Detecting myocardial salvage after primary PTCA: early myocardial contrast echocardiography versus delayed sestamibi perfusion imaging.

The extent of myocardial salvage after primary percutaneous transluminal coronary angioplasty (PTCA) in acute myocardial infarction (AMI) is variable and cannot be predicted on the basis of either vessel patency or early regional wall motion assessment. The aim of this study was to evaluate the reliability of microvascular integrity, as shown by myocardial contrast echocardiography (MCE), as an indicator of tissue salvage and a predictor of late functional recovery, and to compare MCE with the quantification of tracer activity in sestamibi perfusion imaging. METHODS: Twenty-six patients with AMI who received successful treatment with primary PTCA were examined with MCE during cardiac catheterization immediately before and after vessel recanalization. Myocardial contrast effect was scored as 0 (absent), 0.5 (partial) or 1 (normal). Wall motion was assessed by two-dimensional echocardiography on admission and 1 mo later with a 16-segment model and 4-point score. Resting sestamibi SPECT was collected within 1 wk after AMI. The risk area was defined by MCE as the sum of the segments with no perfusion (score 0) before PTCA. Myocardial viability was defined by MCE as an increase in contrast score in the same segments after PTCA and by sestamibi SPECT as a preserved tracer activity (>60% of peak activity). The functional recovery after 1 mo detected by two-dimensional echocardiography was the reference standard for viability. RESULTS: A total of 50 segments showed perfusion defects before PTCA (risk area). Immediately after PTCA, the MCE score increased in 44 of 50 segments, whereas sestamibi SPECT showed preserved activity in 22 of 50 segments. After 1 mo, the wall motion score decreased in 22 of 50 segments (viable segments) and was unchanged in the remaining 28 segments. Thus, MCE showed a sensitivity of 91% and a specificity of 14% in detecting viable myocardium, whereas sestamibi SPECT showed a lower sensitivity (68%) but a significantly higher specificity (75%; P < 0.00001). The positive predictive values were 45% and 68% for MCE and SPECT (P < 0.005), respectively, and the negative predictive values were 67% and 71%, respectively. On a patient basis, SPECT was more specific (79% versus 21%; P < 0.01) and showed a higher overall predictive accuracy (88% versus 50%; P < 0.01) than MCE. CONCLUSION: The demonstration of microvascular integrity by MCE performed immediately after primary PTCA has a limited diagnostic value in predicting salvaged myocardium. Conversely, tracer activity quantification in resting sestamibi SPECT performed in a later stage is confirmed to be a reliable approach for recognizing myocardial stunning and predicting functional recovery.     

Consideration of perfusion reserve in viability assessment by myocardial Tl-201 rest-redistribution SPECT: A quantitative study with dual-isotope SPECT

BACKGROUND: To optimize the use of thallium 201 rest-redistribution study in Tl-201/technetium 99m sestamibi dual-isotope single photon emission computed tomography (SPECT), the predictability of Tl-201 rest-redistribution for viable myocardium was examined according to the degree of perfusion reserve. METHODS AND RESULTS: Twenty patients with both unstable angina and left ventricular dysfunction were enrolled. Tl-201 rest-dipyridamole stress Tc-99m sestamibi gated SPECT/Tl-201 24-hour redistribution SPECT was performed before and 3 months after coronary artery bypass grafting. Through use of a 20-segment model, segmental stress perfusion, rest perfusion, and systolic thickening were quantified on gated SPECT by means of automatic quantitation software. Perfusion was expressed as the average percentage of maximal radioactivity uptake. To represent perfusion reserve, the perfusion difference score (PDS) was defined as rest perfusion minus stress perfusion. A low PDS indicated little or no inducible ischemia, and a high PDS indicated inducible ischemia. In dysfunctional myocardium, viability was defined by the improvement of thickening after coronary artery bypass grafting. The overall predictability of Tl-201 redistribution for viability was 0.709 of the area under the curve (AUC) in receiver operating characteristic analysis. With a cutoff of 7, predictability was significantly better in the low PDS group (AUC = 0.785) than in the high PDS group (AUC = 0.582). CONCLUSIONS: The predictability of Tl-201 rest-redistribution for viability differs according to perfusion reserve. It was more reliable for dysfunctional myocardium with persistent perfusion decrease. On the basis of the continuum hypothesis of chronic stunning and hibernation, we suggest that dysfunctional myocardium with persistent perfusion decrease should be assessed by Tl-201 redistribution SPECT.     

