Publications
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Aizawa K, Hughes AD, Casanova F, et al., 2022, Reservoir Pressure Integral Is Independently Associated With the Reduction in Renal Function in Older Adults, HYPERTENSION, Vol: 79, Pages: 2364-2372, ISSN: 0194-911X
Weinberg PDD, Schroter RCC, Parker KHH, et al., 2022, In Memoriam: Colin Caro 1925-2022, JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME, Vol: 144, ISSN: 0148-0731
Parker KH, de Tombe P, van der Velden J, et al., 2022, The nature of waves in the arteries in memoriam: Nico Westerhof and John Tyberg, JOURNAL OF PHYSIOLOGY-LONDON, Vol: 600, Pages: 4045-4050, ISSN: 0022-3751
Palombo C, Kozakova M, Morizzo C, et al., 2022, Carotid reservoir pressure decrease after prolonged head down tilt bed rest in young healthy subjects is associated with reduction in left ventricular ejection time and diastolic length (vol 13, 866045, 2022), FRONTIERS IN PHYSIOLOGY, Vol: 13
Jordan AN, Aizawa K, Gooding KM, et al., 2022, ARTERIAL HAEMODYNAMIC PARAMETERS LINKED TO ARTERIAL PULSATILITY, EXCESS WAVE PROPAGATION AND COGNITIVE FUNCTION, Journal of hypertension, Vol: 40
OBJECTIVE: Hypertension is associated with the development of cognitive impairment and dementia in an ageing population. Aortic stiffness and alterations in central artery haemodynamics could intensify the penetration of excess wave energy into the cerebral circulation, damaging the microvasculature in addition to age-associated vascular changes. We aimed to determine whether haemodynamic parameters linked to arterial pulsatility and excess wave propagation was associated with cognitive function in a sample of normotensive and hypertensive individuals. DESIGN AND METHOD: We studied 35 treatment-naïve patients with stage II/III hypertension (HT: 63.8 ± 7.4yrs, 19F, SBP 175.6 ± 16.8 mmHg) and 35 age-, sex- and body mass index-matched normotensive individuals (NT: SBP 127.2 ± 8.2 mmHg). Indices of excess pressure including excess pressure integral (INTXSP) and peak excess pressure (MAXXSP) were obtained by radial artery tonometry. Aortic forward compression wave intensity (FCWI) and aortic pulse wave velocity (aPWV) were estimated as proposed by Hughes et al (Front Physiol. 2020). A battery of cognitive examination tests was administered including Addenbrooke's Cognitive Examination-III (ACE), Mini-Mental State Examination (MMSE), Trail making test part A (TMT-A) and B (TMT-B). RESULTS: Both INTXSP (9.2 ± 2.7 vs 5.4 ± 1.2 mmHg s) and MAXXSP (54.1 ± 12.8 vs 33.4 ± 5.9 mmHg) were significantly higher in HT compared to NT (p < 0.001). Additionally, FCWI [14.9 (12.0-20.0) vs 8.0 (6.8-9.3) x105 W/m2] and aPWV (7.2 ± 1.7 vs 4.5 ± 0.8 m/s) were significantly greater in HT compared with NT (p < 0.001). Higher INTXSP was associated with poorer ACE (rs = -0.310, p = 0.009), longer TMT-A (r = 0.409, p < 0.001) and TMT-B (r = 0.380, p = 0.001). Similarly, higher MAXXSP was associated with poorer ACE (rs = -0.343, p = 0.004), longer TMT-A (r = 0.397, p = 0.001) and TMT-B (r = 0.330, p = 0.006), and greater
Jordan AN, Aizawa K, Gooding KM, et al., 2022, ARTERIAL HAEMODYNAMIC PARAMETERS LINKED TO ARTERIAL PULSATILITY, EXCESS WAVE PROPAGATION AND COGNITIVE FUNCTION, 31st Annual Scientific Meeting of the European-Society-of-Hypertension (ESH) on Hypertension and Cardiovascular Protection, Publisher: LIPPINCOTT WILLIAMS & WILKINS, Pages: E259-E259, ISSN: 0263-6352
To C, Aizawa K, Gates PE, et al., 2022, SHORT-TERM HIGH SALT INTAKE ADVERSELY AFFECTS PARAMETERS DERIVED FROM RESERVOIR-EXCESS PRESSURE ANALYSIS AND CENTRAL ARTERY HAEMODYNAMICS IN OVERWEIGHT/OBESE ADULTS, Journal of hypertension, Vol: 40
