Development and characterization of canine‐specific computational models to predict pulsatile arterial hemodynamics and ventricular‐arterial coupling

Figures

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  FIGURE 1. (a) Example aortic blood pressure waveform and pulse wave analysis (PWA) indices. P1 represents the first shoulder or early systolic peak, which in this case is the inflection point of the forward and reflected pressure waves. P2 represents the late systolic peak, which is also the systolic peak of this waveform. DN, or the dicrotic notch, is the incisura that marks the end of systole. PWA pressure augmentation, time intervals, and areas under the curve can be computed from these parameters and the diastolic pressure. Augmented pressure (Ap) is the amplitude difference between the early (P1) and late (P2) systolic peaks and is a measurement of the intensity of the reflected wave (Nichols et al., 2015). Ejection duration (ED) measures the time of systole, from the upstroke of the pressure wave at the diastolic nadir to the DN, and is composed of Tr and SDR (Nichols et al., 2013). The round trip travel time (Tr) to and from the major reflection sites of the body is measured from the diastolic pressure to the early inflection point (P1), while systolic duration of the reflected wave (SDR) is the time from P1 to DN (Hashimoto et al., 2008). The area under the systolic portion of the…

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  FIGURE 2. Example simultaneous aortic pressure and flow waveforms and wave separation analysis (WSA) and wave power analysis (WPA) indices. Aortic pressure and flow waveforms are acquired, and the slope of the early systolic pressure‐flow loop is approximated to equal the aortic characteristic impedance Zc. In WSA, aortic pressure is scaled to its diastolic pressure and separated into forward (Pf) and backward (Pb) pressure (Chirinos & Segers, 2010). Flow is multiplied by aortic Zc to obtain the product QZc, and the difference between QZc and measured pressure is quantified as Wasted pressure effort (Chirinos, 2017). In WPA, changes in pressure (dP) and flow velocity (dQ) are multiplied to calculate instantaneous wave power (d∏). Waves are identified as forward (d∏+) or backward (d∏−) based on direction of power peaks. These waves are further characterized as compression or expansion wavefronts based on signs of dP and dU: Forward compression wave (FCW): +d∏, + dP, +dQ; forward expansion wave (FEW): +d∏, −dP, −dQ; backward compression wave (BCW): −d∏, +dP, −dQ (Mynard & Smolich, 2016).

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  FIGURE 3. (a) 10 s of representative data for each animal at baseline and 1 month time points. Symbol on left corresponds to animal‐identifying symbols used in panels B‐G. Y‐axis for all data segments is set at 40–140 mmHg. (b) Average stroke volume (SV) measurement taken over a 5 minute recording period for each animal at baseline, 1 week, and 1 month. Data from individual animals are indicated by symbol. Horizontal lines represent mean value at each time point. *p < 0.05. (c) Average pressure systolic area (PSA) measurement taken over a 5 min recording period for each animal. (d) SV and PSA data at 1 week and 1 month normalized to baseline data for each animal. Bars represent minimum to maximum data, with a horizontal line at the mean value. (e) Comparison between SV and PSA reported as percent of baseline measurements. The dashed line represents equality.

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  FIGURE 4. Representative aortic blood pressure, flow, and wave separation analysis (WSA) and wave power analysis (WPA) from animal #4 at baseline (top) and 1 month after onset of RVP (bottom). (a) Simultaneous pressure (solid black line) and flow (dashed gray line) waveforms were collected. (b) Aortic pressure is scaled by setting the diastolic blood pressure to zero and then separated into forward (Pf, solid black line) and backward (Pb, dashed gray line) pressure waves, where reflection magnitude (RM) is the ratio between the peaks of Pb/Pf. (c) After Zc is determined from pressure‐flow loops, the QZc product (dark gray area) is identified and wasted pressure effort (light gray area) is then calculated as the difference between QZc and measured pressure (solid black line). (d) Change in flow volume (dQ) and pressure (dP) are used to determine forward (+d∏, solid black line) and backward (−d∏, dashed black line) wave power. The signs of dQ, dP, and d∏ classify waves as forward compressive (FCW, black area), forward expansion (FCW, dark gray area), and backward compression (BCW, light gray area) waves.

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  FIGURE 5. Representative aortic blood pressure, flow, and wave separation analysis (WSA) and wave power analysis (WPA) from animal #1 at baseline. The top row uses true measured flow measured from the animal, and the bottom row uses the synthesized flow waveform for WSA and WPA calculations. (a) Simultaneous pressure (solid black line) and measured flow (top) or synthesized flow (bottom) waveforms (dashed gray line) were collected/synthesized. (b) Aortic pressure is scaled by setting the diastolic blood pressure to zero and then separated into forward (Pf, solid black line) and backward (Pb, dashed gray line) pressure waves. (c) The QZc product (dark gray area) and wasted pressure effort (light gray area) for the corresponding measured pressure (solid black line). (d) Change in flow volume (dQ) and pressure (dP) are used to determine forward (+d∏, solid black line) and backward (−d∏, dashed black line) wave power. The signs of dQ, dP, and d∏ classify waves as forward compressive (FCW, black area), forward expansion (FCW, dark gray area), and backward compression (BCW, light gray area) waves. d∏ derived from synthesized flow (bottom trace) is uncalibrated, so FCW, FEW, and BCW heights are…