Biomedical subjects

T F Christian

Publications and source records attributed to T F Christian.

72 records · Page 4Linked to original sources

PubMed1992

Noninvasive identification of severe coronary artery disease using exercise tomographic thallium-201 imaging.

The ability of exercise thallium-201 tomographic imaging to predict the presence of left main or 3-vessel coronary artery disease (CAD) was examined in 688 patients who underwent both exercise thallium-201 testing and coronary angiography. Significant differences existed for multiple variables between patients with (n = 196) and without (n = 492) severe left main or 3-vessel CAD. Logistic regression analysis identified 4 variables as independently predictive of left main or 3-vessel CAD. These variables were the magnitude of ST-segment depression with exercise, the number of visually abnormal short-axis thallium-201 segments, the presence or absence of diabetes mellitus, and the change in systolic blood pressure with exercise. Using these variables, patients were classified by nomograms into low-, intermediate- and high-probability groups. Patients at high probability (n = 205) had a 52% prevalence of 3-vessel or left main CAD, whereas those at low probability (n = 170) had only a 12% prevalence. Only 53 patients (29%) with 3-vessel or left main CAD had perfusion abnormalities in all 3 coronary territories. Clinical and exercise parameters provide important independent information in the identification of left main or 3-vessel CAD by exercise thallium-201 tomographic imaging, because thallium scintigraphy alone is suggestive of extensive CAD in few patients.

Aged↗

PubMed1992

Determinants of infarct size in reperfusion therapy for acute myocardial infarction.

BACKGROUND: Experimental animal studies have demonstrated that myocardium at risk, residual collateral flow, and duration of coronary artery occlusion are important determinants of final infarct size. The present study examined these variables in patients with acute myocardial infarction in relation to final infarct size. METHODS AND RESULTS: Myocardium at risk was assessed with hexakis(2-methoxyisobutyl isonitrile) technetium (I) (99mTc sestamibi) in 89 patients with first-time myocardial infarction (anterior, 48 patients; inferior, 41 patients). All patients had successful reperfusion therapy with either intravenous thrombolysis (32 patients) or primary coronary angioplasty (57 patients) within 24 hours of the onset of chest pain (4.7 +/- 3.9 hours; range, 0.5-21.5 hours) documented by coronary angiography. 99mTc sestamibi was injected intravenously before reperfusion therapy, and tomographic imaging was performed 1-6 hours later. Myocardium at risk was quantitated for each patient and expressed as a percentage of the left ventricle: 35 +/- 19%; range, 2-73%. Collateral flow was estimated by both invasive and noninvasive methods. Fifty-three patients with TIMI grade 0 or I flow who underwent primary coronary angioplasty had collateral flow graded angiographically (0-3) before the first balloon inflation. All patients had collateral flow estimated noninvasively from the acute sestamibi short-axis profile curve by three methods that assess the severity of the perfusion defect. Each of these three methods was significantly associated with angiographic collateral grade. Final infarct size was determined at hospital discharge by a second sestamibi study (17 +/- 17%; range, 0-59%). Myocardium at risk (r = 0.61, p less than 0.0001), angiographic collateral grade (p = 0.0003), and radionuclide estimates of collateral flow (r = 0.69-0.70, all p less than 0.0001) were all significantly associated with final infarct size. The time to reperfusion therapy was not significantly associated with final infarct size by univariate analysis (r = 0.18, p = 0.10). Two multivariate models were constructed to determine which variables were independently associated with final infarct size. In the invasive model, myocardium at risk, angiographic collateral grade with an interaction term for infarct location, and time to reperfusion were all independently significant and accounted for 70% of the variability in final infarct size. The noninvasive model, which substituted a radionuclide estimate of collateral flow for angiographic collateral grade, showed nearly identical results, accounting for 68% of the variability in infarct size in patients where the infarct artery was known to be occluded. When all patients were included (patients with and without acute angiography), the noninvasive model accounted for 59% of the variability in infarct size. CONCLUSIONS: Myocardium at risk, collateral flow, and duration of coronary occlusion are each independently associated with final infarct size and account for most of its variability. Ideally, all three parameters should be examined in evaluation of the efficacy of new treatment strategies for acute myocardial infarction.

