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Biomedical subjects

M S Verani

Publications and source records attributed to M S Verani.

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

Detection of viable myocardium in segments with fixed defects on thallium-201 scintigraphy: usefulness of magnetic resonance imaging early after acute myocardial infarction.

To determine if magnetic resonance imaging (MRI) can be used to detect tissue viability in segments with persistent 201T1 defects early following acute myocardial infarction, 24 patients underwent MRI and adenosine 201T1 single photon emission computed tomography (SPECT) imaging at approximately 6 days. Infarction was demonstrated on MRI using a velocity-compensated, T2-weighted spin-echo pulse sequence. Wall thickening was assessed using a gradient-echo pulse sequence obtained in the same anatomic position. Viable myocardium was defined by MRI as a segment with increased signal intensity and preserved wall thickening. A fixed defect on the 201T1 SPECT images was defined as the absence of any redistribution 4 hours after the 201T1 infusion. Of 11 patients with redistribution on the 201T1 images in the infarction region, 10 (91%) had preserved wall thickening by MRI. Of 13 patients with fixed defects on the 201T1 images in the infarction region, 6 (46%) had preserved wall thickening by MRI. Of 7 patients with absent thickening, all had one or more segments with absent perfusion on redistribution imaging. Wall thickening tended to occur in patients who received thrombolytic therapy or who underwent revascularization procedures prior to imaging. The results of the present study suggest that spin-echo MRI with motion compensation can be used to identify viable myocardium in patients with fixed defects on 201T1 SPECT following acute myocardial infarction.

Adenosine↗
PubMed1993

Dobutamine thallium-201 tomography for evaluating patients with suspected coronary artery disease unable to undergo exercise or vasodilator pharmacologic stress testing.

OBJECTIVES: The aim of this study was to assess the feasibility, safety and diagnostic accuracy of a high dose dobutamine infusion in conjunction with thallium-201 single-photon emission computed tomography in 144 patients (72 men and 72 women with a mean age of 65 +/- 10 years) unable to perform exercise or pharmacologic vasodilator stress testing. BACKGROUND: Dobutamine increases myocardial oxygen consumption by increasing heart rate, contractility and arterial blood pressure. In addition, it causes myocardial blood flow heterogeneity and thus may be a useful stress for noninvasive detection of coronary artery disease. METHODS: Dobutamine was administered intravenously at incremental doses of 5, 10, 20, 30 and up to 40 micrograms/kg per min at 3-min intervals. After 1 min of the maximal dose, 3 mCi of thallium-201 was injected and the infusion was continued for an additional 2 min. Thallium-201 tomography was performed 5 to 10 min after termination of the infusion and 4 h later. The images were visually assessed for the presence and vascular location of perfusion defects and the extent of thallium redistribution. Coronary angiography was performed in 84 patients, with a > 50% stenosis considered significant. RESULTS: Dobutamine significantly (p = 0.0001) increased the heart rate (from 75 +/- 14 beats/min to 120 +/- 23 beats/min), systolic blood pressure (from 136 +/- 23 mm Hg to 148 +/- 35 mm Hg) and the rate-pressure product (from 10,144 +/- 2,517 to 17,858 +/- 4,349) from baseline to peak infusion rate, respectively. Most patients (75%) experienced side effects during the infusion, but 74% tolerated a dobutamine dose of 40 micrograms/kg per min and 97% a dose of 30 micrograms/kg per min. The more common side effects were typical (26%) and atypical (5%) chest pain, palpitation (29%), flushing (14%), headache (14%) and dyspnea (14%). The overall sensitivity of dobutamine tomography was 86% in the patients who underwent coronary angiography and 84% in those with single-vessel, 82% in those with double-vessel and 100% in those with triple-vessel disease. Seventy-eight percent of vessels with severe (> or = 70%) stenoses were identified with dobutamine tomography. The specificity of dobutamine tomography was 90% for patients and 86% for individual vessels. CONCLUSIONS: A high dose dobutamine infusion in conjunction with thallium tomography appears to be a well tolerated and accurate method for diagnosing coronary artery disease in patients unable to perform exercise or vasodilator pharmacologic stress testing.

