Entire Left Ventricular Myocardium Research Articles

Non-contrast cine cardiovascular magnetic resonance-based radiomics nomogram for predicting microvascular obstruction after reperfusion in ST-segment elevation myocardial infarction.

This study aimed to develop and validate a cine cardiovascular magnetic resonance (CMR)-based radiomics nomogram model for predicting microvascular obstruction (MVO) following reperfusion in patients with ST-segment elevation myocardial infarction (STEMI). In total, 167 consecutive STEMI patients were retrospectively enrolled. The patients were randomly divided into training and validation cohorts with a ratio of 7:3. All patients were diagnosed with myocardial infarction with or without MVO based on late gadolinium enhancement imaging. Radiomics features were extracted from the cine CMR end-diastolic volume phase of the entire left ventricular myocardium (3D volume). The least absolute shrinkage and selection operator (LASSO) regression was employed to select the features that were most relevant to the MVO; these features were then used to calculate the radiomics score (Rad-score). A combined model was developed based on independent risk factors screened using multivariate regression analysis and visualized using a nomogram. Performance was assessed using receiver operating characteristic curve, calibration curve, and decision curve analysis (DCA). The univariate analysis of clinical features demonstrated that only cardiac troponin I (cTNI) was significantly associated with MVO. LASSO regression revealed that 12 radiomics features were strongly associated with MVO. Multivariate regression analysis indicated that cTNI and Rad-score were independent risk factors for MVO. The nomogram based on these two features achieved an area under the curve of 0.86 and 0.78 in the training and validation cohorts, respectively. Calibration curves and DCA indicated the clinical feasibility and utility of the nomogram. A CMR-based radiomics nomogram offers an effective means of predicting MVO without contrast agents and radiation, which could facilitate risk stratification of patients with STEMI after PCI for reperfusion.

Imaging of cardiac sympathetic dysfunction with 18F-FDOPA PET/CT in patients with heart failure: a pilot study

BackgroundRoutine use of cardiac sympathetic imaging in HF has been limited by the lower availability/sensitivity of radiotracers. This study was aimed to assess the feasibility of 18F-FDOPA (commonly available PET-radiotracer) in assessment of cardiac autonomic dysfunction. MethodsTwenty-four controls (46.5 ± 11.1 years, 16men) and 24 patients (43.5 ± 11.0 years, 18men) with diagnosed HF (Framingham-Criteria) underwent cardiac-PET/CT. Region(s) Of Interest were drawn over entire left ventricular myocardium (LV), individual walls, and mediastinum (M). Coefficient of Variation (CV) was calculated from individual wall counts. ResultsHF patients had significantly lower myocardial 18F-FDOPA uptake (P < .001, independent t test) than controls [32.4% ± 9.5% global reduction; highest in apex (39.9% ± 7.0%)]. A cut-off of LV/M ≤ 1.68 could differentiate patients from controls with sensitivity and specificity of 100% and 95.8%, respectively. LV/M correlated positively with EF (Pearson coefficient = 0.460, P .031). During follow-up, 3 patients were lost to follow-up, 4 died (survival-20.5 ± 4 months), 2 worsened, and 15 remained stable/showed mild improvement. Patients who worsened/died during follow-up had higher CV than those with stable/improving symptoms [0.16 ± 0.05 vs 0.11 ± 0.05, P value .069 (independent t test); Cox regression P = .084]. ConclusionMyocardial 18F-FDOPA uptake in patients with HF is significantly reduced. Higher reduction is seen in those with lower EF. CV, a maker of regional heterogeneity, is a potential prognostic marker.

Identification of fibrosis in hypertrophic cardiomyopathy: a radiomic study on cardiac magnetic resonance cine imaging

