Diagnostic value of maximum intensity projections versus source images for assessment of contrast-enhanced three-dimensional breath-hold magnetic resonance coronary angiography

RATIONALE AND OBJECTIVES: We compared maximum intensity projections (MIP) versus original source images (SI) in respect to detection of coronary artery stenoses by means of magnetic resonance (MR) coronary angiography. METHODS: MR coronary angiography was performed on 61 patients. MIP and SI were independently evaluated as to presence of significant stenoses in the proximal and midcoronary segments and compared with x-ray angiography. RESULTS: A total of 315 of 427 (74%) coronary artery segments could be evaluated in MIP and 328 of 427 (77%) in SI. In segments able to be evaluated, MIP images demonstrated 84% (54/64) sensitivity and 87% (219/251) specificity, whereas SI images showed 85% (58/68) sensitivity and 90% (235/260) specificity. Overall accuracy was 87% (273/310) for MIP and 89% (293/328) for SI. There was no statistically significant difference between both modalities. CONCLUSIONS: The MIP reconstructions showed comparable accuracy to unprocessed SI. However, MIP postprocessing is compromised by a higher number of images that were unable to be evaluated due to overlap of coronary arteries with adjacent cardiac structures.     

MR imaging at rest early after myocardial infarction: detection of preserved function in regions with evidence for ischemic injury and non-transmural myocardial infarction

Patients with subacute myocardial infarction were studied to detect regions of ischemic injury but with preserved myocardial function combining different MRI techniques. On a 1.5-T imaging system 27 patients were examined 7–14 days after acute myocardial infarction. The imaging protocol included T2-weighted fast spin-echo imaging, a cine fast low-angle shot (FLASH) 2D technique to determine regional function at rest, and a first pass as well as late contrast enhancement perfusion study injecting 0.1 mmol/kg Gd-DTPA. Preserved function was compared with the transmural extent of first-pass perfusion phenomena, increased T2 signal intensity (SI), and late contrast enhancement. Semi-quantitative first-pass perfusion parameters were correlated with quantitative myocardial wall thickening (MWT) and degree of coronary artery stenosis. Indicating ischemic injury increased T2 SI and late enhancement was present in 29 and 26% of segments. Preserved function was found predominantly in segments with non-transmural late enhancement (112 of 338 segments with late enhancement) and transmural increase of T2 SI (129 of 386 segments with increased T2 SI). A high-grade perfusion deficit was detected in 4% of all segments and regularly associated with markedly decreased systolic function. Correlation of first-pass perfusion parameters was observed with MWT (r=0.50–0.90, p<0.001) but not with the degree of coronary artery stenosis. Our data suggest that preserved function was detected in non-transmural myocardial infarction demonstrated by non-transmural late enhancement and increase of T2 SI. Electronic Publication     

"False-positive" myocardial perfusion scintigraphy findings in patients with angiographically normal coronary arteries: insights from intravascular sonography studies.

Abnormal exercise perfusion findings have been described as false-positive for coronary artery disease in patients with suspected angina and angiographically normal coronary arteries. METHODS: The significance of this finding was further investigated by obtaining intravascular sonograms and Doppler guidewire measurements of at least 2 coronary arteries in 20 consecutive patients who had chest pain, normal coronary angiography findings, and positive stress-rest sestamibi SPECT findings. The summed reversible score was used to describe the extent and severity of reversible perfusion defects. On the basis of scintigraphy findings, vessels were grouped as supplying underperfused myocardial segments (target vessels, n = 20) or normal territories (reference vessels, n = 25). The presence and extension of atherosclerotic disease of the epicardial arteries were assessed by intracoronary sonography. Measurements of plaque area (PA), vessel area (VA), and relative cross-sectional PA (RPA) (RPA = PA/VA) were obtained at the site of maximum plaque concentration. The coronary flow velocity reserve (CFR) was assessed during adenosine-induced hyperemia, and the relative flow reserve was calculated as the target-to-reference coronary reserve ratio. RESULTS: The median summed reversible score was 3 (range, 1-6). Intracoronary sonography showed occult atherosclerosis in 19 patients (95%), with RPA greater than 40% in 16 patients (80%). Mean RPA was significantly greater in the target vessels (46% +/- 14%) than in reference vessels (12% +/- 18%; P < 0.0001). Doppler flow velocity measurements showed abnormal vasodilation capacity (CFR < 2.5) in 14 patients (70%). Mean CFR was significantly lower in the target vessels than in the reference vessels (2.3 +/- 0.5 versus 3.1 +/- 0.6; P < 0.0001). A significant inverse correlation was seen between the summed reversible score and the coronary reserve ratio (y = 9.05x - 9.9; r = 0.70; P < 0.005). CONCLUSION: Reversible perfusion defects seen on SPECT images are often associated with angiographically unrecognized occult atherosclerotic changes and an abnormal vasodilation capacity of the coronary circulation. The tendency to dismiss abnormal exercise perfusion findings as false-positive in these patients may be unjustified.     

