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D D Watson

Publications and source records attributed to D D Watson.

At least 55 records · Page 3Linked to original sources
PubMed1993

Do false positive thallium-201 scans lead to unnecessary catheterization? Outcome of patients with perfusion defects on quantitative planar thallium-201 scintigraphy.

OBJECTIVES: We postulated that artifactually abnormal thallium-201 scans are well identified at the time of initial clinical interpretation by experienced readers and do not lead to unnecessary coronary angiography. BACKGROUND: Exercise thallium-201 scintigraphy employing quantitative imaging techniques has yielded sensitivity and specificity values of 80% to 90%. There are image artifacts, such as breast shadows, and variants of normal that, if not correctly identified, can lead to a high false positive rate for detection of coronary artery disease. METHODS: Data from 338 consecutive patients with one or more focal thallium-201 defects on quantitative planar images were reviewed. All patients had undergone symptom-limited exercise scintigraphy and were classified as having either artifactual or nonartifactual thallium-201 defects after review of clinical reports. RESULTS: Of the 265 patients with defects judged to be nonartifactual on clinical readings, 167 underwent coronary angiography, which demonstrated significant coronary artery disease (> or = 50% stenosis) in 161 (96%) and normal findings in 6. Four of the latter six had documented prior myocardial infarction. The remaining 73 patients (85% female) had thallium-201 defects deemed to be artifactual on clinical readings, chiefly as a result of breast (66%) and diaphragmatic (8%) attenuation or variants of normal (26%). Only 4 (5%) of the 73 patients underwent subsequent coronary angiography; none had coronary artery disease. One had aortic stenosis and two had variant angina. Follow-up (mean 20 +/- 2 months) of the 69 patients in this group who did not undergo coronary angiography revealed no deaths and one nonfatal non-Q wave myocardial infarction. CONCLUSIONS: Artifactual defects on quantitative planar thallium-201 scintigraphy are well recognized by experienced interpreters and do not result in a high false positive rate leading to unnecessary cardiac catheterization. The incidence of coronary artery disease is high in patients with thallium-201 defects judged to be nonartifactual, and many patients with perfusion defects and angiographically normal coronary arteries have organic heart disease.

Aged↗
PubMed1993

Quantitative planar rest-redistribution 201Tl imaging in detection of myocardial viability and prediction of improvement in left ventricular function after coronary bypass surgery in patients with severely depressed left ventricular function.

BACKGROUND: Although many patients with multivessel coronary artery disease (CAD) and severely depressed left ventricular (LV) function will benefit from coronary artery bypass graft surgery (CABG), surgeons may be reluctant to perform CABG on these patients without evidence of myocardial viability in regions of severe asynergy. We hypothesized that quantitative planar rest-redistribution 201Tl imaging would identify viable myocardium and predict improved regional and global function after revascularization in patients with depressed LV function and CAD. METHODS AND RESULTS: Twenty-one patients (mean LV ejection fraction, 0.27 +/- 0.05) were studied. Regional and global LV functions were evaluated before and 8 weeks after CABG with radionuclide ventriculography. Segments were prospectively classified as showing normal, mildly reduced, or severely reduced viability on the basis of quantitative analysis of defect severity and redistribution on planar resting 201Tl imaging. By 201Tl criteria, 90% of hypokinetic segments were classified with normal or mildly reduced viability. Among akinetic or dyskinetic segments, 20% had normal 201Tl uptake, 53% had mildly reduced viability, and only 27% had severely reduced viability. 201Tl viability criteria identified segments that improved function after CABG. Sixty-two percent of severely asynergic segments with normal viability and 54% with mildly reduced viability improved function after surgery, but only 23% with severely reduced viability improved function (p = 0.002). When only adequately revascularized segments were considered, the predictive value of a positive preoperative viability scan for functional improvement was 73%. The greatest improvement in global LV function after CABG occurred in patients with the greatest number of asynergic segments classified as viable before surgery (p < 0.01). In 10 patients with more than seven viable, asynergic segments, mean LV ejection fraction increased significantly after CABG (0.29 +/- 0.07 to 0.41 +/- 0.11, p = 0.002). In 11 patients with seven or fewer viable, asynergic segments, mean LV ejection fraction remained unchanged after revascularization (0.27 +/- 0.05 to 0.30 +/- 0.08, p = NS). CONCLUSIONS: In patients with CAD and severely depressed LV function, preoperative quantitative planar rest-redistribution. 201Tl imaging identifies viability in many asynergic myocardial segments, and these segments frequently improve function after CABG. The presence of numerous asynergic but viable myocardial segments before surgery correlated significantly with improvement in global LV function after bypass surgery.

