Search PubMed⌕ Search

Biomedical subjects

J Heo

Publications and source records attributed to J Heo.

At least 91 records · Page 5Linked to original sources
PubMed1992

Early thallium imaging after percutaneous transluminal coronary angioplasty: tomographic evaluation during adenosine-induced coronary hyperemia.

This study examined the immediate results of 201Tl imaging during adenosine-induced coronary hyperemia in 25 patients with one-vessel coronary artery disease, 4 +/- 3 days after percutaneous transluminal coronary angioplasty (PTCA). There were special features in our study: use of quantitative angiography and single-photon emission computed tomography (SPECT); a homogeneous group of patients (one-vessel disease) and a uniform stress (adenosine infusion). As a group, quantitative coronary angiography showed a decrease in percent diameter stenosis from 72% +/- 12% to 23% +/- 14%, p < 0.001. The thallium images were normal in 17 patients and abnormal in eight patients. However, of the eight patients, four had residual stenosis either in a secondary branch or downstream; one patient had local dissection (the residual stenosis could not be assessed reliably), two patients had > 50% residual diameter stenosis, and one patient had previous Q-wave myocardial infarction with a corresponding fixed thallium defect. In each of the eight patients with an abnormal image, a logical explanation could be identified. Thus, our results suggest that maximum reactive coronary hyperemia returns to normal immediately after PTCA, and that abnormal thallium results are due to inadequate dilatation or associated lesions.

Adenosine↗
PubMed1992

Comparison of same-day protocols using technetium-99m-sestamibi myocardial imaging.

Two same-day protocols (rest/exercise [Protocol 1] and exercise/rest [Protocol 2]) with sestamibi (hexakis 2-methoxy-2-isobutyl-isonitrile) were performed within 2 to 14 days of each other after randomization. The initial study in each protocol was done using a dose of 185-296 MBq of 99mTc-sestamibi. The second study in each protocol used a dose of 555-925 MBq. SPECT imaging was started 30 to 60 min after injection using a 180 degrees anterior arc. Segmental analysis was interpreted as normal, scar or ischemia (20 segments/patient). Among the protocols, there was concordance in 93% of the segments (593/640 segments). In the 11 patients with coronary artery disease and no prior myocardial infarction who had ischemic abnormality, count densities from abnormal and normal zones were compared between the two protocols. Protocol 1 showed greater count differences between abnormal and normal zones on exercise images with better normalization of abnormality on rest images than Protocol 2 (p less than 0.05). Technetium-99m-sestamibi provides high quality images using either of the two same-day protocols. However, the rest/exercise protocol provides better image contrast and ability to detect reversibility of perfusion defects, and is the preferred same-day protocol.

Ambulatory Care↗
PubMed1991

Assessment of coronary artery disease using single-photon emission computed tomography with thallium-201 during adenosine-induced coronary hyperemia.

Thallium-201 myocardial imaging during dipyridamole-induced coronary hyperemia has been an accepted method for diagnosing coronary artery disease (CAD) and risk stratification. Adenosine is a powerful short-acting coronary vasodilator. Initial results of thallium imaging during adenosine infusion have been encouraging. In 132 patients with CAD and in 16 patients with normal coronary angiograms, adenosine was given intravenously at a dose of 0.14 mg/kg/min for 6 minutes and thallium-201 was injected at 3 minutes. The thallium images using single-photon emission computed tomography were abnormal in 47 of the 54 patients (87%) with 1-vessel, in 34 of 37 patients (92%) with 2-vessel and in 40 of 41 patients (98%) with 3-vessel CAD. The sensitivity was 92% in the 132 patients with CAD (95% confidence intervals, 86 to 96%). In patients with normal coronary angiograms, 14 of 16 patients had normal thallium images (specificity, 88%; 95% confidence intervals, 59 to 100%). The results were very similar when subgroups of patients were analyzed: those without prior myocardial infarction, elderly patients and women. The nature of the perfusion defects (fixed or reversible) was assessed in relation to whether the 4-hour delayed images were obtained with or without the reinjection technique. In patients who underwent conventional delayed imaging, there were more fixed perfusion defects than in patients with reinjection delayed imaging (16 vs 0%, p less than 0.0001). The adverse effects were mild, transient and well tolerated. Thus, adenosine thallium tomographic imaging provides a high degree of accuracy in the diagnosis of CAD. The use of the reinjection technique enhances the ability to detect reversible defects.

