Right Ventricular Strain Is Common in Intubated COVID-19 Patients and Does Not Reflect Severity of Respiratory Illness

Abstract

Background: Right ventricular (RV) dysfunction is common and associated with worse outcomes in patients with coronavirus disease 2019 (COVID-19). In non-COVID-19 acute respiratory distress syndrome, RV dysfunction develops due to pulmonary hypoxic vasoconstriction, inflammation, and alveolar overdistension or atelectasis. Although similar pathogenic mechanisms may induce RV dysfunction in COVID-19, other COVID-19-specific pathology, such as pulmonary endothelialitis, thrombosis, or myocarditis, may also affect RV function. We quantified RV dysfunction by echocardiographic strain analysis and investigated its correlation with disease severity, ventilatory parameters, biomarkers, and imaging findings in critically ill COVID-19 patients.

Methods: We determined RV free wall longitudinal strain (FWLS) in 32 patients receiving mechanical ventilation for COVID-19-associated respiratory failure. Demographics, comorbid conditions, ventilatory parameters, medications, and laboratory findings were extracted from the medical record. Chest imaging was assessed to determine the severity of lung disease and the presence of pulmonary embolism.

Results: Abnormal FWLS was present in 66% of mechanically ventilated COVID-19 patients and was associated with higher lung compliance (39.6 vs 29.4 mL/cmH2O, P = 0.016), lower airway plateau pressures (21 vs 24 cmH2O, P = 0.043), lower tidal volume ventilation (5.74 vs 6.17 cc/kg, P = 0.031), and reduced left ventricular function. FWLS correlated negatively with age (r = -0.414, P = 0.018) and with serum troponin (r = 0.402, P = 0.034). Patients with abnormal RV strain did not exhibit decreased oxygenation or increased disease severity based on inflammatory markers, vasopressor requirements, or chest imaging findings.

Conclusions: RV dysfunction is common among critically ill COVID-19 patients and is not related to abnormal lung mechanics or ventilatory pressures. Instead, patients with abnormal FWLS had more favorable lung compliance. RV dysfunction may be secondary to diffuse intravascular micro- and macro-thrombosis or direct myocardial damage.

Trial registration: National Institutes of Health #NCT04306393. Registered 10 March 2020, https://ichgcp.net/clinical-trials-registry/NCT04306393.

Keywords: COVID-19; acute respiratory distress syndrome; cardiac dysfunction; right ventricle; strain.

Conflict of interest statement

Declaration of Conflicting Interests: The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: LB receives salary support from K23 HL128882/NHLBI NIH as principal investigator for his work on hemolysis and nitric oxide. LB receives technologies and devices from iNO Therapeutics LLC, Praxair Inc., Masimo Corp. LB receives funding from a Fast Grant for COVID-19 research at Mercatus Center of George Mason University and from iNO Therapeutics LLC. BPL is a textbook associate editor and author for Elsevier, Inc. and receives royalties. JKC reports grants from GE Healthcare, non-financial support from AWS, and grants from Genentech Foundation outside of the submitted work.

Figures

Figure 1.

Correlations between right ventricular free wall longitudinal strain (FWLS) and patient characteristics. FWLS negatively correlated with age (A), high-sensitivity troponin level at the time of ICU admission (B) and left ventricular (LV) outflow tract velocity time integral (C), a marker for cardiac stroke volume. In terms of respiratory parameters, FWLS negatively correlated with (D) airway plateau pressure and (E) tidal volume, while FWLS positively correlated with (F) lung compliance.

Figure 2.

Patients with normal and abnormal right ventricular free wall longitudinal strain (FWLS) had similar COVID-19 lung disease severity scores on chest radiographs (PXS score) and different rates of pulmonary embolism on CT imaging. A) Histogram comparing mean PXS scores ± standard deviation between patients with normal and abnormal FWLS. B) Patients with abnormal FWLS had a higher rate of pulmonary embolism detected on CT imaging. C) Illustrative examples above from a patient with normal FWLS (left panel) and abnormal FWLS (right panel) show patchy bilateral airspace opacities. The PXS scores of 8.0 and 8.4 reflect moderate radiographic disease severity.