Transaxial tomography with thallium-201 for detecting remote myocardial infarction: Comparison with planar imaging

Transaxial tomograhic imaging with thallium-201 was compared with standard, planar imaging in 38 patients with remote myocardial infarction and in 15 normal patients. Tomographic images were reconstructed from 64 views collected by a gamma camera that rotated about the anterior circumference of the patient's chest. A series of consecutive transverse-section images which encompassed the cardiac volume were reconstructed at a 6 mm plane spacing by filtered back-projection. No correction was made for attenuation losses. The set of transverse-section images was reformatted by 3-dimensional interpolation to obtain tomograms along the long and short axes of the myocardium. Tomographic and planar images were interpreted qualitatively.

Overall, tomography detected 33 of 38 (87%) prior infarctions whereas planar imaging detected 24 of 38 (63 %) (p = 0.01). Improvement of the tomographic imaging method occurred only in the combined subset of transmural inferior and subendocardial infarctions, and not in transmural anterior infarctions. Peak increases in creatinine phosphokinase were smaller in patients detected only by tomography compared with those detected by both the planar and the tomographic approach (3.1 × normal versus 10.4 × normal, p = 0.04). Five patients (13%) with prior infarction were not detected by either approach. For 6 of the 9 patients detected by tomography alone, realignment of the image data along the short and long axes of the heart was essential for making the diagnosis. Fourteen of 15 patients without infarction were normal on both planar and tomographic imaging. A single normal patient had a defect detected by both techniques, yielding a specificity of 93% for each.

We conclude that transaxial tomography significantly improves the detection of thallium-201 myocardial perfusion defects in patients with prior myocardial infarction.     

Evaluation of cardiac function in myocardial infarction patients by ECG 99mTc-MIBI gated SPECT using a three-dimensional perfusion/motion map procedure

Three-dimensional (3D) radionuclear myocardial imaging has improved the evaluation of left ventricular wall motion. However, there have been no studies evaluating left ventricular function using 3D-perfusion/motion map techniques. We hypothesized that the 3D-perfusion/motion map could accurately evaluate left ventricular wall motion even in patients with a history of myocardial infarction. Electrocardiogram (ECG)-gated single photon emission computed tomography (SPECT) using 99mTc-methoxy isobutyl isonitrile (MIBI) was performed in 20 patients with a history of myocardial infarction who underwent left ventriculography. Myocardial imaging data were collected during ECG-gated SPECT using a 3-headed gamma camera. Reconstructed 3D SPECT images were oriented to correspond to standard left ventriculography views (right anterior oblique and left anterior oblique projections), and the shortening fraction (SF) was calculated using the center line method. The SF and left ventricular ejection fraction from 3D SPECT images were compared with those determined by left ventriculography. There was a significant correlation between left ventriculography and the 3D-perfusion/motion map procedure in determining SF for all regions of the left ventricle except the anterobasal and posterior segments by using the Bland and Altman method. The 3D-perfusion/motion map procedure offers the advantage that the influences of contraction-related myocardial torsion and three-dimensional compression are minimized. In addition, this method facilitates evaluation of images from nonstandard projections. We conclude that this method may be useful for evaluating left ventricular function.     

99mTc-pyrophosphate imaging in patients with acute myocardial infarction: comparison of planar imaging with single-photon tomography with and without blood pool overlay

