Left Ventricular Systolic Function
The importance of a baseline echocardiogram during the acute-phase of
myocarditis is important as it allows for appropriate classification
between severe and non-severe myocarditis, based on preservation of
LVEF. This is important as these populations exhibit different
pathologic changes, disease states and clinical outcomes(23). Impairment in LV systolic
function in patients with myocarditis is attributed to a greater
percentage of myocardial involvement secondary to an inflammatory
myopathic process, which is consistent with the immune checkpoint
inhibitor (ICI) myocarditis(24). As a result, there is
development of regional and/or global systolic dysfunction, which is
typically seen in more severe forms of myocarditis, such as
immune-mediated myocarditis. Two of the included studies in this
meta-analysis demonstrated no significant differences in LVEF between
myocarditis and control populations, both in the initial phase(17), and on a follow-up at a
mean period of 22 months, highlighting the heterogeneous nature of this
disease process (15).Interestingly, the majority of patients with myocarditis in this
systematic review had a normal LVEF. Only one study demonstrated an
impaired mean LVEF in the myocarditis population. This study focused on
patients with ICI myocarditis secondary to checkpoint inhibition
chemotherapy (13).
This study also reinforces the value of LV-GLS in differentiating cases
of both severe and non-severe myocarditis in both the acute- and
sub-acute disease states. All included studies clearly demonstrated
significantly lower LV-GLS values in myocarditis populations, compared
to controls suggesting that LV-GLS may be a more sensitive marker of LV
systolic function compared to LVEF. LV-GLS was shown to be directly
associated with degree of myocardial inflammation, and diagnostic of
regional myocardial fibrosis, when correlated with CMR(16). In some longitudinal
studies, LV-GLS was shown also shown to remain impaired on follow-up(17) , which highlights the value
of LV-GLS as a potential marker for monitoring and diagnosing chronic
myocarditis or response to treatment.
The main advantages of LV-GLS compared to standard echocardiographic
parameters in assessment of myocarditis, are the signal-to-noise ratio,
angle independence and ability to differentiate between active and
passive myocardial segmental motion(25). LV-GLS has recently
emerged as a measure of cardiac function which is sensitive in detecting
subclinical cardiac injury relative to LVEF and has been shown to have
prognostic value in multiple pathologies