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Biomedical subjects

B C Maciel

Publications and source records attributed to B C Maciel.

At least 19 recordsLinked to original sources

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%) 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%) and in only 10 group 2 patients (22.2%; 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.

Adult↗

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.

Adult↗

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.

Adult↗

Effects of blood viscosity on proximal flow convergence calculations of regurgitant flow rate and jet dimensions as evaluated by color Doppler flow mapping: an in vitro study.

There are limited data on the potential influence of blood viscosity on the quantification of valvular regurgitation by color Doppler in the clinical setting. This study was designed to evaluate the effects of blood viscosity on jet dimensions and the proximal flow convergence (proximal isovelocity surface area, PISA) method of estimating valvular insufficiency severity. We used an in vitro flow model filled with human blood at varying hematocrits (15%, 35%, and 55%) and blood viscosity (blood/water viscosity: 2.6, 4.8, 9.1) in which jets were driven through a known orifice (16 mm(2)) into a 110-mL compliant receiving chamber (compliance: 2.2 mL/mm Hg) by a power injection pump. Blood injections (2 and 4 mL) at flow rates of 4, 6, 8, 10, and 12 mL/s were performed. Proximal flow convergence and spatial distribution of jets were imaged by a 3.5-MHz transducer. Pressure and volume in the flow model were kept constant before each injection. Ultrasound settings were the same for all experiments. Jet area decreased significantly with increasing blood viscosity, but the difference in jet dimensions was much larger for lower than for higher flow rates and for highest blood viscosity. Estimation of flow rate by the PISA method was not significantly influenced by blood viscosity. Blood viscosity has a major influence in jet area, especially for lower flow rates, but did not change significantly the grading of regurgitation by the PISA method. Thus this factor should be considered for determining the method of choice when quantification of valvular regurgitation is performed in patients with anemia or polycythemia.

Blood Viscosity↗

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% reduction in luminal diameter). In each study, dobutamine (5 to 40 microg 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%, 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 +/- 11%) and dipyridamole (-18 +/- 16%) tests as compared to dobutamine (-9 +/- 6%) (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 +/- 7%; dipyridamole: -25 +/- 16%; dobutamine: -26 +/- 10%; 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.

Animals↗

Relation of regional sympathetic denervation and myocardial perfusion disturbance to wall motion impairment in Chagas' cardiomyopathy.

Impairment of sinus node autonomic control and myocardial perfusion disturbances have been described in patients with chronic Chagas' cardiomyopathy. However, it is not clear how these conditions contribute to myocardial damage. In this investigation, iodine-123 (I-123) meta-iodobenzylguanidine (MIBG) and thallium-201 myocardium segmental uptake were studied in correlation with the severity of left ventricular (LV) dysfunction detected in various phases of Chagas' heart disease. Group I consisted of 12 subjects (43 +/- 4 years, 7 men) with no symptoms and no cardiac involvement on electrocardiogram (ECG) or echocardiography; group II consisted of 13 patients (48 +/- 3 years, 9 men) with abnormal resting ECG and/or echocardiographic segmental abnormalities, and LV ejection fraction of > or = 0.5; group III was comprised of 12 patients (59 +/- 3 years, 10 men) with more severe heart disease, LV dilation, and LV ejection fraction of < 0.5. Eighteen control volunteers (38 +/- 3 years, 9 men) were also included in the study. I-123 MIBG single-photon emission computed tomographic (SPECT) segmental uptake defects were observed in group I (33%), group II (77%), and group III (92%). Quantitative analysis showed mean areas of reduced LV I-123-MIBG uptake: group I was 3.7 +/- 2.1%; group II was 8.3 +/- 2.3%; and group III was 19.0 +/- 3.3%. The differences between group I and both groups II and III were statistically significant (p < 0.001, analysis of variance test). Myocardial perfusion defects (reversible, fixed, and paradox) were observed in group I (83%), group II (69%), and group III (83%). A marked topographic association between perfusion, innervation, and wall motion abnormalities (assessed by gated-SPECT perfusion studies) was observed in all the groups. Defects predominated in the inferior, posterior lateral, and apical LV regions. Thus, extensive impairment of cardiac sympathetic function at the ventricular level occured early in the course of Chagas' cardiomyopathy and was related to regional myocardial perfusion disturbances, before wall motion abnormalities. Both conditions are associated with progression of ventricular dysfunction.

