2D Parameters of Left Ventricular Size
This meta-analysis demonstrated that half of the studies featured quantifiable changes in LV end-diastolic diameter, a marker of structural myocardial remodeling, thus potentially useful as a discriminator between myocarditis and control populations although not strong. Measurement of LV diameter was demonstrated to have the lowest overall effect size when compared to the parameters of LV function which was consistent with the notion that measures of LV function being more sensitive for the detection of underlying myocardial pathology compared to measures of LV structural change(20). Identification of increased LV diameter may also be reflective of the chronicity of disease hence effective in distinguishing more chronic or fulminant myocarditis, which would also be more likely to have other echocardiographic abnormalities such as regional wall motion abnormalities and impaired LV systolic function, as demonstrated in two of the included studies (13, 14).
Only four out of the six studies included in this systematic review reported LV volumes with only one study reporting significant differences in indexed volumes. The heterogeneity in the methodology for the assessment of LV volumes did not allow for meta-analysis of this parameter although it is postulated that LV volume changes would provide a more accurate reflection of LV structural change compared to linear measurements of LV size changes. Moreover, current guidelines do not recommend use of LVEDD for routine quantification of LV size but indexed volumes instead. Whilst LV dilatation has been hypothesized to be associated with an increased risk of heart failure, LV volumes have been shown to more accurately reflect LV remodeling, in comparison to single dimensional assessment (21, 22). One study did demonstrate that indexed left ventricular end-diastolic volumes were greater in their cohort of myocarditis patients compared to controls consistent with expectations. However, the remaining studies reporting non-indexed LV volumes did not demonstrate any significant differences between myocarditis populations and controls. This finding is largely thought to be attributed to the non-indexation of LV volumes, limiting its precision and accuracy.