Adult↗

PubMed1992

Serial tomographic imaging with technetium-99m-sestamibi for the assessment of infarct-related arterial patency following reperfusion therapy.

The purpose of this study was to determine the relationship of changes in the severity and extent of hypoperfusion on serial tomographic 99mTc-sestamibi images with patency of the infarct related artery during acute myocardial infarction. We studied 109 patients with acute myocardial infarction using tomographic 99mTc-sestamibi imaging acutely and at 18-48 hr later. Perfusion defect extent and defect area, an index of defect severity, were measured on both studies. Both defect extent and defect area were significantly (p = 0.0001) greater for anterior infarctions than for inferior and lateral infarctions. By two factor analysis of variance, the change in defect area varied significantly with both infarct location (p = 0.0001) and patency of the infarct-related artery (p = 0.002). The change in defect extent also varied significantly with both infarct location (p = 0.0001) and with patency of the infarct-related artery (p = 0.004). In patients with inferior myocardial infarction, a change in defect extent or defect area of greater than 4% or 0.017, respectively, had a positive predictive accuracy of 96% and 93%, respectively, for the identification of a patent infarct artery. Therefore, sequential changes on tomographic 99mTc-sestamibi images are of potential value for the noninvasive assessment of patency of the infarct-related artery.

Adult↗

PubMed1991

Relation of left ventricular volume and function over one year after acute myocardial infarction to infarct size determined by technetium-99m sestamibi.

Twenty patients with a first acute myocardial infarction (AMI) (15 anterior, 5 inferior) who received successful reperfusion therapy underwent tomographic imaging with technetium-99m (Tc-99m) sestamibi and radionuclide ventriculography at discharge, 6 weeks, and 1 year after AMI. Patency of the infarct-related artery after reperfusion (thrombolysis, 8 patients; coronary angioplasty, 12 patients) was confirmed by angiogrpahy in all patients. Tc-99m sestamibi perfusion defect at discharge (a measure of infarct size) was quantitated using previous methods and expressed as a percentage of the left ventricle (28 +/- 19%, range 0 to 59%). This perfusion defect size correlated closely with ejection fraction at discharge (r = -0.87), 6 weeks (r = -0.81) and at 1 year (r = -0.78, all p less than 0.0001). Perfusion defect size at discharge also correlated closely with end-systolic volume index at discharge (r = 0.71, p less than 0.0005), 6 weeks (r = 0.63, p less than 0.005) and at 1 year (r = 0.76, p less than 0.0001). Perfusion defect size at discharge did not correlate significantly with end-diastolic volume index at discharge or at 6 weeks, but did correlate at 1 year (r = 0.66, p less than 0.005). There was no significant group change in end-systolic or end-diastolic volume indexes from discharge to 1 year later, although 7 patients had definite individual changes in end-diastolic volume index (3 increased and 4 decreased). There was no relation between defect size and late changes in end-systolic volume index, but there was a weak correlation between defect size and late changes in end-diastolic volume index (r = 0.42, p = 0.07).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Limitations of the electrocardiogram in estimating infarction size after acute reperfusion therapy for myocardial infarction.

