Feasibility of Simple Evaluation of Coronary Artery Calcium Using a Number of Chest Computed Tomography Slices: A Multicenter Study.

Objective: We aimed to evaluate the visual measurements of coronary artery calcium (CAC) on nonelectrocardiogram (ECG)-gated chest computed tomography (CT) using a simple scoring method that involves counting the number of CT slices containing CAC. Materials and Methods: We analyzed 163 participants who underwent both coronary and chest CT examinations at six centers within 3 months. Agatston scores were calculated on standard ECG-gated scans and classified as none (0), mild (1-99), moderate (100-400), or severe (>400). Next, chest CT images were reconstructed to standard 5.0 mm axial slices. Then, CAC on chest CT scans was measured using two methods: the Weston score (sum of the assigned score of each vessel, range: 0-12) and number of slices showing CAC (Ca-slice#). Results: When the Weston score and Ca-slice# were divided into four levels according to the optimal divisional levels corresponding to the Agatston score classes, good agreements with the 4-grade Agatston score were observed (kappa value=0.610 and 0.794, respectively). The sensitivity and specificity of Ca-slice# ≥9 to identify severe Agatston scores of >400 were 86% and 96%, respectively. Conclusion: The Ca-slice#, a simple scoring method using chest CT scans, was in good agreement with the ECG-gated Agatston score.

Intravenous IgG Reduces Pathogenic Autoantibodies, Serum IL-6 Levels, and Disease Severity in Experimental Bullous Pemphigoid Models.

Bullous pemphigoid (BP) is an autoimmune blistering disease characterized by autoantibodies to COL17. Currently, systemic corticosteroids are used as first-line treatments for BP; alternatively, intravenous administration of high-dose IgG (IVIG) has been shown to be effective for patients with steroid-resistant BP in clinical practice. However, the effect of IVIG on BP has not fully been investigated. To examine the effects and mechanisms of action of IVIG against BP, we performed IVIG experiments using two experimental BP mouse models. One is a passive-transfer BP model that reproduces subepidermal separation in neonatal mice by the passive transfer of IgGs against COL17, such as polyclonal or monoclonal mouse IgG or IgG from BP patients. The other is an active BP model that continuously develops a disease phenotype in adult mice. IVIG decreased pathogenic IgG and the disease scores in both models. Injected IVIG distributed throughout the dermis and the intercellular space of the lower epidermis. Notably, IVIG inhibited the increase of IL-6 in both models, possibly by suppressing the production of IL-6 by keratinocytes. These results suggest that the inhibitory effects of IVIG on BP are associated with the reduction of pathogenic IgG and the modulation of cytokine production.

A Comparison of Heart Rate Response between 12 hours Caffeine Abstinence and 24 hours in Adenosine Stress Myocardial Perfusion Imaging.

The aim of this study was to examine whether the heart rate response to adenosine differs after 12 hours [Good control (Good-C)] versus 24 hours [Excellent control (Exc-C)] of caffeine abstinence in adenosine stress thallium-201 (TL) myocardial perfusion imaging (MPI). Patients (n=729) with suspected ischemic heart disease underwent adenosine TL-MPI after 12 (n=226) and 24 (n=503) hours of caffeine abstinence. There was not significant differences between the heart rate of Exc-C and Good-C in 0-2 min after adenosine infusion (0 min 63.7±9.5 versus 63.7±10.0, 1 min 66.4±10.6 versus 65.3±10.5, 2 min 72.3±11.2 versus 70.6±11.4). The heart rate of Exc-C was higher compared to Good-C in 3-6 min after adenosine infusion (3 min 75.6 ±11.7 versus 73.3±11.6 p=0.013, 4 min 79.2±12.9 versus 76.7±12.2 p=0.012, 5 min 79.4±12.6 versus 76.8±12.4 p=0.009, 6 min 79.4±12.5 versus 77.0±12.3 p=0.016). Therefore, the longer caffeine abstinence, namely 24 hours self-restraint, is effective in adenosine TL-MPI.

Quantification of the myocardial area at risk using coronary CT angiography and Voronoi algorithm-based myocardial segmentation.

