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

KEY POINTS: Coronary wave intensity analysis (WIA) is an emerging technique for assessing upstream and downstream influences on myocardial perfusion. It is thought that a dominant backward decompression wave (BDWdia ) is generated by a distal suction effect, while early-diastolic forward decompression (FDWdia ) and compression (FCWdia ) waves originate in the aorta. We show that wave reflection also makes a substantial contribution to FDWdia , FCWdia and BDWdia , as quantified by a novel method. In 18 sheep, wave reflection accounted for ∼70% of BDWdia , whereas distal suction dominated in a computer model representing a hypertensive human. Non-linear addition/subtraction of mechanistically distinct waves (e.g. wave reflection and distal suction) obfuscates the true contribution of upstream and downstream forces on measured waves (the 'smoke and mirrors' effect). The mechanisms underlying coronary WIA are more complex than previously thought and the impact of wave reflection should be considered when interpreting clinical and experimental data. ABSTRACT: Coronary arterial wave intensity analysis (WIA) is thought to provide clear insight into upstream and downstream forces on coronary flow, with a large early-diastolic surge in coronary flow accompanied by a prominent backward decompression wave (BDWdia ), as well as a forward decompression wave (FDWdia ) and forward compression wave (FCWdia ). The BDWdia is believed to arise from distal suction due to release of extravascular compression by relaxing myocardium, while FDWdia and FCWdia are thought to be transmitted from the aorta into the coronary arteries. Based on an established multi-scale computational model and high-fidelity measurements from the proximal circumflex artery (Cx) of 18 anaesthetized sheep, we present evidence that wave reflection has a major impact on each of these three waves, with a non-linear addition/subtraction of reflected waves obscuring the true influence of upstream and downstream forces through concealment and exaggeration, i.e. a 'smoke and mirrors' effect. We also describe methods, requiring additional measurement of aortic WIA, for unravelling the separate influences of wave reflection versus active upstream/downstream forces on coronary waves. Distal wave reflection accounted for ∼70% of the BDWdia in sheep, but had a lesser influence (∼25%) in the computer model representing a hypertensive human. Negative reflection of the BDWdia at the coronary-aortic junction attenuated the Cx FDWdia (by ∼40% in sheep) and augmented Cx FCWdia (∼5-fold), relative to the corresponding aortic waves. We conclude that wave reflection has a major influence on early-diastolic WIA, and thus needs to be considered when interpreting coronary WIA profiles.

On the origin of mongrels: evolutionary history of free-breeding dogs in Eurasia.

Although a large part of the global domestic dog population is free-ranging and free-breeding, knowledge of genetic diversity in these free-breeding dogs (FBDs) and their ancestry relations to pure-breed dogs is limited, and the indigenous status of FBDs in Asia is still uncertain. We analyse genome-wide SNP variability of FBDs across Eurasia, and show that they display weak genetic structure and are genetically distinct from pure-breed dogs rather than constituting an admixture of breeds. Our results suggest that modern European breeds originated locally from European FBDs. East Asian and Arctic breeds show closest affinity to East Asian FBDs, and they both represent the earliest branching lineages in the phylogeny of extant Eurasian dogs. Our biogeographic reconstruction of ancestral distributions indicates a gradual westward expansion of East Asian indigenous dogs to the Middle East and Europe through Central and West Asia, providing evidence for a major expansion that shaped the patterns of genetic differentiation in modern dogs. This expansion was probably secondary and could have led to the replacement of earlier resident populations in Western Eurasia. This could explain why earlier studies based on modern DNA suggest East Asia as the region of dog origin, while ancient DNA and archaeological data point to Western Eurasia.

Effects of sublingual nitroglycerin on working conditions of the heart and arterial system: analysis using wave intensity.

PURPOSE: The effects of nitroglycerin (NTG) on the vascular system are well known. However, the effects of NTG on the heart are still obscure, because these effects are modified by those on the vascular system, and vice versa. Therefore, to evaluate the hemodynamic effects of NTG, it is important to understand the interaction between the heart and the vascular system. Wave intensity (WI) is a new hemodynamic index that provides information about working conditions of the heart interacting with the arterial system. The purpose of this study was to evaluate the interactive effects of NTG on the cardiovascular system in normal subjects using wave intensity. METHODS: We simultaneously measured carotid arterial blood flow velocity and diameter change using a specially designed ultrasonic system, and calculated the WI and the stiffness parameter ß. Measurements were made in 13 normal subjects (9 men and 4 women, aged 47 ± 10 years) in the supine position before and after sublingual NTG. RESULTS: The maximum value of WI (W 1) and the mid-systolic expansion wave (X) increased (W 1 from 9.1 ± 4.3 to 12.3 ± 5.5 × 10(3) mmHg m/s(3), P < 0.001; X from 105 ± 185 to 345 ± 370 mmHg m/s(3), P < 0.05). ß increased (from 10.5 ± 3.8 to 14.1 ± 3.8, P < 0.001). The pressure contours changed considerably. CONCLUSIONS: NTG increased W 1 and the mid-systolic expansion wave, which suggests enhanced cardiac power during the initial ejection and mid-systolic unloading. These results are new findings about the effects of NTG that can be added to the widely known late systolic unloading and preload reduction. NTG also increased arterial stiffness, which reduces the Windkessel function. By using an echo-Doppler system, WI can be obtained noninvasively. WI has the clinical potential to provide quantitative and detailed information about working conditions of the heart interacting with the arterial system.

Effect of viscosity on the wave propagation: Experimental determination of compression and expansion pulse wave velocity in fluid-fill elastic tube.

The velocity by which the disturbance travels through the medium is the wave velocity. Pulse wave velocity is one of the main parameters in hemodynamics. The study of wave propagation through the fluid-fill elastic tube is of great importance for the proper biophysical understanding of the nature of blood flow through of cardiovascular system. The effect of viscosity on the pulse wave velocity is generally ignored. In this paper we present the results of experimental measurements of pulse wave velocity (PWV) of compression and expansion waves in elastic tube. The solutions with different density and viscosity were used in the experiment. Biophysical model of the circulatory flow is designed to perform measurements. Experimental results show that the PWV of the expansion waves is higher than the compression waves during the same experimental conditions. It was found that the change in viscosity causes a change of PWV for both waves. We found a relationship between PWV, fluid density and viscosity.