Reproducibility study of left ventricular measurements with breath-hold cine MRI using a semiautomated volumetric image analysis program

Survival Outcomes After Heart Transplantation: Does Recipient Sex Matter?

BACKGROUND

Currently, women represent <25% of heart transplant recipients. Reasons for this female underrepresentation have been attributed to selection and referral bias and potentially poorer outcomes in female recipients. The aim of this study was to compare long-term posttransplant survival between men and women, when matched for recipient and donor characteristics.

METHODS AND RESULTS

Using the International Society for Heart and Lung Transplantation Registry, we performed descriptive analyses and estimated overall freedom from posttransplant death stratified by sex using Kaplan-Meier survival methods. Male and female recipients were matched according to the Index for Mortality Prediction After Cardiac Transplantation and Donor Risk Index score using 1:1 propensity score matching. The study cohort comprised 34 198 heart transplant recipients (76.3% men, 23.7% women) between 2004 and 2014. Compared with men, women were more likely younger (51 [39-59] versus 55 [46-61] years; P<0.001) and had a different distribution of heart failure etiology (P<0.001). In general, the prevalence of comorbidities was lower in women than in men. Women were less likely to have diabetes mellitus (19.1% versus 26.2%; P<0.001), hypertension (40.7% versus 47.9%; P<0.001), peripheral vascular disease (2.4% versus 3.3%; P=0.002), tobacco use (36.5% versus 52.3%; P<0.001), and prior cardiovascular surgery (38.6% versus 50.7%; P<0.001). Women were more likely to have a history of malignancy (10.5% versus 5.3%; P<0.001), require intravenous inotropes (41.4% versus 37.2%; P<0.001), and were less likely supported by an intra-aortic balloon pump (3.3% versus 3.8%; P=0.03) or durable ventricular assist device (22% versus 31.5%; P<0.001). Transplanted male recipients had a higher Index for Mortality Prediction After Cardiac Transplantation score (5 [2-7] versus 4 [1-6]; P<0.001). When male and female heart transplant recipients were matched for recipient and donor characteristics, there was no significant survival difference (P=0.57).

CONCLUSIONS

Overall survival does not differ between men and women after cardiac transplantation. Women who survive to heart transplantation appear to have lower risk features than male recipients but receive hearts from higher risk donors.

Effect of comprehensive initial training on the variability of left ventricular measures using fast-SENC cardiac magnetic resonance imaging

Cardiac magnetic resonance (CMR) is becoming the imaging modality of choice in multicenter studies where highly reproducible measurements are necessary. The purpose of this study was to assess the effect of comprehensive initial training on reproducibility of quantitative left ventricular (LV) parameters estimated using strain-encoded (SENC) imaging. Thirty participants (10 patients with heart failure (HF) and preserved LV ejection fraction (HFpEF), 10 patients with HF and reduced LV ejection fraction (HFrEF) and 10 healthy volunteers) were examined using fast-SENC imaging. Four observers with different experience in non-invasive cardiac imaging completed comprehensive initial training course and were invited to perform CMR data analysis. To assess agreement between observers, LV volumes, mass, ejection fraction (LVEF), global longitudinal strain (GLS) and global circumferential strain (GCS) were estimated using dedicated software (MyoStrain, USA). To test intraobserver agreement data analysis was repeated after 4 weeks. SENC imaging and analysis were fast and were completed in less than 5 minutes. LV end-diastolic volume index (LVEDVi), LVEF and strain were significantly lower in HFpEF patients than in healthy volunteers (p = 0.019 for LVEDVi; p = 0.023 for LVEF; p = 0.004 for GLS and p < 0.001 for GCS). All LV functional parameters were further reduced in HFrEF. Excellent interobserver agreement was found for all LV parameters independently of the level of experience. The reproducibility of LV mass was lower, especially at the intraobserver level (ICC 0.91; 95% CI 0.74–0.96). LV volumetric and functional parameters derived using fast-SENC imaging, are highly reproducible. The appropriate initial training is relevant and allows to achieve highest concordance in fast-SENC measurements.

