Predictors of restenosis after percutaneous coronary intervention using bare-metal stents: a comparison between patients with and without dysglycemia

The objective of this study was to identify intravascular ultrasound (IVUS), angiographic and metabolic parameters related to restenosis in patients with dysglycemia. Seventy consecutive patients (77 lesions) selected according to inclusion and exclusion criteria were evaluated by the oral glucose tolerance test and the determination of insulinemia after a successful percutaneous coronary intervention (PCI) with a bare-metal stent. The degree of insulin resistance was calculated by the homeostasis model assessment of insulin resistance (HOMA-IR). Six-month IVUS and angiogram follow-up were performed. Thirty-nine patients (55.7 percent) had dysglycemia. The restenosis rate in the dysglycemic group was 37.2 vs 23.5 percent in the euglycemic group (P = 0.299). The predictors of restenosis using bivariate analysis were reference vessel diameter (RVD): £2.93 mm (RR = 0.54; 95 percentCI = 0.05-0.78; P = 0.048), stent area (SA): <8.91 mm² (RR = 0.66; 95 percentCI = 0.24-0.85; P = 0.006), stent volume (SV): <119.75 mm³ (RR = 0.74; 95 percentCI = 0.38-0.89; P = 0.0005), HOMA-IR: >2.063 (RR = 0.44; 95 percentCI = 0.14-0.64; P = 0.027), and fasting plasma glucose (FPG): ≤108.8 mg/dL (RR = 0.53; 95 percentCI = 0.13-0.75; P = 0.046). SV was an independent predictor of restenosis by multivariable analysis. Dysglycemia is a common clinical condition in patients submitted to PCI. The degree of insulin resistance, FPG, RVD, SA, and SV were correlated with restenosis. SV was inversely correlated with an independent predictor of restenosis in patients treated with a bare-metal stent.

Minor segmental wall motion abnormalities detected in patients with Chagas' disease have adverse prognostic implications

Recent data from our laboratory have shown that patients with the indeterminate form of Chagas' disease can have impairment of left ventricular contractility, as evaluated by the slope of the left ventricle end-systolic pressure-dimension relationship. We also showed that Chagas' disease patients with minimal baseline wall motion abnormalities detected by two-dimensional echocardiography have more intense contractility impairment when compared to patients with the indeterminate form of the disease without this abnormality. The prognostic implications of these findings have not been established. We evaluated 59 patients (37-76 years, mean = 55 years) with different clinical forms of Chagas' disease, who had normal left ventricular global systolic function at baseline (57.6 ± 6.9 percent) and who had at least one additional echo during clinical follow-up (0.4-17.6; mean 4.6 years). Group 1 consisted of 14 patients with minor baseline left ventricle wall motion abnormalities and group 2 consisted of 45 patients without these abnormalities. During follow-up, global left ventricle systolic function deterioration was observed in 10 group 1 patients (71.4 percent) and in only 10 group 2 patients (22.2 percent; P < 0.005). Age and duration of follow-up were not independent determinants of left ventricular function deterioration in these patients. The present data indicate that mild segmental left ventricular wall motion abnormalities are associated with worsening of systolic function in Chagas' disease patients who have normal baseline global systolic performance.

Automated grading of left ventricular segmental wall motion by an artificial neural network using color kinesis images

The present study describes an auxiliary tool in the diagnosis of left ventricular (LV) segmental wall motion (WM) abnormalities based on color-coded echocardiographic WM images. An artificial neural network (ANN) was developed and validated for grading LV segmental WM using data from color kinesis (CK) images, a technique developed to display the timing and magnitude of global and regional WM in real time. We evaluated 21 normal subjects and 20 patients with LVWM abnormalities revealed by two-dimensional echocardiography. CK images were obtained in two sets of viewing planes. A method was developed to analyze CK images, providing quantitation of fractional area change in each of the 16 LV segments. Two experienced observers analyzed LVWM from two-dimensional images and scored them as: 1) normal, 2) mild hypokinesia, 3) moderate hypokinesia, 4) severe hypokinesia, 5) akinesia, and 6) dyskinesia. Based on expert analysis of 10 normal subjects and 10 patients, we trained a multilayer perceptron ANN using a back-propagation algorithm to provide automated grading of LVWM, and this ANN was then tested in the remaining subjects. Excellent concordance between expert and ANN analysis was shown by ROC curve analysis, with measured area under the curve of 0.975. An excellent correlation was also obtained for global LV segmental WM index by expert and ANN analysis (R² = 0.99). In conclusion, ANN showed high accuracy for automated semi-quantitative grading of WM based on CK images. This technique can be an important aid, improving diagnostic accuracy and reducing inter-observer variability in scoring segmental LVWM.

