Right Ventricular Dysfunction in COVID-19 ECMO-A Red Herring or the Real Deal?

To the Editor:

The morphologic and functional changes to the right ventricle seen in patients with coronavirus disease 2019–related acute respiratory distress syndrome (COVID-19 ARDS) requiring venovenous extracorporeal membrane oxygenation (VV-EMCO) are not well-understood. We read with interest the recent study by Lazzeri et al. describing a single-center case series of 35 consecutive patients requiring VV-ECMO for COVID-19 ARDS. We commend the authors for describing the temporal course of right ventricular dysfunction during VV-ECMO therapy for COVID-19 ARDS. A key strength of their study was the use of serial echocardiograms performed before, during, and after VV-ECMO implantation. The study provided important insight to evolution of right ventricular dysfunction in COVID-19 ARDS with and without VV-ECMO.

Our group's own pilot study also explored this same phenomenon. We found that performing point-of-care ultrasound examinations to evaluate right ventricular function in COVID-19 ARDS patients on VV-ECMO is feasible and reproducible. As noted by Lazzeri et al., our study was limited by the lack of serial echocardiographic assessments. However, the authors’ own study also had an important limitation; namely, only using three echocardiographic parameters to describe the right ventricle: right ventricular end-diastolic area, right ventricular-to-left ventricular end-diastolic area ratio, and tricuspid annular plane excursion (TAPSE). Considering the extensive list of echocardiographic indices for right ventricular function, the question arises which measurements yield the most predictive information in a given clinical setting. Recommended right ventricle size evaluation includes right ventricle basal, mid-chamber, and longitudinal end-diastolic diameters obtained from the four-chamber right ventricle–focused view; however, the right ventricular-to-left ventricular end-diastolic area ratio is not routinely used. Additionally, TAPSE is only one of the currently recommended measurements used to describe right ventricular function. The cutoff TAPSE value of 15 mm used in the study was inconsistent with the current guideline recommendation of 17 mm. As a result, the authors may have underreported less severe right ventricular dysfunction by choosing a lower-than-recommended TAPSE cutoff value. The authors could have validated their limited data by including fractional area change, systolic velocity of the lateral tricuspid annulus, three-dimensional right ventricular ejection fraction, and right ventricle free-wall longitudinal strain. When comparing the echocardiographic findings between our two high-volume COVID-19 ARDS ECMO centers, an abnormal TAPSE was associated more strongly with right ventricular dysfunction in Lazzeri's study than it was in ours. Interestingly, we found right ventricular free-wall longitudinal strain and fractional area change to be more sensitive than TAPSE in patients with COVID-19 ARDS on VV-ECMO. Given the propensity for right ventricular dysfunction in ARDS, predominantly secondary to high right ventricular afterload, right ventricular free-wall longitudinal strain is perhaps a better modality for assessing myocardial contractility and systolic function in this patient population, considering that it is relatively load-independent.

The results of Lazzeri et al. bring us closer to understanding right ventricular pathology in patients with COVID-19 ARDS requiring VV-ECMO. The authors provided much-needed data on right ventricular function over the course of VV-ECMO therapy. They convincingly illustrated that one-half of the patients who died exhibited concomitant right ventricular failure, while survivors had reductions in pulmonary artery pressures. Additionally, as illustrated before the COVID-19 pandemic and by the authors, initiation of VV-ECMO tends to improve right ventricular function, as it did in one-third of patients in this cohort within the first 24 hours of VV-ECMO therapy. Furthermore, protracted therapy with ECMO in patients with COVID-19 increases the risk of right ventricular failure development, which likely has a negative effect on mortality. The questions that remain for future study are (1) how is right ventricular function affected by prolonged VV-ECMO therapy for COVID-19 ARDS? and (2) how does right ventricular failure effect the mortality in these patients?

Conflict of Interest

None of the authors has any conflicts of interest to report.

No funding from the National Institutes of Health, Howard Hughes Medical Institute, or any other financial source was received for conducting this study.