Adult↗
PubMed1993

Quantitative adenosine 201Tl single-photon emission computed tomography for the early assessment of patients surviving acute myocardial infarction.

BACKGROUND: We prospectively investigated whether adenosine 201Tl tomography (SPECT) could determine the extent of coronary artery disease, the presence of jeopardized myocardium, and the risk for in-hospital cardiac events in 120 clinically stable patients early (5 +/- 3 days) after myocardial infarction. METHODS AND RESULTS: All patients had coronary angiography and SPECT in close proximity. Adenosine SPECT identified 99% of infarct-related arteries and 82% of severely stenosed (> or = 70%) noninfarct arteries. Multivessel disease was accurately predicted in 69% of patients. Sixty-five percent of stenosed noninfarct arteries had matching thallium perfusion defects, and 92% of these were reversible. The specificity of adenosine SPECT was > 90%. Thallium redistribution occurred often within infarct (59%) and noninfarct (92%) zones. The patency status of the arteries, however, did not predict the presence or extent of jeopardized myocardium. The perfusion defect size was larger (p = 0.0001) in patients with (45 +/- 18%) than in those without (22 +/- 15%) in-hospital cardiac events. Furthermore, 90% of patients with events had a > or = 20% perfusion defect compared with only 38% of those without events (p = 0.0001). The positive-predictive accuracy for developing a cardiac event was 70% when the perfusion defect size was > 30%. The ischemic defect also was larger in patients with (19 +/- 14%) than in those without (10 +/- 10%) events (p = 0.001). The positive- and negative-predictive values for developing early postinfarction angina were 43% and 91%, respectively, when the ischemic defect was > 12%. CONCLUSIONS: In selected low-risk survivors of myocardial infarction, early quantitative adenosine SPECT is safe and accurate in detecting and localizing coronary stenoses, assessing the extent of jeopardized myocardium, and determining subsequent risk for in-hospital cardiac events.

Adenosine↗
PubMed1993

Angiographic and hemodynamic determinants of myocardial ischemia during adenosine thallium-201 scintigraphy in coronary artery disease.

BACKGROUND: Myocardial ischemia attributed to coronary steal may occur in some patients receiving pharmacological coronary vasodilation. ECG ST-segment depression is a marker of myocardial ischemia in these patients, but the factors determining the presence or absence of ischemia are not well known. METHODS AND RESULTS: To examine the angiographic, hemodynamic, and scintigraphic determinants of adenosine-induced ischemic ST-segment depression in patients with coronary artery disease, we studied 65 consecutive patients (45 men and 20 women; mean age, 65 +/- 12 years) who showed reversible perfusion defects during adenosine (140 micrograms.kg-1.min-1 for 6 minutes) 201Tl single-photon emission computed tomography. Patients with prior myocardial infarction were excluded. Ischemic ST depression occurred in one third of the whole cohort (22 of 65 patients). The presence of coronary collateral vessels (p = 0.001), systolic blood pressure at baseline (p = 0.006), and adenosine-induced anginal chest pain (p = 0.011) were the only significant independent predictors of ischemic ST-segment depression by stepwise logistic regression analysis. Rate-pressure product at baseline, systolic blood pressure, heart rate, rate-pressure product, increase in heart rate, and rate-pressure product during adenosine infusion and maximal percent stenosis were variables also significantly related to ischemic ST depression by univariate analysis but were not predictive after the three primary variables were included in the regression model. Perfusion defect size, number of diseased vessels, and age did not correlate with ST-segment depression. CONCLUSIONS: The presence of collaterals, which may predispose to coronary collateral steal, is the most significant correlate of ischemic ST-segment depression during adenosine infusion. Systolic blood pressure at baseline, which may affect the myocardial oxygen supply/demand ratio and anginal chest pain induced by adenosine, are additional variables related to ischemic ST-segment depression during adenosine infusion.

Adenosine↗
PubMed1992

Thallium-201 single-photon emission computed tomography (SPECT) in the assessment of coronary artery disease.