Prediction of left ventricular wall motion recovery after acute myocardial infarction by T1-201 gated SPECT: Incremental value of integrated contractile reserve assessment

BACKGROUND: This investigation tested the application of low-dose dobutamine (LDD) gated single photon emission computed tomography (SPECT) with thallium 201 for myocardial viability detection early after acute myocardial infarction (AMI). METHODS AND RESULTS: Thirty-two hemodynamically stable post-AMI patients (aged 55 +/- 5 years [mean +/- SEM]; 20 men) who were exhibiting regional left ventricular dysfunction underwent stress-redistribution Tl-201 scanning within 4 to 8 days, followed by 2 additional gated SPECT acquisitions after Tl-201 reinjection, at rest and during LDD. A visual 5-point score was computed for segmental radiotracer uptake (0, normal; 4, absent) and a 4-point score for left ventricular wall motion (1, normal; 4, dyskinesis). Predominant viable myocardium in dyssynergic regions was predicted by a mean Tl-201 uptake score of 2 or less or ischemic area of 30% or greater. These indices showed a significant association with wall motion improvement in follow-up echocardiographic studies (overall accuracy = 0.69, sensitivity = 0.93, and specificity = 0.50). Regarding the response to LDD stimulus, an increase in mean wall motion score of 30% or greater was predictive of predominant viable myocardium. Contractile reserve assessment yielded a significant increment in the predictive accuracy for function recovery (overall accuracy = 0.84, sensitivity = 0.71, and specificity = 0.94). CONCLUSIONS: Evaluation of contractile reserve by means of LDD gated SPECT with Tl-201 is safely feasible early after AMI, with incremental value over perfusion assessment alone for myocardial viability detection.     

Clinical significance of reverse redistribution in exercise thallium-201 SPECT after percutaneous transluminal coronary angioplasty

Clinical significance of reverse redistribution on thallium image was evaluated in 54 patients who had undergone PTCA. Thallium SPECT imaging was performed one week and three to six months after PTCA. Reverse redistribution was detected eight of 54 patients one week after PTCA and five of 38 patients three to six months after PTCA. In the segments with reverse redistribution, reduced regional wall motion and lesser degree of coronary stenosis was common features (p less than 0.05) angiography. In conclusion, reverse redistribution had a tendency to appear in the region with mild myocardial injury and relatively high coronary blood flow after PTCA. But in cases with new occurrence and disappearance of reverse redistribution during follow up period, we can not assess the factors to explain these phenomena. In these segments, "coronary flow reserve", "stunned myocardium", "hibernating myocardium" or other factors may be related.     

Assessment of regional wall motion and perfusion by multigated myocardial scintigraphy after intracoronary Tl-201

Fourteen patients undergoing intracoronary thrombolysis for acute myocardial infarction had intracoronary injection of thallium-201 to assess myocardial salvage after reperfusion. Scintigrams of the perfused myocardium were gated and compared with both ungated scans and radionuclide ventriculograms (multigated blood pool scintigrams) to determine the value of gated perfusion images for studies of both perfusion and regional wall motion. Multigated and ungated thallium images provided comparable information about regional myocardial perfusion. Correlation between multigated thallium images of regional wall motion and radionuclide ventriculograms was poor (tau = 0.44). Assessment of wall motion was most accurate in well-perfused segments and least accurate in partially perfused segments.     

