Reverse redistribution in the stress thallium scan--correlation of coronary blood flow and myocardial damage

In order to make clear 'reverse redistribution (RR)' phenomenon in stress thallium scan we investigated 477 consecutive patients who were consisted of 74 cases with PTCA (PTCA group), 86 cases with coronary artery bypass graft (CABG group) and 317 cases without any revascularization (N group). RR was detected in 12 cases out of PTCA group (16%), in 11 cases out of CABG group (13%) and in 10 cases out of N group (3.2%), and the incidence of RR in PTCA or CABG group was higher than that of N group (p less than 0.01). In 33 patients with RR the cases without significant coronary artery stenosis were more than those with stenosis (p less than 0.01) and the cases with myocardial damage were more than those without damage (p less than 0.01). In quantitative analysis washout rate at the RR areas showed relatively high value, but it was not significant compared with normal value (53 +/- 9.0% vs. 49 +/- 1.9%). In conclusion, RR had a tendency to appear in the condition of normal myocardium mingled with scar and of sufficient coronary blood flow. The mechanism of the phenomenon was thought to be that initial uptake of thallium in the partially scarred area was as high as in the normal myocardium, but washout of thallium from its remaining normal myocardium is normal or faster so that the defect appears at the myocardium mingled with scar. Therefore existence of reverse redistribution suspects the myocardium mingled with scar and sufficient coronary blood flow to the remaining normal myocardium.     

Evaluation of efficacy of PTCA in patients with angina pectoris by exercise Tl-201 myocardial SPECT

Exercise 201Tl single photon emission computed tomography (Ex-SPECT) was performed before and after percutaneous transluminal coronary angioplasty (PTCA) to detect ischemia and determine the response of the ischemic myocardium. In a series of 132 patients with angina pectoris, 43 were followed up by Ex-SPECT and coronary angiography. Before PTCA, ischemia was detected in 85% of the patients, and in all cases a diameter stenosis (%DS) of 90% or more was seen. After PTCA, 90% of the patients showed improvement of ischemia. An excellent correlation between the pressure gradient (PG) as determined during PTCA and the washout rate (WR) suggests that the WR can be used as a measure for myocardial perfusion in the areas related to coronary stenosis. During follow-up by Ex-SPECT, 34 patients were found with redistribution, and restenosis was present in 59% of these patients. In comparison with the images obtained one week after PTCA, a further improvement was confirmed by Ex-SPECT during follow-up in 5 of 20 patients without restenosis. Ex-SPECT proved to be of use in evaluating the response of the ischemic myocardium to PTCA, as well as the therapeutical effects and the degree of restenosis. Long-term follow-up revealed that some patients had areas of hibernating myocardium.     

Tc-99m MIBI SPECT in the assessment of myocardial reperfusion after percutaneous transluminal coronary angioplasty.

Tc-99m MIBI SPECT was used to assess the early benefits of successful percutaneous transluminal coronary angioplasty (PTCA) in nine consecutive patients. SPECT stress studies were done by artificial cardiac pacing just prior to PTCA and 16-20 hours later, with perfusion images obtained 2-3 hours after pacing stress and Tc-99m MIBI injection. Angiographic restenosis was demonstrated in three patients at a later date, and all of these showed no significant improvement on the perfusion study after PTCA. All four patients asymptomatic at 7 months following PTCA had an average 15% improvement in segmental perfusion after the procedure. In two patients symptomatic after PTCA, one showed angiographic patency and had greater than 15% improvement in perfusion, while the second showed no scintigraphic improvement (no angiographic data obtained). This preliminary study suggests that Tc-99m MIBI is an important adjunct to angiography in estimating the amount of myocardium "at risk" before and after PTCA.     

Reverse redistribution of 99m Tc-sestamibi after direct percutaneous transluminal coronary angioplasty in acute myocardial infarction: relationship with wall motion and functional response to dobutamine stimulation