ObjectivesHypertrophic cardiomyopathy (HCM) often requires repeated enhanced cardiac magnetic resonance (CMR) imaging to detect fibrosis. We aimed to develop a practical model based on cine imaging to help identify patients with high risk of fibrosis and screen out patients without fibrosis to avoid unnecessary injection of contrast.MethodsA total of 273 patients with HCM were divided into training and test sets at a ratio of 7:3. Logistic regression analysis was used to find predictive image features to construct CMR model. Radiomic features were derived from the maximal wall thickness (MWT) slice and entire left ventricular (LV) myocardium. Extreme gradient boosting was used to build radiomic models. Integrated models were established by fusing image features and radiomic models. The model performance was validated in the test set and assessed by ROC and calibration curve and decision curve analysis (DCA).ResultsWe established five prediction models, including CMR, R1 (based on the MWT slice), R2 (based on the entire LV myocardium), and two integrated models (ICMR+R1 and ICMR+R2). In the test set, ICMR+R2 model had an excellent AUC value (0.898), diagnostic accuracy (89.02%), sensitivity (92.54%), and F1 score (93.23%) in identifying patients with positive late gadolinium enhancement. The calibration plots and DCA indicated that ICMR+R2 model was well-calibrated and presented a better net benefit than other models.ConclusionsA predictive model that fused image and radiomic features from the entire LV myocardium had good diagnostic performance, robustness, and clinical utility.Key Points• Hypertrophic cardiomyopathy is prone to fibrosis, requiring patients to undergo repeated enhanced cardiac magnetic resonance imaging to detect fibrosis over their lifetime follow-up.• A predictive model based on the entire left ventricular myocardium outperformed a model based on a slice of the maximal wall thickness.• A predictive model that fused image and radiomic features from the entire left ventricular myocardium had excellent diagnostic performance, robustness, and clinical utility.

Assessment of myocardial sympathetic innervation with 18F-FDOPA-PET/CT in patients with autonomic dysfunction: feasibility study in IPD patients

BackgroundDysfunction and denervation of myocardial nor-adrenergic sympathetic neurons has been documented in IPD patients with dysautonomia. The aim of this study was to evaluate the feasibility of single tracer imaging of myocardial sympathetic and cerebral striatal involvement in these patients. MethodsTwenty-two controls (mean-age 59.09 ± 12.39 years, 15 men) with no clinical autonomic-dysfunction and normal striatal-uptake in 18F-FDOPA-PET/CT; and 28 patients (mean-age 58.18 ± 8.25 years, 18 men) with autonomic-dysfunction (in Autonomic Function Tests) and striatal dopaminergic-dysfunction were enrolled. Both cardiac-PET/CT (40 minutes post IV-injection of 185-259MBq 18F-FDOPA) and Brain-PET/CT (60 minutes post-IV) were acquired in same session. ROIs were drawn over the entire left ventricular myocardium, individual walls and mediastinum for quantification. Patients and controls were followed-up for 26.93 ± 5.43 months and 37.91 ± 8.63 months, respectively. ResultsStriatal and myocardial-parameters were significantly lower in patients compared to controls; with Myocardium/mediastinal ratio (MwMR) yielding the area-under-the-curve of .941 (P < .001). MwMR correlated negatively with the drop in systolic blood pressure (SBP) during AFTs {Pearson-coefficient (−).565, P = .002}. Mean MwMR in patients with abnormal-AFTs was significantly lower than patients with borderline-AFTs (1.39 ± .12 vs 1.55 ± .10; P = .002). 9/20 patients with abnormal-AFTs showed functional worsening during follow-up, compared to 2/8 with borderline-AFTs. ConclusionSingle tracer, single session imaging of striatal and cardiac sympathetic dysfunction in patients with advanced IPD is feasible with use of 18F-FDOPA. Significantly reduced 18F-FDOPA uptake is seen in the myocardium of the IPD patients with sympathetic dysfunction.

Exploring the Utility of Radiomic Feature Extraction to Improve the Diagnostic Accuracy of Cardiac Sarcoidosis Using FDG PET.

BackgroundThis study aimed to explore the radiomic features from PET images to detect active cardiac sarcoidosis (CS).MethodsForty sarcoid patients and twenty-nine controls were scanned using FDG PET-CMR. Five feature classes were compared between the groups. From the PET images alone, two different segmentations were drawn. For segmentation A, a region of interest (ROI) was manually delineated for the patients' myocardium hot regions with standardized uptake value (SUV) higher than 2.5 and the controls' normal myocardium region. A second ROI was drawn in the entire left ventricular myocardium for both study groups, segmentation B. The conventional metrics and radiomic features were then extracted for each ROI. Mann-Whitney U-test and a logistic regression classifier were used to compare the individual features of the study groups.ResultsFor segmentation A, the SUVmin had the highest area under the curve (AUC) and greatest accuracy among the conventional metrics. However, for both segmentations, the AUC and accuracy of the TBRmax were relatively high, >0.85. Twenty-two (from segmentation A) and thirty-five (from segmentation B) of 75 radiomic features fulfilled the criteria: P-value < 0.00061 (after Bonferroni correction), AUC >0.5, and accuracy >0.7. Principal Component Analysis (PCA) was conducted, with five components leading to cumulative variance higher than 90%. Ten machine learning classifiers were then tested and trained. Most of them had AUCs and accuracies ≥0.8. For segmentation A, the AUCs and accuracies of all classifiers are >0.9, but k-neighbors and neural network classifiers were the highest (=1). For segmentation B, there are four classifiers with AUCs and accuracies ≥0.8. However, the gaussian process classifier indicated the highest AUC and accuracy (0.9 and 0.8, respectively).ConclusionsRadiomic analysis of the specific PET data was not proven to be necessary for the detection of CS. However, building an automated procedure will help to accelerate the analysis and potentially lead to more reproducible findings across different scanners and imaging centers and consequently improve standardization procedures that are important for clinical trials and development of more robust diagnostic protocols.