Strain-encoded cardiac magnetic resonance imaging: a new approach for fast estimation of left ventricular function

Background

Recently introduced fast strain-encoded (SENC) cardiac magnetic resonance (CMR) imaging (fast-SENC) provides real-time acquisition of myocardial performance in a single heartbeat. We aimed to test the ability and accuracy of real-time strain-encoded CMR imaging to estimate left ventricular volumes, ejection fraction and mass.

Methods

Thirty-five subjects (12 healthy volunteers and 23 patients with known or suspected coronary artery disease) were investigated. All study participants were imaged at 1.5 Tesla MRI scanner (Achieva, Philips) using an advanced CMR study protocol which included conventional cine and fast-SENC imaging. A newly developed real-time free-breathing SENC imaging technique based on the acquisition of two images with different frequency modulation was employed.

Results

All parameters were successfully derived from fast-SENC images with total study time of 105 s (a 15 s scan time and a 90 s post-processing time). There was no significant difference between fast-SENC and cine imaging in the estimation of LV volumes and EF, whereas fast-SENC underestimated LV end-diastolic mass by 7%.

Conclusion

The single heartbeat fast-SENC technique can be used as a good alternative to cine imaging for the precise calculation of LV volumes and ejection fraction while the technique significantly underestimates LV end-diastolic mass.

Left ventricular hypertrophy by ECG versus cardiac MRI as a predictor for heart failure

OBJECTIVE

To determine if there is a significant difference in the predictive abilities of left ventricular hypertrophy (LVH) detected by ECG-LVH versus LVH ascertained by cardiac MRI-LVH in a model similar to the Framingham Heart Failure Risk Score (FHFRS).

METHODS

This study included 4745 (mean age 61±10 years, 53.5% women, 61.7% non-whites) participants in the Multi-Ethnic Study of Atherosclerosis. ECG-LVH was defined using Cornell voltage product while MRI-LVH was derived from left ventricular mass. Cox proportional hazard regression was used to examine the association between ECG-LVH and MRI-LVH with incident heart failure (HF). Harrell's concordance C-index was used to estimate the predictive ability of the model when either ECG-LVH or MRI-LVH was included as one of its components.

RESULTS

ECG-LVH was present in 291 (6.1%), while MRI-LVH was present in 499 (10.5%) of the participants. Both ECG-LVH (HR 2.25, 95% CI 1.38 to 3.69) and MRI-LVH (HR 3.80, 95% CI 1.56 to 5.63) were predictive of HF. The absolute risk of developing HF was 8.81% for MRI-LVH versus 2.26% for absence of MRI-LVH with a relative risk of 3.9. With ECG-LVH, the absolute risk of developing HF 6.87% compared with 2.69% for absence of ECG-LVH with a relative risk of 2.55. The ability of the model to predict HF was better with MRI-LVH (C-index 0.871, 95% CI 0.842 to 0.899) than with ECG-LVH (C-index 0.860, 95% CI 0.833 to 0.888) (p<0.0001).

CONCLUSIONS

ECG-LVH and MRI-LVH are predictive of HF. Substituting MRI-LVH for ECG-LVH improves the predictive ability of a model similar to the FHFRS.

Assessment of left ventricular ejection fraction using the wall motion score index in cardiac magnetic resonance imaging

BACKGROUND

Left ventricular ejection fraction (LVEF) is an important indicator of left ventricular function and of the severity and prognosis of ischaemic heart disease. Assessment of regional function using the wall motion score index (WMSI) is an alternative means of evaluating left ventricular function.

AIM

We attempted to evaluate LVEF by a method using the WMSI with cardiac magnetic resonance imaging (MRI).

METHODS

One hundred and twenty-two patients referred for evaluation of heart disease had rest WMSI evaluation by cardiac MRI. The WMSI was evaluated using the 16-segment model and score proposed by the American Society of Echocardiography. In our first group of 80 patients, a correlation between WMSI and cardiac MRI LVEF was established and a regression equation was derived. This regression equation was then used in 42 consecutive patients to compare WMSI LVEF with the gold standard MRI LVEF.

RESULTS

In the first 80 patients, MRI LVEF and WMSI correlated very well (r=0.93). Similarly, in the second group of 42 patients, WMSI LVEF derived from the regression equation correlated very well with MRI LVEF (r=0.94).

