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Biomedical subjects

J Heo

Publications and source records attributed to J Heo.

At least 73 records · Page 4Linked to original sources
PubMed1993

Simultaneous assessment of left ventricular perfusion and function with technetium-99m sestamibi after coronary artery bypass grafting.

This study examined the left ventricular perfusion and EF by using simultaneous SPECT and first-pass radionuclide angiography with technetium 99m sestamibi in 95 patients after uncomplicated coronary artery bypass grafting. The patients were divided into those with normal EF and no previous myocardial infarction before surgery (group 1, n = 57), and those with abnormal EF or infarction (group 2, n = 38). The SPECT images were normal in 37 patients in group 1 and in 6 patients in group 2 (p < 0.0001). The patients with normal SPECT images had a higher EF after surgery than those with abnormal images (65% +/- 10% vs 50% +/- 14%, p < 0.0001) and was higher in group 1 than in group 2 (64% +/- 8% vs 46% +/- 16%, p < 0.0001). There was a significant correlation between the EF and the extent of perfusion abnormality (r = -0.44, p < 0.0001). The patients with normal SPECT images could not be separated from those with abnormal images based on peak CK, CK-MB, and the electrocardiographic changes. Of the 69 patients with postoperative EF > or = 50%, the perfusion pattern was normal in 41 and abnormal in 28; of the 26 patients with EF < 50%, 24 had abnormal SPECT (p < 0.003). There was no significant change in mean EF after surgery (55% +/- 14% before vs 56% +/- 15% after). Thus simultaneous assessment of left ventricular perfusion and function after coronary artery bypass grafting showed that an abnormal perfusion pattern may exist despite a normal EF. These patients could not be predicted by enzymes or electrocardiographic changes.

Aged↗
PubMed1993

Independent and incremental prognostic value of exercise single-photon emission computed tomographic (SPECT) thallium imaging in coronary artery disease.

OBJECTIVES: The objective of this study was to examine the independent and incremental prognostic value of exercise single-photon emission computed tomographic (SPECT) thallium imaging in patients with angiographically defined coronary artery disease. BACKGROUND: Previous studies showed the importance of exercise thallium-201 in risk stratification. However, most of these studies used planar imaging techniques. METHODS: Follow-up data were obtained in 316 medically treated patients with coronary artery disease. Cox proportional hazards regression models were used to examine the independent and incremental prognostic values of clinical, exercise, thallium and cardiac catheterization data. RESULTS: There were 35 events (cardiac death or nonfatal myocardial infarction) at a mean follow-up time of 28 months. Univariate analysis showed that gender (chi-square = 5.1), exercise work load (chi-square = 3.1), extent of coronary artery disease and left ventricular ejection fraction (chi-square = 14.8) and thallium variables (chi-square = 22.7) were prognostically important. The thallium data provided incremental prognostic value to catheterization data (chi-square = 33.7, p < 0.01). The extent of the perfusion abnormality was the single best predictor of prognosis (chi-square = 14). Patients with a large perfusion abnormality had a worse prognosis than that of patients with a mild or no abnormality (Mantel-Cox statistics = 10.6, p < 0.001). CONCLUSIONS: In medically treated patients with coronary artery disease, exercise SPECT thallium imaging provides independent and incremental prognostic information even when catheterization data are available. The extent of the perfusion abnormality is the single most important prognostic predictor.

Aged↗
PubMed1993

Identification of extensive coronary artery disease in women by exercise single-photon emission computed tomographic (SPECT) thallium imaging.

