Abstract Background Dental anesthetic management in implantable cardioverter defibrillator (ICD) recipients with cardiac channelopathies (CCh) can be challenging due to the potential risk of life-threatening arrhythmias and appropriate ICD therapies during procedural time. Objectives The present study assessed the hypothesis that the use of local dental anesthesia with 2% lidocaine with 1:100,000 epinephrine or without a vasoconstrictor can be safe in selected ICD and CCh patients, not resulting in life-threatening events (LTE). Methods Restorative dental treatment under local dental anesthesia was made in two sessions, with a wash-out period of 7 days (cross-over trial), conducting with a 28h - Holter monitoring, and 12-lead electrocardiography, digital sphygmomanometry, and anxiety scale assessments in 3 time periods. Statistical analysis carried out the paired Student’s t test and the Wilcoxon signed-rank test. In all cases, a significance level of 5% was adopted. All patients were in stable condition with no recent events before dental care. Results Twenty-four consecutive procedures were performed in 12 patients (9 women, 3 men) with CCh and ICD: 7 (58.3%) had long QT syndrome (LQTS), 4 (33.3%) Brugada syndrome (BrS), and 1 (8.3%) Catecholaminergic polymorphic ventricular tachycardia (CPVT). Holter analysis showed no increased heart rate (HR) or sustained arrhythmias. Blood pressure (BP), electrocardiographic changes and anxiety measurement showed no statistically significant differences. No LTE occurred during dental treatment, regardless of the type of anesthesia. Conclusion Lidocaine administration, with or without epinephrine, can be safely used in selected CCh-ICD patients without LTE. These preliminary findings need to be confirmed in a larger population with ICD and CCh. (ICD (CCh lifethreatening life threatening 2 1100,000 1100000 100,000 100 000 1:100,00 . (LTE) sessions washout wash crossover cross over trial, trial , trial) h monitoring 12lead lead electrocardiography sphygmomanometry periods Students Student s signedrank signed rank cases 5 adopted care Twentyfour Twenty four 9 ( women men 58.3% 583 58 (58.3% LQTS, LQTS (LQTS) 33.3% 333 33 (33.3% BrS, BrS (BrS) 8.3% 83 8 (8.3% CPVT. CPVT (CPVT) HR (HR BP, BP (BP) differences administration CChICD 1100 1100,00 110000 100000 100,00 10 00 1:100,0 (LTE 58.3 (58.3 (LQTS 33.3 (33.3 (BrS 8.3 (8.3 (CPVT (BP 110 1100,0 11000 10000 100,0 0 1:100, 58. (58. 33. (33. 8. (8. 11 1100, 1000 100, 1:100 (58 (33 (8 1:10 (5 (3 1:1 1:

Resumo Fundamento: A morte súbita cardíaca (MSC), decorrente de arritmias ventriculares, é a principal complicação da cardiomiopatia hipertrófica (CMH). A microalternância da onda T (MAOT) está associada à ocorrência de arritmias ventriculares em diversas cardiopatias, mas seu papel na CMH permanece incerto. Objetivo: Avaliar associação da MAOT com a ocorrência de MSC ou arritmias ventriculares malignas em pacientes com CMH. Método: Pacientes com diagnóstico de CMH e classe funcional I-II (NYHA) foram selecionados de forma consecutiva. No início do seguimento os participantes realizaram a avaliação da MAOT pela metodologia da média móvel modificada no teste de esforço. Os resultados foram classificados em alterado ou normal. O desfecho foi composto por MSC, fibrilação ventricular, taquicardia ventricular sustentada (TVS) e terapia apropriada do cardioversor desfibrilador implantável (CDI). O nível de significância estatística foi de 5%. Resultados: Um total de 132 pacientes (idade média de 39,5±12,6 anos) foram incluídos, com tempo de seguimento médio de 9,5 anos. A MAOT foi alterada em 74 (56%) participantes e normal em 58 (44%). Durante o seguimento, nove (6,8%) desfechos ocorreram, com prevalência de 1,0%/ano, sendo seis casos de MSC, dois choques apropriados do CDI e um episódio de TVS. MAOT alterada foi associada à taquicardia ventricular não sustentada no Holter (p=0,016), espessura septal≥30 mm (p<0,001) e resposta inadequada da pressão arterial ao esforço (p=0,046). Cinco pacientes (7%) e quatro pacientes (7%) com MAOT alterada e normal, respectivamente, apresentaram desfecho primário [OR=0,85(IC95%: 0,21–3,35, p=0,83)]. Curvas de eventos de Kaplan-Meir não apresentaram diferenças entre MAOT normal e alterada. Conclusão: A MAOT alterada não foi associada à ocorrência de MSC ou arritmias ventriculares potencialmente fatais em pacientes com CMH, e a baixa taxa desses eventos em um seguimento em longo prazo sugere o bom prognóstico dessa cardiopatia. Fundamento , (MSC) . (CMH) (MAOT cardiopatias incerto Objetivo Método III I II NYHA (NYHA consecutiva TVS (TVS CDI. (CDI) 5 5% Resultados 13 idade 395126 39 12 6 39,5±12, anos incluídos 95 9 9, 7 56% 56 (56% 44%. 44 44% (44%) 6,8% 68 8 (6,8% ocorreram 10ano ano 1 0 1,0%/ano p=0,016, p0016 p p=0,016 016 (p=0,016) septal30 septal 30 septal≥3 p<0,001 p0001 001 (p<0,001 p=0,046. p0046 p=0,046 046 (p=0,046) 7% (7% respectivamente OR=0,85IC95% OR085IC95 ORIC OR=0,85 IC95% OR 85 IC95 IC [OR=0,85(IC95% 021335 21 3 35 0,21–3,35 p=0,83. p083 p=0,83 83 p=0,83)] KaplanMeir Kaplan Meir Conclusão cardiopatia (MSC (CMH (CDI 39512 39,5±12 (56 4 (44% 6,8 (6,8 p001 p=0,01 01 (p=0,016 septal3 septal≥ p<0,00 p000 00 (p<0,00 p004 p=0,04 04 (p=0,046 (7 85IC95 OR=0,85IC95 OR085IC9 OR085 OR=0,8 IC9 [OR=0,85(IC95 02133 2 0,21–3,3 p08 p=0,8 p=0,83) 3951 39,5±1 (5 (44 6, (6, p00 p=0,0 (p=0,01 p<0,0 (p<0,0 (p=0,04 ( 85IC9 OR=0,85IC9 OR085IC OR08 OR=0, [OR=0,85(IC9 0213 0,21–3, p0 p=0, 395 39,5± (4 (6 (p=0,0 p<0, (p<0, 85IC OR=0,85IC OR0 OR=0 [OR=0,85(IC 021 0,21–3 p=0 39,5 (p=0, p<0 (p<0 OR= 02 0,21– p= 39, (p=0 p< (p< 0,21 (p= (p 0,2 0,