CONCLUSION

An objective evaluation of LVEF can be easily made using the WMSI with cardiac MRI, which correlates very well with standard MRI planimetric methods.

The relationship of left ventricular mass and geometry to incident cardiovascular events: the MESA (Multi-Ethnic Study of Atherosclerosis) study

OBJECTIVE

The purpose of this study was to evaluate the relationship of left ventricular (LV) mass and geometry measured with cardiac magnetic resonance imaging (MRI) to incident cardiovascular events in the MESA (Multi-Ethnic Study of Atherosclerosis) study.

BACKGROUND

MRI is highly accurate for evaluation of heart size and structure and has not previously been used in a large epidemiologic study to predict cardiovascular events.

METHODS

A total of 5,098 participants in the MESA study underwent cardiac MRI at the baseline examination and were followed up for a median of 4 years. Cox proportional hazard models were constructed to predict the end points of coronary heart disease (CHD), stroke, and heart failure (HF) after adjustment for cardiovascular risk factors.

RESULTS

A total of 216 incident events were observed during the follow-up period. In adjusted models, the end points of incident CHD and stroke were positively associated with increased LV mass-to-volume ratio (CHD, hazard ratio [HR]: 2.1 per g/ml, p = 0.02; stroke, HR: 4.2 per g/ml, p = 0.005). In contrast, LV mass showed the strongest association with incident HF events (HR: 1.4 per 10% increment, p < 0.0001). The HF events occurred primarily in participants with LV hypertrophy, that is, >or=95th percentile of LV mass (HR: 8.6, 95% confidence interval: 3.7 to 19.9, reference group <50th percentile of LV mass).

CONCLUSIONS

The LV size was related to incident HF, stroke, and CHD in this multiethnic cohort. Whereas body size-adjusted LV mass alone predicted incident HF, concentric ventricular remodeling predicted incident stroke and CHD.

Addition of the long-axis information to short-axis contours reduces interstudy variability of left-ventricular analysis in cardiac magnetic resonance studies

OBJECTIVES

To reduce interstudy variability using long-axis information for correcting short-axis (SA) contours at basal and apical level for left-ventricular analysis by magnetic resonance imaging.

MATERIALS AND METHODS

A total of 20 patients with documented heart failure and 20 volunteers underwent magnetic resonance imaging examination twice for measuring endocardial end-diastolic volume, endocardial end-systolic volume, mass, and ejection fraction. The boundary of the left ventricle, the mitral valve plane, and apex were marked manually on the 2- and 4-chamber long-axis images. Automatic epicardial and endocardial contour detection was performed on the SA images using the intersection of the outlines from the long axis as starting positions. The same observer compared the interstudy variability of this method with analysis that was based on the SA images only.

RESULTS

The interstudy variability decreased when information from the long axis was included; for end-systolic volume, 9.6% versus 4.7% (P = 0.00014); for end-diastolic volume, 4.9% versus 2.5% (P = 0.0011); for mass, 7.4% versus 5.0% (P = 0.11); and for ejection fraction 12.2% versus 5.6% (P = 0.0017), respectively.

CONCLUSIONS

Identification of the mitral valve plane and apex on long-axis images to limit the extent of volume at the base and the apex of the heart reduces interstudy variability for left-ventricular functional assessment.

Iron-mobilizing properties of the gadolinium-DTPA complex: clinical and experimental observations

BACKGROUND

Gadolinium (Gd) magnetic resonance imaging (MRI) contrast agents are considered to be safe in patients with impaired renal function. Our study investigates a mechanism of severe iron intoxication with life-threatening serum iron levels in a haemodialysis patient following MRI with Gd-diethylenetriaminepentaacetic acid (Gd-DTPA) administration. His previous history was remarkable for multiple blood transfusions and biochemical evidence of iron overload. We hypothesized that Gd-DTPA may have an iron-mobilizing effect in specific conditions of iron overload combined with prolonged exposure to the agent.