The X-X-/E+E+ genotype of the XbaI/EcoRI polymorphisms of the apolipoprotein B gene as a marker of coronary artery disease in a Brazilian sample

Studies that consider polymorphisms within the apolipoprotein B (apo B) gene as risk factors for coronary artery disease (CAD) have reported conflicting results. The aim of the present study was to search for associations between two DNA RFLPs (XbaI and EcoRI) of the apo B gene and CAD diagnosed by angiography. In the present study we compared 116 Brazilian patients (92 men) with CAD (CAD+) to 78 control patients (26 men) without ischemia or arterial damage (CAD-). The allele frequencies at the XbaI (X) and EcoRI (E) sites did not differ between groups. The genotype distributions of CAD+ and CAD- patients were different (chi²(1) = 6.27, P = 0.012) when assigned to two classes (X-X-/E+E+ and the remaining XbaI/EcoRI genotypes). Multivariate logistic regression analysis showed that individuals with the X-X-/E+E+ genotype presented a 6.1 higher chance of developing CAD than individuals with the other XbaI/EcoRI genotypes, independently of the other risk factors considered (sex, tobacco consumption, total cholesterol, hypertension, and triglycerides). We conclude that the X-X-/E+E genotype may be in linkage disequilibrium with an unknown variation in the apo B gene or with a variation in another gene that affects the risk of CAD

Effects of aerobic exercise training on heart rate variability during wakefulness and sleep and cardiorespiratory responses of young and middle-aged healthy men

The purpose of the present study was to evaluate the effects of aerobic physical training (APT) on heart rate variability (HRV) and cardiorespiratory responses at peak condition and ventilatory anaerobic threshold. Ten young (Y: median = 21 years) and seven middle-aged (MA = 53 years) healthy sedentary men were studied. Dynamic exercise tests were performed on a cycloergometer using a continuous ramp protocol (12 to 20 W/min) until exhaustion. A dynamic 24-h electrocardiogram was analyzed by time (TD) (standard deviation of mean R-R intervals) and frequency domain (FD) methods. The power spectral components were expressed as absolute (a) and normalized units (nu) at low (LF) and high (HF) frequencies and as the LF/HF ratio. Control (C) condition: HRV in TD (Y: 108, MA: 96 ms; P<0.05) and FD - LFa, HFa - was significantly higher in young (1030; 2589 ms²/Hz) than in middle-aged men (357; 342 ms²/Hz) only during sleep (P<0.05); post-training effects: resting bradycardia (P<0.05) in the awake condition in both groups; VO2 increased for both groups at anaerobic threshold (P<0.05), and at peak condition only in young men; HRV in TD and FD (a and nu) was not significantly changed by training in either groups. The vagal predominance during sleep is reduced with aging. The resting bradycardia induced by short-term APT in both age groups suggests that this adaptation is much more related to intrinsic alterations in sinus node than in efferent vagal-sympathetic modulation. Furthermore, the greater alterations in VO2 than in HRV may be related to short-term APT

Head-to-head comparison of dipyridamole, dobutamine and pacing stress echocardiography for the detection of myocardial ischemia in an animal model of coronary artery stenosis

To compare the sensitivity of dipyridamole, dobutamine and pacing stress echocardiography for the detection of myocardial ischemia we produced a physiologically significant stenosis in the left circumflex artery of 14 open-chest dogs (range: 50 to 89 percent reduction in luminal diameter). In each study, dobutamine (5 to 40 æg kg-1 min-1 in 3-min stages) and pacing (20 bpm increments, each 2 min, up to 260 bpm) were performed randomly, and then followed by dipyridamole (up to 0.84 mg/kg over 10 min). The positivity of stress echocardiography tests was quantitatively determined by a significant (P<0.05) reduction of or failure to increase absolute and percent systolic wall thickening in the stenotic artery supplied wall, as compared to the opposite wall (areas related to the left anterior descending artery). Systolic and diastolic frozen images were analyzed off-line by two blinded observers in the control and stress conditions. The results showed that 1) the sensitivity of dobutamine, dipyridamole and pacing stress tests was 57, 57 and 36 percent, respectively; 2) in animals with positive tests, the mean percent change of wall thickening in left ventricular ischemic segments was larger in the pacing (-19 Ý 11 percent) and dipyridamole (-18 Ý 16 percent) tests as compared to dobutamine (-9 Ý 6 percent) (P = 0.05), but a similar mean reduction of wall thickening was observed when this variable was normalized to a control left ventricular segment (area related to the left anterior descending artery) (pacing: -16 Ý 7 percent; dipyridamole: -25 Ý 16 percent; dobutamine: -26 Ý 10 percent; not significant), and 3) a significant correlation was observed between magnitude of coronary stenosis and left ventricular segmental dysfunction induced by ischemia in dogs submitted to positive stress tests. We conclude that the dobutamine and dipyridamole stress tests showed identical sensitivities for the detection of myocardial ischemia in this one-vessel disease animal model with a wide range of left circumflex artery stenosis. The pacing stress test was less sensitive, but the difference was not statistically significant. The magnitude of segmental left ventricular dysfunction induced by ischemia was similar in all stress tests evaluated

