Relationship of the T-wave Tpeak-Tend interval with conduction system disorders in arterial hypertension / Relación del intervalo Tpico-Tfinal de la onda T con trastornos del sistema de conducción en hipertensión arterial

Abstract Purpose: The Tpeak-Tend interval of the T wave has emerged as a new electrocardiographic marker of increased transmural dispersion of ventricular repolarization. We aimed to determine the presence of cardiac conduction system disorders in patients with systemic arterial hypertension (SAH) who have altered Tpeak-Tend interval of the T wave. Methods: The 67 patients with SAH were divided into two groups. Those with prolonged (≥ 77 ms) Tpeak-Tend intervals, 21 (31%) patients were in the study group. Those with normal (< 77 ms) Tpeak-Tend intervals, 46 (69%) patients were in the control group. Alteration of ventricular repolarization manifested as a prolongation of the Tpeak-Tend interval was detected by computerized electrocardiographic analysis tools. Results: The median value of QRS complex duration was significantly wider in the study group as compared to the control group (110 ± 12 ms vs. 94 ± 8 ms p < 0.001). There was a significantly greater incidence of left anterior hemiblock in the study group (14% vs. 0% p < 0.04). The median value of the QTc interval was significantly greater in the study group (440 ± 26 vs. 422 ± 15 p < 0.01). There was a significantly greater incidence of patients with prolonged QTc interval in the study group (33% vs. 11% p < 0.02). The median value of the Tpeak-Tend interval was significantly greater in the study group (84 ± 5 ms vs. 65 ± 4 ms p < 0.001), as well as, the Tpeak-Tend/QTc ratio in the study group (0.19 ± 0.1 vs. 0.16 ± 0.1 p < 0.001). Conclusion: There is a significantly greater ventricular repolarization disorders and abnormalities of the cardiac conduction system in SAH patients who possess altered Tpeak-Tend interval of the T wave.

Resumen Objetivo: El intervalo Tpico-Tfinal de la onda T es un marcador electrocardiográfico de la dispersión transmural aumentada de la repolarización ventricular. Investigamos la presencia de trastornos del sistema de conducción cardíaca en pacientes con hipertensión arterial sistémica (HA) que poseen alterado el intervalo Tpico-Tfinal de la onda T. Métodos: Los 67 pacientes con HA fueron divididos en dos grupos. Aquellos con intervalos de Tpico-Tfinal prolongados (≥ 77 ms), 21 (31%) pacientes (grupo de estudio). Aquellos con intervalos normales (< 77 ms) Tpico-Tfinal, 46 (69%) pacientes (grupo control). Los intervalos Tpico-Tfinal fueron medidos por herramientas de análisis electrocardiográfico computarizado. Resultados: El valor mediano de la duración del complejo QRS fue significativamente más amplio en el grupo de estudio (110 ± 12 ms vs. 94 ± 8 ms p < 0.001). Hubo una incidencia significativamente mayor de hemibloqueo anterior izquierdo en el grupo de estudio (14% vs. 0% p < 0.04). El valor mediano del intervalo QTc fue significativamente mayor en el grupo de estudio (440 ± 26 vs. 422 ± 15 p < 0.01). Hubo una incidencia significativamente mayor de pacientes con intervalo QTc prolongado en el grupo de estudio (33% vs. 11% p < 0.02). El valor mediano del intervalo Tpico-Tfinal fue significativamente mayor en el grupo de estudio (84 ± 5 ms vs. 65 ± 4 ms p < 0.001), así como el cociente Tpico-Tfinal/QTc (0.19 ± 0.1 vs. 0.16 ± 0.1 p < 0.001). Conclusión: Existe una alteración de la repolarización ventricular significativamente mayor y anomalías del sistema de conducción cardíaca en pacientes con HA que poseen alteración del intervalo Tpico-Tfinal de la onda T.

