Aproximaciones sobre el panorama epidemiológico en América Latina durante cinco siglos / Approaches of the epidemiological view in Latin America during five centuries

Hace apenas 524 años la vida de los habitantes del continente americano cambió radicalmente, luego de la conquista y colonización europea. No se sabe mucho de la idea que tenían los pueblos prehispánicos sobre la salud pública; ni siquiera se sabe con certeza qué enfermedades padecían los nativos americanos antes del descubrimiento del continente. La historia de los pueblos surgidos de la conquista en relación a las políticas de salud ha estado marcada por los intereses políticos, pero sobre todo económicos de los países colonizadores. Este, es un recuento breve de esa historia.

Since 524 years ago the life of the inhabitants of the Americas changed radically after the conquest and European colonization. Not much is known of the idea faced by prehispanic peoples on public health; not even know with certainty which diseases suffered American natives before the discovery of the continent. The history of peoples emerged from the conquest in relation to health policy has been marked by political but above all economic interests of countries colonizers. This is a brief account of that history.

Hypertensive heart disease: quantitative evaluation of response to therapy with cine MR imaging.

RATIONALE AND OBJECTIVES: To assess the ability of cine magnetic resonance (MR) imaging to help detect and quantity changes in left ventricular parameters in patients receiving antihypertensive therapy. MATERIALS AND METHODS: After undergoing baseline cine MR imaging of the heart, 16 (12 men, four women) hypertensive patients participating in a prospective drug trial began isradipine therapy. Follow-up serial cine MR imaging was performed at 3 months and 6 months. Myocardial mass, end-systolic volume, end-diastolic volume, stroke volume, and ejection fraction were measured. Results from transaxially acquired three-dimensional data sets and monoplanar imaging were compared. RESULTS: Three dimensional data showed reductions of 11% in end-systolic volume (P = .0051) and 17% in end-diastolic volume (P = .0023). These changes were not detected with monoplanar imaging. Changes in myocardial mass, stroke volume, and ejection fraction were not statistically significant. CONCLUSION: Three-dimensional cine MR imaging can depict small yet statistically significant reductions in left ventricular volumes in response to antihypertensive therapy.

[Diagnosis and follow-up of muscle injuries by means of plain and contrast-enhanced MRT: experimental and clinical studies]. / Diagnostik und Verlaufskontrolle von Muskelverletzungen mittels nativer und kontrastmittelunterstützter MRT--experimentelle und klinische Untersuchungen.

PURPOSE: To clarify the value of plain and contrast-enhanced MRI for the diagnosis and follow-up of muscle injuries, by means of experimental and clinical studies. METHOD: 24 Wistar rats were studied following standardized division of the calf muscles by means of MRI carried out on the first day, and also after one, two, three and four weeks. In addition, 16 patients with muscle injuries were examined (32 examinations), first between the first and fifth day of trauma, and subsequently over a period of two to seven weeks (average: four weeks). RESULTS: In the animal experiments, there was signal reduction of T1 and an increase of the T2-weighted signal during the acute inflammatory phase. During the subacute reparative phase, there was an increase of both the T1-weighted and T2-weighted signals. These became reduced during the chronic healing phase. Early differentiation between intramuscular haematomas and bleeding, surrounding oedema and recognition of the divided muscle fibres was possible only after the intravenous injection of an MR contrast medium (Gd-DTPA). Suture of the divided muscles resulted in more rapid healing without major defects. CONCLUSION: It is possible to follow up the healing process after muscle injuries by means of plain MR. Contrast-enhanced MR allows early evaluation of muscle abnormalities, and is particularly valuable for recognising the margins of the injured muscles.

[Value of endoscopic ultrasound examination of the mediastinum in Hodgkin's and non-Hodgkin's lymphomas]. / Stellenwert des endoskopischen Ultraschalls zur Untersuchung des Mediastinums bei Hodgkin- und Non-Hodgkin-Lymphomen.