Postrevascularization recovery of fatty acid utilization in ischemic myocardium: A randomized clinical trial of potassium channel opener

BACKGROUND: Abnormal fatty acid metabolism persists in hibernating myocardium, even after reperfusion. This study was designed to determine whether the K+ channel opener, nicorandil, improves fatty acid utilization after percutaneous transluminal coronary angioplasty (PTCA). METHODS: Patients undergoing elective PTCA were randomly assigned to treatment (group N, n = 26) or control groups (group C, n = 22). Group N received intracoronary and intravenous nicorandil during PTCA. Myocardial fatty acid use and perfusion were quantitatively evaluated by means of iodine-123-beta-methyl-p-iodophenyl-pentadecanoic acid single photon emission computed tomography (I-123 BMIPP SPECT) and thallium-201 (Tl-201) imaging before PTCA, 72 hours after PTCA, and 3 months after PTCA. Left ventricular function was also evaluated by means of contrast ventriculography before and 3 to 6 months after PTCA. RESULTS: The 1-123 BMIPP defect score in group N significantly decreased, from 28%+/-13% to 20%+/-20% after PTCA and to 18%+/-17% 3 months later. In contrast, the I-123 BMIPP defect score in group C increased from 28%+/-20% to 36%+/-15% (P<.05 versus group N) after PTCA, then returned to 28%+/-17% (P<.05 versus group N) 3 months after PTCA. Recovery of left ventricular function paralleled the recovery of I-123 BMIPP uptake. CONCLUSIONS: Nicorandil improves the recovery of myocardial fatty acid utilization and cardiac function after PTCA. K(ATP) channel activation may have a protective effect during coronary artery occlusion and improve subsequent recovery.     

Simultaneous assessment of Tc-99m-sestamibi and I-123-BMIPP myocardial distribution in patients with myocardial infarction: Evaluation of left ventricular function with ECG-gated myocardial SPECT

123I-labeled 15-(p-iodophenyl)-3R,S-methyl pentadecanoic acid (BMIPP) is a branched-chain free fatty acid that is used to evaluate various cardiac diseases. The aim of the present study was to investigate the relationship between myocardial perfusion (99mTc-sestamibi) and BMIPP uptake, and to correlate perfusion and metabolic alterations with regional left ventricular dysfunction in patients with myocardial infarction (MI). ECG-gated dual-isotope myocardial SPECT was performed on 130 patients with MI with sestamibi (555 MBq) and BMIPP (148 MBq). The patients were classified into 3 groups according to PTCA therapy and the interval between the onset of infarction and RI injection (OR time). Group A (n = 56) included patients whose OR time was less than one month and who had undergone successful PTCA, Group B (n = 36) had OR times of less than one month and had conservative medical therapy, and Group C (n = 38) had OR times of over one month. The severity scores of the dual-isotope images were calculated from the defect scores in 9 segments. From the ECG-gated SPECT data with sestamibi, the left ventricular ejection fraction (LVEF; %) and regional wall motion were determined automatically using the QGS program LVEF obtained from gated SPECT correlated well with the severity scores for sestamibi and BMIPP (r = -0.68 and -0.76, respectively). The delta severity scores (BMIPP scores - sestamibi scores) of Group A were significantly higher than those of the other two groups (3.6 +/- 3.0 vs. 1.5 +/- 1.7 and 1.0 +/- 1.4, p < 0.001 ). The rate of dysfunctional segments with normal sestamihi distribution was significantly higher in Group A than in Group C (20.7% vs. 6.7%, p < 0.001). ECG-gated dual-isotope SPECT is useful since myocardial perfusion, fatty acid metabolism and left ventricular function can be analyzed during a single examination, so that this procedure has the potential to provide comprehensive information when evaluating patients with ischemic heart disease.     

201Tl-reverse redistribution in a case with stunned myocardium

A 58-year-old man was admitted to our hospital because of chest pain. Electrocardiogram showed giant negative T waves in leads I, II, III, aVl, aVf and V2 through V6. Echocardiogram showed anterior wall motion abnormality. Rest-redistribution thallium scan obtained 3 days after admission revealed reverse redistribution in antero-apical area. Coronary angiogram showed no significant stenotic lesions and left ventriculogram in chronic stage showed improvement of wall motion abnormality. Repeat thallium scan in chronic stage showed disappearance of perfusion defect in apical area. It was difficult to diagnose myocardial viability in our case with stunned myocardium because rest-redistribution thallium scan showed reverse redistribution. As the mechanism of this finding, early coronary recanalization in acute stage of the event was suspected.     

