Biomedical subjects

D D Watson

Publications and source records attributed to D D Watson.

At least 37 records · Page 2Linked to original sources

PubMed1997

Significance of slow upsloping ST-segment depression on exercise stress testing.

The supplementary value of varying degrees of upsloping ST-segment depression observed during treadmill exercise testing to the accuracy of the exercise ST-segment response for detection of ischemia was determined by employing a reversible thallium-201 (201Tl) defect as the criteria for ischemia. A group of 199 consecutive patients (168 men) with > or = 1 reversible 201Tl defects on quantitative planar perfusion imaging, and a normal group of 366 patients with normal 201Tl scans who achieved > or = 85% of age-predicted maximum heart rate were studied. Upsloping ST-segment depression was subcategorized for > or = 1.0, > or = 1.5, and > or = 2.0 mm of sustained ST-segment depression below baseline at 0.08 seconds after the J-point. If only > or = 1.0 mm of horizontal or downsloping ST-segment depression was designated as abnormal and all upsloping responses as normal, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the exercise electrocardiogram were 49% (98 of 199), 84% (281 of 336), 64% (98 of 153), 74% (281 of 382), and 71% (379 of 535), respectively. If in addition to > 1.0 mm of horizontal or downsloping ST-segment depression, > or = 2.0 mm of upsloping ST-segment depression is considered abnormal, these values were 52% (104 of 199), 81% (272 of 336), 62% (104 of 168), 74% (272 of 367), and 70% (376 of 535), respectively. If > or = 1.5 mm of upsloping ST-segment depression is considered an abnormal response, these values were 59% (117 of 199), 74% (248 of 336), 57% (117 of 205), 75% (248 of 330), and 68% (365 of 535), respectively. Finally, if > or = 1.0 mm of upsloping ST-segment depression is considered abnormal, these values were 71% (142 of 199), 56% (187 of 336), 49% (142 of 291), 77% (187 of 244), and 61% (329 of 535), respectively. Thus, if upsloping ST-segment depression is added to the criteria for a positive exercise test result, sensitivity for detection of ischemia is increased but at the expense of a fall in specificity and a significant decrease in the positive predictive value of the test.

Aged↗

PubMed1997

Predicting adverse outcome with exercise SPECT technetium-99m sestamibi imaging in patients with suspected or known coronary artery disease.

The goal of this study was to determine the ability of exercise single-photon emission computed tomographic (SPECT) technetium-99m (Tc-99m) sestamibi imaging to predict adverse events in a population with a comparable distribution of men (n = 114) and women (n = 115). Consecutive patients referred for evaluation of chest pain syndrome, known coronary artery disease, or residual ischemia after acute myocardial infarction underwent imaging using a single-headed SPECT camera. Clinical readings were reviewed and scored by independent observers as normal or abnormal. Follow-up, defined as time from scanning until an event, late revascularization, or patient response averaged 19.2 +/- 5.2 months and was 90% complete (229 of 255 patients). Cardiac death and nonfatal infarction were corroborated by chart review or physician contact. Patients were excluded from analysis if a revascularization procedure was performed within 1 month of imaging. There were 172 patients with normal scans (67%) and 83 with abnormal scans (33%). Of the patients in whom followup was obtained, 2 of 155 with normal scans (0.8%/year) and 6 of 74 with abnormal scans (5.4%/year) had cardiac events. Statistical analysis using the Kaplan-Meier survival curves suggests a significant difference in event-free survival between normal and abnormal scans. Patients with abnormal scans portended a worse outcome (chi-square = 8.04, p <0.005). Thus, exercise SPECT Tc-99m sestamibi scintigraphy is useful for prognostication in a mixed population of patients with suspected or known coronary artery disease in which women comprised 50% of the patient cohort.

Adult↗

PubMed1997

Value of gating of technetium-99m sestamibi single-photon emission computed tomographic imaging.

