Quantification Of Extracellular Volume Fraction Research Articles

489 Intermodality Comparison Of Myocardial Extracellular Volume Fraction Assessment In Patients With Severe Aortic Stenosis Undergoing TAVR Evaluation

Introduction: Assessment of diffuse myocardial fibrosis is possible by cardiovascular magnetic resonance imaging with the quantification of extracellular volume fraction (ECV-CMR). ECV can also be determined by computed tomography angiography (ECV-CTA), using pre- and post-contrast images that are easily incorporated into the standard pre-procedural CTA for planning transcatheter aortic valve replacement (TAVR). There is limited data comparing ECV-CTA to ECV-CMR in this population.

Myocardial extracellular volume quantification by computed tomography predicts outcomes in patients with severe aortic stenosis.

The extent of myocardial fibrosis in patients with severe aortic stenosis might have an important prognostic value. Non-invasive imaging to quantify myocardial fibrosis by measuring extracellular volume fraction might have an important clinical utility prior to aortic valve intervention. Seventy-five consecutive patients with severe aortic stenosis, and 19 normal subjects were prospectively recruited and underwent pre- and post-contrast computed tomography for estimating myocardial extracellular volume fraction. Serum level of galectin-3 was measured and 2-dimensional echocardiography was performed to characterize the extent of cardiac damage using a recently published aortic stenosis staging classification. Extracellular volume fraction was higher in patients with aortic stenosis compared to normal subjects (40.0±11% vs. 21.6±5.6%; respectively, p<0.001). In patients with aortic stenosis, extracellular volume fraction correlated with markers of left ventricular decompensation including New York Heart Association functional class, left atrial volume, staging classification of aortic stenosis and lower left ventricular ejection fraction. Out of 75 patients in the AS group, 49 underwent TAVI, 6 surgical AVR, 2 balloon valvuloplasty, and 18 did not undergo any type of intervention. At 12-months after aortic valve intervention, extracellular volume fraction predicted the combined outcomes of stroke and hospitalization for heart failure with an area under the curve of 0.77 (95% confidence interval: 0.65-0.88). A trend for correlation between serum galectin-3 and extracellular volume was noted. In patients with severe aortic stenosis undergoing computed tomography before aortic valve intervention, quantification of extracellular volume fraction correlated with functional status and markers of left ventricular decompensation, and predicted the 12-months composite adverse clinical outcomes. Implementation of this novel technique might aid in the risk stratification process before aortic valve interventions.

Quantification of extracellular volume fraction by cardiac computed tomography for noninvasive assessment of myocardial fibrosis in hemodialysis patients

Extent of myocardial fibrosis in hemodialysis patients has been associated with poor prognosis. Myocardial extracellular volume (ECV) quantification using contrast enhanced cardiac computed tomography (CT) is a novel method to determine extent of myocardial fibrosis. Cardiac CT-based myocardial ECV in hemodialysis patients with those of propensity-matched non-hemodialysis control subjects were compared. Twenty hemodialysis patients (mean age, 67.4 ± 9.6 years; 80% male) and 20 propensity-matched non-hemodialysis controls (mean age, 66.3 ± 9.1 years; 85% male) who underwent comprehensive cardiac CT consisted of calcium scoring, coronary CT angiography, stress perfusion CT and delayed enhancement CT were evaluated. Myocardial ECV was significantly greater in the hemodialysis group than in the control group (33.8 ± 4.7% versus 26.6 ± 2.9%; P < 0.0001). In the hemodialysis group, modest correlation was evident between myocardial ECV and left atrial volume index (r = 0.54; P = 0.01), while there was no correlation between myocardial ECV and other cardiac parameters including left ventricular mass index and severity of myocardial ischemia. Cardiac CT-based myocardial ECV may offer a potential imaging biomarker for myocardial fibrosis in HD patients.

