Fractal analysis in cardiovascular magnetic resonance: prognostic value of biventricular trabecular complexity in hypertrophic cardiomyopathy.

Background: Trabecular complexity can be quantified by fractal analysis based on cine images of cardiovascular magnetic resonance (CMR), yielding fractal dimension (FD) index. We aimed to investigate the prognostic value of biventricular FD in patients with hypertrophic cardiomyopathy (HCM). Methods: This retrospective study included 284 (192 men, median age 53 years) patients with HCM who underwent CMR, with median follow-up of 24 months. Biventricular trabeculae complexity was quantified as FD using short-axis cine images. The primary end point included sudden cardiac death (SCD) events. The secondary end point included both SCD events and rehospitalization due to heart failure. Cox regressions were performed. Prediction models were established by adding ventricular FDs to ESC predictors and late gadolinium enhancement (LGE) percentage and the C indices were calculated. Results: Cox regressions revealed that left ventricular (LV) maximal apical FD (HR range 1.114-1.133; all P<0.05) and right ventricular (RV) global FD (HR range 1.135-1.150; all P<0.05) were significant prognostic factors of both end points after adjustment for the European Society of Cardiology (ESC) predictors (age, maximum LV wall thickness, LV atrial size, peak left ventricular outflow tract (LVOT) gradient, family history of SCD, unexplained syncope, non-sustained ventricular tachycardia), and LGE percentage. The prediction model with the addition of biventricular FDs (C-index: 0.864-0.877) had the best performance. Conclusions: LV maximal apical FD and RV global FD were independent predictors of SCD events and rehospitalization due to heart failure in patients with HCM. The addition of biventricular FDs to the conventional prediction model contributed incremental prognosis value in HCM.

Evaluation of left ventricular strain in patients with arrhythmia based on the 3T MR temporal parallel acquisition technique.

Most of the current studies on myocardial strain are mainly applied in patients with sinus rhythm because the image quality of arrhythmias obtained with conventional scanning sequences does not meet diagnostic needs. Here, we intend to assess left ventricular (LV) global myocardial strain in patients with arrhythmias with 3 Tesla magnetic resonance (MR) and a new cine sequence. Thirty-three patients with arrhythmia and forty-eight subjects with sinus rhythm were enrolled in the study. LV myocardial thickness, cardiac function, myocardial strain and the apparent contrast-to-noise ratio (CNR) were all measured and compared using images generated by the real-time temporal parallel acquisition technique (TPAT) and the conventional cine sequence. In the arrhythmia group, the image quality of real-time TPAT was significantly better than that of the conventional cine sequence. In the arrhythmia group, the LV global peak radial strain and global peak circumferential strain values of real-time TPAT were significantly different from those of the conventional technique (radial strain, conventional: 20.27 ± 15.39 vs. TPAT: 24.14 ± 15.85, p = 0.007; circumferential strain, conventional:-12.06 ± 6.60 vs. TPAT: -13.71 ± 6.31, p = 0.015). There was no significant difference in global peak longitudinal strain between real-time TPAT and the conventional technique (-10.94 ± 4.66 vs. -10.70 ± 5.96, p = 0.771). There was no significant difference in the cardiac function parameters between the two techniques (p > 0.05), but there was a significant difference in 12 segments of the LV wall thickness between the two sequences (p < 0.05). In the sinus rhythm group, image quality using real-time TPAT was comparable to that using the conventional technique, and there was no significant difference in any of the indices (p > 0.05). Real-time TPAT is an effective method for detection of left ventricular myocardial deformation in patients with arrhythmia.

[Feasibility of using intravascular loopless monopole antenna to image atherosclerotic plaque in a porcine model with 3.0 T magnetic resonance imaging].

OBJECTIVE: To investigate the feasibility of using intravascular loopless monopole antenna (ILMA) to image atherosclerosis plaque in a porcine model with 3.0T magnetic resonance imaging (MRI). METHODS: Atherosclerosis model was established by feeding high fat diet combined with balloon catheter injury to the endothelium in 6 pigs. After 3 months, animals underwent MRI and ILMA examination. The ILMA was invasively inserted to the distal part of abdominal vein and bilateral common iliac veins. MR sequences including T1 weighted imaging (T1WI), T2WI were obtained. MR image data were transferred to post-processing station. Luminal border and external elastic membrane of the vessel were reconstructed based on the MR images. After co-register these images, vessel area, lumen area, vessel wall area and plaque burden in the same lesions imaged by different modality were calculated and compared. Finally, all animals were scarified and hematoxylin eosin (HE) staining was performed in the targeted vessels. Diagnostic accuracy of MR in delineating vessel wall and detecting plaque were analyzed and calculated by comparing with pathological results. RESULTS: The atherosclerotic model was successfully established in all 6 pigs. Good agreement of delineating vessel area, lumen area vessel, wall area and plaque burden were found between MRI and pathology with r value of 0.98, 0.95, and 0.96, respectively (P < 0.001). Compared with pathological findings, the plaque component in corresponding area imaged by MR was as follows: sensitivity and specificity of detecting lipid plaque were 77% and 69%, kappa value was 0.75 ± 0.19 (P < 0.01); sensitivity and specificity on detecting fibrotic plaque were 78% and 73%, Κ value was 0.78 ± 0.18 (P < 0.01). The sensitivity and specificity of detecting calcified plaque were 100%. ILMA results showed that the average lumen area was 49.72 mm(2), average vessel area was 124.08 mm(2), and the average vessel wall area was 74.37 mm(2), ILMA slightly overestimated these indexes as compared with pathological results. CONCLUSION: The results showed that ILMA could be used to image deepened artery and atherosclerotic plaque. Detected plaque size, vessel area, lumen area vessel, wall area, and plaque burden were comparable to pathological findings. It may thus provide an alternative method for detecting atherosclerotic plaque in future research work.