3-Iodobenzylguanidine↗

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% 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.

Blood Pressure↗

Cardiac autonomic impairment and early myocardial damage involving the right ventricle are independent phenomena in Chagas' disease.

Cardiac autonomic impairment and right side heart failure are prominent features in patients with Chagas' disease, but no causal relationship between these phenomena has been disclosed and the pathophysiology of such manifestations is unclear. Aim of study was to assess the cardiac autonomic control and biventricular function in chagasic patients in early stages of the disease, using radionuclide angiography, Valsalva manoeuvre, head-up tilt and baroreflex sensitivity evaluation. Thirty-one chagasic patients with no clinical signs of Chagas' heart disease-16 in the indeterminate phase and 15 with sole organic digestive involvement-were studied, and results compared with those obtained in 14 normal volunteers. No significant differences were observed among the three groups, in regard to any systolic or diastolic parameter of LV function, including ejection fraction, peak ejection and filling rates and correspondent times, time to end-systole, and the standard deviation of phase values. The indeterminate and digestive groups of chagasics had significantly lower right ventricular ejection fraction (45.7 +/- 6.3 and 46.2 +/- 10.1 respectively) and peak ejection rate (respectively 2.8 +/- 0.6 and 2.9 +/- 0.6) and higher right ventricular phase standard deviation (22.4 +/- 5.9 and 20.1 +/- 5.6 degrees, respectively), as compared with the control group (53.6 +/- 4.3, 3.5 +/- 0.5, and 15.8 +/- 3.8 respectively for right ventricular ejection fraction, peak ejection rate and phase standard deviation). No significant differences were found between the results of autonomic evaluation in the control and indeterminate groups of chagasic patients. The group of digestive disease patients showed abnormally lower Valsalva ratio (1.5 +/- 0.15), baroreflex sensitivity (8.85 +/- 2.05 ms/mmHg) and parasympathetically-dependent heart rate response to tilt (8.85 +/- 8.42 beats/mm) and higher Valsalva delay (15.67 +/- 1.35 s) values, compared with the control group (respectively 1.85 +/- 0.49, 20.23 +/- 12.66 ms/mmHg, 21.61 +/- 5.77 beats/mm and 10.1 +/- 2.5 s). Thus, cardiac autonomic impairment is a prominent feature in chagasic patients with the digestive but not the indeterminate form of Chagas' disease. It bears no causative relationship to the early myocardial damage that is apparent only regarding right ventricular function, in both groups of patients. Early right ventricular dysfunction is a likely mechanism for the marked predominance of systemic over pulmonary congestion when heart failure supervenes in patients with Chagas' disease.

Adult↗

[Hypertrophic cardiomyopathy treated by interventional technique of septal reduction].

A 75-year old woman with obstructive hypertrophic cardiomyopathy and class IV dyspnea refractory to medical management had relative contraindications for both pacemaker implantation and surgical approach. Percutaneous intervention was devised to perform the selective injection of absolute alcohol in the first septal branch of the left anterior descending coronary artery. This led to a limited septal infarction documented by ST elevation, enzymatic elevation and the appearance of complete right bundle branch block on the electrocardiogram. A baseline left ventricular outflow tract pressure gradient of 66mmHg was immediately abolished and no unexpected complications supervened. Currently, two months after the procedure, marked symptomatic relief is present and associated with the absence of obstructive outflow gradient, as documented by echocardiography.

Aged↗

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% of the peak HR). The contribution of sympathetic and para-sympathetic 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 (delta 0-10 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 (delta 1-4 min) related to a sympathetic-dependent mechanism was observed in T; 3) the VO2 AT (S = 1.06 and T = 1.33 l/min) and VO2 peak (S = 1.97 and T = 2.47 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.

Adaptation, Physiological↗

Reversible segmental left-ventricular dysfunction caused by accidental administration of sympathomimetic drug in human.

