.5% to 17% of all deaths in epilepsy. Many factors are current associated with SUDEP and possible effect of stress and cardiac arrhythmia are still not clear. Sudden death syndrome (SDS) in chickens is a disease characterized by an acute death of well-nourished and seeming healthy Gallus gallus after abrupt and brief flapping of their wings, similar to an epileptic seizure, with an incidence estimated as 0.5 to 5% in broiler chickens. A variety of nutritional and environmental factors have been included: but the exactly etiology of SDS is unknown. Studies had suggested that the hearts of broiler chickens are considerably more susceptible to arrhythmias and stress may induce ventricular arrhythmia and thus, sudden cardiac death. In this way, SDS in Gallus gallus could be an interesting model to study SUDEP.

Citrus Sudden Death Is Transmitted by Graft-Inoculation and Natural Transmission Is Prevented by Individual Insect-Proof Cages

Citrus sudden death (CSD) transmission was studied by graft-inoculation and under natural conditions. Young sweet orange trees on Rangpur rootstock were used as indicator plants. They were examined regularly for one or two characteristic markers of CSD: (i) presence of a yellow-stained layer of thickened bark on the Rangpur rootstock, and (ii) infection with the CSD-associated marafivirus. Based on these two markers, transmission of CSD was obtained, not only when budwood for graft-inoculation was taken from symptomatic, sweet orange trees on Rangpur, but also when the budwood sources were asymptomatic sweet orange trees on Cleopatra mandarin, indicating that the latter trees are symptomless carriers of the CSD agent. For natural transmission, 80 young indicator plants were planted within a citrus plot severely affected by CSD. Individual insect-proof cages were built around 40 indicator plants, and the other 40 indicator plants remained uncaged. Only two of the 40 caged indicator plants were affected by CSD, whereas 17 uncaged indicator plants showed CSD symptoms and were infected with the marafivirus. An additional 12 uncaged indicator plants became severely affected with citrus variegated chlorosis and were removed. These results strongly suggest that under natural conditions, CSD is transmitted by an aerial vector, such as an insect, and that the cages protected the trees against infection by the vector.

Unexplained sudden death in patients on the waiting list for renal transplantation

Background. The incidence of unexplained sudden death (SD) and the factors involved in its occurrence in patients with chronic kidney disease are not well known. Methods. We investigated the incidence and the role of co-morbidities in unexplained SD in 1139 haemodialysis patients on the renal transplant waiting list. Results. Forty-four patients died from SD of undetermined causes (20% of all deaths; 3.9 deaths/1000 patients per year), while 178 died from other causes and 917 survived. SD patients were older and likely to have diabetes, hypertension, past/present cardiovascular disease, higher left ventricular mass index, and lower ejection fraction. Multivariate analysis showed that cardiovascular disease of any type was the only independent predictor of SD (P = 0.0001, HR = 2.13, 95% CI 1.46-3.22). Alterations closely associated with ischaemic heart disease like angina, previous myocardial infarction and altered myocardial scan were not independent predictors of SD. The incidence of unexplained SD in these haemodialysis patients is high and probably a consequence of pre-existing cardiovascular disease. Conclusions. Factors influencing SD in dialysis patients are not substantially different from factors in the general population. The role played by ischaemic heart disease in this context needs further evaluation.

Sudden unexpected death in an adolescent with epilepsy: All roads lead to the heart?

The incidence of sudden unexpected death in epilepsy (SUDEP) has been estimated from 0.5-1.4/1,000 person-years in people with treated epilepsy, and 9/1,000 person-years in candidates for epilepsy surgery. Potential risk factors for SUDEP include: age, early onset of epilepsy, duration of epilepsy, uncontrolled seizures, seizure type and winter temperatures. The arrythmogenic side-effect of antiepileptic drugs and seizures may increase the risk of SUDEP. In this report, we describe a patient with prolonged post-ictal tachycardia in EEG video recordings with a typical case of SUDEP: a 16-year-old boy with medically intractable complex partial seizures. Magnetic resonance imaging revealed left mesial temporal sclerosis. During non-invasive video-EEG monitoring, the patient presented a post-ictal heart rate increased for five hours. Two months after video-EEG, he died from SUDEP during a tonic-clonic secondary generalized seizure. The possibility of cardiac involvement in the pathogenesis of SUDEP has been suggested by many studies. Evaluation of this patient with EEG-video monitoring, including measurement of heart rate, contributed to an identification of ictal tachycardia that may have played a role in the SUDEP. Premature mortality seems to be increased in patients with epilepsy, and cardiac abnormalities may be a possible cause of SUDEP. (Cardiol J 2011; 18, 2: 194-196)