OBJECTIVES: The purpose of this study was to estimate the myocardial area at risk (MAAR) using coronary computed tomography angiography (CTA) and Voronoi algorithm-based myocardial segmentation in comparison with single-photon emission computed tomography (SPECT). METHODS: Thirty-four patients with coronary artery disease underwent 128-slice coronary CTA, stress/rest thallium-201 SPECT, and coronary angiography (CAG). CTA-based MAAR was defined as the sum of all CAG stenosis (>50%) related territories (the ratio of the left ventricular volume). Using automated quantification software (17-segment model, 5-point scale), SPECT-based MAAR was defined as the number of segments with a score above zero as compared to the total 17 segments by summed stress score (SSS), difference (SDS) score map, and comprehensive SPECT interpretation with either SSS or SDS best correlating CAG findings (SSS/SDS). Results were compared using Pearson's correlation coefficient. RESULTS: Forty-nine stenoses were observed in 102 major coronary territories. Mean value of CTA-based MAAR was 28.3 ± 14.0%. SSS-based, SDS-based, and SSS/SDS-based MAAR was 30.1 ± 6.1%, 20.1 ± 15.8%, and 26.8 ± 15.7%, respectively. CTA-based MAAR was significantly related to SPECT-based MAAR (r = 0.531 for SSS; r = 0.494 for SDS; r = 0.814 for SSS/SDS; P < 0.05 in each). CONCLUSIONS: CTA-based Voronoi algorithm myocardial segmentation reliably quantifies SPECT-based MAAR. KEY POINTS: • Voronoi algorithm allows for three-dimensional myocardial segmentation of coronary CT angiography • Stenosis-related CT myocardial territories correlate to SPECT based area at risk • CT angiography myocardial segmentation may assist in clinical decision-making.

[Intravenous adenosine and radiopharmaceutical injection in the same line was feasible in adenosine stress myocardial perfusion. imaging].

Adenosine stress myocardial perfusion imaging was performed with an intravenous adenosine and radiopharmaceutical injection in the same line. A syringe containing 720 µg/kg of adenosine in 40 ml of saline was prepared and injected at the constant infusion rate of 400 ml/h. Adenosine was temporarily stopped by the stopcock when 1.5 ml of thallium was injected for 0.5 second from the three-way stopcock with two ways opened. Thereafter, the stopcock was returned to the original position in 0.5 second, and adenosine flow returned to the constant flow rate again. In this method, 0.75% of adenosine total dose was injected at a rate of 3.0 ml/s and adenosine was stopped for 3.6 second. There were no significant differences in either effects and adverse events of adenosine between this method and two intravenous injection line method. Adenosine stress in one venous line method would be an easy method maintaining the dose effect and safety.

Transmural perfusion gradient in adenosine triphosphate stress myocardial perfusion computed tomography.

BACKGROUND: The aim of the present study was to assess semi-quantification of myocardial perfusion using adenosine triphosphate (ATP)-stress myocardial perfusion computed tomography (MPCT) in patients with coronary artery disease (CAD). METHODS AND RESULTS: Seventeen patients with CAD underwent ATP-stress MPCT, stress myocardial perfusion scintigraphy (MPS) and coronary angiography (CAG). With ATP loading (0.16 mg·kg⁻¹·min⁻¹, 5 min) and slow infusion of contrast medium (2 ml/s, 100 ml), stress images were acquired using prospective electrocardiogram-gated 64-slice CT. Stress MPCT images were analyzed according to the transmural perfusion gradient (TMPG; difference between subendocardial and epicardial attenuation, divided by wall thickness; Hounsfield units [HU]/mm) per segment, and summed TMPG was compared with those of stress MPS and CAG per territory and patient, respectively. There were 36 CAG-proved stenotic vessels in 51 (17 × 3) territories. There were significant correlations between TMPG and MPS stress score per segment, per territory and per patient, respectively (P<0.05). Summed TMPG in territories with and without >70% coronary stenosis was 32.3HU/mm (-1.9~90.9) and 14.5 HU/mm (-5.6~38.4; P<0.05). For detecting coronary artery stenosis, sensitivity, specificity, positive and negative predictive values using the summed TMPG were 72%, 87%, 93% and 57%, in comparison with summed MPS (64%, 73%, 85%, and 46%). CONCLUSIONS: Semi-quantification of myocardial perfusion using TMPG has great potential to evaluate the severity of myocardial ischemia, similarly to MPS score.

Cardiac surgery for annuloaortic ectasia and mitral regurgitation in an adult patient with dextrocardia.