AIM: The applicability of ultrasound for diagnosing mediastinal diseases is limited by the surrounding thorax containing air and bone, permitting only restricted echo windows. Transoesophageal endoscopic ultrasound circumvents this problem and provides good visualisation of nearly all parts of the mediastinum. We evaluated the value of endoscopic ultrasonography for mediastinal staging of Hodgkin's and non-Hodgkin lymphoma patients. PATIENTS AND METHODS: From August 1994 to July 1995 36 Hodgkin's and non-Hodgkin lymphoma patients underwent clinical staging and were endosonographically examined for mediastinal involvement. CT in the spiral technique was used as the reference. RESULTS: In assessing mediastinal involvement, endoscopic ultrasound revealed a sensitivity of 96% and a specificity of 75%. There were limitations in the right paratracheal region and the area lateral to the aortic arch. CONCLUSION: Endoscopic ultrasound is a highly valuable imaging procedure for diagnosing mediastinal spread of malignant lymphomas and has interesting potentials in assessing the clinical course during therapy.

[Endoscopic ultrasound of pathological mediastinal findings]. / Endoskopischer Ultraschall pathologischer Mediastinalbefunde.

INTRODUCTION: Mediastinal diseases are mostly diagnosed by CT and MRI. The applicability of ultrasound is limited by the surrounding air- and bone-containing thorax, which permits only restricted echo windows. Transesophageal endoscopic ultrasonography circumvents this problem and ensures visualization of parts of the mediastinum. PATIENTS AND METHODS: We report our results in 38 patients with pathological mediastinal findings who were examined by endoscopic ultrasound between 1988 and 1993. The diagnoses were established by imaging and/or histological procedures. RESULTS: The following mediastinal diseases were diagnosed in 38 patients: aberrant right subclavian artery (n = 3), right aortic arch (n = 1), aortic aneurysm (n = 6), cysts (n = 4), retrosternal struma (n = 3), mediastinal lymph node tuberculosis (n = 1), Hodgkin's/non-Hodgkin's lymphomas (n = 11), lymph node involvement in bronchogenic carcinoma (n = 8), mediastinal inflammatory fibrosarcoma (n = 1). Altogether, 37/38 pathological findings were demonstrated endosonographically. CONCLUSIONS: The results in this small group of patients with pathological mediastinal findings show that endoscopic ultrasound can give additional information to conventional imaging methods. A prospective comparative study is necessary to evaluate this procedure in comparison to the established imaging techniques.

Effect of magnetic susceptibility contrast medium on myocardial signal intensity with fast gradient-recalled echo and spin-echo MR imaging: initial experience in humans.

PURPOSE: To show the effect of dysprosium diethylenetriaminepentaacetic acid bis-methylamine injection on the images of normal human myocardium. MATERIALS AND METHODS: T2-sensitive fast gradient-recalled echo (GRE) (repetition time [TR], 10.8 msec; echo time [TE], 4.2 msec) and spin-echo (SE) (TR, three RR intervals; TE, 60 msec) magnetic resonance (MR) imaging with driven equilibrium-preparation pulse was used to produce T2 contrast material enhancement. The contrast agent was injected into 12 healthy subjects at doses of 0.05, 0.1, 0.2, 0.4, and 0.6 mmol/kg. RESULTS: Driven equilibrium-prepared GRE images showed a transient decrease of myocardial signal intensity at doses of 0.2-0.6 mmol/kg. Postcontrast T2-weighted SE images showed a myocardial signal attenuation (30%-45% decrease) at a dose of 0.4 mmol/kg or higher. CONCLUSION: Dynamic MR imaging with a magnetic susceptibility contrast medium can be used to monitor the first pass of contrast media through human myocardium with a conventional MR imager and a fast GRE sequence.

Quantification of the left ventricular volumes and function with cine MR imaging: comparison of geometric models with three-dimensional data.

Acquisition and measurement of left ventricular (LV) volumes with a three-dimensional data set of cine magnetic resonance (MR) images from apex to base is a time-consuming process. Results of a study with 10 healthy volunteers and 10 patients with LV hypertrophy were prospectively evaluated. The heart was shown in the anatomic short- and horizontal long-axis planes with cine MR imaging. LV volumes were measured with various geometric models, and ejection fractions were calculated. In both groups, the values of LV stroke volume obtained with a modified Simpson rule and biplane ellipsoid models correlated well to the analysis of the three-dimensional data set of cine MR images. There were no significant differences for the calculated ejection fraction between values obtained with the modified Simpson rule or the biplane ellipsoid model versus the three-dimensional data set. A high inter-observer reproducibility of cine MR measurements with the two former models was found. Therefore, modified Simpson rule and biplane ellipsoid models, with their shorter acquisition and processing times, may increase the clinical utility of cine MR imaging.

