自制声学造影剂定量局部心肌血流效果的实验研究

目的　探讨自制声学造影剂进行心肌造影超声心动图 (myocardialechocardiography ,MCE)检查中自制声学造影剂定量局部心肌血流 (myocardialbloodflow ,MBF)的能力。 方法　MCE检测开胸犬不同状态的局部MBF ,并与放射性微球测得的心肌血流量的比较。①造影剂制备 :将 1%人体白蛋白、5 %葡萄糖和氟碳气体以一定的比例混合 ,分别以 70s ,14 0s和 2 10s进行声振 ,比较各组造影剂中微泡的大小和浓度。②MCE定量MBF :开胸犬 6条 ,分别在基础状态、静脉给予潘生丁造成的充血状态、左冠状动脉回旋支 (LCx)不同程度狭窄状态下计算MCE得出的局部MBF。③在最后狭窄状态 ,于MCE结束后左房内注入放射性微球测量局部心肌血流量。结果　①以 70s ,14 0s和 2 10s声振制成造影剂微泡的直径分别为 ( 9.0 1± 3.14 ) μm ,( 6 .45± 2 .39) μm ,( 4 .86± 2 .0 9) μm ,浓度分别为 ( 1.71± 0 .2 2 )× 10 8个 /ml,( 3.77± 0 .92 )× 10 8个 /ml,( 8.95± 0 .81)× 10 8个 /ml ,故使用与文献中造影剂直径和浓度最接近的 2 10s声振造影剂进行MCE。②在无冠脉狭窄及狭窄程度较轻时 ,随触发间歇时间的延长 ,心肌最后均可达完全显影 ,但所需时间不同。③A·β(LCx) /A·β(LAD) 与放射微球测得MBF(LCx) /MBF(LAD) 相关 (Y =0     

Quantification of myocardial blood flow with cardiovascular magnetic resonance throughout the cardiac cycle

Background

Myocardial blood flow (MBF) varies throughout the cardiac cycle in response to phasic changes in myocardial tension. The aim of this study was to determine if quantitative myocardial perfusion imaging with cardiovascular magnetic resonance (CMR) can accurately track physiological variations in MBF throughout the cardiac cycle.

Methods

30 healthy volunteers underwent a single stress/rest perfusion CMR study with data acquisition at 5 different time points in the cardiac cycle (early-systole, mid-systole, end-systole, early-diastole and end-diastole). MBF was estimated on a per-subject basis by Fermi-constrained deconvolution. Interval variations in MBF between successive time points were expressed as percentage change. Maximal cyclic variation (MCV) was calculated as the percentage difference between maximum and minimum MBF values in a cardiac cycle.

Results

At stress, there was significant variation in MBF across the cardiac cycle with successive reductions in MBF from end-diastole to early-, mid- and end-systole, and an increase from early- to end-diastole (end-diastole: 4.50 ± 0.91 vs. early-systole: 4.03 ± 0.76 vs. mid-systole: 3.68 ± 0.67 vs. end-systole 3.31 ± 0.70 vs. early-diastole: 4.11 ± 0.83 ml/g/min; all p values <0.0001). In all cases, the maximum and minimum stress MBF values occurred at end-diastole and end-systole respectively (mean MCV = 26 ± 5%). There was a strong negative correlation between MCV and peak heart rate at stress (r = −0.88, p < 0.001). The largest interval variation in stress MBF occurred between end-systole and early-diastole (24 ± 9% increase). At rest, there was no significant cyclic variation in MBF (end-diastole: 1.24 ± 0.19 vs. early-systole: 1.28 ± 0.17 vs.mid-systole: 1.28 ± 0.17 vs. end-systole: 1.27 ± 0.19 vs. early-diastole: 1.29 ± 0.19 ml/g/min; p = 0.71).

Conclusion

Quantitative perfusion CMR can be used to non-invasively assess cyclic variations in MBF throughout the cardiac cycle. In this study, estimates of stress MBF followed the expected physiological trend, peaking at end-diastole and falling steadily through to end-systole. This technique may be useful in future pathophysiological studies of coronary blood flow and microvascular function.     