To test the hypothesis that single-photon emission computed tomography (SPECT) of 99mTc-pyrophosphate (99mTc-PPi) with and without the overlay of tomographic blood pool scintigrams might detect small infarcts not identified by planar imaging, 52 patients were studied 3.2 +/- 2.0(SD) days after hospital admission for suspected acute myocardial infarction. Patients were chosen prospectively for tomographic study primarily, but not exclusively, because planar four-view imaging with 99mTc-PPi was either negative or equivocal. SPECT was performed with a commercial rotating detector system immediately after planar imaging on one occasion. Corresponding 99mTc-PPi and blood pool sections were mapped into opposite halves of a bichromic color table and displayed as an overlay. Planar images, SPECT and SPECT with blood pool overlay were interpreted separately and in random order without knowledge of clinical data. Seventeen patients had transmural infarcts (four anterior, 13 inferior), 19 had nontransmural infarcts, and 16 patients did not have acute myocardial infarction. The sensitivity of SPECT with blood pool overlay was significantly better than planar imaging for the entire group with myocardial infarction (97% vs 78%; p less than .025); this was primarily due to increased sensitivity in the detection of nontransmural myocardial infarction (95% vs 67%; p less than .05), although in one additional patient inferior transmural myocardial infarction was also detected by the SPECT overlay technique. The specificities of the SPECT overlay technique and planar imaging were not significantly different; however, receiver operating characteristic analysis showed enhanced observer confidence with the tomographic method. SPECT without overlay was intermediate in sensitivity and specificity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Improved detection of acute myocardial infarct with combined simultaneous thallium-201/technetium-99m-PPi tomography in comparison with planar infarct scintigraphy

The combined TI-201/Tc-99mPPi tomography was compared to planar Tc-99m-PPi scintigraphy in terms of diagnosis and localization of the infarction. In 32 consecutive patients with recent myocardial infarctions, the necrosis could be detected by means of planar imaging in 17 out of 22 patients with transmural and in three out of 10 patients with intramural infarctions. Six out of seven patients without recent myocardial infarctions were accurately diagnosed. Double radionuclide tomography made possible accurate diagnoses in all patients. Artefacts resulting from residual radioactivity within the cardiac blood pool and uptake of tracer in bones that overlie the heart were only observed with planar imaging. Conclusion: double radionuclide tomography is superior to planar imaging in the diagnosis of acute myocardial infarction.     

Diagnostic value of contrast-enhanced magnetic resonance imaging and single-photon emission computed tomography for detection of myocardial necrosis early after acute myocardial infarction.

OBJECTIVES: This study sought to evaluate the diagnostic value of contrast-enhanced magnetic resonance imaging (CMR) and single-photon emission computed tomography (SPECT) for detection of myocardial necrosis after acute myocardial infarction (AMI). BACKGROUND: Single-photon emission computed tomography is widely accepted in the clinical setting for detection and estimation of myocardial infarction. Contrast-enhanced magnetic resonance imaging offers technical advantages and is therefore a promising new method for identification of infarcted tissue. METHODS: Seventy-eight patients with AMI were examined by CMR and SPECT 7 days after percutaneous coronary intervention. Contrast-enhanced magnetic resonance imaging and SPECT images were scored for presence and location of infarction using a 17-segment model. Results were compared with the peak troponin T level, electrocardiographic, and angiographic findings. RESULTS: Acute myocardial infarction was detected significantly more often by CMR than SPECT (overall sensitivity: 97% vs. 87%; p = 0.008). Sensitivity of CMR was superior to SPECT in detecting small infarction as assessed by the peak troponin T level <3.0 ng/ml (92 vs. 69%; p = 0.03), and infarction in non-anterior location (98% vs. 84%; p = 0.03). Non-Q-wave infarctions were more likely to be detected by CMR (sensitivity 85% vs. 46%; p = 0.06). While CMR offered high sensitivity for detection of AMI irrespective of the infarct-related artery, SPECT was less sensitive, particularly within the left circumflex artery territory. CONCLUSIONS: Contrast-enhanced magnetic resonance imaging is superior to SPECT in detecting myocardial necrosis after reperfused AMI because CMR detects small infarcts that were missed by SPECT independent of the infarct location. Thus, CMR is attractive for accurate detection and assessment of the myocardial infarct region in patients early after AMI.     