OBJECTIVES: The aim of this study was to examine the ability of exercise single-photon emission computed tomographic (SPECT) thallium imaging to identify high risk women with left main or three-vessel coronary artery disease using a stepwise discriminant analysis. BACKGROUND: Previous studies have used statistical methods to identify high risk men with coronary artery disease. Only limited data are available in women. METHODS: Exercise SPECT thallium imaging and coronary arteriography were performed for evaluation of chest pain in 243 women. Group 1 comprised 58 women with left main or three-vessel coronary disease and group 2 comprised 185 women with no or one- or two-vessel disease. Stepwise discriminant analysis was used to determine predictors of left main or three-vessel disease. RESULTS: On univariate analysis, women in group 1 were older (p < 0.03) and had a lower exercise work load (p < 0.02), lower exercise heart rate (p < 0.004), higher prevalence rate of diabetes mellitus (p < 0.0003) and more multivessel thallium abnormality (p < 0.0001) compared with women in group 2. On multivariate analysis, only multivessel thallium abnormality (F = 43) and exercise heart rate (F = 6) were independent predictors of left main or three-vessel coronary disease. A model based on these two variables separated the women into three risk groups: 99 patients with 9%, 70 patients with 23% and 74 patients with 45% prevalence of left main or three-vessel disease (p < 0.0001). CONCLUSIONS: High risk women with left main or three-vessel coronary disease can be identified by exercise SPECT thallium imaging.

Aged↗
PubMed1993

Effect of adenosine on coronary blood flow and its use as a diagnostic test for coronary artery disease.

Myocardial perfusion imaging during adenosine induced coronary hyperaemia is a highly sensitive method for diagnosing coronary artery disease. Most perfusion defects reflect heterogeneity in coronary blood flow in the territories of normal and diseased coronary arteries. Myocardial ischaemia can occur, however, due to subendocardial hypoperfusion and coronary artery steal. Evidence for myocardial ischaemia is more difficult to document in clinical than in experimental studies, and includes abnormalities in the ST segment, wall motion, haemodynamic variables, metabolism, and coronary blood flow responses. Using these indices, myocardial ischaemia may occur in some patients with coronary artery disease but it is not a prerequisite for the development of perfusion abnormalities and for the diagnosis of coronary artery during adenosine stress testing.

Adenosine↗
PubMed1993

The role of nuclear imaging in ischemic heart disease.

Assessment of myocardial perfusion during exercise and pharmacologic stress testing is an important factor in the detection of coronary artery disease and in risk assessment. Imaging techniques that examine myocardial perfusion and cellular integrity or myocardial metabolism flow mismatches aid in the detection of reversible causes of left ventricular dysfunction. These techniques are also helpful in managing patients after percutaneous transluminal coronary angioplasty or thrombolytic therapy.

Adenosine↗
PubMed1993

Age- and sex-related differences in the use of coronary angiography in patients undergoing adenosine SPECT thallium imaging.

BACKGROUND: Recent reports suggest sex-related differences in the management of patients with coronary artery disease. METHODS: This study examined the pattern of use of coronary angiography in 535 patients initially referred for adenosine single photon emission computed tomography (SPECT) thallium imaging. RESULTS: Coronary angiography was carried out more often in patients under 70 years of age than those over 70 years of age [107 out of 322 (33%) versus 50 out of 213 (23%), P < 0.01]. Even in patients with abnormal adenosine SPECT thallium results, coronary angiography was less frequently performed in the elderly [40 out of 130 (31%) versus 82 out of 178 (46%), P < 0.01]. Women underwent coronary angiography less often than men [56 out of 261 (21%) versus 101 out of 274 (37%), P < 0.0002]. This difference was due to differences in patients under 70 years of age [31 out of 138 women (22%) versus 76 of 184 men (41%), P < 0.003)], but not in patients over 70 years of age. In patients with abnormal adenosine thallium image results, the difference between men and women was still present: 37 out of 112 women (33%) versus 85 of 196 men (43%) underwent coronary angiography (P = 0.05). Stepwise discriminant analysis of clinical and scintigraphic variables identified four independent predictors of the need for coronary angiography; the abnormal thallium image results (chi 2 = 33, P < 0.0001); the size of the perfusion abnormality (chi 2 = 7, P < 0.01); sex (chi 2 = 7, P < 0.01) and age (chi 2 = 4, P < 0.05). CONCLUSION: Coronary angiography is less often performed in women and elderly patients even when initial screening results are abnormal. The relation of this observation to subsequent clinical course and events requires further studies.