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.     

Tc-99m sestamibi gated SPECT in patients with left bundle branch block

PURPOSE: The purpose of this study was to assess the diagnostic role of a Tc-99m sestamibi gated SPECT technique in patients with left bundle branch block (LBBB) without known coronary artery disease. MATERIALS AND METHODS: Twenty consecutive patients with constant complete LBBB were included. A same-day rest-stress protocol was used, and dipyridamole stress (14 patients) or treadmill exercise (6 patients) was applied. Electrocardiograph (ECG)-gated SPECT images were acquired 15 minutes after the administration of 0.31 mCi/kg Tc-99m sestamibi at peak stress. Regional myocardial perfusion was analyzed in relation to the cardiac cycle. RESULTS: Eleven of 14 patients who underwent a dipyridamole stress test had hypoactivity in the left anterior descending (LAD) artery territory in the ungated (summed) stress-rest images (abnormality ratio, 78%). On the ungated images, the abnormality was completely reversible in one patient (9%), partially reversible in five patients (46%), irreversible in two patients (18%), and reverse perfusion was identified in three patients (27%). Abnormality ratios of end-systolic and end-diastolic data were 93% and 29%, respectively. Conversely, the ungated rest-stress and end-systolic images of all the patients who performed treadmill exercise were abnormal despite the presence of normal or nearly normal end-diastolic myocardial perfusion. The angiographic findings correlated best with those of end-diastolic images. In 13 patients without coronary artery disease, normal or nearly normal regional perfusion was observed on end-diastole, but four patients with abnormal end-diastolic perfusion, which involved the LAD territory in all but one, had substantial coronary artery disease. The number of the involved segments was similar on the end-systolic and ungated data. Most of these artifactual defects were localized to the anteroseptal, septal, and inferoseptal segments. CONCLUSIONS: These preliminary data indicate that end-diastolic images can significantly reduce artifactual defects in patients with LBBB. The resolution of an LBBB pattern on end-diastolic data would significantly improve the diagnostic role of myocardial perfusion studies in these patients.     

Cardiac MRI in ischemic heart disease with severe coronary artery stenosis

RATIONALE AND OBJECTIVES: The aim was to evaluate the left ventricular wall motion abnormalities, perfusion and late contrast enhancement patterns on magnetic resonance imaging (MRI) in patients with 70% or higher degree stenosis or occlusion of coronary arteries on coronary angiography. MATERIALS AND METHODS: Twenty-four patients (5 women, 19 men, age range 38-78, mean age 59.1) who had 70% or higher degree stenosis or occlusion of coronary arteries on coronary angiography who had been referred for cardiac MRI were included. On coronary angiography, 20 vessels were totally occluded [left anterior descending artery (LAD) 12; left circumflex coronary artery (LCx) 2; right coronary artery 6] and 20 vessels were severely stenotic (70-99%). In 5 patients' three vessels, in 6 patients' two vessels, and in 13 patients' a single vessel was involved. Wall motion, perfusion abnormalities, and late contrast enhancement consistent with nonviable myocardium were analyzed at apical, at midventricular, and basal levels on short-axis images of cardiac MRI in concordance with the segmental irrigation areas of the coronary arteries. RESULTS: Impaired perfusion was observed on the corresponding irrigation segments of 39 vessels of 40 coronary artery branches. Wall motion abnormalities were present on corresponding irrigation areas of 30 severely stenotic vessels. Combined evaluation of wall motion and perfusion, segments with the decreased left ventricular contraction, and perfusion matched with the corresponding irrigation areas of all of the 40 stenotic or occluded vessels. CONCLUSION: A correlation was found between the combined assessments of myocardial perfusion, wall motion, and viability on late contrast enhancement on cardiac MRI with the clinical and angiography findings. Thus this combined MRI protocol can be used for the evaluation of ischemic heart disease.     

