Strain rate imaging differentiates transmural from non-transmural myocardial infarction: a validation study using delayed-enhancement magnetic resonance imaging.

OBJECTIVES: The aim of this study was to determine if strain rate imaging (SRI) correlates with the transmural extent of myocardial infarction (MI) measured by contrast-enhanced magnetic resonance imaging (Ce-MRI). BACKGROUND: Identification of the transmural extent of myocardial necrosis and degree of non-viability after acute MI is clinically important. METHODS: Tissue Doppler echocardiography with SRI and Ce-MRI were performed in 47 consecutive patients with a first acute MI between days 2 and 6 and compared to 60 age-matched healthy volunteers. Peak myocardial velocities and peak myocardial deformation strain rates were measured. Location and size of the infarct zone was confirmed by Ce-MRI using the delayed enhancement technique with a 16-segment model. RESULTS: Contrast-enhanced MRI identified transmural infarction in 21 patients, non-transmural infarction in 15 (mean transmurality of infarct 72.3 +/- 10.6%), and another 11 patients with subendocardial infarction (<50% transmural extent of the left ventricular wall). Peak systolic strain rate (SRs) of the transmural infarction segments was significantly lower compared to normal myocardium or with non-transmural infarction segments (both p < 0.0005). A cutoff value of SRs >-0.59 s(-1) detected a transmural infarction with high sensitivity (90.9%) and high specificity (96.4%), and -0.98 s(-1) >SRs >-1.26 s(-1) distinguished subendocardial infarction from normal myocardium with a sensitivity of 81.3% and a specificity of 83.3%. CONCLUSIONS: Peak myocardial deformation by SRI can differentiate transmural from non-transmural MI, and it allows noninvasive determination of transmurality of the scar after MI and thereby the extent of non-viable myocardium.

Left ventricular systolic asynchrony after acute myocardial infarction in patients with narrow QRS complexes.

BACKGROUND: The aim of the study was to assess the degree of left ventricular (LV) asynchrony after myocardial infarction (MI) in patients with a narrow QRS complex using tissue Doppler imaging (TDI) and correlate this with the site and extent of the infarction measured by contrast-enhanced magnetic resonance imaging (Ce-MRI). METHODS: Echocardiography with TDI and Ce-MRI was performed within 6 days of acute MI in 47 patients and compared with 69 age-matched healthy volunteers. Regional myocardial velocities were assessed in 12 segments, and the corresponding systolic velocity (Sm), early diastolic velocity (Em), as well as the time to peak Sm (Ts) and time to peak Em (Te) were measured. To assess LV synchronicity, SDs of Ts (Ts-SD) and Te (Te-SD) of all 12 segments were computed. Location and size of infarct were confirmed by Ce-MRI with a 16-segment model. RESULTS: All the patients had a normal QRS complex duration. The Ts-SD was significantly prolonged in the MI group when compared with controls (42.2 +/- 13.7 vs 18.0 +/- 7.0 milliseconds, P < .001). The Ts-SD was longer in patients with anterior than inferior MI (46.8 +/- 13.9 vs 34.6 +/- 8.5 milliseconds, P = .002). Stepwise multiple regression analysis revealed that infarct size was the main independent predictor of systolic asynchrony ( B = 0.79, 95% CI 0.75-1.23, P < .001). Asynchrony was not related to the transmurality of the infarction. CONCLUSIONS: Myocardial infarction has a significant impact on LV synchronicity even in those with a narrow QRS complex. The degree of LV systolic asynchrony is mainly determined by the infarct size and not transmurality.

Screening of colonic tumors by air-inflated magnetic resonance (MR) colonography.

PURPOSE: To assess the accuracy of air-inflated magnetic resonance (MR) colonography for the detection of colonic lesions. MATERIALS AND METHODS: A total of 36 patients underwent both colonoscopy and air-inflated MR colonography. Breath-hold sequences (volumetric interpolated breath-hold examination (VIBE) coronal, and half-Fourier acquisition single-shot turbo spin-echo (HASTE) axial and coronal, both supine and prone) were performed with a 1.5T scanner. The detection of colonic lesions by MR colonography was then correlated with the findings from the colonoscopy performed on the same day. RESULTS: Two patients were unable to complete the MR colonography examination. Analysis was based on the results from 34 patients (17 males and 17 females, 38-70 years old, mean age = 54.9 years) who completed both examinations. MR colonography depicted two of two colonic tumors, one of one P4 (> 2 cm) polyp, one of two P2 (0.5-1 cm) polyps, and two of 11 P1 (< 0.5 cm) polyps. False-positive MR colonography interpretations were noted for one P1 polyp and two P2 polyps. The overall sensitivity, positive predictive value, and accuracy of MR colonography were 38%, 67%, and 46.2%, respectively. For the detection of endoluminal lesions > 5 mm, air-inflated MR colonography yielded a sensitivity of 75%, specificity of 93.3%, accuracy of 91.2%, positive predictive value of 60%, and negative predictive value of 96.6%. CONCLUSION: Air-inflated MR colonography is a new technique that deserves further investigation.

