Scalability and in vivo validation of a multiscale numerical model of the left coronary circulation

Abstract

Mynard JP, Penny DJ, Smolich JJ. Scalability and in vivo validation of a multiscale numerical model of the left coronary circulation. Am J Physiol Heart Circ Physiol 306: H517-H528, 2014. First published December 20, 2013 doi:10.1152/ajpheart.00603.2013.-Multiscale modeling is a promising tool for the study of coronary hemodynamics. A key strength of this approach is that it accounts for microvascular properties and extravascular forces that differ regionally and transmurally, as well as wave propagation effects in the conduit arteries. However, little validation of such models has been reported and no models of the newborn coronary circulation have been described. We therefore validated a multiscale model of the left coronary circulation using high-fidelity data from nine adult sheep and nine newborn lambs and investigated whether wave propagation effects are more prominent in adults, whose body size (and hence wave transit distance) is greater. The model consisted of a one-dimensional (1D) network of the major conduit arteries and a lumped parameter model of microvascular beds. Intramyocardial pressure was considered to arise via contraction-related myocyte thickening and transmission of ventricular cavity pressure into the heart wall. 1D network geometry from published human anatomical data was scaled using myocardial weights, while subject-specific aortic pressure/flow and ventricular pressure formed model inputs. Total vascular resistance was determined iteratively from measured mean circumflex coronary flow (CxQ), but no fitting of phasic aspects of the waveform was performed. Excellent agreement was obtained between simulated and measured CxQ waveforms in most cases. Detailed flow waveform analysis did not clearly reveal a greater prominence of wave propagation effects in adults compared with newborns. This multiscale model is likely to be useful for investigating wave phenomena and phasic aspects of coronary flow in adults and during development. coronary arteries; wave propagation; allometric scaling; computer model; hemodynamics; newborn MATHEMATICAL MODELING, in concert with experimental studies, has played an important role in building our current understanding of coronary hemodynamics, providing insights into the role of intramyocardial pressure, large microvascular compliance, and transmural differences of vascular impedance and flow patterns (4, 9 -12, 18, 64, 67, 70). Many models of the coronary circulation have been of the lumped parameter [or zero-dimensional (0D)] type, where the resistive and capacitive properties of all coronary vessels are combined into a small number of elements. For example, the main conduit coronary arteries lying on the epicardium (or traversing the ventricular septum) have generally been represented by a single compliance (10, 12, 64) or windkessel compartment (4, 9, 18).One limitation of an exclusively 0D modeling approach is that wave propagation effects are neglected. That these effects play a role in shaping the coronary arterial flow waveform was first suggested ...

In silico coronary wave intensity analysis: application of an integrated one-dimensional and poromechanical model of cardiac perfusion

“…This was replaced by a scaled LV elastance waveform in later work (Mynard et al. 2014) for a more realistic coronary flow. The two pressures were regarded to be independent and linearly summed.…”

Impact of coronary bifurcation morphology on wave propagation

“…Two simpler assumptions are to impose a constant uniform PWS (37) (which implies decreasing β* distally) or uniform material property (implying an increase in the PWS distally) (42) throughout the network. A third common approach (43, 69) relies on an empirical relationship described by Olufsen (45), based on measurements from mostly the systemic circulation: $\frac{Eh}{r_0}=k_1{e}^{k_2{r}_0}+k_3$…”

Major influence of a ‘smoke and mirrors’ effect caused by wave reflection on early diastolic coronary arterial wave intensity

“…), has been validated in sheep (Mynard et al . ) and produced wave intensity profiles that were very consistent with published in vivo waveforms (Davies et al . ).…”

“…Using a previously described multi‐scale computational model of the coronary circulation (Mynard et al . ; Mynard & Smolich, ), we show that wave reflection effects lead to concealment of the coronary FDW dia and augmentation of the BDW dia and FCW dia , which we term a ‘smoke and mirrors’ effect. We also describe methods for unravelling the contributions of active forces and wave reflection underlying measured coronary waves.…”