Publications
477 results found
Michail M, Comella A, McCormick L, et al., 2019, The Immediate Physiological Impact of Transcatheter Aortic Valve Replacement on Central Aortic Pressure in Patients With Severe Aortic Stenosis, 31st Annual Symposium on Transcatheter Cardiovascular Therapeutics (TCT), Publisher: ELSEVIER SCIENCE INC, Pages: B137-B137, ISSN: 0735-1097
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: 7
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: 8
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
Michail M, Narayan O, Parker KH, et al., 2018, Relationship of aortic excess pressure obtained using pressure-only reservoir pressure analysis to directly measured aortic flow in humans, PHYSIOLOGICAL MEASUREMENT, Vol: 39, ISSN: 0967-3334
Su J, Logan CC, Hughes AD, et al., 2018, Impact of chronic hypoxia on proximal pulmonary artery wave propagation and mechanical properties in rats, AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, Vol: 314, Pages: H1264-H1278, ISSN: 0363-6135
Raphael CE, Cooper R, Mitchell F, et al., 2018, PERFUSION ABNORMALITIES IN HYPERTROPHIC CARDIOMYOPATHY: MECHANISMS AND PROGNOSTIC IMPORTANCE, Annual Conference of the British-Cardiovascular-Society on High Performing Teams, Publisher: BMJ PUBLISHING GROUP, Pages: A112-A113, ISSN: 1355-6037
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- Citations: 1
Aizawa K, Casanova F, Mawson DM, et al., 2018, PARAMETERS DERIVED FROM RESERVOIR PRESSURE ANALYSIS INDEPENDENTLY PREDICT CARDIOVASCULAR EVENTS IN A MULTI-CENTRE STUDY OF INDIVIDUALS WITH TYPE 2 DIABETES, 28th European Meeting of Hypertension and Cardiovascular Protection of the European-Society-of-Hypertension (ESH), Publisher: LIPPINCOTT WILLIAMS & WILKINS, Pages: E286-E287, ISSN: 0263-6352
Broyd CJ, Hernández-Pérez F, Segovia J, et al., 2018, Identification of capillary rarefaction using intracoronary wave intensity analysis with resultant prognostic implications for cardiac allograft patients, European Heart Journal, Vol: 39, Pages: 1807-1814, ISSN: 1522-9645
Aims: Techniques for identifying specific microcirculatory structural changes are desirable. As such, capillary rarefaction constitutes one of the earliest changes of cardiac allograft vasculopathy (CAV) in cardiac allograft recipients, but its identification with coronary flow reserve (CFR) or intracoronary resistance measurements is hampered because of non-selective interrogation of the capillary bed. We therefore investigated the potential of wave intensity analysis (WIA) to assess capillary rarefaction and thereby predict CAV. Methods and results: Fifty-two allograft patients with unobstructed coronary arteries and normal left ventricular (LV) function were assessed. Adequate aortic pressure and left anterior descending artery flow measurements at rest and with intracoronary adenosine were obtained in 46 of which 2 were lost to follow-up. In a subgroup of 15 patients, simultaneous RV biopsies were obtained and analysed for capillary density. Patients were followed up with 1-3 yearly screening angiography. A significant relationship with capillary density was noted with CFR (r = 0.52, P = 0.048) and the backward decompression wave (BDW) (r = -0.65, P < 0.01). Over a mean follow-up of 9.3 ± 5.2 years patients with a smaller BDW had an increased risk of developing angiographic CAV (hazard ratio 2.89, 95% CI 1.12-7.39; P = 0.03). Additionally, the index BDW was lower in those who went on to have a clinical CAV-events (P = 0.04) as well as more severe disease (P = 0.01). Conclusions: Within cardiac transplant patients, WIA is able to quantify the earliest histological changes of CAV and can predict clinical and angiographic outcomes. This proof-of-concept for WIA also lends weight to its use in the assessment of other disease processes in which capillary rarefaction is involved.