An Assessment of Different Region of Interest (ROI) Sampling Techniques for Calculating Native T1 and Extracellular Volume (ECV) on Cardiac MRI

Extracellular volume and native T1 values in CMRI are non-invasive determinants of myocardial remodelling, fibrosis, and inflammation. Native T1 values are often measured in the interventricular septum of diffuse disease to represent the entire left ventricular myocardium.

Echocardiographic global longitudinal strain is associated with infarct size assessed by cardiac magnetic resonance in acute myocardial infarction

The aim of this study was to investigate if there was an association between infarct size (IS) measured by cardiac magnetic resonance (CMR) and echocardiographic global longitudinal strain (GLS) in the early stage of acute myocardial infarction in patients with preserved left ventricular ejection fraction (LVEF). Patients with ST-segment elevation myocardial infarction who underwent primary percutaneous coronary intervention were assessed with CMR and transthoracic echocardiogram within 1 week of hospital admission. Two-dimensional speckle tracking was performed using a semi-automatic algorithm (EchoPac, GE Healthcare). Longitudinal strain curves were generated in a 17-segment model covering the entire left ventricular myocardium. GLS was calculated automatically. LVEF was measured by auto-LVEF in EchoPac. IS was measured by late gadolinium enhancement CMR in short-axis views covering the left ventricle. The study population consisted of 49 patients (age 60.4 ± 9.7 years; 92% male). The study population had preserved echocardiographic LVEF with a mean of 45.8 ± 8.7%. For each percent increase of IS, we found an impairment in GLS by 1.59% (95% CI 0.57–2.61), P = 0.02, after adjustment for sex, age and LVEF. No significant association between IS and echocardiographic LVEF was found: −0.25 (95% CI: −0.61 to 0.11), P = 0.51. At the segmental level, the strongest association between IS and longitudinal strain was found in the apical part of the LV: impairment of 1.69% (95% CI: 1.14–2.23), P < 0.001, for each percent increase in IS. In conclusion, GLS was significantly associated with IS in the early stage of acute myocardial infarction in patients with preserved LVEF, and this association was strongest in the apical part of the LV. No association between IS and LVEF was found.

Multiparametric cardiovascular magnetic resonance imaging in acute myocarditis: a comparison of different measurement approaches

BackgroundMyocardial T1 and T2 mapping are reliable diagnostic markers for the detection and follow up of acute myocarditis. The aim of this study was to compare the diagnostic performance of current mapping measurement approaches to differentiate between myocarditis patients and healthy individuals.MethodsFifty patients with clinically defined acute myocarditis and 30 healthy controls underwent cardiovascular magnetic resonance (CMR). Myocardial T1 relaxation times, T2 relaxation times, left ventricular (LV) function, T2 ratio, early gadolinium enhancement ratio, and presence of late gadolinium enhancement (LGE) were analysed. Native T1 and T2 relaxation times, as well as extracellular volume fraction (ECV) were measured for the entire LV myocardium (global), within the midventricular short axis slice (mSAX), within the midventricular septal wall (ConSept), and within the remote myocardium (remote). Receiver operating characteristics analysis was performed to compare diagnostic performance.ResultsAll measurement approaches revealed significantly higher native T1 and T2 relaxation times as well as ECV values in patients compared to healthy controls (p < 0.05 for all parameters). The global measurement approach showed highest diagnostic performance regarding all mapping parameters (AUCs, native T1: 0.903, T2: 0.847, ECV: 0.731). Direct comparison of the different measurement approaches revealed significant differences in diagnostic performance between the global and the remote approach regarding T1 relaxation times and ECV (p = 0.001 and p = 0.002 respectively). Further, the global measurement approach revealed significantly higher T1 relaxation times compared to the ConSept approach (AUCs: 0.903 vs. 0.783; p = 0.003) and nearly significant differences compared to the mSAX approach (AUC: 0.850; p = 0.051).T2 relaxation times showed no significant differences between all measurement approaches (p > 0.050 for all parameters).ConclusionsNative T1 and T2 mapping allow for accurate detection of acute myocarditis irrespective of the measurement approach used. Even measurements performed exclusively within remote myocardium allow for reliable detection of acute myocarditis, demonstrating diffuse involvement of disease despite a mostly regional or patchy distribution pattern of visible pathologies. The global measurement approach provides the overall best diagnostic performance in acute myocarditis for both T1 and T2 mapping.