We report a surgical case of dextrocardia complicated with annuloaortic ectasia (AAE) and mitral regurgitation, which induced congestive heart failure. Preoperative electrocardiography-gated multidetector-row computed tomography (MDCT) showed the following complex cardiovascular abnormalities without motion artifacts: dextrocardia, situs inversus, polysplenia, AAE, absence of the inferior vena cava, azygos vein continuation, drainage of the hepatic vein into the right atrium, and bilateral superior venae cavae. On the basis of the MDCT data, we established a cardiopulmonary bypass; and a modified Bentall procedure (Piehler method) and mitral valve replacement were performed without complications.

Improvement of image resolution of brain SPECT by use of the wide-angle offset acquisition method.

OBJECTIVE: Cerebral SPECT images require high spatial and contrast resolution for precise evaluation of the abnormal tracer distribution in the brain. A shorter data acquisition time is preferable so that artifacts due to patient movement are avoided. We tried to shorten data acquisition time applying larger sampling angle and offset acquisition method, in which half degree of the step angle was shifted in the opposite gamma camera of the dual-detector SPECT system. METHODS: A simulation study was performed with a 3-dimensional mathematical phantom. The phantom studies were performed with a hot-rod phantom and a brain phantom. A clinical study with 99(m)Tc-ECD SPECT was also performed on a patient who had a cerebral infarction. Reconstruction of images was done for the normal 6° and 12° onset and 12° offset. Data for the 12° offset were acquired by shifting of sampling angles of the opposite detector by half (6°) of the sampling angles of 12°. The MLEM algorithm was used for image reconstruction. Image qualities in the simulation study, the phantom studies, and the clinical study were compared for the 6° and 12° onset, and for the 12° offset by quantitative analysis with use of profile curves. RESULTS: Analysis of the profile curves revealed that the image quality of the 12° offset was better than that of the 12° onset and compared to that of the 6° onset in the simulation study, the phantom studies, and the clinical study. CONCLUSIONS: The present study indicates that wide-angle offset data acquisition improves the image resolution of brain SPECT compared to onset data acquisition with the same sampling time.

Functional assessment of coronary artery flow using adenosine stress dual-energy CT: a preliminary study.

We attempted to assess coronary artery flow using adenosine-stress and dual-energy mode with dual-source CT (DE-CT). Data of 18 patients with suspected coronary arteries disease who had undergone cardiac DE-CT were retrospectively analyzed. The patients were divided into two groups: 10 patients who performed adenosine stress CT, and 8 patients who performed rest CT as controls. We reconstructed an iodine map and composite images at 120 kV (120 kV images) using raw data with scan parameters of 100 and 140 kV. We measured mean attenuation in the coronary artery proximal to the distal portion on both the iodine map and 120 kV images. Coronary enhancement ratio (CER) was calculated by dividing mean attenuation in the coronary artery by attenuation in the aortic root, and was used as an estimate of coronary enhancement. Coronary stenosis was identified as a reduction in diameter of >50% on CT angiogram, and myocardial ischemia was diagnosed by adenosine-stress myocardial perfusion scintigraphy. The iodine map showed that CER was significantly lower for ischemic territories (0.76 ± 0.06) or stenosed coronary arteries (0.77 ± 0.06) than for non-ischemic territories (0.95 ± 0.21, P=0.02) or non-stenosed coronary arteries (1.07 ± 0.33, P<0.001). The 120 kV images showed no difference in CER between these two groups. Use of CER on the iodine map separated ischemic territories from non-ischemic territories with a sensitivity of 86% and a specificity of 75%. Our quantification is the first non-invasive analytical technique for assessment of coronary artery flow using cardiac CT. CER on the iodine map is a candidate method for demonstration of alteration in coronary artery flow under adenosine stress, which is related to the physiological significance of coronary artery disease.

Myocardial hypoenhancement in a case of acute coronary syndrome with normal coronary arteries: demonstration by 64-slice multidetector computed tomography.

A 48-year-old man presented with severe chest pain that had started 2 h before and ST elevation on the electrocardiogram. Cardiac computed tomography (CT) was performed using a 64-slice multidetector scanner (MDCT) to assess coronary artery stenosis at 3 h after the onset. Coronary CT angiography showed no significant stenosis at the coronary arteries, but CT myocardial images at systole demonstrated predominantly subendocardial hypoenhancement in the anterior wall. Cardiac CT that combined coronary angiography and myocardial imaging demonstrated myocardial hypoenhancement in a case of acute coronary syndrome with normal coronary arteries, which may be related to microvascular dysfunction caused by vasospastic angina or microvascular angina.

