ABSTRACT
Signal-averaged electrocardiogram (SAECG) identifies ventricular late potentials (LP), low-amplitude electrical signals that are markers of slow cardiac conduction in fibrous myocardium, consisting in a predictive factor for sudden death in dogs at risk of sustained ventricular tachycardia. The aim of this study was to establish reference values of SAECG for German Shepherd and Boxer dogs. SAECG was performed in 19 German Shepherd and 28 Boxer client-owned dogs, and parameters analyzed were QRSd (duration of filtered QRS), LAS<40μV (duration of low-amplitude signals in terminal portion of filtered QRS) and RMS40 (root square of mean voltage over the last 40 milliseconds of filtered QRS), with two different filters (25-250 Hz and 40-250 Hz). Statistical analyses was achieved by T Student test (p<0.05) to identify differences between the two groups and between the values obtained with the two filters. No statistical difference was found in SAECG variables between the two breeds with the two different filters (p>0.05). Achieving normal values of SAECG in German Shepherd and Boxer dogs is important to further research late potentials in animals of these breeds with hereditary ventricular tachycardia or arrhythmogenic cardiomyopathy and identification of individuals at high risk of cardiac-related sudden death...
O eletrocardiograma de alta resolução (ECGAR) identifica os potenciais tardios (PT), sinais elétricos de baixa amplitude considerados marcadores de condução cardíaca lenta de áreas fibrosadas do miocárdio, cuja presença consiste em fator preditivo de morte súbita em cães com taquicardia ventricular sustentada. O objetivo deste estudo foi o estabelecimento de valores de referência para o ECGAR de cães Boxer (n=28) e Pastor Alemão (n=19). Os seguintes parâmetros do ECGAR foram analisados: dQRS (duração do QRS filtrado), LAS<40μV (duração dos sinais de baixa amplitude no final do QRS filtrado) e RMS40 (raiz quadrada da voltagem média do final do QRS filtrado), com dois tipos diferentes de filtro (25-250 Hz e 40-250 Hz). Análise estatística foi realizada por meio do teste T de Student (p<0,05) para identificar diferenças entre os dois grupos e entre os valores obtidos com os dois filtros. Não foram encontradas diferenças significativas entre as variáveis de ECGAR nas duas raças estudadas com os dois diferentes filtros (p>0,05). A obtenção dos valores de normalidade de ECGAR em cães dessas raças auxiliará na realização de futuras pesquisas de potenciais tardios em animais com taquicardia ventricular hereditária ou cardiomiopatia arritmogênica, bem como na identificação dos indivíduos com alto risco de morte súbita de origem cardíaca...
Subject(s)
Animals , Dogs , Arrhythmias, Cardiac/veterinary , Dogs/physiology , Arrhythmogenic Right Ventricular Dysplasia/veterinary , Electrocardiography/veterinary , Tachycardia, Ventricular/veterinary , Death, Sudden, Cardiac/veterinary , Reference ValuesABSTRACT
The accuracy of high resolution electrocardiographic (HRECG) methods for stratifying the risk of malignant ventricular arrhythmia depends on the fidelity of QRS fiducial points detection. This study aims at examining the effect of acquisition and processing variables in HRECG on the variability of QRS complex offset (QRS offset) detection in simulated and biological signals, as well as investigating the factors related to the so called uncertainty principle applied to HRECG. Successive QRS offset locations were calculated in different signals configurations including HRECG data from patients with and without ventricular late potentials and simulated data using linear and exponential functions. The expected error in QRS offset detection was assessed as a function of: i) signal characteristics (Simulated or Biological); ii) Sampling Frequency (SF); iii) Residual Noise Level (RNL); iv) QRS maximum amplitudes. The uncertainty principle was related to HRECG and a given exponential signals, and increasing RNL up to 0.5 μV. SF and RNL are outstanding factors influencing QRS offset variability. Thus, HRECG related uncertainty principle is a deterministic phenomenon associated with both HRECG signal and mathematical formulation of the terminal decay of the QRS complex to the fusion with the ST segment.
A precisão dos resultados dos exames de eletrocardiografia de alta resolução (ECGAR) para estratificação do desenvolvimento de arritmias ventriculares malignas depende da fidelidade na detecção dos pontos fiduciais do complexo QRS. O presente estudo tem o objetivo de avaliar o efeito das variáveis de aquisição e processamento do ECGAR sobre a variabilidade da detecção do ponto final do complexo QRS (QRS-fim) em sinais biológicos simulados e reais, bem como investigar o efeito de condições relacionadas ao assim formulado princípio da incerteza da eletrocardiografia de alta resolução. Detecções sucessivas do QRS-fim foram realizadas usando diferentes configurações de sinais simulados e de pacientes com e sem potenciais tardios ventriculares. Os sinais simulados empregaram funções lineares e exponenciais para mimetização da porção final do complexo QRS. O erro de detecção do QRS-fim esperado foi avaliado em função de: i) procedência dos sinais (simulado ou biológico); ii) frequência de amostragem (FA); iii) nível de ruído residual (NRR); iv) amplitude máxima do complexo QRS. A presença do princípio da incerteza relacionou-se ao padrão de decaimento exponencial e ao aumento progressivo da NRR, até 0,5 μV. FA e NRR têm impacto significativo na variabilidade do QRS-fim. Assim, o principio da incerteza da ECGAR é um fenômeno determinístico dependente da forma de onda relativa ao decaimento da região terminal do complexo QRS até a sua fusão com o segmento ST.
Subject(s)
Humans , Electrocardiography/instrumentation , Electrocardiography/methods , Electrocardiography , Arrhythmias, Cardiac/complications , Bundle-Branch Block/diagnosis , Heart Rate , Time FactorsABSTRACT
PURPOSE--To study by using the signal-averaged P wave, the atrial activation of patients with documented episodes of paroxysmal atrial fibrillation (PAF). METHODS--This study enrolled a total of 20 patients with documented episodes of paroxysmal atrial fibrillation (males 14; mean age 58.4 +/- 10.6 years). The signal-averaged P wave was recorded with a Corazonix Predictor II system. The total P wave duration was determined from the combined filtered x,y,z vector-magnitude and used for analysis. The results were compared with a normal group of 10 patients, matched in age. RESULTS--In the control group, the total P wave duration ranged from 120.0 to 135.0 (mean = 128.3 +/- 5.8) ms. In the group of PAF, the total P wave duration ranged from 118.0 to 168.5 (mean = 151.5 +/- 13.7) ms (p < 0.000). Sixteen (80) of this patients showed a P wave duration > 140.0 ms. With a cut < 140.0 ms for the normal atrial activation, the sensitivity was 76, specificity was 100, positive and negative predictive value were 100 and 60 respectively for the method detected patients with PAF. CONCLUSION--Patients with PAF showed a prolonged signal-averaged P wave duration and should be differentiated by this method from the normal population.