OA197] Normal ranges of cardiac imaging radiomic metrics in healthy volunteers 24 h post ultra-small particles of iron oxide (USPIO) administration

Purpose Radiomics is a novel post-processing imaging methodology by which statistical features are extracted from medical images. The radiomic features of a myocardial region of interest open the possibility that novel descriptive patterns, found in images, may selectively identify phenotypic features of myocardial disease. Ultra-small particles of iron oxide (USPIO) uptake in the myocardium may show insights into a variety of pathologies that involve macrophage activation. While myocardial uptake may be low, any MRI signal changes due to USPIO uptake may be difficult to detect using global measures. Hence the potential need for more subtle metrics. The study aims to investigate USPIO uptake by innate macrophages resistant in normal myocardium using radiomics. Methods 11 healthy volunteers were imaged using a 3T Philips MRI scanner pre and exactly 24 h post administration of 2 (n = 7) or 4 mg/kg (n = 4) of USPIO. A short axis stack of entire left ventricular myocardium was acquired using a multi-echo gradient sequence (10 mm thickness, 0 mm gap). To delineate the myocardium, endocardial and epicardial border contours were manually traced on the first echo in the sequence (TE = 1.15 ms). First order and second order radiomic features were extracted from each slice of the stacks. Differences between feature values pre and post USPIO administration were calculated using paired samples t-test. Results In the 4 mg/kg USPIO group significant differences were found in Mean (p = 0.027), Large Area Emphasis (LAE) (p = 0.027), Zone Variance (ZV) (p = 0.027), Large Area Low Gray Level Emphasis (LALGLE) (p = 0.027), and Large Area High Gray Level Emphasis (LAHGLE) (p = 0.027). For the 2 mg/kg group, significant differences were found for Informal Measure of Correlation 1 (p = 0.009), LAE (p = 0.014), ZV (p = 0.014), Zone Percentage (p = 0.014), LALGLE (p = 0.014), and LAHGLE (p = 0.014). Conclusions Radiomics assessment of multi-echo gradient magnetic resonance images of the myocardium is feasible. Compared to pre USPIO images, post USPIO radiomics was able to detect a reduction in voxel intensity, an increase in intensity and run length homogeneity, and an increase in coarseness; with a smaller distribution of shorter run lengths.

Feasibility of myocardial flow reserve prediction without the use of dynamic data from myocardial perfusion positron emission tomography

Quantification of myocardial flow reserve (MFR) provides diagnostic value for detection of cardiovascular artery disease. However, the common calculation method for MFR requires dynamic acquisition and specific software. The study aimed to predict coronary artery disease by simpler calculation of myocardial count without the use of dynamic data from 13N-ammonia myocardial perfusion positron emission tomography (MP-PET). This study included 40 consecutive patients suspected of ischemic heart disease and 7 healthy controls (34 men and 13 women, 66 ± 12years). All participants underwent adenosine stress and rest 13N-ammonia MP-PET. From the dynamic images, the MFR in the entire left ventricular myocardium (ELV) and the three-vessel area was calculated by dividing stress myocardial blood flow (MBF) by rest MBF. From the static images, the myocardium-to-background ratio (MBR) was calculated by dividing each area's counts/pixel by background counts in the upper thoracic aorta/pixel in both stress and rest images. The MBR-increasing rate (MBR-IR) was calculated by dividing stress MBR by rest MBR. The relationship between MFR and MBR-IR in each area was examined. The cutoff diagnostic value of MBR-IR corresponding to that of MFR for detection of cardiovascular artery disease was calculated. Each MBR-IR was closely correlated with each MFR (r = 0.830 in ELV, r = 0.864 in LAD, r = 0.829 in LCX, r = 0.757 in RCA). The cutoff values of MBR-IR were 1.45 in ELV, 1.46 in LAD, 1.41 in LCX, and 1.45 in RCA, respectively. This study demonstrated that quantification of MBR-IR may provide diagnostic value for detection of coronary artery disease as well as MFR.