Of all currently available techniques, thallium-201 single-photon emission computed tomography (SPECT) is the most time-tested noninvasive method for the detection of coronary artery disease (CAD). Recent pooled data show an overall sensitivity of 90% and a specificity of 70% for thallium-201 SPECT. Of patients with single-vessel coronary disease, 83% are identified by SPECT. Nearly all patients with double- and triple-vessel coronary disease (93% and 95%, respectively) are also identified. Thallium-201 SPECT imaging is also very effective in diagnosing CAD imaging is also very effective in diagnosing CAD using pharmacologic stress testing. In certain patient populations (e.g., in sedentary patients or those using anti-ischemic medications), pharmacologic stress testing with dipyridamole or adenosine may be a logical alternative to exercise testing. Moreover, many patients have physical disabilities that preclude appropriate exercise testing. Intravenous adenosine is a very potent direct coronary vasodilator, with the advantage of an ultrashort half-life, which eliminates the need to administer an antagonist in the majority of patients. In addition, the dosage of adenosine can be adjusted during the infusion, if necessary. The importance of thallium-201 SPECT during exercise or pharmacologic vasodilation transcends diagnosis, since it also plays an important role in the prognostic evaluation of patients with stable angina or postmyocardial infarction. Risk evaluation can be done with submaximal exercise electrocardiographic testing, but there is evidence that the addition of perfusion scintigraphy enhances the ability to predict future risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Disease↗
PubMed1992

Equivalence between adenosine and exercise thallium-201 myocardial tomography: a multicenter, prospective, crossover trial.

OBJECTIVES: The study was designed to compare pharmacologic and exercise stress during thallium-201 single-photon tomography in a multicenter prospective crossover trial. BACKGROUND: Both exercise and adenosine myocardial perfusion imaging have high sensitivity and specificity for detection of coronary artery disease. However, few data are available comparing these two stress tests in the same patients. METHODS: The study group consisted of 175 subjects: 55 healthy volunteers and 120 patients with suspected coronary artery disease. All subjects underwent two thallium tomographic tests performed 30 days apart, one during intravenous administration of adenosine (140 micrograms/kg per min for 6 min) and one during exercise stress. All images were computer quantified and interpreted without knowledge of the stress test performed. Interpretation agreement was assessed by kappa and Z statistics. RESULTS: Agreement on the presence of normal or abnormal tomograms by adenosine and exercise scintigraphy was 82.8% by visual analysis with kappa and Z statistics of 0.65 (p less than 0.0001) and 11.1 (p less than 0.00001), respectively. The agreement by computer quantification was 86% with kappa and Z statistics of 0.709 (p less than 0.0001) and 12.2 (p less than 0.00001), respectively. Agreement on localization of the perfusion defect to a specific coronary vascular territory varied from 82.7% to 91.4% with highly significant kappa and Z statistics (p less than 0.0001). There was a good correlation between quantified perfusion defect size by adenosine and exercise (r = 0.80, p less than 0.0001), but the values for defect size were significantly greater by adenosine scintigraphy (p = 0.0073). Adenosine side effects were frequent but transient and ceased spontaneously in most subjects within 1 to 2 min after the infusion was discontinued. CONCLUSIONS: Adenosine thallium-201 scintigraphy provides diagnostic information similar to that of exercise scintigraphy, although values for defect sizes are greater with adenosine.

Adenosine↗
PubMed1992

Relation of perfusion defects observed with myocardial contrast echocardiography to the severity of coronary stenosis: correlation with thallium-201 single-photon emission tomography.