Regional myocardial blood flow measured by stress multidetector computed tomography as a predictor of recovery of left ventricular function after coronary artery bypass grafting.

BACKGROUND: Multidetector-row computed tomography (MDCT) applications have expanded to evaluation of myocardial blood flow (MBF) and viability. We quantified regional MBF pre- and post-coronary artery bypass grafting (CABG) using adenosine stress and cardiac 64-MDCT, and investigated whether the results predict MBF and left ventricular (LV) function recovery after CABG. METHODS: We studied 321 regions in 19 CABG patients who underwent adenosine stress 64-row MDCT perfusion imaging and cine magnetic resonance imaging pre- and post-CABG. Myocardial blood flow was estimated from linear regression equation slopes using Patlak plot analyses and compared with LV function by measuring wall thickening (%WT) using cine magnetic resonance imaging. RESULTS: Overall mean MBFs were 1.39 +/- 0.49 and 1.95 +/- 0.49 mL/(g min) pre- and post-CABG (P < .0001). Myocardial blood flow in revascularized areas increased significantly (pre-CABG 1.18 +/- 0.45, post-CABG 1.99 +/- 0.66 mL/[g min], P < .001), whereas nonischemic areas showed no difference (1.79 +/- 0.70 and 1.97 +/- 0.46 mL/[g min], P = .14). Revascularized areas with preoperative MBF > or = 0.9 mL/(g min) showed significantly greater MBF improvement than those with preoperative MBF <0.9 mL/(g min) (P = .04). In patients with preoperative LV dysfunction (ejection fraction <40%), %WT in revascularized areas with pre-CABG MBF > or = 0.9 mL/(g min) improved significantly after CABG (pre-%WT 40.9 +/- 22.9, post-%WT 52.8 +/- 20.6, P = .03) versus those with pre-CABG MBF <0.9 mL/(g min) (pre-%WT 53.2 +/- 35.5, post-%WT 42.5 +/- 17.0, P = .40). CONCLUSIONS: Our results demonstrated more significantly increased MBF post-CABG than pre-CABG, particularly in revascularized areas. Regional MBF before CABG may predict MBF and LV function recovery, in the short term, after CABG.

Peri-infarct dysfunction in post-myocardial infarction: assessment of 3-T tagged and late enhancement MRI.

OBJECTIVE: To determine LV function at different distances from myocardial infarction (MI) by using 3-T tagged MRI and late gadolinium enhancement (LGE). METHODS: Cardiac MR images were acquired from 21 patients with previous MI. The harmonic phase (HARP) method was used to calculate radial and circumferential strain (RS, CS). The two strains were synchronised by subtracting the CS from the RS at the same time, and this was defined as the efficient strain (ES). Peak strain (P-RS, P-CS, P-ES) and time to peak strain (T-RS, T-CS, T-ES) were used as estimates of contractile function. Based on the presence of LGE, myocardium was classified into infarct, border zone, adjacent and remote areas. RESULTS: P-RS and P-ES were significantly greater for remote than for adjacent and infarct areas. P-CS values were significantly greater for remote and border zone than for infarct areas. T-RS and T-ES were significantly shorter for remote and border zone than for infarct areas. T-CS was significantly shorter for border zone than for infarct areas. CONCLUSION: Contractile dysfunction demonstrated by peak strain was correlated with location at different distances from the infarct. In the border zone, contractile deformation was characterised as earlier T-RS, T-CS and T-ES and greater P-CS than in the infarct area.

Myocardial ischemia in acute coronary syndrome: assessment using 64-MDCT.