Aged↗
PubMed1993

99mTc-sestamibi uptake and retention during myocardial ischemia and reperfusion.

BACKGROUND: 99mTc-methoxyisobutyl isonitrile (Sestamibi) is a new perfusion agent that has shown promise for the noninvasive detection of myocardial salvage after coronary reperfusion in acute myocardial infarction. The objective of this study was to further validate that myocardial uptake and retention of Sestamibi after reperfusion in a canine myocardial infarction model are markers of tissue viability. The hypotheses tested were that if Sestamibi is given early after reperfusion and myocardial uptake is quantitated soon afterward, the degree of ultimate myocardial salvage will be overestimated, and that there will be continued loss of myocardial Sestamibi from ischemic tissue during 3 hours of reperfusion due to accelerated release of Sestamibi from cells already irreversibly injured during the phase of coronary occlusion, reperfusion injury to myocytes still viable early after reflow, or a combination of both mechanisms. METHODS AND RESULTS: In protocol 1, 8.0 mCi Sestamibi was injected intravenously in anesthetized dogs 2-5 minutes after reperfusion preceded by 3 hours of left anterior descending coronary artery (LAD) occlusion. Animals were killed either 5 minutes (n = 7) or 3 hours (n = 9) after Sestamibi administration. Mean endocardial Sestamibi activity was 74 +/- 3% of nonischemic activity in dogs killed early and 31 +/- 2% of nonischemic activity in dogs killed late after Sestamibi administration, indicating myocardial loss of Sestamibi during 3 hours of reflow. Regional flow (percent nonischemic) at the time of Sestamibi administration (2-5 minutes after reperfusion) was comparable in dogs killed early (144 +/- 23%) and dogs killed late (118 +/- 4%, p = NS). In protocol 2, Sestamibi was given intravenously at baseline under normal conditions followed by 3 hours of LAD occlusion and either 4 (n = 6), 30 (n = 9), or 180 minutes (n = 10) of reperfusion. At postmortem, myocardial slices were imaged for quantification of defect magnitude and regional flow (radiolabeled microspheres), and tissue Sestamibi activities were determined by gamma well counting. Coronary sinus Sestamibi activity was serially measured. In these dogs, which were preloaded with Sestamibi at baseline, 3 hours of LAD occlusion followed by 3 hours of reperfusion resulted in a loss of Sestamibi in the endocardial zone of the ischemic region to 40 +/- 6% of nonischemic levels (p < 0.0001). This loss corresponded to a sustained elevation of coronary sinus activity throughout the reflow period. The loss of myocardial Sestamibi was significantly greater than that observed in dogs killed 4 or 30 minutes after reflow. Defect magnitude also worsened over 3 hours of reperfusion as assessed by gamma camera imaging of slices of the excised hearts. CONCLUSIONS: These experimental data suggest that Sestamibi uptake and retention are dependent on myocardial viability as well as regional flow. If Sestamibi is administered early after reperfusion and imaging is performed soon afterward, the degree of myocardial salvage could be significantly overestimated.

Animals↗
PubMed1993

Role of quantitative planar thallium-201 imaging for determining viability in patients with acute myocardial infarction and a totally occluded infarct-related artery.

We studied 57 patients with a recent infarction and an occluded infarct-related artery to test the hypothesis that the amount of 201Tl on delayed planar images correlates with the extent of viable myocardium after acute myocardial infarction. There was a significant (p < 0.001) correlation between mean 201Tl activity in the infarct zone and regional wall motion score in that zone both at baseline (r = -0.60, n = 57) and 1 mo after attempted angioplasty (r = -0.67, n = 48), with better function being associated with greater 201Tl uptake in the delayed images. There was no correlation between the number of segments showing redistribution and the wall motion score. We conclude that in patients with recent myocardial infarction and an occluded infarct-related artery, the average 201Tl activity within the infarct zone on delayed planar imaging correlates well with the extent of viable myocardium in that zone. The presence or absence of redistribution does not influence these results.