Adenosine↗
PubMed1991

Dipyridamole thallium imaging.

Dipyridamole cardiac imaging is a useful alternative to exercise stress testing in the evaluation of patients with ischemic heart disease. Intravenous dipyridamole has been approved recently for clinical use. Oral dipyridamole is widely available. The hemodynamic effects of dipyridamole include an increase in coronary blood flow in excess of the increase in myocardial oxygen consumption and cardiac output. The quality of the thallium images is better or similar to that of exercise thallium images. The optimal dose of intravenous dipyridamole is 0.56 mg/kg and the optimal oral dose is 300-375 mg, although higher doses may be necessary in some patients. The sensitivity and specificity of dipyridamole-thallium imaging, whether intravenous or oral, have been shown in a number of studies to be quite adequate and comparable to that achieved during exercise thallium imaging. Dipyridamole-thallium imaging has also been useful in identifying high-risk patients undergoing major elective vascular surgery. The relative merits of dipyridamole imaging versus exercise testing after acute myocardial infarction require further studies.

Coronary Vessels↗
PubMed1991

Myocardial imaging with Tc-99m teboroxime: technique and initial results.

This study examined the results of Tc-99m teboroxime imaging in 22 patients aged 59 +/- 9 years and compared the results with those of thallium-201. The exercise and rest teboroxime studies were obtained within 3 hours of each other using a dose of 15 mCi/study. Because of the very short wash-out half-life of teboroxime, imaging was begun within 1 to 2 minutes after injection. Both SPECT and planar images were obtained; the SPECT protocol was modified by changing the number of frames, the time per frame, or the filters used for reconstruction of images. The planar images were obtained in the supine or upright position. Shorter acquisition time for SPECT (10 sec/frame) and the use of a Butterworth filter with a frequency cutoff of 0.3 cycle/cm and a power of 10 yielded best image quality. There was a close agreement with thallium results in identifying an abnormal or normal perfusion pattern in 89% of vascular territories. The scans were abnormal by both techniques in 12 patients, normal in nine patients, and discordant in only one patient. Thus Tc-99m teboroxime myocardial imaging is feasible at rest and during exercise using either SPECT or planar imaging. Shorter acquisition time and appropriate filtering for SPECT imaging and the upright position in planar imaging improve image quality and are convenient for the patient.

Coronary Disease↗
PubMed1991

Nuclear cardiac imaging.

Important developments in the field of nuclear cardiac imaging include increasing use of single-photon emission computed tomography; the availability of pharmacologic stress testing; the introduction of newer technetium-labeled perfusion imaging agents; and a number of other newer imaging agents and imaging techniques. Tomographic imaging improves image quality as well as sensitivity. This improvement is probably more noticeable with pharmacologic stress testing and with the newer technetium agents. A number of pharmacologic stress agents are now being used. These include dipyridamole, adenosine, and dobutamine. In our experience, thallium tomographic imaging during adenosine-induced coronary hyperemia has resulted in a high degree of accuracy in the diagnosis of coronary artery disease. Both 99mTc-sestaMIBI (hexakis-2-methoxyisobutyl-isonitrile) and 99mTc-teboroxime may be used for simultaneous assessment of perfusion and function. These agents, although similar to thallium in many aspects, differ in many other aspects as they differ from each other. For example, sestaMIBI has a long retention time, but teboroxime has a very rapid washout time. Therefore, the imaging protocols using these two agents are considerably different. Assessment of myocardial viability has been an area of interest; specifically, the use of the reinjection technique has improved the ability to differentiate between scar tissue and viable myocardium.

Adenosine↗
PubMed1990

Left ventricular dilatation and pulmonary thallium uptake after single-photon emission computer tomography using thallium-201 during adenosine-induced coronary hyperemia.

