A Study on Ventricular Late Potentials by Signal Averaged Electrocardiogram in Myocardial Infarction Patients.

Fifty patients who presented with Myocardial Infarction (MI), diagnosed by history, ECG, enzymes were subjected to late potential analysis between 7-10 days post MI by Signal Averaged Electrocardiography (SAECG). There were 42 male and 8 female patients. 34 had anterior wall MI and 16 had inferior wall MI, and all of them had Q wave infarction. History of previous MI in 12, diabetes in 14, hypertension in 34, smoking in 24 and hypercholesterolemia in 8 was noted. Patients were followed up for one year. Late potentials were positive in 10 patients (62.5%) of inferior wall MI and 6 patients (17.5%) of anterior wall MI. Those with episodes of ventricular tachycardia had increased incidence of late potentials. There was no correlation of late potentials and LV function assessed by echocardiography. Thrombolysed group had decreased incidence of late potentials.

Electrocardiograma de alta resolución / Electrocardiogram of high resolution

El electrocardiograma de alta resolución es una técnica valiosa para estudiar la patología cardiovascular y determinar su influencia en los factores de riesgo. Trata de registrar aquellos potenciales alterados que son de conducción lenta y muy bajo voltaje, denominados micropotenciales, requiriendo cierto sustrato anatómico para fijar ciertos circuitos relacionados con taquicardia ventricular. Para estudiar y separar los diferentes componentes de las señales de un electrocardiograma de alta resolución se utilizan diferentes técnicas matemáticas: señales promediadas, transformada de Fourier, transformada de Gabor, transformada de ondícula, mapeo espectro-temporal. Es importante recalcar que esta técnica de estudio de los micropotenciales en pacientes pos-infarto, por ejemplo, tiene un valor predictivo negativo cercano al 90 por ciento y el valor predictivo positivo es cercano al 20 por ciento, por lo que se recomienda su estudio en combinación con fracción de eyección, Holter de arritmia. Con la presente revisión se establecen conceptos y su utilidad en la práctica clínica: cardiopatía isquémica, displasia arritmogénica del ventrículo derecho, síndrome de Brugada, miocardiopatía dilatada, prolapso mitral, enfermedad de Chagas, fibrilación auricular, hipertensión arterial, obesidad, síndrome de QT congénito y Wolf Parkinson White.

The electrocardiogram of high resolution is a technique valuable to study the cardiovascular pathology and to determine its influence in the risk factors. It tries to register those altered potentials that are of slow conduction and very under voltage, determinated micropotential, requiring certain anatomical substrate no fix certain circuits related to ventricular tachycardia. In order to study and to separate the different components from the signals of an electrocardiogram of high resolution different mathematical techniques are used: signal averaged, transformed of Fourier, transformed of Gabor, transformed of wavelet, spectral-temporary map. It is important to stress that techniques of study of the micropotential in patients post-infarct, for example, has a negative predictive value near 90% and the positive predictive value is near 20%, reason why in combination with fraction of ejection. Holter of arrhythmia is recommended. With the present revision concepts and their actually clinical utility settle down: isquemic cardiopathy, displasya arrhythmogenic of the right ventricle, syndrome of Brugada, dilated miocardiopathy, mitral prolanse, disease of Chagas, auricular fibrilation, arterial hyspertension, obesity, congenital QT syndrome and Wolf Parkinson White syndrome.

Effects of Patency of the Infarct-Related Artery on the Signal-Averaged ECG in Acute Myocardial Infarction

BACKGROUND: In patients after acute myocardial infarction, signal-averaged electrocardiography is used as the one of the non-invasive methods for the prediction for ventricular arrhythmia, one of the causes ofn death in acute myocardial infarction. Signal-averaged electrocardiography has allowed the identification of low-amplitude, high-frequency signals(late potentials)in the terminal portion of the QRS complex. They are thougt to be occured in the portion of electrophysiologically unstable myocardium. The presence of late potentials identifies regions of delayed conducton in the elctrophysiologically unstable border zone of an acute infarction. These electrophysiologic change of myocardium is influenced by the patency of infarct-related artery. A patent artery is associated with electrical stability of myocardium, decreased in cidence of late potentials and improved survival. METHODS: 58 patients of acute myocardial infarction underwent signal-averaged electrocardiography, coronary angiography within 10 days after AMI, 20 of healthy persons underwent signal-averaged electrocardiography. RESULTS: In patent group, late potentials were recorded in 7 of 38 patients(18%) as compared with 13 of 20 patients(65%) of non-patent group. The statistically significant parameters of signal-averaged electrocardiography beteen patent and non-patent group were filtered total QRS duration(TQRS, 106.7+/-20.9msec), high frequency low amplitude signal (HLAS, 30.8+/-7.5 vs 41.3+/-16.5 msec)with HLAS being the most powerful varialble in the model. CONCLUSION: These results suggest that the patency of infarct-related artery is associated with electrophysiologic stability of myocardium and signal-averaged electrocardiography is one of the useful non-invasive method in risk stratification of acute myocrdial infarction.