Intracoronary versus intravenous injection of 99mTc-tetrofosmin: comparison of myocardial perfusion patterns and wall motion

OBJECTIVES: The accuracy of viability and defect size detection by Tc-tetrofosmin has been discussed by several authors. The lower myocardial extraction fraction of the latter compared with Tc-sestamibi or Tl has often been emphasized. We hypothesized that the intracoronary (i.c.) injection of tracer activity, i.e. higher than that theoretically achievable in the case of intravenous (i.v.) administration, could demonstrate the clinical relevance of this finding intra-individually. In this study, myocardial perfusion images obtained after tracer injection down the infarct-related artery were compared with i.v. injection images in the same patients. The trial also provided us with the opportunity to compare the wall motion values calculated using conventional Tc-tetrofosmin gated single-photon emission computed tomography (SPECT) studies with those obtained using optimal target/background ratios after i.c. injection. METHODS: Fourteen patients with acute myocardial infarction, no history of previous cardiac events, single vessel disease and no visible collaterals in the coronary arteriogram were included in the study. Electrocardiogram gated SPECT was carried out separately after i.c. and i.v. injections of the tracer within 5-7 days following thrombolytic therapy. Myocardial perfusion patterns were compared by contingency table analysis after semi-quantitative visual scoring. Segmental wall motion was compared using quantified polar map data in a subset of patients (eight of 14) with normal to moderately hypoperfused myocardium supplied by the left coronary artery. RESULTS: Visual perfusion scores of both studies showed good concordance (kappa, 0.70), with complete agreement in 94 of 119 segments. Nearly all of the discordant segments (24 of 25) were mildly better scored in i.c. studies than in i.v. studies. The mean wall motion values calculated on polar maps of 78 segments for i.c. and i.v. studies were 8.4 +/- 1.2 mm and 8.2 +/- 1.3 mm (mean Delta wall motion=0.23 mm), respectively. High segmental wall motion correlation was observed (R=0.90; P<0.0001). CONCLUSION: It can be concluded that infarct-related myocardial perfusion scores obtained after i.c. and i.v. injections of Tc-tetrofosmin compare favourably, with a total agreement rate of 79%. However, the additional information obtained in 21% of the total number of myocardial segments by i.c. injection may indicate a mild underestimation of myocardial viability by i.v. injection. Conventional gated SPECT using i.v. Tc-tetrofosmin was demonstrated to be a reliable technique in the detection of true wall motion.     

Influence of infarct-zone viability detected by rest Tc-99m sestamibi gated SPECT on left ventricular remodeling after acute myocardial infarction treated by percutaneous transluminal coronary angioplasty in the acute phase

BACKGROUND: The purpose of this study was to assess the value of technetium 99m sestamibi gated single photon emission computed tomography (SPECT) in predicting the evolution of left ventricular volumes in patients treated successfully in the acute phase of a myocardial infarction (MI). METHODS AND RESULTS: Twenty-nine patients with acute MI and early percutaneous transluminal coronary angioplasty (PTCA) were included in this study. A rest Tc-99m sestamibi electrocardiography (ECG)-gated SPECT study was performed 21 +/- 5 days after PTCA. The myocardial perfusion index was calculated by use of a semiautomatic sectorial analysis. All patients had contrast ventriculography performed during the acute phase and 6 months later. The patients were separated into two groups according to the absence (group I, n = 21) or presence (group II, n = 8) of end-systolic enlargement. The perfusion index in the infarct sectors was -2.29 +/- 2.90 SD in group I and -6.40 +/- 2.85 SD in group II ( P < .01). With a cutoff value of -2.46 SD, the sensitivity and specificity of Tc-99m sestamibi SPECT for the prediction of end-systolic volume enlargement were 100% and 62%, respectively. When the functional data from ECG-gated acquisitions were added, specificity increased to 86%. CONCLUSIONS: Despite successful PTCA in the acute phase of MI, an increase in end-systolic volume was observed at 6 months in 28% of patients. Tc-99m sestamibi ECG-gated SPECT performed 3 weeks after the acute phase could predict this enlargement with a high accuracy.     

