Reversibility by dipyridamole of thallium-201 myocardial scan defects in patients with sarcoidosis

PURPOSE: In order to clarify the significance of anginal pain and myocardial thallium-201 scan defects in cardiac sarcoidosis, the pharmacologic effect of dipyridamole on myocardial perfusion was assessed by planar thallium-201 myocardial scintigraphy in patients with sarcoidosis. PATIENTS and METHODS: Thallium-201 myocardial scintigraphy was performed at rest and after 0.56 mg/kg intravenous dipyridamole during four minutes in 16 patients with sarcoidosis. The myocardial scan (45-degree and 70-degree left anterior oblique, and anterior views) was divided into 15 segments. Results were evaluated by the number of segmental defects and with a global perfusion score (from 0 to 60) by a semi-quantitative index depending on the size and severity of myocardial thallium-201 defects. RESULTS: Thirteen of the 16 patients showed partial or total reversion of their thallium-201 defects on redistribution scanning either at rest or after dipyridamole. The mean (+/- SD) number of myocardial perfusion defects that were present in all the patients decreased from 5.31 +/- 1.78 at rest to 3.25 +/- 2.52 after redistribution (p less than 0.001) and to 2.19 +/- 2.10 after dipyridamole (p less than 0.001). The mean global perfusion score increased from 53.2 +/- 3.0 at rest to 56.2 +/- 2.9 after redistribution (p less than 0.001) and to 57.2 +/- 2.7 after dipyridamole (p less than 0.001). A significant correlation (r = 0.82, p less than 0.001) was found between the increase of global perfusion score on redistribution and after dipyridamole. CONCLUSION: The reversibility of myocardial scan defects is a common finding in sarcoidosis. It makes unlikely the role of scar fibrosis or extensive confluent granulomas as a mechanism for such defects. The effect of dipyridamole suggests the presence of reversible disorders lying at the coronary microvascular level.     

Myocardial contrast echocardiography in the evaluation of myocardial perfusion in patients with left bundle branch block and coronary artery disease.

BACKGROUND: In patients with left bundle branch block (LBBB), conventional tests such as electrocardiography and myocardial scintigraphy poorly evaluate coronary artery disease. It has been reported that myocardial contrast echocardiography (MCE) is capable of identifying patients with a postinfarction contractile reserve and myocardial functional recovery, also allowing the early identification of late left ventricular remodeling. The purpose of this study was to evaluate, retrospectively, myocardial perfusion in selected patients with LBBB. METHODS: Thirty patients (mean age 56 +/- 8 years) with LBBB, 15 with normal coronary arteries at angiography and 15 with a previous myocardial infarction and a critical one-vessel residual stenosis at angiography, underwent MCE from June 2000 to May 2001. MCE results were compared with rest thallium-201 myocardial scintigraphy. RESULTS: Among 15 LBBB patients with normal coronary arteries, MCE demonstrated normal perfusion in 14 patients, whereas 1 subject showed an impairment of septal perfusion. In the same group, rest thallium-201 myocardial scintigraphy showed an impaired septal perfusion in 14 patients, whereas 1 subject had a normal perfusion (MCE specificity 93% vs myocardial scintigraphy specificity 7%). Among 15 LBBB patients with coronary artery disease, MCE correctly identified a contrast defect in 14/15 patients, whereas rest thallium-201 myocardial scintigraphy demonstrated a perfusion defect in 15/15 patients (MCE sensitivity 93% vs scintigraphy sensitivity 100%). The two techniques showed a good agreement as for myocardial perfusion in the anterior wall (86.6% anterobasal; 86.6% mid-anterior; 80% distal anterior), the inferior wall (86.6%), the distal segment of the posterior lateral wall (83.3%), but a low concordance was found as for the basal septum (16.6%) and middistal septum (33.3%). CONCLUSIONS: MCE allows a diagnostic benefit in the detection of microvascular damage in patients with LBBB and unknown coronary artery disease, also in the presence of discordance with rest thallium-201 myocardial scintigraphy.     

