Publications by authors named "Amy E Burchell"

22 Publications

  • Page 1 of 1

Retrograde blood flow in the internal jugular veins of humans with hypertension may have implications for cerebral arterial blood flow.

Eur Radiol 2020 Jul 10;30(7):3890-3899. Epub 2020 Mar 10.

BHI CardioNomics Research Group, Clinical Research and Imaging Centre-Bristol, School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, BS8 1TD, UK.

Objectives: To use multi-parametric magnetic resonance imaging (MRI) to test the hypothesis that hypertensives would have higher retrograde venous blood flow (RVBF) in the internal jugular veins (IJV) vs. normotensives, and that this would inversely correlate with arterial inflow and gray matter, white matter, and cerebrospinal fluid volumes.

Methods: Following local institutional review board approval and written consent, a prospective observational 3-T MRI study of 42 hypertensive patients (53 ± 2 years, BMI 28.2 ± 0.6 kg/m, ambulatory daytime systolic BP 148 ± 2 mmHg, ambulatory daytime diastolic BP 101 ± 2 mmHg) and 35 normotensive patients (48 ± 2 years, BMI 25.2 ± 0.8 kg/m, ambulatory daytime systolic BP 119 ± 3 mmHg, ambulatory daytime diastolic BP 90 ± 2 mmHg) was performed. Phase contrast imaging calculated percentage retrograde venous blood flow (%RVBF), brain segmentation estimated regional brain volumes from 3D T1-weighted images, and pseudo-continuous arterial spin labeling measured regional cerebral blood perfusion. Statistical analysis included two-sample equal variance Student's T tests, two-way analysis of variance with Tukey's post hoc correction, and permutation-based two-group general linear modeling (p < 0.05).

Results: In the left IJV, %RVBF was higher in hypertensives (6.1 ± 1.5%) vs. normotensives (1.1 ± 0.3%, p = 0.003). In hypertensives, there was an inverse relationship of %RVBF (permutation-based general linear modeling) to cerebral blood flow in several brain regions, including the left occipital pole and the cerebellar vermis (p < 0.01). Percentage retrograde flow in the left IJV correlated inversely with the total matter volume (gray plus white matter volume) in hypertensives (r = - 0.49, p = 0.004).

Conclusion: RVBF in the left IJV is greater in hypertensives vs. normotensives and is linked to regional hypoperfusion and brain total matter volume.

Key Points: • Hypertensive humans have higher retrograde cerebral venous blood flow, associated with regional brain hypoperfusion and lower tissue volume, compared with controls. • Cerebral retrograde venous blood flow may add further stress to already hypoperfused tissue in hypertensive patients. • The amount of retrograde venous blood flow in hypertensive patients may predict which patients might be at higher risk of developing cerebral pathologies.
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http://dx.doi.org/10.1007/s00330-020-06752-6DOI Listing
July 2020

Cerebral Blood Flow Response to Simulated Hypovolemia in Essential Hypertension: A Magnetic Resonance Imaging Study.

Hypertension 2019 12 28;74(6):1391-1398. Epub 2019 Oct 28.

From the Faculty of Life Sciences, School of Physiology, Pharmacology and Neuroscience (S.N., Z.H.A., J.B., A.K.N., J.P., E.C.H.), University of Bristol, United Kingdom.

Hypertension is associated with raised cerebral vascular resistance and cerebrovascular remodeling. It is currently unclear whether the cerebral circulation can maintain cerebral blood flow (CBF) during reductions in cardiac output (CO) in hypertensive patients thereby avoiding hypoperfusion of the brain. We hypothesized that hypertension would impair the ability to effectively regulate CBF during simulated hypovolemia. In the present study, 39 participants (13 normotensive, 13 controlled, and 13 uncontrolled hypertensives; mean age±SD, 55±10 years) underwent lower body negative pressure (LBNP) at -20, -40, and -50 mmHg to decrease central blood volume. Phase-contrast MR angiography was used to measure flow in the basilar and internal carotid arteries, as well as the ascending aorta. CBF and CO decreased during LBNP (<0.0001). Heart rate increased during LBNP, reaching significance at -50 mmHg (<0.0001). There was no change in mean arterial pressure during LBNP (=0.3). All participants showed similar reductions in CBF (=0.3, between groups) and CO (=0.7, between groups) during LBNP. There was no difference in resting CBF between the groups (=0.36). In summary, during reductions in CO induced by hypovolemic stress, mean arterial pressure is maintained but CBF declines indicating that CBF is dependent on CO in middle-aged normotensive and hypertensive volunteers. Hypertension is not associated with impairments in the CBF response to reduced CO.
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http://dx.doi.org/10.1161/HYPERTENSIONAHA.119.13229DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7069391PMC
December 2019

Left ventricular extracellular volume fraction and atrioventricular interaction in hypertension.

Eur Radiol 2019 Mar 19;29(3):1574-1585. Epub 2018 Sep 19.

Department of Radiology, Bristol Royal Infirmary, University Bristol NHS Foundation Trust, Bristol, UK.