This study examined the implications of left ventricular (LV) dilatation and increased pulmonary thallium uptake during adenosine-induced coronary hyperemia. The lung-to-heart thallium ratio in the initial images was significantly higher in patients with coronary artery disease (CAD) than normal subjects; 0.48 +/- 0.16 in 3-vessel disease (n = 16), 0.43 +/- 0.10 in 2-vessel disease (n = 20), 0.43 +/- 0.08 in 1-vessel disease (n = 16) and 0.36 +/- 0.05 in normal subjects (n = 7) (p less than 0.001, 0.09 and 0.06, respectively). There was a significant correlation between the severity and the extent of the perfusion abnormality (determined from the polar maps) and the lung-to-heart thallium ratio (r = 0.51 and 0.52, respectively, p less than 0.0002). There was also a significant correlation between lung thallium washout and lung-to-heart thallium ratio (r = 0.42, p = 0.0009) and peak heart rate (r = -0.49, p less than 0.0001). The LV dilatation was mostly due to an increase in cavity dimension (30% increase) and to a lesser extent (6% increase) due to increase in LV size. (The cavity dimensions were measured from the short-axis slices at the midventricular level in the initial and delayed images). The dilation was seen in patients with CAD but not in the normal subjects. These changes correlated with the extent and severity of the thallium perfusion abnormality. Thus, adenosine-induced coronary hyperemia may cause LV dilation and increased lung thallium uptake on the basis of subendocardial ischemia.

Adenosine↗
PubMed1990

Single photon emission computed tomography with thallium-201 during adenosine-induced coronary hyperemia: correlation with coronary arteriography, exercise thallium imaging and two-dimensional echocardiography.

The feasibility, safety and diagnostic accuracy of single photon emission computed tomography (SPECT) with thallium-201 imaging during adenosine-induced coronary hyperemia were evaluated in 53 patients with and 7 without coronary artery disease proved by coronary angiography. Adenosine was infused intravenously at a dose of 0.14 mg/kg body weight per min for 6 min and thallium was injected at 3 min. Adenosine caused an increase in heart rate (68 +/- 12 at baseline versus 87 +/- 18 beats/min at peak effect, p less than 0.0001) but no change in blood pressure. The sensitivity and specificity were 92% (95% confidence intervals 81% to 98%) and 100% (95% confidence intervals 59% to 100%), respectively; 20 (61%) of 33 patients with multivessel coronary artery disease were also correctly identified. In 30 patients, the predictive accuracy of adenosine thallium imaging was slightly higher than that of exercise SPECT thallium imaging (90% versus 80%, p = NS) (95% confidence intervals 72% to 97% and 61% to 92%, respectively). In 25 patients, two-dimensional echocardiography during adenosine infusion disclosed a new wall motion abnormality in 2 (10%) of 20 patients with coronary artery disease; 80% of these patients had reversible thallium defects (p less than 0.001). Side effects were mild and transient; aminophylline was used in only three patients. Thus, adenosine SPECT thallium imaging provides a high degree of accuracy in the diagnosis of coronary artery disease. The results are comparable with those of exercise SPECT thallium imaging. Most reversible defects in the adenosine study are not associated with any transient wall motion abnormality.

Adenosine↗
PubMed1990

Quantification of the reversibility of stress-induced thallium-201 myocardial perfusion defects: a multicenter trial using bull's-eye polar maps and standard normal limits.

A multicenter trial was performed on 140 patients from four centers to determine the accuracy of quantitative analysis of stress/delayed thallium-201 myocardial tomograms using normal limits to assess the relative amount of reversibility of stress-induced defects. The patients were found to have 85 fixed and 124 reversible defects, as determined by visual interpretation. Reversibility bull's-eye polar maps were compared to gender-matched normal limits from 36 normals. Regions were identified as reversible if their normalized difference between stress and 4 hr greater than 1.5 s.d.s. from the mean normal limits. Overall agreement between experts at multicenter sites and reversibility maps was 73% for reversible defects and 80% of fixed defects. Sensitivity in detecting reversibility was highest for the left circumflex (88%) and lowest for the right coronary (60%). These results indicate that reversibility polar maps and normal limits offer an objective, accurate technique for determining the reversibility of stress-induced perfusion defects.

