Detecção de isquemia miocárdica em chagásicos crônicos com precordialgia atípica pelos testes de esforço e Holter / Detection of Myocardial Ischemia in Chagas' Disease Patients with Angina-Like Symptoms by the Effort Test and Holter Monitoring

RESUMO

Objetivo - Investigar a freqüência e as características de alteraçöes isquêmicas miocárdicas detectadas pela eletrocardiografia de esforço e monitorizaçäo eletrocardiográfica contínua (Holter) em pacientes chagásicos com dor precordial. Métodos - Trinta e um pacientes com diagnósticos clínicos e sorológico de doença de Chagas (54,4 ñ 9,6 anos, 51// homens) foram investigados para esclarecimento causal de angina de peito intensa e preocupante a ponto de afetar o padräo de vida e exigir exploraçäo agressiva. A detecçäo de isquemia miocárdica consistiu de 1 teste de esforço máximo e 2) Holter de 24h. Todos os pacientes foram submetidos a cinecoronariografia, ocasiäo em que se executava manobra de hiperventilaçäo controlada para constataçäo de espasmo arterial coronário. Os resultados obtidos com os dois testes (esforço e Holter) foram correlacionados e confrontados com os obtidos durante a cinecoronariografia. Resultados - alteraçöes basais do eletrocardiograma (ECG) impediram a análise do segmento ST em 11 pacientes. Dos restantes, 7(35//) apresentaram angina no teste de esforço. Dois deles (10//) tiveram isquemia miocárdica concomitante, detectando-se coronariopatia orgânica/funcional em ambos (associaçäo positiva, p=0,03) lesöes de 90// na artéria circunflexa e de 50// no trajeto intramiocárdico da descendente anterior esquerda. Nesta última, após hiperventilaçäo, ocorreu espasmo que reduziu em mais de 30// o diâmetro luminal do segmento estenótico, com dor precordial e elevaçäo de ST, que reverteram com nitrato. Durante o Holter (16 pacientes com traçados aproveitáveis), 25// dos indivíduos apresentaram angina do peito, sem qualquer distúrbio arrítmico ou isquêmico concomitante. Isquemia silente ocorreu em 1 paciente (5//) durante o esforço e, em outros (18//), durante o Holter. Sua presença näo foi preditiva de alteraçöes coronárias orgânicas ou funcionais. Näo foram documentadas lesöes significativas nos 11 pacientes cujo ECG näo era passível de análise. Conclusäo - Observou-se importante limitaçäo da aplicabilidade geral dos métodos eletrocardiográficos para detecçäo de isquemia miocárdica nos pacientes chagásicos em decorrência das alteraçöes basais do ECG. Contudo, quando o ECG basal é adequado, o teste de esforço positivo (ST isquêmico, acompanhado de dor precordial) apresentou 100// de valor preditivo para doença arterial coronária orgânica/funcional. Isto ocorreu em pequena, porém näo desprezivel proporçäo desta populaçäo chagásica específica (10//). O teste de Holter näo contribuiu para elucidaçäo da origem da angina do peito em qualquer um dos doentes estudados. Ante a inconsistência dos resultados, o significado o significado clínico e fisiopatológico da isquemia silente na cardiopatia chágasica demanda investigaçäo ulterior

ABSTRACT

Purpose - To determine the incidence and characteristics of myocardial ischemia, as detected by stress electrocardiography and Holter monitoring in Chagus' patients whose main complaint was precordial pain. Methods - Thirty-one consecutive patients with Chagas' disease diagnosed on the basis of clinical and serological tests, and precordial pain severe enough to warrant cardiac catheterization were studied. Mean age was 54.4 ± 9.6 years, and 51% were males. EKG changes indicative of myocardial ischemia were sought during maximul exercise and also during 24-hour Holter monitoring. The detection of myocardial ischemia by each one of these tests was compared by Fischer exact test, and also correlated to anatomical and functional results of coronary angiography at rest and after standardized hyperventilation for detecting coronary vasospasm. Results - Baseline EKG changes mainly associated with ventricular conduction defects precluded the analysis of the ST segment in 11 patients. Among the other 20 patients, 7(35%) had angina during the exercice test, of whom only 2(10%) showed concomitant ischemic ST changes one had 90% stenosis in the circumflex branch and the other 50% reduction of luminal diameter in a intramyocardial segment of the leit anterior descending coronary artery, undergoing further 30% constriction after hyperventilation, with pain and ST-elevation that responded to nitrate administration. Thus, a positive correlation between a positive EKG exercise test with accompanying symptoms, and organic/functional coronary artery disease was found (p = 0.03). Holter tracings of good quality were obtained in 16 patients. Angina-like symptoms occurred in 25% of these patients, without concomitant ischemic or dysrhythmic EKG changes. Conversely, silent ischemia was detected in 1 (5%) patient during exercice and in 3 (18%) patients during the Holter monitoring None of these patients had any evidence of organic or functional alterations in the coronary arteries. The absence of significant (> 50%) narrowing of the coronary arteries, t baseline and after hyperventilation, was also documented in the 11 patients in whom no valid EKG tracings were obtained for analysis. Conclusion - EKG-based methods for detecting myocardial eschemia are of limited value in the general population with Chagas' disease presenting with precordial pain, due to the high prevalence of baseline ST changes. The overall incidence of significant coronary artery disease, as detected by angiography, was low but not negligible in this population of Chagas' patients with precordial pain (4%). Nevertheless, a positive EKG test based on ST changes and accompanying pain has a 100% positive predictive accuracy for the presence of organic or functional coronary abnormalities. No additional yield was obtained with Holter monitoring, for the elucidution of the pathophysiology of the precordial pain in Chagas' patients with atypical angina. The significance of episodes of silent ischemia in some of these patients, with angiographically normal coronary arteries, remains to be determined