Discussion
TTE is the main imaging technique to investigate LV structure and functions, but conventional echocardiographic techniques may not be enough to show the pre-clinic mechanical deterioration. 2D-STE is a better method for evaluating regional and global myocardial deformation and can diagnose subclinical myocardial dysfunction earlier and may detect patients who needs further investigations, cardiac controls, and myocardial protection (11-14).
In our study we evaluated the difference of left ventricular myocardial functions with LV-GLS between asymptomatic and symptomatic patients who had mild COVID infection. Życzkowska et al also investigated mild COVID infection’s effects in heart functions including standard and advanced echocardiographic techniques but the result of the study did not show significant impairment in left ventricle functions (20).
The real prevalence of the cardiac involvement is not clear, and the study results are conflicting. It can be speculated that these results may be related with the study populations. In a study from a single tertiary centre, Erdol et al evaluated 100 consecutive COVID-19 proven patients after quarantine period with CMR and cardiac involvement was detected in 49 patients in which 41 patients described cardiac symptoms that were not present before COVID infection, and the results were statistically significant (p=0,001). In 24 patients out of 51 who does not have cardiac involvement in CMR were asymptomatic and this result was also statistically significant (p=0,001) (21).
As it’s known that the 2D-STE and CMR results are compatible with each other, 2D-STE for LV quantification has been validated against MRI (22). Puntmann at al. evaluated left ventricle with CMR after mild COVID infection without known cardiac disease and showed more diffuse myocardial edema at follow-up in patients with ongoing symptoms as compared to the ones who has improved. They also investigated the LV-GLS values between the control and post-COVID patients and even though the average values of LV-GLS were in normal ranges in both groups, the difference was statistically different (23). In our study, even the average LV-GLS value was lower in the symptomatic group, the difference was not statistically different.
In another hybrid study using both TTE, 2D-STE and CMR, Brito et al. evaluated young athletes who had mild to moderate degree COVID-19 infection. Even no athlete showed ongoing myocarditis imaging features, the result of this study shows that mild or asymptomatic COVID-19 is not a benign illness, as more than one-half of the younger individuals showed subclinical myocardial and pericardial disease (24). The reduction of LV-GLS values is seemed to be obtained mostly in symptomatic patients or in patients who have an additional finding as pericardial involvement, and it is independent of the COVID-19 disease severity.
The limitations of our study are, it’s a single centre retrospective study and the GLS values of our study population are not known before the COVID infection, and the number of the study population is low because we have stopped including patients after August 2021, the date that the m-RNA vaccines are applied to the general population in Turkey to avoid the effects of m-RNA vaccine’s myocardial damage and myocarditis side effect.
Conclusion
Despite the small number of the patients in the study group, the results of this study show that more symptomatic patients than the asymptomatic ones have impaired LV-GLS values. Even if it is not statistically significant, the mean LV-GLS values are also reduced in symptomatic patients after mild COVID-19 infection. It can be concluded that close follow-up of these patients in the future may be beneficial until randomized controlled studies with high numbers of patients are conducted.