OBJECTIVES: The purpose of this study was to determine how frequently and for what reasons the addition of electrocardiographically gated technetium-99m (Tc-99m) sestamibi single-photon emission computed tomographic (SPECT) images add value to nongated SPECT perfusion images. BACKGROUND: Electrocardiographic gating of Tc-99m sestamibi SPECT images permits assessment of regional and global left ventricular function and may assist in differentiating attenuation artifacts from myocardial scar. METHODS: A total of 285 consecutive patients (143 women and 142 men; mean age 57.6 +/- 11.5 years) underwent gated SPECT Tc-99m sestamibi imaging (212 with exercise, 63 with dipyridamole and 10 with dobutamine). The conventional stress and rest tomograms were interpreted first by means of a 14-segment scoring system, and then the studies were reinterpreted while the gated images were viewed. RESULTS: In the total group of 285 patients, the number of "borderline" interpretations was reduced from 89 to 29. In the 137 patients with a < or = 10% pretest likelihood of coronary artery disease, the addition of gated images added significantly to the percentage of interpretations that were designated "normal" (74% [101 of 137] vs. 93% [127 of 137], p < 0.0001), due to a reduction in borderline normal and borderline abnormal readings. In 49 patients with a previous infarction or recent angiography with > or = 70% stenosis, or both, the addition of gated images changed the percentage of "abnormal" scan interpretations from 78% (38 of 49) to 92% (45 of 49). This result was not significant (p = 0.09, two-tailed), but the trend was toward a greater number of unequivocal abnormal interpretations in this subgroup. CONCLUSIONS: The addition of electrocardiographically gated Tc-99m sestamibi SPECT images to the reading of stress and rest perfusion images alone resulted in shifting the final scan interpretations to a more normal designation in patients with a low pretest likelihood of coronary artery disease, and to more abnormal defects consistent with coronary artery disease in patients with known coronary artery disease. The number of "borderline normal" and "borderline abnormal" interpretations are significantly reduced when gated SPECT images are interpreted simultaneously with stress and rest perfusion images.

Coronary Disease↗

PubMed1997

The needs of women with substance use problems: an expanded vision for treatment.

Although the number of females served in United States treatment programs for substance use has increased over the last decade, women continue to be underrepresented. This suggests that the prevalent treatment models, which tend to be male-oriented, may not provide appropriate strategies to meet women's needs. Substance use problems in women appear to be multideterminded phenomena in which genetics, familial history, psychosocial issues, and other environmental factors play contributing roles. Working from a relational theoretical model of female psychosocial development, a continuum of expanded services addressing the entire context of women's lives is discussed.

Comprehensive Health Care↗

PubMed1996

Pharmacological stress thallium scintigraphy with 2-cyclohexylmethylidenehydrazinoadenosine (WRC-0470). A novel, short-acting adenosine A2A receptor agonist.

BACKGROUND: Pharmacological stress imaging with adenosine or dipyridamole is associated with a high incidence of side effects, including hypotension, chest pain, AV conduction abnormalities, and bronchospasm. Although the desired coronary vasodilatory response is mediated primarily by the adenosine A2A receptors, these side effects result from stimulation of the A1, A2B, or A3 adenosine receptors. We hypothesized that a selective adenosine A2A receptor agonist would induce coronary vasodilatation appropriate for pharmacological stress imaging, without evoking adenosine receptor-mediated side effects. METHODS AND RESULTS: Infusions of a potent and selective A2A adenosine receptor agonist, WRC-0470 (0.1 to 3 micrograms kg-1. min-1 for 10 minutes), to five open-chest dogs produced dose-related left anterior descending (LAD) and left circumflex (LCx) coronary artery vasodilatation without altering mean arterial pressure, heart rate, left atrial pressure, or left ventricular dP/dt. In the same dogs, adenosine (300 micrograms . kg-1. min-1 for 4 minutes) produced coronary vasodilatation that was limited by significant hypotension. To determine the utility of WRC-0470 for pharmacological stress imaging, the hemodynamic responses to WRC-0470 (0.6 microgram.kg-1.min-1 for 10 minutes) and adenosine (250 micrograms.kg-1.min-1 for 4 minutes) were compared in dogs with critical LAD stenoses. 201T1 was injected at the peak WRC-0470 stress response. WRC-0470 increased LCx flow nearly fivefold but did not significantly lower mean arterial pressure. Anteroseptal defects were readily apparent in slice images from all dogs. The mean defect ratio (LAD/LCx) was 0.59 +/- 0.06. CONCLUSIONS: The potent A2A-selective adenosine receptor agonist WRC-0470 is a short-acting coronary vasodilator with potential utility for pharmacological stress perfusion imaging.