Objectives: Left atrial enlargement (LAE) predicts cardiovascular morbidity and mortality. Impaired LA function also confers poor prognosis. This study aimed to determine whether left ventricular (LV) interstitial fibrosis is associated with LAE and LA impairment in systemic hypertension.

Methods: Following informed written consent, a prospective observational study of 86 hypertensive patients (49 ± 15 years, 53% male, office SBP 168 ± 30 mmHg, office DBP 97 ± 4 mmHg) and 20 normotensive controls (48 ± 13 years, 55% male, office SBP 130 ± 13 mmHg, office DBP 80 ± 11 mmHg) at 1.5-T cardiovascular magnetic resonance was conducted. Extracellular volume fraction (ECV) was calculated by T1-mapping. LA volume (LAV) was measured with biplane area-length method. LA reservoir, conduit and pump function were calculated with the phasic volumetric method.

Results: Indexed LAV correlated with indexed LV mass (R = 0.376, p < 0.0001) and ECV (R = 0.359, p = 0.001). However, ECV was the strongest significant predictor of LAE in multivariate regression analysis (odds ratio [95th confidence interval] 1.24 [1.04-1.48], p = 0.017). Indexed myocardial interstitial volume was associated with significant reductions in LA reservoir (R = -0.437, p < 0.0001) and conduit (R = -0.316, p = 0.003) but not pump (R = -0.167, p = 0.125) function. Multiple linear regression, correcting for age, gender, BMI, BP and diabetes, showed an independent decrease of 3.5% LA total emptying fraction for each 10 ml/m increase in myocardial interstitial volume (standard β coefficient -3.54, p = 0.002).

Conclusions: LV extracellular expansion is associated with LAE and impaired LA reservoir and conduit function. Future studies should identify if targeting diffuse LV fibrosis is beneficial in reverse remodelling of LA structural and functional pathological abnormalities in hypertension.

Key Points: • Left atrial enlargement (LAE) and impairment are markers of adverse prognosis in systemic hypertension but their pathophysiology is poorly understood. • Left ventricular extracellular volume fraction was the strongest independent multivariate predictor of LAE and was associated with impaired left atrial reservoir and conduit function. • LV interstitial expansion may play a central role in the pathophysiology of adverse atrioventricular interaction in systemic hypertension.
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http://dx.doi.org/10.1007/s00330-018-5700-zDOI Listing
March 2019

Antihypertensive Treatment Fails to Control Blood Pressure During Exercise.

Hypertension 2018 07;72(1):102-109

From the Bristol Heart Institute (BHI) CardioNomics Research Group, Clinical Research and Imaging Centre, School of Physiology, Pharmacology, Neuroscience (B.C., M.B., T.H., J.F.R.P., E.C.H.)

An exaggerated blood pressure (BP) response to maximal exercise is an independent risk factor for cardiovascular events and mortality. It is unclear whether treating BP to guideline recommended levels could normalize the rise in BP during exercise, which is mediated by the metaboreflex. We aimed to assess the BP response to incremental exercise testing and metaboreflex activation in treated-controlled hypertension (n=16), treated-uncontrolled hypertension (n=16), and untreated hypertension (n=11) and 16 control participants with normal BP (n=16). All groups were matched for age and body mass index. BP was measured during an incremental Vo peak test on a cycle ergometer and during metaboreflex isolation using postexercise ischemia. Data were analyzed using 2-way ANOVA with Tukey test for multiple comparisons. Aerobic fitness was similar among groups (=0.97). The rise in absolute systolic BP from baseline at peak exercise was similar in controlled, uncontrolled, and untreated hypertension but greater compared with normotensive controls (Δ71±3, 81±7, 79±8.5 versus 47±5 mm Hg; =0.0001). Metaboreflex sensitivity was also similar in controlled, uncontrolled, and untreated hypertension but augmented compared with normotensive controls (Δsystolic BP: 21±2, 28±2, 25±3 versus 12±2 mm Hg; <0.0001). An amplified pressor response to exercise occurred in patients taking antihypertensive medication, despite having controlled BP at rest and was potentially caused (in part) by enhanced metaboreflex sensitivity. Poor BP control during exercise, partially mediated by the metaboreflex, may contribute to the heightened risk of an adverse cardiovascular event even in treated-controlled patients.
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http://dx.doi.org/10.1161/HYPERTENSIONAHA.118.11076DOI Listing
July 2018

Noctural dipping status and left ventricular hypertrophy: A cardiac magnetic resonance imaging study.

J Clin Hypertens (Greenwich) 2018 04 8;20(4):784-793. Epub 2018 Mar 8.

NIHR Bristol Cardiovascular Biomedical Research Unit, Cardiac Magnetic Resonance Department, Bristol Heart Institute, University Hospitals Bristol NHS Foundation Trust, Bristol, UK.

