Matthias Regenfus

Contrast-enhanced MRI and routine single photon emission computed tomography (SPECT) perfusion imaging for detection of subendocardial myocardial infarcts: an imaging study

BACKGROUNDnMyocardial infarcts are routinely detected by nuclear imaging techniques such as single photon emission computed tomography (SPECT) myocardial perfusion imaging. A newly developed technique for infarct detection based on contrast-enhanced cardiovascular magnetic resonance (CMR) has higher spatial resolution than SPECT. We postulated that this technique would detect infarcts missed by SPECT.nnnMETHODSnWe did contrast-enhanced CMR and SPECT examinations in 91 patients with suspected or known coronary artery disease. All CMR and SPECT images were scored, using a 14-segment model, for the presence, location, and spatial extent of infarction. To compare each imaging modality to a gold standard, we also acquired contrast-enhanced CMR and SPECT images in 12 dogs with, and three dogs without, myocardial infarction as defined by histochemical staining.nnnFINDINGSnIn animals, contrast-enhanced CMR and SPECT detected all segments with nearly transmural infarction (>75% transmural extent of the left-ventricular wall). CMR also identified 100 of the 109 segments (92%) with subendocardial infarction (<50% transmural extent of the left-ventricular wall), whereas SPECT identified only 31 (28%). SPECT and CMR showed high specificity for the detection of infarction (97% and 98%, respectively). In patients, all segments with nearly transmural infarction, as defined by contrast-enhanced CMR, were detected by SPECT. However, of the 181 segments with subendocardial infarction, 85 (47%) were not detected by SPECT. On a per patient basis, six (13%) individuals with subendocardial infarcts visible by CMR had no evidence of infarction by SPECT.nnnINTERPRETATIONnSPECT and CMR detect transmural myocardial infarcts at similar rates. However, CMR systematically detects subendocardial infarcts that are missed by SPECT.

Incidence and characteristics of segmental postsystolic longitudinal shortening in normal, acutely ischemic, and scarred myocardium

OBJECTIVEnMyocardial longitudinal shortening after aortic valve closure (postsystolic shortening [PSS]) is considered a marker of pathology with diagnostic potential. However, PSS can also occur in healthy subjects. We, therefore, investigated the occurrence and characteristics of PSS in control subjects and patients, and how to distinguish normality from disease.nnnMETHODSnIn 20 young control subjects, 10 older control subjects, 30 patients with acute myocardial infarction (acute ischemia), and 10 patients with postischemic myocardial scar, longitudinal myocardial deformation was measured with Doppler tissue strain rate (SR) imaging. Segmental SR and strain were visually and quantitatively analyzed and compared.nnnRESULTSnIn young control subjects, PSS was found in 98 of 313 segments (31%) and showed gaussian distribution (median 1.3%). During ejection time, median peak SR was -1.4 s(-1) and median strain -16.6%. In older control subjects, parameters differed only slightly. In acutely ischemic and scarred myocardium, both systolic strain and SR were significantly reduced or inverted. In disease, PSS occurred significantly more often (78% and 79%, respectively), was significantly higher in magnitude, and its peak occurred later than in young and older control subjects.nnnCONCLUSIONnPSS is a normal finding in healthy subjects occurring in approximately one-third of myocardial segments and, thus, is not always a marker of disease. Our data indicate that pathologic PSS can be detected by coexisting reduction in systolic strain and, second, by exceeding a postsystolic strain magnitude cutoff.

Variability of Repeated Coronary Artery Calcium Measurements by Electron Beam Tomography

In 120 patients, the mean interscan variability of coronary calcium quantification by electron beam tomography was 19.9% (median 7.8%) for the traditional calcium score, and 16.2% (median 5.7%) for volumetric scoring. Although this difference was not significant, there was a significant influence of the total amount of calcium, number of acquired images, and image noise on interscan reproducibility.

