Bridging the gap: hybrid cardiac echo in the critically Ill.

BACKGROUND: Point-of-care ultrasound (POCUS) often includes cardiac ultrasound (CU). It is commonly used to evaluate cardiac function in critically ill patients, but lacks the specific quantitative anatomic assessment afforded by standard transthoracic echocardiography (TTE). We developed the Focused Rapid Echocardiographic Evaluation (FREE) - a hybrid between a CU and TTE that places an emphasis on cardiac function rather than anatomy. We hypothesized that data obtained from FREE correlates well with TTE while providing actionable information for clinical decision-making.

METHODS: FREE exams evaluating cardiac function (left ventricle (LV) ejection fraction (EF), diastolic dysfunction (including early mitral Doppler flow (E) and early mitral tissue Doppler (E'), right ventricular (RV) function, cardiac output, preload (LV internal dimension end diastole (LVID)), stroke volume (SV), stroke volume variation (SVV), inferior vena cava (IVC) diameter and IVC collapse were performed. Patients who underwent both a TTE and FREE on same day were identified as the cohort and quantitative measurements were compared. Correlation analyses were performed to assess levels of agreement.

RESULTS: 462 FREE exams were performed, of which 69 patients had both a FREE and TTE. FREE EF was strongly correlated with TTE (r= 0.89, 95% CI). LVOT, LVID, E, and Lateral E' derived from FREE were also strongly correlated with TTE measurements (r=0.83, r=0.94, r=0.77, r=0.88 respectively). In 82% of patients, RV function for FREE was the same as reported for TTE; pericardial effusion was detected on both exams in 94% of cases. No significant valvular anatomy was missed with the FREE exam.

CONCLUSIONS: Functional rather than anatomically based hybrid ultrasound exams, like the FREE, facilitate decision making for critically ill patients. The FREE's functional assessment correlates well with TTE measurements, and may be of significant clinical value in critically ill patients, especially when employed in remote operating environments where resources are limited.

LEVEL OF EVIDENCE: Level 2, Diagnostic Test.