Spontaneous changes in thallium-201 myocardial perfusion imaging after myocardial infarction

To examine regional myocardial perfusion after myocardial infarction, 26 patients underwent exercise electrocardiographic testing with thallium-201 myocardial perfusion imaging 3 weeks and 3 months after infarction. At 3 weeks, 9 of 26 patients (35%) had myocardial ischemia by exercise electrocardiographic testing, whereas 18 of 26 (69%) had ischemia by thallium-201 imaging. The thallium-201 scintigrams were scored by dividing each image, in 3 views, into 5 segments, using a 5-point scoring scheme. The exercise thallium-201 score was 44.3 ± 1.2 and increased to 47.3 ± 1.2 in the redistribution study (p < 0.001). Three months after infarction, although there was a significantly greater rate-pressure product which would predict a larger ischemic defect and a decrease in the stress thallium-201 score, the stress score was improved (48.3 ± 1.1, p < 0.001). The redistribution score was similar, that is, 48.9 ± 1.0. The improvement in thallium-201 myocardial perfusion was associated with a loss of stress-induced ischemia in 8 patients (30%). These results indicate that spontaneous improvements in thallium-201 myocardial perfusion imaging may occur after myocardial infarction.     

Incremental prognostic value of exercise thallium-201 myocardial single-photon emission computed tomography late after coronary artery bypass surgery

Objectives.This study assessed the incremental prognostic value of exercise thallium-201 myocardial perfusion single-photon emission computed tomography (SPECT) performed ≥5 years after coronary artery bypass surgery.Background.Thallium-201 scintigraphy has shown significant prognostic value in a variety of populations with suspected and known coronary artery disease. However, its value in patients with previous bypass surgery remains unknown.Methods.We studied 294 patients who were prospectively followed up. Cox proportional hazards models for prediction of “hard” events (cardiac death and nonfatal infarctions) were constructed, with variables considered for inclusion in hierarchic order: clinical and exercise data first, followed by scintigraphic information.Results.Mean (± SD) follow-up duration after scintigraphy was 31 ± 11 months. There were 20 cardiac deaths and 21 monfatal acute myocardial infarctions. Twenty-nine patients had late (>60) days after thallium-201 SPECT) revascularization procedures or underwent repeat bypass surgery or percutaneous transluminal angioplasty. Shortness of breath and peak exercise heart rate were the most important clinical predictors of hard events. Two scintigraphic variables added significant prognostic information to the clinical model: the thallium-201 summed reversibility score (summation of segmental differences between stress and redistribution scores) and the presence of increased lung uptake of the radiotracer. The global chi-square statistic for this model was twice as high as that for the clinical/exercise model alone (49.7 vs. 24.2). When a second multivariate Cox model was build adding “soft” events (i.e., late revascularization procedures) as outcomes of interest, the summed reversibility score was selected as an independent scintigraphic predictor of events. The global chi-square statistic for this model was 50.7, three times as high as that for the clinical/exercise model alone.Conclusions.After evaluation of treadmill and exercise data, thallium-201 myocardial perfusion SPECT provided incremental prognostic information in patients late after bypass.     

Reverse redistribution of thallium-201: a sign of nontransmural myocardial infarction with patency of the infarct-related coronary artery

The pattern of reverse redistribution on the day 10 poststreptokinase resting thallium-201 myocardial scintigrams is a common finding in patients who have undergone streptokinase therapy in evolving myocardial infarction. To investigate this phenomenon, 67 patients who underwent streptokinase therapy were studied pre- and 10 days poststreptokinase therapy resting thallium-201 studies, poststreptokinase therapy resting radionuclide ventriculography and coronary arteriography (60 of the 67 patients). Of the 67 patients, 50 (75%) showed the reverse redistribution pattern on the day 10 thallium-201 study (Group I), 9 (13%) had a nonreversible defect (Group II) and the remaining 8 (12%) had a normal study or showed a reversible defect (Group III). The reverse redistribution pattern was associated with patency of the infarct-related artery (100%), quantitative improvement in resting thallium-201 defect size from day 1 to day 10 study (94%) and normal or near normal wall motion on day 10 radionuclide ventriculography (80% of segments with marked and 54% of those with mild reverse redistribution). In contrast, nonreversible defects were associated with significantly less frequent patency of the infarct-related artery (67%, p = 0.01), improvement in defect size (11%, p less than 0.001) and normal or near normal wall motion (21%, p less than 0.05). Group III patients were similar to Group I with respect to these variables. The quantitated thallium-201 percent washout was higher in the regions with the reverse redistribution pattern (49 +/- 15%) compared with the contralateral normal zone (24 +/- 15%, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of intracoronary thrombolytic therapy on exercise-induced ischemia after acute myocardial infarction