We investigate the impact of dipper status on cardiac structure with cardiovascular magnetic resonance (CMR). Ambulatory blood pressure monitoring and 1.5T CMR were performed in 99 tertiary hypertension clinic patients. Subgroup analysis by extreme dipper (n = 9), dipper (n = 39), non-dipper (n = 35) and reverse dipper (n = 16) status was performed, matched in age, gender and BMI. Left ventricular (LV) mass was significantly higher for extreme dippers than dippers after correction for covariates (100 ± 6 g/m vs 79 ± 3 g/m , P = .004). Amongst extreme dippers and dippers (n = 48), indexed LV mass correlated positively with the extent of nocturnal blood pressure dipping (R = .403, P = .005). On post-hoc ANCOVA, the percentage of nocturnal dip had significant effect on indexed LV mass (P = .008), but overall SBP did not (P = .348). In the tertiary setting, we found a larger nocturnal BP drop was associated with more LV hypertrophy. If confirmed in larger studies, this may have implications on nocturnal dosing of anti-hypertensive medications.
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http://dx.doi.org/10.1111/jch.13235DOI Listing
April 2018

Chronic Deep Brain Stimulation Decreases Blood Pressure and Sympathetic Nerve Activity in a Drug- and Device-Resistant Hypertensive Patient.

Hypertension 2017 04 27;69(4):522-528. Epub 2017 Feb 27.

From the School of Physiology and Pharmacology (E.L.O'C., E.C.H., J.F.R.P.), CardioNomics, Clinical Research and Imaging Centre (E.C.H., A.E.B., A.K.N., J.F.R.P.), University of Bristol, United Kingdom; Department of Neurosurgery (H.S.-W., S.J., N.K.P.), Department of Cardiology (M.P.), North Bristol NHS Trust, Southmead Hospital, United Kingdom; Department of Cardiology, Bristol Heart Institute, United Kingdom (A.E.B., A.K.N.); Institute for Clinical Pharmacology (J.T., K.H., J.J.) and Department of Nephrology (J.M., H.H.), Hannover Medical School, Germany; and Institute for Aerospace Medicine, German Center for Aerospace Medicine, Cologne, Germany (J.T., J.J.).

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http://dx.doi.org/10.1161/HYPERTENSIONAHA.116.08972DOI Listing
April 2017

The Relationship Between Left Ventricular Wall Thickness, Myocardial Shortening, and Ejection Fraction in Hypertensive Heart Disease: Insights From Cardiac Magnetic Resonance Imaging.

J Clin Hypertens (Greenwich) 2016 11 17;18(11):1119-1127. Epub 2016 Jun 17.

Medical School, Faculty of Medicine and Dentistry, University of Bristol, Bristol, UK.

Hypertensive heart disease is often associated with a preserved left ventricular ejection fraction despite impaired myocardial shortening. The authors investigated this paradox in 55 hypertensive patients (52±13 years, 58% male) and 32 age- and sex-matched normotensive control patients (49±11 years, 56% male) who underwent cardiac magnetic resonance imaging at 1.5T. Long-axis shortening (R=0.62), midwall fractional shortening (R=0.68), and radial strain (R=0.48) all decreased (P<.001) as end-diastolic wall thickness increased. However, absolute wall thickening (defined as end-systolic minus end-diastolic wall thickness) was maintained, despite the reduced myocardial shortening. Absolute wall thickening correlated with ejection fraction (R=0.70, P<.0001). In multiple linear regression analysis, increasing wall thickness by 1 mm independently increased ejection fraction by 3.43 percentage points (adjusted β-coefficient: 3.43 [2.60-4.26], P<.0001). Increasing end-diastolic wall thickness augments ejection fraction through preservation of absolute wall thickening. Left ventricular ejection fraction should not be used in patients with hypertensive heart disease without correction for degree of hypertrophy.
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http://dx.doi.org/10.1111/jch.12849DOI Listing
November 2016

Unilateral Carotid Body Resection in Resistant Hypertension: A Safety and Feasibility Trial.

JACC Basic Transl Sci 2016 Aug 29;1(5):313-324. Epub 2016 Aug 29.

School of Physiology, Pharmacology & Neuroscience, Biomedical Sciences, University of Bristol, Bristol, United Kingdom.

Animal and human data indicate pathological afferent signaling emanating from the carotid body that drives sympathetically mediated elevations in blood pressure in conditions of hypertension. This first-in-man, proof-of-principle study tested the safety and feasibility of unilateral carotid body resection in 15 patients with drug-resistant hypertension. The procedure proved to be safe and feasible. Overall, no change in blood pressure was found. However, 8 patients showed significant reductions in ambulatory blood pressure coinciding with decreases in sympathetic activity. The carotid body may be a novel target for treating an identifiable subpopulation of humans with hypertension.
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http://dx.doi.org/10.1016/j.jacbts.2016.06.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5063532PMC
August 2016

Comprehensive First-Line Magnetic Resonance Imaging in Hypertension: Experience From a Single-Center Tertiary Referral Clinic.

J Clin Hypertens (Greenwich) 2017 01 19;19(1):13-22. Epub 2016 Oct 19.

CardioNomics Research Group, Bristol Heart Institute, University Hospitals Bristol NHS Foundation Trust, University of Bristol, Bristol, UK.