It has been previously shown that myocardial contrast echocardiography is a valuable technique for delineating regions of myocardial underperfusion secondary to coronary occlusion and to critical coronary stenoses in the presence of hyperemic stimulation. The aim of this study was to determine whether myocardial contrast echocardiography performed with a stable solution of sonicated albumin could detect regions of myocardial underperfusion resulting from various degrees of coronary stenosis. The perfusion defect produced in 16 open chest dogs was compared with the anatomic area at risk measured by the postmortem dual-perfusion technique and with thallium-201 single-photon emission tomography (SPECT). During a transient (20-s) coronary occlusion, a perfusion defect was observed with contrast echocardiography in 14 of the 15 dogs in which the occlusion was produced. The perfusion defect correlated significantly with the anatomic area at risk (r = 0.74; p less than 0.002). During dipyridamole-induced hyperemia, 12 of the 16 dogs with a partial coronary stenosis had a visible area of hypoperfusion by contrast echocardiography. The four dogs without a perfusion defect had a stenosis that resulted in a mild (0% to 50%) reduction in dipyridamole-induced hyperemia. The size of the perfusion defect during stenosis correlated significantly with the anatomic area at risk (r = 0.61; p = 0.02). Thallium-201 SPECT demonstrated a perfusion defect in all 14 dogs analyzed during dipyridamole-induced hyperemia; the size of the perfusion defect correlated with the anatomic area at risk (r = 0.58; p less than 0.03) and with the perfusion defect by contrast echocardiography (r = 0.58; p less than 0.03). Thus, myocardial contrast echocardiography can be used to visualize and quantitate the amount of jeopardized myocardium during moderate to severe degrees of coronary stenosis. The results obtained show a correlation with the anatomic area at risk similar to that obtained with thallium-201 SPECT.

Albumins↗
PubMed1992

Effects of acute, transient coronary occlusion on global and regional right ventricular function in humans.

OBJECTIVES: The aim of this study was to investigate the changes in right ventricular function during acute coronary occlusion produced by inflating a coronary angioplasty balloon catheter. BACKGROUND: Alterations in right ventricular function are well known to occur in patients with acute myocardial infarction or ischemic cardiomyopathy. However, the changes in right ventricular function resulting from acute, transient coronary occlusion of each of the major coronary arteries have been scantily studied, perhaps because of serious limitations of currently available technology. METHODS: A newly designed, mobile, multiwire gamma camera, in combination with generator-produced tantalum-178, affords high count rate first-pass radionuclide angiography and is thus ideal for studying right ventricular function at the bedside. Accordingly, 46 patients underwent first-pass radionuclide angiography at baseline and during transient coronary occlusion induced by a coronary angioplasty balloon catheter. RESULTS: A significant, albeit modest, decrease in global right ventricular ejection fraction occurred during occlusion of the left anterior descending (from 42.9 +/- 9.3% to 39 +/- 8.7%, p < 0.05) and left circumflex (from 44 +/- 9.1% to 38.8 +/- 7.9%, p = 0.03) coronary arteries, but diagonal artery occlusion caused no significant change in right ventricular ejection fraction. Occlusion of the right coronary artery proximal (but not distal) to the acute marginal branch caused a significant decrease in right ventricular ejection fraction (from 42.6 +/- 4.7% to 35.7 +/- 7.2%, p < 0.01). Although occlusion of the left anterior descending, left circumflex and proximal right coronary arteries all caused significant deterioration in regional right ventricular function, only proximal right coronary occlusion caused right ventricular dilation (p < 0.005). CONCLUSIONS: Significant impairment of right ventricular function occurs during transient occlusion of the left anterior descending, left circumflex and proximal right coronary arteries, but only occlusion of the latter causes acute right ventricular dilation, probably as a result of ischemia.

Adult↗
PubMed1992

Quantification of left ventricular performance during transient coronary occlusion at various anatomic sites in humans: a study using tantalum-178 and a multiwire gamma camera.