Global quantification of left ventricular myocardial perfusion at dynamic CT imaging: Prognostic value

BackgroundThere is no published data on the prognostic value of global myocardial perfusion values at stress dynamic CT myocardial perfusion imaging (CTMPI). MethodsData of 144 patients from 6 centers who had undergone coronary CT angiography (coronary CTA) and CTMPI were assessed. Coronary CTA studies were acquired at rest; CTMPI was performed under vasodilator stress. Coronary CTA data were evaluated for coronary artery stenosis (≥50% luminal narrowing) on a per-vessel basis. Volumes-of-interest were placed over the entire left ventricular myocardium to obtain global myocardial blood flow (MBF), myocardial blood volume (MBV), and volume transfer constant (Ktrans). Follow-up was obtained at 6/12/18 months. Major adverse cardiac events (MACE, defined as cardiac death, non-fatal myocardial infarction, unstable angina requiring hospitalization, and revascularization) served as the endpoint. ResultsMACE occurred in 40 patients (nonfatal myocardial infarction, n = 1, unstable angina, n = 13, PCI, n = 23, and CABG, n = 3). Patients with global MBF of <121 mL/100 mL/min were at increased risk for MACE (HR 2.07, 95% confidence interval [CI]: 1.12–3.84, p = 0.02). This association remained significant after adjusting for age, gender, and clinical risk factors (HR 2.17, 95%CI: 1.16–4.06, p = 0.02), after further adjusting for presence of ≥50% stenosis at coronary CTA (HR 2.18, 95%CI: 1.16–4.10, p = 0.02) and when excluding early (<6 months) revascularizations (HR 2.34, 95%CI: 1.01–5.43, p = 0.0486). Global MBV and Ktrans were not independent predictors of MACE. ConclusionGlobal quantification of left ventricular MBF at stress dynamic CTMPI may have incremental predictive value for future MACE over clinical risk factors and assessment of stenosis at coronary CTA.

Native myocardial T1 mapping in pulmonary hypertension: correlations with cardiac function and hemodynamics

ObjectivesTo analyze alterations in left ventricular (LV) myocardial T1 times in patients with pulmonary hypertension (PH) and to investigate their associations with ventricular function, mass, geometry and hemodynamics.MethodsFifty-eight patients with suspected PH underwent right heart catheterization (RHC) and 3T cardiac magnetic resonance imaging. Ventricular function, geometry and mass were derived from cine real-time short-axis images. Myocardial T1 maps were acquired by a prototype modified Look-Locker inversion-recovery sequence in short-axis orientations. LV global, segmental and ventricular insertion point (VIP) T1 times were evaluated manually and corrected for blood T1.ResultsSeptal, lateral, global and VIP T1 times were significantly higher in PH than in non-PH subjects (septal, 1249 ± 58 ms vs. 1186 ± 33 ms, p < 0.0001; lateral, 1190 ± 45 ms vs. 1150 ± 33 ms, p = 0.0003; global, 1220 ± 52 ms vs. 1171 ± 29 ms, p < 0.0001; VIP, 1298 ± 78 ms vs. 1193 ± 31 ms, p < 0.0001). In PH, LV eccentricity index was the strongest linear predictor of VIP T1 (r = 0.72). Septal, lateral and global T1 showed strong correlations with VIP T1 (r = 0.81, r = 0.59 and r = 0.75, respectively).ConclusionsIn patients with PH, T1 times in VIPs and in the entire LV myocardium are elevated. LV eccentricity strongly correlates with VIP T1 time, which in turn is strongly associated with T1 time changes in the entire LV myocardium.Key Points• Native T1 mapping detects left ventricular myocardial alterations in pulmonary hypertension• In pulmonary hypertension, native T1 times at ventricular insertion points are increased• These T1 times correlate strongly with left ventricular eccentricity• In pulmonary hypertension, global and segmental myocardial T1 times are increased• Global, segmental and ventricular insertion point T1 times are strongly correlated

Diffuse Myocardial Fibrosis in Children After Heart Transplantations: A Magnetic Resonance T1 Mapping Study.

