![Blood pressure measurement and CV Risk ,[object Object],[object Object],1 Vasan R. N Engl J Med. (2001); 345:1291-97 2 Lewington S. Lancet (2002); 260: 1903-13 3 Simone G. JACC 1995. 25(5): 1056-62 4 Mancia G. Circulation. 1997;95(6):1464-70.](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
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Exercise Haemodynamics
- 1. 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.
- 8. Methods – light exercise central BP and radial 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
- 10. Baseline characteristics (n=40) Age (years) 57± 7 Male (%) 44 BMI (kg/m 2 ) 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/m 2.7 ) 37 ± 8
- 11. Aim 1 : Determine the association between light exercise central SBP and radial P2 with LV mass Correlates of LV Mass r p Light 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
- 12. Aim 2: Compare the strength of the associations between light exercise central SBP and 24 ABPM SBP with LV mass r = 0.35 p = 0.04 Z = 1.91; p=0.065 r = 0.60 p < 0.001
- 13. Aim 2: Compare the strength of the associations between light exercise central SBP and 24 ABPM SBP with LV mass Model R 2 = 0.41 p<0.001 Age Gender BMI 24ABPM SBP Light exercise radial P2 Rest PSBP Rest CSBP Light Exercise Radial P2 β = 0.60, p <0.001
- 14. Above normal LVMI – Males > 48.0 g/m 2.7 ; Females > 44.0 g/m 2.7 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
- 15. 202 mmHg 164 mmHg 184 mmHg 206 mmHg Case 28.63 g/m 2.7 30 50.18 32 28.63
- 17. Acknowledgments Many thanks to: Cardiovascular Imaging Research Group
- 18. Multiple Linear Regression Model with Exercise PSBP and no radial Exercise P2 Model R 2 = 0.26 p=0.003 Age Gender BMI 24ABPM SBP Light exercise PSBP Rest PSBP Rest CSBP BMI, Rest CSBP β = 0.34, p= 0.193
- 19. Sharman J. J Hypertension. 2007;25 (6):1249-54 .
Editor's Notes
- Hypertension is a leading risk factor for cardiovascular disease and mortality. This can be related to end organ damage such as increases in left ventricular mass. The gold standard for assessing blood pressure control is 24 ambulatory blood pressure monitoring, as this is the strongest blood pressure measurement correlate for LV mass. This is logical as blood pressure is assessed during activities of daily living, and is a measure of chronic blood pressure exposure.
- Central blood pressure or the pressure at the ascending aorta estimated by applanation tonometry has been shown to predict cardiovascular disease and death independent of resting brachial blood pressure. Differences between brachial and estimated central blood pressure can be 30mmHg or more between individuals – thus central blood pressure may account for more individual differences and thus greater predictive value for CVD and mortality. Differences in estimated central systolic and brachial can be 30 mmhg or more. Earlier this year Munir has shown that P2 on the radial waveform is closely correlated to central systolic blood pressure and this may negate the need to use the generalized transfer function. Whilst ambulatory blood pressure measures are obviously important large differences can occur activities of daily life.
- So, given that brachial blood pressure monitoring during activities of daily living is the gold standard for assessment of blood pressure control, large differences between central and upper arm sbp occur dyring light exercise similar to daily life. This raises the possibility that light exercise central bp may provide a more accurate estimation of BP control compared with the current gold standard of 24 hour ambulatory blood pressure monitoring.
- Therefore, this study aimed to firstly determine the association between lv mass, estimated central systolic blood pressure and radial p2 as a measure analogous to cbp during light exercise – which is similar to activities of daily living. And our secondary aim was To compare the strength of these associations between light exercise central SBP and 24 ABPM SBP with LV mass
- We hypothesized that Central SBP and radial P2 during light exercise will be stronger correlates of LV mass compared to 24 ABPM SBP (the current “gold standard”). And that Central SBP and radial P2 will predict LV mass independent of 24 ABPM SBP
- We recruited 40 healthy individuals under the age of 70 who had no history of CAD renal disease, were not treated for hypertension, and have had a negative exercise stress echo. [click mouse or spacebar] 24 hour ambulatory blood pressure monitoring, 2d echocardiography, brachial and central blood pressure estimated using radial applanation tonometry and estimated using generalized transfer function using commercial equipment. [click mouse or spacebar] Subjects then performed light-moderate exercise whilst measures of their brachial and central blood pressure were obtained
- Light exercise blood pressure WAS assessed whilst the patients WERE riding at 50rpm on an exercise bike resistance on the bike was adjusted so the subject achieved 50% of age predicted heart rate reserve. [press spacebar] Brachial blood pressure was obtained using brachial cuff mercury sphygmomanometry and [press spacebar] radial tonometry was performed with aid of a servo-controlled unit. OUR GROUP HAS SHOWN This process to be valid and to have good reproducibility during exercise, with this whole process taking approximately 15 minutes.