Cameron JD, Parker K, Narayan O, et al., 2018, Reply - Aortic Reservoir Pressure - not overstretching but testing, JOURNAL OF HYPERTENSION, Vol: 36, Pages: 964-965, ISSN: 0263-6352
Negoita M, Abdullateef S, Hughes AD, et al., 2018, Semi-automatic Vendor-Independent Software for Assessment of Local Arterial Stiffness, 45th Computing in Cardiology Conference (CinC), Publisher: IEEE, ISSN: 2325-8861
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- Citations: 1
Sluyter JD, Hughes AD, Thom SAMG, et al., 2017, Arterial waveform parameters in a large, population-based sample of adults: relationships with ethnicity and lifestyle factors (vol 31, pg 305, 2017), JOURNAL OF HUMAN HYPERTENSION, Vol: 31, Pages: 760-760, ISSN: 0950-9240
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Tyberg JV, Burrowes LM, Bouwmeester JC, et al., 2017, Last Word on Viewpoint: Origin of the forward-going "backward" wave, JOURNAL OF APPLIED PHYSIOLOGY, Vol: 123, Pages: 1411-1411, ISSN: 8750-7587
Su J, Manisty C, Parker KH, et al., 2017, Wave Intensity Analysis Provides Novel Insights Into Pulmonary Arterial Hypertension and Chronic Thromboembolic Pulmonary Hypertension., Journal of the American Heart Association, Vol: 6, ISSN: 2047-9980
BACKGROUND: In contrast to systemic hypertension, the significance of arterial waves in pulmonary hypertension (PH) is not well understood. We hypothesized that arterial wave energy and wave reflection are augmented in PH and that wave behavior differs between patients with pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). METHODS AND RESULTS: Right heart catheterization was performed using a pressure and Doppler flow sensor-tipped catheter to obtain simultaneous pressure and flow velocity measurements in the pulmonary artery. Wave intensity analysis was subsequently applied to the acquired data. Ten control participants, 11 patients with PAH, and 10 patients with CTEPH were studied. Wave speed and wave power were significantly greater in PH patients compared with controls, indicating increased arterial stiffness and right ventricular work, respectively. The ratio of wave power to mean right ventricular power was lower in PAH patients than CTEPH patients and controls. Wave reflection index in PH patients (PAH: ≈25%; CTEPH: ≈30%) was significantly greater compared with controls (≈4%), indicating downstream vascular impedance mismatch. Although wave speed was significantly correlated to disease severity, wave reflection indexes of patients with mildly and severely elevated pulmonary pressures were similar. CONCLUSIONS: Wave reflection in the pulmonary artery increased in PH and was unrelated to severity, suggesting that vascular impedance mismatch occurs early in the development of pulmonary vascular disease. The lower wave power fraction in PAH compared with CTEPH indicates differences in the intrinsic and/or extrinsic ventricular load between the 2 diseases.
Sluyter JD, Camargo CA, Stewart AW, et al., 2017, Effect of Monthly, High-Dose, Long-Term Vitamin D Supplementation on Central Blood Pressure Parameters: A Randomized Controlled Trial Substudy., Journal of the American Heart Association, Vol: 6, ISSN: 2047-9980
BACKGROUND: The effects of monthly, high-dose, long-term (≥1-year) vitamin D supplementation on central blood pressure (BP) parameters are unknown. METHODS AND RESULTS: A total of 517 adults (58% male, aged 50-84 years) were recruited into a double-blinded, placebo-controlled trial substudy and randomized to receive, for 1.1 years (median; range: 0.9-1.5 years), either (1) vitamin D3 200 000 IU (initial dose) followed 1 month later by monthly 100 000-IU doses (n=256) or (2) placebo monthly (n=261). At baseline (n=517) and follow-up (n=380), suprasystolic oscillometry was undertaken, yielding aortic BP waveforms and hemodynamic parameters. Mean deseasonalized 25-hydroxyvitamin D increased from 66 nmol/L (SD: 24) at baseline to 122 nmol/L (SD: 42) at follow-up in the vitamin D group, with no change in the placebo group. Despite small, nonsignificant changes in hemodynamic parameters in the total sample (primary outcome), we observed consistently favorable changes among the 150 participants with vitamin D deficiency (<50 nmol/L) at baseline. In this subgroup, mean changes in the vitamin D group (n=71) versus placebo group (n=79) were -5.3 mm Hg (95% confidence interval [CI], -11.8 to 1.3) for brachial systolic BP (P=0.11), -2.8 mm Hg (95% CI, -6.2 to 0.7) for brachial diastolic BP (P=0.12), -7.5 mm Hg (95% CI, -14.4 to -0.6) for aortic systolic BP (P=0.03), -5.7 mm Hg (95% CI, -10.8 to -0.6) for augmentation index (P=0.03), -0.3 m/s (95% CI, -0.6 to -0.1) for pulse wave velocity (P=0.02), -8.6 mm Hg (95% CI, -15.4 to -1.9) for peak reservoir pressure (P=0.01), and -3.6 mm Hg (95% CI, -6.3 to -0.8) for backward pressure amplitude (P=0.01). CONCLUSIONS: Monthly, high-dose, 1-year vitamin D supplementation lowered central BP parameters among adults with vitamin D deficiency but not in the total sample. CLINICAL TRIAL REGISTRATION: URL: http://www.anzctr.org.au. Unique identifier: ACTRN12611000402943.