Reverse redistribution (RR) of 99mTc-sestamibi is observed after direct percutaneous transluminal coronary angioplasty (PTCA) in acute myocardial infarction (AMI). The purpose of this study was to clarify the functional characteristics of myocardial segments with RR after direct PTCA in AMI. Thirty patients with AMI who had undergone direct PTCA were examined. Myocardial perfusion tomography with 99mTc-sestamibi and low dose dobutamine echocardiography were performed within 2 weeks of the onset. The 99mTc-sestamibi images were obtained 1 and 3 h after tracer administration. The left ventricle was divided into nine segments, and regional 99mTc-sestamibi uptake and clearance were quantitatively evaluated in each segment. RR was defined as a decrease in 99mTc-sestamibi uptake of >10% on 3 h delayed images compared with the 1 h early images. The left ventricle in the echocardiographic images was also divided into nine segments corresponding to the scintigraphic images, and regional wall motion was assessed in the resting condition as the baseline and during dobutamine administration (5-10 microg x kg(-1) x min(-1)). Out of a total of 270 myocardial segments, 111 segments were perfused by the culprit coronary artery and were defined as ischaemic segments. There were 25 segments with RR and 86 segments without RR in the ischaemic myocardium. Enhanced clearance of 99mTc-sestamibi was observed in ischaemic segments with RR (P<0.001). Echocardiography demonstrated that 24 out of 25 segments with RR and 61 out of 86 segments without RR had wall motion abnormalities. Dobutamine infusion improved wall motion in 20 (83%) of the 24 dysfunctional segments with RR and 33 (54%) of the 61 dysfunctional segments without RR (P<0.02). These findings suggest that RR indicates reversible functional abnormalities associated with preserved contractile reserve in response to dobutamine. The early and delayed imaging of 99mTc-sestamibi provides useful information regarding the residual viability of the dysfunctional myocardium in AMI patients.     

Usefulness of coronary angioplasty (PTCA) of the infarct-related artery in patients with prior myocardial infarction--follow up of infarct zone pre- and post-angioplasty by stress thallium scan

We studied the efficacy of coronary angioplasty (PTCA) of the infarct-related artery in 29 patients with prior myocardial infarction by stress thallium scan. Twenty-seven patients had anterior myocardial infarction (single LAD disease), one had inferior (single RCA disease) and one had posterior (single LCX disease). According to the stress-redistribution thallium scintigraphic finding before PTCA, the patients were classified in 4 groups; (A): three patients with complete redistribution. (B): fourteen patients with incomplete redistribution. (C): seven patients with partial redistribution. (D): five patients with no redistribution. After PTCA, the parameters of residual ischemia in the infarct area (% RD and Thallium ischemic score = TIS) were improved significantly but those of infarct size (RD% uptake and Defect Score = DS) were improved slightly in group A. In group B and C, % RD, TIS, RD% uptake and DS were all improved significantly. In group D, TIS was improved slightly and DS was improved slowly 3 months after PTCA. Group A had high probability of viable muscle and group D had high probability of scar at the infarct zone. Group B and C showed intermediate type between group A and D. The change of infarct area after PTCA was variable in 4 groups but both residual ischemia and infarct size decreased in all groups. Thus, PTCA of infarct-related coronary artery is useful even in the patients with prior myocardial infarction.     

冠心病患者PTCA术前后不同冠脉病变支数心率变异性的对比分析

目的　观察不同冠脉病变支数患者心率变异性 (HRV)的变化有无差异及经皮腔内冠脉成形术 (PTCA)对HRV的影响。方法　应用动态心电图中心率变异性的时域和频域分析技术 ,对不同冠脉病变支数患者在PTCA术前、术后 1周及 6个月的自主神经活性进行对比分析。其中单支病变 2 3例 ,双支病变 2 7例 ,三支病变 18例。结果　 (1)PTCA术后 1周HRV较术前有所改善 ,但差异无统计学意义 (P >0 0 5 ) ,术后 6个月HRV明显增高 ,差异有统计学意义 (P <0 0 5 ) ;(2 )PTCA术前、术后冠脉单支、双支、三支病变各组间HRV差异均无统计学意义。结论　冠心病患者HRV的改变可能与神经体液因素对窦房结功能的调控失衡有关 ,而与冠脉病变支数无关。PTCA术后远期HRV显著改善 ,其机制可能与PTCA术改善患者心肌缺血有关。     

Stunned myocardium

BACKGROUND: Stunned myocardium is a state of delayed recovery of regional contractility after a transient period of ischemia followed by reperfusion. CASE REPORT: A 67-year-old patient was admitted to our hospital with acute anterior myocardial infarction, and treated using percutaneous transluminal coronary angioplasty (PTCA) within acute disease stage. Reversible myocardial dysfunction persisted after ischemia following the return of normal perfusion. Abnormal resting wall motion with augmentation of contractility at low and high doses of dobutamine characterizes the stunned myocardium and reflects the normal blood flow reserve, characteristic for these postischemic, reperfused segments. SPECT (Single Photon Emission Computerized Tomography) with Tc 99 and dipyradamole showed normalization of perfusion defects in the apical region. There months after the infarction and PTCA, contractility was almost completely recovered. CONCLUSION: Stunned myocardium recovery lasted from few weeks to few months. Control ultrasonography as well as SPECT showed normalization of systolic function of the left ventricle in the viable segments registered at previous examinations.     

