Abstract
Currently, in clinical practice, the diagnosis and therapy planning of stenotic cardiovascular diseases (such as heart valve stenosis, obstructive cardiomyopathy, and aortic coarctation - CoA) affecting more than 3% of the world population, are mainly based on single-line Doppler echocardiography. By applying the simplified Bernoulli equation (SB), the observation of the peak velocity at the point of maximum constriction (i.e., the effective orifice area) is used to estimate the pressure drop caused by the stenosis. This is the peak pressure drop, and it is driven by advective (i.e., spatial acceleration) effects. The alternative is the measurement of the net pressure drop, considered the ground truth, by invasive catheterization with associated risks and costs. The difference between the peak and net pressure drop is dictated by the pressure recoveryphenomena.
The overarching objective of the PhD studies was to further refine the non-invasive access to flow inefficiencies caused by stenotic conditions and to improve the guidance the stenotic diagnostic and therapy planning. The approach taken was the analysis of blood velocity data based on its fundamental physical principles, i.e., the Navier-Stokes equations. The focus was set on the investigation of the creation/recovery of blood momentum/kinetic energy. Specifically, this was assessed at each cross-section of the vascular anatomy by the SAW formulation, a generalization of SB to the full velocity profile of the blood flow through a vessel.
In this context, the specific contributions of this thesis are: (1) a method to characterise the pressure recovery phenomena by the study of the advective pressure drop and its application to report the potential inaccuracies of catheterised pressure sensors (chapter 2); (2) a method to characterise the conduit function of a vessel, by the advective pressure drop along the length of the vessel, and its application to identify the weak link in the surgical management of hypoplastic aortas (chapter 3); (3) the proposal of a new flow efficiency metric, and correction of the estimation of the advective pressure drop, by differentiating forward and backward components of flow both in-vitro and in-vivo (chapter 4); (4) Multiple phase unwrapping of 4D Flow MRI in cardiovascular valves and vessels (chapter 5).
The following data-cohorts were used: Constant flow In-vitro phantom data from Linköping (7 valves); In-vitro pulsatile CoA phantom from Santiago (via 4 ring narrowings); In-vitro pulsatile Aortic valve disease phantom developed in-house and tested in Santiago (4 compliant valves); In-vitro pulsatile compliant Valve Tube for simultaneous multi-pressure recordings developed in-house (4 compliant valves - WIP); Bicuspid Aortic Valve Cohort from Oxford (32 patients); AMICA cohort of Aortic Valve stenosis from Oxford (25 patients); Hypoplastic left heart syndrome post-surgery from London (10 patients and 6 age-matched controls).
| Date of Award | 1 Dec 2022 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Pablo Lamata de la Orden (Supervisor) |