Narayan O, Parker KH, Davies JE, et al., 2017, Reservoir pressure analysis of aortic blood pressure: an in-vivo study at five locations in humans, JOURNAL OF HYPERTENSION, Vol: 35, Pages: 2025-2033, ISSN: 0263-6352
Negoita M, Hughes AD, Parker KH, et al., 2017, Non-invasive Technique for Determining Local Pulse Wave Velocity in Humans Ascending Aorta, 44th Computing in Cardiology Conference (CinC), Publisher: IEEE COMPUTER SOC, ISSN: 0276-6574
Su J, Manisty C, Simonsen U, et al., 2017, Pulmonary artery wave propagation and reservoir function in conscious man: impact of pulmonary vascular disease, respiration and dynamic stress tests, JOURNAL OF PHYSIOLOGY-LONDON, Vol: 595, Pages: 6463-6476, ISSN: 0022-3751
Detailed haemodynamic analysis may provide novel insights into the pulmonary circulation. Therefore, wave intensity and reservoir-excess pressure analyses were applied in the pulmonary artery to characterize changes in wave propagation and reservoir function during spontaneous respiration and dynamic stress tests. Right heart catheterization was performed using a pressure and Doppler flow sensor tipped guidewire to obtain simultaneous pressure and flow velocity measurements in the pulmonary artery in control subjects and patients with pulmonary arterial hypertension (PAH) at rest. In controls, recordings were also obtained during Valsalva manoeuvre and handgrip exercise. The asymptotic pressure at which the flow through the microcirculation ceases, the reservoir pressure related to arterial compliance and the excess pressure caused by arterial waves increased in PAH patients compared to controls. The systolic and diastolic rate constants also increased, while the diastolic time constant decreased. The forward compression wave energy decreased by ∼8% in controls and ∼6% in PAH patients during expiration compared to inspiration, while the wave speed remained unchanged throughout the respiratory cycle. Wave energy decreased during Valsalva manoeuvre (by ∼45%) and handgrip exercise (by ∼27%) with unaffected wave speed. Moreover, the reservoir and excess pressures decreased during Valsalva manoeuvre but remained unaltered during handgrip exercise. In conclusion, reservoir-excess pressure analysis applied to the pulmonary artery revealed distinctive differences between controls and PAH patients. Variations in the ventricular preload and afterload influence pulmonary arterial wave propagation as demonstrated by changes in wave energy during spontaneous respiration and dynamic stress tests.
Aizawa K, Casanova F, Mawson DM, et al., 2017, RESERVOIR-PRESSURE ANALYSIS PREDICTS CARDIOVASCULAR EVENTS IN INDIVIDUALS WITH TYPE 2 DIABETES: A SINGLE-CENTRE STUDY, Publisher: LIPPINCOTT WILLIAMS & WILKINS, Pages: E248-E249, ISSN: 0263-6352
Segers P, O'Rourke MF, Parker K, et al., 2017, Towards a consensus on the understanding and analysis of the pulse waveform: Results from the 2016 Workshop on Arterial Hemodynamics: Past, present and future, ARTERY RESEARCH, Vol: 18, Pages: 75-80, ISSN: 1872-9312
Parker KH, 2017, The reservoir-wave model, ARTERY RESEARCH, Vol: 18, Pages: 87-101, ISSN: 1872-9312
Ntsinjana HN, Chung R, Ciliberti P, et al., 2017, Utility of cardiovascular Magnetic resonance-Derived Wave intensity analysis as a Marker of Ventricular Function in children with heart Failure and normal ejection Fraction, FRONTIERS IN PEDIATRICS, Vol: 5, ISSN: 2296-2360
Broyd CJ, Davies JE, Escaned JE, et al., 2017, Wave intensity analysis and its application to the coronary circulation., Global Cardiology Science & Practice, Vol: 2017, ISSN: 2305-7823
Wave intensity analysis (WIA) is a technique developed from the field of gas dynamics that is now being applied to assess cardiovascular physiology. It allows quantification of the forces acting to alter flow and pressure within a fluid system, and as such it is highly insightful in ascribing cause to dynamic blood pressure or velocity changes. When co-incident waves arrive at the same spatial location they exert either counteracting or summative effects on flow and pressure. WIA however allows waves of different origins to be measured uninfluenced by other simultaneously arriving waves. It therefore has found particular applicability within the coronary circulation where both proximal (aortic) and distal (myocardial) ends of the coronary artery can markedly influence blood flow. Using these concepts, a repeating pattern of 6 waves has been consistently identified within the coronary arteries, 3 originating proximally and 3 distally. Each has been associated with a particular part of the cardiac cycle. The most clinically relevant wave to date is the backward decompression wave, which causes the marked increase in coronary flow velocity observed at the start of the diastole. It has been proposed that this wave is generated by the elastic re-expansion of the intra-myocardial blood vessels that are compressed during systolic contraction. Particularly by quantifying this wave, WIA has been used to provide mechanistic and prognostic insight into a number of conditions including aortic stenosis, left ventricular hypertrophy, coronary artery disease and heart failure. It has proven itself to be highly sensitive and as such a number of novel research directions are encouraged where further insights would be beneficial.
