In-vivo T1 cardiovascular magnetic resonance study of diffuse myocardial fibrosis in hypertrophic cardiomyopathy

Background

In hypertrophic cardiomyopathy (HCM), autopsy studies revealed both increased focal and diffuse deposition of collagen fibers. Late gadolinium enhancement imaging (LGE) detects focal fibrosis, but is unable to depict interstitial fibrosis. We hypothesized that with T1 mapping, which is employed to determine the myocardial extracellular volume fraction (ECV), can detect diffuse interstitial fibrosis in HCM patients.

Methods

T1 mapping with a modified Look-Locker Inversion Recovery (MOLLI) pulse sequence was used to calculate ECV in manifest HCM (n = 16) patients and in healthy controls (n = 14). ECV was determined in areas where focal fibrosis was excluded with LGE.

Results

The total group of HCM patients showed no significant changes in mean ECV values with respect to controls (0.26 ± 0.03 vs 0.26 ± 0.02, p = 0.83). Besides, ECV in LGE positive HCM patients was comparable with LGE negative HCM patients (0.27 ± 0.03 vs 0.25 ± 0.03, p = 0.12).

Conclusions

This study showed that HCM patients have a similar ECV (e.g. interstitial fibrosis) in myocardium without LGE as healthy controls. Therefore, the additional clinical value of T1 mapping in HCM seems limited, but future larger studies are needed to establish the clinical and prognostic potential of this new technique within HCM.     

Diffuse myocardial fibrosis in hypertrophic cardiomyopathy can be identified by cardiovascular magnetic resonance,and is associated with left ventricular diastolic dysfunction

Background

The presence of myocardial fibrosis is associated with worse clinical outcomes in hypertrophic cardiomyopathy (HCM). Cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE) sequences can detect regional, but not diffuse myocardial fibrosis. Post-contrast T₁ mapping is an emerging CMR technique that may enable the non-invasive evaluation of diffuse myocardial fibrosis in HCM. The purpose of this study was to non-invasively detect and quantify diffuse myocardial fibrosis in HCM with CMR and examine its relationship to diastolic performance.

Methods

We performed CMR on 76 patients - 51 with asymmetric septal hypertrophy due to HCM and 25 healthy controls. Left ventricular (LV) morphology, function and distribution of regional myocardial fibrosis were evaluated with cine imaging and LGE. A CMR T₁ mapping sequence determined the post-contrast myocardial T₁ time as an index of diffuse myocardial fibrosis. Diastolic function was assessed by transthoracic echocardiography.

Results

Regional myocardial fibrosis was observed in 84% of the HCM group. Post-contrast myocardial T₁ time was significantly shorter in patients with HCM compared to controls, consistent with diffuse myocardial fibrosis (498 ± 80 ms vs. 561 ± 47 ms, p < 0.001). In HCM patients, post-contrast myocardial T₁ time correlated with mean E/e’ (r = −0.48, p < 0.001).

Conclusions

Patients with HCM have shorter post-contrast myocardial T₁ times, consistent with diffuse myocardial fibrosis, which correlate with estimated LV filling pressure, suggesting a mechanistic link between diffuse myocardial fibrosis and abnormal diastolic function in HCM.     

Quantitative diffusion-weighted magnetic resonance imaging in the assessment of myocardial fibrosis in hypertrophic cardiomyopathy compared with T1 mapping