Comparative performance of gated perfusion SPECT wall thickening, delayed thallium uptake, and F-18 fluorodeoxyglucose SPECT in detecting myocardial viability

To evaluate the comparative abilities of gated single photon emission computed tomography (SPECT) wall thickening, delayed thallium-201 (Tl-201) SPECT, and F-18 fluorodeoxyglucose (FDG) SPECT in detecting myocardial viability, 23 patients with previous myocardial infarction and clinically suspected viability were studied. Each patient had at least 1 extensive fixed perfusion defect on rest/stress technetium-99m sestamibi SPECT. A total of 41 major vascular territories had fixed defects. The mean (+/- 1 SD) left ventricular ejection fraction determined from gated perfusion SPECT was 26% +/- 11%. Wall thickening was assessed in a semiquantitative fashion by the regional increase in myocardial intensity during systole and was considered normal when a > or = 20% increase was observed. Tl-201 SPECT was acquired 4 hours after resting tracer injection was administered. Viability was considered present when regional defect Tl-201 count density, determined by quantitative analysis, was > 20% greater than that on the resting sestamibi scan. FDG SPECT was performed independently with a 10 mCi F-18 FDG dose after oral glucose loading was performed. A camera equipped with ultrahigh energy collimation was used. Quantitative criteria for viability were the same as for Tl-201. In the 23 patients viability within the fixed sestamibi defects was manifest by preserved wall thickening in 8 patients, delayed Tl-201 uptake in 10 patients, and FDG uptake in 18 patients. Nine major vascular territories with fixed defects were judged viable by wall thickening, 11 by Tl-201 SPECT, and 24 by FDG SPECT (P = .0009). We conclude that FDG SPECT demonstrates more evidence of myocardial viability than either gated sestamibi wall thickening or delayed Tl-201 SPECT.     

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.     

Serial assessment of left ventricular function during dobutamine stress by means of electrocardiographygated myocardial SPECT: Combination with dual-isotope myocardial perfusion SPECT for detection of ischemic heart disease

BACKGROUND: Technetium-labeled myocardial perfusion tracers allow simultaneous assessment of myocardial perfusion and left ventricular function by electrocardiography (ECG)-gated myocardial single photon emission computed tomography (SPECT). The purpose of this study was to evaluate left ventricular performance during dobutamine stress by means of ECG-gated myocardial perfusion SPECT with short-time data collection. METHODS AND RESULTS: After administration of Tc-99m sestamibi or tetrofosmin (600-740 MBq), 67 patients with ischemic heart disease, including 35 with prior myocardial infarction, were examined by ECG-gated myocardial perfusion SPECT at rest and during dobutamine stress (at dosages of 4, 8, 12, 16, and 20 microg/kg/min, with increments every 8 minutes). The ECG-gated data collection time was 5 minutes for each dobutamine dosage. After acquisition of gated SPECT data at the highest dose, thallium 201 chloride (111 MBq) was injected, and dual-isotope SPECT was also performed to assess the myocardial ischemia. In 32 patients without prior myocardial infarction, the sensitivity of individual stenosed-vessel detection with dual-isotope perfusion SPECT, with wall motion abnormality obtained from gated SPECT, and with the combined method was 55.9%, 52.9%, and 73.5%, respectively, based on coronary angiography. ECG-gated SPECT during dobutamine infusion revealed regional wall motion abnormalities (worsening or biphasic response) in 19 (57.6%) of 33 infarcted areas with culprit coronary arterial stenosis. The prevalence of reversible perfusion defects on dual-isotope SPECT was higher in segments with wall motion abnormalities than in segments with normal wall motion response (89.5% vs 42.9%, P <.02). CONCLUSIONS: Myocardial perfusion and left ventricular function during dobutamine infusion were analyzed in a single examination by means of the combined method. This procedure has the potential to provide comprehensive information with which to evaluate patients with ischemic heart disease.     