OBJECTIVE: The association between high salt intake and blood pressure is well-recognised. In overweight/obese individuals, obesity-associated hyperinsulinaemia augments renal sodium reabsorption and in combination with high salt intake this may alter blood pressure and arterial haemodynamics. We determined whether short-term high salt intake altered reservoir-excess pressure and central artery haemodynamic parameters in overweight/obese individuals. DESIGN AND METHOD: We studied 15 middle-aged and older adults (59.3 ± 6.4 yrs, 5F) who were overweight/obese with elevated systolic blood pressure (130 < SBP < 159 mmHg). In a double-blind cross-over design, they were randomly assigned to seven days of low salt diet (LSD: 50 mmol/day) or high salt intake (HIS: LSD with 200 mmol/day of sodium tablets) separated by a two-week washout period. The parameters derived from reservoir-excess pressure analysis including reservoir pressure integral, peak reservoir pressure (MAXPR), excess pressure integral (INTXSP), peak excess pressure (MAXXSP), systolic rate constant and diastolic rate constant (DRC) were obtained by radial artery tonometry. Additionally central artery haemodynamic parameters including aortic systolic pressure (aSBP), diastolic pressure (aDBP), pulse pressure (aPP) and subendocardial viability index (SVI) were derived from ensemble-averaged radial pulse waveform using generalised transfer function. Aortic pulse wave velocity (aPWV) was estimated as proposed by Hughes et al (Front Physiol. 2020). RESULTS: MAXPR (111.0 ± 10.9 vs 105.4 ± 10.4 mmHg), MAXXSP (41.7 ± 12.0 vs 36.6 ± 5.7 mmHg) and DRC (2.0 ± 0.4 vs 1.8 ± 0.3 s-1) were higher following HIS compared to LSD (p < 0.05). There was no convincing evidence that INTXSP was greater following HIS than LSD (6.9 ± 3.2 vs 5.8 ± 1.6 mmHg s, p = 0.055). aSBP (126.3 ± 15.4 vs 117.6 ± 10.1 mmHg), aDBP (76.3 ± 6.2 vs 73.1 ±
To C, Aizawa K, Gates PE, et al., 2022, SHORT-TERM HIGH SALT INTAKE ADVERSELY AFFECTS PARAMETERS DERIVED FROM RESERVOIR-EXCESS PRESSURE ANALYSIS AND CENTRAL ARTERY HAEMODYNAMICS IN OVERWEIGHT/OBESE ADULTS, 31st Annual Scientific Meeting of the European-Society-of-Hypertension (ESH) on Hypertension and Cardiovascular Protection, Publisher: LIPPINCOTT WILLIAMS & WILKINS, Pages: E259-E259, ISSN: 0263-6352
Jordan AN, Aizawa K, Gooding KM, et al., 2022, ARTERIAL HAEMODYNAMIC PARAMETERS LINKED TO ARTERIAL PULSATILITY, EXCESS WAVE PROPAGATION AND COGNITIVE FUNCTION, 31st Annual Scientific Meeting of the European-Society-of-Hypertension (ESH) on Hypertension and Cardiovascular Protection, Publisher: LIPPINCOTT WILLIAMS & WILKINS, Pages: E259-E259, ISSN: 0263-6352
To C, Aizawa K, Gates PE, et al., 2022, SHORT-TERM HIGH SALT INTAKE ADVERSELY AFFECTS PARAMETERS DERIVED FROM RESERVOIR-EXCESS PRESSURE ANALYSIS AND CENTRAL ARTERY HAEMODYNAMICS IN OVERWEIGHT/OBESE ADULTS, 31st Annual Scientific Meeting of the European-Society-of-Hypertension (ESH) on Hypertension and Cardiovascular Protection, Publisher: LIPPINCOTT WILLIAMS & WILKINS, Pages: E259-E259, ISSN: 0263-6352
Palombo C, Kozakova M, Morizzo C, et al., 2022, Carotid Reservoir Pressure Decrease After Prolonged Head Down Tilt Bed Rest in Young Healthy Subjects Is Associated With Reduction in Left Ventricular Ejection Time and Diastolic Length, FRONTIERS IN PHYSIOLOGY, Vol: 13
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- Citations: 1
Francis N, Selwanos PP, Yacoub MH, et al., 2021, The Use of Maximum Entropy to Enhance Wave Intensity Analysis: An Application to Coronary Arteries in Hypertrophic Obstructive Cardiomyopathy, FRONTIERS IN CARDIOVASCULAR MEDICINE, Vol: 8, ISSN: 2297-055X
Aizawa K, Casanova F, Gates PE, et al., 2021, Reservoir-Excess Pressure Parameters Independently Predict Cardiovascular Events in Individuals With Type 2 Diabetes, HYPERTENSION, Vol: 78, Pages: 40-50, ISSN: 0194-911X