To identify myocardial fibrosis in hypertrophic cardiomyopathy (HCM) subjects using quantitative cardiac diffusion-weighted imaging (DWI) and to compare its performance with native T1 mapping and extracellular volume (ECV). Thirty-eight HCM subjects (mean age, 53?±?9 years) and 14 normal controls (mean age, 51?±?8 years) underwent cardiac magnetic resonance imaging (CMRI) on a 3.0T magnetic resonance (MR) machine with DWI, T1 mapping and late gadolinium enhancement (LGE) imaging as the reference standard. The mean apparent diffusion coefficient (ADC), native T1 value and ECV were determined for each subject. Overall, the HCM subjects exhibited an increased native T1 value (1241.04?±?78.50 ms), ECV (0.31?±?0.03) and ADC (2.36?±?0.34 s/mm²) compared with the normal controls (1114.60?±?37.99 ms, 0.24?±?0.04, and 1.62?±?0.38 s/mm², respectively) (p?<?0.05). DWI differentiated healthy and fibrotic myocardia with an area under the curve (AUC) of 0.93, while the AUCs of the native T1 values (0.93), (p?>?0.05) and ECV (0.94), (p?>?0.05) exhibited an equal differentiation ability. Both HCM LGE+ and HCM LGE? subjects had an increased native T1 value, ECV and ADC compared to the normal controls (p?<?0.05). HCM LGE+ subjects exhibited an increased ECV (0.31?±?0.04) and ADC (2.43?±?0.36 s/mm²) compared to HCM LGE? subjects (p?<?0.05). HCM LGE+ and HCM LGE? subjects had similar native T1 values (1250?±?76.36 ms vs. 1213.98?±?92.30 ms, respectively) (p?>?0.05). ADC values were linearly associated with increased ECV (R²?=?0.36) and native T1 values (R²?=?0.40) among all subjects. DWI is a feasible alternative to native T1 mapping and ECV for the identification of myocardial fibrosis in patients with HCM. DWI and ECV can quantitatively characterize the extent of fibrosis in HCM LGE+ and HCM LGE? patients.     

Subclinical myocardial inflammation and diffuse fibrosis are common in systemic sclerosis – a clinical study using myocardial T1-mapping and extracellular volume quantification

Background

Systemic sclerosis (SSc) is characterised by multi-organ tissue fibrosis including the myocardium. Diffuse myocardial fibrosis can be detected non-invasively by T1 and extracellular volume (ECV) quantification, while focal myocardial inflammation and fibrosis may be detected by T2-weighted and late gadolinium enhancement (LGE), respectively, using cardiovascular magnetic resonance (CMR). We hypothesised that multiparametric CMR can detect subclinical myocardial involvement in patients with SSc.

Methods

19 SSc patients (18 female, mean age 55 ± 10 years) and 20 controls (19 female, mean age 56 ± 8 years) without overt cardiovascular disease underwent CMR at 1.5T, including cine, tagging, T1-mapping, T2-weighted, LGE imaging and ECV quantification.

Results

Focal fibrosis on LGE was found in 10 SSc patients (53%) but none of controls. SSc patients also had areas of myocardial oedema on T2-weighted imaging (median 13 vs. 0% in controls). SSc patients had significantly higher native myocardial T1 values (1007 ± 29 vs. 958 ± 20 ms, p < 0.001), larger areas of myocardial involvement by native T1 >990 ms (median 52 vs. 3% in controls) and expansion of ECV (35.4 ± 4.8 vs. 27.6 ± 2.5%, p < 0.001), likely representing a combination of low-grade inflammation and diffuse myocardial fibrosis. Regardless of any regional fibrosis, native T1 and ECV were significantly elevated in SSc and correlated with disease activity and severity. Although biventricular size and global function were preserved, there was impairment in the peak systolic circumferential strain (-16.8 ± 1.6 vs. -18.6 ± 1.0, p < 0.001) and peak diastolic strain rate (83 ± 26 vs. 114 ± 16 s-1, p < 0.001) in SSc, which inversely correlated with diffuse myocardial fibrosis indices.

Conclusions

Cardiac involvement is common in SSc even in the absence of cardiac symptoms, and includes chronic myocardial inflammation as well as focal and diffuse myocardial fibrosis. Myocardial abnormalities detected on CMR were associated with impaired strain parameters, as well as disease activity and severity in SSc patients. CMR may be useful in future in the study of treatments aimed at preventing or reducing adverse myocardial processes in SSc.     

Quantitative analysis of late gadolinium enhancement in hypertrophic cardiomyopathy

Background

Cardiovascular Magnetic resonance (CMR) with the late gadolinium enhancement (LGE) technique allows the detection of myocardial fibrosis in Hypertrophic cardiomyopathy (HCM). The aim of this study was to compare different methods of automatic quantification of LGE in HCM patients. Methods: Forty HCM patients (mean age 48 y, 30 males) and 20 normal subjects (mean age 38 y, 16 males) underwent CMR, and we compared 3 methods of quantification of LGE: 1) in the SD2 method a region of interest (ROI) was placed within the normal myocardium and enhanced myocardium was considered as having signal intensity >2 SD above the mean of ROI; 2) in the SD6 method enhanced myocardium was defined with a cut-off of 6 SD above mean of ROI; 3) in the RC method a ROI was placed in the background of image, a Rayleigh curve was created using the SD of that ROI and used as ideal curve of distribution of signal intensity of a perfectly nulled myocardium. The maximal signal intensity found in the Rayleigh curve was used as cut-off for enhanced myocardium. Parametric images depicting non enhanced and enhanced myocardium was created using each method. Three investigators assigned a score to each method by the comparison of the original LGE image to the respective parametric map generated.