Relationship between coronary flow reserve evaluated by phase-contrast cine cardiovascular magnetic resonance and serum eicosapentaenoic acid

Background

Long-term intake of long-chain n-3 polyunsaturated fatty acids (n-3 PUFAs), especially eicosapentaenoic acid (EPA) is associated with a low risk for cardiovascular disease. Phase-contrast cine cardiovascular magnetic resonance (PC cine CMR) can assess coronary flow reserve (CFR). The present study investigates the relationship between CFR evaluated by PC cine CMR and the serum EPA.

Methods

We studied 127 patients (male, 116 (91%); mean age, 72.2 ± 7.4 years) with known or suspected coronary artery disease (CAD). X-ray coronary angiography revealed no significant coronary arterial stenoses (defined as luminal diameter reduction ≥50% on quantitative coronary angiogram (QCA) analysis) in all study participants. Breath-hold PC cine CMR images of the coronary sinus (CS) were acquired to assess blood flow of the CS both at rest and during adenosine triphosphate (ATP) infusion. We calculated CFR as CS blood flow during ATP infusion divided by that at rest. Patients were allocated to groups according to whether they had high (n = 64, EPA ≥ 75.8 μg/mL) or low (n = 63, EPA < 75.8 μg/mL) median serum EPA.

Results

CFR was significantly lower in the low, than in the high EPA group (2.54 ± 1.00 vs. 2.91 ± 0.98, p = 0.038). Serum EPA positively correlated with CFR (R = 0.35, p < 0.001). We defined preserved CFR as > 2.5, which is the previously reported lower limit of normal flow reserve without obstructive CAD. Multivariate analysis revealed that EPA is an independent predictor of CFR > 2.5 (odds ratio, 1.01; 95% confidence interval, 1.00 – 1.02, p = 0.008).

Conclusions

The serum EPA is significantly correlated with CFR in CAD patients without significant coronary artery stenosis.     

How we perform cardiovascular magnetic resonance flow assessment using phase-contrast velocity mapping.

Flow assessment is an integral part of the comprehensive evaluation of the cardiovascular system. Cardiovascular magnetic resonance is well suited for flow assessment due to its non-invasive, multi-plane imaging capability unrestricted by windows of access and its ability to measure blood flow and velocity. Phase-contrast velocity mapping for flow assessment has been incorporated in all commercial scanners. It is versatile, and with appropriate hardware, software and expertise, it should be accurate and reproducible. In this article, we briefly describe the technique and indications for its use in current clinical practice. We suggest some practical tips in using the technique and describe some of the potential sources of errors and ways to overcome them. Finally, we provide several clinical examples demonstrating how to use phase-contrast velocity mapping in a number of acquired and congenital cardiovascular conditions.     

Dressler's syndrome demonstrated by late gadolinium enhancement cardiovascular magnetic resonance

A 49-year old patient presented late with an anterolateral ST-elevation myocardial infarction and was treated with rescue angioplasty to an occluded left anterior descending artery. Her recovery was complicated by low-grade pyrexia and raised inflammatory markers. Cardiovascular magnetic resonance 5 weeks after the acute presentation showed transmural infarction and global late gadolinium enhancement of the pericardium in keeping with Dressler''s syndrome.     

Evaluation of aortic valve stenosis using cardiovascular magnetic resonance: comparison of an original semiautomated analysis of phase-contrast cardiovascular magnetic resonance with Doppler echocardiography

