Optimization of the method of measuring left ventricular end-diastolic diameter in cardiac magnetic resonance as a predictor of left ventricular enlargement
The research has been conducted in compliance with the principles of Good Clinical Practice and Declaration of Helsinki. Ethics Committee of Wroclaw Medical University approved the experimental protocol (protocol code KB-414/2021). The written informed consent has been obtained from all the patients taking part in the research. All data collected from the patients were anonymized.
The retrospective study included 78 consecutive patients who came to the MRI Laboratory of the Wroclaw Medical University for CMR in the period from November 15, 2020 to March 15, 2021. The mean age of the patients was 55.28 ± 17.18 years, the youngest patient was 22 years old, and the oldest was 87 years old. In the study group, 65.4% were men and 34.6% were women. The clinical indications constituting the reason why patients were referred for MRI included: heart failure (42 patients), cardiomyopathy (49) [including hypertrophic cardiomyopathy (16), dilated cardiomyopathy (26), arrhythmogenic right ventricular cardiomyopathy (2), left ventricular noncompaction (5)], myocarditis (9), coronary artery disease (15), arrhythmias (1), cardiac involvement in the course of systemic diseases (3) and pericardial pathologies (1). The characteristics of the study group are presented in Table 1.
To consider age and gender to optimize the method of LVEDD measuring in CMR as a predictor of LVEDV, subgroups were distinguished. Based on the gender criterion, a male subgroup (n = 51) and a female subgroup (n = 27) were established, while based on the age median (Me = 58 years), a group of patients aged < median (< 58 years, n = 37) and a group of patients aged ≥ median (≥ 58 years, n = 41) were established.
CMR was performed using one 1.5 T Signa Hdx MRI (General Electric Medical Systems, USA) device. CMR was performed according to a standard protocol. ECG gating and breath hold during the gating were used. The study protocol included locating sequences, low-resolution single-shot black blood lookup sequences (Single Shot FSE), CINE steady-state free precession sequences (SSFP), T2 fat saturation sequences (T2fs), and late gadolinium enhancement sequences (IRPrepFGRE). The study protocol consisted of a bolus injection of gadobutrol (Gadovist, Bayer Healthcare, Germany) in the amount of 0.2 mmol/kg body mass through the ulnar fossa veins.
CMR images obtained during the study were assessed using the GE ReportCARD Package (General Electric Medical Systems, USA), a standard application for CMR post-processing assessment provided by the MRI manufacturer. The standard assessment of CMR included the initial assessment of the mediastinal anatomy in the Single Shot FSE sequences, the assessment of the dimensions and volume of the heart chambers in the CINE sequences recorded in the short axis of the left ventricle and in the long axis in the 2-chamber, 3-chamber and 4-chamber views, and the assessment of morphological changes of the left ventricular myocardium (oedema and fibrosis) in T2fs and LGE sequences. In the standard CMR evaluation, the left atrium (LA) and the aortic root (Ao) dimensions were measured in the 3-chamber view; in the short axis view, the left ventricular end-diastolic diameter (LVEDD), anterior interventricular septum diastolic dimension (aIVSDD) and posterior wall diastolic dimension (PWDD) were measured in the basal-middle layers. Based on CINE images in the short axis of the left ventricle, the functional parameters of the left ventricle were measured using the volumetric method. Outlines of the epicardium and endocardium were made in successive layers of the short axis of the left ventricle in diastole and systole. Left ventricular end-diastolic and end-systolic volumes (LVEDV and LVESV) were calculated by summing the consecutive left ventricular lumen areas from the successive layers multiplied by the thickness of the layers. Left ventricular ejection fraction (LVEF) was calculated according to the mathematical formula: LVEF = (LVEDV − LVESV)/LVEDV × 100%. The application, considering the adopted standard myocardial density, estimated the left ventricular mass (LVM) based on the total volume of the left ventricular myocardium. Standard assessment of CMR was performed each time by one of two radiology and imaging diagnostics specialists with experience in the performance and interpretation of CMR reaching up to 150 examinations interpreted annually over the last 5–10 years.
The CINE SSFP images obtained during CMR were used to retrospectively perform additional measurements of the left ventricular dimensions in diastole. In addition to LVEDD measured in the basal-middle layers in the short axis view, measurements of LVEDD were made in the long axis in the 2-chamber, 3-chamber and 4-chamber views. LVEDD in the long axis views was measured at 1/3 of the proximal distance of the mitral valve from the apex (Fig. 1). For the purposes of the present study, additional measurements of the left ventricle dimensions were performed independently by two radiologists: one with almost 10 years of professional experience in the evaluation of CMR (researcher A), the other during training in the assessment of CMR (researcher B).
To assess the repeatability of the measurements of the left ventricular dimensions in diastole, secondary parametric variables were calculated, being the resultant of the measurement of LVEDD measured by researcher A and the measurement of the analogous diameter measured by researcher B. The calculated secondary variables and the formulas used to calculate them are as follows: mean measurement (mean, X): X = (measurement A + measurement B)/2; standard deviation of the measurement (standard deviation, SD): SD = √(((measurement A − X measurement)2) + ((measurement B − X measurement)2))/2); absolute difference (AD): AD =|A measurement − B measurement|; relative difference (RD): RD = AD of measurement/X of measurement; and the coefficient of variation (CV): CV = (SD of measurement/X of measurement) × 100%.
The statistical evaluation of the results was performed with the use of the “Dell Statistica 13” program (Dell Inc., USA). Quantitative variables were characterized by arithmetic means and standard deviations. The results for the qualitative variables were characterized by percentage values. The Shapiro–Wilk W test was used to assess the distribution of variables. In comparative analyses, the test for unrelated variables (in the case of normal distribution of variables) or the Mann–Whitney U test (in the absence of normal distribution of variables) was used to test the hypotheses. To determine the correlations between the studied variables, the Pearson or Spearman correlation analysis and the univariate regression analysis were performed. Moreover, the sensitivity and specificity analysis were performed with the use of ROC (Receiver Operating Characteristic) curve analysis. The results at the levels p < 0.05 were considered statistically significant.
Ethics approval and consent to participate
All procedures performed in studies involving human participants were in accordance with the ethical standards of the Ethics Committee of Wroclaw Medical University (protocol code KB-414/2021) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Consent for participation
Informed consent was obtained from all individual participants included in the study.