Results

Patients with HCM had lower concordance between the measured curve of distribution of signal intensity and the Rayleigh curve than controls (63.7 ± 12.3% vs 92.2 ± 2.3%, p < 0.0001).A cut off of concordance < 82.9% had a 97.1% sensitivity and 92.3% specificity to distinguish HCM from controls. The RC method had higher score than the other methods. The average extent of enhanced myocardium measured by SD6 and Rayleigh curve method was not significant different but SD6 method showed underestimation of enhancement in 12% and overestimation in 5% of patients with HCM.

Conclusions

Quantification of fibrosis in LGE images with a cut-off derived from the Rayleigh curve is more accurate than using a fixed cut-off.     

Assessment of left ventricular twist mechanics by speckle tracking echocardiography reveals association between LV twist and myocardial fibrosis in patients with hypertrophic cardiomyopathy

We aimed to investigate whether left ventricular (LV) twist analysis can detect the extent of myocardial fibrosis in patients with hypertrophic cardiomyopathy (HCM). This prospective case–control study recruited 81 consecutive patients with HCM examined between January 2012 and April 2013. Data of 76 patients were analyzed after excluding 5 patients whose echocardiographic images were of poor quality. Healthy volunteers (n = 46) served as controls. Both groups underwent comprehensive echocardiographic examination (i.e., Bas-Rotation, AP-Rotation, LVEF, LADs, IVST, LAVi, E/Em, LVMI, advanced LV-twist analysis by speckle tracking echocardiography) and magnetic resonance imaging. Between-group differences were analyzed by independent t test; logistic regression analysis was performed to identify effect factors. No significant differences were found between baseline characteristics of HCM and control groups (all p > 0.05). HCM patients had significantly higher Bas-Rotation, AP-Rotation, LV Twist, LVEF, LADs, IVST, LAVi, E/Em and LVMI than controls (all p < 0.0001) and significantly lower LVDd and E/A (both p < 0.001). Bas-Rotation, AP-Rotation, LV-Twist, LADs, IVST, LAVi, E/Em and LVMI were significantly higher in HCM patients with fibrosis than in those without fibrosis (p < 0.001), but no significant differences in other echocardiographic parameters were found between those with and without fibrosis. Age, Bas-Rotation, AP-Rotation, LV twist, LADs, IVST, LAVi, E/A, E/Em, and LVMI were significant effect factors for fibrosis. AUROC analysis showed that LV twist had high discriminatory power to detect extent of myocardial fibrosis (AUC 0.996, 95 % CI 0.989–1.004, p < 0.001). Left ventricular twist mechanics are associated with the extent of myocardial fibrosis. LV-twist assessment by STE may be clinically useful.     

Myocardial fibrosis and quality of life in patients with non-ischemic cardiomyopathy: a cardiovascular magnetic resonance imaging study

Myocardial fibrosis (MF) is a common pathophysiologic endpoint in non-ischemic cardiomyopathy and may be identified by Late Gadolinium Enhancement (LGE) MRI. While associated with future cardiovascular events in Hypertrophic Cardiomyopathy (HCM) and Dilated Cardiomyopathy (DCM) the influence of MF on interim quality of life (QOL) has not been explored. In this study we investigate for associations between MF and validated indices of QOL in patients with HCM and DCM. Ninety-eight patients with known cardiomyopathy (n = 56-HCM/n = 42-DCM) underwent LGE-MRI in addition to standardized testing for QOL using the disease-specific Minnesota Living With Heart Failure (MLWHF) and the generic SF-12 questionnaires. LGE-MRI images were blindly analyzed for the presence and volume of MF using validated techniques. All analyses were stratified according to cardiomyopathy sub-type. The mean age of the population was 56.8 ± 12.9 years. MF was identified in 82 % of patients with HCM and 74 % of patients with DCM with respective mean MF burdens of 20.0 and 13.7 % of the left ventricular mass (p = 0.008). QOL scores for those with HCM or DCM, as assessed by both MLWHF and SF-12, were not significantly different between those with versus those without MF, and showed no association with MF burden by quantitative signal analysis. In this study we identified no association between QOL and MF burden by LGE-MRI in patients with HCM or DCM. Therefore, the severity of underlying myocardial tissue disease, a recognized substrate for ventricular arrhythmia, cannot and should not be inferred from the patient’s symptom status or QOL.     