Adenosine↗

PubMed1996

Comparison of rest thallium-201 imaging and rest technetium-99m sestamibi imaging for assessment of myocardial viability in patients with coronary artery disease and severe left ventricular dysfunction.

OBJECTIVES: We prospectively compared myocardial uptake of thallium-201 (201Tl) at rest with rest technetium-99m (99mTc) sestamibi uptake in the same patients, using quantitative singlephoton emission computed tomography (SPECT). BACKGROUND: Because of only slightly delayed redistribution, 99mTc-sestamibi uptake at rest may be less than 201Tl uptake, thereby underestimating the extent of viability. METHODS: Twenty patients (2.25 stenoses per patient) with a mean left ventricular ejection fraction of 33 +/- 2% underwent early and 3-h delayed rest 201Tl SPECT, rest 99mTc-sestamibi SPECT and two-dimensional echocardiography. RESULTS: The 280 scan segments were classified as either a normal, mild reduction in viability, defined as delayed 201Tl uptake < or = 75% and > or = 5%, or a severe reduction in viability, defined as delayed 201Tl uptake < 50%. Mild and severe defects were further classified as fixed or having rest 201Tl redistribution. Comparisons by patients were made using repeated measures analysis of variance and Dunnett's multiple comparisons test to compare 99mTc-sestamibi with initial rest 201Tl and delayed 201Tl uptake. Twenty patients had at least one mild fixed defect (95 total segments). The average percent uptake in these defects for initial 201Tl, delayed 201Tl and 99mTc-sestamibi was 62.5 +/- 2.7%, 63.1 +/- 7.1% and 67.3 +/- 9.7%, respectively (p = NS). Twelve patients (27 segments) had mild redistribution defects on serial rest 201Tl imaging. The average percent uptake was 61.6 +/- 5.2% for initial 201Tl, 67.0 +/- 9.1% for delayed 201Tl and 67.7 +/- 12.4% for 99mTc-sestamibi defects. Technetium-99m sestamibi uptake was not significantly different than that for delayed 201Tl but was significantly greater than initial 201Tl uptake. Seventeen patients (52 segments) had severe fixed 201Tl defects. The average percent uptake was 38.9 +/- 7.3% for initial 201Tl, 38.3 +/- 12.2% for delayed 201Tl and 42.7 +/- 14.2% for 99mTc-sestamibi defects in these patients (p = NS). Ten patients (19 segments) had severe redistribution defects on rest 201Tl imaging. The average percent uptake was 37.0 +/- 8.5% for initial 201Tl, 42.9 +/- 8.6% for delayed 201Tl and 44.5 +/- 11.3% for 99mTc-sestamibi defects. As was seen for mild 201Tl redistribution defects, 99mTc-sestamibi uptake was significantly higher than initial 201Tl uptake, but not significantly different than delayed 201Tl uptake in these severe defects. CONCLUSIONS: Technetium-99m sestamibi uptake after injection at rest is comparable to 201Tl uptake after injection at rest in patients with severe coronary artery disease and left ventricular dysfunction, suggesting comparable worth for viability assessment.

Cell Survival↗

PubMed1996

Comparison between thallium-201 and technetium-99m-tetrofosmin uptake with sustained low flow and profound systolic dysfunction.

UNLABELLED: Technetium-99m-tetrofosmin uptake was compared to that of 201Tl in the setting of low flow and systolic dysfunction. METHODS: In nine open-chested dogs, a severe left anterior descending (LAD) coronary artery stenosis resulted in a 54.3% mean flow reduction and decreased left ventricular thickening from 21% +/- 1% to -3 +/- 2%. After 30 min, 37 MBq (1 mCi) of 201Tl and microspheres were injected and initial and 2-hr redistribution images acquired. Two hours later, 370 MBq (10 mCi) of 99mTc-tetrofosmin and microspheres were injected and an image was obtained. LAD: left circumflex (LCX) count ratios for both tracers and flows were calculated by well counting postmortem, and 201Tl and 99mTc-tetrofosmin defect magnitudes were determined by quantitative image analysis. RESULTS: LAD:LCx flow ratios were similar during 201Tl and 99mTc-tetrofosmin injections (0.48 +/- 0.04 versus 0.49 +/- 0.05, p = n.s.). Final 201Tl activity (0.66 +/- 0.04) was significantly higher than 99mTc-tetrofosmin (0.55 +/- 0.05; p < 0.05). LAD/LCx 99mTc-tetrofosmin image defect count ratio was similar to 201Tl defect count ratio on the initial rest 201Tl scan (0.57 +/- 0.03 versus 0.56 +/- 0.02, p = ns), but significantly less than 201Tl defect count ratio at 2 hr (0.57 +/- 0.03 versus 0.65 +/- 0.02, p < 0.05). CONCLUSION: In a low-flow model with profound systolic dysfunction, myocardial 99mTc-tetrofosmin uptake ( > 50%) reflective of viability was observed in the asynergic zone perfused by the stenotic LAD.