HFE gene mutations in coronary atherothrombotic disease

Although iron can catalyze the production of free radicals involved in LDL lipid peroxidation, the contribution of iron overload to atherosclerosis remains controversial. The description of two mutations in the HFE gene (Cys282Tyr and His63Asp) related to hereditary hemochromatosis provides an opportunity to address the question of the association between iron overload and atherosclerosis. We investigated the prevalence of HFE mutations in 160 survivors of myocardial infarction with angiographically demonstrated severe coronary atherosclerotic disease, and in 160 age-, gender- and race-matched healthy control subjects. PCR amplification of genomic DNA followed by RsaI and BclI restriction enzyme digestion was used to determine the genotypes. The frequency of the mutant Cys282Tyr allele was identical among patients and controls (0.022; carrier frequency, 4.4 per cent), whereas the mutant His63Asp allele had a frequency of 0.143 (carrier frequency, 27.5 per cent) in controls and of 0.134 (carrier frequency, 24.5 per cent) in patients. Compound heterozygotes were found in 2 of 160 (1.2 per cent) controls and in 1 of 160 (0.6 per cent) patients. The finding of a similar prevalence of Cys282Tyr and His63Asp mutations in the HFE gene among controls and patients with coronary atherothrombotic disease, indirectly questions the possibility of an association between hereditary hemochromatosis and atherosclerosis.

A pulsatile flow model for in vitro quantitative evaluation of prosthetic valve regurgitation

A pulsatile pressure-flow model was developed for in vitro quantitative color Doppler flow mapping studies of valvular regurgitation. The flow through the system was generated by a piston which was driven by stepper motors controlled by a computer. The piston was connected to acrylic chambers designed to simulate "ventricular" and "atrial" heart chambers. Inside the "ventricular" chamber, a prosthetic heart valve was placed at the inflow connection with the "atrial" chamber while another prosthetic valve was positioned at the outflow connection with flexible tubes, elastic balloons and a reservoir arranged to mimic the peripheral circulation. The flow model was filled with a 0.25 per cent corn starch/water suspension to improve Doppler imaging. A continuous flow pump transferred the liquid from the peripheral reservoir to another one connected to the "atrial" chamber. The dimensions of the flow model were designed to permit adequate imaging by Doppler echocardiography. Acoustic windows allowed placement of transducers distal and perpendicular to the valves, so that the ultrasound beam could be positioned parallel to the valvular flow. Strain-gauge and electromagnetic transducers were used for measurements of pressure and flow in different segments of the system. The flow model was also designed to fit different sizes and types of prosthetic valves. This pulsatile flow model was able to generate pressure and flow in the physiological human range, with independent adjustment of pulse duration and rate as well as of stroke volume. This model mimics flow profiles observed in patients with regurgitant prosthetic valves.

Cardiorespiratory adaptations induced by aerobic training in middle-aged men: the importance of a decrease in sympathetic stimulation for the contribution of dynamic exercise tachycardia