It is unclear whether the myocardium undergoes accelerated fibrotic remodeling in children after heart transplantation (HTx). In this prospective study, cardiac magnetic resonance (CMR) studies in 17 patients 1.3 years (median, range 0.03-12.6 years) after HTx (mean age, 9.8 ± 6.2 years; 8 girls) were compared to CMR studies in 9 healthy controls (mean age, 12.4 ± 2.4 years; 4 girls). T1 measurements were performed at a midventricular short axis slice before (ie, native T1 times) and after the application of 0.2 mmol/kg gadopentetate dimeglumine in the interventricular septum, left ventricular (LV) free wall and encompassing the entire LV myocardium. The tissue-blood partition coefficient (TBPC), reflecting the degree of diffuse myocardial fibrosis, was calculated as a function of the ratio of T1 change of myocardium compared to blood. Native T1 times and TBPC were correlated with echocardiographic parameters of diastolic function. Native T1 times were significantly higher in HTx patients compared to controls in all regions assessed (LV free wall 973 ± 42 vs 923 ± 12 ms; P < 0.005; interventricular septum 1003 ± 31 vs 974 ± 21 ms, P < 0.05; entire LV myocardium 987 ± 33 vs 951 ± 16 ms; P < 0.005) and correlated with LV E/e' as an echocardiographic marker of diastolic dysfunction (r = 0.54, P < 0.05). The TBPC was elevated in the LV free wall (0.45 ± 0.06 vs 0.40 ± 0.03, P < 0.005) and the entire LV myocardium (0.47 ± 0.06 vs 0.43 ± 0.03, P < 0.05). Evidence of diffuse myocardial fibrosis and is already present in children after HTx. It appears to be associated with diastolic dysfunction.

Global quantification of left ventricular myocardial perfusion at dynamic CT: feasibility in a multicenter patient population.

The purpose of this study was to determine the feasibility of global quantitative measurements of left ventricular myocardial perfusion derived from stress dynamic CT myocardial perfusion imaging. The coronary CT angiographic and CT myocardial perfusion imaging datasets of 146 patients were visually evaluated for the presence of coronary artery stenosis and perfusion defects. For the quantitative analysis, volumes of interest were defined over the entire left ventricular myocardium to obtain global myocardial blood flow (MBF), myocardial blood volume (MBV), and volume transfer constant (K(trans)). In patients without anatomically significant coronary stenosis or perfusion defects, the mean value of global MBF was 137.9 ± 28.8 mL/100 mL/min; MBV, 19.5 ± 2.3 mL/100 mL; and K(trans), 85.8 ± 15.2 mL/100 mL/min. In patients with perfusion defects in one, two, or three vessels, the mean global MBF values were 132.6 ± 29.2, 117.4 ± 4.9, and 92.5 ± 11.2 mL/100 mL/min; MBV, 17.9 ± 3.2, 16.1 ± 3.1, and 12.8 ± 1.7 mL/100 mL; and K(trans), 80.4 ± 12.9, 76.6 ± 13.8, and 72.6 ± 15.5 mL/100 mL/min. In patients with significant (> 50%) stenosis in one, two, or three vessels at coronary CT angiography, the mean global MBF values were 129.2 ± 28.3, 120.5 ± 24.2, and 119.4 ± 33.5 mL/100 mL/min; MBV, 17.8 ± 3.3, 17.2 ± 3.2, and 14.7 ± 4.1 mL/100 mL; and K(trans), 80.3 ± 12.9, 76.0 ± 14.7, and 77.6 ± 13.2 mL/100 mL/min. Global quantitative assessment of left ventricular perfusion with stress dynamic CT myocardial perfusion imaging is feasible, and the findings correlate with the visual assessment of perfusion and the presence of coronary artery stenosis at coronary CT angiography. The potential clinical utility of this technique as a diagnostic tool for differentiating normal from globally reduced myocardial perfusion or as a prognostic marker merits further investigation.

A fast and effective method of quantifying myocardial perfusion by magnetic resonance imaging

The quantification of global myocardial blood flow (MBF) by measuring coronary sinus flow by magnetic resonance (MRI) was demonstrated to be very well correlated with positron emission tomography (PET). We proposed a new method for the quantification of regional myocardial perfusion with MRI by the integration of MBF and first pass technique. The aim of this study was to validate this new method for quantification of regional perfusion by comparing it with 13NH13-PET in swine models of myocardial infarction and in humans in resting and hyperemic conditions. MRI and 13NH3-PET was performed in 2 healthy swine, 11 swine models of myocardial infarction (5 reperfused, 6 non reperfused) and in 12 humans at rest and during hyperemia. MBF was estimated by MRI through the quantification of coronary sinus flow and left ventricular (LV) mass. The upslope of signal intensity (SI-upslope) of each myocardial segment was obtained by the first pass gadolinium technique. Regional SI-upslope was indexed by the upslope of the entire left ventricular myocardium (global upslope). Regional myocardial perfusion was estimated as the product of MBF and SI-upslope/global upslope. Regional perfusion was also estimated by 13NH3-PET. A close agreement of the MRI and PET techniques for measurement of regional myocardial perfusion was found in all myocardial segments by Bland-Altman analysis (mean difference 5.1 %; limits of agreement, -37.2-27.5 %). With the integration of the first pass technique and the measurement of global MBF by coronary sinus flow/LV mass, MRI allows direct quantification of regional myocardial perfusion.