OBJECTIVE: We investigated the performance of 64-MDCT myocardial imaging in assessing myocardial ischemia in acute coronary syndrome (ACS). MATERIALS AND METHODS: Cardiac CT was performed in 35 patients with ACS: 24 patients with acute myocardial infarction (AMI) and 11 patients with unstable angina pectoris (UAP). We reconstructed 2D myocardial images at diastolic and systolic phases using the same raw data as those used for coronary CT angiography. The CT number in the myocardium was used as an estimate of ischemia. The myocardium was shown using a color scale that depicts faint low-density areas more clearly than gray scale. We evaluated the variations in myocardial enhancement during the cardiac cycle in the territory of the culprit lesion. In addition, we classified patients on the basis of the transmurality of myocardial enhancement and examined whether this feature correlates with myocardial damage. RESULTS: Myocardial imaging at systole showed myocardial hypoenhancement in territories of the culprit lesion in 91% of patients with ACS, 96% of patients with AMI, and 75% of patients with UAP. The hypoenhancement areas at systole tended to be more extensive than those at diastole. The transmural extent of hypoenhancement at systole correlated with myocardial damage, which was shown by myocardial biomarkers. CONCLUSION: CT myocardial imaging can be used to assess myocardial ischemia in the appropriate region of ACS with high sensitivity.

Detection of myocardial ischemia using 64-slice MDCT.

BACKGROUND: The purpose is to investigate the ability of 64-slice multidetector computed tomography (MDCT) at rest in detecting myocardial ischemia, conventionally depicted by myocardial perfusion scintigraphy (MPS). METHODS AND RESULTS: In 75 patients with suspected coronary artery disease, cardiac CE-MDCT at rest and stress/rest MPS were performed. The 2D myocardial images were reconstructed in diastolic and systolic phases using raw data from coronary computed tomography (CT) angiography. CT numbers in the myocardium were used as an estimate of myocardial enhancement. The myocardium was shown using a color scale that depicts faint low-density areas more clearly than gray scale. The variation in myocardial enhancement was evaluated at systole and diastole for those segments depicted as ischemia on MPS. A pattern of transient endocardial hypo-enhancement at systole and normal enhancement at diastole as the ischemic pattern on CT myocardial image was defined. MPS diagnosed myocardial ischemia in 40 of 75 patients. Use of the ischemic pattern on CT images distinguished patients with and without ischemia with a sensitivity of 90%, specificity of 83%, positive predictive value of 86% and negative predictive value of 88%. CONCLUSIONS: CT myocardial imaging at rest demonstrates a characteristic enhancement pattern for ischemia. This has potential as a non-invasive method for detecting ischemia.

History of cardiac computed tomography: single to 320-detector row multislice computed tomography.

Since the introduction of computed tomography (CT) over 30 years ago, the challenge of imaging the beating heart has been a driving force in the innovation of cardiac CT. Imaging the anatomy and physiology of the heart demands temporal, spatial and contrast resolution is arguably greater than for any other organ system in the body. Great progress has been achieved in using CT to evaluate coronary artery stenosis and plaque composition. In addition, techniques to evaluate cardiac function, including myocardial perfusion, regional ventricular wall motion, systolic thickening, ejection fraction, valve function, and congenital cardiac abnormalities are also gaining a foothold in clinical practice as adjuncts to or replacements for invasive coronary angiography, cardiac single photon emission CT (SPECT) imaging, ultrasound and magnetic resonance imaging (MRI). This review summarizes the major accomplishments and future directions in this field, with emphasis on developments over the past 10 years.

Analysis of microvascularity after reperfused acute myocardial infarction using the maximum slope method of contrast-enhanced magnetic resonance imaging.

PURPOSE: The aim of this study was to analyze microvas-cularity after reperfused acute myocardial infarction (AMI) using the maximum slope method of contrastenhanced cardiac magnetic resonance imaging (CMR). MATERIALS AND METHODS: CMR and resting (201)T1 single photon emission computed tomography (SPECT) images were obtained in 30 consecutive patients after reperfused AMI and 10 controls. After bolus injection of gadolinium diethylenetriamine pentaacetic acid, first-pass CMR images were obtained using the True-FISP sequence. Time-intensity curves were generated by measuring the signal intensity in the myocardium and left ventricle. The arterial input function was obtained from the left ventricular time-intensity curve. On the basis of the maximum slope method, the microvascular index (MVI) was calculated by dividing the maximum initial upslope of the myocardium by the initial upslope of the left ventricle. RESULTS: The MVI was significantly lower in the segments related to the occluded coronary artery. MVIs in segments with (201)Tl uptake of 50%-59% of peak were significantly lower than in those with (201)Tl uptake of 60%-69%. MVIs in segments with (201)Tl uptake of <50% of peak were significantly lower than in those with (201)Tl uptake of 50%-59%. CONCLUSION: This study presents a method that directly assesses microvascularity after reperfused AMI.