Intracoronary streptokinase (SK) therapy increases vessel patency rate after acute myocardial infarction (AMI) and thus may lead to a greater exercise-induced myocardial ischemia. This hypothesis was tested in 39 patients enrolled in an angiographically randomized trial of intracoronary SK (19 treated with SK and 20 control subjects); all patients underwent thallium-201 scintigraphy at rest before acute angiography, as well as at rest and during stress 5 to 6 weeks after AMI. The patients were classified into 2 groups based on the presence (n = 13) or absence (n = 26) of complete obstruction of the infarct-related coronary artery at the end of the acute angiography. Semiquantitative score of myocardial thallium uptake was expressed as percent of maximal defect score. Thallium defect score at rest between admission and 5 to 6 weeks' study decreased from 10 +/- 16% units in the control group and from 23 +/- 14% units in the SK group (p = 0.01). This decrease was related to opening of the infarct-related artery (opening 23 +/- 16% vs occlusion 5 +/- 10%). The change in exercise-induced defect score was significantly (p = 0.01) larger in patients in the SK group (11 +/- 6% units) than in those in the control group (5 +/- 7% units). The perfusion defect during exercise was larger (p = 0.006) in patients with incomplete obstruction or reperfusion (10 +/- 6% units) than in patients with complete obstruction (3 +/- 7%). This difference was independent of the number of diseased coronary vessels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serial myocardial scintigraphy after a single dose of thallium-201 in men after acute myocardial infarction

Serial myocardial scintigraphy after a single dose of thallium-201 in the period immediately after myocardial infarction may demonstrate redistribution of thallium-201 into perfusion defects that were evident in the initial scan. This study tested the hypothesis that evaluation of this redistribution, available within hours of infarction, could provide a more accurate estimate of the eventual perfusion defect than a single thallium-201 Image obtained immediately after infarction. The study group comprised 14 patients with a diagnosis on admission of probable acute myocardial infarction. The patients received thallium-201 a mean of 1.3 hours after admission to the coronary care unit. Imaging began 10 minutes after the thallium injection and was repeated 4 to 8 hours later.Eight patients with acute myocardial infarction had a definite reduction in one or more perfusion defects on serial scintigraphy, possibly indicating reperfusion of transiently Ischemic zones. Two patients with acute infarction had an increase in perfusion defects in a second study performed 6 hours after the initial scintigram. In the interval between scans, one patient had a cardiac arrest with clinical evidence of infarct extension after successful resuscitation; the other sustained a lateral extension of the infarct. One patient with acute aortic dissection had normal scans on both studies. All three patients with unstable angina had an abnormal initial scan; on repeat scan, the thallium-201 defect was unchanged in one patient, increased in one and decreased in the third. In the patients with myocardial infarction, repeat thallium-201 scans corresponded more nearly than the initial scans to the extent of technetilum-99m stannous pyrophosphate uptake by the heart.These data suggest that serial myocardial imaging with thallium-201 immediately after myocardial infarction can overcome some of the limitations of a single thallium-201 scintigram and may be useful in delineating ischemic from infarcted myocardium in the postinfarction period.     

QT dispersion in patients with Takayasu arteritis

This study was designed to test the hypothesis that myocardial involvement exists in patients with Takayasu arteritis and is associated with increased QT dispersion, which is a marker of repolarization inhomogeneity. Twenty-one consecutive patients with Takayasu arteritis and no significant coronary artery disease were included. Twelve-lead electrocardiogram and exercise-induced thallium-201 myocardial scintigraphy were performed in all patients. Ten of 21 patients (48%) had abnormal findings on scintigraphy. Patients were divided into two groups by the presence (group P, n = 10) or absence (group N, n = 11) of exercise-induced thallium-201 myocardial scintigraphic perfusion abnormalities, including permanent defects in three, reversible defects in four, and slow washout in three. The QT dispersion at rest was significantly greater in group P than that in group N (54 +/- 12 vs 40 +/- 8 msec, p < 0.005). The QTc dispersion at rest was also significantly greater in group P than in group N (59 +/- 15 vs 43 +/- 11 msec, p < 0.01). In patients with Takayasu arteritis, myocardial involvement suggested by exercise-induced thallium-201 myocardial scintigraphic perfusion abnormalities is not rare, even when no significant coronary stenosis is present on angiography. Increased baseline QT dispersion was associated with scintigraphic abnormalities and may be a useful marker of myocardial involvement in patients with Takayasu arteritis.     