OBJECTIVE: To assess the ability of the 12-lead electrocardiogram to estimate infarction size after reperfusion therapy for acute myocardial infarction. DESIGN: The presence or absence of Q waves and the Selvester QRS score obtained before and after hospital discharge were compared with radionuclide estimates of infarction size and ejection fraction at discharge and 6 weeks later, regional wall motion at discharge and 6 weeks later, and myocardial perfusion defect size quantitated with Tc-99m-sestamibi at discharge. SETTING: A tertiary referral center. PATIENTS: A consecutive series of 43 patients with acute myocardial infarction who received acute reperfusion therapy and were assessed using 12-lead electrocardiography, radionuclide angiography, and Tc-99m-sestamibi tomographic imaging before discharge. INTERVENTIONS: All 43 patients received acute reperfusion therapy: 21 patients received intravenous tissue plasminogen activator, and 22 patients underwent primary percutaneous transluminal coronary angioplasty. MAIN OUTCOME MEASURE: The correlation of QRS score and Q waves with three radionuclide estimates of infarction size. RESULTS: A significant correlation was found between myocardial perfusion defect size at discharge and both left ventricular ejection fraction and regional wall motion at discharge and 6 weeks later (r = -0.71 to -0.81; all comparisons, P less than 0.001). Little correlation was found between electrocardiographic findings and radionuclide measurements of left ventricular function and perfusion. Presence or absence of Q waves at discharge was not associated with any difference in ejection fraction, regional wall motion, or perfusion defect at discharge. No correlation was found between QRS score and ejection fraction or myocardial perfusion defect size at discharge. The QRS score at discharge correlated only weakly with regional wall motion at discharge and 6 weeks later. This lack of correlation was unchanged when electrocardiograms obtained after hospital discharge were analyzed. CONCLUSION: Although inexpensive and readily available, the 12-lead electrocardiogram does not appear to provide a reliable estimate of infarction size after reperfusion therapy for acute myocardial infarction.

Adult↗

PubMed1991

Effect of infarct location on myocardial salvage assessed by technetium-99m isonitrile.

To investigate the influence of infarct location on myocardial salvage, technetium-99m isonitrile was injected into 43 patients with a first myocardial infarction before early reperfusion therapy. Primary coronary angioplasty was performed in 22 patients and successful intravenous thrombolytic therapy was given to 15 patients, both within 6 h of the onset of chest pain. Patency of the infarct-related artery was confirmed by angiography in all 37 patients. In the remaining six patients (three with and three without early thrombolytic therapy) the infarct-related artery remained occluded. Single photon emission computed tomography was performed within 6 h of the administration of technetium-99m isonitrile and repeated at the time of hospital discharge. Radionuclide ejection fraction at discharge was significantly lower for patients with anterior infarction (0.41 +/- 0.12) than for those with inferior infarction (0.56 +/- 0.09, p less than 0.001). Early perfusion defect size, a measure of myocardium at risk, was greater in patients with anterior than in those with inferior infarction (52 +/- 9% vs. 18 +/- 10% of the left ventricle, p = 0.0001) as was final defect size (30 +/- 20% vs. 9 +/- 8%, p less than 0.01). The change in myocardial perfusion, an estimate of myocardial salvage, was also greater in patients with anterior infarction (24 +/- 16% vs. 10 +/- 7%, p less than 0.01). However, the proportion of jeopardized myocardium salvaged (salvage index) was not significantly different between patients with anterior or inferior infarction (0.49 +/- 0.34 vs. 0.59 +/- 0.35, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Noninvasive identification of myocardium at risk in patients with acute myocardial infarction and nondiagnostic electrocardiograms with technetium-99m-Sestamibi.

BACKGROUND: Patients who have chest pain without electrocardiographic ST elevation are not candidates for thrombolytic therapy in most clinical trials. This study examined the value of technetium-99m-Sestamibi tomographic imaging to assess myocardial perfusion in patients during chest pain without ST elevation. METHODS AND RESULTS: Tc-99m-Sestamibi was injected in 14 patients who had chest pain without ST elevation, who subsequently developed enzymatic evidence of myocardial infarction within 24 hours. Tomographic imaging was performed 1-6 hours after injection. Thirteen of 14 patients showed significant perfusion defects indicative of acute myocardial infarction consistent with absent perfusion (20 +/- 15% of the left ventricle; range, 2-53%); one patient had normal images. Because of the absence of definitive electrocardiographic changes, only five patients received reperfusion therapy within 6 hours of the onset of chest pain. Regional wall motion abnormalities were present in nine of nine patients undergoing contrast ventriculography and correlated with the location of the Tc-99m-Sestamibi perfusion defect. At the time of subsequent coronary angiography, total arterial occlusion was present in 11 of the 14 patients. The infarct-related artery could be identified in 13 of the 14 patients. In six of these 13 patients, the left circumflex was the infarct-related artery. CONCLUSIONS: Patients who have chest pain without electrocardiographic ST elevation may have arterial occlusion and significant myocardium at risk. Tc-99m-Sestamibi imaging may be of benefit in identifying these patients early so that they can be considered for acute reperfusion therapy.