Outcome of patients with adenosine-induced ST-segment depression but with normal perfusion on tomographic imaging

Most patients with ST depression during adenosine infusion have reversible perfusion defects by single-photon emission computed tomographic (SPECT) perfusion images. Occasionally ST depression is observed in the setting of normal perfusion images. The outcome of such patients is controversial. We identified 65 patients who underwent gated SPECT perfusion imaging with adenosine as the stress agent. These patients were selected based on the following criteria: none had previous myocardial infarction or coronary revascularization, all were in sinus rhythm, and none had left bundle branch block. The 65 patients had normal SPECT images but ischemic ST response (>or=1 mm ST depression). There were 52 women and 13 men who were 66 +/- 13 years of age. History of diabetes mellitus was present in 16 patients (25%) and hypertension in 48 patients (74%). At a mean follow-up of 24 months, there were no cardiac deaths or myocardial infarctions, and there were 6 coronary revascularization procedures (2 coronary artery bypass graftings and 4 coronary stentings of 1-vessel coronary disease). One patient died of cancer. In conclusion, patients with no previous myocardial infarction or coronary revascularization who have normal SPECT images have a benign outcome despite the presence of ST depression (0% for death or myocardial infarction and 4.6%/year for coronary revascularization). Balanced ischemia could not be a common cause for discordant perfusion and ST response.     

Clinical significance of the right ventricular free wall appearance on stress Tl-201 myocardial images in ischemic heart disease

In order to evaluate the clinical significance of thallium (Tl)-201 myocardial imaging for diagnosing the right ventricular (RV) ischemia, we studied the relationship of right ventricular free wall (RVFW) appearance on myocardial images to coronary arteriographic findings. Patients were divided into 3 groups as follows: 1) normal control (NC) group (19 cases) without angiographically documented coronary artery disease; 2) non-RCA group (18 cases) with significant coronary artery lesion restricted to the left coronary artery (LCA); and 3) RCA group (36 cases) with significant right coronary artery (RCA) stenosis regardless of underlying LCA disease. After the patients had exercised up to 80-85% of the predicted maximal heart rate, immediate and 3-4 hour delayed myocardial images were obtained. As for presence or absence of the RV ischemia on images, the RVFW appearance in 30 degrees and 60 degrees left anterior oblique (LAO) views were assessed carefully. On the immediate images, all patients except one in the NC group and all except 3 in the non-RCA group demonstrated 'continuous visualization' of the RVFW in both views. In the RCA group, 6 showed 'non-visualization' and 11 'defective visualization' of the RVFW in 30 degrees LAO view. In 60 degrees LAO view, 6 presented 'non-visualization' and other 6 'defective visualization' of the RVFW. On the delayed images, although none of the patients in the groups NC and non-RCA demonstrated redistribution phenomenon of the RVFW, 4 patients in the RCA group showed redistribution of Tl-201 into the RVFW. Non- and defective visualization of the RVFW on the immediate images were related to the proximally located RCA lesion, previous history of inferior myocardial infarction and high grade RCA stenosis. Collateral vessels seemed to protect the RVFW against the development of exercise induced ischemia and affect the occurrence of redistribution of Tl-201 into the RVFW. In conclusion, stress Tl-201 myocardial imaging enables us to estimate the myocardial blood flow of the RV and is a useful non-invasive method in the evaluation of RV ischemia.     

Myocardial scintigraphy with 99mTc MIBI. The use of a single-day protocol in a multiregional center: a comparison between planar and tomographic imaging]