Usefulness of early tetrofosmin myocardial SPECT during subacute period to estimate salvaged myocardium in patients with acute myocardial infarction--comparing with tetrofosmin myocardial SPECT during chronic period and evaluating regional wall motion using QGS method

To evaluate salvaged myocardium of acute myocardial infarction (AMI), we performed rest 99mTc-tetrofosmin (TF) SPECT with rest Tl and Tc-pyrophosphate (PYP) dual SPECT within 10 days after admission in 19 patients with initial AMI, who all were reperfused successfully and without restenosis. TF SPECT was obtained at 15 minutes (E) after tracer injection, 4 hours later (D), and 5 months later (FU). We calculated the regional uptake score (RUS) of infarcted area estimated by Tc-PYP uptake and defined RUS(FU) of TF(FU) as salvaged myocardium, and then regarded RUS/RUS(FU) x 100 (%) as subacute predicted value of salvaged myocardium. Furthermore, we regarded the improvement of wall motion estimated by QGS method as the guidepost of myocardial viability. The subacute predicted value of TF(E) was 85 +/- 25%, which was significantly higher than 61 +/- 28% of Tl and 36 +/- 24% of TF(D) (p < 0.01). Sensitivity and specificity of myocardial viability based on the improvement of wall motion SPECT image were 78% and 73% for Tl, 90% and 87% for TF(E) and 52% and 87% for TF(D). TF myocardial early imaging in subacute period was useful to detect salvaged myocardium.     

Fatty acid imaging with 123I-15-(p-iodophenyl)-9-R,S-methylpentadecanoic acid in acute coronary syndrome.

123I-15-(p-iodophenyl)-9-R,S-methylpentadecanoic acid (9-MPA) has recently been developed as a tracer for myocardial fatty acid uptake. The aim of this study, which was performed as part of a phase III clinical trial of 9-MPA, was to test the usefulness of 9-MPA for the assessment of myocardial viability in patients with acute coronary syndrome (ACS). METHODS: Fifteen patients with ACS who had undergone direct percutaneous transluminal coronary angioplasty were examined. Myocardial SPECT with 9-MPA and 99mTc-sestamibi and low-dose dobutamine echocardiography were performed within 2 wk after onset. The 9-MPA images were obtained 10 and 60 min after tracer administration, and sestamibi imaging was begun 60 min after the injection. The left ventricle was divided into 9 segments, and 9-MPA and sestamibi uptake were scored from 0 (normal) to 3 (no activity) in each segment. Lower uptake of 9-MPA than of sestamibi was defined as a mismatch. Myocardial segments showing improvement in wall motion during low-dose dobutamine infusion (5-10 microg/kg/ min) were considered viable. RESULTS: The 9-MPA images were of high quality for all patients. Myocardial uptake of 9-MPA was lower in ischemic myocardium than in nonischemic myocardium (58.2%+/-14.2% versus 91.9%+/-6.5%, P<0.0001). Clearance of 9-MPA from ischemic myocardium was slower than that from nonischemic myocardium (10.2%+/-11.7% versus 19.1%+/-5.9%, P<0.01). A mismatch was seen in 10 of 15 patients, and 18 of 20 (90%) mismatched segments were defined as viable by dobutamine echocardiography. Conversely, 18 of 20 (90%) matched segments did not show any improvement in function during dobutamine stimulation (P<0.0001). Uptake of 9-MPA in nonviable segments was lower than that in dysfunctional but viable segments (P<0.05), and 9-MPA clearance from nonviable segments was slower than that from viable segments (P<0.05). CONCLUSION: The imaging characteristics of 9-MPA for SPECT are excellent, allowing noninvasive assessment of myocardial fatty acid uptake. Myocardial imaging with 9-MPA may reveal impaired fatty acid uptake in dysfunctional but viable myocardium and thus provide useful information for clinical decision making in ACS.     