A inadvertently administrated high dose of sympathomimetic drug induced cardiogenic shock manifestations in a previously healthy woman. This state was characterized by EKG subendocardial injury, serum cardiac enzymes elevation, extensive regional left ventricular wall motion abnormalities on echocardiogram. Therapeutics included oxygen, systemic vasodilators and diuretics. Clinical recovery occurred over a four days period and parallels the normalization of echocardiogram and EKG alterations.

Adult↗

[Risk stratification in acute myocardial infarction survivors. Exercise stress test versus coronary angiography].

PURPOSE: To compare the predictive accuracy for future ischemic events of heart rate limited treadmill exercise test (HET) and coronary angiography (CA) applied to survivors of an uncomplicated myocardial infarction. METHODS: 142 consecutive patients (55 +/- 11 years, 80% males), presenting a non complicated acute myocardial infarction (AMI) were included. HET was performed 10 +/- 3 days after AMI, and CA during hospital stay or within 4-6 weeks. HET positivity criteria were: 1) horizontal or down-sloping ST segment displacement > or = 1 mm; 2) angina; 3) arterial pressure drop during exercise; 4) low workload (< 6 METS); 5) complex ventricular arrhythmia. At CA lesions causing > or = 50% of luminal reduction were considered significant. HET and CA results were correlated to ischemic events occurring during the follow-up (unstable angina in 20%, cardiac death 6%, and reinfarction 6%). RESULTS: HET was positive in 69 (49%) patients, exhibiting a positive predictive value for ischemic events (PV+) of 26% and a negative predictive value (PV-) of 77%. The mean event-free time was 43 +/- 3 months for positive HET and 46 +/- 3 months for a negative one (p = 0.48). CA showed 0-1 vessel involvement in 93 (66%) patients and > or = 2 vessels in 49 (34%) patients. The presence of multivascular disease at CA presented a PV+ of 37% and PV- of 82%; the mean event-free time was 37 +/- 4 months for patients with multivascular involvement and 48 +/- 2 months for patients without this pattern (p = 0.007). CONCLUSION: The predictive accuracy of HET for future ischemic events in the thrombolytic era is markedly reduced. This population of AMI survivors presents an overall good prognosis that seems to justify the poor predictive accuracy of this test.

Adult↗

[Clinical profile, coronary angiography findings and early outcome in young patients with acute myocardial infarction in the thrombolytic era].

PURPOSE: To assess the clinical, angiographic and early follow-up findings of young patients suffering an acute myocardial infarction, in comparison with older patients with infarction, in the thrombolytic era. METHODS: A retrospective analysis of the medical records of 46 patients < 40 years-old (group I) at the time of an acute myocardial infarction was compared with that of 46 older patients, randomly selected, presenting with this syndrome between february, 1991 and february, 1996 (group II). In both groups a comparison was conducted regarding the proportions of gender, risk factors, type of infarction (Q vs non-Q), left ventricular function, coronary anatomy and early mortality (1 month). The medical treatment was comparable for both groups, including the utilization of thrombolytics. RESULTS: The groups were discriminated only by: higher prevalence of smoking, of angiographically normal coronary arteries, and of non-critical (< 75% reduction of luminal diameter) coronary stenosis in group I; in the older group a higher proportion of patients had multivessel disease. Although not reaching statistical significance, a trend was observed to a more benign early course of the infarction in the patients less than < 40 years-old. CONCLUSION: The present findings are similar to those described in the pre-thrombolytic era, for young patients suffering an acute myocardial infarction.

Adult↗

[Esophageal origin of precordial pain in chagasic patients with normal subepicardial coronary arteries].