Quantification of myocardial perfusion by contrast-enhanced 64-MDCT: characterization of ischemic myocardium.

OBJECTIVE: Assessment of hemodynamic changes in ischemic cardiac segments at rest using CT has yet to be performed. We hypothesized that variations in subendocardial perfusion during the cardiac cycle might be related to the appearances of ischemia. The purpose of this study was to investigate myocardial perfusion in ischemic segments using contrast-enhanced 64-MDCT. SUBJECTS AND METHODS: We performed cardiac MDCT at rest and stress/rest (201)Tl myocardial perfusion scintigraphy (MPS) in 34 patients with suspected coronary artery disease. We reconstructed 2D long- and short-axis cardiac images in diastolic and systolic phases using raw data from coronary CT angiography. The attenuation value (in Hounsfield units) in the myocardium was used as an estimate of myocardial perfusion. We measured the subendocardial intensity of 17 segments according to the American Heart Association classification. Systolic perfusion or diastolic perfusion was calculated by dividing the subendocardial intensity at systole or diastole, respectively, for each segment by the mean value across all segments for each patient. We used stress/rest MPS to evaluate the variation in myocardial perfusion at systole and diastole for the segments diagnosed as ischemic or nonischemic. RESULTS: Systolic perfusion for ischemic segments was significantly lower than that for nonischemic segments in 15 of 17 segments. The difference between systolic perfusion and diastolic perfusion in ischemic segments was significantly lower than that in nonischemic segments (14 of 17 segments). There was no significant difference in diastolic perfusion between ischemic and nonischemic segments (15 of 17 segments). CONCLUSION: Our results suggest that a pattern of subendocardial hypoperfusion at systole and normal perfusion at diastole characterizes ischemic myocardium.

Quantification of regional myocardial blood flow using first-pass multidetector-row computed tomography and adenosine triphosphate in coronary artery disease.

BACKGROUND: The feasibility of using cardiac multidetector-row computed tomography (MDCT) technology in the quantitative assessment of myocardial blood flow (MBF) using the adenosine triphosphate (ATP) load technique was investigated in the present study. METHODS AND RESULTS: The study group comprised 14 patients (11 men, 3 women, age range 52-79 years, mean age 69.2 years) who underwent cardiac cine MDCT using the ATP-load technique. MBF was estimated from the slope of the linear regression equation with Patlak plots analysis. The overall average MBF was 1.83+/-0.62 ml . g(-1) . min(-1). Mean MBF in territories with stenosis on coronary angiography was 1.19+/-0.36 ml . g(-1) . min(-1) and 2.06+/-0.54 ml . g(-1) . min(-1) (p<0.01) in territories without stenosis. The average MBF in territories with moderate to severe ischemia on myocardial perfusion scintigraphy was 1.32+/-0.14 ml .g(-1 ). min(-1 )and 1.95+/-0.64 ml . g(-1) . min(-1) (p<0.01) in territories without ischemia. CONCLUSION: MDCT can be used to quantify MBF using first-pass dynamic data.

Clinical importance of microvascular obstruction on contrast-enhanced MRI in reperfused acute myocardial infarction.

BACKGROUND: The aim of the present study was to investigate the clinical importance of microvascular obstruction (MO) on contrast-enhanced magnetic resonance imaging (MRI), comparing it with the myocardial perfusion index (MPI) assessed using first-pass MRI. METHODS AND RESULTS: Cardiac MRI was performed in 33 patients within 7 days after reperfusion of a myocardial infarction (MI). Using a bolus injection of Gd-DPTA, first-pass images were obtained with the Turbo-FLASH sequence. Time-intensity curves in the left ventricular cavity and in myocardial sections were generated and then the MPI was assessed by the maximum slope method. Late enhancement (LE) was assessed using the true-FISP sequence. According to the transmurality of LE, the patients were classified into 3 groups: Group 1 included patients with localized endocardial enhancement; Group 2, patients with transmural enhancement; Group 3, patients having LE with MO. In cases of anterior infarction, the MPI for the anterior wall and parts of the inferior wall in Group 3 was significantly lower than that for Group 1 and 2. For inferior infarction, the MPI for parts of the inferior wall in Group 3 was significantly lower than that for Group 1 and 2. CONCLUSION: MO is related to lower MPI, indicating severe microvascular damage. LE with or without MO is an important marker of perfusion status after reperfused MI.