Coronary artery reperfusion in acute myocardial infarction: assessment by pre- and postintervention thallium-201 myocardial perfusion imaging

In a randomized trial of intracoronary streptokinase (STK) therapy in acute myocardial infarction, 44 patients (21 control subjects and 23 patients treated with STK) underwent sequential thallium-201 planar imaging before angiography and after 4 hours (redistribution), 4 days and 6 weeks. Patients were classified according to the presence or absence of angiographic reperfusion of the infarct-related artery. The semiquantitative score of myocardial thallium uptake was expressed as percent of maximal defect score. Both in control and in STK-treated groups, thallium defect scores decreased over time, but this decrease was smaller in the control group (before angiography, 33 +/- 4%; redistribution, 29 +/- 4%; 4 days, 25 +/- 4%; and 6 weeks, 22 +/- 4%) than in the STK group (44 +/- 4%, 38 +/- 4%, 26 +/- 4% and 21 +/- 3%, respectively). In patients in whom reperfusion was achieved (20 STK-treated, 6 control subjects), a marked decrease in thallium score was observed (before angiography, 40 +/- 4%; redistribution, 32 +/- 4%; 4 days, 20 +/- 5%; and 6 weeks, 14 +/- 22%) compared with patients in whom reperfusion was not achieved (37 +/- 4%, 36 +/- 5%, 33 +/- 5% and 33 +/- 4%, respectively). These results indicate that serial thallium imaging is an accurate method of assessing changes in myocardial perfusion after acute myocardial infarction. Restoration of thallium uptake was observed after reperfusion of the infarct-related artery whether this recanalization was seen spontaneously or after successful thrombolysis.     

Late reversibility of tomographic myocardial thallium-201 defects: an accurate marker of myocardial viability

Twenty-one patients were studied who underwent thallium-201 stress-redistribution single photon emission computed tomography (SPECT) both before and after coronary artery bypass grafting (n = 15) or transluminal coronary angioplasty (n = 6). All patients underwent thallium imaging 15 min, 4 h and late (18 to 72 h) after stress as part of the preintervention thallium-201 scintigram. In a total of 201 tomographic myocardial segments with definite post-stress thallium-201 perfusion defects in which the relevant coronary arteries were subsequently successfully reperfused, the 4 h redistribution images did not predict the postintervention scintigraphic improvement: 67 (85%) of the 79 4 h reversible as well as 88 (72%) of the 122 4 h nonreversible segments improved (p = NS). The 18 to 72 h late redistribution images effectively subcategorized the 4 h nonreversible segments with respect to postintervention scintigraphic improvement: 70 (95%) of the 74 late reversible segments improved after intervention, whereas only 18 (37%) of the 48 late nonreversible segments improved (p less than 0.0001). The frequency of late reversible defects and the frequency of postrevascularization improvement of late nonreversible defects are probably overestimated by this study because of referral biases. The cardiac counts and target to background ratios from late redistribution studies resulted in satisfactory cardiac images for visual interpretation. For optimal assessment of the extent of viable myocardium by thallium-201 scintigraphic studies, late redistribution imaging should be performed when nonreversible defects are observed on 4 h redistribution images.     

Exercise training following myocardial infarction improves myocardial perfusion assessed by thallium-201 scintigraphy

AIM: We assessed the effects of a 6-week exercise programme on the thallium-201 myocardial perfusion characteristics of patients following myocardial infarction. METHODS: Twenty-five patients presenting with a first acute myocardial infarction were randomised into two groups: (i) those undergoing a supervised exercise training programme over 6 weeks (n=15) and (ii) a control group who did not attend the exercise programme (n=10). All underwent three sequential stress thallium myocardial perfusion scans at 10 days, 6 weeks and 3 months after infarction. The stress conditions were identical on each occasion. The images were analysed using a polar plot with a computer assisted algorithm comparing stress and redistribution data. Values for extent, severity and percentage redistribution of the thallium images were generated. RESULTS: A total of 29 perfusion defects were identified, 18 in the exercise group and 11 in the control group. Over 3 months in the exercise group the mean extent of the stress image defect fell from 109+/-64 to 95+/-51 pixels (P<0.05) while in the control group there was an increase from 133+/-57 to 144+/-57 pixels (P=ns). Stress defect severity fell in the exercise group from 581+/-417 to 494+/-346 S.D. (P<0.05) but increased in the control group from 765+/-494 to 877+/-543 S.D. (P=ns). On redistribution imaging in the exercise group a significant decrease was observed in both extent (94+/-56 to 76+/-43 pixels (P<0.05)) and severity (541+/-387 to 438+/-291 S.D. (P<0.05)) of the defects. However in the control group no significant change was observed for extent (125+/-54 to 125+/-52 pixels) or severity (745+/-485 to 820+/-503 S.D.) of the redistribution defects (P=ns). Reversibility of the defects increased slightly in both the exercise group (from 14.6+/-17 to 17.5+/-20%) and the control group (5.2+/-5 to 9.6+10%) (P=ns). CONCLUSION: Following myocardial infarction a 6-week exercise programme improves myocardial perfusion characteristics. An exercise programme should be integrated into cardiac rehabilitation protocols for patients after infarction.     