PURPOSE: To study the chest pain of esophageal origin in chagasic patients (CH) and non-chagasic subjects (NCH) with normal coronary arteries. METHODS: The study comprised 48 patients: 33 CH (age 56 years, 50% male) and 15 NCH (age 47 years, 25 male), with precordial chest pain and normal subepicardial coronary arteries. They were assigned to upper digestive tract radiologic and endoscopic study, esophageal manometric evaluation at baseline and after provocative tests (Bernstein and intravenous edrophonium). RESULTS: Radiologic study: 14 (42%) CH and 4 (27%) NCH had esophageal dilation (p > 0.05). Hiatal hernia was documented in 7 (21%) CH and 6 (40%) NCH (p > 0.05). 2) Digestive endoscopy: In 15 (45%) CH and 6 (40%) NCH distal esophagitis were seen. In the NCH, esophagitis occurred with hiatal hernia; however only 30% of CH with esophagitis had also hiatal hernia while another 30% had esophageal dilation. 3) Esophageal motility disorders (EMD): 11 (33%) CH showed EMD: 8 with inferior esophageal sphincter achalasia (IESA) and 3 with diffuse esophageal spasm. Among NCH, 2 (13%) had IESA (p > 0.05). 4) Bernstein test--a positive test was seen in 5 (15%) CH and 3 (20%) NCH-p > 0.05. CH with esophageal dilation had 14% of positive results, while CH without esophageal dilation had 16%-p > 0.05. 5) Intravenous edrophonium-esophageal contraction amplitude enhancement provoked by the drug infusion was clearly attenuated in the chagasic (6.9 +/- 12.7 mmHg) when compared with the NCH group (18.8 +/- 21.4 mmHg). A positive test (i.e. chest pain) was obtained in only one patient who was NCH. CONCLUSION: Esophageal pain could be elicited at a relatively low and comparable rate in both groups of patients.

Adult↗

[Reagudization of Chagas myocarditis inducing exclusive right ventricular failure].

Woman, 42 years-old, receiving immunosuppressive therapy for a lymphoma, presented reagudization of Chagas' disease, from its indeterminate phase. Intense inflammatory visceral aggression, due to extensive intracellular proliferation of the Trypanosoma cruzi, was the likely mechanism for acute myocarditis leading to severe right ventricular failure. Antiparasite chemotherapy was effective in the control of visceral involvement and for the remission of cardiac failure. The clinical course in this case is compatible with the hypothesis of early right ventricular damage in Chagas' disease.

Adult↗

Cine magnetic resonance imaging and color Doppler flow mapping displays of flow velocity, spatial acceleration, and jet formation: a comparative in vitro study.

To study the effects of flow acceleration and high-velocity jets on the display characteristics of cine magnetic resonance imaging compared with color Doppler flow mapping, a custom-designed in vitro flow model was developed. This model consisted of a funnel segment tapering to an orifice (0.78 cm2) that leads into a confined receiving chamber with a second, discrete orifice (0.78 cm2) at its distal end. Cine magnetic resonance images obtained at varying flow rates (1.5 to 27.2 L/min) demonstrated loss of signal intensity throughout the tapering zone of spatial acceleration and a small zone of more marked signal loss immediately proximal to the second orifice (always < 50% of the signal intensity within the tapering funnel zone) associated with more rapid spatial acceleration. A formed jet was imaged distal to the first orifice, and the turbulence area surrounding the laminar central jet core correlated well with flow rate (r = 0.98), as did the distance from the orifice to the subsequent onset of flow relaminarization (r = 0.96). A turbulent spray area was always seen distal to the second, discrete orifice. Comparative observations with color Doppler flow mapping and continuous wave Doppler demonstrated that signal intensity on cine magnetic resonance imaging is reduced by both spatial acceleration, and the high-velocity and turbulent jets associated with obstructive and regurgitant lesions. In vitro evaluation of cine magnetic resonance imaging allows comparative observations to be made about the flow characteristics of cine magnetic resonance imaging and color Doppler flow mapping and provides a more rational basis for the interpretation of cine magnetic resonance imaging in the clinical setting.

Blood Flow Velocity↗

[Detection of myocardial ischemia in chronic Chagas disease patients with atypic precordial pain by exercise and Holter tests].

PURPOSE: To determine the incidence and characteristics of myocardial ischemia, as detected by stress electrocardiography and Holter monitoring in Chagas' 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 maximal 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 exercise 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 left 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 exercise 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, at 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 ischemia 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 elucidation 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.

Adult↗