The optimal performance of the cardiovascular system, as well as the breakdown of this performance with disease, both involve complex biomechanical interactions between the heart, conduit vascular networks and microvascular beds. 'Wave analysis' refers to a group of techniques that provide valuable insight into these interactions by scrutinizing the shape of blood pressure and flow/velocity waveforms. The aim of this review paper is to provide a comprehensive introduction to wave analysis, with a focus on key concepts and practical application rather than mathematical derivations. We begin with an overview of invasive and non-invasive measurement techniques that can be used to obtain the signals required for wave analysis. We then review the most widely used wave analysis techniques-pulse wave analysis, wave separation and wave intensity analysis-and associated methods for estimating local wave speed or characteristic impedance that are required for decomposing waveforms into forward and backward wave components. This is followed by a discussion of the biomechanical phenomena that generate waves and the processes that modulate wave amplitude, both of which are critical for interpreting measured wave patterns. Finally, we provide a brief update on several emerging techniques/concepts in the wave analysis field, namely wave potential and the reservoir-excess pressure approach.
Wave reflection from the site of aortic coarctation produces a reflected backward compression wave (BCW) that raises left ventricular (LV) afterload. However, not all reflected wave power will propagate back to the LV. This study investigated the hypothesis that the BCW is partially transmitted into supra-aortic vessels as a forward wave and explored the consequences of this phenomenon for cerebral and LV haemodynamic load. In eight sheep, high fidelity pressure and flow were measured in the aortic trunk (AoT) and brachiocephalic trunk (BCT, the single supra-aortic vessel present in sheep) at baseline and during two levels of proximal descending aortic constriction. Wave power analysis showed that aortic constriction produced not only a BCW in the AoT, but also a second forward compression wave ([Formula: see text] in the BCT that augmented pressure and flow after the initial forward compression wave ([Formula: see text]. Mathematical analysis and a one-dimensional model of the human systemic arteries and aortic coarctation suggested that the relative transmission of waves into supra-aortic vessels versus the aorta was determined by the relative admittances of these vessels. Reducing supra-aortic admittance (1) increased pressure and flow pulsatility in cerebral arteries, (2) produced carotid and middle cerebral arterial flow waveforms with an older adult phenotype, (3) promoted transmission of reflected wave power towards the LV and (4) substantially increased mid- to late-systolic myocardial stress, which may promote LV hypertrophy. These findings suggest that wave transmission into supra-aortic branches has an important impact on both cerebral hemodynamics and LV load in aortic coarctation.
BackgroundThe Ross procedure in children carries substantial mortality and reoperation rate. Aortic root dilatation is of concern. To prevent dilatation of the neoaortic root, but permit normal growth, we began to apply an absorbable poly‐(p‐dioxanone)‐filaments (PDS) band at the sino‐tubular (ST)‐junction.Methods and ResultsAll children (n=100) who underwent Ross procedure during 1995–2012 were studied. Mean age at operation was 8.6±6.1 years (median 8.3 years, range 3 days to 18 years); 19 patients were younger than 1 year of age. The root replacement (n=91, Ross‐Konno procedure in 29 patients), root inclusion (n=6), and subcoronary implantation (n=3) techniques were used. Operative mortality was 6% (6/100, 4 neonates, 2 infants). Age of <1‐year at time of operation was a risk factor for early death (P<0.001). Mean follow‐up time was 7.0±4.8 years (median 7.4 years, range 5 days to 16 years). Late mortality was 4.3% (4/94). Freedom from moderate or greater neoaortic valve insufficiency (AI) at 5 and 10 years was 89% and 83%, respectively. Freedom from neoaortic valve reoperation at 5 and 10 years was 96% and 86%, respectively. Aortic dilatation to Z‐score >4 was greatest at the ST‐junction (23%, 11/48) compared to the aortic annulus (17%, 11/66) and sinuses (14%, 7/50). Since 2001, a PDS band was placed around the ST‐junction in 19 patients. Survivors with the PDS band had less AI (0 versus 20%, P=0.043) compared to survivors (n=35) without the PDS at 4.1±3 years.ConclusionsThe Ross procedure in children can be performed with acceptable results. Children younger than 1 year of age have higher mortality, but not an increased autograft reoperation rate. Stabilization of the ST‐junction may reduce AI.
Until data are available from larger prospective studies, it is prudent to advise families of individuals with a history of Kawasaki disease to minimise traditional modifiable cardiovascular risk factors.
Patients with a hypoplastic arch operated via thoracotomy have an alarming prevalence of hypertension. Regular follow-up with 24-hour ambulatory blood pressure monitoring is warranted, especially in patients who have had a smaller aortic arch at the time of the initial operation.
Patients with moderately hypoplastic arch treated by conventional coarctation repair have adequate growth of the distal arch demonstrated at long-term follow-up, but one-third of them keep a small proximal arch. This subset of patients is at risk of developing hypertension and may warrant further investigation.
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