Background: Stiffening and dilatation of the ascending aorta (AA) with age is a major determinant of increased aortic pulse pressure (PP), leading to isolated systolic hypertension. The aortic wrap (AW) is our proposed method to restore higher distensibility in the stiffened AA. By wrapping the AA with a highly distensible synthetic material and decreasing the AA diameter it is possible to shift the pulsatile load from the AA walls to the AW, thus reducing PP and systolic pressure. Aim: To investigate the effects of the AW on input impedance (Zin) and characteristic impedance (Zc) in a bench model of the arterial circulation. Methods: A hydraulic loop model of the circulation was used. This is composed by a silicon model of the arterial tree connected to a pulsatile pump, which mimicks physiological conditions (3 heart rates (HRs) of 50, 65 and 80 bpm; and 3 stroke volumes (SVs) of 60, 70 and 80 ml/s). The AA segment of the model was wrapped with a distensible elastic band (3.5 cm long), achieving a 30% diameter reduction of the AA at 0 mmHg. Flow waves were recorded at the inlet via a transonic flowmeter, and pressure waves were recorded at 10 locations along the model with a Millar microtip pressure catheter. Zin (= P(ω)/Q(ω), where ω=frequency) and Zc (initial slope of the P-Q curve) were calculated for all the possible combinations of HR and SV. Results: After wrapping, there was a consistent reduction of Zc, with the exception of the 50 bpm HR–80 ml SV configuration. The maximum reduction (–41.9% compared with the corresponding unwrapped value) was achieved at the lowest HR (50 bpm) and lowest SV (50 ml). Zin modulus was reduced consistently by the AW, the 1st harmonic component showing a decrease (varying from –14.5% to –30.1% of the corresponding unwrapped value) for all the low (50 bpm) and medium (65 bpm) HR configurations. Conclusion: Our in vitro modelling study shows that the AW procedure consistently decreases Zin and Zc for most HR and SV configurations, resulting in a concomitant decrease of PP. This suggests a potential use of the AW as a non-pharmacological treatment of isolated systolic hypertension. The dependency of the impedance reduction on HR and SV indicates a potential patient-specific optimization approach.
|Number of pages||1|
|Publication status||Published - Jun 2014|
|Event||Annual Scientific Meeting of the High Blood Pressure Research Council of Australia (HBPRCA) (35th : 2013) / Annual Scientific Meeting of the Australian Atherosclerosis Society (AAS) (39th : 2013) - Melbourne, Australia, Australia|
Duration: 5 Dec 2013 → 7 Dec 2013