Right Ventricular “Bubble Time” to Identify Patients With Right Ventricular Dysfunction

Abstract

ObjectiveWe propose a novel method of evaluating right ventricular (RV) dysfunction in the emergency department (ED) using RV “bubble time” – the duration of time bubbles from a saline flush are visualized in the RV on echocardiography. The objective was to identify the optimal cutoff value for RV bubble time that differentiates patients with RV dysfunction and report on its diagnostic test characteristics. MethodsThis prospective diagnostic accuracy study enrolled a convenience sample of hemodynamically stable ED patients. A sonographer administered a 10-milliliter saline flush into patient’s intravenous catheter, performed a bedside echocardiogram, and measured RV bubble time. Subsequently, the patient underwent a comprehensive cardiologist-interpreted echocardiogram with 36 hours, which served as the gold standard. Patients with RV strain or enlargement on the latter echocardiogram were considered to have RV dysfunction. Bubble time was evaluated by a second provider, blinded to the initial results, who reviewed the ultrasound clips. The primary outcome measure was the optimal cutoff value of RV bubble time that identifies patients with and without RV dysfunction. ResultsOf 196 patients, median age was 67 and half were female, with 69 (35.2%) having RV dysfunction. Median RV bubble time among patients with RV dysfunction was 62 seconds (interquartile range (IQR): 52, 93) compared with 21 seconds (IQR: 12, 32) among patients without (p<0.0001). The optimal cutoff value of RV bubble time for identifying patients with RV dysfunction was ≥40 seconds, with a sensitivity of 0.97 (95% CI: 0.93, 1.00) and specificity of 0.87 (95% CI: 0.82, 0.93). ConclusionIn ED patients, an RV bubble time of ≥40 seconds had high sensitivity in identifying patients with RV dysfunction, while an RV bubble time of <40 seconds had good specificity in identifying patients without RV dysfunction. These findings warrant further investigation in undifferentiated patient population and by emergency physicians without advanced ultrasound training.