Serum carnitine concentrations in patients with idiopathic hypertrophic cardiomyopathy: relationship with impaired myocardial fatty acid metabolism.

We evaluated the clinical significance of serum carnitine concentrations in determining the severity of impaired myocardial fatty acid metabolism in idiopathic hypertrophic cardiomyopathy (HCM). We studied 56 asymptomatic or mildly symptomatic patients with HCM. Serum levels of free carnitine and acylcarnitine were measured by the enzymic cycling method. Myocardial scintigraphy with (123)I-labelled 15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid (BMIPP) was performed, and the images were analysed quantitatively and semi-quantitatively. Serum free carnitine levels were significantly higher in HCM patients than in normal subjects (52. 5+/-9.5 and 42.3+/-5.5 nmol/ml respectively; P<0.0001). On the other hand, serum acylcarnitine levels and acyl/free carnitine ratios were lower in HCM patients than in normal subjects (10.2+/-4.0 nmol/ml and 0.19+/-0.08, compared with 13.2+/-3.9 nmol/ml and 0.32+/-0.11 respectively; P<0.0001). Clinical characteristics were not significantly different between the patients showing high and normal free carnitine levels, although female patients with high free carnitine levels were few (P=0.02). Both quantitative and semi-quantitative analyses revealed that the severity of decreased myocardial BMIPP uptake was significantly correlated with serum free carnitine levels (quantitative analysis: r=-0.422, P<0.0012; semi-quantitative analysis: r=0.633, P<0.0001). In the presence of reduced carnitine uptake into the myocardium in HCM, there may also be reduced transport of acylcarnitines out of the myocardium into the plasma. Although inborn errors of fatty acid metabolism and carnitine deficiencies are reported to provoke secondary HCM and are associated with low serum carnitine concentrations, this study has revealed that the levels of carnitine are, in contrast, increased in idiopathic HCM. Moreover, serum carnitine concentrations are a sensitive indicator of the severity of impaired myocardial fatty acid metabolism even in asymptomatic patients with HCM.     

3.0T心脏磁共振对肥厚性心肌病心肌纤维化与心肌损伤标志物的关系研究

目的运用3.0 T心脏磁共振(CMR)延迟强化(LGE)技术对肥厚性心肌病(HCM)心肌纤维化进行定量检测,并获得LGE与心肌标志物即心肌代谢酶的关系,从而探究HCM患者心肌标志物升高是否与心肌纤维化造成的心肌细胞损伤有关。方法纳入34例HCM患者(HCM组)与20例健康志愿者(正常对照组)。两组均行3.0 T CMR扫描,包括短轴位心脏电影及LGE序列。心脏功能用短轴为心脏电影序列测定;运用LGE序列测定HCM与正常对照组的LGE参数,包括总LGE率、LGE体积及LGE质量;测定与心肌损伤程度有关的血清心肌标志物含量,包括肌酸激酶同工酶、肌钙蛋白。采用独立样本t检验及Pearson积矩相关对心肌标志物及LGE参数进行统计分析。结果 HCM组肌酸激酶同工酶、肌钙蛋白均大于临床正常范围。通过LGE检测,HCM组的LGE参数,包括总LGE率、LGE体积及LGE质量均大于正常对照组[分别为(18.95±9.87)%vs.(50.82±14.18)%、(8.50±4.50)ml vs.(86.26±41.99)ml及(9.00±4.80)g vs.(90.58±44.11)g,均P<0.05]。Pearson积矩相关证明,HCM组肌酸激酶同工酶与总LGE率、LGE体积呈正相关(r值分别为0.759、0.448,P值分别为0.000、0.008)。肌钙蛋白与总LGE率、LGE体积呈正相关(r值分别为0.647、0.578,P值均为0.000)。结论 3.0 T CMR LGE技术可用于肥厚性心肌病心肌纤维化的定量检测,HCM患者心肌标志物与心肌的LGE率呈正相关,表明心肌纤维化造成的心肌细胞损伤可能导致心肌细胞内的代谢酶类即心肌标志物释放,从而影响心肌的代谢功能,最终造成心脏功能损伤。     