The use of a single-day protocol for 99mTc MIBI myocardial scintigraphy is particularly well-suited for the nuclear medicine departments that are the referral centres for the cardiology departments of several community hospitals. The aim of the study was to compare, in the same patient population, the diagnostic accuracy of planar and SPECT imaging with 99mTc MIBI using a single-day protocol. Thirty-nine patients (31 males and 8 females, age range 32-69 years) were studied because of effort chest pain. Of them, 7 had a pre-test probability of coronary artery disease less than 2.5%; coronary angiography demonstrated significant coronary obstructions in the remaining 32 subjects and 21 of them also had a history of previous myocardial infarction. All patients underwent 99mTc MIBI myocardial scintigraphy with acquisition of planar and SPECT images after injection of a low dose (370 MBq) at rest and after a second higher dose (1110 MBq), injected approximately four hours later during exercise stress testing. The normalcy rate in the 7 patients with low pre-test probability was 100% using both imaging techniques. For the diagnosis of previous infarction, the sensitivities of planar and SPECT images were 71% and 96% respectively. For the diagnosis of effort ischemia the sensitivity values were 34% and 88%, respectively, using planar and SPECT imaging. With regard to the classification of the diseased coronary arteries, the sensitivities of planar and SPECT studies were 42% and 79% respectively, and the related specificities were 91% and 77%. We may conclude that using a single-day protocol planar imaging seems to allow lower levels of diagnostic accuracy both for the diagnosis of effort ischemia and the classification of the diseased vessels as compared to SPECT, which appears therefore in a similar setting the imaging technique of choice.     

Detection, quantification and localization of myocardial infarcts: comparison of thallium single photon emission computer tomography with biplane angiography

Thallium-201 single photon emission computed tomography (SPECT) is a new method for the scintigraphic visualization of the left ventricular myocardium. With SPECT a three-dimensional imaging by computerized slicing of the myocardium in various axes is possible. To investigate the capabilities of this new imaging technique, detection and quantification of remote transmural infarctions were compared with ventriculographic, coronarographic and electrocardiographic findings. 31 of 80 investigated patients had had a prior myocardial infarction. The left ventricular myocardium was divided into 7 regions in the scintigraphic as well as in the angiographic studies. In a total of 560 segments the sensitivity of SPECT for infarct detection was 87.5% with a specificity of 99.8%. Infarcts which were not detected scintigraphically were relatively small (mean 13.5% of the circumference). To quantify the infarct, the size of the defect was determined scintigraphically from a sagittal long axis and two short axes, and the images compared with angiographic infarct sizes (% of the circumference) according to the method of Feild et al. A good correlation without overestimation of the size by one method (SPECT defect = 0.93 X ventriculographic defect - 1.2%; r = 0.7, p less than 0.001) was obtained. Also a good separation of the perfusion areas of the coronary arteries due to the three-dimensional imaging with SPECT was possible. Thus, by employing Thallium-201 SPECT of the left ventricular myocardium exact localization and quantification of transmural myocardial infarcts with a positive predictive value of 98% can be achieved.     

Clinical validation of technetium-99m MIBI-gated single-photon emission computed tomography (SPECT) for avoiding false positive results in patients with left bundle-branch block: comparison with stress-rest nongated SPECT

BACKGROUND: Septal perfusion defects are common on myocardial perfusion single-photon emission computed tomography (SPECT) slices in patients with left bundle-branch block (LBBB) in the absence of coronary artery disease. HYPOTHESIS: The use of gated myocardial perfusion SPECT imaging in such patients should be clinically validated. The aims of this study were, therefore, to validate clinically the use of gated myocardial SPECT imaging to avoid false positive septal perfusion defects in patients with LBBB and to compare nongated and gated SPECT imaging techniques in the same patients in the same imaging session. METHODS: We performed stress-rest myocardial perfusion SPECT and resting gated SPECT using Technetium-99m MIBI in 25 patients with LBBB and in 6 control subjects. Stress-rest SPECT images and end-diastolic and end-systolic gated SPECT slices were assessed visually and quantitatively (septum/lateral wall count ratio). Coronary angiography was performed in 15 patients with LBBB and in all 6 control subjects. RESULTS: Stress-rest (nongated) SPECT slices and end-diastolic and end-systolic gated SPECT images were normal in all control subjects. Stress-rest (nongated) SPECT imaging revealed septal perfusion defect in 20 (11 reversible, 9 irreversible) patients with LBBB, whereas the figures were 15 and 5 for end-systolic and end-diastolic gated SPECT images, respectively. Coronary angiography results were normal in all control subjects and in 15 patients with LBBB. Quantitative analysis of gated SPECT images revealed no statistically significant difference between patients with LBBB and control subjects in end-diastolic mean septum/lateral wall count values (0.86 +/- 0.19 in LBBB vs. 0.98 +/- 0.15 in normal subjects, p > 0.05), but the difference was statistically significant for end-systolic, stress, and rest values (p < 0.001 for all). CONCLUSION: Gated SPECT imaging, particularly end-diastolic images, revealed fewer false positive results and thus can be used to avoid false positive septal perfusion defects commonly seen in stress-rest (nongated) myocardial perfusion SPECT in patients with LBBB.     