Clinical significance of exercise induced ST segment depression after successful percutaneous transluminal coronary angioplasty--assessment by thallium-201 SPECT

To evaluate the clinical significance of ST segment depression during repeated Treadmill exercise after successful PTCA, Thallium-201 SPECT was performed. The Thallium-201 SPECT was performed before, one week after and 3-6 months after PTCA. All thirty-five patients had one vessel disease and positive Thallium-201 exercise test. During follow-up period for 3-6 months, 11 of 35 patients had persistent ST segment depression. Restenosis of dilated coronary lesion was demonstrated in 6 of 11 patients. In another 3 of 35 patients, exercise induced ST segment depression was disappeared during follow-up Treadmill exercise. In 14 patients with persistent or transient ST segment depression after PTCA, Thallium-201 SPECT demonstrated transient ischemia in 5 of 6 patients with restenosis. In other 8 patients without restenosis, SPECT images did not demonstrate myocardial ischemia and coronary arteriographic findings could not verify side branch stenosis or intimal dissection which might cause myocardial ischemia. The etiology of ST segment depression after successful PTCA in one vessel disease is not produced by exercise induced myocardial ischemia but still unknown mechanisms may be present.     

Assessment of myocardial viability with (99m)Tc-sestamibi -gated SPET images in patients undergoing percutaneous transluminar coronary angioplasty

The present study was designed to evaluate whether nitroglycerin administration preceding the injection of technetium-99m labelled metroxy-isobutyl-isonitryl ((99m)Tc-sestamibi), improves the detection of myocardial perfusion defect reversibility. Moreover, we assessed whether myocardium kinetics improved after the percutaneous transluminar coronary angioplasty (PTCA) study. The study population consisted of 12 patients, 8 males and 4 females, 48-73 years old (mean age: 60.41 years) with chronic stable angina, resting wall dyskinesia, and >/=50% stenosis or occlusion of at least one coronary artery, who were scheduled to undergo PTCA. A gamma-camera gated single photon emission tomography myocardial perfusion scintiscan was performed as a baseline study with (99m)Tc-sestamibi (GSPET-B) and another similar scintiscan after nitrate augmentation (GSPET-N) before PTCA and two to six months after PTCA (GSPET-R), to assess the extent of perfusion defects, contraction abnormalities and myocardial viability. Cedars QGS software was used for semi quantitative assessment and sum perfusion scores were calculated for each study. According to our results from the 174 hypoperfused segments studied by GSPET-B, 137 segments had tracer activity <50%. From the 137 segments with tracer activity of <50% only 51 (37%) remained unaltered after PTCA. Twenty-six of them (51%) were described as nonviable after the GSPET-N study and the remaining 25 were defined as viable. Our study demonstrated significant perfusion improvement after nitrate augmentation (mean sum perfusion score decreased from 34+/-9 in the baseline study (SBS) to 23+/-11 in the GSPECT-N study (SNS), P=0.04. There was no significant difference between SNS and mean sum perfusion score after revascularisation (SRS), 23+/-11 and 24+/-13 respectively (P=0.833). The specificity, sensitivity and accuracy of the perfusion improvement after PTCA, were calculated as: 52%, 85% and 76% respectively. The low specificity in our study could be due to performing GSPET-R in some patients, six months after PTCA; during this time restenoses may occur. Two of our patients whose perfusion and myocardial wall motion kinetics had worsened and also had clinical symptoms of pain and fatigue, were considered to have developed restenosis. In the present study, myocardial wall motion kinetics showed non-significant improvement of global ejection fraction (EF). EF increased from 43.9%+/-3.3% to 48.9% after nitrate augmentation (P=0.262) and to 47.2%+/-6.4% after revascularization (P=0.091). Myocardial wall motion hypokinesia showed significant improvement of severity scores in the GSPET-N study, as well as after PTCA revascularization (P<0.01). It is concluded that GSPET-N (99m)Tc-sestamibi imaging significantly improves the detection of defect reversibility. On the basis of our results, it appears appropriate to recommend GSPET-N (99m)Tc-sestamibi imaging only in patients with perfusion defects and tracer activity of <50%. In such cases it is recommended to perform GSPET not only for perfusion but also for a myocardial wall motion kinetic study. The follow up study to evaluate the result of PTCA is recommended to be performed within 2 months after PTCA, before restenosis may occur and 6 months after PTCA if restenosis is suspected.     