Adult↗
PubMed1989

Effect of exercise level on the ability of thallium-201 tomographic imaging in detecting coronary artery disease: analysis of 461 patients.

This study examined the effect of the level of exercise on the ability of thallium-201 imaging with single photon emission computed tomography (SPECT) to detect coronary artery disease. Patients in group 1 (n = 164) achieved adequate exercise end points, defined as positive exercise electrocardiograms or greater than or equal to 85% of maximal predicted heart rate. Patients in group 2 (n = 108) had submaximal exercise. The SPECT thallium-201 images showed perfusion defects in 74%, 88%, and 98%, respectively, of patients with one, two and three vessel coronary artery disease in group 1, compared with 52%, 84% and 79%, respectively, of such patients in group 2 (p less than 0.05). Perfusion defects showed partial or complete redistribution consistent with ischemia in 56%, 80% and 88%, respectively, of patients with one, two and three vessel coronary artery disease in group 1 compared with 35%, 58% and 56%, respectively, of such patients in group 2 (p = 0.08, less than 0.03 and less than 0.001, respectively). Of 58 patients with normal coronary angiograms or less than 50% diameter stenosis, 36 (62%) had normal SPECT images. In a separate group of 131 patients with less than 5% pretest probability of coronary artery disease, the specificity was 93%. The sensitivity of exercise SPECT imaging in group 1 was higher than that of ST segment depression (p less than 0.001). Thus, the level of exercise affects the results of SPECT thallium imaging in the localization and evaluation of the extent of coronary artery disease and the detection of ischemia.

Coronary Angiography↗
PubMed1989

Use of technetium-99m isonitrile (RP-30A) in assessing left ventricular perfusion and function at rest and during exercise in coronary artery disease, and comparison with coronary arteriography and exercise thallium-201 SPECT imaging.

This study compared the results of stress and rest single-photon emission computed tomography imaging of myocardial perfusion using technetium-99m isonitrile (RP-30A) with the results of stress and redistribution tomographic thallium imaging and the results of coronary arteriography in 39 patients, 11 without and 28 with coronary artery disease (CAD). Each patient underwent 2 exercise studies at identical workload, heart rate and double product. In a subset of 13 patients, concomitant evaluation of left ventricular (LV) function using first-pass radionuclide angiography with a multi-crystal camera also was performed with bolus injections of isonitrile. Isonitrile had similar sensitivity (82 vs 82%, difference not significant), a slightly--but not significantly--higher specificity (100 vs 82%) and similar predictive accuracy (87 vs 82%) to thallium-201. The tracer uptake was assessed in 20 segments/study. There was concordance between the isonitrile and thallium-201 images in 723 of the 780 segments (93%) (kappa = 0.83 +/- 0.02). In general, the isonitrile images were considered of better quality than the thallium-201 images. All 10 patients with CAD who underwent concomitant first-pass radionuclide angiography had either perfusion abnormalities or an abnormal ejection fraction response to exercise. Thus, technetium-99m isonitrile provides a reliable method of assessment of CAD with a sensitivity, specificity and predictive accuracy comparable to that of exercise thallium-201 imaging. Additional advantages include better image quality and the ability to obtain concomitant assessment of LV function with the use of first-pass radionuclide angiography.

Angiography↗
PubMed1989

Use of oral dipyridamole SPECT thallium-201 imaging in detection of coronary artery disease.