Semiquantitative assessment of myocardial perfusion using magnetic resonance imaging: evaluation of appropriate thresholds and segmentation models

RATIONALE AND OBJECTIVES: The aim of the study was to determine optimal thresholds for semiquantitative perfusion parameters and to evaluate the influence of different segmentation models in detecting malperfused regions. MATERIAL AND METHODS: In 6 healthy subjects and 13 patients with coronary artery disease, contrast-enhanced first-pass perfusion imaging was performed using a SR-TrueFISP-sequence. Thresholds for semiquantitative parameters were established, and different segmentation models of the left ventricular myocardium were tested. The standard of reference for patient studies was single photon emission computed tomography. RESULTS: Optimal thresholds were determined in healthy subjects for the perfusion parameters upslope, AUC, and peak SI of mv-0.5*std, mv-1.5*std, and mv-1.0*std, respectively. Using the optimal threshold for each parameter/segmentation combination sensitivities and specificities of stress studies were between 66% and 93% and 77% and 92%, respectively. Subdivision of radial segments into subendo/subepicardial segments increased sensitivities for perfusion deficits. CONCLUSIONS: Subdivision of radial myocardial segments is essential in analysis of magnetic resonance first-pass perfusion series. Semiquantitative perfusion parameters possess different sensitivities for the detection of perfusion deficits.     

Influence of angiographic collateral circulation on myocardial perfusion in patients with chronic total occlusion of a single coronary artery and no prior myocardial infarction.

The functional role of various angiographic grades for coronary collaterals remains controversial. The aim of this study was to assess the influence of the Rentrop angiographic grading of coronary collaterals on myocardial perfusion in patients with single-vessel chronic total occlusion (CTO) and no prior myocardial infarction (MI). METHODS: The study included 56 patients with single-vessel CTO and no prior MI who underwent rest-stress myocardial perfusion SPECT and coronary angiography within 6 mo. All patients had angiographic evidence of coronary collaterals. Patients were divided according to the Rentrop classification: Group I had grade 1 or 2 (n = 25) and group II had grade 3 collaterals (n = 31). RESULTS: Group I had a higher frequency of resting regional wall motion abnormalities on left ventriculography (52.6% vs. 19.2% [P = 0.019]). The mean perfusion scores of the overall population showed severe and extensive stress perfusion defects (summed stress score of 14.1 +/- 7.1 and summed difference score of 12.9 +/- 6.9) but minimal resting perfusion defects (summed rest score of 1.0 +/- 2.7). No perfusion scores differed between the 2 groups. The perfusion findings suggested that chronic stunning rather than hibernation is the principal cause of regional wall motion abnormalities in these patients. CONCLUSION: In the setting of single-vessel CTO and no prior MI, coronary collaterals appear to protect against resting perfusion defects. Excellent angiographic collaterals may prevent resting regional wall motion abnormalities but do not appear to protect against stress-induced perfusion defects.     

Comparison of exercise, dipyridamole, adenosine, and dobutamine stress with the use of Tc-99m tetrofosmin tomographic imaging

PURPOSE: The purpose of this study was to compare defect extent and severity and myocardial uptake with exercise and pharmacologic stress with technetium-99m (Tc-99m) tetrofosmin tomographic myocardial perfusion imaging. BACKGROUND: Detection of stress-induced myocardial perfusion defects depends on both a disparity in blood flow between normal and stenotic vessels and the extraction fraction and linearity of myocardial uptake of the tracer. There are limited clinical data for exercise or pharmacologic stress with Tc-99m tetrofosmin tomographic myocardial perfusion imaging. METHODS: Thirty-one patients with coronary artery disease and 7 with a < 5% likelihood of coronary artery disease underwent on separate days Tc-99m tetrofosmin single-photon emission computed tomographic imaging at rest and after exercise, dipyridamole, adenosine, and dobutamine stress. Images were interpreted by a blinded consensus of 3 experienced readers with a 17-segment model and 5-point scoring system. RESULTS: Compared with exercise, the summed stress score was smaller with dipyridamole (P < .01), and the reversibility score was smaller with both dipyridamole (P < .01) and dobutamine (P < .05), whereas the number of abnormal and reversible segments was less with both dipyridamole (P < .01 and P < .001, respectively) and dobutamine (both P < .05). No significant differences were found in the summed stress or reversibility scores and the number of abnormal or reversible segments between exercise and adenosine. CONCLUSIONS: Compared with exercise, defect extent, severity, and reversibility are less with dipyridamole and dobutamine with Tc-99m tetrofosmin single photon emission computed tomographic imaging.     