Adult↗
PubMed1992

Myocardial thallium-201 scintigraphy for assessment of viability in patients with severe left ventricular dysfunction.

Many patients with ischemic heart disease and depressed left ventricular (LV) function have asynergic zones with sustained microcirculatory perfusion and myocardial metabolic activity that exhibit improved systolic function after coronary revascularization. The 2 predominant noninvasive techniques used to determine myocardial viability in patients with severely depressed LV function are thallium-201 (201Tl) scintigraphy and positron emission tomography (PET). Myocardial extraction of 201Tl is unaltered under experimental conditions of myocardial stunning or short-term hibernation (characterized by decreased flow and ischemic dysfunction). Akinetic or dyskinetic LV wall segments can exhibit normal or near normal 201Tl uptake as long as some residual flow is present. 201Tl scintigraphy can identify viable asynergic segments when performed on patients with severe coronary artery disease who are in the resting state. Many of these patients have initial resting defects that demonstrate delayed redistribution, or mild persistent defects that show improved perfusion and function after revascularization. There is a direct correlation between the extent of 201Tl uptake in zones of severe regional myocardial asynergy and the magnitude of improvement in resting LV ejection fraction after coronary bypass surgery. Rest 201Tl scintigraphy may help in the selection of patients with coronary artery disease and severely depressed LV function who would benefit the most from revascularization.

Animals↗
PubMed1992

ST-segment depression during dipyridamole infusion, and its clinical, scintigraphic and hemodynamic correlates.

The goal of this study was to determine whether dipyridamole-induced ST-segment depression reflects more severe or extensive myocardial hypoperfusion than the absence of this electrocardiographic finding. The clinical, hemodynamic and scintigraphic correlates of ST-segment depression during intravenous dipyridamole infusion were studied in 204 consecutive patients undergoing dipyridamole stress thallium-201 (Tl-201) imaging for evaluation of coronary artery disease. Of 182 patients with a diagnostic baseline electrocardiogram, 28 (15%) developed ST depression after dipyridamole. Patients with ST depression, compared with those without, were older (64 +/- 1 vs 60 +/- 1 years; p less than 0.03) and had a higher frequency of chest pain (57 vs 23%; p less than 0.001) and a higher heart rate-blood pressure product (12.7 +/- 0.6 vs 11.2 +/- 0.2 x 10(3); p less than 0.008) after dipyridamole. Patients with ST depression were more likely to have Tl-201 redistribution (64 vs 38%; p less than 0.02) and a greater number of redistribution defects (2.3 +/- 0.04 vs 0.9 +/- 0.1, p less than 0.001) than were those without ST depression. By multivariate logistic regression analysis, the most powerful correlate of ST depression was the number of segments having Tl-201 redistribution (p less than 0.001). Other independent correlates were presence of chest pain, heart rate at Tl-201 injection, and age. Thus, the determinants of dipyridamole-induced ST-segment depression include the scintigraphic extent of reversible hypoperfusion, as well as indexes of myocardial oxygen demand.

Aged↗
PubMed1992

Effects of intracoronary dipyridamole infusion on regional myocardial blood flow and intrinsic thallium-201 washout in dogs with a critical coronary stenosis.

Intravenous dipyridamole (DP) infusion produces a significant endocardial-to-epicardial flow gradient distal to a critical coronary stenosis, resulting in diminished regional thallium-201 (Tl-201) uptake and washout. Intravenous DP can also produce a significant decrease in arterial blood pressure and therefore in coronary perfusion pressure. We determined to further clarify the mechanism of this transmural coronary "steal" employing intracoronary DP administration, thereby avoiding systemic hypotension. In five of eight dogs with a critical left anterior descending (LAD) stenosis, intracoronary DP caused no significant fall in systemic arterial pressure, a rise in epicardial flow from 1.15 +/- 0.2 to 1.75 +/- 0.2 ml/min/gm, and a slight fall in subendocardial flow from 1.15 +/- 0.2 to 1.03 +/- 0.5 ml/min/gm. Intracoronary DP caused no prolongation of the intrinsic Tl-201 washout rate. In three dogs that developed systemic hypotension after intracoronary DP, endocardial flow fell from 1.14 to 0.63 ml/min/gm, the epicardial/endocardial flow ratio fell to 0.35, and Tl-201 washout became more prolonged. Thus intracoronary DP in the setting of a critical LAD stenosis caused minimal endocardial-to-epicardial steal and had no effect on the intrinsic Tl-201 washout rate unless it was accompanied by a fall in systemic arterial pressure. The magnitude of the transmural steal was substantially less than reported in our previous experiments utilizing intravenous DP infusion. This study provides a further insight into the mechanism of DP-induced subendocardial ischemia and suggests that systemic hemodynamic alterations play an important role in the effects of the vasodilator on myocardial blood flow and Tl-201 kinetics.