Animals↗

PubMed1995

Comparison of thallium-201 resting redistribution with technetium-99m-sestamibi uptake and functional response to dobutamine for assessment of myocardial viability.

BACKGROUND: 201Tl scintigraphy is useful for determination of viability in patients with coronary artery disease and depressed left ventricular function. Whether 99mTc sestamibi is adequate for viability detection remains controversial. The primary goal of this study was to compare 99mTc-sestamibi uptake with 201Tl uptake in canine models of sustained low flow and regional asynergy for determination of viability. A secondary objective was to compare myocardial uptake of these tracers with the functional response to low-dose dobutamine. METHODS AND RESULTS: In protocol 1, 14 open-chested, anesthetized dogs with a 50% reduction in resting left anterior descending coronary artery (LAD) flow underwent 1 hour of transient LAD occlusion followed by reperfusion through the severe stenosis. Then 1.0 mCi of 201Tl was injected, and serial imaging was performed 5 minutes and 2 hours later. After acquisition of the delayed 201Tl image, 10 mCi of 99mTc sestamibi was injected, and imaging was repeated 45 minutes later. No significant difference was seen between the 201Tl defect ratio (LAD/left circumflex coronary artery [LCx]) on redistribution images (0.62 +/- 0.02) and 99mTc-sestamibi defect ratio (0.60 +/- 0.02). Similarly, LAD/LCx activity ratios by gamma-well counting were comparable (0.62 +/- 0.02 versus 0.59 +/- 0.04) and reflected the flow decrement. Systolic thickening was -11 +/- 3% at the time of tracer injection. In protocol 2, 16 dogs underwent serial 201Tl and 99mTc-sestamibi imaging during a 50% reduction in LAD flow with no superimposed transient LAD occlusion. In this model, the 99mTc-sestamibi LAD/LCx image defect ratio (0.61 +/- 0.03) was significantly less than the 201Tl redistribution image defect ratio (0.66 +/- 0.03, P < .01). In 10 dogs, the stenosis was released, resulting in a significant increase in systolic thickening (P = .003), which increased further in response to 5 micrograms.kg-1.min-1 of dobutamine (P = .02). In contrast, thickening increased only from -7 +/- 3% to 2 +/- 4% (P = .004) in response to dobutamine infusion in the remaining 6 dogs with persistent severe LAD stenoses. In protocol 3, 5 dogs received both 201Tl and 99mTc sestamibi to compare the degree of delayed redistribution between tracers at 2 hours. The LAD/LCx microsphere flow ratios when 201Tl and 99mTc sestamibi were injected were 0.44 +/- 0.06 and 0.43 +/- 0.05 (P = NS), respectively. The LAD/LCx activity ratio by gamma-well counting was greater for 201Tl (0.56 +/- 0.08) than 99mTc sestamibi (0.50 +/- 0.07) at 2 hours of redistribution (P < .05), indicating greater redistribution for 201Tl. The LAD/LCx 99mTc-sestamibi defect ratios on serial imaging improved from 0.49 +/- 0.07 to 0.52 +/- 0.07 (P = .0005), consistent with a slight amount of 99mTc-sestamibi redistribution. In protocol 4, no difference between 201Tl and 99mTc-sestamibi defect magnitudes was seen in 4 dogs undergoing 3 hours of total LAD occlusion and ligation of visible coronary collaterals. Infarct size was 68 +/- 19% of the risk area. CONCLUSIONS: Although 99mTc-sestamibi and 201Tl defect magnitudes and regional activities were comparable in dogs with sustained low coronary flows and superimposed subendocardial infarctions and in dogs with large infarctions, approximately 5% more 201Tl than 99mTc-sestamibi uptake was observed in dogs with chronic low flow and severe systolic dysfunction. Substantial 99mTc-sestamibi uptake in asynergic zones was observed in this low-flow model, with some slight resting 99mTc-sestamibi redistribution observed on serial images. Systolic thickening was negligibly enhanced during dobutamine infusion in dogs with sustained low flow, whereas 201Tl uptake was only mildly reduced.