Technetium 99m-diphosphate as an imaging agent in acute myocardial infarction (author's transl)

To test the sensitivity and specificity of 99m-Technetium-Diphosphat myocardial scintigraphy in the diagnosis of acute myocardial infarction we examined the scintigrams of 53 patients admitted to our CCU. In all 38 patients with transmural myocardial infarction positive scintigrams with localized uptake of the tracer found. Myocardial imaging was performed 70--90 minutes after the intravenous injection of 15 mCi 99m-Technetium-Diphosphat in anterior and LAO position. The clinical value of the method for proving the presence or absence of a myocardial infarction is demonstrated on infarctions combined with bundle-branch block, pacemaker Ecg and on reinfarction. All normal cases in this group showed no tracer activity outside the bones. In unstable angina pectoris a faint but not localized tracer activity was found.     

Left ventricular wall motion abnormalities as well as reduced wall thickness can cause false positive results of routine SPECT perfusion imaging for detection of myocardial infarction.

AIMS: The relationship between wall thickness, wall thickening, wall motion, and single-photon emission computed tomography (SPECT) results for detection of myocardial infarction has never been systematically evaluated in a clinical setting. In particular, the discussion whether non-ischaemic regional wall motion abnormalities and reduced wall thickness can cause SPECT to be false positive for infarct detection remains unsettled. METHODS AND RESULTS: We therefore evaluated patients presenting with left bundle branch block (LBBB) and only included them in the analysis if any coronary artery disease (CAD) had been ruled out by angiography. LBBB is known to cause septal wall motion abnormalities as well as to reduce systolic septal wall thickness. Thus, LBBB is a good non-ischaemic clinical model to evaluate the influence of wall thickness and wall motion on the homogeneity of tracer distribution in resting SPECT images. SPECT revealed fixed defects in all 139 patients initially identified for possible enrollment. CAD was found to be present by angiography in 120 patients. The remaining 19 patients without any CAD underwent cardiovascular magnetic resonance (CMR) and were included in the study. Evaluation of SPECT using a 72-segment model revealed septum-related fixed defects in all 19 patients. Every defect was interpreted as myocardial infarction by blinded observers. The comparison of nuclear results to the gold standard CMR demonstrated that none of the fixed SPECT defects did represent myocardial infarcts. Defects, however, exactly matched areas of wall motion abnormalities as well as regions with impaired wall thickness as demonstrated by CMR. On a segmental basis, we found a strong relationship between wall motion and reduced wall thickness on one hand and SPECT defects on the other hand. For example, only 5% of segments with normal wall motion were false positive by SPECT for myocardial infarction, whereas 93% of all dyskinetic segments were found to be false positive (P<0.01). Comparing wall thickness to SPECT results revealed that 58% of segment in which wall thickness was 1 SD below the mean and 93% of segments in which wall thickness was 2 SD below the mean showed fixed defects by SPECT. Conversely, only 0.5% of segments in which wall thickness was above the mean were affected by false positive SPECT results (P<0.01). CONCLUSION: Wall motion abnormalities as well as impaired myocardial wall thickening and wall thickness can cause false positive results of resting SPECT myocardial perfusion imaging for detection of myocardial infarction in the absence of myocardial infarct scars and CAD.     

Technetium stannous pyrophosphate myocardial scintigrams in patients with chest pain of varying etiology.