Abstract Background: Sudden cardiac death (SCD) resulting from ventricular arrhythmia is the main complication of hypertrophic cardiomyopathy (HCM). Microvolt T-wave alternans (MTWA) is associated with the occurrence of ventricular arrhythmias in several heart diseases, but its role in HCM remains uncertain. Objective: To evaluate the association of MTWA with the occurrence of SCD or potentially fatal ventricular arrhythmias in HCM patients in a long-term follow-up. Methods: Patients diagnosed with HCM and NYHA functional class I-II were consecutively selected. At the beginning of the follow-up, the participants performed the MTWA evaluation using the modified moving average during the stress test. The results were classified as altered or normal. The composite endpoint of SCD, ventricular fibrillation, sustained ventricular tachycardia (SVT) or appropriate implantable cardiac defibrillation (ICD) therapy was assessed. The level of significance was set at 5%. Results: A total of 132 patients (mean age of 39.5 ± 12.6 years) were recruited and followed for a mean of 9.5 years. The MTWA test was altered in 74 (56%) participants and normal in 58 (44%). Nine events (6.8%) occurred during the follow-up, with a prevalence of 1.0%/year – six SCDs, two appropriate ICD shocks and one episode of (SVT). Altered MTWA was associated with non-sustained ventricular tachycardia on Holter (p = 0.016), septal thickness ≥30 mm (p < 0.001) and inadequate blood pressure response to effort (p = 0.046). Five patients with altered MTWA (7%) and four patients with normal MTWA (7%) had the primary outcome [OR = 0.85 (95% CI: 0.21 - 3.35, p=0.83)]. Kaplan-Meir event curves showed no differences between normal and altered MTWA. Conclusion: Altered MTWA was not associated with the occurrence of SCD or potentially fatal ventricular arrhythmias in HCM patients, and the low rate of these events during long-term follow-up suggests the good prognosis of this heart disease. Background (SCD HCM. . (HCM) Twave T wave (MTWA diseases uncertain Objective longterm long term followup. followup follow up. up Methods III I II selected followup, up, fibrillation SVT (SVT (ICD assessed 5 5% Results 13 395 39 39. 126 12 6 12. years 95 9 9. 7 56% 56 (56% 44%. 44 44% (44%) 6.8% 68 8 (6.8% 10year year 1 0 SCDs SVT. nonsustained non p 0.016, 0016 0.016 , 016 0.016) 30 ≥3 0.001 0001 001 0.046. 0046 0.046 046 0.046) 7% (7% OR 085 85 0.8 95% (95 CI 021 21 0.2 335 3 35 3.35 p=0.83. p083 p=0.83 83 p=0.83)] KaplanMeir Kaplan Meir Conclusion disease (HCM (56 4 (44% 6.8 (6.8 0.01 01 ≥ 0.00 000 00 004 0.04 04 (7 08 0. (9 02 2 33 3.3 p08 p=0.8 p=0.83) (5 (44 6. (6. 0.0 ( 3. p0 p=0. (4 (6 p=0 p=

Resumo Fundamento O período neonatal é marcado por muitas alterações importantes no sistema cardiovascular, principalmente na primeira semana de vida. Diferentemente da população adulta, estudos sobre dados de eletrocardiograma (ECG) no período neonatal são escassos. Este é o primeiro estudo a descrever alterações eletrocardiográficas em uma coorte de recém-nascidos com ecocardiogramas normais. Objetivos Analisar padrões eletrocardiográficos de uma população de recém-nascidos a termo, sem anomalias morfológicas ou funcionais cardíacas, e comparar os resultados com a literatura. Métodos Neste estudo observacional, ecocardiogramas e resultados de ECG de 94 neonatos divididos em três grupos etários (até 24 horas, entre 25 e 72 horas, e entre 73 e 168 horas de vida) foram avaliados e comparados com aqueles descritos por Davignon et al. Um valor de p < 0,05 foi considerado estatisticamente significativo. Resultados Diferenças significativas na direção da onda T foram detectadas nas derivações V1 (p= 0,04), V2 (p= 0,02), V3 (p= 0,008) e V4 (p= 0,005). Houve diferenças entre nossos resultados e a literatura atual na maioria dos parâmetros. Conclusão Recém-nascidos a termo com menos de 24 horas de vida apresentaram significativamente mais ondas T positivas que aqueles com mais horas de vida. Encontramos muitas diferenças nos parâmetros de ECG em comparação aos descritos por Davignon et al., particularmente nas amplitudes de P, Q, R, S, duração do QRS, R/S e R+S. Esses achados indicam a necessidade de mais estudos para uma interpretação definitiva do ECG em recém-nascidos.