Sedative and electrocardiographic effects of low dose dexmedetomidine in healthy cats / Efeitos sedativos e eletrocardiográficos da baixa dose de dexmedetomidina em gatos saudáveis

In feline veterinary practice sedation is often needed to perform diagnostic or minimally invasive procedures, minimize stress, and facilitate handling. The mortality rate of cats undergoing sedation is significantly higher than dogs, so it is fundamental that the sedatives provide good cardiovascular stability. Dexmedetomidine (DEX) is an α2-adrenergic receptor agonist utilized in cats to provide sedation and analgesia, although studies have been utilized high doses, and markedly hemodynamic impairments were reported. The aim of this study was to prospectively investigate how the sedative and electrocardiographic effects of a low dose of DEX performing in cats. Eleven healthy cats were recruited; baseline sedative score, systolic arterial pressure, electrocardiography, and vasovagal tonus index (VVTI) were assessed, and repeated after ten minutes of DEX 5μg/kg intramuscularly (IM). A smooth sedation was noticed, and emesis and sialorrhea were common adverse effects, observed on average seven minutes after IM injection. Furthermore, electrocardiographic effects of a low dose of DEX mainly include decreases on heart rate, and increases on T-wave amplitude. The augmentation on VVTI and appearance of respiratory sinus arrhythmia, as well as sinus bradycardia in some cats, suggesting that DEX enhances parasympathetic tonus in healthy cats, and therefore will be best avoid in patients at risk for bradycardia.(AU)

Na rotina clínica da medicina veterinária felina a sedação é frequentemente requerida para realização de procedimentos diagnósticos ou minimamente invasivos, para minimizar o estresse e facilitar o manuseio dos pacientes. A taxa de mortalidade de gatos submetidos à sedação é mais elevada do que em cães, por esse motivo, é fundamental que os sedativos confiram estabilidade hemodinâmica. A dexmedetomidina (DEX) é um α2-agonista utilizado em felinos para promover sedação e analgesia, porém os estudos têm utilizado doses elevadas, e com isso prejuízos hemodinâmicos importantes foram relatados. O objetivo desta investigação foi avaliar os efeitos sedativos e eletrocardiográficos da baixa dose de DEX em gatos. Para tal, onze felinos saudáveis foram recrutados, foram obtidos valores basais para escore de sedação, pressão arterial sistólica e eletrocardiografia, além do índice de tônus vaso vagal (ITVV). Após dez minutos da aplicação intramuscular (IM) de DEX 5μg/kg todos os exames foram repetidos. Após a DEX, sedação suave foi detectada, e a êmese e sialorreia foram efeitos adversos comuns, observados em média 7 minutos após a injeção IM. Ademais, os principais efeitos eletrocardiográficos foram redução na frequência cardíaca e aumento na amplitude da onda T. O ITVV mais elevado e surgimento de arritmia sinusal respiratória, bem como bradicardia sinusal em alguns gatos, sugerem que a DEX eleva o tônus parassimpático, e por esse motivo deve ser utilizada com cautela em pacientes com predisposição à bradicardia.(AU)

Early T-wave inversion in anterior leads predict patency of the anterior descending artery in ST-segment elevation myocardial infarction / La onda T invertida temprana en derivaciones anteriores predice permeabilidad de la arteria descendente anterior en infarto agudo de miocardio con elevación del segmento ST

Abstract: Introduction: T-wave inversion has always been considered as a natural progression sign of the non-perfunded myocardial infarction, however it is also seen after early succesful reperfusion via fibrinolysis or primary angioplasty; its role in predicting auto-reperfusion has not been established. Objective: Assess the patency of the infarct-related artery (IRA) in patients presenting with early (< 3 hours of symptoms onset) T-wave inversion (TWI) in leads with ST-segment elevation (STE) myocardial infarction (STEMI). Methods: We retrospectively analyzed 432 patients admitted at the emergency department of the National Cardiology Institute in Mexico City with a diagnosis of STEMI who arrived within three hours of symptoms onset and underwent primary percutaneous coronary intervention (p-PCI) from October 2005 to November 2015. Clinical data, electrocardiogram (ECG) and angiographic data were reviewed. The subjects were divided in two groups: those with TWI and those with positive T waves (PTW). Results: 386 (89.3%) patients presented with PTW and 46 (10.6%) with TWI. The presence of early TWI in anterior leads predicted patency of the anterior descending artery (LAD) (18 [69.2%] vs 41 [24%]; p < 0.001) but not in other arteries. Conclusions: The presence of early TWI in anterior leads with STE is associated with patency of the LAD. This relationship was not found in other infarct-related arteries.(AU)