Pediatric epilepsy surgery and sudden unexpected death epilepsy: the contribution of a Brazilian epilepsy surgery program

Individuals with epilepsy are at higher risk of death than those from the general population, and sudden unexpected death in epilepsy (SUDEP) is the most important direct epilepsy-related cause of death. Epilepsies in the pediatric group are more frequently associated with known potentially risk factors for SUDEP, and a treatment resulting in an improved seizure control may also decrease mortality. The aim of this study is to identify the incidence of SUDEP in a group of operated-on children and adolescents. We analyzed 267 patients up to 18 years old, with medically intractable epilepsy submitted to surgery. We considered the age at surgery, the seizure type, the pathological findings, and the seizure outcome. Data were prospectively collected, according to the protocols of our institution`s ethics committee. The percentage of boys was 58.05. A good outcome was achieved in 72.6% of the cases and a bad outcome in 27.4%. Nine patients died during follow-up, six from clinical complications, and one from SUDEP. All patients who died during the long-term follow-up had persisted with refractory postoperative seizures. The patient who died from SUDEP died during a generalized tonic-clonic seizure. Of the patients, 72.6% had excellent postoperative outcome, and one patient died of SUDEP. All patients who died had had disabling seizures` persistence. The surgical treatment of epilepsy in children and adolescents is an efficient therapy for the medically intractable symptomatic epilepsies and also for the reduction of mortality and SUDEP risks.

Subclinical hyperthyroidism and sudden unexpected death in epilepsy

Epilepsy is the most common serious neurological condition and sudden unexpected death in epilepsy (SUDEP) is the most important direct epilepsy-related cause of death. Information concerning risk factors for SUDEP is conflicting, but high seizure frequency is a potential risk factor. Additionally, potential pathomechanisms for SUDEP are unknown, but it is very probable that cardiac arrhythmias during and between seizures or transmission of epileptic activity to the heart via the autonomic nervous system potentially play a role. In parallel, several studies have shown a link between hormones and epilepsy. However, exact knowledge regarding the association of thyroid hormones and epilepsy is lacking. As subclinical hyperthyroidism has been linked with increased risk of cardiovascular disease, we propose in this paper that SUDEP, at least in some cases, could be related with subclinical thyroid dysfunction. (C) 2009 Elsevier Ltd. All rights reserved.

Benefits of sunlight: Vitamin D deficiency might increase the risk of sudden unexpected death in epilepsy

Epilepsy is the most common serious neurological condition and sudden unexpected death in epilepsy (SUDEP) is the most important direct epilepsy-related cause of death. information concerning risk factors for SUDEP is conflicting, but high seizure frequency is a potential risk factor. Additionally, potential pathomechanisms for SUDEP are unknown, but it is very probable that cardiac arrhythmias during and between seizures or transmission of epileptic activity to the heart via the autonomic nervous system potentially play a role. In parallel, studies have shown a link between vitamin D dysfunction and epilepsy. Moreover, several evidences in the literature suggest an association between low vitamin D and seizures, indicating the possibility of anticonvulsant properties of this hormone. Quite interesting, a growing body of data suggests that low vitamin D levels may adversely affect cardiovascular health, directly associated with death from heart failure and sudden cardiac death. In view of the above findings, our research group focused in this review article that SUDEP, at least in some cases, could be related with low vitamin D levels. (C) 2009 Elsevier Ltd. All rights reserved.

Does the lunar phase have an effect on sudden unexpected death in epilepsy?