Abstract Background The neonatal period is marked by major changes in the cardiovascular system, especially in the first week of life. Unlike the adult population, studies on electrocardiogram (ECG) data in the neonatal period are scarce. This is the first study to describe electrocardiographic changes in a cohort of newborns with normal echocardiograms. Objectives To analyze the electrocardiographic patterns of a population of full-term NB, without any cardiac morphological or functional anomalies, and compare the results with the literature. Methods In this observational study, echocardiograms and ECG results from 94 newborns divided in three age groups (up to 24 hours, between 25 and 72 hours, and between 73 and 168 hours of life) were evaluated and compared with those reported by Davignon et al. A p-value <0.05 was considered statistically significant. Results There were significant differences in T-wave direction in leads V1 (p= 0.04), V2 (p= 0.02), V3 (p= 0.008) and V4 (p= 0.005) between the three age groups. There were differences between our findings and the current literature in most of the parameters. Conclusion Term newborns within 24 hours of life showed significantly more positive T waves than older ones. Many differences from the Davignon’s ECG parameters were found, particularly in the P, Q, R, S amplitudes, QRS duration, R/S and R+S. These findings indicate that more studies are needed for a definitive interpretation of the ECG in newborns.

Resumo O eletrocardiograma (ECG) foi revigorado com o reconhecimento de alterações elétricas que ainda não haviam sido observadas de maneira definitiva. Nesse contexto, principalmente na definição dos substratos arritmogênicos, a associação do ECG com o vetorcardiograma (VCG) propiciou mais informações sobre os fenômenos elétricos cardíacos, possibilitando distinguir os casos potencialmente fatais dos benignos. A obtenção de um VCG ao mesmo tempo da realização do ECG trouxe um ganho muito importante para definir patologias extremamente sofisticadas, com alterações estruturais ou dinâmicas que envolvem canais e correntes iônicas, cujas funções são diminuídas ou exageradas em razão de mutações genéticas. Os aspectos clássicos da relação ECG/VCG no diagnóstico diferencial das áreas inativas, dos distúrbios de condução, das sobrecargas atriais e ventriculares e das associações entre esses distúrbios elétricos continuam vigentes e assertivos, e ficam mais claros quando vistos pelo binômio ECG/VCG. Além disso, a orientação espacial tridimensional das atividades atrial e ventricular cria uma ferramenta de observação muito mais completa do que o modo linear do ECG. A análise moderna do ECG e do respectivo VCG, obtidos simultaneamente pela técnica recente chamada de eletrovetorcardiograma (ECG/VCG), trouxe um ganho importante no diagnóstico diferencial de algumas patologias. Desse modo, são abordadas aqui as principais utilidades dessa análise na elucidação de diagnósticos importantes da atividade diária na clínica cardiológica.

Abstract The electrocardiogram (ECG) has been reinvigorated by the identification of electrical alterations that were not definitely clarified before. In this context, and mainly regarding the definition of arrhythmogenic substrates, the association of the ECG with the vectorcardiogram (VCG) has gathered much more information about the cardiac electrical phenomena, thus allowing us to differentiate potentially fatal cases from benign ones. Obtaining a VCG concomitantly with the performance of an ECG has led to a significant gain in the definition of extremely sophisticated pathologies, which function suffer some type of structural or dynamic alterations, involving either the reduction or enhancement of ionic channels and currents. The classic aspects of the ECG/VCG association in the differential diagnosis of myocardial infarctions, conduction disorders, atrial and ventricular hypertrophies, and the correlations between these electrical disorders are still valid and assertive. The association of these pathologies is further clarified when they are seen through the ECG/VCG dyad. The three-dimensional spatial orientation of both the atrial and the ventricular activity provides a far more complete observation tool than the ECG linear form. The modern analysis of the ECG and its respective VCG, simultaneously obtained by the recent technique called electro-vectorcardiogram (ECG/VCG), brought a significant gain for the differential diagnosis of some pathologies. Therefore, we illustrate how this type of analysis can elucidate some of the most important diagnoses found in our daily clinical practice as cardiologists.