Nuclear imaging is more sensitive for the detection of viable myocardium than dobutamine echocardiography

Intact perfusion, preserved metabolism of free fatty acids and glucose, and the presence of contractile reserve have been used as markers of viable myocardium. However, not all viable myocardium may exhibit all these characteristics. Accordingly, these features were evaluated in patients with chronic coronary artery disease and left ventricular dysfunction. Fourteen patients with chronic ischaemic heart disease and depressed left ventricular function (LVEF 34+/-10%) perfusion was evaluated by early resting 201Tl single photon emission computed tomography (SPECT), fatty acid utilization by 15-p-[123I]iodophenyl-3-(R,S)-methylpentadecanoic acid SPECT, glucose utilization by 2-[18F]fluoro-2-deoxy-D-glucose SPECT and contractile reserve (CR) by dobutamine echocardiography. The comparison of the different modalities was restricted to akinetic or dyskinetic myocardium as assessed by resting 2-dimensional echocardiography. For all techniques a 13-segment model was used. Sixty-four of 182 segments (35%) showed akinesia or dyskinesia. Intact perfusion was found in 33/64 (52%) segments. Fatty acid utilization was maintained in 38/64 (59%) segments and glucose utilization was maintained in 38/64 (59%) segments. CR was present in significantly fewer segments: 21 of 64 (33%) (P<0.01 vs glucose and fatty acid utilization). In the 21 segments with preserved CR, perfusion was intact in 16/21 (76%) segments, fatty acid utilization in 19/21 (90%) segments and glucose utilization was preserved in all (100%) segments. Conversely, in the 43 segments without CR, 17 segments (40%) showed intact perfusion, 19 segments (44%) preserved fatty acid utilization and 17 (40%) still showed preserved glucose utilization. Disagreement in segments between the viability markers was caused mainly by segments without CR but preserved perfusion, fatty acid or glucose utilization. The substantial number of segments with preserved glucose and fatty acid utilization but without contractile reserve, suggests an underestimation of myocardial viability by dobutamine echocardiography.     

Reduction of coronary flow reserve in areas with and without ischemia on stress perfusion imaging in patients with coronary artery disease: A study using oxygen 15-labeled water PET

BACKGROUND: Myocardial perfusion single photon emission computed tomography (SPECT) occasionally fails to detect coronary stenosis in patients with coronary artery disease (CAD). We evaluated coronary flow reserve (CFR) using oxygen 15-labeled water in areas with and without ischemia on technetium 99m tetrofosmin stress perfusion SPECT in patients with angiographically documented CAD. METHODS AND RESULTS: Twenty-seven patients with CAD and eleven age-matched normal subjects were studied. Baseline myocardial blood flow (MBF) and MBF during hyperemia induced by intravenous adenosine triphosphate infusion (0.16 mg. kg(-1). min(-1)) were determined with the use of O-15-labeled water positron emission tomography, and the CFR was calculated. Tc-99m tetrofosmin stress/rest SPECT was performed for comparison. On the basis of the results of coronary angiography and SPECT, coronary segments were divided into 3 types: segments with coronary stenosis and a perfusion abnormality on stress SPECT imaging (group A, n = 16), segments with coronary stenosis without a perfusion abnormality (group B, n = 42), and remote segments with no coronary stenosis or perfusion abnormality (group C, n = 18). Baseline MBF values were similar among the 3 groups. CFR in group A was lower (1.82 +/- 0.54) than in group B (2.22 +/- 0.87, P <.05), in group C (2.92 +/- 1.21, P <.01), and in normal segments (3.86 +/- 1.24, P <.001). CFR in group B was lower than in group C (P <.02) and in normal segments (P <.001). CFR in group C was lower than in normal segments (P <.02). CONCLUSIONS: Areas with a perfusion abnormality on stress SPECT had reduced CFR. In the areas without a perfusion abnormality and with coronary stenosis, lowering of CFR was intermediate between the areas with a perfusion abnormality and remote segments. Moreover, CFR was slightly, but significantly, lower in remote segments in patients with CAD compared with normal segments.     