This study examined the merits of oral dipyridamole SPECT thallium-201 imaging in detecting CAD and multivessel CAD. The 65 patients included in this study (aged 62 +/- 11 years) were not candidates for exercise testing (for the usual reasons). Coronary arteriography revealed no significant CAD in 17 patients and greater than or equal to 50% narrowing of one or more vessels in 48 patients; 12 had one-vessel and 36 had multivessel CAD (high-risk group). Thallium-201 was injected intravenously 45 minutes after an oral dose of 375 mg of dipyridamole, and SPECT imaging was performed within 10 minutes and 4 hours after injection. There were no serious side effects; only six patients (8%) had ST segment depression and 18 patients (28%) had chest pain. The heart rate increased from 74 +/- 15 beats/min at rest to 84 +/- 14 beats/min at peak effect (p = 0.001); the systolic blood pressure did not change (130 +/- 18 and 128 +/- 20 mm Hg, respectively, p = NS). The thallium images were abnormal in 6 of 17 patients (35%) with no CAD, in 7 of 12 patients with one-vessel disease (58%), and in 34 of 36 patients with multivessel CAD (94%) (p = 0.001). Twenty-one of 25 patients (84%) with a perfusion abnormality in more than one vascular territory had multivessel CAD assessed by angiography. Thus oral dipyridamole SPECT thallium-201 imaging is a safe and inexpensive method for the detection of CAD in patients who are otherwise not candidates for exercise testing.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1989

Relation between myocardial thallium-201 kinetics during exercise and quantitative coronary angiography in patients with one vessel coronary artery disease.

This study examined the relation between the kinetics of thallium-201 and coronary stenosis in 30 patients with one vessel coronary artery disease; 25 patients had no visible collateral vessels. The myocardial thallium concentration in the postexercise images and percent washout were determined in the distribution of the diseased vessel and a normal vessel, and each was expressed as a ratio. Coronary stenosis was assessed as minimal diameter stenosis, minimal area stenosis and percent diameter stenosis. The correlations between the myocardial concentration ratio or washout ratio and the descriptors of coronary stenosis improved when the patients with collateral vessels were excluded. There were significant correlations between the myocardial thallium concentration ratio and minimal diameter stenosis (r = 0.73, p less than 0.001), minimal area stenosis (r = 0.72, p less than 0.001) and, to a lesser degree, percent diameter stenosis (r = -0.51, p less than 0.01). Similarly, there were significant correlations between washout ratio and minimal diameter stenosis (r = 0.50, p less than 0.01) and minimal area stenosis (r = 0.45, p less than 0.02) but not percent diameter stenosis (r = 0.37, p = 0.06). Thus, variation in thallium kinetics in relation to the severity of coronary stenosis can be demonstrated with conventional imaging in patients with one vessel disease. The myocardial thallium concentration and washout are physiologic expressions of the severity of perfusion deficit and are dependent on collateral flow. The myocardial thallium concentration ratio and washout ratio correlate better with minimal diameter and area stenosis than with percent diameter stenosis.

Aged↗
PubMed1988

Use of exercise thallium-201 imaging for risk stratification of elderly patients with coronary artery disease.

Although coronary artery disease (CAD) may be asymptomatic, it is the most common cause of death in elderly patients in the U.S. This study examined the prognosis of 449 patients with a mean age of 65 years using exercise thallium-201 imaging. At a follow-up of 25 months, 45 patients underwent coronary artery revascularization, 8 died of cardiac causes and 10 had nonfatal acute myocardial infarctions (AMIs). Thus the total of patients with "hard" events was 18. The events included 12 of 276 patients with atypical or non-anginal symptoms versus 6 of 128 with typical angina (p = not significant); 7 of 51 patients (14%) with Q-wave AMI versus 11 of 353 (3%) without Q-wave AMI (p less than 0.001); 1 of 183 patients (1%) with normal versus 17 of 221 (8%) with abnormal exercise thallium-201 images (p less than 0.002); 10 of 76 patients (13%) with multi vessel thallium-201 abnormality vs 8 of 328 (2%) with no or 1-vessel thallium-201 abnormality (p less than 0.001) and 10 of 96 patients (10%) with greater than or equal to 3 abnormal segments by thallium-201 imaging (total segments = 9) versus 8 of 308 patients with no or less than 3 abnormal segments (p less than 0.001). The number of segments with thallium-201 defects was 1 +/- 2 patients without and 3 +/- 2 in patients with hard events (p less than 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