Correlation Between RVOT VTI Measured via a Modified Subcostal View and LVOT VTI in Critically Ill Patients

Background Assessment of cardiac output by transthoracic echocardiography in critically ill patients commonly relies on measurement of the left ventricular outflow tract velocity‐time integral (LVOT VTI). However, obtaining an adequate apical view is not always possible in the intensive care unit. We evaluated whether right ventricular outflow tract velocity‐time integral (RVOT VTI), obtained from a modified subcostal view, correlates with LVOT VTI and whether it can identify patients with normal LVOT VTI values. Methods This was a post hoc analysis of a prospective diagnostic accuracy study performed in two mixed medical‐surgical intensive care units. Adult patients admitted between January and April 2022 were included when both RVOT and LVOT Doppler measurements were feasible. RVOT VTI was measured using a modified subcostal approach, whereas LVOT VTI was obtained from the apical five‐chamber view. Results Forty‐three patients were analyzed. RVOT VTI showed a strong positive correlation with LVOT VTI (Spearman r = 0.72, p < 0.0001). Bland–Altman analysis demonstrated a mean bias of −4.3 cm, with wide limits of agreement (−11.6 to +2.9 cm). The area under the receiver operating characteristic curve for predicting an LVOT VTI ≥ 17 cm was 0.934 (95% CI 0.815–0.970). An RVOT VTI > 14.6 cm predicted LVOT VTI ≥ 17 cm with 80.7% sensitivity (95% CI 62.5%–92.5%) and 100% specificity (95% CI 73.5%–100%). Conclusion RVOT VTI measured from a modified subcostal view may be a useful alternative when standard LVOT VTI assessment cannot be obtained in critically ill patients. Although both measurements should not be considered interchangeable, RVOT VTI may help identify normal forward flow and follow hemodynamic changes at the bedside.