Análise de potenciais tardios em pacientes com arritmias ventriculares malignas / Late potentials analysis in patients with malignant ventricular arrhythmia

PURPOSE--To assess the relationship between late potentials and spontaneous ventricular arrhythmias, organic heart disease, inducibility of arrhythmias at electrophysiological study and ejection fraction. METHODS--The population is comprised by 52 patients (41 men, 11 women with mean age 50 +/- 16 years) with spontaneous clinically documented ventricular tachycardia or ventricular fibrillation. An electrophysiological study was performed with conventional programmed stimulation. Within a week of the test a study of late potentials was also performed. RESULTS--Late potentials were documented in 73 per cent of the patients with ventricular tachycardia and only in 17 per cent of the patients with ventricular fibrillation. Sixty-eight percent of the patients with ischemic cardiopathy presented late potentials and in these, ventricular tachycardia was inducible in 93 per cent . Only one from a group of 7 patients with ventricular arrhythmias and no organic heart disease, presented late potentials. In patients with late potentials, 84 per cent have inducible ventricular tachycardia, but only 26 per cent of patients without late potentials have inducible ventricular tachycardia. The incidence of late potentials was inversely correlated with left ventricular ejection fraction. CONCLUSION--The presence of late potentials was more frequent in patients with ventricular tachycardia than in patients with ventricular fibrillation. The presence of late potentials has a sensibility of 81.5 per cent and a specificity of 78 per cent to detect patients with inducible ventricular tachycardia

The Change of Late Potential in Acute Myocardial Infarction and the Influence of Patency of Infarct-Related Artery on Its Development

BACKGROUND: The restoration of anterograde flow in the infarct-related artery(IRA) may improve electrophysiological consequences and survival. Patients with occluded IRA are more likely than those with patent IRA to have late potentials on signal-averaged electrocardiogram(SAEKG). The natural history of late potentials in the acute phase after AMI was reported to vary in recent studies and requires further investigation. Therefore, we investigated 1) whether parameters of SAEKG and incidence of late potentials are changed in 2 weeks after AMI, and 2) whether the status of IRA, ejection fraction, ventricular premature beats(VPB) on Holter and the use of thrombolytic agent can influence the developement of late potentials. METHOD: SAEKGs were performed in 40 patients with acute myocardial infarction(AMI, mean age : 56.6yr) and 20 normal controls(mean age : 53.0yr). SAEKGs were recorded first in 48 hours and then 2 weeks after AMI. Late potential were considered to be positive if two of the three following criteria were identified : 1) duration of filtered QRS complex>118ms, 2) duration of HFLA signal>40 ms, and 3) RMS voltage<20microV. RESULT: 1) The duration of filtered QRS complex and HFLA signal in patients with AMI in 48 hours and 2 weeks were longer than in the controls(p<0.01, p<0.05. respectively), and the RMS voltage in only 2 weeks was lower than in the controls(p<0.05). 2) There was no significant difference in the 3 parameters of SAEKG between 48 hours and 2 weeks after AMI, but the incidence of late potentials increased from 35%(14/40) to 42.5%(17/40). Of the 26 patients with a normal initial SAEKG, 3(11.5%) had late potentials in 2 weeks, whereas none of the patients with positive late potentials on initial SAEKG was normalized in 2 weeks. 3) The ejection fraction, the degree of VPB on the Holter EKG and the history of thrombolyic therapy in patients whose late potentials were positive were not different from those in patients with normal SAEKG. 4) In the 3 parameters of SAEKG, RMS voltage in patients with occluded IRA was significantly lower than in those with open IRA(p<0.05), and the incidence of late potentials were higher in the patients with occluded IRA(75%) than in those with open IRA(28.6%)(p<0.05). CONCLUSION: The incidence of late potentials on SAEKG after AMI was modestly increased in 2 weeks, but the development of late potentials was not influenced by the degree of frequently in patients with occluded IRA. These findings may indicate that the development of late potential after AMI tends to increase even in 2 weeks, and that the occlusion in IRA may unfavorably alter the electrophysiological state identified by SAEKG.

