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Published on: April 13, 2015
Carotid flow as a surrogate of the left ventricular stroke volume
Issac Cheong1,2, Victoria Otero Castro3, Fernando Ariel Sosa4,5
1Department of Critical Care Medicine, Sanatorio de los Arcos, Buenos Aires, Argentina. issac_cheong@hotmail.com.
Insights
Measuring carotid flow velocity-time integral (VTI) can serve as a surrogate for left ventricular outflow tract (LVOT) VTI in critical care patients. This novel technique offers a potential alternative for hemodynamic monitoring when echocardiography is challenging.
Area of Science:
- Critical Care Medicine
- Cardiovascular Physiology
- Diagnostic Imaging
Background:
- Transthoracic echocardiography (TTE) is essential for hemodynamic monitoring in intensive care units (ICUs).
- Left ventricle stroke volume assessment via LVOT VTI can be difficult in ICUs due to challenging views.
- A reliable surrogate for LVOT VTI is needed for continuous hemodynamic assessment in critical patients.
Purpose of the Study:
- To evaluate the utility of carotid flow velocity-time integral (VTI) as a surrogate for left ventricle outflow tract (LVOT) VTI.
- To assess the correlation and agreement between carotid flow VTI measurements and LVOT VTI in critically ill patients.
Main Methods:
- Observational, prospective, simple-blind study conducted in ICUs.
- Measured carotid systodiastolic flow (CSD) VTI and carotid systolic flow (CS) VTI at the left supraclavicular fossa.
- Compared carotid flow VTI measurements with LVOT VTI obtained via TTE in 43 subjects.
Main Results:
- Strong Spearman's correlation observed between LVOT VTI and CS VTI (0.81) and between LVOT VTI and CSD VTI (0.89).
- Bland-Altman analysis showed a bias of -0.2 cm for CSD VTI versus LVOT VTI, with a percentage error of 37.9%.
- CSD VTI could not be considered interchangeable with LVOT VTI but demonstrated potential as a surrogate.
Conclusions:
- Carotid flow VTI, particularly CSD VTI, shows significant correlation with LVOT VTI in critical care settings.
- While not interchangeable, carotid flow VTI may serve as a valuable surrogate for LVOT VTI when echocardiography is limited.
- This novel technique offers a promising, non-invasive approach for hemodynamic monitoring in intensive care.
Abstract:
Transthoracic echocardiography (TTE) is a fundamental tool for hemodynamic monitoring in critical patients. It allows evaluating the left ventricle's stroke volume based on the measurement of the velocity-time integral (VTI) of the left ventricle outflow tract (LVOT). However, in the intensive care unit obtaining adequate echocardiographic views may present a challenge. We propose to measure, as a surrogate of the stroke volume, the carotid flow with a novel technique. This is an observational, prospective, and simple blind study, conducted in the intensive care unit of Sanatorio de los Arcos and Hospital Aleman, in Buenos Aires, Argentina. We measured the carotid systodiastolic flow (CSD) VTI and the carotid systolic flow (CS) VTI at the level of the left supraclavicular fossa and we compared it with the LVOT VTI obtained by TTE. We evaluated 43 subjects. Spearman's correlation coefficient between LVOT VTI and CS VTI was 0.81 (95% CI 0.67-0.89) and between LVOT VTI and CSD VTI was 0.89 (95% CI 0.81-0.94). The Bland-Altman method analysis of the 5-chamber apical window LVOT VTI compared to the CSD VTI showed a bias of - 0.2 (95% CI - 0.82 to 0.43), with a concordance interval between - 4.2 (95% CI - 5.2 to - 3.1) and 3.8 cm (95% CI 2.7 to 4.9). The percentage error was 37.9%. Almost 100% of the values fell within the concordance limits, and no trend was observed in bias across the spectrum of mean variables. Although the CSD VTI could not be interchangeable with the LVOT VTI, it could be considered as its surrogate.
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