OBJECTIVES: In athletes, isolated electrocardiogram high voltage criteria are widely used to evaluate left ventricular hypertrophy, but positive findings are thought to represent normal electrocardiogram alterations. However, which electrocardiogram criterion can best detect left ventricular hypertrophy in athletes of various sport modalities remains unknown. METHODS: Five electrocardiogram criteria used to detect left ventricular hypertrophy were tested in 180 male athletes grouped according to their sport modality: 67% low-static and high-dynamic components and 33% high-static and high-dynamic components of exercise. The following echocardiogram parameters are the gold standard for diagnosing left ventricular hypertrophy: left ventricular mass index ≥134 g.m-2, relative wall thickness ≥0.42 mm, left ventricular diastolic diameter index ≥32 mm.m-2, septum wall thickness ≥13 mm, and posterior wall thickness ≥13 mm. Results for the various criteria were compared using the kappa coefficient. Significance was established at p<0.05. RESULTS: Fifty athletes (28%) presented with left ventricular hypertrophy according to electrocardiogram findings, with the following sensitivities and specificities, respectively: 38-53% and 79-83% (Perugia), 22-40% and 89-91% (Cornell), 24-29% and 90% (Romhilt-Estes), 68-87% and 20-23% (Sokolow-Lyon), and 0% and 99% (Gubner). The Perugia and Cornell criteria had higher negative predictive values for the low-static and high-dynamic subgroup. Kappa coefficients were higher for Romhilt-Estes, Cornell and Perugia criteria than for Sokolow-Lyon and Gubner criteria. CONCLUSION: All five evaluated criteria are inadequate for detecting left ventricular hypertrophy, but the Perugia, Cornell and Romhilt-Estes criteria are useful for excluding its presence. The Perugia and Cornell criteria were more effective at excluding left ventricular hypertrophy in athletes involved in a sport modality with low-static and high-dynamic component predominance.

Resumo A terceira versão das diretrizes aborda tópicos recentemente descritos, como as doenças dos canais iônicos, alterações isquêmicas agudas, o eletrocardiograma dos atletas e análise da repolarização ventricular. Ela buscou rever critérios de sobrecargas, distúrbios de condução e análise de dados transmitidos via internet.

Abstract The third version of the guidelines covers recently described topics, such as ion channel diseases, acute ischemic changes, the electrocardiogram in athletes, and analysis of ventricular repolarization. It sought to revise the criteria for overloads, conduction disorders, and analysis of data for internet transmission.

Fundamento:Dados sobre sobrevida após uma síndrome coronariana aguda (SCA) são geralmente de curto prazo ou baseados em centros cardiológicos.Objetivo:Descrever a frequência de ocorrência de óbito em um ano no Estudo de Registro de Insuficiência Coronariana (ERICO), e seus preditores.Métodos:Foram analisados 964 participantes ERICO incluídos de fevereiro/2009 a dezembro/2012. O estado vital dos participantes foi obtido por telefone e fontes oficiais de óbito. A causa de morte foi determinada pelos certificados de óbito. Foi utilizado o teste log-rank para comparar probabilidades de sobrevivência. Construímos modelos de regressão de Cox, brutos e ajustados (para idade, sexo e subtipo de SCA), para estudar se o subtipo de SCA ou características de entrada no estudo foram preditores independentes de mortalidade.Resultados:Identificamos 110 óbitos (frequência de ocorrência de óbito, 12,0%). A idade (risco relativo [RR] em 10 anos = 2,04; intervalo de confiança de 95% [IC95%]=1,75-2,38), infarto do miocárdio sem elevação do segmento ST (RR = 3,82; IC95% = 2,21-6,60) ou infarto do miocárdio com elevação do segmento ST (RR = 2,59; IC95% = 1,38‑4,89) e diabetes (RR = 1,78; IC95% = 1,20-2,63) foram fatores de risco significativos para mortalidade geral em modelos ajustados. Encontramos resultados semelhantes para mortalidade cardiovascular. Diagnóstico prévio de doença arterial coronariana também foi um preditor independente de mortalidade geral (RR = 1,61; IC95% = 1,04-2,50), mas não de mortalidade cardiovascular.Conclusão:Encontramos uma frequência de ocorrência de óbito em um ano de 12,0% nesta amostra de pacientes pós-SCA de um hospital comunitário em São Paulo. Idade, subtipo de SCA e diabetes foram preditores independentes de pior sobrevida em um ano.