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- Citations: 2
Aizawa K, Casanova F, Mawson DM, et al., 2021, ELEVATED EXCESS PRESSURE INTEGRAL IS ASSOCIATED WITH VASCULAR BIOMARKERS OF SUBCLINICAL ATHEROSCLEROSIS IN OLDER ADULTS, Publisher: LIPPINCOTT WILLIAMS & WILKINS, Pages: E314-E314, ISSN: 0263-6352
Morad S, Ulbricht C, Harkin P, et al., 2020, Surgical Robot Platform with a Novel Concentric Joint for Minimally Invasive Procedures, Journal of Medical Robotics Research, Vol: 5, ISSN: 2424-9068
In this paper, a surgical robot platform with a novel concentric connector joint (CCJ) is presented. The surgical robot is a parallel robot platform comprised of multiple struts, arranged in a geometrically stable array, connected at their end points via the CCJ. The CCJ joints have near-perfect concentricity of rotation around the node point, which enables the tension and compression forces of the struts to be resolved in a structurally-efficient manner. The preliminary feasibility tests, modeling and simulations were introduced.
Bhuva AN, D'Silva A, Torlasco C, et al., 2020, Non-invasive assessment of ventriculo-arterial coupling using aortic wave intensity analysis combining central blood pressure and phase-contrast cardiovascular magnetic resonance, EUROPEAN HEART JOURNAL-CARDIOVASCULAR IMAGING, Vol: 21, Pages: 805-813, ISSN: 2047-2404
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- Citations: 10
Michail M, Hughes AD, Comella A, et al., 2020, Acute Effects of Transcatheter Aortic Valve Replacement on Central Aortic Hemodynamics in Patients With Severe Aortic Stenosis, HYPERTENSION, Vol: 75, Pages: 1557-1564, ISSN: 0194-911X
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- Citations: 8
Hughes AD, Park C, Ramakrishnan A, et al., 2020, Feasibility of estimation of aortic wave intensity using non-invasive pressure recordings in the absence of flow velocity in man, Frontiers in Physiology, Vol: 11, Pages: 1-9, ISSN: 1664-042X
Background: Wave intensity analysis provides valuable information on ventriculo-arterial function, hemodynamics, and energy transfer in the arterial circulation. Widespread use of wave intensity analysis is limited by the need for concurrent measurement of pressure and flow waveforms. We describe a method that can estimate wave intensity patterns using only non-invasive pressure waveforms (pWIA).Methods: Radial artery pressure and left ventricular outflow tract (LVOT) flow velocity waveforms were recorded in 12 participants in the Southall and Brent Revisited (SABRE) study. Pressure waveforms were analyzed using custom-written software to derive the excess pressure (Pxs) which was scaled to peak LVOT velocity and used to calculate wave intensity. These data were compared with wave intensity calculated using the measured LVOT flow velocity waveform. In a separate study, repeat measures of pWIA were performed on 34 individuals who attended two clinic visits at an interval of ≈1 month to assess reproducibility and reliability of the method.Results: Pxs waveforms were similar in shape to aortic flow velocity waveforms and the time of peak Pxs and peak aortic velocity agreed closely. Wave intensity estimated using pWIA showed acceptable agreement with estimates using LVOT velocity tracings and estimates of wave intensity were similar to values reported previously in the literature. The method showed fair to good reproducibility for most parameters.Conclusion: The Pxs is a surrogate of LVOT flow velocity which, when appropriately scaled, allows estimation of aortic wave intensity with acceptable reproducibility. This may enable wider application of wave intensity analysis to large studies.
