Discussion:
The present prospective study evaluated the presence of myocardial
injury and subclinical myocardial dysfunction using CMR in COVID-19
recovered subjects. The major findings of our study were the presence of
abnormal CMR in 16 (53.3%) patients who had recently recovered from
COVID-19. A significant proportion of patients had either raised T2
(40%) and/or LGE (33.3%). These findings persisted even on follow-up
(13.3% of patients had abnormal CMR scan at six months). These findings
are important as myocardial injury and subclinical cardiac involvement
is not well elucidated and is often overlooked in patients who have
recovered from COVID-19 infection. The authors have earlier reported
sub-clinical left ventricular dysfunction in one-third of COVID-19
recovered subjects using speckle tracking echocardiography.
There is a limited data regarding the role of CMR in COVID-19 recovered
patients. Previous studies have reported the prevalence of abnormal CMR
findings in COVID-19 recovered subjects to be ranging between 1.4% and
78%.8-12 This marked degree of heterogeneity can be
explained based on the differences in population studied (asymptomatic
to severe COVID) and varying methods for detection of myocardial injury
(conventional CMR sequences such as LGE and T2WI versus native T1 and T2
measurements). In a study from China, among 26 COVID-19 recovered
subjects, myocardial edema was reported in 14 (54%) while 8 (31%)
patients had LGE.9 However, the authors had included
patients recovering from moderate or severe COVID-19 illness and
utilized only conventional MR sequences such as LGE and T2WI for
detection of myocardial damage. Previous small studies have reported
variable myocardial inflammation in heterogenous group of
patients10,11. Major limitation was either the absence
of a control group or inclusion of large number of patients with various
comorbidities such as diabetes mellitus, hypertension, coronary artery
disease that may have otherwise contributed to the ongoing inflammation.10,11Our study addresses all the previous limitations
including incorporation of both the conventional parameters such as LGE
and T2WI as well as T1 and T2 mapping.
Findings on CMR in our study included the presence of myocardial edema
and or LGE in more than 50% of the patients recovering from COVID-19
infection. Additionally, our results showed that the myocardial T1 and
T2 values were higher in COVID-19 patients as compared to healthy
controls. In our study, elevated T1 was reported in 53.3% while raised
T2 was reported in 40% subjects. These findings are concurrent to those
in previous studies 9-12. Prior studies have
documented that elevated T2 values corresponds to areas of myocardial
edema while elevated T1 values reflect development of myocardial
interstitial fibrosis.16,17 These findings often
reflect the inflammatory damage to the myocardium during active COVID-19
infection or an ongoing low-grade localized inflammation during the
convalescent phase. Additionally, myocardial edema could be due to
increased vascular permeability which is mediated by the endothelial
angiotensin converting enzyme (ACE-2).18 In subjects
with viral myocarditis, edema and LGE commonly occurs in the inferior
and inferior-lateral wall with most of the lesions being patchy
sub-epicardial in nature.19 Similar findings were
observed in our study too where the predominant distribution of LGE was
sub-epicardial involving inferior and infero-septal segments at base and
mid-LV cavity level. Severity of the initial COVID-19 infection has an
important bearing on findings on CMR. Severe COVID-19 patients with
higher levels of inflammatory markers and greater immune mediated
myocardial damage often have significantly higher T1 and T2 values as
compared to those with mild and moderate COVID-19
infection.11
In our study, COVID-19 recovered patients had evidence of right
ventricular (RV) dysfunction on CMR as compared to healthy controls.
Previous studies using CMR and echocardiogram have reported RV
dysfunction among COVID-19 survivors.4,9,20 Most of
this has been attributed to development of pulmonary fibrosis following
lung injury and ARDS in COVID-19 recovered subjects. This often results
in increased pulmonary vascular
resistance, raised systolic pulmonary arterial pressure with an
increased RV afterload along with hypoxia and oxidative
stress.21,22
Though use of CMR as a routine investigation in COVID-19 recovered
patients is not possible, but it did provide some important insights and
serves as an important tool in detection of viral myocarditis and
sub-clinical left ventricular dysfunction. Since, inflammation, LGE and
fibrosis plays an important role in the development of dilated
cardiomyopathy, it becomes all the more prudent to follow-up these
patients with an abnormal baseline CMR. There is limited data regarding
follow-up CMR imaging in recovered COVID-19 patients. The present study
reported abnormal follow-up CMR in 4/16 (25%) with LGE persisting in 3
while one had a raised myocardial T2 value. Earlier reports showed
complete resolution of both T2 abnormalities and LGE in 11/27 athletes
(40.7%) while 16 athletes (59.3%) still had persistent
LGE.23