Aged↗

PubMed1990

Left ventricular systolic response to exercise in patients with systemic hypertension without left ventricular hypertrophy.

Supine exercise radionuclide angiography was performed in 367 men to assess left ventricular (LV) systolic response to exercise; 58 had systemic hypertension without LV hypertrophy on a resting electrocardiogram and 309 were normotensive. All patients met the following criteria defining a low pretest likelihood of coronary artery disease: age less than 50 years; normal electrocardiographic response to exercise; absence of typical or atypical chest pain; and exercise heart rate greater than 120 beats/min. Patients taking beta-receptor blockers were excluded. There were no significant differences between hypertensive and normotensive groups in peak exercise heart rate, workload or exercise duration. However, hypertensive patients had significantly higher peak exercise systolic blood pressures and peak exercise rate-pressure products. There were no differences between patients with and without hypertension in resting ejection fraction, peak exercise ejection fraction (hypertensive patients 0.71 +/- 0.01, normotensive patients 0.70 +/- 0.05) or change in ejection fraction at peak exercise (hypertensive patients 0.07 +/- 0.01, normotensive patients 0.07 +/- 0.04). Diastolic and systolic ventricular volumes tended to be smaller in the hypertensive patients, but the difference was not statistically significant. The change in systolic volume with exercise was similar in the 2 groups (hypertensive -10 +/- 3 ml/m2, normotensive -10 +/- 1 ml/m2). In the absence of electrocardiographic evidence of LV hypertrophy, systemic hypertension does not influence LV systolic response to exercise.

Adolescent↗

PubMed1990

Mismatch of left ventricular function and infarct size demonstrated by technetium-99m isonitrile imaging after reperfusion therapy for acute myocardial infarction: identification of myocardial stunning and hyperkinesia.

Quantitation of perfusion defect size using tomographic imaging with technetium-99m-hexakis-2-methoxy isobutyl isonitrile was performed at the time of hospital discharge in 32 patients with a first myocardial infarction who underwent successful coronary reperfusion within 8 h of the onset of chest pain. Reperfusion was accomplished with thrombolysis or primary coronary angioplasty. Radionuclide angiography was performed at discharge and 6 weeks later. There was a close correlation between perfusion defect size and values for ejection fraction and regional wall motion both at discharge (r = -0.80 and -0.75, respectively) and 6 weeks later (r = -0.81 and -0.81, respectively). There was no overall group difference in ejection fraction between the value at discharge and at 6 weeks; however, five patients had a significant increase (greater than or equal to 0.08) and six had a significant decrease (greater than or equal to 0.08) in ejection fraction. In patients with a significant increase at 6 weeks, ejection fraction was significantly lower at discharge than the value predicted from perfusion defect size (0.37 +/- 0.09 measured versus 0.47 +/- 0.13 predicted, p less than 0.05) and it improved at 6 weeks to near predicted values (0.51 +/- 0.07). In patients with a significant decrease at 6 weeks, ejection fraction was significantly higher at discharge than the value predicted from perfusion defect size (0.60 +/- 0.10 measured versus 0.50 +/- 0.10 predicted, p less than 0.05) and it decreased at 6 weeks to near predicted levels (0.51 +/- 0.09). Left ventricular ejection fraction at the time of hospital discharge is a potentially misleading index of the efficacy of reperfusion therapy for myocardial infarction. In a significant minority (34%) of patients this index does not accurately reflect perfusion defect size, apparently because of the effects of myocardial stunning and compensatory hyperkinesia.

