Aims: Lake Louise Criteria (LLC) are time-dependent and some acute myocarditis (AM) with preserved left ventricular ejection fraction (LVEF) could be missed, due to the limited accessibility of Cardiac Magnetic Resonance (CMR). We aimed to assess the potential value of cardiac strain measured by feature tracking (FT) imaging in this population.
Methods and results: Eighty-three patients with clinically suspected AM and normal LVEF were divided into 39 "confirmed AM" (positive LLC) and 44 "suspected AM" (negative LLC). An age and gender-matched sample of 42 normal subjects underwent CMR. In all groups, FT-derived biventricular strains and STE- global longitudinal strain (GLS) were assessed, being regularly measurable. Strain values < 5th percentile of the control group were considered abnormal. "Suspected" and "confirmed" AM were similar, except for medium time of CMR evaluation (5.2 vs 1 months from presentation, respectively; p = 0.004). Compared to healthy controls, both "suspected" and "confirmed" AM showed significantly impaired strain values. LV-global circumferential strain (GCS), right ventricular GCS and LV-GLS were abnormal in 15.4% and 15.9%, 20.5% and 15.9%, 7.7% and 9.1% in "confirmed" and "suspected" AM, respectively. STE analysis confirmed the results on LV-GLS, however a weak correlation emerged between STE and CMR-FT LV-GLS (p = 0.08).
Conclusions: Compared to STE, CMR-FT analysis provided a more comprehensive and complementary biventricular strain evaluation that resulted similar in "confirmed" and "suspected" AM with normal LVEF. Conversely, mostly biventricular GCS was significantly reduced in up to 20% of patients, compared to healthy controls.
Keywords: Circumferential strain; Feature tracking imaging; Longitudinal strain; Multiparametric approach; Myocarditis; Normal left-ventricular ejection fraction.