Clinical and Electrophysiologic Characteristics of Idiopathic Sustained Left Ventricular Tachycardia

Ventricular tachycardias(VTs) usually complicate iscemic heart disease. Cardiomyopathy or other organic heart disease and are aften associated with sudden cardiac death. Ventricular tachycardias with no apparent cardiac abnormalities, however, have been known to have different clinical features comprising a unique clinical entity among other tachycardias. Eleven patients(7men, 4 women) were investigated on their clinical features, electrophysiologic studies and late potentials. 1) The mean age at diagnosis was 23.4+/-6.5 years and the predominating clincal features were palpitation, syncope or congestive heart failure. No death occured over a mean follow up period of 29.2+/-26.5 months. 2) The resting ECGs were within normal limits in 8 patients and showed nonspecific ST-T changes in 3 patients. 3) Ventricular pacing induced sustained ventricular tachycardias in 7 patients and nonsustained VT in 1 aptient. Atrial pacing could provoke sustained VTs in 3 patients. 4) His bundle electrograms(HBE) were obtained in 7 patients during tachycardial. The HV intervals of the induced VTs distributed between 0 to -25msec in 5 patients and there was no definite His potentials in two patients. 5) The coupling interval of premature stimuli and the echo interval(the interval from the stimulus to the initiation of resulting VT) showed inverse relationship in 5 cases. No direct relationship was observed. 6) The termination mode, observed in 7 patients, showed delayed ternmination in 2 patients. 7) Late potentials(LPs) were pisitive in three patients but there was no significant statistical difference between LPs in normal control and those with idiopathic sustained left VTs. 8) Verapamil terminated VTs in 8 patients and slowed the rate of tachycardial in 1 patient. In conclusion, idiopathic sustained left ventricular tachycardias occur in younger age group and have more favorable prognosis. The findings of EPS and LPs suggest microreentry or triggered activity as their basic mechanism and verapamil can be used effectively for their termination.

Comportamento dos potenciais tardios em portadores de infarto do miocárdio submetidos à trombólise coronária / Late potentials in patients with myocardial infarction submitted to thrombolytic therapy

Objetivo­Analisar o comportamento dos potenciais tardios (Pr) em pacientes submetidos com sucesso a trombólise coronária. Casuística e Métodos­Trinta e cinco pacientes com infarto do miocárdio, 32 (91,4%) do sexo masculino com idades entre 33 e 68 (média de 52,6) anos. Trombólise coronária foi obtida durante estudo hemodinâmico através da infusão venosa, em bolo, de doses variáveis de 50,60 e 70mg de rt-PA, sucedida por nova dose de 30mg aos 60 minutos do procedimento. O exame angiocardiográfico foi repetido 12-48h após. O eletrocardiograma de alta resolução foi obtido, utilizando-se sistema ART modelo 1200 EPX, antes, a seguir e 72 horas após o término do estudo hemodinâmico. PT foram reconhecidos pela presença de ondas elétricas com amplitude inferior a 20 microvolts e duração maior que 35ms nos últimos 40ms do complexo QRS (duração total do QRS entre 110 e 114ms)...

Purpose­Analyse the behavior of the late potentials (LP) in patients submitted to thrombolysis with success. Material and Metllods­Thrty-five patients with acute myocardial infarction, 32 (91,4%) male with ages varying from 33 to 68 (mean 52.ó). Thrombolysis was obtained during cinecoronariography with intravenous infusion "in bolus" of d oses of 50mg, 60mg and 70mg of rt-PA, with a new bolus of 30mg at 60 minutes after the procedure. A new angiographic study was performed 12-48 hours late. The high resolution ECG was taken with the ART system model 1200 EPX. before, after and 72 hours later. The presence of electrical activity in the last 40ms of the QRS comple:£ with less than 20 uvolts in amplitude and more than 35ms in duration characterized the LP...