Flow pattern analysis in the abdominal aorta with velocity-encoded cine MR imaging.

The sites of deposition of atherosclerotic plaque on the aortic wall are considered to be influenced by secondary and retrograde flow patterns that cause regions of altered shear stress. To detect secondary flow patterns and areas of retrograde flow in the abdominal aorta, velocity-encoded cine (VEC) magnetic resonance (MR) imaging was performed at five different levels of the abdominal aorta in nine healthy volunteers. Net retrograde flow (expressed as a percentage of antegrade flow) increased from proximal to distal levels and was maximal (13.8% +/- 11.8) just distal to the origin of the renal arteries. An increase in the duration of retrograde flow over the cardiac cycle was observed from proximal to distal levels. Whereas retrograde flow was present at end systole and early diastole in each volunteer at every level, the duration and amount of retrograde flow during diastole showed high interindividual variation. Such differences suggest the possibility of variable vascular geometric risk factors in the population for the development of atherosclerotic plaque. The location of retrograde flow in the abdominal aorta demonstrated in vivo with VEC MR imaging was close to that obtained with in vitro flow visualization studies in models of the abdominal aorta.

MR imaging of the myocardium using nonionic contrast medium: signal-intensity changes in patients with subacute myocardial infarction.

OBJECTIVE: Gadodiamide injection (Omniscan, Sanofi Winthrop Pharmaceuticals, New York) is a new nonionic MR contrast medium that has been shown in animal studies to provide persistent differential enhancement of myocardial infarction. Because differential enhancement of normal and infarcted myocardium may be useful for the diagnosis and sizing of myocardial infarctions, we assessed the effectiveness of gadodiamide injection in enhancing signal-intensity differences between infarcted and normal myocardium on spin-echo T1-weighted images. SUBJECTS AND METHODS: Signal intensity of normal and infarcted myocardium, contrast ratio, contrast-to-noise ratio, and signal-to-noise ratio were measured in 12 patients with subacute myocardial infarction (mean, 16 days after diagnosis) before and after injection of contrast medium. Precontrast T1-weighted and T2-weighted images were obtained with a 1.5-T MR imager. T1-weighted images were acquired 5, 15, and 30 min after gadodiamide injection (0.2 mmol/kg) and T1-weighted images with fat saturation were acquired 10 min after gadodiamide injection. RESULTS: Gadodiamide injection significantly increased signal intensity of normal (34 +/- %) and infarcted (90 +/- %) myocardium compared with their signal intensities on precontrast T1-weighted images. The contrast ratio was significantly increased, and the augmented ratios persisted throughout the 45-min observation period. The contrast ratio on T2-weighted images was comparable to that on contrast-enhanced T1-weighted images (with or without the use of fat saturation). However, the signal-to-noise and contrast-to-noise ratios of T2-weighted images were significantly lower than those of contrast-enhanced T1-weighted images. The maximum contrast-to-noise ratio for visualizing myocardial infarction was achieved on contrast-enhanced T1-weighted images with fat saturation. CONCLUSION: Improved and persistent contrast between infarcted and normal myocardium can be produced on MR images by injecting gadodiamide at a dose of 0.2 mmol/kg, which provides prolonged delineation of myocardial infarctions. Maximum contrast-to-noise ratios for detecting myocardial infarction can be produced by using fat-saturated T1-weighted imaging after a high dose of this nonionic contrast medium has been administered.

Velocity-encoded cine MRI in the evaluation of left ventricular diastolic function: measurement of mitral valve and pulmonary vein flow velocities and flow volume across the mitral valve.

