ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood...

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Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai, SG Anderson, N Sattar, J Finn, F Wu & JK Cruickshank * Cardiovascular & Endocrine Sciences University of Manchester & Glasgow Royal Infirmary * Now @ King’s College & St Thomas’ Hospital, London

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Page 1: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Ethnic differences in aortic pulse wave velocity occur in the

descending aorta independent of blood pressure and may be related

to vitamin D

MR Rezai, SG Anderson, N Sattar, J Finn, F Wu & JK Cruickshank*

Cardiovascular & Endocrine SciencesUniversity of Manchester & Glasgow Royal Infirmary

*Now @ King’s College & St Thomas’ Hospital,

London

Page 2: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Background

• Increasing evidence suggests that vitamin D may have an important role in modifying risk of cardiometabolic outcomes.

• Cross-sectional & prospective studies (and meta-analyses of these) have shown an independent inverse association between blood 25-OH vitamin D and CVD risk factors including BP, diabetes and dyslipidemia

Page 3: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Meta-analysis of CVD incidence and mortality

About 50% increased risk of CVD incidence and mortality in the lowest

compared to the highest categories of vitamin D (pooled HR = 1.54 [1.22–

1.95])

Grandi et al. 2010. Prev Med. 51(3-4):228-33

Page 4: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Reduced odds (24%) of hypertension for the highest vs. the lowest category of vitamin D

Burgaz et al 2011. Journal of Hypertension. 29(4):636-45

Page 5: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Most of Northern Europe vitamin D deplete or deficient through winter -

and beyond• Setting - North West Britain (2009-2010)

• Population – 724 General Medicine OPD clinic attendees

assessed for vitamin D status

• Vitamin D deficiency - 75% with vit D <40 ng/ml **

• Vitamin D deplete - 23% <20 ng/ml#; 33% were South

Asian

• 10% & 15% overtly vitamin D deficient## and South Asian

**’recommended’ #’deplete’ ## <10ng/ml

Data courtesy of Prof R Malik

Page 6: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Study Aims & Hypotheses

i. To Calibrate the Arteriograph against MR

ii. To examine the role of vitamin D on arterial stiffness - & its relation to ethnic differences in CVD

Hypotheses:

• Vitamin D would correlate closely with PWV, in relation to vascular risk

• People with melanised skin (eg: South Asian & Caribbean-origin), for given BP levels, have stiffer arteries in line with Vitamin D levels, independent of other Risk Factors

Page 7: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Study participants

• 198 men aged 40 to 80 years of AfC,

SA, and European origin previously

recruited to the European Male

Ageing Study*.

• The participants had to be free of

severe chronic or acute disease

*N Engl J Med 2010; 363:123-135

Page 8: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

The Arteriograph device was used to measure arterial stiffness indices, including

total aPWV• Measurements were

performed ≥2 times on

the left arm after ≥5

minutes of rest supine

after BP measurement.

• The difference in time

between the beginning of

the 1st wave and 2nd

(reflected wave) is divided

into the distance from

sternal notch to pubic

symphysis.

Page 9: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Arteriograph aPWV estimates calibrated with MRI-derived

Aortic Lengths• Comparison of MR-derived total aortic lengths

indicated an over estimate of real aortic path

using external landmarks.

• Mean difference 7cms (SD 2.8)

• Transit times similar

• Consequently, we recalculated Arteriograph

aPWV using transit times measured by device

and length of aortic path estimated by a

regression model from MR

Page 10: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Study Characteristics by ethnicity

S Asian (n=65)

Af-C’bean (n=64)

European (n=62)

Age (yr) 55±10 54±10 56±8 SBP 124±15 < 129±16 126±13 DBP (mmHg) 78±10 < 82±11 81±8 PP 46±

9 48±10 45±7

HR (bpm) 68±11 > 64±8 > 61±8 BMI 27±3 28±5 27±4

ArterialStiffness PWV (m/s) 8.1±1.5 > 7.2±1.2 < 7.8±1.

4 central BP 125±19 127±20 124±12

Page 11: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Vitamin D levels by Ethnic group & regression results for PWV

Ethnic effect diminished / absentP<0.01 lower

Page 12: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

MRI sub-study

• Randomly selected MRI study

participants (n=47) consisting of 16

Caribbean, 13 Pakistani, and 18

European men

Page 13: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Regional MR PWV derived from sagittal views

(3 aortic paths - P1P2, P2P3, and P1P3)

• The MR protocol for PWV

measurement used a 1.5-T Philips

Intera scanner to acquire 2

consecutive transverse images:

– One from aortic arch at

level of pulmonary artery

– The other 2cm above the

aortic bifurcation.

P1P1

P2

AV

Bif

P3

P1

P2

AV

Bif

P3

desPWV

arcPWV

P2

P3

Bif

aoP

WV

Page 14: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Regional PWV profiles across ethnicity.

Age-SBP adjusted mean desPWVMR in SAs was 0.7 m/s (0.3 m/s) and 0.8 m/s (0.3 m/s) greater than in AfCs and Europeans, respectively

Page 15: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Are the larger sample PWV data by Arteriograph replicated by MR?

Hypertension – Aug 2011

Page 16: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Summary

• Consistent with CVD risk among UK Caribbean, South

Asian and Europeans…

– SA men had higher (descending) aPWV, despite slightly

lower distending BPs, using a single point arm based

device (calibrated via MR)

– These changes were confirmed on an MR imaged sub-

sample

– Plasma vitamin D levels are related to aPWV & account

for much of the ethnic difference in aPWV

Page 17: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

THANK YOU

Page 18: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Abdominal aorta (bifurcation)

Aortic arch1

2

3

1 2

3

Abdominal aorta (bifurcation)

Aortic arch1

2

1

2

33

1 2

3

Flow curves from 3 sections(Transit time derived from P1P2, P2P3 and P1P3)

-35-30-25-20-15-10-505

101520253035404550556065707580859095

100105110115120125130135140145150155160165170175180185190195200205210215220225230235240

Asce Aorta flow [ml/s]

Desc Aort flow [ml/s]

Above Bifurc. Flex Coil flow [ml/s]1

2

3

-35-30-25-20-15-10-505

101520253035404550556065707580859095

100105110115120125130135140145150155160165170175180185190195200205210215220225230235240

Asce Aorta flow [ml/s]

Desc Aort flow [ml/s]

Above Bifurc. Flex Coil flow [ml/s]1

2

3

Arrival times of the aortic pulse waves were computed from the 3 flow-time curves recorded at the 3 points: P1, P2, and P3

10% of the slope of the flow wave from each site

Page 19: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Multiple regression model: risk factors related to aortic

stiffness = Pulse Wave Velocity (R2=0.36).

B

Per / 1 unit

SE B β Sig.

Constant -0.68 1.02 0.5

Age 0.05 0.01 0.35 <0.001 SBP 0.02 0.01 0.26 <0.001 HR 0.02 0.01 0.17 0.01

Diabetes 0.63 0.28 0.16 0.02 LDL/HDL Ratio 0.10 0.11 0.06 0.34

Smoking 0.31 0.17 0.11 0.07 Sth Asian # 0.73 0.23 0.25 0.001 European # 0.57 0.21 0.19 0.008

# vsAf C’beans

Page 20: Ethnic differences in aortic pulse wave velocity occur in the descending aorta independent of blood pressure and may be related to vitamin D MR Rezai,

Abdominal aorta (bifurcation)

Aortic arch1

2

3

1 2

3

Making PWV measures by MRI