Animals↗

PubMed1995

Early versus late congestive heart failure after initially uncomplicated anterior wall acute myocardial infarction.

We determined the incidence and clinical, noninvasive, and angiographic variables contributing to postdischarge early (< or = 3 months) and late (> 3 months) congestive heart failure (CHF) after anterior wall acute myocardial infarction. The patient cohort consisted of 94 consecutive patients < 65 years of age who underwent predischarge exercise thallium-201 planar scintigraphy, rest radionuclide angiography, and coronary arteriography. At a mean of 49 months of follow-up, 10 of the 68 medically managed patients developed early CHF, and 10 had late CHF. The 10 patients with early CHF had significantly higher peak creatine kinase values (2,494 vs 1,032 IU/L, p = 0.01), and at discharge, a lower left ventricular (LV) ejection fraction (28 +/- 11% vs 41 +/- 11%, p < 0.02), more persistent thallium-201 defects (3.4 +/- 1.2 vs 2.1 +/- 1.2, p < 0.02), and fewer stress-induced redistribution defects (1.4 +/- 1.1 vs 0.4 +/- 1.1, p < or = 0.05) than those with late CHF. The early group had less multivessel disease (40% vs 90%, p < or = 0.03). Fifty percent (5 of 10) of patients who developed late CHF did so after a recurrent infarction compared with 10% (1 of 10) in the early CHF group (p < 0.07) and 8% in the group without CHF (p < 0.003). The 26 patients who underwent bypass surgery within 3 months had an LV ejection fraction and extent of ischemia and extent of angiographic stenoses comparable to patients with late CHF. None required hospitalization for CHF or had sustained a recurrent infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Comparison between 201Tl and 99mTc sestamibi uptake during adenosine-induced vasodilation as a function of coronary stenosis severity.

BACKGROUND: Myocardial uptake of either 201Tl or 99mTc-sestamibi (sestamibi) is known to plateau at high coronary flow rates. However, few direct comparisons have been made between these tracers to determine what effect differences in the uptake plateau for the two tracers may have on the detection of coronary stenoses of various severities. METHODS AND RESULTS: Twenty-two dogs were instrumented with flow transducers on the left anterior descending (LAD) and circumflex (LCx) arteries. In 6 nonstenotic dogs, adenosine was infused directly into the LAD, whereas 16 dogs with either critical (n = 7) or mild (n = 9) LAD stenoses received an intravenous infusion. At peak flow, 201Tl (0.5 mCi), sestamibi (5 to 8 mCi), and radiolabeled microspheres were injected simultaneously. Five minutes later, dogs were killed, and ex vivo imaging of heart slices and gamma-well counting of multiple myocardial samples was performed. Neither 201Tl nor sestamibi uptake increased in direct proportion to flow. In the 6 nonstenotic dogs, a fivefold increase in LAD flow increased 201Tl and sestamibi uptake by only 202 +/- 6% and 138 +/- 4%, respectively (P < .0001). In the dogs with critical stenosis, the ratios of stenotic to normal activity by well counting for 201Tl (0.37 +/- 0.05) and sestamibi (0.53 +/- 0.06) underestimated the microsphere-determined flow disparity (0.17 +/- 0.03) (P < .005), but the degree of underestimation was greater for sestamibi (P = .001). Similarly, in the dogs with mild stenosis, the stenotic-to-normal ratio for 201Tl (0.62 +/- 0.04) approximated the flow ratio (0.43 +/- 0.04) better than sestamibi (0.79 +/- 0.03) (P < .0001). Sestamibi defects, however, were visually identifiable on the images of the myocardial slices. By image quantification, sestamibi defect magnitude (LAD-to-LCx count ratio) in the critical stenosis group (0.62 +/- 0.05) was significantly less than in the mild stenosis group (0.80 +/- 0.02) (P < .01). CONCLUSIONS: Thus, with adenosine-induced hyperemic flow, both 201Tl and sestamibi significantly underestimated the magnitude of the flow disparity between stenotic and normal perfusion beds. The degree of underestimation was greater for sestamibi. The clinical implication of these experimental findings for vasodilator perfusion imaging remains to be determined, since factors such as greater redistribution and scatter with 201Tl could offset its advantages.