Cardiovascular Magnetic Resonance Imaging of Myocardial Interstitial Expansion in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a cardiovascular genetic disease with a varied clinical presentation and phenotype. Although mutations are typically found in genes coding for sarcomeric proteins, phenotypic derangements extend beyond the myocyte to include the extracellular compartment. Myocardial fibrosis is commonly detected by histology, and is associated with clinical vulnerability to adverse outcomes. Over the past decade, the noninvasive visualization of myocardial fibrosis by cardiovascular magnetic resonance (CMR) techniques has garnered much interest given the potential applications toward improving our understanding of pathophysiologic mechanisms of disease, as well as diagnosis and prognosis. Late gadolinium enhancement (LGE) imaging techniques are able to detect focal (typically replacement) fibrosis. Newer CMR techniques that measure absolute T1 relaxation time allow the quantification of the entire range of focal to diffuse (interstitial) fibrosis and may overcome potential limitations of LGE. This review will discuss the methodology and current status of these novel techniques, with a focus on extracellular volume fraction (ECV). Recent findings describing ECV measurement in HCM will be summarized.     

Diagnostic value of routine clinical parameters in acute myocardial infarction: a comparison to delayed contrast enhanced magnetic resonance imaging

Aims: Contrast enhanced magnetic resonance imaging (ceMRI) has been shown to reliably identify irreversible myocardial injury. The aim of this study was to compare the findings on ceMRI with routine clinical markers of myocardial injury in patients with acute myocardial infarction (MI). Methods and results: Twenty-four patients with acute MI were investigated at 1.5 T. The global myocardial function was analysed with a standard cine MR protocol and a stack of short axis slices encompassing the entire left ventricle. Corresponding short axis slices were acquired for delayed ceMRI 15–20 min after the administration of 0.2 mmol gadolinium–DTPA/kg body weight. Mass of hyperenhancement and peak creatine kinase release (peak CK) was determined for each patient. The presenting 12-lead ECG was analysed for ST-elevation on admission and later development of Q-waves. Mass of hyperenhancement correlated moderately well to peak CK (r = 0.65, p < 0.01) and endsystolic volume index (r = 0.55, p < 0.01). Mass of hyperenhancement was inversely correlated to ejection fraction (r = ?0.50, p = 0.02). Neither the presence of ST elevation on the admission ECG nor the later development of Q-waves did relate to the transmural extent of hyperenhancement and to the mass of hyperenhancement. Conclusion: Mass of hyperenhancement significantly correlates to global myocardial function and to peak CK. However, there is no relationship between the findings in ceMRI and 12-lead ECG abnormalities on admission suggesting an advantage of ceMRI in defining transmural extent and depicting small areas of necrosis.     

Gadolinium-enhanced magnetic resonance imaging for detection and quantification of fibrosis in human myocardium in vitro

Background The availability of a non-invasive test to detect and quantify interstitial and replacement fibrosis would be a useful advance for evaluation of cardiac therapies that could prevent fibrosis progression. There is an established role for magnetic resonance imaging (MRI) in the assessment of replacement fibrosis (when fibrosis replaces myocytes), but the potential for assessment of interstitial fibrosis (when amount of fibrosis increases between myocytes) has not been evaluated. Methods A novel in vitro MRI technique was developed for comparison of gadodiamide contrast distribution volume as a measure of both kinds of myocardial fibrosis, with histologically determined myocardial collagen volume fraction, the current gold standard for quantification of myocardial fibrosis. Eight samples of human myocardium were obtained postmortem and a fast spin-echo sequence (3 Tesla) with non-slice selective inversion pulse performed before and after immersion in a gadodiamide saline solution for determination of the gadodiamide partition coefficient. T1 values were calculated from the inversion recovery signal curves. The same samples were fixed in formalin, and collagen volume fraction was determined by the picrosirius red method using a semi-automated, polarized, digital microscopy system. Results Both gadodiamide distribution volumes as well as CVF values were significantly different in normal myocardium versus interstitial fibrosis (P = 0.001), and normal versus replacement fibrosis (P = 0.015). Moreover, there was a significant positive correlation between the two methods, across all three histological categories of myocardial fibrosis (r = 0.73; P = 0.017). Conclusion These findings indicate an expanded potential for gadodiamide enhanced MRI as a novel, non-invasive alternative to histological evaluation, for the quantification of both interstitial and replacement myocardial fibrosis.     

