Evaluation of contemporary methods to determine vascular impedance

The past decade has seen considerable growth in therapeutics and device technologies to treat patients with hypertension and other cardiovascular disease states. Uncoupling ventriculo-arterial interactions in these patients, however, is often complex and not adequately accounted for by arterial pressure or vascular resistance measurement alone. In reality, the global vascular load presented to the left ventricle (LV) includes both steady-state and pulsatile components. Whereas steady-state load is best represented by the vascular resistance, pulsatile load, which incorporates wave reflections and arterial stiffness, may oscillate during various phases of the cardiac cycle and is best determined by the vascular impedance (Z). In recent years, measurement of Z has become more readily accessible through an array of simultaneous applanation tonometry, echocardiography and cardiac magnetic resonance (CMR) techniques. In the following review, we evaluate existing and newer methods to assess Z so as to better understand the pulsatile characteristics of the human circulation in hypertension and other cardiovascular disease states.