Late prognostic value of scintigraphic parameters of acute myocardial infarction size in complicated myocardial infarction without heart failure

Perfusion scintigraphy with thallium-201, infarct scintigraphy with technetium-99m pyrophosphate (TcPYP), and equilibrium blood pool scintigraphy were performed during the initial hospitalization for acute myocardial infarction (MI) in 25 patients without evidence of heart failure who presented with advanced electrocardiographic rhythm and conduction disturbances requiring treatment. Scintigraphic findings during short-term hospitalization were related to the late clinical follow-up performed an average of 14 months later, where patients were grouped as asymptomatic, 8 patients; symptomatic, 9 patients; and deceased, 8 patients. Quantitation of perfusion abnormalities, TcPYP image abnormalities, and left ventricular ejection fraction (EF) revealed that the deceased group had significantly larger TcPYP abnormalities (36 +/- 20 cm2), absolute perfusion abnormalities (32 +/- 16 cm2), and perfusion abnormalities expressed as a percentage of the projected left ventricular area (42 +/- 8%) than the asymptomatic group (13 +/- 8 cm2, 14 +/- 6 cm2, and 20 +/- 9%; p less than 0.05, p greater than 0.05, and p less than 0.01, respectively). The percent perfusion abnormality was significantly larger in the deceased group (42 +/- 8%, p less than 0.01) than in either the symptomatic group (35 +/- 13%, p less than 0.01) or the asymptomatic group (20 +/- 9%), and this parameter in the symptomatic group also differed from that in the asymptomatic group (p less than 0.01). The study indicates that patients with rhythm and conduction disturbances and without congestive heart failure during acute MI may follow an uncomplicated or a complicated late clinical course. Early scintigraphic measurements of MI and perfusion correlate well with this outcome; however, EF could not differentiate among prognostic subgroups.     

Myocardial scintigraphy with Tc-99m-teboroxime: its feasibility and the evaluation of its diagnostic reliability. A comparison with thallium-201 and coronary angiography]

