Impedance cardiographic hemodynamic variables and hypertension in elderly Han residents

OBJECTIVE We studied the relationship between systolic blood pressure and hemodynamics using impedance cardiography in elderly Han residents in order to evaluate how different hemodynamic variables are altered with normal aging and with hypertension superimposed on aging. METHODS A total of 670 subjects, aged 60-93 years, were evaluated with impedance cardiography for non-invasive hemodynamic variables. The subjects were categorized as hypertensives or normotensives, and then they were also divided into six subgroups according to actual systolic blood pressure values. RESULTS Hypertensive patients had significantly lower values of cardiac output (4.4 ± 1.5 L/min) and cardiac index (2.6 ± 1.0 L/min/m(2)) than those in the normotensive group (4.7 ± 1.5 L/min, and 2.8 ± 0.8 L/min/m(2), respectively; P < 0.05 for both). Compared to the normotensive group, stroke volume and stroke index values were also lower and systemic vascular resistance and systemic vascular resistance index were higher in the hypertensive group. There were no significant differences in left ventricular stroke work and left ventricular stroke work index between the two groups. When all 670 subjects were stratified to actual blood pressure, cardiac output of group 6 patients (systolic blood pressure ≥180 mmHg) was 19% lower than that of group 1 subjects (SBP <140 mmHg; P < 0.05). Similarly, systemic vascular resistance of group 6 patients was 56% higher than that of group 1 subjects (P < 0.05). CONCLUSION With aging, arterial systolic blood pressure is elevated as a result of increased arterial stiffness and increased systemic vascular resistance. With hypertension, these values are further elevated. Non-invasive impedance cardiography helps to characterize the hemodynamic mechanisms, which can improve hypertension management.