Study population
We reviewed the clinical, transthoracic echocardiography, and CMR findings of 370 patients at a single tertiary center, who were diagnosed with reperfused AMI, HCM, or DCM. The inclusion criteria were as follows: (1) patients with AMI for the first time who underwent successful percutaneous coronary intervention within 48 hours of chest pain were enrolled, AMI was diagnosed on the basis of the elevated levels of cardiac enzyme and ST-segment or T-wave deviation on electrocardiography according to the established diagnostic criteria [9]. We excluded patients with chronic ischemic disease. (2) Patients with maximal LV hypertrophy greater than 13 mm and a ratio of maximal thickness to posterior wall thickness greater than 1.3 without an underlying cause of hypertrophy, such as uncontrolled hypertension or aortic stenosis, were enrolled as HCM [10]. The patients diagnosed infiltrative disease, such as amyloidosis were excluded in HCM group. (3) DCM patients were defined individuals who matched the diagnostic criteria established by the World Health Organization. The patients were diagnosed with non-ischemic cause of DCM were only included. The patients with inadequate tracking quality by CMR and those with pulmonary vascular disease at the time of echocardiography or CMR were also excluded. This study was approved by the Institutional Review Board of Gangnam Severance Hospital (3-2021-0030).
Echocardiographic Analysis
A comprehensive echo-Doppler evaluation was performed according to the current guidelines [11]. The E/e′ ratio was subsequently calculated. When the peaks E and A were fused due to tachycardia or atrioventricular block, the peak velocities of the fused mitral inflow waves were used for E/e’ calculation [12] ; additionally, the average value of five consecutive beats was used in patients with atrial fibrillation. The PASP was calculated as 4 × (peak TRV)2 + right atrial pressure, where the right atrial pressure was estimated according to the inferior vena cava diameter and its respiratory variations.
Cmr Imaging And Measurements Of Ecv
CMR was performed using a 1.5-T scanner (Magnetom Avanto; Siemens Medical Solutions, Erlangen, Germany) or 3-T scanner (Magnetom Vida; Siemens Medical Solutions, Erlangen, Germany) with a phased-array body coil. The LV 2-, 3-, 4-chamber, and short-axis views were obtained using cine images with a steady-state free precession sequence. After the administration of a gadolinium-based contrast agent (0.2 mmol/kg gadoterate dimeglumine; Dotarem, Guerbet, France), Native T1 mapping with a modified Look-Locker technique was performed during the mid-diastolic phase, and post-T1 mapping was performed 15 min after the contrast media injection using the same slice axis and parameters as the pre-T1 mapping. Native T1, post-T1, and ECV analyses were performed with QmapECV 2.2.44 (Medis, Leiden, Netherlands) [13]. The myocardial ECV (n=297) was automatically calculated using the following equation in 16 segments, and the average value was used for further analysis.
ECV = (\({\Delta }\)R1 of myocardium\(∕{\Delta }\)R1 of LV blood pool)\(\times\)(1\(-\)hematocrit),
where R1=1\(∕\)T1 and \({\Delta }\)R1=post-contrast R1\(-\)pre-contrast R1. (Figure 1)
The reproducibility and standardization of ECV measurement was reported previously [13].
LA strain and phasic volume analysis using feature tracking CMR
The myocardial strain analysis using feature tracking CMR was performed using semi-automated software (QstrainMR 2.0, Medis, Leiden, Netherlands). The LA endocardial border was manually traced in a 4-chamber long-axis view using the LV end-diastole as the reference phase. The LA global longitudinal strain (GLS) was defined as the average peak strain value. The LA maximal, pre-contraction (pre-A in cases without atrial fibrillation), and minimal volumes were measured. The LA total emptying fraction was calculated as (LA maximal volume – LA minimal volume) / LA maximal volume; the reservoir fraction, as (LA maximal volume – LA minimal volume / LA minimal volume); the conduit fraction as (LA maximal volume – LA pre-A volume) / LA maximal volume; and the active emptying fraction as (LA pre-A volume – LA minimal volume) / LA pre-A volume [14], as shown in Figure 1. The LA volume divided by the body surface area was defined as the LA volume index (LAVI), and E/e’ divided by LA-GLS was defined as the LA stiffness index [15].
Statistical analysis
The baseline characteristics were summarized using frequencies and percentages and examined using the chi-square test for categorical variables. The continuous variables are reported as the mean and standard deviation or interquartile range for non-normally distributed variables. For normally distributed variables, the analysis of variance (ANOVA) was performed to test the differences among the three groups. A post-hoc test with Tukey’s HSD was conducted for pairwise comparisons. Non-normally distributed variables were compared using the Kruskal-Wallis test, and the Dunn’s post-hoc test was performed for pair-wise comparisons. A univariable linear regression model was used to estimate the unadjusted coefficient of primary endpoints for each echocardiographic and each CMR characteristic. Univariable factors with P < 0.05 and the major relevant clinical factors were entered into multivariable analyses for the predictive value of variables for PASP. The coefficient values were generated and expressed, together with their 95% confidence intervals. A subgroup analysis was performed to evaluate the differential effect of clinical variables among the three groups clustered by a linear regression between PASP and E/e’: 1) relatively higher PASP group compared to E/e’, 2) within 95% confidence interval and 3) relatively lower PASP group compared to E/e’. All analyses used two-tailed tests with a significance level of 0.05. Statistical analyses were performed using SPSS software (Statistical Package for Social Sciences, version 25.0, IBM Corp., Armonk, NY).