定量组织速度成像对肥厚型心肌病患者左心室局部收缩功能的研究

目的　应用定量组织速度成像 (QTVI)评价肥厚型心肌病 (HCM)患者左心室局部收缩功能。方法　应用QTVI离线分析 3 1例HCM患者和 2 0例正常对照者左室长轴和短轴方向各心肌节段的速度曲线 ,测量收缩期峰值速度 (Vs) ,计算左室后壁和室间隔各心肌节段在长轴与短轴方向速度的比值。结果　HCM组肥厚与非肥厚心肌节段的平均Vs降低 ,与对照组相比 ,绝大部分心肌节段差异有显著性意义 (P<0 .0 5) ,但HCM组肥厚与非肥厚心肌节段的平均Vs之间差异无显著性意义 (P >0 .0 5)。正常人长轴与短轴方向速度的比值均 >1,而HCM患者其比值明显降低 ,大部分比值 <1。结论　HCM患者尽管左室射血分数正常 ,但左室长轴方向各心肌节段收缩功能受损 ,损害不仅发生在肥厚的左室壁 ,非肥厚的室壁同样受到损害 ;QTVI能定量评价HCM患者左室局部收缩功能     

Relationship of basal-septal fibrosis with LV outflow tract obstruction in hypertrophic cardiomyopathy: insights from cardiac magnetic resonance analysis

Myocardial fibrosis is frequently observed and may be associated with the prognosis in patients with hypertrophic cardiomyopathy (HCM); however, the clinical pathophysiological features, particularly in terms of fibrosis, of hypertrophic obstructive cardiomyopathy (HOCM) remain unclear. This study aimed to determine a role of local fibrosis in HOCM using cardiac magnetic resonance (CMR). 108 consecutive HCM patients underwent CMR. HOCM was defined as a left ventricular outflow tract (LVOT) pressure gradient ≥30 mmHg at rest. Myocardial mass and fibrosis mass by late gadolinium-enhancement CMR (LGE-CMR) were calculated and the distribution/pattern was analyzed using the AHA 17-segment model. LV ejection fraction (LVEF) was significantly higher in patients with HOCM (n = 19) than in those with nonobstructive HCM (n = 89) (P < 0.05). Both total myocardial and fibrosis masses in LV were similar in the two groups (P = 0.385 and P = 0.859, respectively). However, fibrosis in the basal septum was significantly less frequent in the HOCM group than in the nonobstructive HCM group (P < 0.01). The LVOT pressure gradient was significantly higher in the basal-septal non-fibrosis group than in the fibrosis group (23.6 ± 37.3 vs. 4.8 ± 11.4 mmHg, P < 0.01). Multivariate analysis revealed that basal-septal fibrosis was an independent negative predictor of LVOT obstruction in addition to the local wall thickness and LVEF as positive predictors in HCM patients. In conclusion, a significant association was observed between LVOT obstruction and basal septal fibrosis by LGE-CMR in HCM patients. In addition to negative impact of basal-septal fibrosis, basal-septal hypertrophy and preserved global LV contractility may be associated with the pathophysiological features of LVOT obstruction.     