Background:Information about post-acute coronary syndrome (ACS) survival have been mostly short-term findings or based on specialized, cardiology referral centers.Objectives:To describe one-year case-fatality rates in the Strategy of Registry of Acute Coronary Syndrome (ERICO) cohort, and to study baseline characteristics as predictors.Methods:We analyzed data from 964 ERICO participants enrolled from February 2009 to December 2012. We assessed vital status by telephone contact and official death certificate searches. The cause of death was determined according to the official death certificates. We used log-rank tests to compare the probabilities of survival across subgroups. We built crude and adjusted (for age, sex and ACS subtype) Cox regression models to study if the ACS subtype or baseline characteristics were independent predictors of all-cause or cardiovascular mortality.Results:We identified 110 deaths in the cohort (case-fatality rate, 12.0%). Age [Hazard ratio (HR) = 2.04 per 10 year increase; 95% confidence interval (95%CI) = 1.75–2.38], non-ST elevation myocardial infarction (HR = 3.82 ; 95%CI = 2.21–6.60) or ST elevation myocardial infarction (HR = 2.59; 95%CI = 1.38–4.89) diagnoses, and diabetes (HR = 1.78; 95%CI = 1.20‑2.63) were significant risk factors for all-cause mortality in the adjusted models. We found similar results for cardiovascular mortality. A previous coronary artery disease diagnosis was also an independent predictor of all-cause mortality (HR = 1.61; 95%CI = 1.04–2.50), but not for cardiovascular mortality.Conclusion:We found an overall one-year mortality rate of 12.0% in a sample of post-ACS patients in a community, non-specialized hospital in São Paulo, Brazil. Age, ACS subtype, and diabetes were independent predictors of poor one‑year survival for overall and cardiovascular-related causes.

OBJECTIVES: Few studies have evaluated cardiac electrical activation dynamics after cardiac resynchronization therapy. Although this procedure reduces morbidity and mortality in heart failure patients, many approaches attempting to identify the responders have shown that 30% of patients do not attain clinical or functional improvement. This study sought to quantify and characterize the effect of resynchronization therapy on the ventricular electrical activation of patients using body surface potential mapping, a noninvasive tool. METHODS: This retrospective study included 91 resynchronization patients with a mean age of 61 years, left ventricle ejection fraction of 28%, mean QRS duration of 182 ms, and functional class III/IV (78%/22%); the patients underwent 87-lead body surface mapping with the resynchronization device on and off. Thirty-six patients were excluded. Body surface isochronal maps produced 87 maximal/mean global ventricular activation times with three regions identified. The regional activation times for right and left ventricles and their inter-regional right-to-left ventricle gradients were calculated from these results and analyzed. The Mann-Whitney U-test and Kruskall-Wallis test were used for comparisons, with the level of significance set at p≤0.05. RESULTS: During intrinsic rhythms, regional ventricular activation times were significantly different (54.5 ms vs. 95.9 ms in the right and left ventricle regions, respectively). Regarding cardiac resynchronization, the maximal global value was significantly reduced (138 ms to 131 ms), and a downward variation of 19.4% in regional-left and an upward variation of 44.8% in regional-right ventricular activation times resulted in a significantly reduced inter-regional gradient (43.8 ms to 17 ms). CONCLUSIONS: Body surface potential mapping in resynchronization patients yielded electrical ventricular activation times for two cardiac regions with significantly decreased global and regional-left values but significantly increased regional-right values, thus showing an attenuated inter-regional gradient after the cardiac resynchronization therapy.