Resumen: Introducción: La onda T invertida siempre se ha considerado como progresión natural de un infarto de miocardio no reperfundido, sin embargo, también se puede observar posterior a fibrinólisis o angioplastia primaria exitosas, su rol en predecir autorreperfusión no ha sido establecido. Objetivo: Valorar la permeabilidad de la arteria culpable del infarto (ACI) en pacientes que se presentan con onda T invertida (OTI) temprana (menos de tres horas de inicio de síntomas) en derivaciones con elevación del segmento ST (IAMCEST). Métodos: Se analizaron 432 pacientes de forma retrospectiva que fueron admitidos al Servicio de Urgencias del Instituto Nacional de Cardiología en la Ciudad de México con diagnóstico de IAMCEST dentro de las primeras tres horas de inicio de los síntomas y que fueran llevados a angioplastia primaria de octubre de 2005 a noviembre de 2015. Se revisaron datos clínicos, electrocardiogramas y angiografías coronarias. Los sujetos fueron divididos en dos grupos: aquéllos con OTI y aquéllos con onda T positiva (OTP). Resultados: Se presentaron 386 (89.3%) pacientes con OTP y 46 (10.6%) con OTI. La presencia de OTI temprana en derivaciones anteriores predijo permeabilidad de la descendente anterior (DA) (18 [69.2%] vs 41 [24%]; p < 0.001) pero no en las otras arterias. Conclusión: La presencia de OTI tempranas en derivaciones anteriores con elevación del segmento ST se asocia a permeabilidad de la DA. Este hallazgo no fue encontrado en otras arterias culpables de infarto.(AU)

Distorsión morfológica isquémica de la onda T en la centellografía de perfusión miocárdica con estrés vasodilatador / Ischemic T wave distortion associated with vasodilator-stress myocardial perfusion imaging

Los protocolos que utilizan vasodilatadores para inducir isquemia en la centellografía de perfusión miocárdica han demostrado una exactitud diagnóstica elevada e incidencia muy baja de complicaciones graves. Sin embargo, el significado fisiológico y valor diagnóstico de diversas alteraciones electrocardiográficas asociadas al estrés vasodilatador ha sido escasamente evaluado más allá del segmento ST. Describimos cinco pacientes que presentan distorsión morfológica de la onda T en derivaciones electrocardiográficas torácicas asociada a diversos defectos de perfusión, discutiendo los potenciales aportes de estos cambios al diagnóstico y cuantificación de la isquemia miocárdica en los estudios de imagen que utilizan estrés con vasodilatadores.

The protocols using vasodilators to induce ischemia on myocardial perfusion scintigraphy have shown a high diagnostic accuracy and a very low incidence of serious complications. However, the physiological significance and diagnostic value of various electrocardiographic changes associated with vasodilator stress has not been deeply evaluated beyond the ST-segment. Five clinical cases presenting morphological distortion of the T-wave in electrocardiographic chest leads associated with varying degrees of perfusion defects are described, discussing potential contributions of these changes to the diagnosis and quantification of myocardial ischemia in imaging studies using vasodilator stress.

Cuantificación de la dispersión espacial de la repolarización ventricular cardíaca a través del electrocardiograma de superficie / Quantification of Cardiac Ventricular Repolarization and its Spatial Dispersion through the Surface Electrocardiogram

La dispersión de la repolarización ventricular (DRV) está determinada esencialmente por la heterogeneidad de los potenciales de acción en diferentes regiones del miocardio. Con frecuencia el corazón responde a ciertos estados fisiopatológicos con la producción de un incremento de la DRV, fenómeno éste que puede devenir en una arritmia ventricular maligna y/o en la muerte súbita. Hace 25 años, con el objetivo de identificar a pacientes de riesgo cardíaco, se comenzó a cuantificar la DRV con diversos índices obtenidos por procesamiento computacional del electrocardiograma. Estos índices se basan en la detección de cambios en la duración o en la forma en la onda T en presencia de cardiopatías. En este trabajo se presenta una revisión de los índices de dispersión espacial y su potencialidad como herramienta de apoyo al diagnóstico de riesgo cardíaco.