Technetium-99m stannous pyrophosphate was utilized for myocardial imaging in 202 patients admitted to the hospital with chest pain of uncertain etiology. One hundred and one patients had clinical and evolved electrocardiographic and enzymatic evidence of acute myocardial infarction. Ninety-six of these 101 patients had increased myocardial uptake of the technetium stannous pyrophosphate and positive myocardial scintigrams; there was nearly precise correlation between the ECG and myocardial imaging localization of the area of infarction for acute transmural myocardial infarctions. In the five patients with negative myocardial images the scintigrams were obtained after seven or more days had elapsed following the myocardial infarction. In the remaining 101 patients no clinical, ECG, or enzymatic evidence of infarction developed; 92 of these patients had negative myocardial scintigrams. Seven of the remaining nine patients were admitted with "unstable angina pectoris", and despite the absence of diagnostic ECG and enzyme evolution each of these patients had faintly and diffusely positive myocardial scintigrams. The remaining two patients had positive myocardial scintigrams but no definite ECG or enzymatic evidence of acute myocardial infarction. Thus the technetium pyrophosphate imaging technique appears safe, inexpensive and to correlate well with ECG and enzyme identification of the presence of infarction and with ECG localization of myocardial infarction. In addition the positive myocardial scintigrams in some patients with "unstable angina" suggest that there may be limited myocardial necrosis that is ordinarily undetected by ECG and enzymes in these patients. The incidence of false positive and false negative scintigrams appears to be small.     

Positron emission tomography--usefulness in assessing myocardial viability.

Positron emission tomography (PET) using N-13 ammonia and F-18 fluorodeoxyglucose (FDG) has been used to evaluate myocardial viability in comparison with thallium-201 single photon emission computed tomography (SPECT), and left ventricular wall motion in comparison with contrast ventriculography. Forty patients with anterior myocardial infarction underwent stress and delayed resting perfusion imaging using Tl-201 SPECT and ammonia PET, a glucose metabolism study using FDG PET, and wall motion assessment with left ventriculography. Out of a total of 600 segments of left ventricular imaging, SPECT demonstrated 197 fixed perfusion defects, 99 with redistribution on delayed imaging and 304 normal segments. Of 197 segments with fixed defects, 24 (12%) were normal and 71 (36%) ischemic according to PET criteria. Nineteen of 28 with infarction and all of 12 with non-Q wave infarction showed a viable myocardium. Left ventricular wall motion was significantly better in patients with normal PET findings compared with those with ischemia or scar on PET. Post-PTCA PET revealed improved ammonia PET in 6 of 11 patients but reduced FDG uptake was noted only in 3. These data suggests that Tl-201 SPECT significantly underestimates myocardial viability and that PET imaging is a promising tool for assessing the presence of salvaged myocardium.     

Renal artery angiography: "the right ipsilateral oblique" myth.

BACKGROUND: Finding the optimal image intensifier angle of obliquity during renal intervention is important for accurate stent placement but can require multiple catheter rotations and test injections of contrast. OBJECTIVE: Explore the usefulness of axial magnetic resonance angiography (MRA) as a roadmap for predicting image intensifier position during subsequent renal intervention. METHODS: MRA images were reviewed in 137 consecutive patients (255 renal arteries) undergoing workup for renal artery stenosis. The axial angle of renal artery incidence perpendicular to the spine was estimated by two operators and results averaged. RESULTS: The average angle of incidence for the renal artery ostia was +21.24 degrees +/-2.31 degrees for the right and +8.81 degrees +/-2.0 degrees for the left (P < .0001). The positive numbers correlate with left anterior oblique (LAO) and negative right anterior oblique (RAO). CONCLUSIONS: MRA can be used to define the origin of the renal artery and is most likely to predict an LAO image window for subsequent angiography of the left and right renal arteries displacing the "ipsilateral oblique" axiom. In patients without baseline MRA the 10 to 20 degree LAO "empiric" position will allow coaxial imaging of both renal ostia in 75% of cases. However, there can be extreme variation in the renal origin (53 degrees RAO to 85 degrees LAO) and we advocate using the simple technique reported herein to define the renal origin in patients with pre-procedure MRA.     