Clinical implication of reverse redistribution on99mTc-sestamibi images for evaluating ischemic heart disease

OBJECTIVE: The purpose of this study was to clarify the usefulness of 99mTc-sestamibi (MIBI) delayed imaging in the assessment of the severity of myocardial ischemia in patients with coronary artery stenosis. METHODS: Forty-three angina pectoris with coronary stenosis of greater than 75% were enrolled in this study. Myocardial perfusion SPECT images were obtained 1 and 6 hours after an intravenous injection of MIBI at rest. Stress myocardial perfusion SPECT images were also acquired after the injection of MIBI. And myocardial fatty acid metabolism images were obtained 30 minutes after the injection of BMIPP at rest. Myocardial perfusion SPECT images were divided into 20 segments which were semiquantitatively assessed according to a 4-level defect score scale: score 0 (normal) to score 3 (severely); then the extent score (ES) and severity score (SS) were calculated. RESULTS: The sensitivity for myocardial ischemia showed the highest rate at 88.3% with MIBI delayed SPECT. According to the coronary angiography findings, MIBI stress SPECT and MIBI delayed SPECT detected the severity and extent of ischemia with more sensitivity than MIBI early SPECT in 12 patients (group A) with stenosis of more than 75% but less than 90% (p < 0.01). Even though MIBI stress SPECT detected the severity and extent of ischemia in 31 patients (group B) with stenosis of more than 90% but less than 100%, there was no significant difference between MIBI stress SPECT and MIBI delayed SPECT. BMIPP SPECT revealed significant differences between group A and group B regarding the severity of myocardial ischemia. MIBI reverse redistribution was observed in 33 patients and no significant difference existed between groups A and B. CONCLUSIONS: Myocardial washout of MIBI was frequently observed in patients with angina pectoris and the detection accuracy for ischemia was high. MIBI imaging is considered useful for assessment not only of myocardial perfusion but also mitochondrial function. The imagings with BMIPP and delayed MIBI could serve to determine the severity of myocardial ischemia more accurately.     

Contrast-enhanced magnetic resonance imaging of hypoperfused myocardium.

Contrast-enhanced magnetic resonance (MR) imaging can define myocardial perfusion defects due to acute coronary occlusion. However, since most clinically important diagnostic examinations involve coronary arteries with subtotal stenoses, we investigated the ability of MR imaging with a manganese contrast agent to detect perfusion abnormalities in a canine model of partial coronary artery stenosis. The contrast agent was administered after the creation of a partial coronary artery stenosis with the addition of the coronary vasodilator dipyridamole in six of 12 animals. The hearts were imaged ex situ using gradient reversal and spin-echo sequences, and images were analyzed to determine differences in signal intensity between hypoperfused and normally perfused myocardium. Comparison of MR images with regional blood flow and thallium-201 measurements showed good concordance of hypoperfused segments in those animals given dipyridamole, with 75% of the abnormal segments correctly identified. In those animals not given dipyridamole, 48% of segments were correctly identified. Thus, ex vivo MR imaging with a paramagnetic contrast enhancement can be used to detect acute regional myocardial perfusion abnormalities due to severe partial coronary artery stenoses.     

Risk stratification in patients with remote prior myocardial infarction using rest-stress myocardial perfusion spect: prognostic value and impact on referral to early catheterization

BACKGROUND: Little is known about the prognostic value of myocardial perfusion single photon emission computed tomography (SPECT) in patients with remote prior myocardial infarction (MI). METHODS AND RESULTS: We identified 1413 consecutive patients with remote prior MI who underwent rest-stress myocardial perfusion SPECT. Semiquantitative visual analysis of 20 SPECT segments was used to define the summed stress, rest, and difference scores. The number of non-reversible segments was used as an index of infarct size. During follow-up (>or=1 year), 118 hard events occurred: 64 cardiac deaths (CDs) and 54 recurrent MIs. Annual CD and hard event rates increased significantly as a function of SPECT abnormality. For summed stress scores less than 4, 4 to 8, 9 to 13, and more than 13, the annual CD rates were 0.4%, 0.9%, 1.7%, and 3.5%, respectively (P =.002). Patients with small MI (<4 non-reversible segments) and no or mild ischemia (summed difference score or=4 non-reversible segments) had moderate to high annual CD rates (3.7%-6.6%) regardless of the extent of ischemia. Nuclear testing added incremental prognostic information to pre-scan information. Compared with a strategy in which all patients are referred to catheterization, a strategy that referred only those patients with a risk for CD of greater than 1% by myocardial perfusion SPECT resulted in a 41.6% cost savings. CONCLUSIONS: Myocardial perfusion SPECT adds incremental value to pre-scan information and is highly predictive and cost-efficient in the risk stratification of patients with remote prior MI. Patients with normal or mildly abnormal scan results or small MI in combination with absent or mild ischemia have a low risk for CD.     