Background- Accurate quantification of aortic valve stenosis (AVS) is needed for relevant management decisions. However, transthoracic Doppler echocardiography (TTE) remains inconclusive in a significant number of patients. Previous studies demonstrated the usefulness of phase-contrast cardiovascular magnetic resonance (PC-CMR) in noninvasive AVS evaluation. We hypothesized that semiautomated analysis of aortic hemodynamics from PC-CMR might provide reproducible and accurate evaluation of aortic valve area (AVA), aortic velocities, and gradients in agreement with TTE. Methods and Results- We studied 53 AVS patients (AVA(TTE)=0.87±0.44 cm(2)) and 21 controls (AVA(TTE)=2.96±0.59 cm(2)) who had TTE and PC-CMR of aortic valve and left ventricular outflow tract on the same day. PC-CMR data analysis included left ventricular outflow tract and aortic valve segmentation, and extraction of velocities, gradients, and flow rates. Three AVA measures were performed: AVA(CMR1) based on Hakki formula, AVA(CMR2) based on continuity equation, AVA(CMR3) simplified continuity equation=left ventricular outflow tract peak flow rate/aortic peak velocity. Our analysis was reproducible, as reflected by low interoperator variability (<4.56±4.40%). Comparison of PC-CMR and TTE aortic peak velocities and mean gradients resulted in good agreement (r=0.92 with mean bias=-29±62 cm/s and r=0.86 with mean bias=-12±15 mm Hg, respectively). Although good agreement was found between TTE and continuity equation-based CMR-AVA (r>0.94 and mean bias=-0.01±0.38 cm(2) for AVA(CMR2), -0.09±0.28 cm(2) for AVA(CMR3)), AVA(CMR1) values were lower than AVA(TTE) especially for higher AVA (mean bias=-0.45±0.52 cm(2)). Besides, ability of PC-CMR to detect severe AVS, defined by TTE, provided the best results for continuity equation-based methods (accuracy >94%). Conclusions- Our PC-CMR semiautomated AVS evaluation provided reproducible measurements that accurately detected severe AVS and were in good agreement with TTE.     

Feature tracking compared with tissue tagging measurements of segmental strain by cardiovascular magnetic resonance

Background

Left ventricular segmental wall motion analysis is important for clinical decision making in cardiac diseases. Strain analysis with myocardial tissue tagging is the non-invasive gold standard for quantitative assessment, however, it is time-consuming. Cardiovascular magnetic resonance myocardial feature-tracking (CMR-FT) can rapidly perform strain analysis, because it can be employed with standard CMR cine-imaging. The aim is to validate segmental peak systolic circumferential strain (peak SCS) and time to peak systolic circumferential strain (T2P-SCS) analysed by CMR-FT against tissue tagging, and determine its intra and inter-observer variability.

Methods

Patients in whom both cine CMR and tissue tagging has been performed were selected. CMR-FT analysis was done using endocardial (CMR-FT_endo) and mid-wall contours (CMR-FT_mid). The Intra Class Correlation Coefficient (ICC) and Pearson correlation were calculated.

Results

10 healthy volunteers, 10 left bundle branch block (LBBB) and 10 hypertrophic cardiomyopathy patients were selected. With CMR-FT all 480 segments were analyzable and with tissue tagging 464 segments.Significant differences in mean peak SCS values of the total study group were present between CMR-FT_endo and tissue tagging (-23.8 ± 9.9% vs -13.4 ± 3.3%, p < 0.001). Differences were smaller between CMR-FT_mid and tissue tagging (-16.4 ± 6.1% vs -13.4 ± 3.3%, p = 0.001). The ICC of the mean peak SCS of the total study group between CMR-FT_endo and tissue tagging was low (0.19 (95%-CI-0.10-0.49), p = 0.02). Comparable results were seen between CMR-FT_mid and tissue tagging. In LBBB patients, mean T2P-SCS values measured with CMR-FT_endo and CMR-FT_mid were 418 ± 66 ms, 454 ± 60 ms, which were longer than with tissue tagging, 376 ± 55 ms, both p < 0.05. ICC of the mean T2P-SCS between CMR-FT_endo and tissue tagging was 0.64 (95%-CI-0.36-0.81), p < 0.001, this was better in the healthy volunteers and LBBB group, whereas the ICC between CMR-FT_mid and tissue tagging was lower.The intra and inter-observer agreement of segmental peak SCS with CMR-FT_mid was lower compared with tissue tagging; similar results were seen for segmental T2P-SCS.

Conclusions

The intra and inter-observer agreement of segmental peak SCS and T2P-SCS is substantially lower with CMR-FT_mid compared with tissue tagging. Therefore, current segmental CMR-FT_mid techniques are not yet applicable for clinical and research purposes.     

