Discussion
Our results demonstrated that RV dysfunction is an important clinical
feature in COVID-19 pneumonia patients with ARDS, which is related to
the severity of COVID-19 pneumonia and ARDS. Bedside echocardiography
allows an early integrated assessment of the RV function through the
evaluation of TAPSE. The echocardiographic parameters of RV function and
cardiac cavity in COVID-19 pneumonia patients show abnormity to
different extents compared to healthy subjects.
Viral pneumonia is the one of the most common causes for ARDS and is
associated with high morbidity and mortality worldwide, such as SARS,
H1N1 flu and so on [13-15]. RV dysfunction is frequently presented
in these patients, and leads to left-right asymmetry of the heart, which
can worsen hemodynamic stability and is associated with a poorer
prognosis [6, 16, 17]. In our study, a higher incidence of RV
dysfunction was found in critically severe group who had more severe
ARDS patients, which is similar to that in the severe ARDS population
caused by SARS and H1N1 viruses [15, 18, 19]. Thus, RV dysfunction
is common in viral pneumonia patients, especially in patients with
severe ARDS.
TAPSE, as the most commonly used index for evaluating RV function, has
been widely used in patients with ARDS [20]. A TAPSE less than 17 mm
was recommended as a major parameter of RV dysfunction by ASE
guidelines. In present study, we found the TAPSE in patients with
COVID-19 pneumonia was significantly decreased compared to healthy
people, and the proportion of patients with TAPSE <17 mm was
significantly higher in critically severe patients (35.7%) than that in
severe patients (8.6%), indicating that there was a correlation between
the occurrence of RV dysfunction and the severity of COVID-19 pneumonia.
Patients in critically severe group appeared to be more severely ill in
terms of APACHE II, decreased MAP and increased HR. Moreover, invasive
ventilation and vasopressors are frequently required in these patients.
The function of the RV is to keep proper pulmonary perfusion pressure
and systemic venous pressure to maintain normal blood flow [21]. The
main factors affecting the RV function in patients with ARDS are
impaired RV contraction and increased pulmonary vascular resistance. It
is known that the increase of pulmonary vascular resistance may be
induced by vasoconstrictor, hypoxemia, hypercapnia, acidosis and so on,
which cause the deterioration of right heart structure and function
[22-24]. Recent studies have shown that the clinical characteristics
of severe and critically severe COVID-19 pneumonia patients are severe
hypoxemia, hypercapnia and microthrombosis, which may lead to the
increase of pulmonary vascular resistance [3-5].
In our study, the values of TRPG and PASP were higher than normal ranges
and increased in COVID-19 pneumonia patients. Although the majority of
patients in critically severe group received mechanical ventilation,
there were no significant differences in TRPG and PASP between the
severe and critically severe patients. This may be because pulmonary
vascular resistance is reduced by positive pressure mechanical
ventilation and is not seriously deteriorated in the early stages of the
disease [25-27]. The right heart had a poor ability to regulate
pressure load [16]. In this study, the right heart cavity and
pulmonary artery were enlarged soon after the increase of pulmonary
vascular resistance in patients with COVID-19 pneumonia.
Patients with critically severe COVID-19 pneumonia are often accompanied
by organ dysfunction and shock. The results of the present study have
shown that both RV and left ventricular systolic function in critically
severe patients with COVID-19 pneumonia are impaired. The hemodynamic
instability of decreased LVEF and MAP is associated with more severe RV
dysfunction, which present significantly decreased TAPSE, enhanced
diameters of IVC and reduced ICV-CI. Therefore, the monitoring and
protection of right ventricular function need to be strengthened in the
management of patients with COVID-19 pneumonia.
There are limitations in the present study. This is a retrospective
study with limited sample size. The results need to be further confirmed
by prospective clinical studies. In addition, although the assessments
of echocardiography were performed by ultrasonologist, it became more
challenged and difficult than usual to obtain parameters since
three-level isolation and protection measures must be taken when
contacting patients with COVID-19 pneumonia. However, in this case,
echocardiography is the most important bedside examination method for
evaluation of patients with COVID-19 pneumonia.