Female↗

PubMedDate not supplied

Comparison of reinjection thallium 201 and resting technetium 99m sestamibi tomographic images for the quantification of infarct size after acute myocardial infarction.

BACKGROUND: Both thallium 201 and technetium 99m sestamibi have been used to quantitate infarct size at rest. Exercise 201Tl scintigraphy has been shown to have powerful prognostic information after myocardial infarction. A single study using these agents that could provide data on infarct size and prognosis would be of value. The purpose of this study was to compare estimates of infarct size by use of 201Tl and 99mTc sestamibi and to correlate these measurements with left ventricular ejection fraction in patients after acute myocardial infarction. METHODS AND RESULTS: The study group consisted of 20 patients who underwent low-level 201Tl stress studies with reinjection and 99mTc sestamibi resting studies within 4 days. Acute reperfusion was attempted in 18 of 20 patients. For 99mTc sestamibi tomographic imaging, infarct size was quantitated with 60% of maximal counts per slice for five short-axis slices as described in multiple previous studies. The postreinjection delayed 201Tl images acquired 4 hours after stress were quantitated according to the same threshold method. 201Tl patient images were also quantitated with a commercially available polar map program and compared with sex-matched control subjects. Ejection fraction was determined for each patient by radionuclide ventriculography 6 weeks later. Ejection fraction was well preserved for the group: mean 0.53 +/- 0.10. Infarct size with 99mTc sestamibi was 12% +/- 13% of the left ventricle, which was significantly smaller than either method with 201Tl: threshold method, 29% +/- 18% of left ventricle; polar map method, 25% +/- 17% of left ventricle (both 201Tl estimates, p < 0.0001 vs 99mTc sestamibi; 201Tl, 70% threshold vs 201Tl polar map, p = 0.04). There was a significant correlation between infarct size with 99mTc sestamibi and that with 201Tl (r = 0.72 to 0.73; p < 0.001). Infarct size with 99mTc sestamibi, however, provided the closest correlation with ejection fraction (r = 0.81; p < 0.001), with the two 201Tl quantitative methods providing very similar correlations (r = 0.69; p < 0.001). CONCLUSIONS: Infarct size with reinjection 201Tl imaging correlates significantly with resting infarct size with 99mTc sestamibi, although it provides significantly larger estimates. Although both approaches can be combined with a same-day exercise protocol, the closer correlation of infarct size with ejection fraction at 6 weeks suggests that resting infarct size with 99mTc sestamibi may be slightly more accurate.

Aged↗

PubMedDate not supplied

Factors influencing myocardial salvage with primary angioplasty.

BACKGROUND: The purpose of this study was to evaluate the factors influencing the salvage of jeopardized myocardium in patients treated with primary angioplasty for acute myocardial infarction. METHODS AND RESULTS: This multicenter study involved 59 patients with acute myocardial infarction who underwent primary angioplasty without antecedent thrombolytic therapy and paired baseline (before angioplasty) and predischarge tomographic perfusion imaging by quantitative 99mTc-labeled sestamibi techniques for assessing the initial area at risk and eventual infarct size. Of the 59 patients who underwent primary angioplasty, Thrombolysis In Myocardial Infarction (TIMI) level 3 perfusion was restored in the infarct vessel in 54 patients (92%). On average, approximately one third of the left ventricular myocardial mass was initially jeopardized by the infarction in progress; eventual infarct size was 18% +/- 15% of the left ventricle; myocardial salvage was 16% +/- 17% of the left ventricle. Primary angioplasty salvaged 46% +/- 50% of initially jeopardized myocardium. Factors correlated with myocardial salvage included elapsed time from onset of pain to reperfusion, infarct location (anterior infarcts had more myocardial salvage than inferior infarcts), and residual flow to the infarct zone at preangioplasty baseline levels. In the five patients reperfused less than 2 hours from onset of pain, 80% of the jeopardized myocardium was salvaged. Myocardial salvage beyond 2 hours was much more variable. CONCLUSIONS: Primary angioplasty was highly effective at restoring normal perfusion in the infarct vessel and salvaging jeopardized myocardium. The myocardial salvage was highly variable and correlated with elapsed time to reperfusion, baseline residual flow to the infarct zone, and infarct location.