The incidence of sudden unexpected death in epilepsy (SUDEP) in Our epilepsy unit over an 8-year period was analyzed to determine a possible association between phase of the moon and SUDEP. Analysis revealed that the number of SUDEPs was highest in full moon (70%), followed by waxing moon (20%) and new moon (10%). No SUDEPs Occurred during the waning cycle. These preliminary findings suggest that the full moon appears to correlate with SUDEP. (C) 2008 Elsevier Inc. All rights reserved.

Thyroid gland and cerebella lesions: New risk factors for sudden cardiac death in schizophrenia?

People with schizophrenia show a two to threefold increased risk to die prematurely than those without schizophrenia. Patients` life style, suicide, premature development of cardiovascular disease, high prevalence of metabolic syndrome and sudden cardiac death are well-known causes of the excess mortality. The exact pathophysiological cause of sudden death in schizophrenia is unknown, but it is likely that cardiac arrhythmia and respiratory abnormalities play potential role. Some antipsychotics may be associated with cardiovascular adverse events (e.g., QT interval prolongation) and lesions in specific brain regions, such as cerebella may be associated with respiratory abnormalities, suggesting that metabolic and brain dysfunction could lead to sudden cardiac death in patients with schizophrenia. However, exact knowledge regarding the association of these findings and schizophrenia is lacking. As subclinical hyperthyroidism has been linked with increased risk of cardiovascular disease and cerebella progressive atrophy has been observed in patients with schizophrenia, we propose in this paper that subclinical thyroid dysfunction and cerebella volume loss could be considered as new risk factor for sudden cardiac death in schizophrenia. (C) 2010 Elsevier Ltd. All rights reserved.

Could sudden death syndrome (SDS) in chickens (Gallus gallus) be a valid animal model for sudden unexpected death in epilepsy (SUDEP)?

Epilepsy is the most common serious neurological disorder and approximately 1% of the population worldwide has epilepsy. Moreover, sudden unexpected death in epilepsy (SUDEP) is the most important direct epilepsy-related cause of death. Information concerning fisk factors for SUDEP is conflicting, but potential risk factors include: young age, early onset of epilepsy, duration of epilepsy, uncontrolled seizures, seizure frequency, AED number and winter temperatures. Additionally, the cause of SUDEP is still unknown; however, the most commonly suggested mechanisms are cardiac abnormalities during and between seizures. Similarly, sudden death syndrome (SDS) is a disease characterized by an acute death of well-nourished and seeming healthy Gallus gallus after abrupt and brief flapping of their wings and incidence of SDS these animals has recently increased worldwide. Moreover, the exactly cause of SDS in Gallus gallus is unknown, but is very probable that cardiac abnormalities play a potential role. Due the similarities between SUDEP and SDS and as Gallus gallus behavioral manifestation during SDS phenomenon is close of a tonic-clonic seizure, in this paper we suggest that epilepsy could be a new possible causal factor for SDS. (C) 2009 Elsevier Ltd. All rights reserved.

Universality of sudden death of entanglement

We present a constructive argument to demonstrate the universality of the sudden death of entanglement in the case of two non-interacting qubits, each of which generically coupled to independent Markovian environments at zero temperature. Conditions for the occurrence of the abrupt disappearance of entanglement are determined and, most importantly, rigourously shown to be almost always satisfied: Dynamical models for which the sudden death of entanglement does not occur are seen to form a highly idealized zero-measure subset within the set of all possible quantum dynamics.

Entanglement degree measure and a criterion for sudden death as a phase transition in bipartite systems

We propose a method to compute the entanglement degree E of bipartite systems having dimension 2 x 2 and demonstrate that the partial transposition of density matrix, the Peres criterion, arise as a consequence Of Our method. Differently from other existing measures of entanglement, the one presented here makes possible the derivation of a criterion to verify if an arbitrary bipartite entanglement will suffers sudden death (SD) based only on the initial-state parameters. Our method also makes possible to characterize the SD as a dynamical quantum phase transition, with order parameter epsilon. having a universal critical exponent -1/2. (C) 2009 Elsevier Inc. All rights reserved.