BACKGROUND. Tc-99m-teboroxime is a new tracer for myocardial perfusion scintigraphy. Its more remarkable features are the high myocardial extraction fraction, which is well correlated with the coronary blood flow, and the extremely rapid myocardial washout. This makes it necessary to complete the image collection shortly after the injection; on the other hand, repeated scans can be easily performed by renewed Tc-99m-teboroxime administrations. The aim of the present study was to test the feasibility of Tc-99m-teboroxime imaging and to evaluate its accuracy by comparing it with thallium-201 (TI-201) scintigraphy and coronary angiography. METHODS. The patient population included 16 male patients (mean age 57.8 +/- 6.3 years) affected by suspect effort angina and/or with signs of exercise-induced ischemia; 12 of them had history of previous myocardial infarction. They underwent effort TI-201 and Tc-99m-teboroxime myocardial scintigraphy within 48 hours; left heart catheterization and coronary angiography were performed within 5 days. Scintigraphic images were collected in 3 planar views; each projection was divided in 3 segments, with the apical one shared by all views, for a total of 7 segments/study. Tracer uptake was qualitatively assessed and graduated according to a scoring scheme (from 0 = normal through 4 = absent uptake). RESULTS. Tc-99m-teboroxime scans could be accomplished without major problems in all subjects. The image quality was comparable to TI-201 in 8 patients and poorer in the remaining 8. Coronary angiography showed 50% obstructions in 15 patients; of them 1 subject had a normal scintigraphic pattern with both TI-201 and Tc-99m-teboroxime. The presence of previous infarction was recognized by both tracers in the 12 patients with infarct history. The number of abnormal segments and the uptake score were not significantly different in the Tc-99m-teboroxime rest and in the TI-201 redistribution images (segments: 2.8 +/- 1.4 vs 2.8 +/- 1.6; score: 5.6 +/- 4.2 vs 6 +/- 4.5). The diagnosis of effort ischemia was made in 13 patients with Tc-99m-teboroxime and in 12 patients with TI-201. The number of abnormal segments in the exercise Tc-99m-teboroxime and TI-201 myocardial scintigraphy was not significantly different (3.3 +/- 1.3 vs 3.3 +/- 1.5); on the contrary the defect score was significantly higher with Tc-99m-teboroxime than with TI-201 (9.5 +/- 4.3 vs 8.4 +/- 4.6, p < 0.03). Therefore the ischemic score (exercise defect score minus rest defect score) of Tc-99m-teboroxime was significantly higher than that of TI-201 (3.9 +/- 2.8 vs 2.4 +/- 2.2, p < 0.02). The two tracers gave comparable results in terms of recognition of patients with one-vessel or multi-vessel coronary artery disease. CONCLUSIONS. Planar myocardial scintigraphy with Tc-99m-teboroxime can be performed without major problems. In terms of clinical reliability the results are comparable to those of TI-201 scans. On the other hand, taking into account the poor image quality of Tc-99m-teboroxime scintigraphy, it is still impossible to predict its future role in the radionuclide imaging of coronary artery disease.     

Prevalence of and variables associated with silent myocardial ischemia on exercise thallium-201 stress testing

The prevalence of silent myocardial ischemia was prospectively assessed in a group of 103 consecutive patients (mean age 59 +/- 10 years, 79% male) undergoing symptom-limited exercise thallium-201 scintigraphy. Variables that best correlated with the occurrence of painless ischemia by quantitative scintigraphic criteria were examined. Fifty-nine patients (57%) had no angina on exercise testing. A significantly greater percent of patients with silent ischemia than of patients with angina had a recent myocardial infarction (31% versus 7%, p less than 0.01), had no prior angina (91% versus 64%, p less than 0.01), had dyspnea as an exercise test end point (56% versus 35%, p less than 0.05) and exhibited redistribution defects in the supply regions of the right and circumflex coronary arteries (50% versus 35%, p less than 0.05). The group with exercise angina had more ST depression (64% versus 41%, p less than 0.05) and more patients with four or more redistribution defects. However, there was no difference between the two groups with respect to mean total thallium-201 perfusion score, number of redistribution defects per patient, multi-vessel thallium redistribution pattern or extent of angiographic coronary artery disease. There was also no difference between the silent ischemia and angina groups with respect to antianginal drug usage, prevalence of diabetes mellitus, exercise duration, peak exercise heart rate, peak work load, peak double (rate-pressure) product and percent of patients achieving greater than or equal to 85% of maximal predicted heart rate for age. Thus, in this study group, there was a rather high prevalence rate of silent ischemia (57%) by exercise thallium-201 criteria.(ABSTRACT TRUNCATED AT 250 WORDS)     

Beta-methyl-15-P-[123I] iodophenyl-pentadecanoic acid and thallium-201 in the assessment of myocardial perfusion defects

The purpose of this investigation was to examine the ability of beta-methyl-15-P-[123I]-iodophenyl-pentadecanoic acid (beta 123IPPA) and thallium-201 to assess the ischemic risk zone associated with myocardial infarction. The hearts of mongrel dogs were infarcted by ligating the left anterior descending coronary artery and at 6 h post infarction injected with thallium-201 (2 mCi; scanning time 30 mins) followed by beta 123IPPA (3 to 5 mCi; scanning time 30 mins). Scintigraphic assessment of the perfusion defect yielded perfusion defect size (percentage of whole slice), which was then compared to the defect when assessed by tetrazolium staining. Myocardial ratios were calculated to assess differences in localization between tracers. Any differences noted may affect identification of the area at risk following acute myocardial infarction. A slice-by-slice comparison of perfusion defect size for scintigraphic methods and histochemical method showed no significant difference between beta 123IPPA and thallium-201. The mean ratio for myocardial defect size expressed as beta 123IPPA/thallium-201 was 1.03 +/- 1.29. Enzymatic analysis demonstrated significant increases in creatine kinase (160.33 +/- 46.44 to 5030.6 +/- 2238 U) and creatine kinase-MB% (31.85 +/- 15.11 to 82.99 +/- 8.14%) post infarction (P less than 0.05 in both cases). Elevated ST segments were also seen in all dogs post infarction. It can be concluded that the combined use of beta 123IPPA and thallium-201 does not allow the identification of the ischemic risk zone (percentage area at risk) often associated with myocardial perfusion defects. Problems continue to exist with image resolution and border demarcation.     

