Reduced Aortic Distensibility is Associated With Higher Aorto-Carotid Wave Transmission and Central Aortic Systolic Pressure in Young Adults After Coarctation Repair

Superiority of a Representative MRI Flow Waveform over Doppler Ultrasound for Aortic Wave Reflection Assessment in Children and Adolescents With/Without a History of Heart Disease

Wave separation analysis (WSA) reveals the impact of forward- and backward-running waves on the arterial pressure pulse, but the calculations require a flow waveform. This study investigated (1) the variability of the ascending aortic flow waveform in children and adolescents with/without a childhood heart disease history (CHD); (2) the accuracy of WSA obtained with a representative flow waveform (RepFlow), compared with the triangulation method and published ultrasound-derived adult representative flow; (3) the impact of limitations in Doppler ultrasound on WSA; and (4) generalizability of results to adults with a history of CHD. Phase contrast MRI was performed in youth without (n = 45, Group 1, 10-19 years) and with CHD (n = 79, Group 2, 7-18 years), and adults with CHD history (n = 29, Group 3, 19-59 years). Segmented aortic cross-sectional area was used as a surrogate for the central pressure waveform in WSA. A subject-specific virtual Doppler ultrasound was performed on MRI data by extracting velocities from a sample volume. Time/amplitude-normalized ascending aortic flow waveforms were highly consistent amongst all groups. WSA with RepFlow therefore yielded errors < 10% in all groups for reflected wave magnitude and return time. Absolute errors were typically 1.5-3 times greater with other methods, including subject-specific (best-case/virtual) Doppler ultrasound, for which velocity profile skewing introduced waveform errors. Our data suggest that RepFlow is the optimal approach for pressure-only WSA in children and adolescents with/without CHD, as well as adults with CHD history, and may even be more accurate than subject-specific Doppler ultrasound in the ascending aorta.

Comparison of aortic stiffness and hypertension in repaired coarctation patients with a bicuspid versus a tricuspid aortic valve

BACKGROUND

Coarctation of the aorta (COA) is associated with reduced aortic distensibility and systemic hypertension (HTN). 60-85% of COA patients have a bicuspid aortic valve (BAV). It is not known if the presence of a BAV accentuates the aortopathy and HTN in CoA patients. We examined whether patients with COA and a BAV had lower aortic distensibility by CMR, and a higher prevalence of systemic HTN compared with COA patients with a tricuspid aortic valve (TAV).

METHODS

In successfully repaired COA patients excluding those with residual COA, ascending aorta (AAO) and descending aorta (DAO) distensibility was calculated by CMR. HTN was assessed using standard pediatric and adult criteria.

RESULTS

Among 215 COA patients (median age 25.3 years), 67% had a BAV, and 33% had a TAV. Median AAO distensibility z-score was lower in the BAV group (- 1.2 versus - 0.7; p = 0.014) but DAO distensibility was similar in BAV and TAV patients. HTN prevalence was similar in BAV (32%) and TAV groups (36%, p = 0.56). On multivariable analysis controlling for confounders, HTN was not associated with BAV but was associated with male gender (p = 0.003) and older age at follow-up (p = 0.004).

CONCLUSIONS

In young adults with treated COA, those with a BAV had stiffer AAO compared to those with a TAV, but DAO stiffness was similar. HTN was not related to BAV. These results suggest that although the presence of a BAV in COA exacerbates the AAO aortopathy, it does not exacerbate the more generalized vascular dysfunction and associated HTN.

Impaired Elastic Properties of the Ascending Aorta in Fetuses With Coarctation of the Aorta

Background Abnormal aortic elastic properties are major notable vasculopathy involved in coarctation of the aorta (CoA). However, there are no reports on aortic wall elastic characteristics in fetuses with CoA. Methods and Results Fifty-six fetuses with CoA and 56 normal controls were included in this prospective case-control study. The dimensions of the cardiac chamber, the size of the aorta, left ventricular myocardial performance indexes, and aortic elastic properties, including the global circumferential strain, fractional area change and mean longitudinal strain, were measured serially in utero. The global circumferential strain, fractional area change, and mean longitudinal strain in fetuses with CoA were smaller than those in the normal group at both the first and last examinations (18.50% versus 37.73% for global circumferential strain, 38.90% versus 57.55% for fractional area change, 6.61% versus 11.81% for mean longitudinal strain at first scan, 16.62% versus 42.05% for global circumferential strain, 36.54% versus 59.7% for fractional area change, 6.2% versus 11.46% for mean longitudinal strain at last scan, all P<0.001). There were negative correlations between aortic elastic properties and left ventricular myocardial performance indexes in fetuses with CoA (P<0.01). Aortic elastic properties were correlated positively with aortic isthmus size in fetuses with CoA (P<0.01). Conclusions Aortic strain and the fractional area change were decreased in fetuses with CoA. Impairments of these aortic elastic properties were associated with diminished heart function and aortic isthmus size in utero. Further large-scale longitudinal studies are required to confirm the potential predictive value of cardiovascular morbidity (ie, hypertension) in fetuses with CoA.

