Right ventricle (RV) dysfunction is a frequent complication of acute respiratory distress syndrome (ARDS). Its more severe presentation, acute cor pulmonale (ACP), is defined at echocardiography as a dilated RV (end-diastolic RV/left ventricle area ratio > 0.6) associated with the presence of septal dyskinesia. The prevalence of ACP in non-Covid-19 related ARDS (NC-ARDS) has been evaluated to be 22% [95% confidence interval (CI) 19–25%] during the first 72 h of protective mechanical ventilation [1]. A clinical risk score has been proposed to select NC-ARDS patients at risk of ACP, including four variables: pneumonia as a cause of ARDS, elevated driving pressure, severe hypoxemia and severe hypercapnia [1]. RV dysfunction has been also reported in the setting of COVID-19-related ARDS (C-ARDS) [2], but the prevalence of ACP and the validity of ACP risk score in C-ARDS patients are still unknown. We performed an observational study in the medical ICU of Henri Mondor University Hospital (Créteil, France), from March 9th 2020 to March 9th 2021 to assess the prevalence and predictors of ACP in C-ARDS.

Continuous data are expressed as the mean ± standard deviation or median [25th–75th percentiles] and were compared using the Student t test or Mann–Whitney U test, as appropriate. Categorical variables, expressed as number and percentages, were evaluated using the chi-square test or Fisher’s exact test. To evaluate independent factors associated with ACP, significant or marginally significant (p < 0.10) bivariate risk factors (using the above-mentioned tests) were examined using univariate and multivariable backward stepwise logistic regression analysis. Coefficients were computed by the method of maximum likelihood. The calibrations of model was assessed by the Hosmer–Lemeshow goodness-of-fit statistic and discrimination by the area under the receiver operating characteristics curve.

Among 282 Covid-19 patients admitted in our ICU during the study period, 175 were intubated and ventilated for C-ARDS. Fifty-eight C-ARDS patients were excluded because they had no available echocardiographic data obtained within 72 h of initiation of invasive mechanical ventilation and the remaining 117 patients were included. In our cohort, the observed prevalence of ACP (44/117, 38%, 95% confidence interval 0.29–0.47) was higher than previously described for NC-ARDS. C-ARDS patients with ACP were less likely to have diabetes or chronic kidney disease (Table 1). They were not more likely to have a thorax computed tomography angiogram performed but, if they did have the exam, they were significantly more likely to present a pulmonary embolism (Table 1). On the contrary, there was no significant association between the presence of ACP and the ACP risk score or its components (Table 1). In multivariable analysis, pulmonary embolism was the only factor associated with ACP (Table 2). Including the ACP risk score in the model yielded similar results. Patients with ACP had a trend towards more extracorporeal membrane oxygenation and required tracheostomy more frequently, but had a similar mortality than their counterparts (Table 1).

Table 1 Characteristics and outcomes of patients with Covid-19 related acute respiratory distress syndrome, with or without acute cor pulmonale
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Table 2 Univariate and multivariable analysis for acute cor pulmonale in patients with Cocid-19 related acute respiratory distress syndrome
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Our study suggests that ACP is more prevalent in C-ARDS than previously reported in NC-ARDS, and is rather driven by pulmonary vascular obstruction in this group of patients than classical risk factors favoring vascular constriction/compression (hypoxemia, hypercapnia and driving pressure). Widespread pulmonary thrombosis with microangiopathy is a characteristic histological feature of C-ARDS [3, 4]. Pulmonary embolism is reported in up to 24% of critically-ill patients with C-ARDS [5]. Our data suggests that the presence of ACP may prompt the search of pulmonary embolism by a CT-scan in C-ARDS patients.

In conclusion, ACP seems more frequent and more related to pulmonary embolism in C-ARDS as compared to NC-ARDS. These observations need to be confirmed in larger studies.