Abou Gamrah M, Xu J, El Sawy A, et al., 2020, Mechanics of the dicrotic notch: An acceleration hypothesis, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART H-JOURNAL OF ENGINEERING IN MEDICINE, Vol: 234, Pages: 1253-1259, ISSN: 0954-4119
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- Citations: 3
Hughes AD, Parker KH, 2020, The modified arterial reservoir: An update with consideration of asymptotic pressure (P-infinity) and zero-flow pressure (P-zf), PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART H-JOURNAL OF ENGINEERING IN MEDICINE, Vol: 234, Pages: 1288-1299, ISSN: 0954-4119
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- Citations: 10
Martinez-Perez ME, Parker KH, Witt N, et al., 2020, Automatic artery/vein classification in colour retinal images, 12th International Conference on Machine Vision (ICMV), Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
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- Citations: 2
Sherwood JM, Boazak EM, Feola AJ, et al., 2019, Measurement of ocular compliance using iPerfusion, Frontiers in Bioengineering and Biotechnology, Vol: 7, Pages: 1-15, ISSN: 2296-4185
The pressure-volume relationship of the eye is determined by the biomechanical properties of the corneoscleral shell and is classically characterised by Friedenwald's coefficient of ocular rigidity or, alternatively, by the ocular compliance (OC), defined as dV/dP. OC is important in any situation where the volume (V) or pressure (P) of the eye is perturbed, as occurs during several physiological and pathological processes. However, accurately measuring OC is challenging, particularly in rodents. We measured OC in 24 untreated enucleated eyes from 12 C57BL/6 mice using the iPerfusion system to apply controlled pressure steps, whilst measuring the time-varying flow rate into the eye. Pressure and flow data were analysed by a “Discrete Volume” (integrating the flow trace) and “Step Response” method (fitting an analytical solution to the pressure trace). OC evaluated at 13 mmHg was similar between the two methods (Step Response, 41 [37, 46] vs. Discrete Volume, 42 [37, 48] nl/mmHg; mean [95% CI]), although the Step Response Method yielded tighter confidence bounds on individual eyes. OC was tightly correlated between contralateral eyes (R2 = 0.75, p = 0.0003). Following treatment with the cross-linking agent genipin, OC decreased by 40 [33, 47]% (p = 0.0001; N = 6, Step Response Method). Measuring OC provides a powerful tool to assess corneoscleral biomechanics in mice and other species.
Sluyter JD, Hughes AD, Camargo CA, et al., 2019, Identification of Distinct Arterial Waveform Clusters and a Longitudinal Evaluation of Their Clinical Usefulness, HYPERTENSION, Vol: 74, Pages: 921-928, ISSN: 0194-911X
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- Citations: 6
Su J, Hughes AD, Simonsen U, et al., 2019, Impact of pulmonary endarterectomy on pulmonary arterial wave propagation and reservoir function., Am J Physiol Heart Circ Physiol, Vol: 317, Pages: H505-H516
High wave speed and large wave reflection in the pulmonary artery have previously been reported in patients with chronic thromboembolic pulmonary hypertension (CTEPH). We assessed the impact of pulmonary endarterectomy (PEA) on pulmonary arterial wave propagation and reservoir function in patients with CTEPH. Right heart catheterization was performed using a combined pressure and Doppler flow sensor-tipped guidewire to obtain simultaneous pressure and flow velocity measurements in the pulmonary artery in eight patients with CTEPH before and 3 mo after PEA. Wave intensity and reservoir-excess pressure analyses were then performed. Following PEA, mean pulmonary arterial pressure (PAPm; ∼49 vs. ∼32 mmHg), pulmonary vascular resistance (PVR; ∼11.1 vs. ∼5.1 Wood units), and wave speed (∼16.5 vs. ∼8.1 m/s), i.e., local arterial stiffness, markedly decreased. The changes in the intensity of the reflected arterial wave and wave reflection index (pre: ∼28%; post: ∼22%) were small, and patients post-PEA with and without residual pulmonary hypertension (i.e., PAPm ≥ 25 mmHg) had similar wave reflection index (∼20 vs. ∼23%). The reservoir and excess pressure decreased post-PEA, and the changes were associated with improved