Adult↗

PubMedDate not supplied

The use of perfusion imaging in acute myocardial infarction: applications for clinical trials and clinical care.

The use of perfusion imaging in the acute phase of myocardial infarction has been facilitated by the introduction of technetium 99m-labeled sestamibi (99mTc-sestamibi). Because of minimal redistribution, myocardium at risk can be quantified without delaying reperfusion therapy. The use of perfusion imaging with 99mTc-sestamibi has been extensively validated in a series of important animal studies in contrast to other methods used to assess outcome from acute myocardial infarction. This has important implications regarding the assessment of reperfusion therapy. With an accurate means to define myocardium at risk, myocardial salvage can be measured for specific therapies or patient subsets. Such measures also have clinical utility for the care of individual patients. Infarct size measures with 99mTc-sestamibi are accurate and predictive of subsequent left ventricular remodeling as well as prognosis. The identification of jeopardized myocardium in patients with nondiagnostic electrocardiograms and the noninvasive prospective measurement of collateral blood flow before reperfusion therapy are two new areas where perfusion imaging has special clinical use. Because of the ability of perfusion imaging with 99mTc-sestamibi to measure most of the variables known to determine infarct size, comparative clinical trials can be accomplished by using relatively small sample sizes. This has important implications regarding the assessment of new therapies for acute myocardial infarction.

Clinical Trials as Topic↗

PubMedDate not supplied

The influence of gating on measurements of myocardium at risk and infarct size during acute myocardial infarction by tomographic technetium 99m-labeled sestamibi imaging.

BACKGROUND: Serial perfusion imaging with 99mTc-labeled sestamibi has been useful in the assessment of myocardial salvage from reperfusion therapy during acute myocardial infarction. Studies in animal models have shown that discernible perfusion defects can be created by left ventricular asynergy from partial volume effects in the setting of homogenous perfusion tracer distribution. The purpose of this study was to examine the influence of gating on serial perfusion images during acute myocardial infarction to determine the magnitude of potential partial volume effects. METHODS AND RESULTS: 99mTc-labeled sestamibi was injected into 18 patients during acute myocardial infarction and 29 patients 5 to 8 days after myocardial infarction. Tomographic imaging was acquired in gated format (16 frames per R-R cycle of the electrocardiogram) for each set of images. All frames were summed to produce ungated images. Tomographic images were quantified on three different thresholds to define the perfusion defect: 50%, 60%, and 70% of maximal counts. Severity of perfusion defects was calculated as the lowest ratio of minimum/maximum counts on five short-axis slices. Regional wall motion was assessed subjectively on the gated images by cine-loop display. Radionuclide ventriculography was performed at 6 weeks. There was a close correlation between perfusion defect size on ungated images and end-diastolic and end-systolic images independent of the quantitative threshold used (r = 0.90 to 0.93; p < 0.0001 for all correlations). Gated images provided consistently significantly greater estimates of perfusion defect size and severity by a small increment (3% to 9% of the left ventricle; p < 0.05 for all comparisons) independently of the quantitative threshold used or the time of imaging (acute or late). Ungated images provided slightly better correlations with left ventricular ejection fraction at 6 weeks independently of the quantitative threshold used and despite significant wall motion abnormalities present on both the acute and final studies. CONCLUSIONS: The differences between perfusion defect size for gated and ungated images were highly significant as a group, but the magnitude of difference was small and not clinically relevant. The larger estimates provided by end-diastolic gated images are opposite the difference expected if partial volume effects were significantly influencing perfusion defect size. Partial volume effects appear to have minimal impact on clinical tomographic imaging during acute myocardial infarction for the quantification of myocardium at risk and infarct size.