Adenosine↗
PubMed1992

Mechanism of exercise-induced hypotension in coronary artery disease.

Hypotension during exercise testing has been considered a marker of extensive coronary artery disease (CAD) and poor prognosis. The mechanism of hypotension was examined in 25 CAD patients who developed hypotension during treadmill exercise testing (mean decrease in systolic blood pressure [BP] 33 +/- 13 mm Hg) (group 1) and was compared with the results of 25 CAD patients who had a normal systolic BP response to exercise (mean increase 53 +/- 15 mm Hg) (group 2). The 2 groups were comparable in age, sex, extent of CAD, previous myocardial infarction, left ventricular ejection fraction, history of hypertension and cardiac medications. Exercise heart rate (121 +/- 23 vs 133 +/- 25 beats/min; p = not significant [NS]) and duration (6 +/- 2 vs 7 +/- 3 minutes; p = NS) were comparable. ST-segment depression occurred in 44% of patients in group 1 and in 52% in group 2 (p = NS), and angina during exercise occurred in 60% of both groups. Single-photon emission computed tomographic thallium images were abnormal in 24 patients (96%) in group 1 and in 20 patients (80%) in group 2 (p = NS). Percent thallium abnormality was 19 +/- 12% in group 1, and 18 +/- 14% in group 2 (p = NS), and the severity of thallium abnormality was 710 +/- 510 in group 1, and 510 +/- 500 in group 2 (p = NS). Ischemia involving the inferior/posterior segments was seen in 68% of patients in group 1 and in 60% in group 2 (p = NS). Increased lung thallium uptake was seen in 48% of both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

The perfusion pattern in coronary artery occlusion: comparison of exercise and adenosine.p6.

This study compared exercise to adenosine thallium-201 single photon emission computed tomography in detecting occlusion of left anterior descending or right coronary arteries in patients with no previous myocardial infarction. There were 41 patients who underwent adenosine thallium imaging (adenosine infusion at a rate of 140 micrograms/kg/min for 6 min), and 143 patients who underwent exercise thallium imaging. There were more patients with right coronary than left anterior descending coronary artery occlusion. Thus, in the adenosine group, there were 15 patients with left anterior descending artery occlusion, and 26 with right coronary artery occlusion, and in the exercise group, there were 46 patients with left anterior descending artery occlusion, and 97 patients with right coronary artery occlusion. In the adenosine group, the thallium images were abnormal in 41 patients (100%), while in the exercise group, the thallium images were abnormal in 125 patients (87%, P < 0.02) in the territories of the occluded arteries. ST segment depression was noted in 19 patients (46%) in the adenosine group, and 69 patients (48%) in the exercise group (P:NS). In patients with isolated single vessel occlusion, the size of the perfusion abnormality was 28 +/- 9% with adenosine, and 21 +/- 12% with exercise (P:NS). Thus, most patients with occlusion of the left anterior descending or right coronary artery have regional perfusion abnormality during stress; the different role of collaterals with each type of stress may explain the higher percentage of abnormal results with adenosine than exercise.

Adenosine↗
PubMed1992

Technetium-labeled myocardial imaging agents.

99mTc sestamibi and 99mTc teboroxime has unique features that differ from thallium-201 in dosimetry, energy, cellular transport, extraction fraction, retention, washout, and imaging protocols. Sestamibi is ideal for gated and SPECT imaging while SPECT imaging with a multi-head detector system is preferred for teboroxime. Both permit simultaneous assessment of perfusion and function using first-pass radionuclide angiography. This paper discusses the special features and clinical applications of these two technetium agents.

Coronary Disease↗
PubMed1992

The treadmill exercise score revisited: coronary arteriographic and thallium perfusion correlates.