Animals↗
PubMed1992

Influence of subendocardial ischemia on transmural myocardial function.

The relationship between regional myocardial perfusion and function under ischemic conditions was examined by using a nontraumatic single-crystal pulsed Doppler system that permits complete transmural assessment of myocardial thickening. Sixteen open-chest dogs underwent either 50 (n = 4) or 180 (n = 12) min of partial coronary artery occlusion. Simultaneous measurements of myocardial thickening fraction (TF) and microsphere-determined blood flow (BF) were taken in the subepicardial, midwall, and subendocardial thirds of the left ventricular wall. During ischemia, there was an excellent correlation between BF and TF in the subendocardium. Mean subendocardial BF was reduced to 0.45 +/- 0.3 ml.min-1.g-1, resulting in a subendocardial TF of 0.8 +/- 19%. Although subepicardial BF was relatively preserved at 1.03 +/- 0.4 ml.min-1.g-1, subepicardial TF was diminished markedly and not significantly different from subendocardial TF. Subepicardial and midwall TF were highly dependent on subendocardial flow rather than on the actual flow in these areas. Hence these studies show a marked dependence of transmural myocardial function on subendocardial blood flow. Outer wall function is more dependent on subendocardial than subepicardial blood flow.

Animals↗
PubMed1992

Blinded evaluation of planar technetium-99m-sestamibi myocardial perfusion studies.

Sestamibi planar myocardial perfusion studies were performed at Hotel-Dieu de Montreal on 28 patients with documented coronary artery disease and 16 normal subjects. Stress and rest studies were performed on separate days. These studies were sent to Virginia for interpretation while blinded as to age, sex, and other clinical information. Studies were quantitated independently by two operators (using a computer program modified for Sestamibi), and interpreted independently by two experienced interpreters. Computer quantitation of 2816 segments gave an average interoperator deviation of 2.2%. Pure quantitative criteria were applied for computer interpretation. By varying the detection threshold, we produced the entire ROC curve relating sensitivity and specificity as a function of detection threshold. Using only computer criteria for normal or abnormal, interoperator agreement by patient was 98% and 93% by view. The computer could achieve equal positive and negative predictive accuracy of 87%. Interpreters, allowed both quantitative and subjective judgment, agreed on 91% of 44 patients, 90% of 132 views, and 92% of 660 segments. Interpreters averaged 94% positive and 86% negative predictive accuracy.

Adult↗
PubMed1991

Physiological basis of myocardial perfusion imaging with the technetium 99m agents.

In recent years, several technetium 99m-labeled myocardial perfusion agents have been under investigation to determine their utility in assessing regional myocardial blood flow and cellular viability. 99mTc sestamibi (2-methoxyisobutyl isonitrile), one of the most promising of these agents, is a lipophilic cation that is sequestered largely within mitochondria by the large negative transmembrane potential. Experimental studies have shown that this agent is taken up in the myocardium in proportion to blood flow, but like other diffusible radionuclides underestimates flow at high flow rates. Fractional extraction (Emax) for 99mTc sestamibi is lower than that for thallium 201, but net myocardial uptake is comparable between the two radionuclides. Compared with 201Tl, 99mTc sestamibi does not significantly redistribute. Studies have shown that 99mTc sestamibi uptake after reperfusion, preceded by varying periods of coronary occlusion, reflects the degree of myocardial salvage and viability. 99mTc teboroxime, another promising new perfusion agent, is a boronic acid adduct of technetium dioxime complexes. Emax of 99mTc teboroxime is higher than Emax for 201Tl, but myocardial washout is very rapid (half-life = 21 minutes). Myocardial uptake is proportional to regional flow as found with 99mTc sestamibi and 201Tl.