Clinical Utility of Cardiovascular Magnetic Resonance in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is characterized by substantial genetic and phenotypic heterogeneity, leading to considerable diversity in clinical course including the most common cause of sudden death in young people and a determinant of heart failure symptoms in patients of any age. Traditionally, two-dimensional echocardiography has been the most reliable method for establishing a clinical diagnosis of HCM. However, cardiovascular magnetic resonance (CMR), with its high spatial resolution and tomographic imaging capability, has emerged as a technique particularly well suited to characterize the diverse phenotypic expression of this complex disease. For example, CMR is often superior to echocardiography for HCM diagnosis, by identifying areas of segmental hypertrophy (ie., anterolateral wall or apex) not reliably visualized by echocardiography (or underestimated in terms of extent). High-risk HCM patient subgroups identified with CMR include those with thin-walled scarred LV apical aneurysms (which prior to CMR imaging in HCM remained largely undetected), end-stage systolic dysfunction, and massive LV hypertrophy. CMR observations also suggest that the cardiomyopathic process in HCM is more diffuse than previously regarded, extending beyond the LV myocardium to include thickening of the right ventricular wall as well as substantial morphologic diversity with regard to papillary muscles and mitral valve. These findings have implications for management strategies in patients undergoing invasive septal reduction therapy. Among HCM family members, CMR has identified unique phenotypic markers of affected genetic status in the absence of LV hypertrophy including: myocardial crypts, elongated mitral valve leaflets and late gadolinium enhancement. The unique capability of contrast-enhanced CMR with late gadolinium enhancement to identify myocardial fibrosis has raised the expectation that this may represent a novel marker, which may enhance risk stratification. At this time, late gadolinium enhancement appears to be an important determinant of adverse LV remodeling associated with systolic dysfunction. However, the predictive significance of LGE for sudden death is incompletely resolved and ultimately future large prospective studies may provide greater insights into this issue. These observations underscore an important role for CMR in the contemporary assessment of patients with HCM, providing important information impacting diagnosis and clinical management strategies.     

Optimal timing for first-pass stress CT myocardial perfusion imaging

CT-based myocardial perfusion imaging (CTP) has been shown to accurately detect myocardial perfusion defects when compared to SPECT. When performing single-phase first-pass stress CTP, timing is of major importance. The aim of this study was to provide guidance for optimal timing of single-phase first-pass stress CTP acquisitions. 16 patients (12 male, age, 69 ± 8 years) with known or suspected coronary artery disease underwent invasive coronary angiography with fractional flow reserve (FFR) measurements using a pressure wire as well as a time-resolved CTP protocol under adenosine stress, performed on a dual-Source CT scanner over a period of 30 s. From the CTP data, time-attenuation curves have been determined both in known ischemic myocardium with a corresponding coronary artery stenosis as proven by a FFR below 0.75 in invasive coronary angiography, as well as in non-ischemic reference myocardium during pharmacological stress. Furthermore, contrast enhancement in the ascending aorta was determined. The time point for an optimal contrast (i.e., difference in Hounsfield Units, HU) between ischemic and normal myocardium was determined. Under pharmacological stress using adenosine, a maximum mean HU difference between ischemic and non-ischemic myocardium (17.7–22.5 HU) was observed 24–32 s after injection of contrast medium. The maximal attenuation difference between normal and ischemic myocardium ranged from 15 to 77 HU in the analyzed patient cohort. When applying a bolus-tracking technique with an automatic contrast detection in the proximal ascending aorta, the optimal time frame for stress CTP was between 8 and 16 s after contrast enhancement in the aorta exceeds 100 HU, or between 7 and 15 s using a threshold of 150 HU. For first-pass CT myocardial perfusion imaging there is a time frame of approximately 8 s for optimal differentiation of ischemic and non-ischemic myocardium, which will be helpful to optimize single-phase CTP scans.     

Frequency and distribution of late gadolinium enhancement in magnetic resonance imaging of patients with apical hypertrophic cardiomyopathy and patients with asymmetrical hypertrophic cardiomyopathy: a comparative study

Our aim was to compare the frequency and distribution of late gadolinium enhancement (LGE) on contrast MRI between hypertrophic cardiomyopathy (HCM) patients with apical hypertrophic cardiomyopathy (APH) and those with asymmetrical septal hypertrophy (ASH). We studied 66 patients with HCM (50 men and 16 women; average age: 58.8 ± 29.8 years) who had undergone MRI. All the MRI examinations were performed using a 1.5 T system. LGE images were acquired using the inversion recovery segmented spoiled-gradient echo and phase-sensitive inversion recovery methods. We evaluated 17 segments of the left ventricle as defined by the American Heart Association criteria for LGE determination. LGE was detected at the junction of the right ventricle and the interventricular septum in 25 (73.5%) of the 34 HCM patients with ASH and in the apex of the heart in 13 (40.6%) of the 32 patients with APH. LGE-positive areas were more widely distributed in the case of the ASH group than in the case of the APH group. The distribution of LGE was clearly different between the two groups (Fisher’s exact probability test, P = 0.0068). The number of LGE-positive cases and LGE-positive segments were significantly higher in the ASH group than in the APH group and there was a significant difference in the distribution of the LGE-positive areas between the two groups. LGE was mainly detected in the hypertrophied areas of the myocardium.     