OBJECTIVES: To describe the ERICO study (Strategy of Registry of Acute Coronary Syndrome), a prospective cohort to investigate the epidemiology of acute coronary syndrome. METHODS: The ERICO study, which is being performed at a secondary general hospital in São Paulo, Brazil, is enrolling consecutive acute coronary syndrome patients who are 35 years old or older. The sociodemographic information, medical assessments, treatment data and blood samples are collected at admission. After 30 days, the medical history is updated, and additional blood and urinary samples are collected. In addition, a retinography, carotid intima-media thickness, heart rate variability and pulse-wave velocity are performed. Questionnaires about food frequency, physical activity, sleep apnea and depression are also applied. At six months and annually after an acute event, information is collected by telephone. RESULTS: From February 2009 to September 2011, 738 patients with a diagnosis of an acute coronary syndrome were enrolled. Of these, 208 (28.2%) had ST-elevation myocardial infarction (STEMI), 288 (39.0%) had non-ST-elevation myocardial infarction (NSTEMI) and 242 (32.8%) had unstable angina (UA). The mean age was 62.7 years, 58.5% were men and 77.4% had 8 years or less of education. The most common cardiovascular risk factors were hypertension (76%) and sedentarism (73.4%). Only 29.2% had a prior history of coronary heart disease. Compared with the ST-elevation myocardial infarction subgroup, the unstable angina and non-ST-elevation myocardial infarction patients had higher frequencies of hypertension, diabetes, prior coronary heart disease (p<0.001) and dyslipidemia (p = 0.03). Smoking was more frequent in the ST-elevation myocardial infarction patients (p = 0.006). CONCLUSIONS: Compared with other hospital registries, our findings revealed a higher burden of CV risk factors and less frequent prior CHD history.

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.

Accurate recognition of individuals at higher immediate risk of sudden cardiac death (SCD) is still an open question. The fortuitous nature of acute cardiovascular events just does not seem to fit the well-known model of ventricular tachycardia/fibrillation induction in a static arrhythmogenic substrate by a synchronous trigger. On the mechanism of SCD, a dynamical electrical instability would better explain the rarity of the simultaneous association of a correct trigger and an appropriate cardiac substrate. Several studies have been conducted trying to measure this cardiac electrical instability (or any valid surrogate) in an ECG beat stream. Among the current possible candidates we can number QT prolongation, QT dispersion, late potentials, T-wave alternans (TWA), and heart rate turbulence. This article reviews the particular role of TWA in the current cardiac risk stratification scenario. TWA findings are still heterogeneous, ranging from very good to nearly null prognostic performance depending on the clinical population observed and clinical protocol in use. To fill the current gaps in the TWA base of knowledge, practitioners, and researchers should better explore the technical features of the several technologies available for TWA evaluation and pay greater attention to the fact that TWA values are responsive to several factors other than medications. Information about the cellular and subcellular mechanisms of TWA is outside the scope of this article, but the reader is referred to some of the good papers available on this topic whenever this extra information could help the understanding of the concepts and facts covered herein.

Reconocer con precisión individuos con mayor riesgo inmediato de muerte súbita cardíaca (MSC) aun es una cuestión en abierto. La naturaleza fortuita de los eventos cardiovasculares agudos no parece adecuarse al conocido modelo de inducción de taquicardia/fibrilación ventricular por un gatillo en sincronía con un substrato arritmogénico estático. En cuanto al mecanismo de la MSC, una inestabilidad eléctrica dinámica explicaría mejor la rareza de la asociación simultánea de un gatillo correcto a un substrato cardíaco apropiado. Diversos estudios trataron de medir esa inestabilidad eléctrica cardíaca (o un equivalente válido) en una secuencia de latidos cardíacos en el ECG. Entre los mecanismos posibles podemos citar la prolongación del QT, dispersión del QT, potenciales tardíos, alternancia de onda T o T-wave alternans (TWA), y turbulencia de la frecuencia cardíaca. Este artículo se atiene en particular al papel de la TWA en el panorama actual de la estratificación de riesgo cardíaco. Los hallazgos sobre TWA aun son heterogéneos, variando de un desempeño pronóstico muy bueno hasta uno casi nulo, dependiendo de la población clínica observada y protocolo clínico usado. Para llenar las actuales lagunas en el conocimiento sobre TWA, profesionales médicos e investigadores deben explotar mejor las características técnicas de las diversas tecnologías disponibles para la evaluación de TWA y estar atento al hecho de que los valores de TWA responden a otros diversos factores, además de medicamentos. Informaciones sobre mecanismos celulares y subcelulares de la TWA están fuera del objetivo de este artículo, pero son referenciados algunos de los principales trabajos sobre este tópico, con el propósito de auxiliar en la comprensión de los conceptos y hechos cubiertos en este artículo.