Coronary input impedance during cardiac cycle as determined by impulse response method

Abstract

The coronary arterial system was characterized by its input impedance determined in systole and diastole from impulse response functions in five dogs. The impulse response technique was verified on a known hydraulic system. A second confirmation was obtained on the circumflex artery: reflected pulses were correlated with site of reflections generated by occlusions. The impulse response indicates discrete reflections, superimposed on the tail of the response, resulting from diffuse reflections. Input impedance was calculated from Fourier analysis of the impulse response. Characteristic impedance was 1.0 +/- 0.2 X 10(9) Pa X s X m-3 (0.13 +/- 0.02 mmHg X ml-1 X min) and impedance at 0 Hz was 2.6 +/- 0.8 X 10(9) Pa X s X m-3. No significant differences between systole and diastole were found in both characteristic impedance and impedance at 0 Hz. It is concluded that the coronary system consists of a proximal part that can be described with the three-element windkessel and a distal part not seen by oscillatory pressure or flow perturbations, which depends on the phase of cardiac contraction.

Windkesselness of coronary arteries hampers assessment of human coronary wave speed by single-point technique

“…For a wave speed of 20 m/s, this corresponds to a minimal wavelength of 40 cm (wavelength ϭ wave speed/frequency), which is substantially more than twice the typical coronary vessel length. Additional support for the above reasoning is gained from an earlier study by van Huis et al (24) who demonstrated by using impedance analysis that the coronary system consists of a proximal part that can be described by a windkessel and a distal part that is not seen by high-frequency perturbations.…”

Patient-Specific Modeling of Blood Flow and Pressure in Human Coronary Arteries

“…17 We then computed coronary arterial resistance and coronary arterial microcirculation resistance on the basis of mean flow, mean arterial pressure, and the coronary impedance spectrum using literature data. 3,26 The capacitance values were adjusted to give physiologically realistic coronary flow and pressure waveforms using literature data. 3 During simulated exercise, the mean flow to the coronary vascular bed was increased to maintain the mean flow at 4.0% of the cardiac output.…”

A Rapid and Computationally Inexpensive Method to Virtually Implant Current and Next-Generation Stents into Subject-Specific Computational Fluid Dynamics Models

“…55 Importantly, this approach can only be applied to the coronary arteries by neglecting the contribution of ventricular contraction. 54 Nonetheless, the threeelement Windkessel method provides a good estimate of the arterial tree beyond model outlets 59 and can be described by three main parameters with physiologic meaning: Rc, C, and Rd. Rc is the characteristic impedance representing the resistance, compliance, and inertance of the proximal artery of interest, C is the arterial capacitance and represents the collective compliance of all arteries beyond a model outlet, and Rd describes the total distal resistance beyond a given outlet.…”

“…An LAD blood flow waveform at rest 20 was applied at the model inlet and outlet boundary conditions that replicated flow and pressure in the absence of ventricular contraction were applied using Simvascular. 54 A stent-to-artery deployment ratio of 1:1 was assumed. The stent was modeled as rigid while the modulus of elasticity and thickness of the vessel wall were selected to match the deformation previously observed in response to the imposed resting flow conditions.…”