Noninvasive detection of coronary artery stenosis using contrast-enhanced three-dimensional breath-hold magnetic resonance coronary angiography

OBJECTIVESnThe purpose of this study was to evaluate a contrast-enhanced three-dimensional (3D) breath-hold magnetic resonance (MR) technique for detection of coronary artery stenoses.nnnBACKGROUNDnThe accuracy of previously published MR coronary angiography protocols varies widely. Recently, coronary artery imaging using T1-shortening contrast agent has become possible, but so far there are no data concerning its clinical application.nnnMETHODSnMagnetic resonance coronary angiography was performed in 50 patients with suspected coronary artery disease. Magnetic resonance data acquisition using an ultrafast 3D gradient-echo sequence lasted over 32 heartbeats within one single breath-hold. Twenty milliliters of gadopentetate dimeglumine was injected at a flow rate of 1 ml/s for two successive studies covering the main coronary arteries in single-oblique planes. Stenosis assessment by MR was compared with significant (diameter stenosis > 50%) stenoses on X-ray angiography. Evaluation was limited to the proximal and mid-coronary artery segments.nnnRESULTSnTwo hundred sixty-eight of 350 artery segments (76.6%) could be evaluated. Left circumflex coronary artery was only evaluable in 50% of cases by MR. In the evaluable segments, 48 of 56 stenoses and 193 of 212 nonstenotic segments were correctly classified by MR. On a patient basis, MR correctly identified 34 of 36 patients with and 8 of 14 patients without significant coronary stenoses as demonstrated by X-ray angiography (sensitivity 94.4%, specificity 57.1%).nnnCONCLUSIONSnOblique projection contrast-enhanced MR coronary angiograms obtained within one single breath-hold permit identification of patients with coronary stenoses in the proximal and mid segments of the major coronary arteries with satisfactory accuracy.

Relationship of contractile function to transmural extent of infarction in patients with chronic coronary artery disease.

OBJECTIVESnWe sought to determine the relationship of contractile function to the transmural extent of infarction (TEI) in patients with chronic coronary artery disease.nnnBACKGROUNDnIn the setting of reperfused, chronic myocardial infarction (MI), the relationship of contractile function to the TEI has not been established.nnnMETHODSnWe studied function by cine magnetic resonance imaging (MRI) and the TEI by contrast-enhanced MRI in 31 patients with single-vessel disease 162 +/- 62 days after reperfused first MI.nnnRESULTSnOf all 516 segments with MI, blinded observers were unable to detect abnormal thickening in 193 (37%), and wall thickening measured quantitatively in these segments was 66 +/- 28%. Of the 193 segments, 163 (84%) were infarcts limited to the subendocardium. The average TEI reached 53% before half of the patients had abnormal contractile function. When patients with small MI (< or =5% of total left ventricular [LV] mass) were excluded, the average TEI reached 43% before half the patients had abnormal function. In subjects with small MI (< or =5% of total LV mass [n = 13]), even segments with TEI >75% had normal function (14 of 14) because they were surrounded by normally moving neighbor segments.nnnCONCLUSIONSnIn the setting of reperfused chronic MI, the TEI approaches 50% before contractile dysfunction can be systematically identified. Contractile function cannot be used to rule out chronic MI.

Prognostic value of routine cardiac magnetic resonance assessment of left ventricular ejection fraction and myocardial damage: An international, multicenter study

Background— Cardiac magnetic resonance (CMR) is considered the reference standard for assessment of left ventricular ejection fraction (LVEF) and myocardial damage. However, few studies have evaluated the relationship between CMR findings and patient outcome, and of these, most are small and none multicenter. We performed an international, multicenter study to assess the prognostic importance of routine CMR in patients with known or suspected heart disease. Methods and Results— From 10 centers in 6 countries, consecutive patients undergoing routine CMR assessment of LVEF and myocardial damage by cine and delayed-enhancement imaging (DE-CMR), respectively, were screened for enrollment. Clinical data, CMR protocol information, and findings were collected at all sites and submitted to the data coordinating center for verification of completeness and analysis. The primary end point was all-cause mortality. A total of 1560 patients (age, 59±14 years; 70% men) were enrolled. Mean LVEF was 45±18%, and 1049 (67%) patients had hyperenhanced tissue (HE) on DE-CMR indicative of damage. During a median follow-up time of 2.4 years (interquartile range, 1.2, 2.9 years), 176 (11.3%) patients died. Patients who died were more likely to be older (P<0.0001), have coronary disease (P=0.004), have lower LVEF (P<0.0001), and have more segments with HE (P<0.0001). In multivariable analysis, age, LVEF, and number of segments with HE were independent predictors of mortality. Among patients with near-normal LVEF (≥50%), those with above-median HE (>4 segments) had reduced survival compared to patients with below- or at-median HE (P=0.02). Conclusions— Both LVEF and amount of myocardial damage as assessed by routine CMR are independent predictors of all-cause mortality. Even in patients with near-normal LVEF, significant damage identifies a cohort with a high risk for early mortality.