Improved detection of myocardial infarction by emission computed tomography with thallium-201. Relation to infarct size.

Emission computed tomography with thallium-201 was compared with planar imaging in its ability to detect myocardial infarctions of various sizes four weeks after the onset. Tomography was performed after planar imaging at rest in 160 patients with a first myocardial infarction, in whom infarct size was prospectively estimated by the peak value of creatine kinase activity at the time of the acute episode and in 39 patients without infarction. The planar images and the transaxial, short axial, and long axial tomograms were interpreted qualitatively. Tomography was significantly more sensitive than planar imaging in detecting anterior (87% v 96%), inferior (73% v 97%), and non-transmural (47% v 87%) infarcts. The increased sensitivity was confined to detecting small infarcts as assessed by the peak creatine kinase value (44% v 89% when peak creatine kinase activity was less than or equal to 1000 IU/l). The overall sensitivity was 96% for tomography and 78% for planar imaging. The specificity was similar (92%) with the two techniques. Thus emission computed tomography can improve the detection rate of small infarcts that cannot be identified on planar images, by showing the three dimensional distribution of thallium-201, and increases the diagnostic value of thallium-201 scintigraphy.     

Study of myocardial perfusion at rest using technetium Tc 99m methoxy-isobutylisonitrile: comparison with labeled microspheres and thallium 201

In order to evaluate the potential usefulness of 99m technetium (Tc)-methoxy-isobutyl-isonitrile (MIBI) as a myocardial perfusion tracer in man, its myocardial distribution at rest was compared with that of 201thallium (TI). Perfusion images obtained with 99mTc-labelled microspheres, whose myocardial distribution is exclusively coronary flow dependent, were used as reference. The study was performed on twelve patients (10 males and 2 females, mean age 55.4 +/- 6.4) with suspected effort angina and without a history of previous myocardial infarction. In the space of two weeks patients underwent rest and exercise 99mTc-MIBI myocardial scintigraphy, exercise-redistribution 201TI myocardial scintigraphy, 99mTc-labelled microsphere scintigraphy after microsphere injection in the left ventricle at rest during catheterization before performing left ventriculography and coronary angiography. The comparison with microsphere distribution was limited to rest 99mTc-MIBI scintigraphy and redistribution 201TI images. Single photon emission tomography (SPECT) was employed. SPECT was performed using a double-head Rotacamera with a 360 degrees rotation arc. Ninety projections of 20 seconds each were acquired; subsequently image reconstruction was performed using an iterative algorithm. To evaluate regional perfusion the left ventricular wall was divided into 18 segments; the uptake pattern of each segment was graduated according to a qualitative score (0: severe defect; 1: moderate defect; 2: normal uptake). The quality of tomographic myocardial 99mTc-MIBI and 99mTc-microspheres images was higher than that of 201TI tomograms in account of the different physical characteristics of the two radionuclides.(ABSTRACT TRUNCATED AT 250 WORDS)     

Exercise four hour redistribution thallium-201 single photon emission computed tomography and exercise induced ST segment elevation in detecting the viable myocardium in patients with acute myocardial infarction