Increase in serum cardiac myosin light chain I associated with elective percutaneous transluminal coronary angioplasty in patients with ischemic heart disease

Changes in serum myosin light chain I (MLCI) due to elective percutaneous transluminal coronary angioplasty (PTCA) were studied after PTCA (0, 8 and 48 hours) in 57 patients with old myocardial infarction (MI group) and 20 patients with angina pectoris (AP group). The AP group showed no increase after PTCA. In contrast, in the MI group there were 16 patients in whom MLCI at 48 hours was increased by 1.0 ng/ml or more (MI1 group) and another group of 41 patients who showed no increase in MLCI (MI2 group). The MI1 group had a significantly higher incidence of (1) non-Q wave myocardial infarction (62.5% vs. 17.1%, p < 0.01), (2) 99% stenosis of a coronary artery (50.0% vs. 12.2%, p < 0.01), and (3) redistribution in a hypoperfusion area found in the delayed image of resting thallium-201 (201Tl) myocardial scintigraphy (85.7% vs. 15.8%, p < 0.01). The left ventricular ejection fraction (LVEF) was significantly improved in the MI1 group, 3 to 4 months later (from 0.49 +/- 0.12 to 0.58 +/- 0.11, p < 0.01), in contrast to the patient of MI2 group who did not show any improvement. The AP group was not considered to have a bulk of myocardium impaired enough to show a release of MLCI due to PTCA-associated transient coronary occlusion. In the MI1 group, however, MLCI was probably released from the chronically under-perfused, but still salvageable, portion of the myocardium. This is consistent with the improvement in LVEF observed 3 to 4 months after the relief of severe coronary stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of myocardial revascularization on regional thallium-201 uptake and systolic function in regions with reverse redistribution on tomographic thallium-201 imaging at rest in patients with chronic coronary artery disease

Objectives  There is growing evidence that myocardial segments with reverse redistribution are viable in patients with chronic coronary artery disease. The aim of this study was to assess the effects of myocardial revascularization on systolic function and thallium-201 uptake in such segments. Methods  Rest-redistribution thallium-201 tomography before and after myocardial revascularization was performed in 47 patients with chronic coronary artery disease. Regional function was evaluated by two-dimensional echocardiography before and after revascularization according to a 3-point scale (1=normal, 2=hypokinetic, 3=a/dyskinetic). Improvement of dysfunctional segments was defined when systolic function score decreased ≥1 after revascularization. Reverse redistribution was defined as ≥8% decrease in relative thallium-201 uptake between rest and redistribution images. Results  Reverse redistribution was found in 27 (57%) of 47 patients, corresponding to 60 (11%) of 564 myocardial segments. Of such segments, 24 (40%) had normal systolic function, 19 (32%) were hypokinetic, and 17 (28%) were a/dyskinetic. Thirty-six segments underwent myocardial revascularization, and reverse redistribution was no longer present in 86% of them subsequent to the procedure. Of 26 dyssynergic segments with reverse redistribution subjected to revascularization, 18 (69%) improved at follow-up. Conclusions  The findings of the present study indicate that reverse redistribution is a reversible phenomenon and is often associated with improvement of systolic function following revascularization in patients with chronic coronary artery disease.     