Baseline correction of phase-contrast images in congenital cardiovascular magnetic resonance

Background

One potential source of error in phase contrast (PC) congenital CMR flow measurements is caused by phase offsets due to local non-compensated eddy currents. Phantom correction of these phase offset errors has been shown to result in more accurate measurements of blood flow in adults with structurally normal hearts. We report the effect of phantom correction on PC flow measurements at a clinical congenital CMR program.

Results

Flow was measured in the ascending aorta, main pulmonary artery, and right and left pulmonary arteries as clinically indicated, and additional values such as Qp/Qs were derived from these measurements. Phantom correction in our study population of 149 patients resulted in clinically significant changes in 13% to 48% of these phase-contrast measurements in patients with known or suspected heart disease. Overall, 640 measurements or calculated values were analyzed, and clinically significant changes were found in 31%. Larger vessels were associated with greater phase offset errors, with 22% of the changes in PC flow measurements attributed to the size of the vessel measured. In patients with structurally normal hearts, the pulmonary-to-systemic flow ratio after phantom correction was closer to 1.0 than before phantom correction. There was no significant difference in the effect of phantom correction for patients with tetralogy of Fallot as compared to the group as a whole.

Conclusions

Phantom correction often resulted in clinically significant changes in PC blood flow measurements in patients with known or suspected congenital heart disease. In laboratories performing clinical CMR with suspected phase offset errors of significance, the routine use of phantom correction for PC flow measurements should be considered.     

Quantification of myocardial perfusion by cardiovascular magnetic resonance

The potential of contrast-enhanced cardiovascular magnetic resonance (CMR) for a quantitative assessment of myocardial perfusion has been explored for more than a decade now, with encouraging results from comparisons with accepted "gold standards", such as microspheres used in the physiology laboratory. This has generated an increasing interest in the requirements and methodological approaches for the non-invasive quantification of myocardial blood flow by CMR. This review provides a synopsis of the current status of the field, and introduces the reader to the technical aspects of perfusion quantification by CMR. The field has reached a stage, where quantification of myocardial perfusion is no longer a claim exclusive to nuclear imaging techniques. CMR may in fact offer important advantages like the absence of ionizing radiation, high spatial resolution, and an unmatched versatility to combine the interrogation of the perfusion status with a comprehensive tissue characterization. Further progress will depend on successful dissemination of the techniques for perfusion quantification among the CMR community.     

经静脉声学造影定量心肌局部血流量的实验研究

目的：研究应用自制声学造影剂进行心肌造影超声心动图（MCE）定量显示不同冠状动脉血流量时局部心肌血流量（MB）变化的能力，以及与放射性微球的心肌血流量间的关系。了解其用于评价微循环的价值。方法：开胸犬6条，取乳头肌短轴观，采用经静脉连续滴注造影剂的方法，分别在基础状态，静脉给予潘生丁造成的充血状态，左冠状动脉回旋支（LCx）不同程度狭窄状态下通过逐渐递增触发间歇进行MC，以公式y=A(1-e^βt）拟合感兴趣区的时间－强度化曲线，以A(反映心肌局部血容量）与β（反映心肌局部血流速度）的乘积代表MBF。在最后狭窄状态，于MCE结束后左房内注入放射性微球测量局部心肌血流量，结果：（1）应用递增触发间歇的方法可清晰准确显示局部心肌显影程度的变化。（2）充血状态下，随冠状动脉血流量下降，A．β（LCx）亦减低，每条犬的LCx冠状动脉血流量变化与LCx供血区的A．β（LCx）变化呈正相关(r值分别为0.92,0.83,0.96,0.66,0.83,0.82,P值分别为0.04,0.03,0.003,0.01,0.03,0.03)。（3）A．β（LCx）／A．β（LAD）与放射微球测得MBF（LCx）／MBF（LAD）相关（Y＝0．76X＋0．0.07,r=0.82,P=0.01)，结论：经静脉连续滴注自制声学造影剂对开胸犬行MCE可获得清淅的心肌造影图像，并能够定量反映开胸犬的心肌局部血流量变化。     

Focal myocardial fibrosis assessed by late gadolinium enhancement cardiovascular magnetic resonance in children and adolescents with dilated cardiomyopathy

Background

Different patterns of late gadolinium enhancement (LGE) including mid-wall fibrosis using cardiovascular magnetic resonance (CMR) have been reported in adult patients presenting with non-ischemic dilated cardiomyopathy (DCM). In these studies, LGE was associated with pronounced LV remodelling and predicted adverse cardiac outcomes. Accordingly, the purpose of our study was to determine the presence and patterns of LGE in children and adolescents with DCM.