OBJECTIVE: To investigate the specificity and sensitivity of the combination of redistribution in exercise thallium-201 single photon emission computed tomography (SPECT) and exercise induced ST elevation for detecting the viable myocardium in patients with acute myocardial infarction. DESIGN: 37 patients were studied within seven weeks of onset of Q wave myocardial infarction (anterior in 22, inferior in 15). All patients underwent exercise four hour redistribution thallium-201 SPECT and positron emission tomography using fluorine-18-fluorodeoxyglucose (FDG) and nitrogen-13 ammonia under fasting conditions. RESULTS: Sixteen patients showed exercise induced ST elevation >/= 1.5 mm, and 15 of these had increased FDG uptake in the infarct region. Eleven of 16 patients (10 of 11 patients with anterior infarctions) with irreversible thallium-201 defects and increased FDG uptake showed exercise induced ST elevation. The sensitivity, specificity, and predictive accuracy of redistribution, exercise induced ST segment elevation, or both for detecting increased FDG uptake were 82%, 75%, and 67% (94%, 75%, and 91% for anterior infarctions), respectively. CONCLUSIONS: In patients with acute Q wave myocardial infarction, the combination of redistribution in exercise thallium-201 SPECT and exercise induced ST elevation can detect the viable myocardium in the infarct region with high sensitivity and specificity, especially in patients with anterior infarctions.     

Left ventricular asynergy in electrocardiographic "posterior" myocardial infarction

P2 300 selected patients, scalar electrocardiograms and contemporaneous radionuclide angiograms were analyzed retrospectively to assess the association between prominent right precordial R waves (duration greater than or equal to 0.04 second, R greater than or equal to S in lead V1 or V2), traditionally considered diagnostic of "posterior" infarction, and asynergy in various left ventricular segments. Mathematical methods for analysis of association between nonparametric variables clearly demonstrated that prominent right precordial R waves were strongly associated with asynergy of the basal lateral left ventricular wall, although asynergy of adjacent inferior and lateral segments was common. With the exclusion of right ventricular hypertrophy and bundle branch block, a prominent R wave in lead V1 exhibited a high specificity (greater than to 99%), a high positive predictive value (91%) and a low sensitivity (36%) for diagnosing basal lateral myocardial infarction. A prominent R wave in lead V2 exhibited a higher sensitivity (61%), a somewhat lower specificity (95%) and a significantly lower positive predictive value (76%). A newly developed criterion for such infarction--a prominent R wave in lead V2 and a Q wave inferior infarction--had intermediate characteristics and may be more clinically useful. The most common reasons for the decreased sensitivities of all three criteria were left ventricular hypertrophy or associated anterior myocardial infarction. These data demonstrate that prominent right precordial R waves are clinically useful in identifying inferior and lateral wall infarctions that involve the basal lateral left ventricular segment. Confusion results primarily from inappropriate use of the electrocardiographic term "posterior" for such infarctions.     

Quantification of myocardial infarction: a comparison of single photon-emission computed tomography with pyrophosphate to serial plasma MB-creatine kinase measurements

Single photon-emission computed tomography (SPECT) with 99mTc-pyrophosphate (PPi) has been shown to estimate size of myocardial infarction accurately in animals. We tested the hypothesis that SPECT with 99mTc-PPi and blood pool subtraction can provide prompt and accurate estimates of size of myocardial infarction in patients. SPECT estimates are potentially available early after the onset of infarction and should correlate with estimates of infarct size calculated from serial measurements of plasma MB-creatine kinase (CK) activity. Thirty-three patients with acute myocardial infarction and 16 control patients without acute myocardial infarction were studied. Eleven of the patients had transmural anterior myocardial infarction, 16 had transmural inferior myocardial infarction, and six had nontransmural myocardial infarction. SPECT was performed with a commercially available rotating gamma camera. Identical projection images of the distribution of 99mTc-PPi and the ungated cardiac blood pool were acquired sequentially over 180 degrees. Reconstructed sections were color coded and superimposed for purposes of localization of infarct. Areas of increased PPi uptake within myocardial infarcts were thresholded at 65% of peak activity. The blood pool was thresholded at 50% and subtracted to determine the endocardial border for the left ventricle. Myocardial infarcts ranged in size from 1 to 126 gram equivalents (geq) MB-CK. The correlation of MB-CK estimates of size of infarct with size determined by SPECT (both in geq) was good (r = .89 with a regression line of y = 13.1 + 1.5x).(ABSTRACT TRUNCATED AT 250 WORDS)