Rationale and Objectives
To assess the performance of automated quantification of left ventricular function and mass based on heart deformation analysis (HDA) in asymptomatic older adults.
Materials and Methods
This study complied with Health Insurance Portability and Accountability Act regulations. Following the approval of the institutional review board, 160 asymptomatic older participants were recruited for cardiac magnetic resonance imaging including two-dimensional cine images covering the entire left ventricle in short-axis view. Data analysis included the calculation of left ventricular ejection fraction (LVEF), left ventricular mass (LVM), and cardiac output (CO) using HDA and standard global cardiac function analysis (delineation of end-systolic and end-diastolic left ventricle epi- and endocardial borders). The agreement between methods was evaluated using intraclass correlation coefficient (ICC) and coefficient of variation (CoV).
Results
HDA had a shorter processing time than the standard method (1.5 ± 0.3 min/case vs. 5.8 ± 1.4 min/case, P < 0.001). There was good agreement for LVEF (ICC = 0.552, CoV = 10.5%), CO (ICC = 0.773, CoV = 13.5%), and LVM (ICC = 0.859, CoV = 14.5%) acquired with the standard method and HDA. There was a systemic bias toward lower LVEF (62.8% ± 8.3% vs. 69.3% ± 6.7%, P < 0.001) and CO (4.4 ± 1.0 L/min vs. 4.8 ± 1.3 L/min, P < 0.001) by HDA compared to the standard technique. Conversely, HDA overestimated LVM (114.8 ± 30.1 g vs. 100.2 ± 29.0 g, P < 0.001) as compared to the reference method.
Conclusions
HDA has the potential to measure LVEF, CO, and LVM without the need for user interaction based on standard cardiac two-dimensional cine images.
Introduction
Cardiac aging, which can result in subclinical alterations in the heart, is considered a condition that bridges elderly patients and the incidence of cardiovascular events. At the same time, co-existing cardiovascular confounders, such as diabetes mellitus (DM) and hypertension (HTN), can further contribute to the development of cardiac aging. Left ventricular (LV) ejection fraction (LVEF) and LV mass (LVM) are indices presenting ventricular dysfunction and hypertrophy, two important indicators in cardiovascular risk estimation. In clinical practice, two-dimensional (2D) cine magnetic resonance imaging (MRI) has been adopted as a standard method for the measurement of LVEF and LVM. Balanced steady-state free processing (b-SSFP) is a commonly used MRI technique for the acquisition of cine MRI images at short-axis view because it provides good blood-myocardium contrasts . Generally, endocardial and epicardial borders of the LV are determined automatically or manually for each slice/phase of MRI based on signal differences among blood pool, LV wall, and outer structures. LV volumes at each cardiac phase will be obtained by summing up the LV areas in all slices covering the heart from the base to the apex. End systole and end diastole can be identified to define the smallest and the largest LV volumes, respectively, for the calculation of LVEF and cardiac output (CO). LV myocardial volume will be calculated by adding up the LV areas in each slice at end diastole and end systole. LVM can therefore be calculated by assuming a reasonable myocardial density.
Heart deformation analysis (HDA) is a recently developed image processing technique for the description of global and regional myocardial function and motion on cine MRI. Using a deformation image registration (DIR) algorithm, HDA is able to automatically track the shape of the LV through the entire cardiac cycle by calculating deformation fields (forward and backward) of myocardium tissue among sequential cardiac time frames . As such, global cardiac indices (LVEF, CO, and LVM) as well as regional myocardial motion indices (displacement, velocity, strain, and strain rate) can be extracted from cine images using a semiautomatic “one-stop-shop” analysis with minimal user interaction. However, to date, the capability of the HDA tool to evaluate LV global function and morphology has not been validated in a larger clinical study cohort. Therefore, the aim of the present study was to assess the accuracy of automated quantification of left ventricular function and mass based on HDA in asymptomatic older adults by using a standard LV global function analysis as the reference standard.
Materials and Methods
Study Participants
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Table 1
Description of Participants
Subjects ( N = 160) Male (%) 97 (60) Age (years) 72.0 ± 4.1 Weight (kg) 86.3 ± 17.8 Height (cm) 172.1 ± 9.8 BMI 28.9 ± 5.8 Heart rate (beats/min) 69.7 ± 10.2 DM (%) 39 (24) HTN (%) 57 (36)
BMI, body mass index. DM, diabetes mellitus. HTN, hypertension.
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MRI Facility
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Cine MRI Scan Protocol
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Image Processing
Standard Cine Image Processing
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HDA Analysis
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Data Processing and Statistical Analysis
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Results
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Table 2
The Differences of LVEF, CO, and LVM Measured with the HDA Tool and the Existing Method (Using Paired t Tests)
Processing Time (Min) LVEF (%) CO (L/min) LVM (g) HDA 1.5 ± 0.3 62.8 ± 8.3 4.4 ± 1.0 114.8 ± 30.1 Reference method 5.8 ± 1.4 69.3 ± 6.7 4.8 ± 1.3 100.2 ± 29.0P values <0.001 <0.001 <0.001 <0.001
CO, cardiac output; HDA, heart deformation analysis; LVEF, left ventricular ejection fraction; LVM, left ventricular mass.
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Discussion
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