Metabolic activity in the areas of new fill-in after thallium-201 reinjection: comparison with positron emission tomography using fluorine-18-deoxyglucose

Reinjection of thallium-201 after recording the 3-hr delayed scan often demonstrates improvement in areas of persistent abnormalities. To determine the metabolic activity of these areas, the changes seen on stress/redistribution/reinjection thallium SPECT were compared with PET using fluorine-18-fluorodeoxyglucose (FDG) in 18 patients with coronary artery disease. Of 48 segments showing no redistribution on the delayed scan, the reinjection scan identified new fill-in in 20 segments (42%), all of which demonstrated FDG uptake. In contrast, only 7 of the 28 segments (25%) showing no fill-in after reinjection were PET viable (p less than 0.01). Eleven patients had coronary bypass graft surgery after the radionuclide study. The majority of the segments showing redistribution (87%) and new fill-in after reinjection (65%) improved in wall motion, whereas only eight segments (25%) without new fill-in improved after surgery. Of those without new fill-in, two segments showing PET ischemia improved in wall motion, whereas the remaining six segments showing PET scar did not improve after surgery. Thus, the segments showing new fill-in after reinjection are PET viable myocardium. However, reinjection thallium imaging still underestimates the extent of tissue viability compared to PET imaging.     

Prediction of post-revascularization functional recovery of asynergic myocardium using quantitative thallium-201 rest-redistribution tomography: has the reverse redistribution pattern an independent significance?

The significance of reverse redistribution on rest-redistribution thallium-201 myocardial scintigraphy is unclear. Previous studies suggested that reverse redistribution segments with normal resting activity include viable myocardium, whilst resting defects with further worsening correspond to scar. We evaluated whether reverse redistribution has an independent significance for the prediction of post-revascularization recovery, particularly as compared with the quantification of redistribution activity. We studied 26 coronary artery disease patients with left ventricular dysfunction, who underwent ²⁰¹Tl rest-redistribution single-photon emission tomography (SPET) and echocardiography before revascularization. Viability was defined by the detection of wall motion improvement on follow-up echocardiography. ²⁰¹Tl activity was considered normal if ≥80%, moderately reduced if <80% but ≥50%, and severely decreased if <50%. Reverse redistribution was defined as a defect in redistribution images with ≥10% decrease in relative ²⁰¹Tl activity compared with the resting value. Reverse redistribution was detected in 33 segments (10%). Baseline dysfunction was equally observed in the reverse redistribution and in the non-reverse redistribution segments (64% vs 56%, P=0.40) and the rate of asynergic segments with post-revascularization recovery was not different between the two groups (33% vs 54%, P=0.11). The rate of functional recovery in redistribution defects without reverse redistribution was 53% in moderate and 30% in severe defects; the corresponding values for the reverse redistribution segments were 50% and 27% (all non-significant versus non-reverse redistribution segments). For the prediction of post-revascularization recovery in asynergic segments, the detection of reverse redistribution on rest-redistribution ²⁰¹Tl SPET does not add any information to the quantitative analysis of redistribution activity. Received 19 November 1997 and in revised form 20 February 1998     

Pulsed Doppler tissue imaging for the assessment of myocardial viability: comparison with 99mTc sestamibi perfusion imaging

The aim of the present study was to examine whether Doppler tissue imaging demonstrated comparable diagnostic performance for the detection of viable myocardium compared to myocardial perfusion imaging with Tc hexakis-2-methoxyisobutylisonitrile (MIBI). We studied 30 patients with old myocardial infarction who underwent percutaneous transluminal coronary angioplasty (PTCA). Myocardial single photon emission computed tomography (SPECT) with Tc-MIBI and two-dimensional echocardiography were carried out within 7 days before PTCA. We measured regional Tc-MIBI uptake for each myocardial segment from SPECT and peak systolic velocity and a ratio of regional pre-ejection period to regional ejection time (PEP/ET) from pulsed Doppler tissue imaging. Biplane left ventriculography was performed before interventional procedures and repeated 3 months after PTCA. Myocardial viability was determined when wall motion was improved at least one grade after PTCA. The peak systolic velocity was positively correlated with regional Tc-MIBI uptake (R =0.59, P<0.01). The PEP/ET demonstrated inverse correlation with Tc-MIBI uptake ( R=-0.59, P<0.01). Peak systolic velocity of viable segments was higher than that of non-viable segments ( P<0.05). The PEP/ET was lower in viable segments than in non-viable segments ( P<0.05). Peak systolic velocity and PEP/ET demonstrated high diagnostic accuracy for detecting viable myocardium compared with Tc-MIBI perfusion imaging (80% and 79% vs 90%). These data indicate that measurements of regional peak systolic velocity and PEP/ET by Doppler tissue imaging are useful for evaluating myocardial viability quantitatively and provide helpful information for a clinical judgment in an interventional strategy.     