We investigated the effects of aerobic training on the efferent autonomic control of heart rate (HR) during dynamic exercise in middle-aged men, eight of whom underwent exercise training (T) while the other seven continued their sedentary (S) life style. The training was conducted over 10 months (three 1-h/sessions/week on a field track at 70-85 percent of the peak HR). The contribution of sympathetic and parasympathetic exercise tachycardia was determined in terms of differences in the time constant effects on the HR response obtained using a discontinuous protocol (4-min tests at 25,50,100 and 125 watts on a cycle ergometer), and a continuous protocol (25 watts/min until exhaustion allowed the quantification of the parameters (anaerobic threshold, VO2,AT; peak O2 uptake, VO2 peak; power peak) that reflect oxygen transport. The results obtained for the S and the T groups were: 1) a smaller resting HR in T (66 beats/min) when compared to S (84 beats/min); 2) during exercise, a small increase in the fast tachycardia (delta0-10 s) related to vagal withdrawal (P<0.05, only at 25 watts) was observed in T at all powers; at middle and higher powers a significant decrease (P<0.05 at 50, 100 and 125 watts) in the slow tachycardia (delta1-4 min) related to a sympathetic-dependent mechanism was observed in T; 3) VO2AT (S=1.06 and T=1.33 l/min) and VO2 peak (S=1.97 and T=2.37 l/min) were higher in T (P<0.05). These results demonstrate that aerobic training can induce significant physiological adaptations in middle-aged men, mainly expressed as a decrease in the sympathetic effects on heart rate associated with an increase in oxygen transport during dynamic exercise.

Cardiomiopatia hipertrófica tratada por técnica intervencionista de reduçäo septal / Cardiomyopaty hipertrophic treatment through technique interval the reduction septal

Mulher de 75 anos com cardiomiopatia hipertrófica obstrutiva, com dispnéia classe IV, refratária ao tratamento clínico, apresentava contra-indicaçöes relativas para abordagens cirúrgica e de implante de marcapasso. Realizou-se procedimento intervencionista para injeçäo seletiva de álcool absoluto no 1§ ramo septal da artéria interventricular anterior. O infarto septal provocado acompanhou-se de liberaçäo enzimática, elevaçäo de ST e bloqueio de ramo direito do feixe de His. Näo houve complicaçöes inesperadas, e o gradiente da via ejetiva de ventrículo esquerdo, de 66mmHg, foi imediatamente abolido. Controle ecocardiográfico evidencia manutençäo desse resultado, até o momento, dois meses após o procedimento, em correspodência a marcante alívio sintomático.

Arritmias na cardiopatia chagásica crônica / Arrhythmias in Chagas'heart disease

Na cardiopatia chagásica crônica destacam-se, pela sua prevalência e importância clínica, as bradiarritmias secundárias à doença do nó sinusal, os bloqueios atrioventriculares, as extra-sístoles ventriculares e a taquicardia ventricular. O manuseio clínico dessas arritmias fundamenta-se na avaliação clínica e laboratorial do paciente, com a finalidade de caracterizar a relação com os sintomas, avaliar prognóstico do paciente e orientar a terapêutica. A conduta consensualmente aceita para o tratamento das bradiarritmias sintomáticas na cardiopatia chagásica crônica é o implante de marcapasso cardíaco artificial. No entanto, não há consenso em relação ao tratamento das arritmias ventriculares. Como princípio geral, a conduta mais defensável atualmente é a de não tratar primariamente as arritmias ventriculares assintomáticas. Deve-se tratar com métodos farmacológicos e/ou não-farmacológicos os pacientes sintomáticos (manifestaçöes pré-sincopais ou sincopais) com taquicardia ventricular não-sustentada e os pacientes que manifestam taquicardia ventricular sustentada, independentemente da tolerância hemodinâmica, bem como os sobreviventes de parada cardiorrespiratória. Os pacientes com taquicardia ventricular sustentada recorrente e função do ventrículo esquerdo presercada são candidatos à ablação cirúrgica, ou por cateter, do circuito da taquicardia. Por outro lado, nos pacientes com taquicardia ventricular sustentada mal tolerada e nos sobreviventes de parada cardiorrespiratória deve-se considerar primariamente o implante do cardioversor-desfibrilador automático, associado ou não ao uso de antiarrítmicos.

Miocárdio hibernante: uma realidade clínica / Hibernating myocardium: a clinical reality

O conceito de hibernaçÒo miocárdica implica a ocorrência de disfunçäo ventricular crônica, potencialmente reversível, causada por dissinergia regional, dependente de isquemia prolongada. Näo tem fisiopatologia elucidada, em parte porque näo existem modelos experimentais satisfatórios para seu estudo. Diversos métodos säo capazes de demonstrar viabilidade miocárdica nas regiöes que näo exibem capacidade contrátil basal. O desmascaramento da hibernaçäo nesses territórios pode ser feito mediante demonstraçäo de reserva contrátil, de funcionamento normal da membrana celular, ou de metabolismo preservado. A correta identificaçäo de miocárdio hibernante reveste-se de especial significado clínico, por suas implicaçöes prognósticas quanto a intervençöes de revascularizaçäo miocárdica, destinadas a reabilitar a funçäo ventricular em muitos pacientes coronariopatas crônicos.