Left ventricular diastolic function has been evaluated by means of analysis of the flow pattern through the mitral valve. Velocity-encoded cine magnetic resonance imaging (VEC-MR) is a new method for characterizing flow patterns in the heart. The feasibility of using VEC-MR to measure early diastolic (E) and atrial systolic (A) peak flow velocities and E/A ratios in the mitral inflow, as well as systolic (X), early diastolic (Y), and atrial systolic (Z) peak flow velocities and X/Y ratios in the pulmonary vein, was evaluated in 10 normal volunteers. The VEC-MR-derived velocities and indexes were compared with Doppler-derived results. Volumetric flow across the mitral valve was also used to measure stroke volume, cardiac output, and the left atrial contribution of left ventricular filling. VEC-MR yielded lower peak velocities than Doppler echocardiography. The velocities of the two measurements showed a significant linear correlation (Doppler E velocity = 1.30 x VEC-MR + 1.6 cm/sec, r = 0.68; Doppler A velocity = 1.83 x VEC-MR - 5.2 cm/sec, r = 0.83; and Doppler X velocity = 0.45 x VEC-MR + 0.09 cm/sec, r = 0.74). Consequently the E/A and X/Y ratios measured by these two methods showed statistically significant linear correlations with r values of 0.94 and 0.83. The volume of blood flow across the mitral valve measured by VEC-MR (5610 +/- 620 ml/min) was not statistically different from the cardiac output measured from the ascending aorta by VEC-MR (5670 +/- 590 ml/min) or by left ventricular cine magnetic resonance imaging (5440 +/- 614 ml/min). The left atrial contribution to left ventricular filling was 25.9 +/- 7.5%. Our results indicate that VEC-MR can be used not only for evaluation of left ventricular diastolic filling from the mitral valve and pulmonary vein flow velocities but also for quantitative measurement of the volume of blood flow across the mitral valve.

Right ventricular diastolic filling: evaluation with velocity-encoded cine MRI.

Abnormal flow velocity curves across the tricuspid valve (TV) and in the superior vena cava have been described in patients with abnormal right ventricular (RV) relaxation or restriction and with pericardial diseases by means of Doppler echocardiography. In this study, various imaging planes and strategies of velocity-encoded cine (VEC) MR for measurement of peak E and peak A velocities and the E/A ratio across the TV were evaluated and compared to Doppler measurements in 10 normal volunteers. In addition, VEC-MR velocity measurements were performed in the superior vena cava. Peak E and peak A velocities derived from three-dimensional VEC-MR phase images were slightly higher than velocities derived from two-dimensional VEC images. Higher velocities were measured by VEC-MR in the vertical long-axis plane compared with the horizontal long-axis plane. Excellent correlations (r > 0.89) were found between E/A ratios derived by VEC-MR and Doppler echocardiography. The interobserver variability for VEC-MR measurements was in the range of 2%. The VEC-MR depicted normal superior vena cava velocity curves in every volunteer. These results indicate that VEC-MR may offer a highly reproducible means of assessing abnormal filling properties of the RV.

Airway obstruction by right aortic arch with right-sided patent ductus arteriosus: demonstration by MRI.

An unusual cause of airway obstruction was demonstrated by MRI in two infants with congenital heart disease. The two infants experienced airway obstruction caused by a right aortic arch with right-sided patent ductus arteriosus. The diagnosis was established by MRI prior to surgery; angiography did not demonstrate the critical relationship between the large ductus and the airway. Axial, sagittal, and coronal MRI displayed the right arch, dilated ductus, and the compression of the proximal right bronchus and distal trachea by the ductus. Surgical findings confirmed the MR diagnosis. Thus, MRI can be used to localize the site of airway obstruction and to demonstrate unusual types of vascular anomalies.

Severity of aortic regurgitation: interstudy reproducibility of measurements with velocity-encoded cine MR imaging.