Coronary Circulation↗
PubMed1991

Value of planar 201Tl imaging in risk stratification of patients recovering from acute myocardial infarction.

Although exercise ECG testing has been shown to have important prognostic value after acute myocardial infarction, exercise 201Tl scintigraphy offers several potential advantages, including: 1) increased sensitivity for detecting residual myocardial ischemia; 2) the ability to localize ischemia to a specific area or areas subtended by a specific coronary artery; 3) the ability to identify exercise-induced left ventricular dysfunction, which is manifested by increased lung uptake or transient left ventricular dilation; and 4) more reliable risk stratification of individual patients. The more optimal prognostic efficiency of 201Tl scintigraphy partially results from the fact that the error rate in falsely classifying patients as low risk is significantly smaller with 201Tl scintigraphy than with stress ECG. Because of these substantial advantages, there seems to be adequate rationale for recommending exercise perfusion imaging rather than exercise ECG alone as the preferred method for evaluating mortality and morbidity risks after acute myocardial infarction.

Angiography↗
PubMed1991

A model to predict multivessel coronary artery disease from the exercise thallium-201 stress test.

PURPOSE: The aim of this study was to (1) determine whether nonimaging variables add to the diagnostic information available from exercise thallium-201 images for the detection of multivessel coronary artery disease; and (2) to develop a model based on the exercise thallium-201 stress test to predict the presence of multivessel disease. PATIENTS AND METHODS: The study populations included 383 patients referred to the University of Virginia and 325 patients referred to the Massachusetts General Hospital for evaluation of chest pain. All patients underwent both cardiac catheterization and exercise thallium-201 stress testing between 1978 and 1981. RESULTS: In the University of Virginia cohort, at each level of thallium-201 abnormality (no defects, one defect, more than one defect), ST depression and patient age added significantly in the detection of multivessel disease. Logistic regression analysis using data from these patients identified three independent predictors of multivessel disease: initial thallium-201 defects, ST depression, and age. A model was developed to predict multivessel disease based on these variables. As might be expected, the risk of multivessel disease predicted by the model was similar to that actually observed in the University of Virginia population. More importantly, however, the model was accurate in predicting the occurrence of multivessel disease in the unrelated population studied at the Massachusetts General Hospital. CONCLUSION: It is, therefore, concluded that (1) nonimaging variables (age and exercise-induced ST depression) add independent information to thallium-201 imaging data in the detection of multivessel disease; and (2) a model has been developed based on the exercise thallium-201 stress test that can accurately predict the probability of multivessel disease in other populations.

Arrhythmias, Cardiac↗
PubMed1991

Childhood retroperitoneal fibrosis associated with a horseshoe kidney: a case report.

The case of a 12-year-old girl with retroperitoneal fibrosis and a horseshoe kidney is presented. This is a relationship that has not previously been described. An in-depth review of the literature of childhood retroperitoneal fibrosis is undertaken with accompanying discussion on the etiology, symptoms, pathology, radiographic findings, treatments and prognosis of the disease.

Child↗
PubMed1991

Assessment of myocardial perfusion and viability with technetium-99m methoxyisobutyl isonitrile.

The clinical application of Tc-99m Sestamibi imaging in acute myocardial infarction should be most useful. The capability of assessing risk area during acute coronary occlusion and degree of myocardial salvage after reperfusion offers a noninvasive means to assess the benefit of therapeutic interventions aimed at reducing myocardial ischemic injury. Further studies in larger numbers of patients appear warranted to identify the precise worth of this new imaging technique relative to other existing noninvasive imaging methodologies in clinical practice.

Animals↗
PubMed1990

Prevalence and correlates of increased lung/heart ratio of thallium-201 during dipyridamole stress imaging for suspected coronary artery disease.