The treadmill exercise score has been used to stratify patients into low-, moderate-, and high-risk groups. This score is derived from ST segment depression, angina, and exercise duration. To determine the coronary arteriographic and exercise thallium perfusion correlates of the score, we examined the extent of coronary artery disease and exercise single photon emission computed thallium-201 results in 834 patients for whom cardiac catheterization data were available. Of those, 174 had no coronary artery disease, 195 had one-vessel, 246 had two-vessel, and 219 had three-vessel disease. Based on the treadmill exercise score, 369 were in the low-risk, 384 in the moderate-risk, and 81 in the high-risk group. The extent of coronary artery disease was 2.1 +/- 1 diseased vessels in the high-risk, 1.7 +/- 1 in the moderate, and 1.4 +/- 1.1 in the low-risk group (p < 0.01). The extent of the thallium abnormality (maximum number of abnormal segments 120/patient) was 10 +/- 6 in the high-risk, 7 +/- 6 in the moderate, and 6 +/- 5 in the low-risk group (p < 0.05). Based on the extent of coronary artery disease and results of thallium imaging, patients were reclassified into three groups: group 1 had three-vessel disease and/or > or = 10 abnormal segments (n = 387), group 3 had no coronary artery disease or one-vessel disease and less than five abnormal segments (n = 212), and the remaining patients were in group 2 (n = 235).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Single photon emission computed tomographic teboroxime imaging with a preprocessing masking technique.

We previously reported that single-head SPECT imaging with teboroxime is feasible. However, excessive hepatic uptake in some patients may interfere with image interpretation. This study examined the feasibility of improving image quality by use of a preprocessing masking technique to subtract hepatic activity. A band of 10 pixels in width adjacent to the inferior cardiac silhouette was marked on the raw planar images, and then SPECT reconstruction was done with the Butterworth filter with a frequency cutoff of 0.3 cycles/cm and the power of 10. The stress and rest images were compared before and after masking in 10 patients who underwent SPECT teboroxime imaging during adenosine-induced coronary hyperemia (140 micrograms/kg/min for 6 minutes). SPECT imaging with a single-head detector was performed with the use of a 180-degree anterior arc (from the 45-degree left posterior oblique projection to the 45-degree right anterior oblique projection); 32 images at 8 seconds per stop were obtained (total imaging time = 6.8 minutes). All images were considered subjectively better after the masking technique was used, especially for assessment of inferior wall perfusion pattern. The maximum count in any pixel was in the hepatic region of interest before masking and in the cardiac region of interest after masking (303 +/- 110 counts vs 166 +/- 55 counts; p < 0.001). The difference was especially pronounced in the images that were obtained when patients were at rest (366 +/- 102 counts vs 184 +/- 64 counts; p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1992

Side effects during adenosine thallium imaging with single-port or double-port infusion protocols.

The double-port infusion protocol during adenosine thallium imaging involves the use of two infusion systems, one for adenosine and one for thallium. The single-port infusion protocol, on the other hand, uses one infusion system; both adenosine and thallium are injected via a "Y" connection. This study examined the possibility that the single infusion system, by displacing a column of blood filled with adenosine, may be responsible for a greater incidence of side effects. In a parallel study, 140 patients underwent adenosine thallium imaging with the single-port system (group 1) and 140 patients underwent imaging with the double-port system (group 2). Both groups were comparable in age (67 +/- 10 years vs 64 +/- 11 years), gender (men comprised 56% of patients in group 1 and 64% in group 2), resting heart rate, and systolic blood pressure. More patients in group 1 had chest pains (57% vs 44%; p = 0.03), ST-segment depression (25% vs 9%; p = 0.005), nausea (11% vs 4%; p = 0.04), and second- or third-degree atrioventricular block (11% vs 5%; p less than 0.08) than did patients in group 2. The other side effects were similar, and peak heart rate and peak systolic blood pressure were also similar. The thallium images that used single-photon emission computed tomography were abnormal in 61% of patients in group 1 and in 65% of patients in group 2 (p = not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1992

The clinical relevance of myocardial viability in patient management.

