Coronary arterial stiffness is related with a loss of fractal complexity in the aortic pressure

Arterial stiffening is a common but highly variable disorder. Additionally, excessive arterial pulsatility is associated with various common diseases of aging and hypertension. Fractal dimension (FD) quantifies the time series complexity defined by its geometrical representation. Objective: Arterial pressure and diameter time series were evaluated in order to assess the relationship between arterial stiffness and FD. Methods: Three Corriedale male sheep were operated. Left anterior descending artery (LAD) was dissected and the external arterial diameter was measured trough sonomicrometry. Similarly, a pressure microtransducer was positioned in the upper third of the ascending aorta. Simultaneous pressure and diameter were measured in normal state and under smooth muscle activation. Each time series FD were assessed by the application of Higuchi´s method while arterial wall elastic modulus was evaluated by means of the pressure-strain relationship. Results: Coronary stiffness was increased from normal state to phenylephrine state (47.32%, 21.12%, 10.87%) while aortic pressure FD was decreased (2.11%, 2.57%, 6.85%), respectively. Conclusion: Acute hypertension induced by phenylephrine produces an increase in the coronary wall elastic modulus with a concomitant decrease in the fractal nature of the aortic pressure, suggesting that coronary stiffening is associated with an unwrinkled aortic pressure.