Control of heart rate during exercise in health and disease

The authors present a review of their contributions over the last decade to the study of the autonomic control of heart rate during dynamic exercise under physiological and pathological conditions. These studies included the development of new methods for the evaluation of autonomic control of heart rate during dynamic exercise in man. Pharmacological blockade of sympathetic (propranolol) and parasympathetic (atropine) efferent nerves was used to demonstrate differences in time constants and power-dependent relative participation of each division of the autonomic nervous system, as predominant mechanisms responsible for the tachycardia occurring during dynamic exercise. These findings have permitted the use of properly standardized dynamic exercise (discontinuous protocol: step powers, seated position on a bicycle ergometer, 4-min duration), as a simple and noninvasive test for the evaluation of autonomic control of the sinus node. This test has proved to be useful for detecting physiological autonomic adaptations induced by aerobic training, as well as dysfunctions occurring in pathologic conditions such as Chagas' disease and hyperthyroidism.

A circulaçäo coronária na cardiopatia chagásica crônica / Coronary circulation in chronic Chagas' heart disease

Anormalidades anatômicas e funcionais da circulaçäo coronária têm sido descritas e englobadas na teoria vascular da patogênese da cardiopatia chagásica crônica. Neste artigo foram criticamente revistos resultados de estudos em humanos e modelos experimentais da infecçäo como o T.Cruzi sobre aspectos anatômicos e funcionais da circulaçäo coronária, no epicárdio e na microcirculaçäo. por evidências necroscópicas e cinecoronariográficas, as artérias epicárdicas näo exibem, em geral, lesöes obstrutivas consideradas capazes de induzir isquemia miocárdica. Constituem exceçäo aqueles pacientes chagásicos estudados após episódio de infarto agudo do miocárdio, que apresentam frequência de obstruçöes coronarianas superponível à encontrada na populaçäo näo-chagásica com infarto agudo do miocárdio. Distúrbios prefusionais, compatíveis com as alteraçöes microvasculares experimentalmente documentadas, säo observados em pacientes chagásicos crônicos com coronárias angiograficamente normais. Essas alteraçöes podem ter relaçäo causal com a disfuncçäo contrátil regional detectada em regioöes com hipoperfusäo crônica, sugerindo a ocorrência de possíveis áreas de hibernaçäo miocárdica, análoga à que se verifica na cardiopatia isquêmica aterosclerótica. Investigaçöes recentes em cardiopatas chagásicos com precordialgia sugerem anormalidades no controle vasomotor coronariano, havendo atenuaçäo das respostas arteriais epicárdicas aos estímulos constritor e dilatador.

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

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

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

Depressed respiratory sinus arrhythmia: additional evidence for impairment of vagal activity in human hyperthyroidism

The efferent activity of the parasympathetic component of the autonomic nervous system was evaluated by measuring the magnitude of the respiratory sinus arrhythmia in 3 female patients with hyperthyroidism (Basedow-Graves' disease) before and after treatment. The heart rate variations induced by the test increased in all patients after treatment of thyrotoxicosis (from 15 + or - 2.9 to 28.3 + or - 6.6 beats/min; mean + or - SEM) with propylthiouracil (600 mg/day). This result confirms our previous observations indicating an important and reversible impairment of the efferent vagal activity in human hyperthyroidism

Leg endurance training has no effect on the autonomic control of hearth rate during isometric exercise

1. Heart rate (HR) response to isometric exercise (handgrp) was investigated in 7 normal males of sedentary habits befrore and after endurance training involving the muscles of the lower limbs. Thirteen additional sedentary individuals and 7 middle-distance renners were also studied. Isometric exercise was performed at 100, 75 and 50% of maximum voluntary contraction (MVC) during 10, 20 and 30 s, respectively. Training produced a 15.6 ñ 1.4% (mean ñ SEM) increase in VO2max and a reduction in resting HR from 69 ñ 1.9 to 58 ñ 1.7 bpm. HR was monitored throughout each period of isometric exercise. 2. The pattern of HR response to static effort performed by untrained muscles was comparable before and after training as well as in athletes and sedentary individuals during the first 10 s of contraction, a period during which tachycardia is aminly mediated by vagal release. after the first 10 s, when the sympathetic influence on tachycardia becomes evident, athlets and trained individuals showed a sligh but nonsignificant tendency toward lower HR increases. 3. These results do not demonstrate any appreciable alteration in the efferent activity of autonomic components induced by aerobic training of the leg muscles when isometric exercise is performed with untrained muscles