Adenosine↗

PubMed1995

New insights into the physiology of retrograde cardioplegia delivery.

Although retrograde cardioplegia (RC) is being increasingly used in clinical practice, its physiology is unclear. Because the microvascular architecture of the coronary venous system is different from that of the arterial system, we hypothesized that myocardial perfusion would be different during RC compared with anterograde cardioplegia (AC) delivery. To better understand these differences, three groups of dogs were studied during similar RC and AC flow rates. Radiolabeled microsphere-derived microvascular flow underestimated total cardioplegia flow by 66% during RC. For the same flows, the first-pass extraction fractions of 201Tl and 99mTc were significantly less during RC compared with AC despite adjusting for microsphere loss. Myocardial contrast echocardiography (MCE), however, provided an accurate estimation of AC and RC flow rates. In addition, the rate of myocardial cooling for most of the left ventricular myocardium was similar for AC and RC at the same flow rates, as long as the flow rates were brisk. It is concluded that microvascular and nutrient flows are significantly lower at the same flow rates during RC compared with AC due to loss of RC at different microvascular sites. Unlike microspheres and diffusible radioisotopes, MCE can provide a reliable measure of myocardial flow during RC delivery. Furthermore, myocardial cooling is similar in most of the myocardium during high-flow RC and AC, which suggests that the clinical benefits of RC are probably related to myocardial cooling and that substrate replenishment may be better achieved at the same flow rates and myocardial temperatures with AC rather than RC.

Air↗

PubMed1995

Needle-using practices within the sex industry. National AIDS Research Consortium.

The addicted prostitute faces a risk of AIDS from both her sexual practices and intravenous drug use. While the sexual practices of these women have been studied, much less is known about their needle-using practices. We suggest women in the sex industry are more enmeshed in the drug-using scene and occupy a more constricted set of social roles than other women. They will therefore lack the resources and have fewer opportunities to engage in safer behaviors compared to women who support themselves by other means. The analysis is based on 9,055 addicted women not in treatment. Women who trade sex for money and/or drugs are less likely to use new needles on any consistent basis or to clean old needles. They are more likely to share needles with others compared to women who support themselves by other means. Three identifiable patterns of needle-using practices emerge: indiscriminate sharing, monogamous sharing with a sexual partner, and exclusive use of new needles. To reach those engaged in promiscuous sharing, needle-swapping programs must be particularly "user friendly." Where needle-using behaviors reflect an intimate relationship, the spouse/sex partner must be engaged if change is to take place. Finally, policymakers and practitioners should capitalize on the strengths and strategies of those who report they consistently use sterile needles.

Acquired Immunodeficiency Syndrome↗

PubMed1995

Myocardial technetium-99m-teboroxime uptake during adenosine-induced hyperemia in dogs with either a critical or mild coronary stenosis: comparison to thallium-201 and regional blood flow.

UNLABELLED: Experimental studies have shown 99mTc-teboroxime to have a higher first-pass myocardial extraction, exceeding that of 201Tl with nearly linear initial myocardial uptake over a wide range of coronary flows. The goal of this study was to quantitatively compare teboroxime with 201Tl for the assessment of a regional coronary flow imbalance when administered during adenosine vasodilation in dogs with either critical or mild LAD stenoses. METHODS: Twenty-four anesthetized dogs with either critical (n = 10) or mild (n = 14) LAD stenoses were given an i.v. infusion of adenosine (300 micrograms/kg/min). When LCx flow was maximal, 201Tl, teboroxime and microspheres were simultaneously injected and the dogs were killed either 2 or 4 min later. Regional 201Tl, teboroxime activities and myocardial blood flow were determined by gamma well counting and ex vivo imaging of 99mTc-teboroxime activity in myocardial heart slices was performed. RESULTS: In both the critical and mild stenosis groups, the LAD/LCx zone ratios in dogs killed 2 min after tracer injection for both 201Tl (0.31 +/- 0.07, 0.63 +/- 0.05) and teboroxime (0.38 +/- 0.09, 0.72 +/- 0.04) significantly underestimated the microsphere flow ratio (0.18 +/- 0.05, 0.43 +/- 0.05) (p < or = 0.01), but the degree of underestimation was greater for teboroxime compared with Tl (p < or = 0.05). CONCLUSION: In dogs with either critical or mild LAD stenoses, as early as 2 min after tracer injection, the 201Tl activity ratio more accurately assessed the adenosine-induced regional flow heterogeneity than did teboroxime. These results highlight the importance of an ultra-fast imaging protocol when using teboroxime with pharmacologic stress.