<Superscript>99m</Superscript>Tc sestamibi myocardial perfusion scintigraphy with the novel use of metamizol for the detection of perfusion reversibility

PURPOSE: This study aims to investigate whether induction with metamizol, an analgesic-antipyretic drug having spasmolitic activity, could be used to increase the detectability of ischemic/jeopardized myocardium during MPS (myocardial perfusion scintigraphy). MATERIALS AND METHODS: Metamizol-enhanced rest MPS (45 min after administration of 1 g metamizol orally, 740 MBq (99m)Tc sestamibi was injected, MPS was acquired 45 min later) was performed in 21 patients who had perfusion defects on their previous stress-rest (99m)Tc sestamibi MPS. Blood pressure was monitored at 15-min intervals. Stress, rest, metamizol-rest MPS images were interpreted on the model of 20 segments using a visual uptake score (VUS; 0 = normal, 1 = mild, 2 = moderate, 3 = significant decreases, 4 = no uptake). (99m)Tc sestamibi uptake ratios (MIBI-UR; mean counts in the region of the perfusion defect/mean counts in the region of the normal-perfused wall) were obtained on each MPS and compared with each other. Average MIBI-UR in each scintigraphic examination was calculated. MPS were compared with coronary angiography results. RESULTS: VUS and MIBI-UR results showed that metamizol-rest MPS displayed the defect reversibility better than rest MPS. Of the 14 segments with fixed perfusion defects on stress-rest MPS, 8 showed improvement of perfusion after metamizol induction. In 33 segments, lesion reversibility was better delineated on metamizol-rest MPS. Metamizol-induced sestamibi uptake was significantly higher (p < 0.001) than stress/baseline rest examinations as calculated by the MIBI-UR. Blood pressure remained unaltered. Coronary angiography results were in concordance with metamizol induced MPS. CONCLUSIONS: Metamizol-enhanced rest MPS increases detectability of ischemic/viable myocardium during MPS. Metamizol should be discontinued like nitrates before stress MPS since it may mask the visualization of ischemic perfusion defects.     

The role of left ventricular hypertrophy and diabetes in the presence of transient ischemic dilation of the left ventricle on myocardial perfusion SPECT images.

Transient ischemic dilation of the left ventricle found on SPECT myocardial perfusion imaging (MPI) is an accepted marker of severe and extensive coronary artery disease (CAD) and poor prognosis. The influence of other clinical variables on the incidence of transient ischemic dilation is less certain. The aim of this study was to investigate clinical factors that may influence the incidence of transient ischemic dilation. In particular, we looked at factors that may independently affect subendocardial perfusion, such as left ventricular hypertrophy (LVH) and diabetes. METHODS: MPI studies of 103 consecutive patients who had undergone recent coronary angiography (< or =6 mo) and transthoracic echocardiography within a year of stress electrocardiography-gated MPI were retrospectively analyzed. Transient ischemic dilation was assessed quantitatively using a software program. A ratio cutoff of > or =1.22 was considered to represent transient ischemic dilation. Summed stress score and summed difference score (ischemia score) were determined using the standard 17-segment 5-point scoring system to quantify myocardial ischemia. LVH was defined as a left ventricular wall thickness of >11 mm on M-mode echocardiography. Severe CAD was defined as severe stenosis (> or =90%) of either the left anterior descending artery or both the right coronary and lateral circumflex arteries. RESULTS: Nineteen (18%) of the 103 patients had transient ischemic dilation, 19 (18%) had LVH, and 23 (22%) were diabetic. A high percentage had severe CAD (46/103 [45%]), whereas 57 of 103 (55%) had less severe CAD (30/103 [29%]) or nonsignificant CAD (26/103 [25%]). Severe CAD (P < 0.001), diabetes (P < 0.0001), LVH (P < 0.003), and the ischemia score (P < 0.023) were independent predictors of transient ischemic dilation by multivariate logistic regression. In patients with severe CAD, the effect of LVH on the incidence of transient ischemic dilation was additive, increasing the incidence from 21% (8/38) without LVH to 75% (6/8) with LVH (P < 0.006). Likewise, with severe CAD, the incidence of transient ischemic dilation rose from 21% (7/33) in patients without diabetes to 54% (7/13) in those with diabetes (P < 0.04). CONCLUSION: The presence of transient ischemic dilation on myocardial perfusion SPECT is associated with the presence of severe CAD, but this association is modified by the presence of LVH and diabetes.     

