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Low RVO or LVO if <150 mL/kg/min
"WHAT IS A NORMAL LEVEL OF CARDIAC OUTPUT? A ventricular output of 150 to 300 mL/kg/min is considered normal in (pre)term infants without transductal or interatrial shunting. A ventricular output less than 150 mL/kg/min or SVCf less than 40 to 45 mL/kg/min is associated with adverse outcomes. Although it would be preferred to measure cardiac output very accurately in absolute numbers, it might be more useful to categorize the level of cardiac output (low, normal, or high) for the purpose of understanding the underlying pathophysiology and when interpreted in conjunction with blood pressure for the classification of the stage of shock.37 The combination of low cardiac output and normal blood pressure would suggest a compensated shock, whereas low cardiac output and low blood pressure is indicative of an uncompensated shock. In a hyperdynamic shock, one would expect high cardiac output and low blood pressure. The interpretation of simultaneously assessed cardiac output and blood pressure enables an individualized, pathophysiology-based approach toward cardiocirculatory failure in critically ill newborn infants."
Low RVO if <150 mL/kg/min and Low superior vena cava (SVC) flow (≤55 ml/kg/min)
"Stroke volume was calculated as the product of the aortic flow velocity integral and aortic valve area. There was a twofold increase in LV output 1 hour after birth (fetal 170 +/- 46 ml/min/kg vs 1 hour 327 +/- 66 ml/min/kg; p less than 0.01) which was associated with significant increases in stroke volume, %FS, and LVEDD (stroke volume 1.21 +/- 0.33 ml/kg vs 2.25 +/- 0.37 ml/kg; %FS 34.3% +/- 5.8% vs 37.7% +/- 5.4%; LVEDD 15.4 +/- 1.1 mm vs 17.7 +/- 1.4 mm). Heart rate did not change 1 hour after birth. During the subsequent hours after birth, LV output decreased significantly to a value of 245 +/- 56 ml/min/kg (p less than 0.01) at 24 hours, which did not change 96 hours after birth."
"Noninvasive Doppler-derived cardiac output was measured with the pulsed Doppler method in 22 healthy newborns during their first four days of life. Maximal blood flow velocity in the aorta was measured with the Doppler ultrasound method. The mean Doppler-derived cardiac output was 273 +/- 59 ml/min/kg. Ductal left-to-right shunting was also determined and then graded according to the flow in the main pulmonary artery. The mean Doppler-derived cardiac output was 301 +/- 61 ml/min/kg when there was a moderate ductal left-to-right shunt, 266 +/- 59 ml/min/kg when the shunting was mild, and 260 +/- 53 ml/min/kg when there was no shunting ductus."
Zoom on the aortic valve and LVOT.
Measurement of the LVOT diameter at 0.54 cm.
Here the LVOT is 0.61 cm
VTI at LVOT level (2 lines of the PW-Doppler Cursor at level just below the valve) is at 0.078 meter in a patient with decreased LV output and LV systolic function.
Ideally you would want the best and least angulation with the LVOT to obtain your PW-Doppler with here a VTI estimated at 0.150 meter.
Here, the angle is NOT optimal - we have a VTI estimated at 0.125 meter and is likely underestimated because there is a large angle between the actually LVOT and Ascending Aorta, and the line of interrogation/cursor at the LVOT level.
Very low RVO: 88 mL/kg/min. This patient had severe RV failure with a small left to right duct that was contributing to pulmonary vascular flow in the context of significantly low right ventricular output.
Extremely depressed VTI at 0.064 m, due to RV systolic dysfunction.
Heart rate for the measured cardiac cycle is 89 bpm (this cycle is 674 msec in duration, which means that in 1 minute we have 89 cardiac cycle; 60000/674=89).
0.77 cm (RVOT)
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