Adenosine↗

PubMed1994

Hemodynamic and metabolic correlates of dipyridamole-induced myocardial thallium-201 perfusion abnormalities in multivessel coronary artery disease.

The mechanisms responsible for the development of reversible thallium-201 (TI-201) defects with dipyridamole stress in patients with coronary artery disease (CAD) is not well understood. Previous experimental animal studies have demonstrated coronary steal characterized by an absolute decrease in subendocardial flow distal to a stenosis in response to dipyridamole infusion. Accordingly, the purpose of this study was to determine if reversible TI-201 defects in response to dipyridamole infusion are reflective of myocardial ischemia or secondary to regional differences in flow reserve. Dipyridamole (0.56 mg/kg) TI-201 imaging was performed in 23 patients in whom serial electrocardiographic, hemodynamic, aortic and coronary sinus lactate, and coronary sinus adenosine measurements were obtained. All patients with CAD had TI-201 redistribution (3.8 +/- 2.0 defects/patient), and all patients without CAD had normal scans. Mean aortic pressure was similar in both groups and did not change in response to dipyridamole (non-CAD 103 +/- 11 vs CAD 99 +/- 15 mm Hg, p = NS). Pulmonary capillary wedge pressure was similar at baseline (non-CAD 11 +/- 4 vs CAD 13 +/- 5 mm Hg, p = NS) and did not change in response to the drug (non-CAD 14 +/- 3 vs CAD 15 +/- 7 mm Hg, p = NS). Lactate extraction fraction was similar at baseline (non-CAD 0.22 +/- 0.09 vs CAD 0.17 +/- 0.14, p = NS) and decreased similarly in both groups (non-CAD 0.08 +/- 0.06 vs CAD 0.05 +/- 0.12, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗

PubMed1994

Redistribution of 99mTc-sestamibi and 201Tl in the presence of a severe coronary artery stenosis.

BACKGROUND: 99mTc-labeled methoxyisobutyl isonitrile (99mTc-sestamibi) is a myocardial perfusion agent that clears slowly from the myocardium. This study evaluates the early and late myocardial distributions of 99mTc-sestamibi and 201Tl in the presence of low-flow ischemia to determine whether 99mTc-sestamibi demonstrates rest "redistribution." METHODS AND RESULTS: Low-flow ischemia was produced in 18 anesthetized, open-chest dogs by partial occlusion of the left anterior descending coronary artery. Dogs were injected intravenously with 99mTc-sestamibi, 301Tl, and radiolabeled microspheres during sustained low-flow ischemia. The hearts were excised either 20 minutes (group 1, 10 dogs) or 2.5 hours (group 2, 8 dogs) after injection for gamma well counting to evaluate the early and late myocardial distributions of these radiotracers, relative to microsphere flow. The early myocardial distributions of 99mTc-sestamibi and 201Tl were comparable and correlated with the flow deficit (group 1). We observed a significant difference in myocardial 201Tl (P = .005) and 99mTc-sestamibi (P < .0001) activities between groups 1 and 2 dogs relative to flow, suggesting some redistribution of both tracers. Myocardial slices were imaged postmortem with a gamma camera, and 99mTc-sestamibi defect intensity was quantified. There was excellent correlation (r = .97) between the early relative 99mTc-sestamibi defect intensity on postmortem images and the flow deficit (group 1). Among group 2 dogs, the correlation was good (r = .87), but the 99mTc-sestamibi defect was less severe than the flow deficit, again suggesting redistribution. CONCLUSIONS: The myocardial distributions of 99mTc-sestamibi and 201Tl early after injection are comparable and proportional to flow. Under conditions of sustained low flow, there was detectable rest "redistribution" of 99mTc-sestamibi verified by both gamma well counting and high-resolution postmortem imaging of myocardial slices. Whether this degree of 99mTc-sestamibi rest redistribution will be detectable by serial clinical imaging remains uncertain. Nevertheless, these data suggest that imaging should be delayed after the resting injection of 99mTc-sestamibi when assessing myocardial viability in the presence of a critical stenosis.

