Biomedical subjects

S Borges-Neto

Publications and source records attributed to S Borges-Neto.

29 records · Page 2Linked to original sources

PubMed1993

Radionuclide ventricular function analysis.

The information available from ventricular function studies is important in the management of patients with cardiovascular disease. Radionuclide measurements of ventricular function are closely related to the presence and extent of myocardial damage secondary to various etiologies. The two most commonly used techniques to assess ventricular function are the first-pass radionuclide angiocardiogram and the equilibrium radionuclide angiogram. The first-pass radionuclide angiocardiographic technique assesses function at the time of the bolus administration of the radiotracer. The cardiac blood pool imaging technique has the advantage of being able to assess function hours after tracer administration. Both techniques have their own limitations and advantages. Several measurements can be obtained with radionuclide ventricular function analysis. The most important parameters obtained are the right and left ventricular EFs, wall motion analysis, intracardiac shunts, volumes, and diastolic function. Radionuclide ventricular function analysis can provide information beneficial to patient management in a variety of cardiac disorders including ischemic heart disease, valvular heart disease, and congenital heart disease. Radionuclide ventricular function measurements are well established, important determinants in patients with diagnosis and prognosis of cardiovascular disorders. New 99mTc-labeled radiopharmaceuticals are now available and permit the simultaneous measurement of myocardial perfusion and ventricular function. The combined perfusion and function studies obtained during a single tracer administration provide a large amount of information important to the management of patients with cardiovascular disease. The combination of perfusion and functional measurements may improve the prognostic evaluation of patients with cardiovascular disease.

Coronary Circulation↗

PubMed1991

Combined exercise radionuclide angiocardiography and single photon emission computed tomography perfusion studies for assessment of coronary artery disease.

Although there is widespread use of exercise thallium 201 scintigraphy and radionuclide angiocardiography in patients with coronary artery disease (CAD), little is known about the independence, concordance, or relative importance of these studies in the diagnosis, prognosis, and assessment of the outcome of therapy. The use of both tests in the same patient has been impractical because of the logistic considerations imposed by two exercise tests on separate days, and excessive radiation exposure. New technetium 99m-labeled radiopharmaceuticals with high myocardial extraction now permit the simultaneous assessment of myocardial perfusion (single photon emission computed tomography [SPECT]) and ventricular function (radionuclide angiocardiography [RNA]) during treadmill exercise (exercise tolerance test [ETT]). The ability to perform all three tests during a single exercise session offers a very attractive technique to evaluate patients with CAD. The investigators studied 86 patients with chronic CAD using the same-day perfusion and function protocol combined with treadmill exercise. The results demonstrate good concordance between myocardial perfusion and ventricular function as indicated by a significant correlation between tomographic perfusion defect size and ejection fraction (P less than .0001, R = 0.75 at rest and P less than .0001, R = 0.76 during exercise). Stepwise logistic regression was used to model ETT, RNA, and SPECT variables against the presence of one or more 60% stenoses by quantitative angiography, an end point present in 47 patients. Univariable analysis showed all three tests (ETT, RNA, and SPECT) to be significant predictors of the end points (lambda 2 = 5.1, P less than .05; lambda 2 = 12.5, P less than .001; and lambda 2 = 16.1, P less than .001, respectively). Multivariable analysis demonstrated that SPECT provided more diagnostic information than ETT and RNA (Lambda 2 = 16.1, P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Disease↗

PubMed1991

Comparison of bicycle and treadmill radionuclide angiocardiography.

The purpose of this study was to test motion-correction algorithms for initial-transit radionuclide angiocardiograms acquired at rest and during bicycle and treadmill exercise. Treadmill data was spatially reoriented by computer software designed to eliminate motion of a 125I point source simultaneously recorded at a lower energy window. A second algorithm based on left ventricular centroid counts further corrected for motion on all studies. Exercise left ventricular ejection fraction was higher on the treadmill (0.68 +/- 0.07) compared to the bicycle (0.64 +/- 0.08) (p less than 0.0001, r = 0.88). Treadmill exercise also resulted in larger end-diastolic volumes (180 +/- 30 versus 157 +/- 36, p less than 0.0001), stroke volumes (124 +/- 28 versus 101 +/- 29, p less than 0.0001) and cardiac outputs (19.9 +/- 4.6 versus 15.9 +/- 5.0, p less than 0.0001). Similar variances for these hemodynamic measurements suggest that the mean differences observed were physiologic and that error from body motion was effectively corrected by this approach. We conclude that the measurement of left ventricular function during treadmill exercise, when combined with these techniques for correcting motion, is a reasonable alternative to conventional bicycle exercise.