This study examined the importance of viability as a clinical issue in 532 patients with angiographically proven CAD who underwent exercise SPECT thallium imaging. Conventional 4-hour delayed images were used to differentiate scar tissue from ischemia (20 segments per patient). There were 90 patients (17%) with normal images, 274 patients (52%) with reversible defects only, and 168 patients (31%) with scar tissue either with or without associated ischemia. The patients with scar tissue were subdivided according to the number of segments with fixed defects and the number of additional reversible defects. There were 114 patients with scar tissue alone or more scar tissue than ischemia. Contrast ventriculography in these 114 patients revealed normal wall motion or ejection fraction in 50 patients. On the basis of results of thallium imaging alone, the issue of viability was probably significant in 114 patients (21%); however, when the ventriculographic data were also included, the issue was significant in only 64 patients (12%) (p < 0.001). Thus myocardial viability is an important issue in 21% of patients with CAD when conventional thallium imaging is used, but this percentage decreases to 12% when wall motion and ejection fraction data are also included. These data may be important in considerations for the need of metabolic imaging and emerging scintigraphic techniques.

Aged↗
PubMed1992

Differentiation between primary dilated cardiomyopathy and ischemic cardiomyopathy based on right ventricular performance.

The differentiation of primary dilated cardiomyopathy from ischemic cardiomyopathy, though important, is difficult clinically and may require coronary angiography or metabolic imaging. Both patient groups have severe left ventricular dysfunction and severe wall motion abnormality. This study examined the differences in right ventricular performance between the two groups. There were 90 patients with a left ventricular ejection fraction less than 30% who had coronary angiography and multigated radionuclide angiography (MUGA). Of these, 69 had ischemic cardiomyopathy and 21 had primary cardiomyopathy. The left ventricular ejection fraction was similar; 22 +/- 6% in ischemic cardiomyopathy and 21 +/- 6% in primary cardiomyopathy. However, the right ventricular ejection fraction was higher in ischemic cardiomyopathy (38 +/- 16% versus 29 +/- 12%, p less than 0.01). There were 59 patients with right ventricular ejection fraction greater than or equal to 30%, of whom 50 patients (85%) had ischemic cardiomyopathy. The left ventricular and right ventricular volumes were determined by a count-based method. The right ventricular end-diastolic volume/left ventricular end-diastolic volume ratio was 0.57 in ischemic cardiomyopathy and 1.07 in primary cardiomyopathy (p less than 0.05). Thus assessment of right ventricular function may help differentiate primary from ischemic cardiomyopathy; a preserved right ventricular performance is highly suggestive of ischemic cardiomyopathy.

Cardiac Catheterization↗
PubMed1992

Atrioventricular block during adenosine thallium imaging.

Transient atrioventricular (AV) block has been reported during adenosine thallium imaging. This study examined the predictors and hemodynamic implications in 55 patients who had second- or third-degree AV block (group 1) and compared the results with those in 803 patients who did not have AV block (group 2). There were no significant differences in age, sex, or heart rate at baseline between the two groups. ST segment depression was observed in 25% of patients in group 1 and 16% in group 2 (p = NS). Chest pain occurred in 56% in group 1 and 44% in group 2 (p = NS). Preexisting conduction abnormalities (17% vs 16%) and treatment with digitalis (15% vs 15%) and beta-blockers (31% vs 36%) were similar in the two groups. The results of thallium imaging were abnormal in 66% in group 1 and 67% in group 2 (p = NS). Reversible thallium defects were seen in 51% in group 1 and 52% in group 2 (p = NS). The AV block appeared during the first 2 minutes of infusion in 40 patients (73%) and disappeared despite continuation of infusion in 43 (78%). The heart rate during AV block was 79 +/- 18 beats/min, and the systolic blood pressure was 127 +/- 27 mm Hg. Premature termination of adenosine infusion was required in one patient (2%). Aminophylline was used in 5% in group 1 and 2% in group 2 (p = NS). Thus AV block is transient, occurs during the early minutes of infusion, is not aggravated by digitalis or beta-blocker therapy, can be seen in patients with normal perfusion images, and is often well tolerated.