Animals↗

PubMed1994

Illicit drug injectors in three Texas cities.

In three Texas cities illicit drug injectors not in treatment were located by outreach and interviewed with a standard questionnaire. In all the cities the drug injectors were predominantly undereducated and unemployed young men from minority groups. In Dallas and Houston most were Black, while in San Antonio most were Hispanic. The most frequently reported primary drug in Houston was cocaine, but in Dallas and San Antonio it was heroin. The high needle risk for AIDS and the low rates of positive HIV antibody tests in these samples present a special window of opportunity for prevention of AIDS.

Acquired Immunodeficiency Syndrome↗

PubMed1993

Dipyridamole thallium-201 imaging versus dobutamine echocardiography for the evaluation of coronary artery disease in patients unable to exercise.

The present study used 51 patients in a prospective, crossover, blinded comparison of dipyridamole thallium-201 imaging and dobutamine echocardiography for (1) detection of coronary artery disease (CAD), (2) detection of inducible ischemia, and (3) determination of myocardial viability. The detection of CAD was based on quantitative defects on initial planar thallium-201 images and resting or inducible wall motion abnormalities on echocardiography. Detection of ischemia was based on redistribution on delayed thallium-201 images and inducible wall motion abnormality on echocardiography. The myocardium in a region with resting wall motion abnormality was considered viable if it showed either redistribution or > 50% activity on delayed thallium-201 images, and if regional function either improved or worsened on echocardiography. The tests were comparable for the detection of CAD (53 and 59%, respectively, p = 0.23). Thallium-201 was superior to echocardiography for the detection of ischemia (35 vs 14%, respectively, p = 0.01). Although the incidence of viable myocardium was equivalent by the 2 tests (100 and 96%, respectively, p = 0.99) for each abnormally moving segment in the 24 patients with resting wall motion abnormality on echocardiography, it was greater on thallium-201 imaging (98 vs 68%, p < 0.01). It is concluded that because of its better ability to detect inducible myocardial ischemia and determine viability in myocardial segments showing reduced function, dipyridamole thallium-201 imaging appears to be superior to dobutamine echocardiography for the evaluation of CAD in patients unable to exercise.

Adult↗

PubMed1993

Exercise thallium-201 scintigraphy after thrombolytic therapy with or without angioplasty for acute myocardial infarction.

Scant data are available concerning the application and results of exercise thallium-201 (Tl-201) scintigraphy after acute myocardial infarction (AMI) treated with thrombolytic therapy. The goals of this study were to determine the ability of exercise Tl-201 scintigraphy to detect inducible ischemia and to identify multivessel coronary artery disease (CAD) in 88 consecutive postinfarction patients who received thrombolytic therapy and underwent both predischarge noninvasive testing and coronary angiography. Exercise-induced Tl-201 redistribution on quantitative scintigraphy was significantly more prevalent than exercise ST-segment depression (48 vs 14%, p < 0.001). Sensitivity and specificity of exercise ST depression alone for identification of multivessel disease was 29 and 96%, respectively. Sensitivity of a remote Tl-201 defect for multivessel CAD detection was 35 and 87%, respectively--not significantly different from values for ST depression alone. When considered as a single variable, the presence of either ST depression or a remote Tl-201 defect was associated with a 58% sensitivity (p < 0.05, compared with either ST depression or Tl-201 redistribution alone), but a somewhat diminished specificity of 78%. There was no difference in extent or severity of angiographic CAD in patients with multivessel CAD with or without inducible ischemia. In conclusion, this study shows that exercise Tl-201 imaging is more sensitive than exercise Tl-201 imaging is more sensitive than exercise ST depression for detection of residual ischemia during submaximal exercise in patients who received thrombolytic therapy for AMI. The combination of the presence of either Tl-201 redistribution or ischemic ST depression was better than either variable alone for identifying patients with multivessel CAD.

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