There is little information concerning the prevalence and clinical correlates of increased pulmonary thallium-201 uptake during dipyridamole thallium-201 stress imaging. Accordingly, the clinical characteristics and quantitative thallium-201 findings were correlated with quantitative lung/heart thallium-201 ratio in 87 patients undergoing dipyridamole thallium-201 stress testing. Nineteen patients (22%) had an elevated ratio (greater than 0.51). These patients were more likely to have had an infarction, to be taking beta blockers, and have a lower rate-pressure product after dipyridamole administration than those with a normal ratio (p less than 0.03). An elevated ratio was associated with a greater likelihood of initial, redistribution and persistent defects, as well as left ventricular cavity dilatation on thallium-201 imaging (p less than 0.05). In addition, the number of myocardial segments demonstrating initial, redistribution and persistent defects was also greater in patients with increased ratios (p less than 0.03). Multivariate analysis demonstrated that the presence of redistribution and left ventricular cavity dilatation were the most significant correlates of lung/heart thallium-201 ratio. It is concluded that the prevalence of increased lung/heart thallium-201 ratio with dipyridamole thallium-201 stress imaging is similar to that seen with exercise stress imaging. As with exercise thallium-201 imaging, increased pulmonary thallium-201 uptake may be a marker of functionally more significant coronary artery disease.

Adult↗
PubMed1990

Technical aspects of myocardial planar imaging with technetium-99m sestamibi.

Fundamental quantitative planar imaging techniques, evolved over the years, have been adapted to maximize the efficiency and clinical effectiveness of technetium-99m (Tc-99m) sestamibi imaging. To ensure reproducible image interpretation, the Society for Motion Picture and Television Engineers test pattern is used to obtain the necessary standardization of video and hard copy images. A standardized intensity scale intuitively relates count density to perceived brightness. Data are accumulated via standard 16-frame multiple gated acquisition and can be viewed in cine mode to assess wall motion. The images are then automatically summed for quantitative analysis of myocardial perfusion. Excessive extracardiac Tc-99m activity is automatically suppressed by the computer program to prevent suboptimal display of the heart. Due to the difference in heart background ratio and shape of the extracardiac background between resting and exercise Tc-99m sestamibi images, a modified interpolative background subtraction algorithm was developed. Image registration is necessary for accurate comparison of the rest and exercise images to detect redistribution. This is automatically accomplished by adjusting the position of the background-subtracted and centered images so as to maximize the cross-correlation coefficient. Profiles are generated to sample the myocardial count distribution and can be compared to a normal database, subject to confirmation by a competent interpreter. Rest redistribution is defined by a change in the myocardial distribution of Tc-99m sestamibi between exercise and rest images. Flashback display is used to identify subtle regions of redistribution that often signify residual viability within an infarct zone.(ABSTRACT TRUNCATED AT 250 WORDS)

Heart↗
PubMed1990

Effects of dipyridamole and aminophylline on hemodynamics, regional myocardial blood flow and thallium-201 washout in the setting of a critical coronary stenosis.

Experiments were performed to characterize the interaction of intravenous dipyridamole and aminophylline on thallium-201 transport kinetics, regional myocardial blood flow and systemic hemodynamics in the presence of a critical coronary artery stenosis. In 12 dogs with a critical left anterior descending coronary artery stenosis, arterial pressure decreased from a mean value (+/- SEM) of 107 +/- 6 to 94 +/- 3 mm Hg (p less than 0.05) and distal left anterior descending artery pressure decreased from 70 +/- 7 to 55 +/- 4 mm Hg (p less than 0.05) after intravenous administration of dipyridamole (0.25 mg/kg body weight). In the left anterior descending perfusion zone, the endocardial/epicardial flow ratio decreased from 0.70 to 0.36 and the intrinsic thallium washout rate was significantly prolonged. Intravenous aminophylline (5 mg/kg) reversed the dipyridamole-induced systemic hypotension and transmural coronary steal and restored the thallium washout rate to baseline values. In six other dogs, aminophylline alone resulted in no alterations in systemic and coronary hemodynamics or regional myocardial blood flow. As expected, dipyridamole-induced vasodilation and coronary steal were prevented by aminophylline pretreatment. These data show that in a canine model of partial coronary stenosis, systemic hypotension, adverse regional flow effects (coronary steal) and prolonged thallium-201 washout consequent to intravenously administered dipyridamole are promptly reversed by intravenous aminophylline administration. Aminophylline alone had no significant hemodynamic and coronary flow effects. This study provides further insight into the altered thallium kinetics occurring as a consequence of dipyridamole-induced vasodilation and suggests that the prompt reversal of symptoms and signs of ischemia with aminophylline in patients receiving intravenous dipyridamole for clinical imaging studies probably reflects the reversal of transmural coronary steal.

Aminophylline↗