Clinical significance of denervated but viable myocardium in patients with recanalized acute myocardial infarction.

In patients with acute myocardial infarction (MI), myocardial sympathetic innervation evaluated by 123I-metaiodobenzylguanidine myocardial scintigraphy is more sensitive to ischaemia than the associated perfusion abnormality of 201Tl myocardial scintigraphy. The purpose of this study was to evaluate the scintigraphic indices related to the recovery of left ventricular function after acute MI. 123I-metaiodobenzylguanidine and 201Tl-chloride imaging were performed in 15 patients (mean age 60 years, 13 men and 2 women) 2 weeks after the onset of acute MI. Using a 20-segment visual interpretation of the 201Tl image, myocardial segments were classified into persistent defect, redistribution or reverse redistribution, and normal 201Tl uptake. The extent of denervated segments showed a fair correlation with the ejection fraction on admission (r = -0.53, P = 0.04), whereas the extent of persistent defect had a close correlation with the ejection fraction at 4 months (r = -0.79, P = 0.01). There was a good correlation between the extent of denervated but viable myocardium and the change in ejection fraction from admission to 4 months (r = 0.68, P = 0.01). Thus, denervated but viable myocardium is a scintigraphic index related to the functional recovery of left ventricular pump function after acute MI.     

Enhanced regional washout of technetium-99m-sestamibi in patients with coronary spastic angina

BACKGROUND: Reverse redistribution and rapid washout of 99mTc-sestamibi are observed in patients with acute myocardial infarction and may indicate viable myocardium. However, the clinical significance of this phenomenon has not been rigorously examined in other cardiac diseases. Thus, we investigated whether reverse redistribution and washout of 99mTc-sestamibi could be used in the diagnosis and follow-up of patients with coronary spastic angina. METHODS: Thirty patients diagnosed as coronary spastic angina were examined. During coronary arteriography, spasm was induced by provocation test with ergonovine, and only total or subtotal occlusion was considered positive. Myocardial perfusion tomography was obtained 45 min (early) and 3 hr (delayed) after 99mTc-sestamibi injection. Segmental defect score was visually graded from 0 (normal) to 4 (defect), and a total defect score was determined as the sum of defect scores for all segments. Washout rate of 99mTc-sestamibi from the myocardium was calculated for each segment. After medical treatment with calcium antagonists and nitrates for 3 months, 99mTc-sestamibi imaging was repeated. RESULTS: Out of 30 patients, on the early images 17 (57%) patients demonstrated decreased 99mTc-sestamibi uptake in spastic segments; on the other hand, 24 (80%) patients did decreased 99mTc-sestamibi uptake in spastic segments on delayed images. Total defect scores in delayed images were higher than those in early images (6.9 +/- 0.3 vs. 3.6 +/- 0.4, p < 0.01). Reverse redistribution of 99mTc-sestamibi was observed in 17 out of 30 patients (57%) with coronary spastic angina. Washout rate of 99mTc-sestamibi from spastic segments was higher than that from non-spastic segments (16 +/- 2% vs. 11 +/- 5%, p < 0.01). After medical treatment, washout rate from spastic segments was decreased to 10 +/- 4 (p < 0.01), and left ventricular ejection fraction was increased from 63 +/- 8% to 73 +/- 4% (p < 0.01). CONCLUSION: Rapid washout of 99mTc-sestamibi was observed in patients with coronary spastic angina and might indicate that the ability of myocyte to retain the tracer was impaired due to repetitive brief ischemia by coronary spasm. The early and delayed 99mTc-sestamibi imaging provides useful information for the diagnosis and responses to the treatment in patients with coronary spastic angina.     

Clinical variables that can cause the underestimation of the viable myocardium in the infarcted area: results of the sequential exercise thallium-201 myocardial scintigraphy

Clinical variables that can cause the underestimation of the viable myocardium were examined in the sequential exercise thallium-201 study before and after PTCA. Among 60 patients who had documented myocardial infarction with single coronary artery disease, 43 patients had successful PTCA. Compared to the initial images after PTCA, the 4 hour-delayed images before PTCA had larger and more severe defect in the infarcted area of 14 patients (33%). This underestimated group had shorter period from the infarction to the stress study. (3.4 +/- 2.4 M vs. 7.1 +/- 9.2 M; p less than 0.05), and attained more maximal heart rate during the stress study. The numbers of the patients who had severe stenosis (greater than or equal to 99%) were more in the underestimated group (79% vs. 34%; p less than 0.01). The patients who have recent myocardial infarction, especially within three months, are likely to be underestimated their viable myocardium in the infarcted area, and this variable is dependent from their workload during the stress study and the severity of the stenotic lesion which also affect the estimation of the myocardial viability.     