To study the functional significance of transient coronary occlusion on systolic and diastolic left ventricular function relative to the anatomic site of occlusion, first-pass radionuclide angiography with a mobile multiwire gamma camera using tantalum-178 (dose activity less than or equal to 84 mCi/elution) was performed in 46 patients undergoing balloon coronary angioplasty. First-pass images were acquired immediately before angioplasty and during the last 30 s of a 60-s balloon inflation in 23 left anterior descending arteries, 18 right coronary arteries, 8 circumflex arteries and 3 diagonal coronary arteries. Occlusion of the left anterior descending artery resulted in significant decreases in left ventricular ejection fraction (54.6 +/- 12.7% to 32.3 +/- 10.6%, p = 0.0001) and peak filling rate (2.48 +/- 0.68 to 1.75 +/- 0.64 end-diastolic volumes/s, p = 0.0001), accompanied by severe abnormalities in regional function and left ventricular dilation. Right coronary artery occlusion caused inferior hypokinesia, but did not significantly change left ventricular ejection fraction (48.5 +/- 12.4% vs. 45.8 +/- 12.5%, p = NS) or peak filling rate (2.05 +/- 0.81 vs. 2.09 +/- 0.81 end-diastolic volumes/s, p = NS). Circumflex artery occlusion resulted in mild wall motion deterioration and a borderline decrease in ejection fraction (54.7 +/- 11.4% to 50.5 +/- 12%, p = 0.057). Diagonal artery occlusion did not cause significant changes in left ventricular ejection fraction or filling rate. The decrease in left ventricular ejection fraction during coronary occlusion was 9 +/- 25% and 27 +/- 22%, respectively, in those arteries with and without collateral supply (p = 0.052). These data provide strong evidence for the critical importance of the left anterior descending artery and the secondary role of the other coronary arteries in maintaining global systolic and diastolic left ventricular function and suggest a protective role of collateral vessels during coronary occlusion.

Angioplasty, Balloon, Coronary↗
PubMed1992

Exercise echocardiography versus 201Tl single-photon emission computed tomography in evaluation of coronary artery disease. Analysis of 292 patients.

BACKGROUND: Exercise echocardiography (digital cine-loop technique) and 201Tl single-photon emission computed tomography (SPECT) were performed simultaneously in 292 patients being evaluated for coronary artery disease. METHODS AND RESULTS: Pretreadmill and posttreadmill echocardiographic images of diagnostic quality were obtained in 289 patients, and the left ventricle was divided into anterior, inferior, and lateral regions. Any wall motion or perfusion abnormality observed within each region was classified as totally reversible, fixed, or partially reversible. Exercise echocardiography and SPECT were normal in 137 patients and abnormal in 118 (88% agreement). Equal numbers of regional abnormalities were detected by one test when missed by the other. The two tests had an 82% agreement in detecting the same type of finding within the regions analyzed. SPECT detected more reversible abnormalities than echocardiography, whereas echocardiography detected more fixed abnormalities than SPECT: Regions with a fixed abnormality by echocardiography frequently showed partial reversibility of a perfusion defect by SPECT: Nearly one third of regions with fixed perfusion defects by SPECT demonstrated normal resting function or reversible abnormalities by echocardiography. Sensitivity for coronary artery disease by angiography (greater than or equal to 50% diameter stenosis) in 112 patients was similar for the two tests, ranging from 58% and 61% (echocardiography and SPECT, respectively) for one-vessel disease to 94% for three-vessel disease. The specificities for echocardiography and SPECT were 88% and 81%, respectively. CONCLUSIONS: Exercise echocardiography had a diagnostic accuracy comparable to that of SPECT for the detection of regional abnormalities produced by significant coronary artery disease. A greater number of abnormal regions were detected with the combined use of both tests.

Coronary Angiography↗
PubMed1992

Significance of increased lung thallium uptake during adenosine thallium-201 scintigraphy.

To determine the relationship of lung 201Tl activity during adenosine scintigraphy to the presence and extent of coronary artery disease, we investigated 132 subjects comprising 4 groups: 36 normal volunteers, 19 patients with angiographically normal coronaries, 29 patients with single-vessel (greater than 50% luminal stenosis) and 48 patients with multivessel coronary artery disease. Lung activity was quantified relative to maximal myocardial activity in both an early anterior planar image (pretomography) and the unprocessed tomographic image in the anterior projection. A good correlation was found for the lung-to-heart ratio assessed by planar and tomographic imaging (r = 0.83, p less than 0.0001), but the ratio was higher with planar imaging. The lung-to-heart ratio in the planar images was significantly higher in patients with multivessel disease compared to those with single-vessel disease (p less than 0.05) or volunteers and subjects with normal coronary arteries combined (p less than 0.001). A lung-to-heart ratio of greater than 0.45 in the planar images (upper 95% confidence limit for the normal subjects) was found in 6 (21%) single-vessel disease and 17 (35%) multivessel disease patients. Patients with elevated lung thallium activity during adenosine infusion had more hypoperfused myocardial segments (p = 0.007), more segments with redistribution (p = 0.04) and larger initial perfusion defect size (p = 0.04) than those with normal lung activity. Thus, evaluation of lung activity during adenosine thallium scintigraphy provides supplementary information regarding the severity of coronary artery disease and extent of myocardial hypoperfusion.