right ventricular afterload, function, and size. In conclusion, although PVR and arterial stiffness decreased substantially following PEA, large wave reflection persisted, even in patients without residual pulmonary hypertension, indicating lack of improvement in vascular impedance mismatch. This may continue to affect the optimal ventriculoarterial interaction, and further studies are warranted to determine whether this contributes to persistent symptoms in some patients.NEW & NOTEWORTHY We performed wave intensity analysis in the pulmonary artery in patients with chronic thromboembolic pulmonary hypertension before and 3 mo after pulmonary endarterectomy. Despite substantial reduction in pulmonary arterial pres
Aizawa K, Casanova F, Mawson DM, et al., 2019, ALTERED CENTRAL HAEMODYNAMIC PARAMETERS DERIVED FROM RESERVOIR PRESSURE ANALYSIS: ASSOCIATION WITH BIOMARKERS OF TARGET ORGAN DAMAGE IN OLDER ADULTS, 29th European Meeting of Hypertension and Cardiovascular Protection of the European-Society-of-Hypertension (ESH), Publisher: LIPPINCOTT WILLIAMS & WILKINS, Pages: E307-E307, ISSN: 0263-6352
Elena Martinez-Perez M, Witt N, Parker KH, et al., 2019, Automatic optic disc detection in colour fundus images by means of multispectral analysis and information content, PEERJ, Vol: 7, ISSN: 2167-8359
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- Citations: 7
Negoita M, Hughes AD, Parker KH, et al., 2018, A method for determining local pulse wave velocity in human ascending aorta from sequential ultrasound measurements of diameter and velocity, PHYSIOLOGICAL MEASUREMENT, Vol: 39, ISSN: 0967-3334
Neumann S, Sophocleous F, Kobetic MD, et al., 2018, Wave intensity analysis in the internal carotid artery of hypertensive subjects using phase-contrast MR angiography and preliminary assessment of the effect of vessel morphology on wave dynamics, PHYSIOLOGICAL MEASUREMENT, Vol: 39, ISSN: 0967-3334
Michail M, Davies JE, Cameron JD, et al., 2018, Pathophysiological coronary and microcirculatory flow alterations in aortic stenosis, NATURE REVIEWS CARDIOLOGY, Vol: 15, Pages: 420-431, ISSN: 1759-5002
Broyd CJ, Rigo F, Nijjer S, et al., 2018, Regression of left ventricular hypertrophy provides an additive physiological benefit following treatment of aortic stenosis: Insights from serial coronary wave intensity analysis., Acta Physiologica, Vol: 2018, Pages: e13109-e13109, ISSN: 1748-1708
AIM: Severe aortic stenosis frequently involves the development of left ventricular hypertrophy (LVH) creating a dichotomous haemodynamic state within the coronary circulation. Whilst the increased force of ventricular contraction enhances its resultant relaxation and thus increases the distal diastolic coronary "suction" force, the presence of LVH has a potentially opposing effect on ventricular-coronary interplay. The aim of this study was to use non-invasive coronary wave intensity analysis (WIA) to separate and measure the sequential effects of outflow tract obstruction relief and then LVH regression following intervention for aortic stenosis. METHODS: Fifteen patients with unobstructed coronary arteries undergoing aortic valve intervention (11 surgical aortic valve replacement [SAVR], 4 TAVI) were successfully assessed before and after intervention, and at 6 and 12 months post-procedure. Coronary WIA was constructed from simultaneously acquired coronary flow from transthoracic echo and pressure from an oscillometric brachial cuff system. RESULTS: Immediately following intervention, a decline in the backward decompression wave (BDW) was noted (9.7 ± 5.7 vs 5.1 ± 3.6 × 103 W/m2 /s, P < 0.01). Over 12 months, LV mass index fell from 114 ± 19 to 82 ± 17 kg/m2 . Accompanying this, the BDW fraction increased to 32.8 ± 7.2% at 6 months (P = 0.01 vs post-procedure) and 34.7 ± 6.7% at 12 months (P < 0.001 vs post-procedure). CONCLUSION: In aortic stenosis, both the outflow tract gradient and the presence of LVH impact significantly on coronary haemodynamics that cannot be appreciated by examining resting coronary flow rates alone. An immediate change in coronary wave intensity occurs following intervention with further effects appreciable with hypertrophy regression. The improvement
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