The ventricular repolarization dispersion (VRD) is determined basically by the heterogeneity of the action potentials in different myocardial regions. Usually the heart responds to certain physiopathological states by producing a VRD increase, which may lead to a malignant ventricular arrhythmia and/or sudden death. For 25 years, the VRD has been quantified with several indexes obtained by computerprocessing the electrocardiogram, in order to identify cardiac- risk patients. These indexes are based on the detection of T wave changes in duration or form, in the presence of cardiopathies. A revision of the spatial dispersion indexes and their potential as supporting tool for the diagnosis of cardiac risk is presented in this work.

Memória cardíaca em pacientes com marcapasso artificial definitivo / Cardiac memory in patients with permanent cardiac pacemakers

Objetivo Analisar concordância ou diocordância entre a polaridade dos QRS artificialmente induzidos e das ondas T durante ritmo espontâneo (memória cardíaca), em pacientes com marcapasso (MP) artificial permamente. Métodos Trinta e cinco pacientes, obtendo-se seus ritmos espontâneos por inibição exter na ou reprogramação do gerador. Correlacionou-se a polaridade dos complexos QRS arti ficiais e das ondas T espontâneas, em busca de concordância ou discordância entre ativação e recuperação. Analisaram-se as melhores projeções do fenômeno concordante (memória cardíaca) e sua possível dependência de variáveis específicas, como o ritmo espontâneo e as características dos complexos QRS, tipo e modo de estimulação artificial e cronicidade do implante. Resultados Houve concordância entre QRS artificial e T espontânea em 5 ou mais derivações do PF em 77% e no pH em 50% dos casos. Nos pacientes com comando supraventricular, a concordância foi observada em 82% dos casos e em 50% nos com idioventricular. O fenômeno foi mais bem evidenciado quando o padrão de condução intraventricular era normal. Não houve correlação entre tipo, modo de estimulação e cronicidade do implante e o fenômeno da memória cardíaca. Esta foi mais bem evidenciada nas derivações aVF, D2, D3, V3 e V4. Conclusão O fenômeno da memória cardíaca é freqüente em paciente com MP artificial definitivo. A existência de um padrão normal de ativação ventricular, durante ritmo espontâneo, é o fator mais significativo para o seu aparecimento

Purpose To correlate the direction of QRS complex of paced beats and postpacing T wave, in patients with artificial pacemaker. Methods Thirty five patients with spontaneous rhythm obtained by chest wall stimulation or by programmability of the automatic interval. It was correlated in all patients, the direction forces of QRS complexes of paced beats and postpacing T waves in all 12 ECG leads. It was considered as a cardiac memory phenomenon when QRS complexes of paced beats and postpacing T waves had the same polarity. The phenomenon was correlated with the 12 ECG leads and with specific variables like spontaneous rhythm, QRS complex duration, type and modality of artificial stimulation and chronicity of the implant. Results The artificial QRS complexes and spontaneous T waves had the same direction in 5 or more leads of the frontal plane in 77% of the patients and in 50% of the patients in the horizontal plane. In patients with supraventricular command, this correlation was found in 82% of the patients and in 50% of the patients with idioventricular rhythm. Regardless of the type of spontaneous command, the phenomenon was better observed with normal intraventricular conduction. It was not found correlation between type, modality of stimulation and chronicity of the implant and cardiac memory. It was better observed in aVF, D2, D3 and V3, V4. Conclusion The phenomenon of cardiac memory in patients with artificial pacemaker is very frequent. The most important factor to develop the phenomenon seem to be a normal pattern of ventricular activation