Methods

Patients <18 years of age presenting with severe congestive heart failure who were admitted for evaluation of heart transplantation at our centre underwent CMR examination which consisted of ventricular functional analysis and assessment of LGE for detection of myocardial fibrosis. Ischemic DCM was excluded by coronary angiography, and right ventricular endomyocardial biopsies ruled out acute myocarditis.

Results

Thirty-one patients (mean age 2.1 ± 4.2 years) with severe LV dilatation (mean indexed LVEDV 136 ± 48 ml/m²) and LV dysfunction (mean LV-EF 23 ± 8%) were examined. LGE was detected in 5 of the 31 patients (16%) appearing in various patterns characterized as mid-wall (n = 1), focal patchy (n = 1), RV insertion site (n = 1) and transmural (n = 2). Based on histopathological analysis, 4 of the 5 LGE positive patients had lymphocytic myocarditis, whereas one patient was diagnosed with idiopathic DCM.

Conclusions

In children and adolescents with DCM, focal histologically proven myocardial fibrosis is rarely detected by LGE CMR despite marked LV dilatation and severely depressed LV function. LGE occurred in various patterns and mostly in patients with inflammatory cardiomyopathy. It remains unclear whether myocardial fibrosis in childhood DCM reflects different endogenous repair mechanisms that enable favourable reverse remodelling. Larger trials are needed to assess the prognostic implications of LGE in childhood DCM.     

In vivo contrast free chronic myocardial infarction characterization using diffusion-weighted cardiovascular magnetic resonance

Background

Despite the established role of late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) in characterizing chronic myocardial infarction (MI), a significant portion of chronic MI patients are contraindicative for the use of contrast agents. One promising alternative contrast free technique is diffusion weighted CMR (dwCMR), which has been shown ex vivo to be sensitive to myocardial fibrosis. We used a recently developed in vivo dwCMR in chronic MI pigs to compare apparent diffusion coefficient (ADC) maps with LGE imaging for infarct characterization.

Methods

In eleven mini pigs, chronic MI was induced by complete occlusion of the left anterior descending artery for 150 minutes. LGE, cine, and dwCMR imaging was performed 8 weeks post MI. ADC maps were derived from three orthogonal diffusion directions (b = 400 s/mm²) and one non-diffusion weighted image. Two semi-automatic infarct classification methods, threshold and full width half max (FWHM), were performed in both LGE and ADC maps. Regional wall motion (RWM) analysis was performed and compared to ADC maps to determine if any observed ADC change was significantly influenced by bulk motion.

Results

ADC of chronic MI territories was significantly increased (threshold: 2.4 ± 0.3 μm²/ms, FWHM: 2.4 ± 0.2 μm²/ms) compared to remote myocardium (1.4 ± 0.3 μm²/ms). RWM was significantly reduced (threshold: 1.0 ± 0.4 mm, FWHM: 0.9 ± 0.4 mm) in infarcted regions delineated by ADC compared to remote myocardium (8.3 ± 0.1 mm). ADC-derived infarct volume and location had excellent agreement with LGE. Both LGE and ADC were in complete agreement when identifying transmural infarcts. Additionally, ADC was able to detect LGE-delineated infarcted segments with high sensitivity, specificity, PPV, and NPV. (threshold: 0.88, 0.93, 0.87, and 0.94, FWHM: 0.98, 0.97, 0.93, and 0.99, respectively).

Conclusions

In vivo diffusion weighted CMR has potential as a contrast free alternative for LGE in characterizing chronic MI.     