Noninvasive coronary angiography by magnetic resonance imaging, electron-beam computed tomography, and multislice computed tomography

In recent years, several techniques for noninvasive imaging of the coronary artery lumen (noninvasive coronary angiography) have been developed. These techniques include magnetic resonance imaging, electron-beam computed tomography, and, most recently, multislice computed tomography. Each of these techniques has specific advantages and disadvantages. Currently, EBCT seems to permit the most robust coronary artery imaging. In the future, imaging modalities will have to be further improved and validated in order to define specific areas for potential clinical applications.

Comparison of contrast-enhanced breath-hold and free-breathing respiratory-gated imaging in three-dimensional magnetic resonance coronary angiography

Suppression of respiratory motion is one of the major challenges of magnetic resonance (MR) coronary angiography. Two approaches to compensate for respiratory motion have often been proposed: breath-hold (BH) and free-breathing respiratory-gated (FBRG) imaging. So far, however, these approaches have never been directly compared. MR coronary angiography was performed in 32 patients with suspected coronary artery disease. MR data were acquired using contrast-enhanced BH and FBRG 3-dimensional MR coronary angiographic techniques. MR images were compared with regard to image quality using quantitative parameters and with regard to accuracy for stenosis detection in the proximal and mid-coronary segments in comparison to x-ray angiography. With regard to image quality, BH was superior to FBRG. Signal-to-noise ratio was 29.1 +/- 10.7 for BH versus 18.8 +/- 9.7 for FBRG (p <0.05) and contrast-to-noise was 18.0 +/- 7.4 for BH versus 11.3 +/- 7.9 for FBRG (p </=0.05). One hundered seventy-one of 224 coronary artery segments (76%) were evaluable in BH compared with 155 of 224 in FBRG (69%). In the evaluable segments, BH demonstrated a sensitivity of 87% (26 of 30 stenoses detected) and specificity of 92% (129 of 141 nonstenotic segments correctly identified), whereas FBRG showed a sensitivity of 60% (15 of 25) and specificity of 89% (115 of 130). Overall accuracy was 91% (155 of 171) for BH and 84% (130 of 155) for FBRG. Sensitivity was significantly higher for BH (p = 0.0320), whereas specificity and overall accuracy were not significantly different. Thus, contrast-enhanced BH MR coronary angiography compares favorably to FBRG imaging with regard to image quality and detection of coronary stenoses.

A direct comparison of noninvasive coronary angiography by electron beam tomography and navigator-echo-based magnetic resonance imaging for the detection of restenosis following coronary angioplasty.

Ropers D, Regenfus M, Stilianakis N, et al. A direct comparison of noninvasive coronary angiography by electron beam tomography and navigator-echo-based magnetic resonance imaging for the detection of restenosis following coronary angioplasty. Invest Radiol 2002;37:386–392. rationale and objectives. To compare electron beam tomography (EBT) with MR imaging (MRI) for detection of restenosis after coronary angioplasty (PTCA). methods. One hundred eighteen patients after PTCA were investigated. By EBT, 50 axial images were acquired (3-mm slice thickness, 120–160 mL radiographic contrast agent). MRI was performed using respiratory-gated sequences (24–48 cross-sections, 2-mm slice thickness, 20 mL Gd-DTPA). EBT and MRI images were evaluated concerning high-grade post-PTCA restenosis (≥70%) and validated against coronary angiography. results. In EBT, 28 patients and in MRI, 31 patients were not evaluable. In the remaining patients, sensitivity for restenosis detection was 90% in EBT (17/19) and 73% in MRI (11/15;P = 0.370). In EBT, specificity was significantly higher (66% vs. 49%, P = 0.043). Overall accuracy was 71% for EBT and 53% for MRI (P = 0.014). conclusions. For the detection of high-grade restenosis after PTCA, EBT demonstrated significantly higher accuracy than MRI.

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

Regenfus M, Ropers D, Achenbach S, et al. Diagnostic value of maximum intensity projections versus source images for assessment of contrast-enhanced three-dimensional breath-hold magnetic resonance coronary angiography. Invest Radiol 2003;38:200–206. 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.