Adult↗

PubMedDate not supplied

Evaluation of a multicrystal gamma camera and rotating chair for tomographic studies of the heart.

BACKGROUND: This study evaluates the feasibility of performing tomographic studies with a multicrystal gamma camera combined with a rotating chair. METHODS AND RESULTS: Tomographic acquisitions were performed with a cardiac phantom containing eight defects of different sizes. Defect size was determined from the fraction of counts in the short-axis slices that fell below a fixed threshold value. Image contrast was determined from the ratio of minimum/maximum counts. Images of an American College of Nuclear Physicians cardiac single-photon emission computed tomographic phantom were acquired and the results were compared with those obtained from 194 centers in the United States. For cardiac studies with 201Tl and 99mTc, threshold values of 65% to 70% gave the best correlation (R2 > 0.94) between true and measured defect sizes, although the slope of the regression line was less than 0.95 for both isotopes. Small inferior defects demonstrated poor image contrast, particularly for 99mTc. Of the three defects in the American College of Nuclear Physicians phantom, the two largest were identified in the tomographic images. CONCLUSIONS: A multicrystal gamma camera system coupled with a rotating chair can be used for tomographic studies of the heart. Image quality is poorer than that seen on conventional single-photon emission computed tomographic systems, particularly for 99mTc.

Feasibility Studies↗

PubMedDate not supplied

An estimate of the prevalence of reversible left ventricular dysfunction in patients referred for coronary artery bypass surgery.

BACKGROUND: The prevalence of reversible left ventricular function through revascularization has been difficult to assess because of the referral bias inherent in patients undergoing viability-targeted preoperative testing. METHODS AND RESULTS: Rest and exercise gated equilibrium radionuclide angiography was performed in 86 patients within 6 months before and any time after coronary artery bypass. Clinical characteristics were recorded for each patient before each of the two radionuclide ventriculograms. Global left ventricular ejection fraction (LVEF) was calculated for each patient at rest. A definite change in LVEF was defined as 0.08 or more points and a probable change as 0.04 or more points. Only patients with a resting LVEF of 0.50 or less were eligible for the study. There was no significant group change in LVEF (0.39 +/- 0.08 before surgery vs 0.38 +/- 0.11 after surgery; difference not significant). However, a definite improvement in LVEF was seen in 18 patients (21%) and a probable change in an additional 10 (12%). Consequently, one third of the patients had at least a probable improvement in resting left ventricular function. These prevalences were not related to any change in medical therapy. CONCLUSION: According to a test not specifically designed to evaluate myocardial viability, the prevalence of reversible left ventricular dysfunction is not uncommon, occurring in up to one third of patients referred for coronary revascularization.

Confounding Factors, Epidemiologic↗

PubMedDate not supplied

Prognosis in patients with spontaneous chest pain, a nondiagnostic electrocardiogram, normal cardiac enzymes, and no evidence of severe resting ischemia by quantitative technetium 99m sestamibi tomographic imaging.

