Fig. 1

Measurements of the tNd, aortic characteristic impedance, and reflection magnitude (RM). A The tNd, defined as the ratio of the pre-ejection periods (PEP) to the total systolic period (PEP + ejection time [ET]) during ventricular systole, was derived from the pulsed-wave Doppler tracing of left ventricular outflow tract (LVOT) flow at the apical five-chamber view. It was calculated as the ratio of the interval from the electrocardiogram (ECG) Q wave to flow onset, to the interval from the ECG Q wave to the end of flow. B Measurements of aortic characteristic impedance and RM. Digitized data from LVOT flow and aortic pressure were aligned to calculate characteristic impedance and RM