Technetium 99m furifosmin regional myocardial uptake in patients with previous myocardial infarction: Relation to thallium-201 activity and left ventricular function

BACKGROUND: This study was designed to compare the results of rest-redistribution thallium-201 imaging with those of rest technetium 99m furifosmin single photon emission computed tomography in the same patients with chronic ischemic left ventricular (LV) dysfunction. METHODS: Twenty-one patients (mean age 62 +/- 9 years) with chronic myocardial infarction and LV dysfunction (mean LV ejection fraction 34% +/- 8%) underwent rest-redistribution thallium imaging and resting furifosmin single photon emission computed tomography on the same day. In each patient, regional thallium and furifosmin activity was quantitatively measured in 13 myocardial segments. Regional LV function was assessed in corresponding segments by echocardiography. RESULTS: At thallium imaging, 91 (33%) segments had normal uptake, 16 (6%) showed reversible defects, and the remaining 166 (61%) irreversible defects. Of these 166 irreversible defects, 74 (45%) had moderate (> or =58% of peak activity) and 92 (55%) severe (<58% of peak activity) reduction of thallium uptake. Regional furifosmin uptake was significantly related to both rest (r = 0.87, P < .0001) and redistribution (r = 0.90, P < .0001) thallium activity. Agreement in the evaluation of regional perfusion status between thallium and furifosmin imaging was observed in 70% of the 84 hypokinetic segments (kappa = 0.54) and in 76% of the 78 akinetic or dyskinetic segments (kappa = 0.60). Concordance in the detection of myocardial viability between thallium and furifosmin imaging was observed in 69 (82%) of hypokinetic regions (kappa = 0.60) and in 65 (83%) of akinetic or dyskinetic regions (kappa = 0.67). CONCLUSIONS: These results suggest that in patients with chronic coronary artery disease and LV dysfunction, quantitative rest-redistribution thallium scintigraphy and furifosmin tomography at rest provide similar results in the evaluation of perfusion status and in the detection of myocardial viability.     

Acute myocardial infarction: evaluation with first-pass enhancement and delayed enhancement MR imaging compared with 201Tl SPECT imaging

PURPOSE: To evaluate acute myocardial infarction by using first-pass enhancement (FPE) and delayed enhancement (DE) magnetic resonance (MR) imaging compared with thallium 201 ((201)Tl) single photon emission computed tomography (SPECT). MATERIALS AND METHODS: Contrast material-enhanced FPE MR, inversion-recovery DE MR, and rest-redistribution (201)Tl SPECT images were obtained in 60 consecutive patients (53 men, seven women; mean age [+/- SD], 56 years +/- 13; range, 30-78 years) at 6 days +/- 3 after reperfused first myocardial infarction. Presence of microvascular obstruction was determined on FPE MR images. Infarct size was defined on DE MR images as percentage of left ventricular (LV) area and compared with uptake defect on redistribution (201)Tl SPECT images. Differences in continuous data were analyzed with Student t test. Linear regression and Bland-Altman analysis were used to compare measurements of infarct size. RESULTS: Mean infarct size was not significantly different between DE MR imaging (20.7% +/- 11.5% of LV area) and (201)Tl SPECT (19.4% +/- 14.3% of LV area; P =.26); good correlation (r = 0.73; P <.001) and agreement were found, with a mean difference of +1.3% +/- 9.8% of LV area. (201)Tl SPECT failed to depict infarct in six (20%) of 30 patients with inferior myocardial infarction (mean size, 6.4% +/- 5.7% of LV area on DE MR images), whereas DE MR images showed the infarct in all patients (P <.01). FPE MR images depicted microvascular obstruction in 23 (38%) of 60 patients; these patients had larger infarctions at DE MR imaging than did patients without microvascular obstruction (30.4% +/- 9.0% vs 15.1% +/- 8.4% of LV area, P <.001). (201)Tl SPECT showed larger infarcts in patients with microvascular obstruction (26.7% +/- 16.2% vs 15.0% +/- 11.2% of LV area, P <.01). CONCLUSION: Good correlation and agreement with (201)Tl SPECT indicate DE MR imaging may be used to estimate infarct size 6 days after reperfused acute myocardial infarction. DE MR imaging is more sensitive for detection of inferior infarction than is (201)Tl SPECT. Patients with microvascular obstruction on FPE MR images have larger infarcts.     