METHODS

For the in vitro study, Gd-DTPA was added to mice liver homogenate and iron metabolism parameters were measured after incubation in comparison with the same samples incubated with saline only. For the in vivo study, an experimental model of acute renal failure in iron-overloaded rats was designed. Previously iron-overloaded and normally fed rats underwent bilateral nephrectomy by renal pedicle ligation, followed by Gd-DTPA or saline injection. Iron and iron saturation levels were checked before and 24 h after Gd-DTPA or vehicle administration.

RESULTS

Significant mobilization of iron from mice liver tissue homogenate in mixtures with Gd in vitro was seen in the control (saline) and in the experimental (Gd) groups (513+/-99.1 vs 1117.8+/-360.8 microg/dl, respectively; P<0.05). Administration of Gd-DTPA to iron-overloaded rats after renal pedicle ligation caused marked elevation of serum iron from baseline 143+/-3.4 to 570+/-8 microg/dl (P<0.0001). There were no changes of the named parameter, either in iron-overloaded anuric rats after saline injection or in normal diet uraemic animals, following Gd-DTPA administration.

CONCLUSIONS

The combination of iron overload and lack of adequate clearance of Gd chelates may cause massive liberation of iron with dangerous elevation of free serum iron. It is highly recommended that after Gd contrast study, end-stage renal disease patients with probable iron overload should undergo prompt and intensive haemodialysis for prevention of this serious complication.

Relationship between alcohol consumption, ambulatory blood pressure recordings and left ventricular mass

The relationship between alcohol consumption, blood pressure and left ventricular mass remains uncertain. A detailed alcohol intake history, clinic blood pressure measurements, 24-h ambulatory blood pressure recordings and measurements of left ventricular mass using magnetic resonance imaging (MRI) were performed in 98 males aged 47.9 +/- 9.7 years, 20 of whom were receiving antihypertensive monotherapy. Alcohol consumption (median intake 315 g/week, range 0-2050) was significantly related to supine systolic clinic blood pressures (beta = 0.20, p = 0.05) but not to clinic supine diastolic blood pressures (beta = 0.12, p = 0.25), 24-h blood pressures (systolic: beta = -0.03, p = 0.75; diastolic beta = -0.05, p = 0.60), awake blood pressures or sleeping blood pressures. Alcohol consumption was not related to left ventricular mass index (beta = -0.05, p = 0.59). Left ventricular mass was strongly related to mean 24-h systolic blood pressures (beta = 0.28, p = 0.01), mean awake and sleeping systolic blood pressures, and less strongly to clinic systolic blood pressures (beta = 0.23, p = 0.03). These results were not significantly altered by adjusting for age, smoking, body mass index or alcohol intake, or by excluding the 20 men who were receiving antihypertensive therapy. The results of this study suggest that alcohol consumption at levels commonly encountered in the community is not an important predictor of left ventricular mass index in men, either via direct effects or by indirect effects on blood pressure.

Measurements of left ventricular dimensions using real-time acquisition in cardiac magnetic resonance imaging: comparison with conventional gradient echo imaging

This study investigates the use of real-time acquisition in cardiac magnetic resonance imaging (MRI) for measurements of left ventricular dimensions in comparison with conventional gradient echo acquisition. Thirty-one subjects with a variety of left ventricular morphologies to represent a typical clinical population were studied. Short-axis data sets of the left ventricle (LV) were acquired using a conventional turbo-gradient echo and an ultrafast hybrid gradient echo/echo planar sequence with acquisition in real-time. End-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF) and left ventricular mass (LV mass) were measured. The agreement between the two acquisitions and interobserver, intraobserver and interstudy variabilities were determined. The bias between the two methods was 5.86 ml for EDV, 0.23 ml for ESV and 0.94% for EF. LV mass measurements were significantly lower with the real-time method (mean bias 14.38 g). This is likely to be the result of lower spatial resolution and chemical shift artefacts with the real-time method. Interobserver, intraobserver and interstudy variabilities were low for all parameters. In conclusion, real time acquisition in MRI can provide accurate and reproducible measurements of LV dimensions in subjects with normal as well as abnormal LV morphologies, but LV mass measurements were lower than with conventional gradient echo imaging.