European guidelines recommend that patients with hypertension be assessed for asymptomatic organ damage and secondary causes. The authors propose that a single magnetic resonance imaging (MRI) scan can provide comprehensive first-line imaging of patients assessed via a specialist hypertension clinic. A total of 200 patients (56% male, aged 51±15 years, office BP 168±30/96±16 mm Hg) underwent MRI of the heart, kidneys, renal arteries, adrenals and aorta. Comparisons were made with other imaging modalities where available. A total of 61% had left ventricular hypertrophy (LVH), 14% had reduced ejection fraction, and 15 patients had myocardial infarcts. Echocardiography overdiagnosed LVH in 15% of patients and missed LVH in 14%. Secondary causes were identified in 14.5% of patients: 12 adrenal masses, 10 renal artery stenoses, seven thyroid abnormalities, one aortic coarctation, one enlarged pituitary gland, one polycystic kidney disease, and one renal coloboma syndrome. This comprehensive MRI protocol is an effective method of screening for asymptomatic organ damage and secondary causes of hypertension.
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http://dx.doi.org/10.1111/jch.12920DOI Listing
January 2017

Is High Blood Pressure Self-Protection for the Brain?

Circ Res 2016 Dec 26;119(12):e140-e151. Epub 2016 Sep 26.

From the Cardiff University Brain Research Imaging Centre, School of Psychology, Cardiff University, United Kingdom (E.A.H.W., R.G.W.); CardioNomics Research Group, Clinical Research and Imaging Centre (J.C.L.R., A.E.B., S.N., L.E.K.R., N.E.M., A.K.N., J.F.R.P., E.C.H.) and School of Physiology, Pharmacology, and Neuroscience, Biomedical Sciences (J.C.L.R., S.N., L.E.K.R., Z.A., J.F.R.P., E.C.H.), University of Bristol, United Kingdom; University Hospitals Bristol NHS Foundation Trust, United Kingdom (S.N., L.E.K.R., Z.A., J.F.R.P., E.C.H.); Department of Radiology, University of Calgary, Canada (A.D.H.); and CAIR Program, Alberta Children's Hospital Research Institute, University of Calgary, Hotchkiss Brain Institute, Canada (A.D.H.).

Rationale: Data from animal models of hypertension indicate that high blood pressure may develop as a vital mechanism to maintain adequate blood flow to the brain. We propose that congenital vascular variants of the posterior cerebral circulation and cerebral hypoperfusion could partially explain the pathogenesis of essential hypertension, which remains enigmatic in 95% of patients.

Objective: To evaluate the role of the cerebral circulation in the pathophysiology of hypertension.

Methods And Results: We completed a series of retrospective and mechanistic case-control magnetic resonance imaging and physiological studies in normotensive and hypertensive humans (n=259). Interestingly, in humans with hypertension, we report a higher prevalence of congenital cerebrovascular variants; vertebral artery hypoplasia, and an incomplete posterior circle of Willis, which were coupled with increased cerebral vascular resistance, reduced cerebral blood flow, and a higher incidence of lacunar type infarcts. Causally, cerebral vascular resistance was elevated before the onset of hypertension and elevated sympathetic nerve activity (n=126). Interestingly, untreated hypertensive patients (n=20) had a cerebral blood flow similar to age-matched controls (n=28). However, participants receiving antihypertensive therapy (with blood pressure controlled below target levels) had reduced cerebral perfusion (n=19). Finally, elevated cerebral vascular resistance was a predictor of hypertension, suggesting that it may be a novel prognostic or diagnostic marker (n=126).

Conclusions: Our data indicate that congenital cerebrovascular variants in the posterior circulation and the associated cerebral hypoperfusion may be a factor in triggering hypertension. Therefore, lowering blood pressure may worsen cerebral perfusion in susceptible individuals.
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http://dx.doi.org/10.1161/CIRCRESAHA.116.309493DOI Listing
December 2016

Hypertensive heart disease versus hypertrophic cardiomyopathy: multi-parametric cardiovascular magnetic resonance discriminators when end-diastolic wall thickness ≥ 15 mm.

Eur Radiol 2017 Mar 1;27(3):1125-1135. Epub 2016 Jul 1.

NIHR Bristol Cardiovascular Biomedical Research Unit, Cardiac Magnetic Resonance Department, Bristol Heart Institute, University Hospitals Bristol NHS Foundation Trust, Upper Maudlin Street, Bristol, BS2 8HW, UK.

Objectives: European guidelines state left ventricular (LV) end-diastolic wall thickness (EDWT) ≥15mm suggests hypertrophic cardiomyopathy (HCM), but distinguishing from hypertensive heart disease (HHD) is challenging. We identify cardiovascular magnetic resonance (CMR) predictors of HHD over HCM when EDWT ≥15mm.