Magnetic resonance colonography in the detection of colonic neoplasm in high-risk and average-risk individuals.

OBJECTIVES: Magnetic resonance colonography (MRC) is a new noninvasive diagnostic modality for colorectal cancer. However, the use of MRC in the detection of colorectal neoplasm in average-risk individuals remains unknown. This study determined the performance and the patient's preference of MRC in the detection of colorectal neoplasm. METHODS: Both high-risk (i.e., symptoms suggestive of colorectal neoplasm, positive fecal occult blood test, history of colorectal cancer in one or more first-degree relatives) and average-risk (i.e., asymptomatic individuals >50 yr) individuals were recruited. MRC was performed immediately prior to conventional colonoscopy (CC) by using air inflation without contrast. The finding on CC together with histology was used as a gold standard. Patients' pain and discomfort score were recorded immediately and 24 h after the procedure. They were also asked about their preferences for the two procedures. RESULTS: A total of 165 patients (79 average risk and 86 high risk) were recruited. Eight patients had incomplete MRC and one patient had failed CC. Of the remaining 156 patients, 4 were found to have colonic cancer and 31 were found to have 67 polyps. MRC correctly identified 3 cancers (sensitivity 75%, specificity 99.3%) and 4 patients with colonic polyps (sensitivity 12.9% and specificity 97.6%). Sensitivity of MRC tended to be lower in polyps <10 mm in size and in average-risk individuals. The mean procedure time of CC was significantly shorter than MRC (13.6 +/- 6.7 vs 20.6 +/- 2.7 min, p < 0.001). Although there was no significant difference in the pain and discomfort scores of the 2 procedures, 75% of patients preferred CC to MRC. CONCLUSIONS: The performance of MRC when used in the detection of colonic neoplasm in average-risk individuals is unsatisfactory.

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.

Metabolic control patterns in acute phase and regenerating human liver determined in vivo by 31-phosphorus magnetic resonance spectroscopy.

OBJECTIVE: To elucidate the metabolic changes occurring within hepatocytes during acute phase reaction and liver regeneration. SUMMARY BACKGROUND DATA: The metabolic events occurring within the liver during the hepatic stress response are poorly understood. The authors used in vivo 31-phosphorus magnetic resonance spectroscopy to study hepatic metabolism after surgical trauma with and without loss of liver cell mass. METHODS: Three groups were studied: five patients undergoing partial hepatectomy; five patients in whom laparotomy and colonic resection was performed; and five patients treated by thyroidectomy. Hepatic metabolism was evaluated by 31-phosphorus magnetic resonance spectroscopy before surgery and serially thereafter on postoperative days 2, 4, 6, 14, and 28. Estimation of liver volume by magnetic resonance imaging and blood sampling for biochemistry were performed at the same time points. RESULTS: The authors found that alterations in hepatocyte phospholipid metabolism occurred after surgery that were correlated with changes in circulating acute phase proteins. Liver regeneration after hepatectomy was also associated with a derangement in energy metabolism, measured by a decrease in the ratio of ATP to its hydrolysis product inorganic phosphate. The depleted energy status was mirrored in biochemical indices of liver function, and restitution paralleled the course of restoration of hepatic cell mass. CONCLUSIONS: These findings indicate that changes in liver metabolism after surgery reflect the magnitude of tissue injury and the quantity of functioning liver cells. Acute phase responses dominate the initial recovery period at the expense of less important endergonic functions. When liver parenchyma is lost, the acute phase reaction is maintained and further supported by a rapid replenishment of hepatocytes, which can even be considered a continuation of acute phase physiology. Modulation of liver function within the framework of overall hepatic energy economy is one mechanism for matching energy supply with increased demands during these processes.