Adult↗

PubMed1990

Simultaneous measurement of myocardial perfusion and ventricular function during exercise from a single injection of technetium-99m sestamibi in coronary artery disease.

New radiopharmaceuticals permit simultaneous assessment of myocardial perfusion and left ventricular function using a single tracer injection. The purpose of this study was to quantitate the relation between myocardial perfusion and function at rest and during exercise in patients with documented coronary artery disease (CAD). A rest first-pass radionuclide angiocardiogram (RNA) was recorded in 51 patients with CAD during injection of 10 mCi of technetium-99m (Tc-99m) sestamibi, and tomographic perfusion images were obtained 60 minutes later. A treadmill test was then performed, and on attainment of an exercise end point a second first-pass RNA was recorded with 30 mCi of Tc-99m sestamibi. Tomographic images reflecting myocardial perfusion during exercise were obtained 1 hour later. Tomographic perfusion defect size, quantified using modifications of the Cedars-Sinai program, correlated directly with end-systolic volume and inversely with ejection fraction at rest and during exercise. However, perfusion defect size often varied widely in patients with similar left ventricular function. This independence between measurements of perfusion and function suggests that simultaneous assessment of the 2 physiologic variables could improve the diagnostic and prognostic information of radionuclide tests.

Coronary Disease↗

PubMed1990

Perfusion and function at rest and treadmill exercise using technetium-99m-sestamibi: comparison of one- and two-day protocols in normal volunteers.

The purpose of this study was to explore the feasibility of performing rest and exercise technetium-99m-sestamibi (99mTc-sestamibi) studies on the same day. We prospectively studied 34 asymptomatic volunteers using two different protocols (17 patients studied using one-day protocol and 17 patients studied using two-day protocol). For the one-day protocol, the rest study was performed first. For the two-day protocol, the exercise study was performed first followed by a second-day rest study. Left and right ventricular ejection fractions, myocardium/lung, myocardium/liver, myocardium/spleen, and myocardium/gallbladder count ratios were similar for the one- and two-day groups. No significant difference was observed in any variable measured. These data suggest that 99mTc-sestamibi can be used for rest and treadmill exercise studies performed on the same day to provide assessment of ventricular function and perfusion similar to studies performed on separate days.

Abdomen↗

PubMed1988

Quantification of myocardial infarction during coronary occlusion and myocardial salvage after reperfusion using cardiac imaging with technetium-99m hexakis 2-methoxyisobutyl isonitrile.

Myocardial imaging with technetium-99m hexakis 2-methoxyisobutyl isonitrile was investigated as a means to assess myocardial infarct size during coronary occlusion and to quantify the extent of salvaged myocardium after coronary occlusion followed by reperfusion. Open chest dogs underwent either a permanent coronary artery occlusion (Group 1, n = 16) or a 2 h occlusion followed by reperfusion (Group 2, n = 15). Animals in both groups were killed 48 h after occlusion. During coronary occlusion, 23 of the 25 dogs that survived the coronary occlusions had abnormal myocardial scintigrams. The scintigraphic perfusion defect size correlated well with the pathologic infarct size (r = 0.85 and 0.95 by planar and tomographic imaging, respectively). The planar scintigraphic defect size, but not the tomographic defect size, overestimated the pathologic size. The planar scintigraphic defect size observed during coronary occlusion was markedly reduced 48 h after reperfusion (24.8 +/- 12.8% to 10.6 +/- 9.7% of the left ventricle, p less than 0.003). The uptake of technetium-99m hexakis 2-methoxyisobutyl isonitrile in the ischemic myocardium increased significantly 48 h after reperfusion (p less than 0.003) and correlated with the increase in regional myocardial blood flow, as assessed by radioactive microspheres (r = 0.83, p less than 0.01). Thus, myocardial imaging with technetium-99m hexakis 2-methoxyisobutyl isonitrile allows reliable demonstration of the presence of acute infarction, estimation of infarct size and quantification of the extent of salvaged myocardium after coronary reperfusion.