Clinical significance of 201Tl reverse redistribution in patients with aorto-coronary bypass surgery

Detection of myocardial ischemia by the stress thallium scan has traditionally been performed using transient defect analysis on exercise, followed by redistribution studies. Worsening of the 201Tl myocardial image from exercise to redistribution is referred to as reverse redistribution. In this study, we found reverse redistribution in 10 (21%) of 48 angina pectoris patients who had undergone aortocoronary bypass surgery. The clinical significance of this phenomenon in these patients was investigated in relation to angiographic and surgical findings. Reverse redistribution was found to occur in regions which were supplied by bypass grafts. These areas showed increased coronary blood flow and rapid thallium washout. Our results indicate that a perfusion defect in the bypass region of the redistribution image might be caused by relatively rapid washout in the bypass graft region compared to the adjacent normal myocardium. These results should be considered in the clinical interpretation of stress thallium scans.     

Clinical significance of 201Tl reverse redistribution in patients with aorto-coronary bypass surgery

Detection of myocardial ischemia by the stress thallium scan has traditionally been performed using transient defect analysis on exercise, followed by redistribution studies. Worsening of the ²⁰¹Tl myocardial image from exercise to redistribution is referred to as reverse redistribution. In this study, we found reverse redistribution in 10 (21%) of 48 angina pectoris patients who had undergone aortocoronary bypass surgery. The clinical significance of this phenomenon in these patients was investigated in relation to angiographic and surgical findings. Reverse redistribution was found to occur in regions which were supplied by bypass grafts. These areas showed increased coronary blood flow and rapid thallium washout. Our results indicate that a perfusion defect in the bypass region of the redistribution image might be caused by relatively rapid washout in the bypass graft region compared to the adjacent normal myocardium. These results should be considered in the clinical interpretation of stress thallium scans.     

Selective intracoronary injection of sestamibi to detect myocardial viability: Prediction of perfusion and contractile recovery after percutaneous transluminal coronary angioplasty

BACKGROUND: The main limitation of myocardial single photon emission computed tomography (SPECT) in detecting hibernating myocardium is the poor delivery of radiotracers in hypoperfused areas supplied by severely stenotic coronary arteries. Increasing local availability of radiotracers by intracoronary injection might represent an attractive solution. The hypothesis that the intracoronary administration of sestamibi could improve myocardial SPECT accuracy in detecting hibernating myocardium was addressed in this pilot study. METHODS AND RESULTS: Seven patients with prior myocardial infarction and severe stenosis of the infarct-related artery underwent myocardial SPECT after intracoronary injection of technetium 99m sestamibi immediately before percutaneous transluminal coronary angioplasty (PTCA). Wall motion and perfusion were evaluated, before and 1 month after PTCA, by 2-dimensional echocardiography and rest-redistribution thallium 201 SPECT. A "low-flow area" was identified on the pre-PTCA Tl-201 SPECT image as the area with less than 50% of maximum radiotracer uptake. Changes in wall motion and perfusion in the low-flow area were compared with results of intracoronary sestamibi imaging. On a pixel-by-pixel analysis, intracoronary sestamibi predicted perfusion recovery within the low-flow area with a 91% sensitivity, a 78% specificity, and an 82% overall accuracy. Only in the 5 patients with an extent of sestamibi uptake greater than one third of the low-flow area was an improved regional and global left ventricular wall motion observed after PTCA (wall motion score index decreased from 1.95 +/- 0.28 to 1.60 +/- 0.34, P =.007; left ventricular ejection fraction increased from 42% +/- 7% to 49% +/- 7%, P =.001; asynergic segments in the low-flow area decreased from 3.6 +/- 0.9 to 1.8 +/- 1.5, P =.021). CONCLUSIONS: In patients with prior myocardial infarction and severe stenosis of the infarct-related artery, sestamibi uptake after intracoronary administration identified viable myocardium that was undetected after rest-redistribution thallium SPECT but capable of clinically significant contractile improvement after revascularization.