- LV mass was measured according to amercian society of echo guidelines utilising m mode echocardiographic assessment of left ventricular wall thickness.
- Mean age of this population was 57 years, 44% were male, and generally overweight. Resting brachial clinic SBP was normal. As a measure of exercise intensity these patients were exposed to a heart rate reserve of around 50% - which is equivalent to light to moderate exercise as stipulated by the american college of sports medicine. LV mass was normal on average in this population.
- Inorder to determine the association between light exercise central sbp and radial p2 with lv mass we performed pearson bivariate correlations for lv mass. Here is the strongest correlates in descending order of significance. In this population a correlation of 0.35 for 24 abpm was obtained which is similar to previously published research. However, note that light exercise radial p2 and central systolic blood pressure were more strongly correlated to LV mass than 24 hour monitoring.
- Here are graphical representations of 24ABPM SBP on the left 24 abpm and radial p2 on the right. In order to test our second hypothesis we needed to determine if there was significant difference between these correlations a z statistic was performed. The difference was of only borderline significance with p of 0.065
- To test our second hypothesis we then wanted to look at the best independent predictors of lv mass. We entered Known significant predictors of lv mass, and the significant correlates for lv mass from our data into a backward stepwise multiple linear regression model. Exercise peripheral systolic blood pressure was not included due to collinearity with exercise radial p2. In this model the only independent predictor of lv mass was light exercise p2. with a beta 0.60 and a highly significant p value of <0.001. This model explained 41% of the variance in LV mass and was statistically significant at less than 0.001. When we replace exericse peripheral systolic blood pressure the model was weakened.
- Lang reference. The group was divided into 2 groups, based on lv mass. Those with raised lv mass have a significantly higher exercise radial p2 However, there is no significant difference in other measures including 24 abpm sbp.
- Radial p2 during light exercise as a measure of central systolic blood pressure may be a more accurate predictor of lv mass and may be explained by this graph. All brachial light intensity exercise blood pressures have been stratified from smallest to highest, and plotted in purple, the corresponding radial p2 measures are plotted in green. The brachial blood pressure is the same type of reading which is taken by the 24 hour monitor – this does not represent the central pressure that the heart is exposed to whilst these patients go about their activities of daily living. Note that there is a greater amount of variation in the p2 measure, this variation may account for the improved accuracy of the radial p2 measure. [Press spacebar] Take case 30 and 32. both women have similar brachial exercise bps at 202 and 206 respectively, but their radial p2 measures differ by 19mmHg. In keeping with other data presented the person with higher p2 has a higher lv mass.
- Light exercise radial P2 as an estimate of central sbp is an independent predictor LV mass Although more studies are required a single clinic measure of light exercise radial tonometry may be a more efficient, convenient and accurate test to determine blood pressure control
- I would like to thank and acknowledge my fellow contributors on this article as well a number of organisation who have helped me by funding travel – which have enabled me to speak here today. High blood pressure research council of Australia for the funding for travel they have provided. Solvay pharmaceuticals who have provided me with an unrestricted travel grant. And the on going funding and support which Prof. Marwich and his research group has provided me. Thank-you.
- To test our second hypothesis we then wanted to look at the best independent predictors of lv mass. We entered Known significant predictors of lv mass, and the significant correlates for lv mass from our data into a backward stepwise multiple linear regression model. In this model the only independent predictor of lv mass was light exercise p2. with a beta 0.60 and a highly significant p value of <0.001. This model explained 41% of the variance in LV mass and was statistically significant at less than 0.001
- This is important because when looking at 2 males of the same age during light exercise. [Press spacebar] whilst their brachial blood pressure – taken at the upper arm, is the same [press spacebar] their pressures centrally are significantly different. This second person’s central blood pressure is elevated during conditions similar to activities of daily living. Our second individual’s heart is pumping against 25mmHg more pressure than person 1, and this may have a significant impact upon the size of their heart. Our group has previously shown that there is significant individual variation in central systolic bp response to light intensity exercise which is not apparent at rest.