Longitudinal Changes in Left Ventricular Blood Flow Kinetic Energy After Myocardial Infarction: Predictive Relevance for Cardiac Remodeling.

BACKGROUND

Four-dimensional (4D) flow cardiac magnetic resonance (cardiac MR) imaging provides quantification of intracavity left ventricular (LV) flow kinetic energy (KE) parameters in three dimensions. ST-elevation myocardial infarction (STEMI) patients have been shown to have altered intracardiac blood flow compared to controls; however, how 4D flow parameters change over time has not been explored previously.

PURPOSE

Measure longitudinal changes in intraventricular flow post-STEMI and ascertain its predictive relevance of long-term cardiac remodeling.

STUDY TYPE

Prospective.

POPULATION

Thirty-five STEMI patients (M:F = 26:9, aged 56 ± 9 years).

FIELD STRENGTH/SEQUENCE: A 3 T/3D EPI-based, fast field echo (FFE) free-breathing 4D-flow sequence with retrospective cardiac gating.

ASSESSMENT

Serial imaging at 3-7 days (V1), 3-months (V2), and 12-months (V3) post-STEMI, including the following protocol: functional imaging for measuring volumes and 4D-flow for calculating parameters including systolic and peakE-wave LVKE, normalized to end-diastolic volume (iEDV) and stroke volume (iSV). Data were analyzed by H.B. (3 years experience). Patients were categorized into two groups: preserved ejection fraction (pEF, if EF > 50%) and reduced EF (rEF, if EF < 50%).

STATISTICAL TESTS

Independent sample t-tests were used to detect the statistical significance between any two cohorts. P < 0.05 was considered statistically significant.

RESULTS

Across the cohort, systolic KEi was highest at V1 (28.0 ± 4.4 μJ/mL). Patients with rEF retained significantly higher systolic KEi than patients with pEF at V2 (18.2 ± 3.4 μJ/mL vs. 6.9 ± 0.6 μJ/mL, P < 0.001) and V3 (21.6 ± 5.1 μJ/mL vs. 7.4 ± 0.9 μJ/mL, P < 0.001). Patients with pEF had significantly higher peakE-wave KEi than rEF patients throughout the study (V1: 25.4 ± 11.6 μJ/mL vs. 18.1 ± 9.9 μJ/mL, P < 0.03, V2: 24.0 ± 10.2 μJ/mL vs. 17.2 ± 12.2 μJ/mL, P < 0.05, V3: 27.7 ± 14.8 μJ/mL vs. 15.8 ± 7.6 μJ/mL, P < 0.04).

DATA CONCLUSION

Systolic KE increased acutely following MI; in patients with pEF, this decreased over 12 months, while patients with rEF, this remained raised. Compared to patients with pEF, persistently lower peakE-wave KE in rEF patients is suggestive of early and fixed impairment in diastolic function.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 3.