Tetrofosmin imaging in the detection of myocardial viability in patients with previous myocardial infarction: comparison with sestamibi and tl-201 scintigraphy

BACKGROUND: Technetium 99m tetrofosmin has been introduced as a myocardial perfusion agent, providing similar results to those of thallium 201 and sestamibi in the identification of patients with coronary artery disease. No data are available comparing tetrofosmin and sestamibi imaging in the identification of reversible left ventricular (LV) dysfunction in the same patients. This study compared the results of tetrofosmin, thallium, and sestamibi single photon emission computed tomography at rest in detection of myocardial viability in patients with previous myocardial infarction. METHODS AND RESULTS: Seventeen patients with previous myocardial infarction who were undergoing coronary revascularization were studied. Echocardiography was performed at baseline and 3 months after revascularization to evaluate recovery of LV function. The optimal threshold cutoffs to separate reversible from irreversible dysfunction, as determined by receiver operating characteristic analysis, were 55% of peak activity for both tetrofosmin and sestamibi and 60% for thallium. In all asynergic segments (n = 77) analyzed, tetrofosmin uptake correlated with both sestamibi (r = 0.90, P <.0001) and thallium (r = 0.85, P <.0001) activity. The sensitivity and specificity for reversible dysfunction were, respectively, 70% and 70% for tetrofosmin, 70% and 66% for sestamibi, and 60% and 68% for thallium imaging (all P = not significant). The areas under the receiver operating characteristic curves constructed for tetrofosmin, thallium, and sestamibi activity were 0.74 +/- 0.06 (mean +/- SD), 0.75 +/- 0.06, and 0.74 +/- 0.06, respectively (all P = not significant). Concordance for detecting myocardial viability between tetrofosmin and thallium imaging was found in 67 regions (87%) (kappa = 0.74), and concordance between tetrofosmin and sestamibi imaging was found in 69 regions (90%) (kappa = 0.79). CONCLUSIONS: The diagnostic performance of quantitative rest tetrofosmin single photon emission computed tomography in predicting functional recovery after revascularization is comparable to that of both thallium and sestamibi scintigraphy in patients with myocardial infarction and chronic LV dysfunction.     

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.     

Comparison of Tc-99m sestamibi and Tl-201 gated perfusion SPECT

BACKGROUND: To determine the interpretability of gated thallium-201 perfusion SPECT compared with that performed by use of technetium-99m sestamibi (MIBI), 33 patients with prior myocardial infarction were studied. Patients received 22 to 30 mCi (814 to 1110 MBq) MIBI at peak stress, and a 15-minute gated SPECT acquisition was begun 30 to 40 minutes thereafter. On a subsequent day gated Tl-201 SPECT was acquired for 15 minutes, 4 hours after a resting 3.5 mCi (130 MBq) injection. SPECT was performed over a 180-degree arc by use of a 90-degree angled 2-detector camera. RESULTS: Gated studies were interpreted independently by 4 experienced physicians. Study quality was graded (0 = uninterpretable to 4 = excellent). Wall motion (0 = normal to 2 = akinetic/dyskinetic) and wall thickening (0 = normal to 2 = absent) were graded for each of 10 segments viewed in orthogonal planes. Left ventricular ejection fraction (LVEF) was calculated by use of software thus far validated only for MIBI. The average count density of mid-ventricular end-diastolic short axis tomograms with sestamibi was 3.47 times greater than with thallium. Mean study quality was 3.4 for MIBI and 1.8 for thallium (P < 10(-6)). No gated MIBI SPECTs, but 2 gated thallium studies (6%) were judged uninterpretable. Among interpretable scans, interobserver agreement (Kendall statistic) in assessing wall motion was 0.73 for MIBI and 0.66 for thallium (P = .01). For assessing wall thickening, the Kendall statistic was 0.73 for MIBI and 0.69 for thallium (P = .05). Correlation (r) of LVEFs was 0.91, SEE = 6.4. CONCLUSIONS: We conclude that gated thallium SPECT is inferior to MIBI because of much poorer image quality and somewhat poorer interobserver agreement among experienced physicians. However, LVEF can be determined reliably from gated thallium SPECT.