Methods: 2481 consecutive clinical CMRs between 2014 and 2015 were reviewed. 464 segments from 29 HCM subjects with EDWT ≥15mm but without other cardiac abnormality, hypertension or renal impairment were analyzed. 432 segments from 27 HHD subjects with EDWT ≥15mm but without concomitant cardiac pathology were analyzed. Magnitude and location of maximal EDWT, presence of late gadolinium enhancement (LGE), LV asymmetry (>1.5-fold opposing segment) and systolic anterior motion of the mitral valve (SAM) were measured. Multivariate logistic regression was performed. Significance was defined as p<0.05.

Results: HHD and HCM cohorts were age-/gender-matched. HHD had significantly increased indexed LV mass (110±27g/m vs. 91±31g/m, p=0.016) but no difference in site or magnitude of maximal EDWT. Mid-wall LGE was significantly more prevalent in HCM. Elevated indexed LVM, mid-wall LGE and absence of SAM were significant multivariate predictors of HHD, but LV asymmetry was not.

Conclusions: Increased indexed LV mass, absence of mid-wall LGE and absence of SAM are better CMR discriminators of HHD from HCM than EDWT ≥15mm.

Key Points: • Hypertrophic cardiomyopathy (HCM) is often diagnosed with end-diastolic wall thickness ≥15mm. • Hypertensive heart disease (HHD) can be difficult to distinguish from HCM. • Retrospective case-control study showed that location and magnitude of EDWT are poor discriminators. • Increased left ventricular mass and midwall fibrosis are independent predictors of HHD. • Cardiovascular magnetic resonance parameters facilitate a better discrimination between HHD and HCM.
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http://dx.doi.org/10.1007/s00330-016-4468-2DOI Listing
March 2017

ECG strain pattern in hypertension is associated with myocardial cellular expansion and diffuse interstitial fibrosis: a multi-parametric cardiac magnetic resonance study.

Eur Heart J Cardiovasc Imaging 2017 Apr;18(4):441-450

NIHR Bristol Cardiovascular Biomedical Research Unit, Bristol Heart Institute, University Hospitals Bristol NHS Foundation Trust, Upper Maudlin Street, Bristol BS2 8HW, UK.

Aims: In hypertension, the presence of left ventricular (LV) strain pattern on 12-lead electrocardiogram (ECG) carries adverse cardiovascular prognosis. The underlying mechanisms are poorly understood. We investigated whether hypertensive ECG strain is associated with myocardial interstitial fibrosis and impaired myocardial strain, assessed by multi-parametric cardiac magnetic resonance (CMR).

Methods And Results: A total of 100 hypertensive patients [50 ± 14 years, male: 58%, office systolic blood pressure (SBP): 170 ± 30 mmHg, office diastolic blood pressure (DBP): 97 ± 14 mmHg) underwent ECG and 1.5T CMR and were compared with 25 normotensive controls (46 ± 14 years, 60% male, SBP: 124 ± 8 mmHg, DBP: 76 ± 7 mmHg). Native T1 and extracellular volume fraction (ECV) were calculated with the modified look-locker inversion-recovery sequence. Myocardial strain values were estimated with voxel-tracking software. ECG strain (n = 20) was associated with significantly higher indexed LV mass (LVM) (119 ± 32 vs. 80 ± 17 g/m2, P < 0.05) and ECV (30 ± 4 vs. 27 ± 3%, P < 0.05) compared with hypertensive subjects without ECG strain (n = 80). ECG strain subjects had significantly impaired circumferential strain compared with hypertensive subjects without ECG strain and controls (-15.2 ± 4.7 vs. -17.0 ± 3.3 vs. -17.3 ± 2.4%, P < 0.05, respectively). In subgroup analysis, comparing ECG strain subjects to hypertensive subjects with elevated LVM but no ECG strain, a significantly higher ECV (30 ± 4 vs. 28 ± 3%, P < 0.05) was still observed. Indexed LVM was the only variable independently associated with ECG strain in multivariate logistic regression analysis [odds ratio (95th confidence interval): 1.07 (1.02-1.12), P < 0.05).

Conclusion: In hypertension, ECG strain is a marker of advanced LVH associated with increased interstitial fibrosis and associated with significant myocardial circumferential strain impairment.
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http://dx.doi.org/10.1093/ehjci/jew117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5837603PMC
April 2017

Comprehensive characterisation of hypertensive heart disease left ventricular phenotypes.

Heart 2016 10 3;102(20):1671-9. Epub 2016 Jun 3.

NIHR Bristol Cardiovascular Biomedical Research Unit, Cardiac Magnetic Resonance Department, Bristol Heart Institute, University Hospitals Bristol NHS Foundation Trust, Bristol, UK Department of Cardiology, Bristol Royal Infirmary, University Hospitals Bristol NHS Foundation Trust, Bristol, UK.

Objective: Myocardial intracellular/extracellular structure and aortic function were assessed among hypertensive left ventricular (LV) phenotypes using cardiovascular magnetic resonance (CMR).