Dobutamine stress cine-MRI of cardiac function in the hearts of adult cardiomyocyte-specific VEGF knockout mice

A mouse model of non-necrotic vascular deficiency in the adult heart was studied using cine-magnetic resonance imaging (MRI) and other techniques. The mice lacked cardiomyocyte-derived vascular endothelial growth factor (VEGF) following a targeted knockout in the ventricular cardiomyocytes. Quantitative endothelial labeling showed that the capillary density was significantly reduced in the hearts of knockout mice. Gene expression patterns suggested that they were hypoxic. Semiautomated MR image analysis was employed to obtain both global and regional measurements of left ventricular function at 10 or more time points through the cardiac cycle. MRI measurements showed a marked reduction in ejection fraction both at rest and under low- and high-dose dobutamine stress. Regional wall thickness, thickening, and displacement were all attenuated in the knockout mice. A prolonged high-dose dobutamine challenge was monitored by MRI. A maximal response was sustained for 90 minutes, suggesting that it did not depend on endogenous glycogen stores.

Steady-state free precession magnetic resonance imaging of the heart: comparison with segmented k-space gradient-echo imaging

Steady-state free precession imaging is a promising technique for cardiac magnetic resonance imaging (MRI), as it provides improved blood/myocardial contrast in shorter acquisition times compared with conventional gradient-echo acquisition. The better contrast could improve observer agreement and automatic detection of cardiac contours for volumetric assessment of the ventricles, but measurements might differ from those obtained using conventional methods. We compared volumetric measurements, observer variabilities, and automatic contour detection between a steady-state free precession imaging sequence (BFFE = balanced fast field echo) and segmented k-space gradient-echo acquisition (TFE = turbo field echo) in 41 subjects. With BFFE, significantly higher end-diastolic and end-systolic volumes and lower wall thickness, ventricular mass, ejection fraction, and wall motion were observed (P < 0.0001), while interobserver variabilities were lower and automatic contour detection of endocardial contours was more successful. We conclude that the improved image quality of BFFE reduces the observer-dependence of volumetric measurements of the left ventricle (LV) but results in significantly different values in comparison to TFE measurements.

The effects of ACE inhibitor therapy on left ventricular myocardial mass and diastolic filling in previously untreated hypertensive patients: a cine MRI study

Cardiac remodeling in case of hypertension induces hypertrophy of myocytes and elevated collagen content and, subsequently, impaired diastolic filling of the left ventricle. The purpose of this prospective study was to evaluate changes of left ventricular (LV) myocardial mass, as well as diastolic filling properties, in hypertensive patients treated with the ACE inhibitor fosinopril. Sixteen hypertensive patients with echocardiographically documented LV hypertrophy and diastolic dysfunction received fosinopril (10-20 mg daily). Measurements of LV myocardial mass and properties of diastolic filling (peak filling fraction (PFF); peak filling rate (PFR)) were performed prior to medication, as well as after 3 and 6 months of therapy using cine magnetic resonance imaging (MRI). Ten healthy subjects served as a control group. LV myocardial mass (g/m2) decreased continuously within 3-6 months of follow-up by 32% (148 +/- 40 vs. 120 +/- 26 vs. 101 +/- 22 g/m2; P < 0.0001/0.005). The extent of regression correlated to the severity of LV hypertrophy at baseline (r = 0.77; P < 0.004). Early diastolic filling increased significantly within 6 months of therapy (PFF (%): 36 +/- 6 vs. 61 +/- 7, P < 0.0001; PFR (mL/second): 211 +/- 48 vs. 282 +/- 48, P < 0.001). Cine MRI can be used to assess the time course of pharmacological effects on cardiac remodeling in the course of hypertension. ACE inhibitor therapy results in a significant reduction of LV mass within 3 months and is accompanied by a normalization of diastolic filling that is completed after 6 months.