Threshold,incidence, and predictors of prognostically high-risk silent ischemia in asymptomatic patients without prior diagnosis of coronary artery disease

Background  Little is known about incidence, threshold, and predictors of prognostically relevant silent ischemia (SI). The aim was to study these three aspects of silent coronary artery disease (CAD). Methods  In total, 3,664 consecutive asymptomatic patients without prior diagnosis of CAD undergoing myocardial perfusion SPECT (MPS) were evaluated and followed-up ≥1 year for Events (HE): cardiac death or myocardial infarction. MPS was interpreted using a 20 segment model to define summed stress, rest, and difference scores (the extent of % myocardium ischemic was derived). Prognostic high-risk ischemia was defined as ischemia consistent with a HE rate ≥3%. Results  Overall, ≥7.5% myocardium ischemic was consistent with high risk. Twenty-one and six percent of patients had ischemia and high-risk ischemia, respectively. Patients with high-risk ischemia had a worse prognosis than patients with less SI, HE rate of 3.1 and 0.4%, respectively, (P = .0001). Sex, age, diabetes, hypertension, abnormal resting ECG, angina, peak heart rate, blood pressure during treadmill testing, ST-depression, and Duke treadmill score were independent predictors of relevant SI. Conclusions  In total, ≥7.5% myocardium ischemic revealed to be consistent with high risk. Six percent of patients had evidence of high-risk SI. Diagnostic scores are provided to most likely identify patients with high-risk SI. This work was presented in part at the annual meeting of the European Society of Cardiology in Munich, Germany, 2004.     

Fluorine-18 deoxyglucose PET for assessment of viable myocardium in perfusion defects in 99mTc-MIBI SPET: a comparative study in patients with coronary artery disease

Extent and frequency of viable tissue in myocardial segments yielding a perfusion defect on technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI), single photon emission tomography (SPET) at rest was prospectively investigated with 2-¹⁸F-2-deoxyglucose (¹⁸FDG) positron emission tomography (PET) in 46 patients with chronic coronary artery disease (CAD). Of these, 43 had a history of old myocardial infarction. For comparative visual and quantitative evaluation of identical anatomical slices, PET image files were converted into the SPET file structure and into the same matrix size. SPET and PET images were documented and visually (9 segments/patient) or semiquantitatively evaluated by a target-like polar map. Relative perfusion was expressed in percentage of peak ^99mTc-MIBI uptake. Sample ¹⁸FDG uptake was related to the ¹⁸FDG uptake in the area of such maximal perfusion (¹⁸FDG uptake was 100% at the 100% ^99mTc-MIBI uptake area). Of 414 segments, 167 (40%) revealed a resting perfusion defect. ¹⁸FDG uptake was present in 38 (23%) of the defects, while another 40 (24%) segments yielded ¹⁸FDG uptake in the periphery of the defect. When grouped according to the degree of ^99mTc-MIBI uptake-reduction (in percentage of peak activity), 80% of severe defects (30% of peak uptake), 48% of moderate (31%–50% of peak uptake) and 31% of mild (>50% of peak uptake) defects were considered as non-viable on the basis of ¹⁸FDG uptake. Complete viability was found in none of the severe defects in contrast to 29% of moderate and 35% of mild perfusion defects. From these data we conclude that ^99mTc-MIBI uptake as a myocardial perfusion marker underestimates myocardial viability in patients with chronic CAD and after myocardial infarction. Nevertheless, only moderate reductions of ^99mTc-MIBI uptake seem to imply a greater likelihood for viability. Comparative analysis of metabolism and flow is possible with different tomographic systems and is valuable for clinical evaluation of the cardiac patient. Offprint requests to: C. AltehoeferThis paper presents in part results of the doctoral thesis of C. Feinendegen and was supported in part by the EEC Concerted Action on PET in Cardiology.It is dedicated to Prof. L.E. Feinendegen, Jülich/Düsseldorf on the occasion of his 65th birthday.     