Animals↗

PubMed1988

Quantitative thallium-201 single photon emission computed tomography after oral dipyridamole for assessing the presence, anatomic location and severity of coronary artery disease.

The objective of this investigation was to determine whether analysis of thallium-201 images as detected by quantitative single photon emission computed tomography after a single high oral dose of dipyridamole (300 mg) would accurately detect the presence of coronary artery disease and the anatomic location of the individual stenosis. Analyses were performed on 100 patients who concomitantly underwent diagnostic coronary arteriography and myocardial imaging. Tomographic myocardial perfusion defects were quantified using computer-generated polar maps. Eighty-four patients had significant coronary artery disease defined as greater than 50% luminal diameter stenosis. The sensitivity for detecting patients with coronary disease was 92% overall, 89% in patients without previous myocardial infarction and 97% in those with prior infarction. The technique had a sensitivity of 80, 87 and 51% for localizing coronary artery stenosis of the left anterior descending, the right coronary and the left circumflex artery, respectively. The corresponding specificity was 84, 92 and 92%. Furthermore, the presence of severe (greater than or equal to 70%) multivessel disease was identified with a sensitivity of 79% and a specificity of 87%. In conclusion, quantitative thallium-201 single photon emission computed tomography after oral dipyridamole has high sensitivity and specificity for diagnosing the presence of coronary disease, ascertaining the location of stenosed vessels and identifying the presence of multivessel disease.

Administration, Oral↗

PubMed1988

Clinical significance of perfusion defects by thallium-201 single photon emission tomography following oral dipyridamole early after coronary angioplasty.

The clinical significance of myocardial perfusion defects present early after angiographically successful percutaneous transluminal coronary angioplasty was assessed in 53 patients using thallium-201 single photon emission computed tomography combined with pharmacologic vasodilation induced by a large dose (300 mg) of orally administered dipyridamole. Myocardial tomographic images were obtained at a mean of 20 +/- 6 h (SD) before and 2.9 +/- 2.7 days after angioplasty. Before angioplasty, 15 (28%) of the 53 patients developed angina after dipyridamole administration, in contrast to only 3 (7.5%) of 40 patients after angioplasty (p less than 0.001). The mean percent luminal area stenosis decreased from 93 +/- 6% before angioplasty to 34 +/- 17% after angioplasty (p less than 0.001). Myocardial perfusion defects, present in 49 (93%) of the 53 patients before angioplasty, were reversible in 44 patients (83%), all of whom underwent dilation of arteries supplying the ischemic areas. After angioplasty, 26 (65%) of 40 patients had no ischemic defects, whereas 14 (35%) of the patients still had an ischemic defect in the vascular territory of the dilated artery. After a mean follow-up period of 21.7 months, 13 (33%) of 39 patients developed restenosis, 10 of whom had an ischemic defect early after angioplasty. Restenosis developed in 10 (71%) of 14 patients with an ischemic defect after angioplasty, but in only 3 (11.5%) of the patients without an ischemic defect (p = 0.007). In conclusion, thallium-201 tomography after oral dipyridamole affords convenient assessment of the physiologic significance of coronary stenosis present before angioplasty and the residual stenosis after angioplasty.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1988

Quantification of infarct size by 201Tl single-photon emission computed tomography during acute myocardial infarction in humans. Comparison with enzymatic estimates.