Myocardial tissue characterization by gadolinium-enhanced cardiac magnetic resonance imaging for risk stratification of adverse events in hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is a genetic cardiomyopathy with a wide spectrum of clinical manifestations. Patients can be asymptomatic or suffer major adverse events including sudden cardiac death, ventricular arrhythmias, and heart failure. Identification of individuals with HCM who are at risk for these complications remains challenging. While echocardiography remains the mainstay of diagnostic evaluation, cardiac magnetic resonance imaging (CMR) is an important adjunctive diagnostic modality with emerging applications for risk-stratification of adverse events in the HCM population. Although not included in current guidelines for HCM management, there is increasing evidence to support the use of CMR for routine prognostic assessment of HCM patients. In this review we discuss the use of CMR techniques, including late gadolinium enhancement, T1 mapping, and quantification of extracellular volume fraction, for the risk stratification of three major adverse events in HCM: sudden cardiac death, ventricular arrhythmias, and congestive heart failure.

Automatic quantification of the myocardial extracellular volume by cardiac computed tomography: Synthetic ECV by CCT

BackgroundThe quantification of extracellular volume fraction (ECV) by Cardiac Computed Tomography (CCT) can identify changes in the myocardial interstitium due to fibrosis or infiltration. Current methodologies require laboratory blood hematocrit (Hct) measurement – which complicates the technique. The attenuation of blood (HUblood) is known to change with anemia. We hypothesized that the relationship between Hct and HUblood could be calibrated to rapidly generate a synthetic ECV without formally measuring Hct. MethodsThe association between Hct and HUblood was derived from forty non-contrast thoracic CT scans using regression analysis. Synthetic Hct was then used to calculate synthetic ECV, and in turn compared with ECV using blood Hct in a validation cohort with mild interstitial expansion due to fibrosis (aortic stenosis, n = 28, ECVCT = 28 ± 4%) and severe interstitial expansion due to amyloidosis (n = 27; ECVCT = 54 ± 11%, p < 0.001). For histological validation, synthetic ECV was correlated with collagen volume fraction (CVF) in a separate cohort with aortic stenosis (n = 18). All CT scans were performed at 120 kV and 160 mAs. ResultsHUblood was a good predictor of Hct (R2 = 0.47; p < 0.01), with the regression model (Hct = [0.51 * HUblood] + 17.4) describing the association. Synthetic ECV correlated well with conventional ECV (R2 = 0.96; p < 0.01) with minimal bias and 2SD difference of 5.7%. Synthetic ECV correlated as well as conventional ECV with histological CVF (both R2 = 0.50, p < 0.01). Finally, we implemented an automatic ECV plug-in for offline analysis. ConclusionSynthetic ECV by CCT provides instantaneous quantification of the myocardial extracellular space without the need for blood sampling.

A novel calibration technique to obtain high resolution 3D T1 Maps for Infarct characterization

Background Myocardial T1 mapping enables quantification of extracellular volume fraction (ECV), which correlates with myocardial fibrosis and is predictive of adverse cardiac events. Quantitative T1 mapping is highly useful in detecting scar tissue in patients with prior myocardial infarctions or those with other cardiomyopathies. The Modified Look-Locker inversion recovery (MOLLI) sequence is a clinical standard for T1 mapping, however it is limited by low spatial resolution which prevents it from being used for infarct characterization. In this study, a novel technique to convert high resolution 3D phase sensitive inversion recovery (3D-PSIR) images into high resolution T1 maps by calibration with lowresolution MOLLI T1 maps. Methods From a phantom study using 11 agarose vials doped with different concentrations of Ni, an exponential relationship was derived between signal intensity and T1 using a 3D-PSIR segmented Turbo FLASH and MOLLI acquisition, respectively. 9 canines with chronic infarcts (ranging from 12-14 weeks) were scanned on a 1.5 T Siemens Avanto scanner. A 3D-PSIR (covering the entire left ventricle) and a single long axis MOLLI were collected prior to contrast injection and 15-20 minutes after contrast injection (Gd-DTPA). The MOLLI and 3D-PSIR images had resolutions of approximately isotropic in-plane 1.3-1.4 mm × 8.0 mm and 1.4 × 1.4 × 1.4 mm, respectively. Six regions of interest (3 in the myocardium, 2 in the blood pool, and 1 in the liver) were drawn in the MOLLI image

