Defining the physiological bounds of left ventricular ejection time with a wireless, wearable ultrasound: An analysis of over 137,000 cardiac cycles.

Background: Flow time (FT) or the left ventricular ejection time (LVET) is the duration of mechanical systole, when the aortic valve is open and ejecting blood. LVET can be measured in the common carotid artery from the time of the systolic upstroke to the incisural notch. FT is directly related to stroke volume (SV) and therefore has important implications for inpatient and outpatient cardiovascular care. Despite this known relationship between FT (i.e., LVET) and SV, large patient datasets describing the distribution and physiological bounds of FT are lacking. Methods: Using a wearable, continuous-wave Doppler ultrasound patch, we are amassing a database of cardiac cycles from the common carotid Doppler pulse in patients and healthy volunteers performing various preload challenges. Results: From this dataset of over 137,000 measurements in 347 patients, we report the mean and distributions of the common carotid artery flow time (i.e., LVET) corrected for heart rate using several prevailing equations. Conclusions: Our findings are the most extensive exploration of the physiological bounds of FT (i.e., LVET) and are useful in both clinical assessments of cardiac health and various algorithm detection applications.