The interstudy reproducibility of velocity-encoded cine (VEC) magnetic resonance (MR) imaging for quantification of regurgitant volume (RV) and regurgitant fraction (RF) was studied in 10 patients with chronic aortic regurgitation. Each patient underwent two VEC MR imaging studies. RV and RF were measured on the aortic flow curve by quantifying antegrade and retrograde flow per cardiac cycle. VEC MR imaging measurements for RV and RF correlated closely with volumetric measurements for both studies (r greater than .97). Interstudy reproducibility for VEC MR imaging measurement of RV and RF was high (r greater than .97), and the interstudy variability for VEC MR imaging measurements was low. These results demonstrate a high accuracy of VEC MR imaging for measurement of RV and RF in patients with chronic aortic regurgitation. The level of interstudy reproducibility of VEC MR imaging for quantitative assessment of RV and RF indicates the potential of this technique for follow-up and monitoring of response to therapy.

[Experiences with intraoperative radiotherapy in gastric carcinoma (Berlin method)]. / Erfahrungen mit der intraoperativen Strahlentherapie beim Magenkarzinom (Berliner Methode).

The aim of our pilot study is to determine whether intraoperative radiotherapy in gastric cancer cannot only prevent a local relapse but also improve the survival rate. Since November 1987, 26 patients with resectable gastric cancer were irradiated intraoperatively with the linear accelerator using fast electrons (single dose: 12 to 16 Gy). Percutaneous radiotherapy was performed postoperatively with 24 to 38 Gy (4 x 2 Gy per week). For intraoperative and percutaneous radiotherapy the target absorbed dose was selected in a way that their combined effect on the tumor was approximately equivalent to that of a total dose of 60 Gy in the usual fractionating. Up to now, the median survival time for stage III patients (UICC 1987) has been twelve months. In five patients who died of a relapse or of peritoneal carcinosis, histologic evaluation revealed in every case a diffuse tumor type according to Lauren-classification. All relapses occurred within the first eight months. The two-year survival rate according to Kaplan-Meier is 67% for stage III. Advanced resectable gastric cancer of the intestinal tumor type seems to profit from adjuvant intraoperative radiotherapy. The results warrant further research within the framework of a prospective randomized multicenter study.

[Variability and reproducibility in the determination of left-ventricular heart volume by cine-MR. A comparison of measurement methods]. / Variabilität und Reproduzierbarkeit bei der Bestimmung des linksventrikulären Herzvolumens mittels Cine-MR. Vergleich unterschiedlicher Messmethoden.

Sixteen normal individuals were examined on a 1.5 T instrument using gradient echo sequences (cine-MR). The results of various computations were tested with respect to agreement and reproducibility of the methods. The ejection fractions calculated from bi-plane and 3-dimensional reconstructed volumes showed very low standard deviations of mean values (SD less than 2%). Volumes calculated from a single plane produced the greatest scatter of mean values (SC approximately 5%). In all sixteen subjects, the MR findings showed good reproducibility. There was very little inter-observer variability (variability less than 5%). A comparison of various methods showed that bi-plane and monoplane volume calculations obtained by MR in the cardiac axis are more accurate than those obtained by echocardiography (MR:R greater than 0.75, p less than 0.001; echo:R less than 0.75, p greater than 0.05).

[A semiquantitative assessment of aortic valve insufficiency by cine-MR compared to Doppler color echocardiography and cardioangiography]. / Semiquantitative Beurteilung von Aortenklappeninsuffizienzen mittels Cine-MR im Vergleich zur Farb-Doppler-Echokardiographie und der Kardioangiographie.

A simple, reliable semiquantitative method for evaluating aortic valve insufficiency by means of cine MR is described. Ten normal persons and 36 patients with aortic valve abnormalities were examined in a 1.5 Tesla apparatus using ECG-triggered gradient echo sequences. The heart was imaged along its short axis. Semiquantitative evaluation of aortic valve insufficiency was calculated from an MRI index, which depends on the diameter of the aortic regurgitant jet and on its length; the results were compared with colour Doppler echocardiography and cardioangiography. The MRI index showed better correlation with cardioangiography (r = 0.92) than the correlation between the colour Doppler echocardiography and cardioangiography (r = 0.78). Over and under estimates are less common with MRI than with colour Doppler echocardiography. MRI showed very little interobserver variability (r = 0.96, p less than 0.001). Cine MR is a reliable method for demonstrating aortic valve insufficiency. Using the short axis of the heart, rapid semiquantitative evaluation of the aortic regurgitant jet is regularly possible.