BACKGROUND: There are limited data addressing the outcome of patients with normal or near normal myocardial perfusion during chest pain at rest. The purpose of this study was to determine the prognosis of patients with spontaneous chest pain, a normal or nondiagnostic electrocardiogram, no enzymatic evidence of myocardial infarction, and no evidence of severe resting ischemia by quantitative technetium 99m (99mTc) sestamibi imaging. METHODS: In the study, 111 patients who fulfilled the above criteria were injected with 99mTc sestamibi during resting chest pain and were followed for a median 2.7 years. Of the patients in the study group, 58% had coronary artery disease that was documented by clinical history or coronary angiography. Tomographic 99mTc perfusion images were interpreted with a quantitative threshold technique initially developed to detect severely hypoperfused myocardium. The images were also interpreted qualitatively to detect patients with milder degrees of hypoperfused myocardium. RESULTS: During follow-up 3 patients had cardiac deaths, 5 had nonfatal myocardial infarctions, and 21 underwent revascularization procedures (13 within 3 months and 8 more than 3 months after the sestamibi study). At 3 years, survival free of cardiac death was 97%, survival free of cardiac death or myocardial infarction was 91%, and survival of cardiac death, myocardial infarction, or late revascularization was 82%. Quantitative analysis of the scans revealed that 100% of patients without fixed defects had 3-year survival free of cardiac death versus 76% of patients who had fixed defects (p < 0.001). Mild to moderate resting ischemia by qualitative interpretation of the scans was present in 20% of patients, but this did not predict outcome. CONCLUSIONS: Patients with spontaneous chest pain and nonischemic quantitative 99mTc sestamibi images were at reasonably low risk for hard cardiac events although some patients (18%) required revascularization.

Aged↗

PubMedDate not supplied

Prediction of severe coronary artery disease and long-term outcome in patients undergoing vasodilator SPECT.

BACKGROUND: Vasodilator perfusion imaging has not been extensively evaluated for predicting severe coronary artery disease (CAD) or long-term prognosis. METHODS AND RESULTS: The goals of this study were to develop a model to predict left main/3-vessel CAD in patients undergoing vasodilator thallium 201 imaging and coronary angiography (angiographic population) and to test the long-term prognostic value of this model in a separate cohort of patients who were not referred for angiography (prognostic population). In the angiographic population (n = 653) the chi2 value of the clinical model (containing the variables age, sex, and prior myocardial infarction) in the prediction of severe CAD was 32. The addition of 3 vasodilator Tl-201 variables (magnitude of ST-segment depression, summed reversibility score, and increased lung uptake) increased the model chi2 value to 114 (P <.001). Only 9% of predicted low-risk patients versus 57% of predicted high-risk patients had severe CAD. In the prognostic population (n = 521) survival rates free of cardiac death or myocardial infarction at 7 years were 91%, 73%, and 51%, respectively, for patient groups predicted to be at low, intermediate, and high risk of severe CAD (P <.001). CONCLUSIONS: Clinical and vasodilator Tl-201 variables can accurately predict the risk of severe CAD. Stress Tl-201 variables add incremental information to clinical variables. The same model also predicts patient outcome.

Adenosine↗

PubMedDate not supplied

Infarct size measured by single photon emission computed tomographic imaging with (99m)Tc-sestamibi: A measure of the efficacy of therapy in acute myocardial infarction.

BACKGROUND: Use of mortality as an end point in randomized trials of reperfusion therapy requires increasingly large sample sizes to test advances compared with existing therapy, which is already highly effective. There has been a growing interest in infarct size measurements by (99m)Tc-sestamibi SPECT (single photon emission computed tomographic) imaging as a surrogate end point. METHODS AND RESULTS: We reviewed the reports published in English regarding infarct size measurements by (99m)Tc-sestamibi. Four separate lines of published evidence support the validity of SPECT imaging with (99m)Tc-sestamibi for determination of infarct size. This end point has been used in a total of 7 randomized trials-1 single center and 6 multicenter. The end point compares favorably with left ventricular function and infarct size measurements with the use of other radiopharmaceuticals. The most important limitation of this approach is the absence thus far of a randomized trial that has shown a corresponding decrease in mortality in association with a therapy that reduces infarct size. CONCLUSIONS: SPECT imaging with (99m)Tc-sestamibi is the best available measurement tool for infarct size. It has already served as an end point in early pilot studies to evaluate potential efficacy and in dose-ranging studies. It has the potential to serve as a surrogate end point to uncover advantages of new therapies that may be equivalent to existing therapies with respect to early mortality.

Heart↗