3.3 The cardiac function in severe patients with COVID-19 during
follow-up
There was no statistical difference in the size of both atria and
ventricle, thickness of interventricular septum, left ventricular
posterior wall, diameter of aorta and pulmonary between the baseline and
follow-up results. No difference was also observed in left ventricular
systolic function (LVEF) and diastolic function (E/e’), LAEF, IVC
collapse rate and systolic (TAPSE, TDI-S) function of right ventricle.
(Table 5)
The GCS of left ventricle was significantly higher
(P< 0.05) at follow-up when compared with baseline.
However, there was no statistical difference in LV GLS of severe
patients at baseline and follow-up, neither in LA GLS (Table 6).
Only 10 severe patients received echocardiography examination more than
7 times during hospitalization. The patient number was small, thus we
drew a line chart to show the strain in left atrium and left ventricle.
The results showed that the LA GLS, LV GCS and LV GLS tended to rise
gradually. (Figure 3).
Discussion
Acute myocardial injury has been demonstrated in 7.2%-12% of patients
with COVID-19 in preliminary reports, with a higher prevalence among
those requiring intensive care 10. Mortality data from
44672 cases of COVID-19 released by the Chinese Centre for Disease
Control and Prevention demonstrate that patients with cardiovascular
comorbidities show a much higher mortality11.
But there still lack a systematic and comprehensive study including mild
and severe patients in the assessment of left ventricular, left atrial
and right ventricular function.
The aim of the present study was to evaluate the cardiac function by
standard and strain echocardiography including mild and severe patients
with COVID-19. We observed that: 1. Both mild and severe COVID-19
infected patients showed reduced left ventricular diastolic function
compared with control group; 2. Severe patients with COVID-19 exhibited
exacerbated right ventricular systolic function; 3. Both mild and severe
patients with COVID-19 showed impaired left ventricular strain, and the
strain in severe patients even worse, suggesting all the patients may
had early systolic function. 4. The strain in apical segment of mild
patients with COVID-19 was elevated compared with basal and middle
segment. 5.There was a negative correlation between LV GLS and log
TnT-hs, as well as NT-pro BNP. 6. The EF value and strain of left atrium
of mild and severe patients with COVID-19 decreased; 7.LV GLS, LV GCS
and LA GLS might predict the severity of COVID-19. 8. In the follow-up
of severe COVID-19 infected patients, their cardiac structure and
function had no change, while left atrial and ventricular strain
exhibited an increased trend.
In the present study, there was no difference in the size of LV and
LVEF, among the 3 groups. IVS and LVPW in severe patients with COVID-19
were thicker than mild patients and the controls. There were 8 severe
patients with hypertension. However, only one mild patient with
hypertension. That might contribute to thicker IVS and
LVPW12. In addition, the age may also have an effect
on this cardiac performance13. In our investigation,
E/e’ in severe patients with COVID-19 were higher than mild and control
groups, probably suggesting elevated LV filling pressure. Furthermore,
no difference in RV among the 3 groups. TDI-s and TAPSE, the index of
right ventricular systolic function, in severe patients were lower than
that in the other two groups, suggesting right ventricular systolic
dysfunction, which was seen, particularly in the context of severe
parenchymal lung disease and acute respiratory
disease13. Previous study also demonstrated that
compared with survivors, nonsurvivors displayed enlarged right heart
chambers, diminished RV function, and elevated pulmonary artery systolic
pressure.14 7 of 17 (42%) needed prone positioning
for severe Hypoxia had RV dysfunction(RV FAC < 35%).15
LA is considered to modulate left ventricular filling and cardiovascular
performance as (i) a reservoir for pulmonary venous return during
ventricular systole,(ii) a conduit for pulmonary venous return during
early ventricular diastole, and (iii) a booster pump that augments
ventricular filling during late ventricular diastole.16LA size is strong predictor of cardiovascular morbidity and
death17.LA size correlates with both LA and left
ventricular(LV) function. Previous study found no difference in LA
dimension between survivors and nonsurvivors with
COVID-1914, and there is still lack of study on left
atrial strain for now. In our study, higher LA volume and lower LAEF
were observed in severe and mild patients with COVID-19 than control
group. Further, LA myocardial deformation is assessed as global
longitudinal strain. 18In addition, the results showed
that LAGLS decreased in severe and mild patients, suggesting the LA
systolic dysfunction. All LA volume, LAEF and LAGLS showed LA systolic
dysfunction, contributing to LV dysfunction.
Strain image is superior to standard echocardiography for myocardial
injury detection in patients and reflects the complex deformation
pattern of the heart during systole19. Previous study
showed that LV GLS measurement are stable and repeatable, which have
additional predictive value for evaluating the rest cardiac function of
patients.20 The normal LV GLS measured by Qlab is
18.9±2.5%21. Though there was no significant change
in LVEF and LV volumes, significantly lower LV GLS and LV GCS were
observed in severe and mild patients with COVID-19 compared with control
group, especially in severe group. Although in severe patients, 2
patients with coronary heart disease and 1 with chronic heart disease
may contribute to worse GLS. Patients with hypertension may also lead to
lower GLS22. This result showed subclinical cardiac
systolic dysfunction in patients with COVID-19. Troponin and NT-pro BNP
is a widely accepted biomarker of myocardial injury, and elevated serum
levels have been a notable feature during recent epidemics of
respiratory virus infections.20Accordingly, we
observed the troponin and NT-pro BNP were negatively correlated with LV
GLS in severe patients. Previous data indicated a decreased myocardial
longitudinal strain in fulminat myocarditis especially decreased in the
basal and middle segments4,23,which was similar to our
results, our results observed the apical LS in mild patients was higher
than middle and basal segment, however, no significant difference among
basal, middle and apical LS,CS in severe patients, as shown in table 4.
Previous study showed that GLS can predict functional capacity in
patients with preserved LVEF heart failure and to assess prognosis in
reduced LVEF heart failure24. And it could classify HF
patients according to the functional capacity.25 In
this study, we found that GLS had a low predicted value of the disease
severity, which may stratify the patients with unknown condition and
therefore to deserve more differentiated treatment.
In our study, only 13 severe patients in ICU received echocardiography
one more time. Compared with the first examination, no change in cardiac
structure on follow-up. For the strain, our results showed only LV GCS
increased (30.40±7.51 vs 23.05±8.56, P< 0.05) in severe
patients when compared with the first echocardiography, while the LV GLS
and LA GLS exhibited an increased trend. Furthermore, the line chart
based on 10 patients for 16 days also showed steadily rising trend.
Alleviating myocardial injury was implied, although which needed longer
observation. Previous study showed cardiac impairment caused by SARS-CoV
in the more critically ill patients may be reversible on
recovery26.
Study Limitations
Outbreak of COVID-19 was abrupt, the study was an observational, ’not
well-designed’ one in highly contagious COVID-19 patients, lasting only
16 days. The study population number in our study was small.
Conclusions
These findings suggested that left
ventricular performance was subclinically impaired during COVID-9
infection irrespective of infection severity and the strain of LV and LA
may predict the disease severity. The cardiac function had an increasing
trend for severe patients treated in ICU. Whether the myocardial injury
may be reversible on clinical recovery needs longer follow-up.