Cholesterol reduction improves myocardial perfusion abnormalities in patients with coronary artery disease and average cholesterol levels

OBJECTIVES: We sought to evaluate whether pravastatin treatment increases myocardial perfusion, as assessed by thallium-201 single-photon emission computed tomographic (SPECT) dipyridamole testing, in patients with coronary artery disease (CAD) and average cholesterol levels. BACKGROUND: Previous studies in hypercholesterolemic patients have demonstrated that cholesterol reduction restores peripheral and coronary endothelium-dependent vasodilation and increases myocardial perfusion. METHODS: This was a randomized, placebo-controlled study with a cross-over design. Twenty patients with CAD were randomly assigned to receive 20 mg of pravastatin or placebo for 16 weeks and then were crossed over to the opposite medication for a further 16 weeks. Lipid and lipoprotein analysis and dipyridamole thallium-201 SPECT were performed at the end of each period. The SPECT images were visually analyzed in eight myocardial segments using a 4-point scoring system by two independent observers. A summed stress score and a summed rest score were obtained for each patient. Quantitative evaluation was performed by the Cedars-Sinai method. The magnitude of the defect was expressed as a percentage of global myocardial perfusion. RESULTS: Total and low density lipoprotein cholesterol levels during placebo were 214 +/- 29 mg/dl and 148 +/- 25 mg/dl, respectively. These levels with pravastatin were 170 +/- 23 mg/dl and 103 +/- 23 mg/dl, respectively. The summed stress score and summed rest score were lower with pravastatin than with placebo (7.2 +/- 2.3 vs. 5.9 +/- 2.3, p = 0.012 and 3.2 +/- 1.6 vs. 2.4 +/- 2.2, p = 0.043, respectively). Quantitative analysis showed a smaller perfusion defect with pravastatin (29.2%) as compared with placebo (33.8%) (p = 0.021) during dipyridamole stress. No differences were found at rest. CONCLUSIONS: Reducing cholesterol levels with pravastatin in patients with CAD improves myocardial perfusion during dipyridamole stress thallium-201 SPECT.     

Magnetic resonance imaging of myocardial infarction: correlation with enzymatic, angiographic, and radionuclide findings

Spin-echo cardiac magnetic resonance imaging studies were performed in 20 patients with a first 7- to 14-day-old (mean 10) myocardial infarction. The magnetic resonance imaging findings were compared with coronary angiography (14 patients), myocardial enzyme release (18 patients), radionuclide angiography (19 patients), and thallium-201 perfusion scintigraphy (19 patients). Regional T2 relaxation times determined from the signal intensities at echo times 30 msec and 90 msec were significantly prolonged in the infarcted areas. Based on abnormal T2 times for every patient, a regional and a total myocardial damage score was determined. The infarct-related artery was correctly identified in 93% of patients by magnetic resonance imaging, in 79% of patients by thallium-201 scintigraphy, and in 62% of patients by radionuclide angiography. The total damage score correlated well with enzymatic infarct size (r = 0.75, p less than 0.001). The correlation between left ventricular end-systolic volume index determined by magnetic resonance imaging and by radionuclide angiography was r = 0.89 (p less than 0.002). The left ventricular end-systolic volume index correlated significantly with enzymatic infarct size (r = 0.72, p less than 0.001), total damage score (r = 0.68, p less than 0.002), and radionuclide left ventricular ejection fraction (r = -0.68, p less than 0.002). Correlations between the magnetic resonance damage score and the thallium-201 perfusion score were r = 0.60 (p less than 0.01) for the exercise images, and r = 0.72 (p less than 0.001) for the redistribution images. This study shows that spin-echo magnetic resonance imaging is quite comparable with the established noninvasive imaging modalities currently used in patients with acute myocardial infarction.     