Methods: An observational study from consecutive tertiary hypertension clinic patients referred for CMR (1.5 T) was performed. Four LV phenotypes were defined: (1) normal with normal indexed LV mass (LVM) and LVM to volume ratio (M/V), (2) concentric remodelling with normal LVM but elevated M/V, (3) concentric LV hypertrophy (LVH) with elevated LVM but normal indexed end-diastolic volume (EDV) or (4) eccentric LVH with elevated LVM and EDV. Extracellular volume fraction was measured using T1-mapping. Circumferential strain was calculated by voxel-tracking. Aortic distensibility was derived from high-resolution aortic cines and contemporaneous blood pressure measurements.

Results: 88 hypertensive patients (49±14 years, 57% men, systolic blood pressure (SBP): 167±30 mm Hg, diastolic blood pressure (DBP): 96±14 mm Hg) were compared with 29 age-matched/sex-matched controls (47±14 years, 59% men, SBP: 128±12 mm Hg, DBP: 79±10 mm Hg). LVH resulted from increased myocardial cell volume (eccentric LVH: 78±19 mL/m(2) vs concentric LVH: 73±15 mL/m(2) vs concentric remodelling: 55±9 mL/m(2), p<0.05, respectively) and interstitial fibrosis (eccentric LVH: 33±10 mL/m(2) vs concentric LVH: 30±10 mL/m(2) vs concentricremodelling: 19±2 mL/m(2), p<0.05, respectively). LVH had worst circumferential impairment (eccentric LVH: -12.8±4.6% vs concentric LVH: -15.5±3.1% vs concentric remodelling: -17.1±3.2%, p<0.05, respectively). Concentric remodelling was associated with reduced aortic distensibility, but not with large intracellular/interstitial expansion or myocardial dysfunction versus controls.

Conclusions: Myocardial interstitial fibrosis varies across hypertensive LV phenotypes with functional consequences. Eccentric LVH has the most fibrosis and systolic impairment. Concentric remodelling is only associated with abnormal aortic function. Understanding these differences may help tailor future antihypertensive treatments.
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http://dx.doi.org/10.1136/heartjnl-2016-309576DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5099214PMC
October 2016

Controversies Surrounding Renal Denervation: Lessons Learned From Real-World Experience in Two United Kingdom Centers.

J Clin Hypertens (Greenwich) 2016 06 9;18(6):585-92. Epub 2016 Feb 9.

CardioNomics Research Group, Clinical Research & Imaging Centre-Bristol, Bristol Heart Institute, University Hospitals Bristol NHS Foundation Trust, University of Bristol, Bristol, UK.

Renal denervation (RDN) is a therapy that targets treatment-resistant hypertension (TRH). The Renal Denervation in Patients With Uncontrolled Hypertension (Symplicity) HTN-1 and Symplicity HTN-2 trials reported response rates of >80%; however, sham-controlled Symplicity HTN-3 failed to reach its primary blood pressure (BP) outcome. The authors address the current controversies surrounding RDN, illustrated with real-world data from two centers in the United Kingdom. In this cohort, 52% of patients responded to RDN, with a 13±32 mm Hg reduction in office systolic BP (SBP) at 6 months (n=29, P=.03). Baseline office SBP and number of ablations correlated with office SBP reduction (R=-0.47, P=.01; R=-0.56, P=.002). RDN appears to be an effective treatment for some patients with TRH; however, individual responses are highly variable. Selecting patients for RDN is challenging, with only 10% (33 of 321) of the screened patients eligible for the study. Medication alterations and nonadherence confound outcomes. Adequate ablation is critical and should impact future catheter design/training. Markers of procedural success and improved patient selection parameters remain key research aims.
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http://dx.doi.org/10.1111/jch.12789DOI Listing
June 2016

Renal artery sympathetic denervation: observations from the UK experience.

Clin Res Cardiol 2016 Jun 22;105(6):544-52. Epub 2016 Jan 22.

Radiology Department, Queen Elizabeth Hospital Birmingham, University Hospital Birmingham NHS Trust, Edgbaston, Birmingham, B15 2TH, UK.

Background: Renal denervation (RDN) may lower blood pressure (BP); however, it is unclear whether medication changes may be confounding results. Furthermore, limited data exist on pattern of ambulatory blood pressure (ABP) response-particularly in those prescribed aldosterone antagonists at the time of RDN.

Methods: We examined all patients treated with RDN for treatment-resistant hypertension in 18 UK centres.

Results: Results from 253 patients treated with five technologies are shown. Pre-procedural mean office BP (OBP) was 185/102 mmHg (SD 26/19; n = 253) and mean daytime ABP was 170/98 mmHg (SD 22/16; n = 186). Median number of antihypertensive drugs was 5.0: 96 % ACEi/ARB; 86 % thiazide/loop diuretic and 55 % aldosterone antagonist. OBP, available in 90 % at 11 months follow-up, was 163/93 mmHg (reduction of 22/9 mmHg). ABP, available in 70 % at 8.5 months follow-up, was 158/91 mmHg (fall of 12/7 mmHg). Mean drug changes post RDN were: 0.36 drugs added, 0.91 withdrawn. Dose changes appeared neutral. Quartile analysis by starting ABP showed mean reductions in systolic ABP after RDN of: 0.4; 6.5; 14.5 and 22.1 mmHg, respectively (p < 0.001 for trend). Use of aldosterone antagonist did not predict response (p > 0.2).

