Introduction: Despite more than 200 years of research, no model has been able to fit all the aortic pressure waveform with physiologically interpretable parameters. We propose that the arterial waveform is composed of two components: (1) an arterial windkessel which stores ejected blood during systole and discharges it during diastole and (2) waves originating from the left ventricle and distal reflection sites.

Method: In 19 subjects (age 54±13 years) we measured simultaneous pressure and velocity in the aorta. The windkessel component of the pressure wave was calculated, and forward and backward waves were identified as previously described [1]. The peak contribution of each component was calculated after subtraction of the diastolic pressure.

Result: In the human aorta, the initial rise in pressure was due to a wave arising from the left ventricle (Figure 1). This wave was responsible for 20 mmHg (29%) of the total rise in pressure. Windkessel pressure was responsible for 40 mmHg (57%) of the total pressure rise. Reflected waves were responsible for 10 mmHg (14%) of the total rise in pressure.

Conclusions: Using this new approach we have shown that the aortic pressure wave consists of three principal components. The systolic rise in pressure in the aorta is largely determined by a windkessel and waves arising from the left ventricle. Reflected waves make only a minor contribution. Waves do not contribute to the pressure and flow in diastole. Diastolic pressure is due to capacitative discharge of pressure from the Windkessel.