Sluyter JD, Hughes AD, Thom SAMG, et al., 2016, Arterial waveform parameters in a large, population-based sample of adults: relationships with ethnicity and lifestyle factors, Journal of Human Hypertension, Vol: 31, Pages: 305-312, ISSN: 0950-9240
Little is known about how aortic waveform parameters vary with ethnicity and lifestyle factors. We investigated these issues in a large, population-based sample. We carried out a cross-sectional analysis of 4798 men and women, aged 50–84 years from Auckland, New Zealand. Participants were 3961 European, 321 Pacific, 266 Maori and 250 South Asian people. We assessed modifiable lifestyle factors via questionnaires, and measured body mass index (BMI) and brachial blood pressure (BP). Suprasystolic oscillometry was used to derive aortic pressure, from which several haemodynamic parameters were calculated. Heavy alcohol consumption and BMI were positively related to most waveform parameters. Current smokers had higher levels of aortic augmentation index than non-smokers (difference=3.7%, P<0.0001). Aortic waveform parameters, controlling for demographics, antihypertensives, diabetes and cardiovascular disease (CVD), were higher in non-Europeans than in Europeans. Further adjustment for brachial BP or lifestyle factors (particularly BMI) reduced many differences but several remained. Despite even further adjustment for mean arterial pressure, pulse rate, height and total:high-density lipoprotein cholesterol, compared with Europeans, South Asians had higher levels of all measured aortic waveform parameters (for example, for backward pressure amplitude: β=1.5 mm Hg; P<0.0001), whereas Pacific people had 9% higher loge (excess pressure integral) (P<0.0001). In conclusion, aortic waveform parameters varied with ethnicity in line with the greater prevalence of CVD among non-white populations. Generally, this was true even after accounting for brachial BP, suggesting that waveform parameters may have increased usefulness in capturing ethnic variations in cardiovascular risk. Heavy alcohol consumption, smoking and especially BMI may partially contribute to elevated levels of these parameters.
Raphael CE, Keegan J, Parker KH, et al., 2016, Feasibility of cardiovascular magnetic resonance derived coronary wave intensity analysis, Journal of Cardiovascular Magnetic Resonance, Vol: 18, ISSN: 1532-429X
BackgroundWave intensity analysis (WIA) of the coronary arteries allows description of the predominant mechanisms influencing coronary flow over the cardiac cycle. The data are traditionally derived from pressure and velocity changes measured invasively in the coronary artery. Cardiovascular magnetic resonance (CMR) allows measurement of coronary velocities using phase velocity mapping and derivation of central aortic pressure from aortic distension. We assessed the feasibility of WIA of the coronary arteries using CMR and compared this to invasive data.MethodsCMR scans were undertaken in a serial cohort of patients who had undergone invasive WIA. Velocity maps were acquired in the proximal left anterior descending and proximal right coronary artery using a retrospectively-gated breath-hold spiral phase velocity mapping sequence with high temporal resolution (19 ms). A breath-hold segmented gradient echo sequence was used to acquire through-plane cross sectional area changes in the proximal ascending aorta which were used as a surrogate of an aortic pressure waveform after calibration with brachial blood pressure measured with a sphygmomanometer. CMR-derived aortic pressures and CMR-measured velocities were used to derive wave intensity. The CMR-derived wave intensities were compared to invasive data in 12 coronary arteries (8 left, 4 right). Waves were presented as absolute values and as a % of total wave intensity. Intra-study reproducibility of invasive and non-invasive WIA was assessed using Bland-Altman analysis and the intraclass correlation coefficient (ICC).ResultsThe combination of the CMR-derived pressure and velocity data produced the expected pattern of forward and backward compression and expansion waves. The intra-study reproducibility of the CMR derived wave intensities as a % of the total wave intensity (mean ± standard deviation of differences) was 0.0 ± 6.8%, ICC = 0.91. Intra-study reproducib
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