Quantification of myocardial extracellular volume fraction by cardiac magnetic resonance for early detection of the left ventricle involvement in systemic sclerosis

Cardiologia CROATICA Background: Early identification of myocardial dysfunction is challenging for many cardiovascular diseases and systemic sclerosis (SSc) is an unique model of progressive myocardial fibrosis. Cardiac magnetic resonance with late gadolinium enhancement (LGE) can detect fibrosis in advanced stages of SSc, but is limited in the early stage due to the diffuse nature of fibrotic changes. T1 mapping is able to quantify myocardial fibrosis and can be used to quantify myocardial extracellular volume fraction (EVF), which changes when collagen content increases. We aimed to determine whether EVF quantification could detect subclinical left ventricular (LV) abnormalities and to investigate the relationship between EVF and subtle diastolic and systolic dysfunction. Materials and Methods: T1 mapping and EVF quantification were prospectively performed in 33 consecutive SSc patients with normal echocardiography, no severe diastolic dysfunction, no pulmonary hypertension at rest and no LGE, as well as in 16 healthy controls. The study was approved by the local ethics committee and all subjects gave written informed consent. Results: SSc patients had significantly higher global EVF (P<0.0001) and higher local EVF for all basal and mid-ventricular LV segments (P<0.01). Global EVF significantly correlated with left atrial volume (P<0.0001) and with the grade of diastolic dysfunction (P=0.016). Majority of SSc patients (63%) had both a high global EVF and low global systolic circumferential strain. Conclusions: EVF quantification can identify LV abnormalities at an early stage in SSc patients. These abnormalities may reflect increase in diffuse myocardial fibrosis and are associated with subtle diastolic and systolic LV dysfunction.

Kardiomyopathien und Myokarditis

Cardiomyopathies and myocarditis are frequently challenging in clinical practice regarding differentiation, risk stratification and treatment strategy. There are various disease entities which often affect young or middle-aged adults and the course is variable from asymptomatic and irrelevant for prognosis to sudden cardiac death or severe heart failure even at an early age. Making the right diagnosis is therefore fundamental to correctly identify affected patients and to initiate treatment steps in time. Whereas causal treatment options exist for some forms of cardiomyopathy, the majority of patients receives standard heart failure and device therapy but others require lifelong careful monitoring. The diagnosis of cardiomyopathy is mainly based on the cardiac phenotype; therefore, non-invasive imaging is very important. Cardiovascular magnetic resonance has become the gold standard to assess cardiomyopathy as it combines functional information (e.g. wall motion) with myocardial tissue analysis (e.g. fibrosis and edema) and in some cases it can replace invasive endomyocardial biopsies. The importance of cardiovascular magnetic resonance to assess cardiomyopathy is based on several aspects: accurate analysis of cardiac dimensions and function, non-invasive tissue analysis to make the diagnosis (e.g. myocarditis), estimation of prognosis by non-invasive tissue analysis, high reproducibility for accurate follow-up examinations, potential for technical improvements (e.g. quantification of extracellular volume fraction by T1 mapping). In all types of cardiomyopathy, cardiovascular magnetic resonance has a major impact on the differential diagnosis, risk stratification and treatment. In some entities the appropriate clinical use is already confirmed by evidence (e.g. myocarditis) and in others there are first encouraging results that indicate the future potential (e.g. risk stratification in hypertrophic cardiomyopathy). Cardiovascular magnetic resonance has evolved as the gold standard to assess cardiomyopathy as it provides both functional and morphological information. It is recommended to use this technique in a comprehensive approach to achieve complete work-up of affected patients.