Adenosine↗
PubMed1991

Diagnosis of ischemic heart disease with adenosine echocardiography.

To assess the feasibility, safety and diagnostic accuracy of adenosine infusion combined with echocardiography, 73 patients with suspected or known coronary artery disease underwent echocardiography at baseline and during a maximal intravenous adenosine infusion of 140 micrograms/kg per min. Compared with baseline values, adenosine caused an increase in heart rate, a decrease in systolic and diastolic blood pressure and a slight but significant increase in rate-pressure product. The echocardiographic images were digitized and randomly assigned in a quad-screen format for nonbiased interpretation. An ischemic response, defined as a new or worsening wall motion abnormality, developed in 25 patients; a fixed wall motion abnormality was present in 27 and no abnormality in 21. All patients underwent coronary angiography. The sensitivity of adenosine echocardiography for greater than or equal to 75% coronary artery diameter stenosis was 85% (46 of 54), with a specificity of 92% in patients with normal coronary arteries. In the 35 patients with a normal baseline electrocardiogram the sensitivity was 60%; 9 (82%) of 11 patients with multivessel disease were correctly identified. The sensitivity for adenosine electrocardiography (greater than or equal to 1-mm ST depression) was 35% with a specificity of 100%. Side effects were transient and mild; aminophylline was used in two patients. Thus, ischemic changes can be induced in patients with coronary artery disease with intravenous adenosine that, combined with echocardiography, is sensitive for the assessment of ischemic heart disease, particularly in patients with multivessel disease.

Adenosine↗
PubMed1991

Exercise thallium-201 perfusion scintigraphy in the assessment of coronary artery disease.

Exercise thallium-201 perfusion scintigraphy has been used extensively over the last decade for the detection and localization of coronary artery disease. Single-photon emission computed tomography (SPECT) is a refinement of presently available techniques, offering improved identification over planar imaging of individual vessel stenosis and quantification of the extent of abnormally perfused myocardium. In this review, the planar and SPECT techniques are discussed in light of the most recently published large patient series, and with regard to the many factors that affect the sensitivity and specificity of perfusion imaging in identifying coronary artery disease. The clinical implications of exercise perfusion scintigraphy and its future applications in cardiology practice are discussed.

Coronary Disease↗
PubMed1991

Myocardial perfusion scintigraphy during maximal coronary artery vasodilation with adenosine.

Pharmacologic coronary vasodilation as an adjunct to thallium-201 myocardial perfusion scintigraphy provides an important alternative form of stress that has been increasingly used in patients unable to perform an exercise stress test. Although dipyridamole has traditionally been used for this purpose, there are several compelling reasons why adenosine may be a preferable agent. First, dipyridamole acts by blocking the reuptake and transport of adenosine, which is the effective substance responsible for coronary vasodilation. Second, exogenous adenosine has a very short half-life (less than 2 seconds), which explains its very short duration of action as well as the brief, self-limiting duration of its side effects. Third, the adenosine infusion is controllable and may be increased or decreased as desired. Fourth, the coronary vasodilation induced by the doses of adenosine we recommend (140 micrograms/kg/min) may be more profound than that induced by the standard dipyridamole dose. Our experience to date, with nearly 1,000 patients studied, shows the adenosine thallium-201 test to be practical and well tolerated, with high sensitivity (87%) and specificity (94%) for detecting coronary artery disease.

Adenosine↗