Myocardial perfusion abnormalities early (12-24 h) after coronary stenting or balloon angioplasty: implications regarding pathophysiology and late clinical outcome

OBJECTIVE: We prospectively examined the prevalence of reversible perfusion defects on very early (12-24 h) thallium-201 single photon emission computed tomography (SPECT) scintigraphy after angiographically successful percutaneous coronary intervention (PCI) by stenting and/or stand-alone balloon angioplasty and the predictive value of these defects for late target lesion revascularization (TLR). PATIENTS AND METHODS: 83 consecutive patients undergoing PCI for 88 lesions (38 balloon angioplasties, 50 stents) underwent very early (12-24 h) SPECT thallium-201 scintigraphy at rest and following administration of 0.7 mg/kg intravenous dipyridamole after PCI. Univariate and multivariate clinical, procedural and scintigraphic correlates of target lesion revascularization during long-term follow-up were examined. RESULTS: Coronary stenting achieved a larger immediate post-PCI minimal luminal dimension (2.7 +/- 0.4 vs. 2.1 +/- 0.4 mm, p < 0.001) and less residual stenosis (4 +/- 12 vs. 19 +/- 11%, p < 0.001) than stand-alone balloon angioplasty. Nonetheless, early reversible perfusion defects were similarly present in the territory supplied by 36% of stented lesions and 32% of lesions treated by balloon angioplasty (NS). Of 81 lesions (76 patients) available for long-term clinical follow-up, TLR was performed in 11% of the stent group and 14% of the balloon angioplasty group (NS). By multivariate logistic regression analysis, diabetes mellitus was the only predictor of late TLR (p < 0.05). The type of intervention (balloon or stent) predicted neither early perfusion defects nor late TLR. CONCLUSIONS: Early 201-thallium SPECT scintigraphy was abnormal in a third of patients treated by stand-alone balloon angioplasty or by stent placement. The very early SPECT scintigraphic findings did not differentiate between balloon and stent and did not predict late TLR.     

The relationship between chest pain during thallium-201 scintigraphy with dipyridamole and myocardial ischemia

Dipyridamole thallium-201 scintigraphy (DP-Tl) and coronary angiography were studied on 74 patients with suspected coronary artery disease. We compared the clinical features, hemodynamic responses, angiographic results and scintigraphic findings of patients who had chest pain during DP-Tl testing ('chest pain' group) with those of patients who did not have chest pain ('no pain' group). Thirty eight (51%) of the 74 patients developed chest pain. Heart rate and rate pressure product during DP infusion of 'chest pain' group were greater than those of the 'no pain' group (p less than 0.05). Ischemic ST depression was more frequently observed among 'chest pain' patients (p less than 0.01). There were no differences in angiographic severity of coronary artery disease between 'chest pain' and 'no pain' group. Also, we could find no differences in extent and severity scores of perfusion defects and washout abnormalities between the two groups. However, when patients with myocardial infarction were excluded, the 'chest pain' group had significantly greater extent and severity scores of washout abnormalities than the 'no pain' group (extent score: 38 +/- 8 vs 18 +/- 5, p less than 0.05, severity score: 55 +/- 15 vs 18 +/- 7, p less than 0.01). Our study indicated that in patients without myocardial infarction, patients with 'chest pain' had more severe ischemia than 'no pain' patients. But in patients with myocardial infarction, myocardial ischemia not accompanied by chest pain might be as severe as that with chest pain. The presence or absence of myocardial infarction might have great influence on results regarding the relation of chest pain to myocardial ischemia.     

Nicardipine improves myocardial perfusion in systemic sclerosis

Primary scleroderma myocardial disease may be due in part to myocardial ischemia caused by a disturbance of the coronary microcirculation. We evaluated the effect of the calcium channel blocker nicardipine on myocardial perfusion assessed by thallium-201 scanning in 16 patients with systemic sclerosis. Thallium-201 single photon emission computerized tomography was performed at baseline and 90 min after 40 mg of oral nicardipine. The mean (+/- SD) number of left ventricular segments with perfusion defects significantly decreased from 6.0 +/- 2.0 at baseline to 4.1 +/- 2.3 after nicardipine (p less than 0.01). The mean global perfusion score significantly increased from 10.2 +/- 1.9 at baseline to 11.9 +/- 2.6 after nicardipine (p less than 0.02). Our study demonstrates short-term improvement in thallium-201 myocardial perfusion with nicardipine in patients with systemic sclerosis.