We prospectively investigated whether 201Tl single-photon emission computed tomography (SPECT) could accurately diagnose the presence and quantify the extent of acute myocardial infarction when compared with infarct size assessed by plasma MB-creatine kinase activity. Thirty patients with enzymatic evidence of infarction were imaged within 12-36 hours of chest pain (mean, 23.4 hours). No patient had a previous infarction, and none underwent intervention seeking to restore coronary patency. Infarct size was quantified with computer-generated polar maps of the myocardial radioactivity and expressed as a percentage of the total left ventricular volume. To assess left and right ventricular performance, blood-pool gated radionuclide angiography was performed immediately after SPECT. All 30 patients had perfusion defects consistent with myocardial infarction. Scintigraphic and enzymatic estimates of infarct size correlated well for the group as a whole (r = 0.78, p less than 0.001, SEE = 9.1) but especially for those patients with anterior infarction (r = 0.91, p less than 0.001, SEE = 7.9). The poor correlation observed in patients with inferior infarction (r = 0.50, p less than 0.05, SEE = 10.0) was believed to be related to the frequent occurrence of right ventricular involvement because SPECT assessed only left ventricular damage, whereas the enzymatic method estimated the myocardial injury in both ventricles. A quantitative index of right ventricular infarct size, derived from the relation between the scintigraphic and enzymatic estimates, had a strong inverse correlation with right ventricular ejection fraction (r = -0.89, p less than 0.001, SEE = 3.6).(ABSTRACT TRUNCATED AT 250 WORDS)

Creatine Kinase↗

PubMedDate not supplied

Analysis of cardiac arrhythmias during dobutamine pharmacologic stress testing in nuclear cardiology as related to the presence or absence of baseline arrhythmias.

BACKGROUND: Intravenous dobutamine is an acceptable pharmacologic stress agent for evaluation of myocardial ischemia, but it has the undesirable side effect of precipitating cardiac arrhythmias. All patients are susceptible to the arrhythmogenic potential of dobutamine. However, the presence of a baseline arrhythmia creates additional concern about proceeding with a pharmacologic dobutamine stress test. The purpose of this study was to evaluate cardiac arrhythmias during dobutamine stress as they relate to the presence or absence of baseline arrhythmias in patients undergoing radionuclide myocardial perfusion imaging. METHODS AND RESULTS: Data from 486 consecutive dobutamine stress tests in nuclear cardiology were reviewed retrospectively. Baseline and stress electrocardiographic monitoring and 12-lead electrocardiograms were used for classification of arrhythmias. For patients without baseline arrhythmias, the estimated probability of having nonsustained ventricular tachycardia with dobutamine stress was 4.0% (16 of 403), as compared with 15.7% (13 of 83) for patients with baseline arrhythmias (p < 0.001). Three of the 403 patients (0.7%) and 2 of the 83 patients (2.4%) had their study terminated because of ventricular tachycardia (p > 0.05). CONCLUSIONS: The probability of having nonsustained ventricular tachycardia with dobutamine stress testing was significantly greater in patients who had baseline arrhythmias than in those who had no arrhythmias at baseline. Although termination of the study because of ventricular tachycardia was not statistically significant between these two groups, patients with baseline cardiac arrhythmias should be considered at higher risk for the development of nonsustained ventricular tachycardia during dobutamine stress testing than patients who have no baseline arrhythmia.

Adult↗

PubMedDate not supplied

Prediction of severe coronary artery disease by combined rest and exercise radionuclide angiocardiography and tomographic perfusion imaging with technetium 99m-labeled sestamibi: a comparison with clinical and electrocardiographic data.

BACKGROUND: The purpose of this study was to compare the incremental value of clinical information, electrocardiographic data, myocardial perfusion imaging, and radionuclide angiography for predicting severe coronary artery disease at a single testing interval. Clinical information, treadmill exercise studies, radionuclide angiography, and myocardial perfusion imaging are important predictors of severe coronary artery disease. However, the relative and absolute diagnostic importance of each of these methods has not been addressed at a single testing interval. METHODS AND RESULTS: A same-day rest/treadmill exercise perfusion and function study was performed in 167 patients within 90 days of coronary angiography. A multivariable regression model was used to assess the independent informational content of these predictors. Clinical and electrocardiographic data were related strongly to the presence of severe coronary artery disease (chi2 = 12.2 and p < 0.001; chi2 = 11.8 and p < 0.001, respectively). Combined perfusion and functional studies contributed 31% of the diagnostic information beyond that provided by clinical and electrocardiographic data alone (p < 0.05). CONCLUSIONS: These data demonstrate that combined studies of myocardial perfusion and left ventricular function are able to improve prediction of the extent of coronary artery disease, even when clinical and electrocardiographic data are also available.

Cardiac Catheterization↗