Strain analysis reveals subtle systolic dysfunction in confirmed and suspected myocarditis with normal LVEF. A cardiac magnetic resonance study

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. Graphic abstract