Multi-centre cross-sectional study on vascular remodelling in children following successful coarctation correction

Coarctation of the aorta is an arteriopathy with life-long sequelae, with remarkably increased cardiovascular events in young adults even after successful repair and despite blood pressure status. There are data on arterial remodelling in adults after coarctation correction, however, these data are scarce in childhood. Thus, the aim of this cross-sectional study was to evaluate changes in arterial wall function and morphology in children following successful coarctation repair and to compare these changes among patients with different blood pressure status and coarctation correction modes. Blood pressure status, echocardiographic parameters, arterial wall structure and stiffness, endothelial function and central blood pressure measurements were evaluated in 110 children aged 6-18 years following successful coarctation repair with right arm blood pressure not exceeding leg blood pressure by ≥20 mmHg. The prevalence of arterial hypertension was 50%. The mean carotid intima-media thickness SDS was 3.1 ± 1.5 and above 1.65 SDS in 91 of 110 patients. Increased right carotid intima-media thickness was associated with left ventricular hypertrophy, office blood pressure difference between leg and right arm, recoarctation in the past and interventional coarctation correction. Increased local common carotid artery stiffness was associated with increased pulse pressure and central systolic blood pressure. Potentially decreased endothelial function was related to a slight increase of peak and mean systolic gradient in the descending aorta. After successful coarctation repair and with a low blood pressure gradient, children still have a high prevalence of arterial hypertension and significant arterial remodelling, indicating accelerated biological age and advanced arteriosclerosis.

Personalized 0D-1D multiscale hemodynamic modeling and wave dynamics analysis of cerebral circulation for an elderly patient with dementia

Senile dementia is associated with pronounced alterations in cerebral circulation. A fundamental understanding of intracranial hemodynamics and wave dynamics is essential for assessing dementia risk. Recent findings suggest that higher carotid artery wave intensity (WI) can predict future cognitive impairments in the elderly. However, wave power (WP) is more advantageous for assessing the risk of cognitive impairment and dementia because of its conservative form, which allows quantification of detailed WP distribution among the entire cerebrovascular network. Unfortunately, intracranial hemodynamics and wave dynamics in elderly patients with dementia remain poorly understood due to ethical issues and technical challenges. In this paper, we proposed a novel and easily achievable personalized methodology for the 0D-1D model of cerebral circulation using widely available clinical data on transcranial Doppler ultrasonography velocity, cerebral artery anatomy from magnetic resonance imaging, and brachial artery pressure. Using the proposed model, we simulated the cerebral blood flows and compared the wave dynamics between a healthy elderly subject and one living with dementia. Moreover, we performed a variance-based global sensitivity analysis to quantify the model-predicted WI and WP sensitivity to the uncertainties of model inputs. This provided more precise information for model personalization and further insights into the wave dynamics of cerebral circulation. In conclusion, the proposed personalized model framework provides a practical approach for patient-specific modeling and WI/WP analysis of cerebral circulation through noninvasive clinical data. The wave dynamics features of higher WI and lower WP in cerebral arteries may be an invaluable biomarker for assessing dementia risk.

Measurement, Analysis and Interpretation of Pressure/Flow Waves in Blood Vessels

The optimal performance of the cardiovascular system, as well as the break-down 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.

Unveiling the Vascular Mechanisms Behind Long-Term Effects of Coarctation Treatment Using Pulse Wave Dynamics

See Article by Martins et al and Kowalski et al

Measuring the Interaction Between the Macro- and Micro-Vasculature

Structural and functional dysfunction in both the macro- and microvasculature are a feature of essential hypertension. In a healthy cardiovascular system, the elastic properties of the large arteries ensure that pulsations in pressure and flow generated by cyclic left ventricular contraction are dampened, so that less pulsatile pressure and flow are delivered at the microvascular level. However, in response to aging, hypertension, and other disease states, arterial stiffening limits the buffering capacity of the elastic arteries, thus exposing the microvasculature to increased pulsatile stress. This is thought to be particularly pertinent to high flow/low resistance organs such as the brain and kidney, which may be sensitive to excess pressure and flow pulsatility, damaging capillary networks, and resulting in target organ damage. In this review, we describe the clinical relevance of the pulsatile interaction between the macro- and microvasculature and summarize current methods for measuring the transmission of pulsatility between the two sites.

Reduced Aortic Distensibility is Associated With Higher Aorto-Carotid Wave Transmission and Central Aortic Systolic Pressure in Young Adults After Coarctation Repair

Background The long-term prognosis of patients with repaired aortic coarctation is characterized by high rates of cardiovascular and cerebrovascular disease related to hypertension, the basis of which remains unclear. To define potential underlying mechanisms, we investigated aortic and carotid arterial biomechanics and wave dynamics, and determinants of aortic systolic blood pressure, in young adults after coarctation repair. Methods and Results Aortic arch and carotid biomechanics, wave intensity and wave power, and central aortic blood pressure, were derived from echocardiography and brachial blood pressure in 43 young adults after coarctation repair and 42 controls. Coarctation subjects had higher brachial and central systolic blood pressure ( P=0.04), while aortic compliance was lower and characteristic impedance (Zc) higher. Although carotid intima-media thickness was higher ( P<0.001), carotid biomechanics were no different. Carotid forward compression wave power was higher and was negatively correlated with aortic compliance ( R2=0.42, P<0.001) and distensibility ( R2=0.37, P=0.001) in coarctation subjects. Aortic wave power and wave reflection indices were no different in control and coarctation patients, but coarctation patients with elevated aortic Zc had greater aorto-carotid transmission of forward compression wave power ( P=0.006). Aortic distensibility was the only independent predictor of central aortic systolic blood pressure on multivariable analysis. Conclusions Young adults following coarctation repair had a less compliant aorta, but no change in carotid biomechanics. Reduced aortic distensibility was related to greater transmission of aortic forward wave energy into the carotid artery and higher central aortic systolic blood pressure. These findings suggest that reduced aortic distensibility may contribute to later cardiovascular and cerebrovascular disease after coarctation repair.