Magnetic resonance imaging features of vulnerable plaques in an atherosclerotic rabbit model.

BACKGROUND: Noninvasive detection of vulnerable plaque has a significant implication for prevention and treatment of atherosclerotic diseases. The aim of this study is to investigate the difference between vulnerable plaques and stable plaques in magnetic resonance (MR) images. METHODS: Atherosclerosis was induced in twenty male New Zealand white rabbits by high cholesterol diet and balloon injury of the abdominal aorta. After baseline (pre-triggering) MR imaging (MRI) scan, the rabbits underwent pharmaceutical triggering with Russell's viper venom and histamine to induce atherothrombosis, followed by another MRI scan 48 hours later (post-triggering). Rabbits were euthanized to obtain pathological and histological data. The results of MRI were compared with those of pathology and histology. RESULTS: MRI showed that abdominal aorta of the rabbits had pathological change of atherosclerosis in different degrees. Seventy-five plaques were analysed, among which 14 had vulnerable thrombi and 61 stable. Thrombosis was identified in 7 of 11 rabbits by post-triggering MRI, the sensitivity and K value of MR in detection of vulnerable plaque was 71% and 0.803 (P < 0.05). MRI data significantly correlated with the histopathological data in fibrous cap thickness (r = 0.749) plaque area (r = 0.853), lipid core area (r = 0.900). Compared with stable plaques, vulnerable plaques had a significantly thinner fibrous cap ((0.58 ± 0.27) mm vs. (0.95 ± 0.22) mm), larger lipid core area ((7.56 ± 2.78) mm(2) vs. (3.29 ± 1.75) mm(2)), and a higher ratio of lipid core area/plaque area ((55 ± 16)% vs. (27 ± 17)%), but plaque area was comparable in two groups on MRI. The ratio of lipid core area/plaque area was a strong predictor of vulnerable plaques. CONCLUSION: MRI could distinguish vulnerable plaques from stable plaques in a rabbit model of atherothrombosis and may thus be useful as a noninvasive modality for detection of vulnerable plaques in humans.

Detection of atherosclerotic plaque progression in the abdominal aorta of rabbits with 3T magnetic resonance imaging.

BACKGROUND: With features of high tissue contrast, MRI can be used for the qualitative and quantitative evaluation of atherosclerosis plaques. In this study we investigated the development of atherosclerosis plaque with high resolution 3T MRI in a rabbit model and compared the findings with the histopathological results. METHOD: Twenty male New Zealand white rabbits were randomly allocated into an experimental group (n = 16) and a control group (n = 4). Atherosclerotic lesions were induced in the abdominal aorta by balloon injury and cholesterol feeding. Multiple sequences MRI examination (ToF, T1WI, T2WI, and CE T1WI) were performed at the 2nd, 3rd, and 4th months after aortic denudation. Vessel wall thickness, total vessel area, lumen area, and vessel wall area were recorded. Plaque components were analyzed using histological results as a standard reference. RESULTS: Seventeen rabbits (14 in the experimental group and 3 in the control group) received all three MR examinations. Gradually, from 2 months to 4 months, vessel wall thickness and area in the experimental group increased significantly compared with the control group (P < 0.01). In the lumen area progressive stenosis was not found, even a slight dilation had developed in the experimental group. Lipid, fibrotic and calcified plaques can be differentiated by MR image. According to histological results, MRI had good performance in detection of lipid plaque. CONCLUSION: MRI can be used to monitor progression of atherosclerosis and differentiate plaque components.

[A study of neurological complications after coronary artery bypass grafting].

OBJECTIVE: To prospectively investigate the neurological complications (NC) after off-pump coronary artery bypass grafting (OPCABG), including the kinds of NC and their mobility, risk factors, prevention and treatment. METHODS: A total of 55 consecutive patients with undergoing OPCABG were evaluated from March to June 2006 at the Department of Cardiosurgery in Beijing Anzhen Hospital. Risk factors of NC were collected before operation. Nervous system physical examination, the NIH Stroke Scale (NIHSS) score evaluation, cognitive tests, imaging examination (MRI, MRA and f-MRI), anxious and depression scale were performed before and after OPCABG. NC and their kinds were identified after surgery. According to the presence or absence of NC after the operation, the patients were divided into two groups, and univariate analysis was used between the two groups. P < 0.05 was considered of statistically significant difference. RESULTS: (1) 2 cases of ischemic stroke developed after surgery (2/55), but there no case of mortality. The risk factors were not statistically different between the two groups (P > 0.05); (2) For all the patients, cognitive evaluation was normal and unchanged before and after surgery (P > 0.05), including Mini-Mental State Examination (MMSE), Clinical dementia rating (CDR) and Global Deterioration Scale (GDS); (3) Except the 2 cases of stroke, the others were normal and had no change on MRI, MRA, and f-MRI (P > 0.05) before and after surgery; (4) 7 patients with slight anxiety and one with slight depression before operation recovered completely after surgery without treatment. Both the Self-rating Anxiety Scale (SAS) and Self-rating Depression Scale (SDS) were normal and unchanged before and after surgery (P > 0.05). CONCLUSIONS: 2 cases of ischemic stroke were found among 55 patients undergoing OPCABG (2/55) and there was no mortality. There was no obvious change of cognitive function, imaging finding, anxiety and depression before and after the operation (P > 0.05). OPCABG is relatively safe for nervous system, but more exploratory work and clinical data are needed.