Conclusion: In 253 patients treated with RDN, office BP fell by 22/9 mmHg. Ambulatory BP fell by 12/7 mmHg, though little response was seen in the lowermost quartile of starting blood pressure. Fall in BP was not explained by medication changes and aldosterone antagonist use did not affect response.
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http://dx.doi.org/10.1007/s00392-015-0959-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4882343PMC
June 2016

Prevalence and predictors of asymmetric hypertensive heart disease: insights from cardiac and aortic function with cardiovascular magnetic resonance.

Eur Heart J Cardiovasc Imaging 2016 Dec 24;17(12):1405-1413. Epub 2015 Dec 24.

NIHR Bristol Cardiovascular Biomedical Research Unit, Cardiac Magnetic Resonance Department, Bristol Heart Institute, University Hospitals Bristol NHS Foundation Trust, Upper Maudlin Street, Bristol BS2 8HW, UK.

Aims: We sought to determine the prevalence of asymmetric hypertensive heart disease (HHD) overlapping morphologically with hypertrophic cardiomyopathy (HCM) and to determine predictors of this pattern of hypertensive remodelling.

Methods And Results: One hundred and fifty hypertensive patients underwent 1.5 T cardiovascular magnetic resonance imaging. Twenty-one patients were excluded due to concomitant cardiac pathology that may confound the hypertrophic response, e.g. myocardial infarction, moderate-severe valvular disease, or other cardiomyopathy. Asymmetric HHD was defined as a segmental wall thickness of ≥15 mm and >1.5-fold the opposing wall in ≥1 myocardial segments, measured from short-axis cine stack at end-diastole. Ambulatory blood pressure, myocardial replacement fibrosis, aortic distensibility and aortoseptal angle were investigated as predictors of asymmetric HHD by multivariate logistic regression. Out of 129 hypertensive subjects (age: 51 ± 15 years, 50% male, systolic blood pressure: 170 ± 30 mmHg, diastolic blood pressure: 97 ± 16 mmHg), asymmetric HHD occurred in 21%. Where present, maximal end-diastolic wall thickness (EDWT) was 17.8 ± 1.9 mm and located exclusively in the basal or mid septum. In asymmetric HHD, aortoseptal angle (114 ± 10° vs. 125 ± 9° vs. 123 ± 12°, P < 0.05, respectively) was significantly reduced compared to concentric left ventricular hypertrophy (LVH) and compared to no LVH, respectively. Aortic distensibility in asymmetric HHD (1.01 ± 0.60 vs. 1.83 ± 1.65 mm/mmHg × 10, P < 0.05, respectively) was significantly reduced compared to subjects with no LVH. Age (odds ratio [95th confidence interval]: 1.10 [1.02-1.18], P < 0.05) and indexed LV mass (1.09 [0.98-1.28], P < 0.0001) were significant, independent predictors of asymmetric HDD.

Conclusions: Asymmetric HHD morphologically overlapping with HCM, according to the current ESC guidelines, is common. Postulating a diagnosis of HCM on the basis of EDWT of ≥15 mm should be made with caution in the presence of arterial hypertension particular in male subjects with elevated LV mass.
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http://dx.doi.org/10.1093/ehjci/jev329DOI Listing
December 2016

Deep brain stimulation for the treatment of resistant hypertension.

Curr Hypertens Rep 2014 Nov;16(11):493

School of Physiology & Pharmacology, University of Bristol, Bristol, BS8 1TD, UK.

Hypertension is a leading risk factor for the development of several cardiovascular diseases. As the global prevalence of hypertension increases, so too has the recognition of resistant hypertension. Whilst figures vary, the proportion of hypertensive patients that are resistant to multiple drug therapies have been reported to be as high as 16.4 %. Resistant hypertension is typically associated with elevated sympathetic activity and abnormal homeostatic reflex control and is termed neurogenic hypertension because of its presumed central autonomic nervous system origin. This resistance to conventional pharmacological treatment has stimulated a plethora of medical devices to be investigated for use in hypertension, with varying degrees of success. In this review, we discuss a new therapy for drug-resistant hypertension, deep brain stimulation. The utility of deep brain stimulation in resistant hypertension was first discovered in patients with concurrent neuropathic pain, where it lowered blood pressure and improved baroreflex sensitivity. The most promising central target for stimulation is the ventrolateral periaqueductal gray, which has been well characterised in animal studies as a control centre for autonomic outflow. In this review, we will discuss the promise and potential mechanisms of deep brain stimulation in the treatment of severe, resistant hypertension.
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http://dx.doi.org/10.1007/s11906-014-0493-1DOI Listing
November 2014

Arteriovenous anastomosis: is this the way to control hypertension?

Hypertension 2014 Jul 7;64(1):6-12. Epub 2014 Apr 7.