Combined first-pass perfusion and viability study at MR imaging in patients with non-ST segment-elevation acute coronary syndromes: feasibility study

PURPOSE: To assess the feasibility of combined perfusion and viability testing by using magnetic resonance (MR) imaging in one setting in patients with non-ST segment-elevation acute coronary syndromes. MATERIALS AND METHODS: The data of 13 patients (mean age, 68 years; range, 40-85 years) at high risk for myocardial infarction who underwent MR imaging at 1.5 T were reviewed. Risk factors were increased troponin T levels in seven, reversible ST depression on an electrocardiogram in four, history of myocardial infarction in two, and presence of heart failure in four. Cine imaging of the left ventricle was performed with a true-fast imaging with steady-state precession (FISP) sequence to assess the regional myocardial contraction and ejection fraction. After injection of 0.1 mmol per kilogram of body weight of gadopentetate dimeglumine, first-pass MR images were obtained by using an inversion-recovery true-FISP sequence at rest and during infusion of adenosine (140 microg/kg/min). Resting and stress images were assessed qualitatively for abnormal regional perfusion (hypoenhancement). The myocardium was divided into three radial segments corresponding to the three coronary artery territories. Delayed (after 15 minutes) contrast material-enhanced images were acquired with use of a segmented inversion-recovery fast low-angle shot sequence. Conventional coronary angiograms were compared with the first-pass images. A more than 50% stenosis in diameter in any coronary artery was considered substantial. Mann-Whitney test was used to assess any significant difference between the left ventricular ejection fraction (LVEF) in patients with and those without myocardial infarct. RESULTS: Mean LVEF was 51.5% (range, 30%-77%). First-pass stress perfusion studies depicted 25 segments of hypoenhancement in 11 patients. Comparison of first-pass perfusion defects with findings on coronary angiograms indicated an overall sensitivity of 92% (24 of 26) and specificity of 92% (12 of 13) in detection of substantial coronary artery disease. Infarcts detected from hyperenhancement on delayed contrast-enhanced images were present in eight segments (four were transmural) in five patients. No significant difference was noted in the LVEF between patients with and those without infarct (P =.724). CONCLUSION: Combined stress perfusion and viability MR imaging was feasible in patients with acute coronary syndromes. First-pass MR perfusion defects compare well with the presence of substantial coronary artery stenosis on conventional angiograms.     

Validation of a model of left ventricular segmentation for interpretation of SPET myocardial perfusion images

Several models of left ventricular segmentation have been developed that assume a standard coronary artery distribution, and are currently used for interpretation of single-photon emission tomography (SPET) myocardial perfusion imaging. This approach has the potential for incorrect assignment of myocardial segments to vascular territories, possibly over- or underestimating the number of vessels with significant coronary artery disease (CAD). We therefore sought to validate a 17-segment model of myocardial perfusion by comparing the predefined coronary territory assignment with the actual angiographically derived coronary distribution. We examined 135 patients who underwent both coronary angiography and stress SPET imaging within 30 days. Individualized coronary distribution was determined by review of the coronary angiograms and used to identify the coronary artery supplying each of the 17 myocardial segments of the model. The actual coronary distribution was used to assess the accuracy of the assumed coronary distribution of the model. The sensitivities and specificities of stress SPET for detection of CAD in individual coronary arteries and the classification regarding perceived number of diseased coronary arteries were also compared between the two coronary distributions (actual and assumed). The assumed coronary distribution corresponded to the actual coronary anatomy in all but one segment (#3). The majority of patients (80%) had 14 or more concordant segments. Sensitivities and specificities of stress SPET for detection of CAD in the coronary territories were similar, with the exception of the RCA territory, for which specificity for detection of CAD was better for the angiographically derived coronary artery distribution than for the model. There was 95% agreement between assumed and angiographically derived coronary distributions in classification to single- versus multi-vessel CAD. Reassignment of a single segment (segment #3) from the LCX to the LAD territory further improved the model's fit with the anatomic data. It is concluded that left ventricular segmentation using a model with assumed coronary artery distribution is valid for interpretation of SPET myocardial perfusion imaging.