Adenosine↗
PubMed1992

Tomographic myocardial perfusion imaging with technetium-99m teboroxime during adenosine-induced coronary hyperemia: correlation with thallium-201 imaging.

Single-photon emission computed tomographic imaging with technetium-99m teboroxime during exercise has been found to be feasible and the results correlate with those obtained with thallium-201. This study examined the feasibility of this technique and compared tomographic imaging with technetium-99m teboroxime during adenosine-induced coronary hyperemia with thallium-201 imaging. With the patient positioned on the imaging table, adenosine was infused at a rate of 140 micrograms/kg per min for 6 min. At 4 min, 20 to 25 mCi (740 to 925 MBq) of technetium-99m teboroxime was injected intravenously and imaging was started as soon as the infusion was completed with use of a 180 degrees anterior arc and 32 stops at 10 s/stop (total imaging time 7.8 min). Rest images were obtained 60 to 90 min later with use of a similar dose of technetium-99m teboroxime. Exercise tomographic thallium images were obtained within 2 weeks of the teboroxime studies. In the 20 patients studied, the teboroxime images were normal in 2 (50%) of 4 normal subjects and abnormal in 15 (94%) of 16 patients with coronary artery disease; 4 of the 15 had a fixed defect and 11 a reversible defect. There was agreement between teboroxime and thallium studies in 16 patients (80%), in 319 (80%) of 400 segments and in 50 (83%) of 60 vascular segments (p less than 0.05). In two normal subjects, an apparent fixed defect involving the inferior wall was seen on the teboroxime but not the thallium images and was thought to be due to an attenuation artifact secondary to extracardiac activity in the left lobe of the liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1992

Effect of intravenous adenosine infusion on myocardial perfusion and function. Hemodynamic/angiographic and scintigraphic study.

BACKGROUND: Myocardial perfusion imaging during adenosine-induced hyperemia with dipyridamole or adenosine is an accepted method to diagnose coronary artery disease (CAD) and risk assessment. The mechanism of perfusion abnormality may be caused by disparate flow responses or coronary steal. This study examined the relation between 201Tl perfusion pattern and hemodynamic/angiographic changes during intravenous adenosine infusion. METHODS AND RESULTS: Patients with suspected CAD underwent sequential hemodynamic, coronary arteriographic, and left ventriculographic studies simultaneously with 201Tl imaging during adenosine infusion (140 micrograms.kg-1.min-1 for 6 minutes). There were 33 patients with CAD and 12 patients without CAD. The 201Tl images (using single-photon emission computed tomography) were abnormal in 31 patients with CAD (sensitivity, 94%) and normal in the patients without CAD (specificity, 100%). In patients with and without CAD, there were significant increases in heart rate and cardiac output (p less than 0.0001) and decreases in systemic vascular resistance and blood pressure (p less than 0.0001). There was a 77 +/- 38% increase in pulmonary capillary wedge pressure in normal subjects and a 125 +/- 83% increase in patients with CAD (p = 0.02). ST segment depression was observed in 11 patients with CAD (33%). In CAD patients, there was no change in percent diameter or area stenosis measured quantitatively during adenosine infusion. In 15 patients, contrast left ventriculography was repeated during adenosine infusion. In these patients, 201Tl perfusion defects were seen in 31 of 75 segments (41%) whereas only six of 75 segments (8%) developed regional wall motion abnormality (p less than 0.001); the remaining segments showed either no change or improved function. The left ventricular ejection fraction did not change significantly (73% versus 75%). CONCLUSIONS: There is a disparity between the effects of adenosine on left ventricular perfusion and function; most patients with CAD have perfusion defects whereas the global and regional systolic function remains unchanged or improves. Diastolic left ventricular dysfunction is a probable mechanism of the increase in pulmonary capillary wedge pressure.

Adenosine↗