From the CardioNomics Research Group, Clinical Research & Imaging Centre-Bristol, Bristol Heart Institute, University Hospitals Bristol NHS Foundation Trust (A.E.B., J.F.R.P.) and School of Clinical Sciences (A.E.B.), University of Bristol, UK; William Harvey Heart Centre, NIHR Cardiovascular Biomedical Research Unit, Centre for Clinical Pharmacology, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, UK (M.D.L.); Barts Hypertension Clinic, Department of Clinical Pharmacology, Barts Health NHS Trust, London, UK (M.D.L.); Eastbourne DG Hospital, Kings Drive, Eastbourne, East Sussex, UK (N.S.); Rox Medical Inc. & The Ohio State University, St Paul, MN (P.A.S.); and School of Physiology & Pharmacology, Bristol CardioVascular, Medical Sciences Building, University of Bristol, UK (J.F.R.P.).

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http://dx.doi.org/10.1161/HYPERTENSIONAHA.114.02925DOI Listing
July 2014

Translational examination of changes in baroreflex function after renal denervation in hypertensive rats and humans.

Hypertension 2013 Sep 1;62(3):533-41. Epub 2013 Jul 1.

School of Physiology and Pharmacology, Bristol Heart Institute, Medical Science Bldg, University of Bristol, Bristol, United Kingdom.

Renal denervation has shown promise in the treatment of resistant hypertension, although the mechanisms underlying the blood pressure (BP) reduction remain unclear. In a translational study of spontaneously hypertensive rats (n=7, surgical denervation) and resistant hypertensive human patients (n=8; 5 men, 33-71 years), we examined the relationship among changes in BP, sympathetic nerve activity, and cardiac and sympathetic baroreflex function after renal denervation. In humans, mean systolic BP (SBP; sphygmomanometry) and muscle sympathetic nerve activity (microneurography) were unchanged at 1 and 6 months after renal denervation (P<0.05). Interestingly, 4 of 8 patients showed a 10% decrease in SBP at 6 months, but sympathetic activity did not necessarily change in parallel with SBP. In contrast, all rats showed significant and immediate decreases in telemetric SBP and lumbar sympathetic activity (P<0.05), 7 days after denervation. Despite no change in SBP, human cardiac and sympathetic baroreflex function (sequence and threshold techniques) showed improvements at 1 and 6 months after denervation, particularly through increased sympathetic baroreflex sensitivity to falling BP. This was mirrored in spontaneously hypertensive rats; cardiac and sympathetic baroreflex sensitivity (spontaneous sequence and the Oxford technique) improved 7 days after denervation. The more consistent results in rats may be because of a more complete (>90% reduction in renal norepinephrine content) denervation. We conclude that (1) renal denervation improves BP in some patients, but sympathetic activity does not always change in parallel, and (2) baroreflex sensitivity is consistently improved in animals and humans, even when SBP has not decreased. Determining procedural success will be crucial in advancing this treatment modality.
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http://dx.doi.org/10.1161/HYPERTENSIONAHA.113.01261DOI Listing
September 2013

Chemohypersensitivity and autonomic modulation of venous capacitance in the pathophysiology of acute decompensated heart failure.

Curr Heart Fail Rep 2013 Jun;10(2):139-46

Bristol CardioNomics Group, Bristol Heart Institute, Bristol Royal Infirmary, Bristol, BS2 8HW, UK.

Heart failure is increasing in prevalence around the world, with hospitalization and re-hospitalization as a result of acute decompensated heart failure (ADHF) presenting a huge social and economic burden. The mechanism for this decompensation is not clear. Whilst in some cases it is due to volume expansion, over half of patients with an acute admission for ADHF did not experience an increase in total body weight. This calls into question the current treatment strategy of targeting salt and water retention in ADHF. An alternative hypothesis proposed by Fallick et al. is that an endogenous fluid shift from the splanchnic bed is implicated in ADHF, rather than an exogenous fluid gain. The hypothesis states further that this shift is triggered by an increase in sympathetic tone causing vasoconstriction in the splanchnic bed, a mechanism that can translocate blood rapidly into the effective circulating volume, generating the raised venous pressure and congestion seen in ADHF. This hypothesis encourages a new clinical paradigm which focuses on the underlying mechanisms of congestion, and highlights the importance of fluid redistribution and neurohormonal activation in its pathophysiology. In this article, we consider the concept that ADHF is attributable to episodic sympathetic hyperactivity, resulting in fluid shifts from the splanchnic bed. Chemosensitivity is a pathologic autonomic mechanism associated with mortality in patients with systolic heart failure. Tonic and episodic activity of the peripheral chemoreceptors may underlie the syndrome of acute decompensation without total body salt and water expansion. We suggest in this manuscript that chemosensitivity in response to intermittent hypoxia, such as experienced in sleep disordered breathing, may explain the intermittent sympathetic hyperactivity underlying renal sodium retention and acute volume redistribution from venous storage sites. This hypothesis provides an alternative structure to guide novel diagnostic and treatment strategies for ADHF.
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http://dx.doi.org/10.1007/s11897-013-0135-yDOI Listing
June 2013