Ross-Konno and Endocardial Fibroelastosis Resection After Hybrid Stage I Palliation in Infancy: Successful Staged Left-Ventricular Rehabilitation and Conversion to Biventricular Circulation After Fetal Diagnosis of Aortic Stenosis

We report a patient who presented during fetal life with severe aortic stenosis, left-ventricular dysfunction, and endocardial fibroelastosis (evolving hypoplastic left heart syndrome). Management involved in utero and postnatal balloon aortic valvuloplasty for partial relief of obstruction and early postnatal hybrid stage I palliation until recovery of left-ventricular systolic function had occurred. The infant subsequently had successful conversion to a biventricular circulation by combining resection of endocardial fibroelastosis with single-stage Ross-Konno, aortic arch reconstruction, hybrid takedown, and pulmonary artery reconstruction

One-Dimensional Haemodynamic Modeling and Wave Dynamics in the Entire Adult Circulation

One-dimensional (1D) modeling is a powerful tool for studying haemodynamics; however, a comprehensive 1D model representing the entire cardiovascular system is lacking. We present a model that accounts for wave propagation in anatomically realistic systemic (including coronary and cerebral) arterial/venous networks, pulmonary arterial/venous networks and portal veins. A lumped parameter (0D) heart model represents cardiac function via a time-varying elastance and source resistance, and accounts for mechanical interactions between heart chambers mediated via pericardial constraint, the atrioventricular septum and atrioventricular plane motion. A non-linear windkessel-like 0D model represents microvascular beds, while specialized 0D models are employed for the hepatic and coronary beds. Model-derived pressure and flow waveforms throughout the circulation are shown to reproduce the characteristic features of published human waveforms. Moreover, wave intensity profiles closely resemble available in vivo profiles. Forward and backward wave intensity is quantified and compared along major arteriovenous paths, providing insights into wave dynamics in all of the major physiological networks. Interactions between cardiac function/mechanics and vascular waves are investigated. The model will be an important resource for studying the mechanics underlying pressure/flow waveforms throughout the circulation, along with global interactions between the heart and vessels under normal and pathological conditions

Wave potential and the one-dimensional windkessel as a wave-based paradigm of diastolic arterial hemodynamics

Controversy exists about whether one-dimensional wave theory can explain the "self-canceling" waves that accompany the diastolic pressure decay and discharge of the arterial reservoir. Although it has been proposed that reservoir and wave effects be treated as separate phenomena, thus avoiding the issue of self-canceling waves, we have argued that reservoir effects are a phenomenological and mathematical subset of wave effects. However, a complete wave-based explanation of self-canceling diastolic expansion (pressure-decreasing) waves has not yet been advanced. These waves are present in the forward and backward components of arterial pressure and flow (P ± and Q ±, respectively), which are calculated by integrating incremental pressure and flow changes (dP ± and dQ ±, respectively). While the integration constants for this calculation have previously been considered arbitrary, we showed that physiologically meaningful constants can be obtained by identifying "undisturbed pressure" as mean circulatory pressure. Using a series of numeric experiments, absolute P ± and Q ± values were shown to represent "wave potential," gradients of which produce propagating wavefronts. With the aid of a "one-dimensional windkessel," we showed how wave theory predicts discharge of the arterial reservoir. Simulated data, along with hemodynamic recordings in seven sheep, suggested that self-canceling diastolic waves arise from repeated and diffuse reflection of the late systolic forward expansion wave throughout the arterial system and at the closed aortic valve, along with progressive leakage of wave potential from the conduit arteries. The combination of wave and wave potential concepts leads to a comprehensive one-dimensional (i.e., wave-based) explanation of arterial hemodynamics, including the diastolic pressure decay

Novel wave power analysis linking pressure-flow waves, wave potential, and the forward and backward components of hydraulic power

Wave intensity analysis provides detailed insights into factors influencing hemodynamics. However, wave intensity is not a conserved quantity, so it is sensitive to diameter variations and is not distributed among branches of a junction. Moreover, the fundamental relation between waves and hydraulic power is unclear. We, therefore, propose an alternative to wave intensity called "wave power," calculated via incremental changes in pressure and flow (dPdQ) and a novel time-domain separation of hydraulic pressure power and kinetic power into forward and backward wave-related components (ΠP±and ΠQ±). Wave power has several useful properties:1) it is obtained directly from flow measurements, without requiring further calculation of velocity;2) it is a quasi-conserved quantity that may be used to study the relative distribution of waves at junctions; and3) it has the units of power (Watts). We also uncover a simple relationship between wave power and changes in ΠP±and show that wave reflection reduces transmitted power. Absolute values of ΠP±represent wave potential, a recently introduced concept that unifies steady and pulsatile aspects of hemodynamics. We show that wave potential represents the hydraulic energy potential stored in a compliant pressurized vessel, with spatial gradients producing waves that transfer this energy. These techniques and principles are verified numerically and also experimentally with pressure/flow measurements in all branches of a central bifurcation in sheep, under a wide range of hemodynamic conditions. The proposed "wave power analysis," encompassing wave power, wave potential, and wave separation of hydraulic power provides a potent time-domain approach for analyzing hemodynamics

Increased right ventricular output and central pulmonary reservoir function support rise in pulmonary blood flow during adenosine infusion in the ovine fetus

Although adenosine markedly increases fetal pulmonary blood flow, the specific changes in pulmonary trunk (PT), ductus arteriosus (DA), and conduit pulmonary artery (PA) flow interactions that support this increased flow are unknown. To address this issue, seven anesthetized late-gestation fetal sheep were instrumented with PT, DA, and left PA micromanometer catheters and transit-time flow probes. Blood flow profile and wave intensity analyses were performed at baseline and after adenosine infusion to increase PA flow approximately fivefold. With adenosine infusion, DA mean and phasic flows were unchanged, but increases in mean PT (500 ± 256 ml/min, P = 0.002) and the combined left and right PA flow (479 ± 181 ml/min, P 0.7) and related to a larger flow-increasing forward-running compression wave arising from right ventricular (RV) impulsive contraction. Moreover, while the increased PT flow was confined to systole, the rise in PA flow spanned systole (316 ml/min) and diastole (163 ml/min). This elevated PA diastolic flow was accompanied by a 170% greater discharge from a PT and main PA reservoir filled in systole (P < 0.001), but loss of retrograde blood discharge from a conduit PA reservoir that was evident at baseline. These data suggest that 1) an increase in fetal pulmonary blood flow produced by adenosine infusion is primarily supported by a higher PT blood flow (i.e., RV output); 2) about two-thirds of this increased RV output passes into the pulmonary circulation during systole; and 3) the remainder is transiently stored in a central PT and main PA systolic reservoir, from where it discharges into the lungs in diastole