Light exercise central blood pressure:A correlate of left ventricular mass that is simpler than 24 hour ambulatory blood pressure monitoring

SB. Thomas *, RL. Leano *, JK Brown *, DT. Gilroy *, JL. Hare *, TH. Marwick *, JE. Sharman *†.Cardiovascular Imaging Research Group, *The University of Queensland, Department of Medicine and †School of Human Movement Studies, Brisbane, AUSTRALIA.

Blood pressure measurement and CV Risk

• Hypertension is a leading risk factor for CVD1 & mortality2 - related to increases in left ventricular (LV) mass3.

• 24 hour ambulatory blood pressure monitoring (24ABPM) – Current gold standard for BP control as is strongest correlate for LV mass (r = 0.3)4.

1 Vasan R. N Engl J Med. (2001); 345:1291-97 2 Lewington S. Lancet (2002); 260: 1903-13 3Simone G. JACC 1995. 25(5): 1056-62 4 Mancia G. Circulation. 1997;95(6):1464-70.

Central Blood pressure and CV Risk

• Central BP – BP at the ascending aorta predicts CVD and mortality 1-4

1 London, G. (2001) 2 Pini, R. JACC (2008); 51(25):2432-39 3 Williams, B. Circ (2006); 113:1213-25 4 Safar, M. (2002); Hypertension; 39:735-38 5 Munir S. Hypertension. 2008;51(1):112-118.

GTF

• BP Monitoring during ADL = Gold Standard

• Large differences between central and upper arm SBP occur during light exercise similar to that of daily life1.

…This raises the possibility that light exercise central BP may provide more accurate estimations of BP control compared with the current gold standard

1 Sharman J. J Hypertens. 2007;25(6):1249-54.

Study Aims

1. To determine the association between light exercise central SBP (and radial P2 as a measure that is analogous to central SBP) with LV mass

2. To compare the strength of the associations between light exercise central SBP and 24 ABPM SBP with LV mass

Hypotheses

1. Central SBP and radial P2 during light exercise will be stronger correlates of LV mass compared to 24 ABPM SBP (the current “gold standard”).

2. Central SBP and radial P2 will predict LV mass independent of 24 ABPM SBP

Study DesignInclusion Criteria

•No CAD, Renal Disease or treated hypertension•Negative Exercise Stress Echo•Age <70

Resting Measurements•24ABPM•2D Echocardiography•Brachial BP•Central BP

Light Exercisen = 40

•Light – Moderate Exercise•Brachial BP•Central BP

Healthy Individualsn = 40

Methods – light exercise central BP andradial P2

Sharman J. Hypertension (2006); 47(6): 1203-8 Holland D. Am J Hypertens. (2008); 21: 1100-6

Colin device

Sphygmocor v8.0 Sydney, Australia

Methods - LV mass

• M-Mode linear measurement

– Wall thickness (septal/posterior wall)

– Left ventricular internal dimension

Lang R. Eur J Echocardiography (2006); 7: 79-108

Baseline characteristics (n=40)

Age (years) 57± 7

Male (%) 44

BMI (kg/m2) 28 ± 4

Brachial clinic SBP (mmHg) 126 ± 12

Brachial clinic DBP (mmHg) 74 ± 8

24 ABPM SBP (mmHg) 133 ± 11

Light exercise brachial SBP (mmHg) 187 ± 19

Light exercise central SBP (mmHg) 154 ± 15

Light exercise radial P2 (mmHg) 152 ± 17

Light exercise heart rate reserve (%) 49 ± 2

LV mass (g/m2.7) 37 ± 8

Aim 1: Determine the association between light exercise central SBP and radial P2 with LV mass

r pLight exercise radial P2 0.60 <0.001

Light exercise central SBP 0.55 <0.001

Light exercise brachial SBP 0.46 <0.01

24ABPM SBP 0.35 0.04

Rest brachial SBP 0.31 0.06

Correlates of LV Mass

Aim 2: Compare the strength of the associations between light exercise central SBP and 24 ABPM SBP with LV mass

r = 0.35p = 0.04

Z = 1.91; p=0.065

r = 0.60p < 0.001

Aim 2: Compare the strength of the associations between light exercise central SBP and 24 ABPM SBP with LV mass

Age

Gender

BMI

24ABPM SBP

Light exercise radial P2

Rest PSBP

Rest CSBP

Light Exercise Radial P2

β = 0.60, p <0.001

Model R2 = 0.41 p<0.001

Variable Normal LVMI (n= 31)

Above normal LVMI (n=5)

p

Exercise radial P2 149.2 ± 15.7 169.2 ± 15.7 0.04

Exercise brachial SBP 184.9 ± 19.3 197.0 ± 17.3 0.21

Rest central SBP 116.3 ± 10.7 124.3 ± 11.9 0.22

Rest brachial SBP 126.2 ± 11.8 134.0 ± 12.6 0.27

24 ABPM SBP 132.5 ± 10.7 138.2 ± 11.3 0.34

Above normal LVMI – Males > 48.0 g/m2.7; Females > 44.0 g/m2.7

202 mmHg

164 mmHg

184 mmHg

206 mmHg

Case 28.63 g/m2.7

30 50.18

32 28.63

Conclusions

1. Light exercise radial P2 is an independent predictor of LV mass.

2. A single clinic measure of light exercise radial tonometry may be a more accurate test to determine BP control.

Acknowledgments

Many thanks to:

Cardiovascular Imaging Research Group

Multiple Linear Regression Model with Exercise PSBP and no radial Exercise P2

Age

Gender

BMI

24ABPM SBP

Light exercise PSBP

Rest PSBP

Rest CSBP

BMI, Rest CSBP

β = 0.34, p= 0.193

Model R2 = 0.26 p=0.003

Sharman J. J Hypertension. 2007;25 (6):1249-54.