Early diastolic mitral annular velocity at the interventricular septal annulus correctly reflects left ventricular longitudinal myocardial relaxation

Early diastolic mitral annular velocity (e') obtained by tissue Doppler imaging (TDI) is widely used to evaluate left ventricular (LV) diastolic function based on the assumption that it reflects myocardial relaxation in the long-axis direction. In this study, we aimed to determine whether or not e' truly reflects early diastolic longitudinal myocardial relaxation, and which is the most useful for evaluating LV diastolic function among e' measured at the interventricular-septal annulus (IS-e'), that measured at the lateral annulus (LW-e') or their mean value (M-e'). IS-e', LW-e', and M-e' were measured using colour TDI in 15 patients with hypertrophic cardiomyopathy, 13 patients with hypertension, and 19 control subjects. Using two-dimensional speckle-tracking imaging, early diastolic myocardial strain rates (SR(E)) were measured for the IS (IS-SR(E)), LW (LW-SR(E)), and entire LV myocardium (G-SR(E)). IS-e' was excellently correlated with IS-SR(E) (r = 0.90, P < 0.001); the correlation was better than that between LW-e' and LW-SR(E) (r = 0.75, P < 0.001). IS-e' and M-e' were well correlated with G-SR(E) (r = 0.88, P < 0.001 and r = 0.86, P< 0.001, respectively) and with LV early diastolic flow propagation velocity (FPV) (r = 0.77, P < 0.001 and r = 0.78, P < 0.001, respectively). The correlations of LW-e' to G-SR(E) (r = 0.80, P < 0.001) and FPV (r = 0.75, P < 0.001) did not reach this level. IS-e' well reflected LV longitudinal myocardial relaxation and LV diastolic function, and was found to be more useful in evaluating LV diastolic function than LW-e'.

Quantitative evaluation of local myocardial blood volume in contrast echocardiography

Myocardial perfusion is usually assessed by Single Photon Emission Computed Tomography (SPECT) imaging. Information about myocardial perfusion is sometimes deduced from angiography or Computed Tomography (CT) angiography, which detect coronary artery stenosis. Contrast echocardiography can be used for that purpose as well. However, the currently available data acquisition and analysis methods are difficult to manage in the clinical environment. This paper presents a novel contrast echo data acquisition protocol and parameter extraction procedure, providing an automatic quantitative evaluation of the local myocardial blood volume for the entire left ventricular myocardium. This information is indicative of local perfusion. Our method evaluates the myocardial blood volume according to the local gray level intensity, as measured during a single heartbeat, when there is a distinct myocardial opacification (based on visual estimation). The echocardiographic image analysis is based on a new attenuation correction technique, which compensates for the ultrasonic signal attenuation in both the tissue and the contrast agent. In comparison, the existing contrast echo based methods utilize the long-term temporal variability of the gray level to extract information regarding the local myocardial blood flow velocity. Our technique has been tested on 17 cine-loops of 15 different patients. We have found a high correlation between abnormal segments, detected automatically by our technique, and segments that have been clinically diagnosed as ischemic (at rest) or infarcted. For that purpose, we have defined ischemic segments as segments fed by coronary arteries with severe stenosis, as determined by angiography, and infarcted segments as segments after Acute Myocardial Infarction, as detected by electrocardiography. Furthermore, we have found a high correlation between the automatically calculated myocardial blood volume levels and the clinical evaluation of segmental contractility, based on echocardiographic imaging.

A stone heart: fatal cardiac microcalcification

Marked cardiac uptake of 99mTc-methyl-diphosphonate was noted on a bone scan performed in a patient with end-stage renal failure, on long-term dialysis. Amyloidosis was considered a possible explanation for clinical features that included severe left ventricular hypertrophy, low-voltage ECG, atrial and ventricular arrhythmia. Cardiac magnetic resonance (CMR) imaging demonstrated an unusual pattern of delayed contrast hyperenhancement of the entire left ventricular myocardium, suggesting diffuse myocardial fibrosis. This pattern was not typical for amyloidosis. Non-contrast CT …

Contrast-enhanced MR Imaging for Evaluation of Coronary Artery Disease before Elective Repair of Aortic Aneurysm