Multidirectional flow analysis by cardiovascular magnetic resonance in aneurysm development following repair of aortic coarctation

Aneurysm formation is a life-threatening complication after operative therapy in coarctation. The identification of patients at risk for the development of such secondary pathologies is of high interest and requires a detailed understanding of the link between vascular malformation and altered hemodynamics. The routine morphometric follow-up by magnetic resonance angiography is a well-established technique. However, the intrinsic sensitivity of magnetic resonance (MR) towards motion offers the possibility to additionally investigate hemodynamic consequences of morphological changes of the aorta.We demonstrate two cases of aneurysm formation 13 and 35 years after coarctation surgery based on a Waldhausen repair with a subclavian patch and a Vosschulte repair with a Dacron patch, respectively. Comprehensive flow visualization by cardiovascular MR (CMR) was performed using a flow-sensitive, 3-dimensional, and 3-directional time-resolved gradient echo sequence at 3T. Subsequent analysis included the calculation of a phase contrast MR angiography and color-coded streamline and particle trace 3D visualization. Additional quantitative evaluation provided regional physiological information on blood flow and derived vessel wall parameters such as wall shear stress and oscillatory shear index.The results highlight the individual 3D blood-flow patterns associated with the different vascular pathologies following repair of aortic coarctation. In addition to known factors predisposing for aneurysm formation after surgical repair of coarctation these findings indicate the importance of flow sensitive CMR to follow up hemodynamic changes with respect to the development of vascular disease.     

Importance of complex blood flow in the assessment of aortic regurgitation severity using phase contrast magnetic resonance imaging

This study aimed to investigate if and how complex flow influences the assessment of aortic regurgitation (AR) using phase contrast MRI in patients with chronic AR. Patients with moderate (n?=?15) and severe (n?=?28) chronic AR were categorized into non-complex flow (NCF) or complex flow (CF) based on the presence of systolic backward flow volume. Phase contrast MRI was performed repeatedly at the level of the sinotubular junction (Ao1) and 1 cm distal to the sinotubular junction (Ao2). All AR patients were assessed to have non-severe AR or severe AR (cut-off values: regurgitation volume (RVol)?≥?60 ml and regurgitation fraction (RF)?≥?50%) in both measurement positions. The repeatability was significantly lower, i.e. variation was larger, for patients with CF than for NCF (≥?12?±?12% versus?≥?6?±?4%, P?≤?0.03). For patients with CF, the repeatability was significantly lower at Ao2 compared to Ao1 (≥?21?±?20% versus?≥?12?±?12%, P?≤?0.02), as well as the assessment of regurgitation (RVol: 42?±?34 ml versus 54?±?42 ml, P?<?0.001; RF: 30?±?18% versus 34?±?16%, P?=?0.01). This was not the case for patients with NCF. The frequency of patients that changed in AR grade from severe to non-severe when the position of the measurement changed from Ao1 to Ao2 was higher for patients with CF compared to NCF (RVol: 5/26 (19%) versus 1/17 (6%), P?=?0.2; RF: 4/26 (15%) versus 0/17 (0%), P?=?0.09). Our study shows that complex flow influences the quantification of chronic AR, which can lead to underestimation of AR severity when using PC-MRI.

     

Recovery of methamphetamine associated cardiomyopathy predicted by late gadolinium enhanced cardiovascular magnetic resonance

Danon disease is a rare X-linked dominant lysosomal glycogen storage disease that can lead to severe ventricular hypertrophy and heart failure. We report a case of Danon disease with cardiac involvement evaluated with cardiovascular magnetic resonance, including late gadolinium enhancement and perfusion studies.     

Characterization of microvascular dysfunction after acute myocardial infarction by cardiovascular magnetic resonance first-pass perfusion and late gadolinium enhancement imaging.