Three-dimensional echocardiography with tissue harmonic imaging shows excellent reproducibility in assessment of left ventricular volumes

We studied the reproducibility of repeated measurements of left ventricular (LV) volumes by 2-dimensional (biplane method of disks) and 3-dimensional echocardiography (coaxial scanning) with tissue harmonic imaging. Ten healthy subjects underwent estimation of LV volumes by transthoracic echocardiography twice within 1 week by 2 different operators to investigate interexamination and operator variance. In addition, the analysis of LV volume was done manually by 2 observers to assess both interobserver and intraobserver variances. With 3D echocardiography, observer variation had the greatest impact on variance. Operator variability showed important contributions to total variance with the use of 2D echocardiography. The reproducibility of 3D echocardiography and tissue harmonic imaging is excellent and comparable to magnetic resonance imaging techniques; 3D echocardiography therefore should provide a powerful tool for noninvasive LV volume estimation.

Quantification of global and regional ventricular function in cardiac magnetic resonance imaging

One of the strong assets of cardiac magnetic resonance (CMR) is its ability to assess myocardial anatomy, structure, function, flow, and perfusion within a single examination. Quantification of global and regional function from magnetic resonance imaging (MRI) studies was shown to be accurate and reproducible in experimental and clinical research studies. With the advent of high-performance MRI scanners and newly developed pulse sequences, image acquisition times have been reduced considerably in recent years. However, the clinical use of CMR remains limited for various reasons. Among these limitations is that the amount of images obtained in a typical cardiac examination is so large that visual and especially quantitative image analysis is tedious and time consuming. There is an urgent need for optimized dedicated software tools featuring highly automated contour detection and optimized display capabilities to present the quantitative results to the physician in an orderly fashion, thus facilitating clinical decision making. This article focuses on the state of the art in CMR postprocessing techniques for quantitative assessment of global and regional function.

A multicenter validation of an active contour-based left ventricular analysis technique

Quantitative analysis of functional cardiac magnetic resonance (MR) images has been limited by the lack of well-validated, semiautomatic, methods for rapid analysis. We describe the evaluation of a DICOM-compatible PC-based parallel-processing tool, for cardiac magnetic resonance analysis (CAMRA), which supports semiautomatic image mensuration using an active contour model-based algorithm. The CAMRA software was used to analyze data from 12 patients in a multicenter acquisition and analysis trial to compare semiautomatic contour detection with manual planimetry of the left ventricular endocardium from short-axis, breath-held, cine gradient-echo images. There was excellent agreement between the manual and semiautomatic measurements of global left ventricular function, with no significant (P = 0.32) difference in the determination of ejection fraction (-0.9 +/- 3.1% [mean difference +/- 1 standard deviation]). There was no significant interobserver difference in the semiautomatically measured ejection fraction. Additionally, a single observer completed the analysis on data from 30 patients and found no significant (P = 0.05) difference in the determination of ejection fraction (-1.3 +/- 3.5% [mean difference +/- 1 standard deviation]). The CAMRA software demonstrates the capability for the reproducible evaluation of global left ventricular function in cardiac patients, with adequate interobserver reproducibility for use in multicenter trials.

Right ventricular volumes and ejection fraction with fast cine MR imaging in breath-hold technique: applicability, normal values from 52 volunteers, and evaluation of 325 adult cardiac patients

Our goal was to establish right ventricular (RV) volume and ejection fraction (EF) values in normal volunteers with fast magnetic resonance (MR) imaging using a breath-hold technique, to assess the frequency and severity of RVEF abnormality in cardiac patients and to compare RV with left ventricular (LV) data. We performed simultaneously derived RV and LV fast cine measurements in 52 normals and 325 patients with coronary artery disease (CAD), acquired valvular disease (VD), cardiomyopathy (CM), or congenital heart disease (CHD). RVEF was reduced in 31% (102) of all patients, in 50% dilated CM, 39% CHD, 34% CAD, and 22% acquired VD patients. Solitary abnormally low RVEF was found in only 15/325 (5%) of all patients, whereas combined with LVEF deterioration in 87/172 (51%) patients. RVEF reduction was mild in 64%, moderate in 25%, and severe in 11%. Although RVEF correlated significantly (r = 0.55, P < 0.001) with LVEF, the predictive value of LVEF for RVEF was low. We conclude that RV volumes can be routinely assessed with fast MRI and should be performed in addition to LV evaluation in CHD, in right-sided VD, and in all patients with an abnormal LVEF.J. Magn. Reson. Imaging 1999; 10:908-918.