To prospectively evaluate the accuracy of first-pass contrast material-enhanced magnetic resonance (MR) imaging during stress and delayed contrast-enhanced MR imaging in the detection of significant coronary artery disease in patients before elective repair of aortic aneurysm. The study was approved by the institutional ethics committee, and informed consent was obtained from all patients. MR imaging was performed in 49 patients (42 men and seven women; mean age, 72.2 years; age range, 58-85 years) before the elective repair of atherosclerotic aortic aneurysms. Thirty-two patients had an abdominal aneurysm, 12 had a thoracic aneurysm, and five had a thoracoabdominal aneurysm. First-pass contrast-enhanced MR images were obtained with short-axis sections encompassing the entire left ventricular myocardium in the resting state and during pharmacologic stress. Inversion-recovery-prepared delayed contrast-enhanced MR images were obtained with breath holding to evaluate for the presence of infarction. All patients underwent coronary angiography within 2 weeks of MR imaging, and these findings were used as the standard of reference. The diagnostic results of first-pass contrast-enhanced MR imaging, delayed contrast-enhanced MR imaging, and a combination of both MR imaging methods in the detection of significant coronary artery disease were expressed as sensitivity, specificity, and accuracy. Coronary angiography depicted a clinically significant stenosis (>70% luminal diameter narrowing) in the coronary artery in 34 of the 49 patients (69%). First-pass contrast-enhanced MR imaging depicted stress-induced hypoenhancement in 27 of those 34 patients (79%). Delayed myocardial enhancement was observed in 17 of the 34 patients (50%). The overall sensitivity of rest-stress first-pass contrast-enhanced MR imaging and delayed contrast-enhanced MR imaging combined in the prediction of at least one coronary artery with significant stenosis was 88% (30 of 34 patients). The specificity and accuracy of MR imaging were 87% (13 of 15 patients) and 88% (43 of 49 patients), respectively. Contrast-enhanced MR imaging had an accuracy of 88% in the detection of significant coronary artery disease in patients with aortic aneurysm.

Regional myocardial metabolic rate of oxygen measured by O2-15 inhalation and positron emission tomography in patients with cardiomyopathy.

Positron emission tomography (PET) metabolic studies have investigated the pathways involved in fatty acid, glucose, and oxidative metabolism in cardiomyopathy and the impairments that occur in the damaged myocardium, but none have provided absolute quantitative variables. Recently, quantitative measurements of the metabolic rate of oxygen (MMRO2) and oxygen extraction fraction (OEF) using O2-15-labeled oxygen gas have been validated in animals and healthy volunteers. The purposes of the current study were to measure MMRO2 and OEF in cardiomyopathy with left ventricular (LV) dysfunction. The authors selected 25 study participants: 16 patients (10 with ischemic and 6 with dilated) cardiomyopathy with LV dysfunction, and 9 healthy volunteers. As evaluated by echocardiography, LV ejection fraction (LVEF) was decreased in patients (35%+/-9% vs. 65%+/-5%, P<0.01). The PET protocol consisted of transmission, C O2-15 static, H2 O-15 dynamic, and O2-15 gas inhalation steady state scans. An entire myocardial region of interest was drawn to encompass the entire LV myocardium on three midventricular slices in each participant. Data showed in patients with dilated cardiomyopathy significant reductions of MMRO2 (0.051+/-0.02 ml x min(-1) x g(-1) vs. 0.108+/-0.02 ml x min(-1) x g(-1), p = 0.01) and OEF (0.55+/-0.15 vs. 0.71+/-0.08, P = 0.01) when compared with healthy volunteers. Furthermore, OEF decreased significantly in lateral and inferior walls. Significant correlations were observed among OEF and the rate-pressure product (RPP) (P = 0.02), LVEF (P<0.001), MMRO2 and RPP (P = 0.04), and LVEF (P = 0.05). In patients with ischemic cardiomyopathy, MMRO2 was significantly reduced (0.039+/-0.02 ml x min(-1) x g(-1) vs. 0.108+/-0.02 ml x min(-1) x g(-1); p = 0.005) but not OEF (0.63+/-0.2 vs. 0.71+/-0.08; P = NS), when compared with healthy volunteers. Significant correlations were observed among OEF and RPP (P = 0.03), LVEF (P = 0.002), MMRO2 and RPP (P<0.01), and LVEF (P = 0.03). These data show that O2-15 gas inhalation and PET allow myocardial MMRO2 and OEF to be measured in patients with cardiomyopathy.