PURPOSE: While both first-pass perfusion and late gadolinium enhancement by cardiovascular magnetic resonance (CMR) can assess coronary microvascular status in acute myocardial infarction (AMI), there are only limited data on their respective diagnostic utility. We aim to evaluate: the utility of first-pass perfusion and late gadolinium enhancement imaging in the detection and quantification of microvascular dysfunction after reperfused acute myocardial infarction, using TIMI frame count (TIMI FC) as the reference standard of microvascular assessment; and their relationship with infarct size and ventricular function. METHODS: First-pass perfusion and late gadolinium enhancement imaging were performed in 25 consecutive AMI patients (84% men, age 58 +/- 10) within 72 h of successful reperfusion. We assessed the myocardial extent of microvascular dysfunction using the size of the perfusion defect on first-pass perfusion (PD%) and the hypoenhanced core region within late gadolinium enhancement (MDEcore%). PD%, MDEcore%, and TIMI FC were analyzed independently of each other and with blinding to clinical data. We adjusted PD% and MDEcore% to the myocardial mass subtended by the infarct-related artery according to the 16-segment model. RESULTS: Median infarct size involved 13.9% (interquartile range: 8.5 to 22.2%) of the left ventricle and median left ventricular ejection fraction was 52% (interquartile range: 43 to 61%). PD% demonstrated evidence of microvascular dysfunction more frequently (84% vs. 36% of patients, p < 0.002) and involved a larger myocardial extent (23.5 +/- 17.5% vs. 3.5 +/- 7.7%, p < 0.001) compared to MDEcore%. PD% had strong correlations with TIMI FC (Spearman rho = 0.62, p < 0.001) and infarct size (rho = 0.64, p < 0.001), and a moderate correlation with LVEF (rho = -0.39, p = 0.055). MDEcore% also correlated with TIMI FC (rho = 0.54, p = 0.005) and infarct size (rho = 0.52, p < 0.01) but not with LVEF (p = NS). CONCLUSIONS: PD% appeared to provide a stronger noninvasive assessment of the microvascular function than MDEcore% and correlated well with prognostic markers such as left ventricular ejection fraction and infarct size. Future studies should consider quantitative analyses of both first-pass perfusion and late gadolinium enhancement imaging in the evaluation of novel therapies targeted to the microvasculature of the infarct-related artery.     

Detection of myocardial ischemia by stress perfusion cardiovascular magnetic resonance

With recent technical and clinical advances, adenosine stress perfusion MRI has evolved from a promising research tool to an everyday clinical test. This article reviews the current state of stress perfusion MRI. Specifically, it addresses the following topics: validation of stress perfusion MRI in preclinical studies, diagnostic performance in patients, imaging protocol, and image interpretation.     

Measurement of blood flow by nuclear magnetic resonance

PREVIEW

The epidemiologic factors of bacterial meningitis, a serious disease that must be addressed with great urgency, have evolved dramatically in the last 25 years. Among both adults and children, multidrug-resistant Streptococcus pneumoniae has emerged as a clinical challenge and has greatly complicated the empirical management of this disease. In this article, the author focuses on new issues involving the epidemiologic factors, diagnosis, treatment, and prevention of bacterial meningitis in adults.     

Transit of blood flow through the human left ventricle mapped by cardiovascular magnetic resonance.

BACKGROUND: The transit of blood through the beating heart is a basic aspect of cardiovascular physiology which remains incompletely studied. Quantification of the components of multidirectional flow in the normal left ventricle (LV) is lacking, making it difficult to put the changes observed with LV dysfunction and cardiac surgery into context. METHODS: Three dimensional, three directional, time resolved magnetic resonance phase-contrast velocity mapping was performed at 1.5 Tesla in 17 normal subjects, 6 female, aged 44+/-14 years (mean+/-SD). We visualized and measured the relative volumes of LV flow components and the diastolic changes in inflowing kinetic energy (KE). Of total diastolic inflow volume, 44+/-11% followed a direct, albeit curved route to systolic ejection (videos 1 and 2), in contrast to 11% in a subject with mildly dilated cardiomyopathy (DCM), who was included for preliminary comparison (video 3). In normals, 16+/-8% of the KE of inflow was conserved to the end of diastole, compared with 5% in the DCM patient. Blood following the direct route lost or transferred less of its KE during diastole than blood that was retained until the next beat (1.6+/-1.0 millijoules vs 8.2+/-1.9 millijoules, p<0.05); whereas, in the DCM patient, the reduction in KE of retained inflow was 18-fold greater than that of the blood tracing the direct route. CONCLUSION: Multidimensional flow mapping can measure the paths, compartmentalization and kinetic energy changes of blood flowing into the LV, demonstrating differences of KE loss between compartments, and potentially between the flows in normal and dilated left ventricles.