定量组织速度成像对肥厚型心肌病左心室局部心肌舒张功能的分析

目的探讨定量组织速度成像（QTVI）评价肥厚型心肌病（HCM）患者左室局部心肌舒张功能的价值。方法获标准心尖长轴切面、心尖二腔切面和心尖四腔切面，应用QTVI技术分析17例HCM患者和18例健康者左室长轴方向不同室壁节段的多普勒速度曲线，测量各节段心肌运动舒张早期峰值速度（Ve）和舒张晚期峰值速度（Va），计算左室二尖瓣环、基底段、中段水平的平均Ve、平均Va。应用脉冲多普勒技术分别测量二尖瓣口舒张早期峰值速率（E）、舒张晚期速率（A）、计算E／A。结果HCM组左室各节段Ve明显低于正常组（大部分P〈0．001），肥厚节段Va低于正常组（P〈0．05），而非肥厚节段Va两组间差异无显著性意义（P〉0．05）。两组同一水平平均Ve、Va的比较均有显著性意义（P〈0．05）。HCM组与正常组二尖瓣口E、A、E／A差异无显著性意义（P〉0．05）。结论QTVI能定量评价HCM患者左室局部心肌舒张功能。HCM患者左室长轴各节段心肌松弛性显著降低，肥厚节段的心肌顺应性受损。     

Effects of hypertrophy and fibrosis on regional and global functional heterogeneity in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a disease that typically has heterogeneous hypertrophy and dysfunction of the myocardium. Cardiac magnetic resonance imaging (CMR) can be used to accurately assess ventricular wall thickness and regional fibrosis. We investigated the effects of hypertrophy and fibrosis on the heterogeneity of regional and global myocardial function in HCM. Forty patients who were diagnosed with HCM were consecutively enrolled. Echocardiography and CMR with delayed hyper-enhancement imaging (DHE) was performed for each patient. Left ventricular (LV) regional and global longitudinal strain (SL_R and SL_G) were obtained by two-dimensional speckle tracking method on echocardiography. With CMR, regional myocardial wall thickness was measured, and the amount of DHE was calculated semi-quantitatively in each segment. Overall, 720 segments were analyzed. SL_R was significantly decreased in the hypertrophied segments (thickness > 11 mm) and segments with DHE (P < 0.001). SL_R was correlated with myocardial wall thickness (r = 0.47, P = 0.001) and amount of regional DHE (r = 0.39, P < 0.001). On multivariate analysis, regional LV wall thickness and amount of DHE were the only independent determinants of SL_R. SL_G was associated with LV diastolic functional parameters in echocardiography, total DHE volume, and LV mass index. Total DHE volume and LV mass index were independent determinants of SL_G on multivariate analysis. The extent of regional myocardial fibrosis is associated with regional myocardial function independently of morphological changes of the myocardium, and the correlation extended to global LV function. In this context, DHE may be a useful parameter to discover early myocardial dysfunction independently of LV hypertrophy.     

应变成像技术对肥厚型心肌病患者和正常人心功能的评价

目的 应用应变成像技术对肥厚型心肌病患者和正常人的心功能进行研究。方法 采集肥厚型心肌病患者20例和正常对照者22例的动态组织多普勒图像后，分别测量其不同心肌节段的最大应变值，对两组结果进行分析比较。结果 正常组应变值在各个心肌节段基本保持一致；而在肥厚型心肌病组，室间隔、左室前壁和下壁各节段心肌的应变值显著低于正常组。结论 应变成像技术可准确地检出肥厚型心肌病患者局部心肌收缩功能的异常，为准确、定量地评价局域心肌功能提供了新的参数。