Stiff Aortic Wall May Lead to Hypertension

(MedPage Today) — Several measures of aortic wall stiffness, including carotid-femoral pulse wave velocity, forward wave amplitude, and augmentation index, were found to correlate with a higher odds of incident hypertension after a 7-year follow-up, reported Gary Mitchell, MD, of Cardiovascular Engineering in Norwood, Mass., and colleagues.

However, higher baseline blood pressure did not correlate with aortic stiffness, which suggests that “arterial stiffness precedes the development of hypertension rather than vice versa,” according to the study published in the Sept. 4 edition of the Journal of the American Medical Association.

Researchers also found that a higher resting brachial artery flow and a lower flow-mediated dilation at baseline were associated with a higher odds of developing hypertension.

“Given the health hazards associated with hypertension, identifying a precursor has significant clinical implications,” wrote Debabrata Mukherjee, MD, MS, of the Texas Tech University Health Sciences Center in El Paso, in an accompanying editorial.

“Stiffening of the aortic wall and improper matching between aortic diameter and flow are associated with unfavorable alterations in pulsatile hemodynamics, including an increase in forward arterial pressure wave amplitude, which increases pulse pressure,” Mitchell and colleagues wrote.

“The resulting increase in pulsatile hemodynamic load increases cardiac afterload, reduces diastolic coronary flow, and damages microcirculation, particularly in high-flow organs such as the kidneys and brain,” they added.

Vascular stiffening occurs with age, but it also occurs with other cardiovascular risk factors such as hypertension, obesity, diabetes, and dyslipidemia.

Although the association between the loss of vascular flexibility and blood pressure has been known, there are not much data on their temporal relationship, “in particular, whether vascular stiffness antedates hypertension or vice versa,” researchers said.

To answer this question, they analyzed data from the longitudinal Framingham Offspring cohort from two time points: baseline 1998-2001 and follow-up 2005-2008.

The baseline period was the first one to include arterial tonometry measurements, which the authors described as:

  • Carotid-femoral pulse wave velocity is the criterion standard for assessing aortic stiffness and depends on aortic wall stiffness and lumen diameter.
  • Forward wave amplitude depends on peak systolic blood flow and the resistance of the aorta to blood flow, and also is related to aortic wall stiffness and lumen diameter.
  • Augmentation index, a measure of peripheral wave reflection, is the proportion of the central pulse pressure that is attributable to a late systolic increase in pressure due to overlap between the forward and reflected pressure wave.
  • Flow-mediated dilation is the percentage change in brachial diameter between baseline and hyperemia.

There was a total of 1,759 participants, with a mean age of 60, and 974 were women. There were 338 incident cases of hypertension, which is an adequately powered sample, Mukherjee commented.

Overall, in multivariable analyses, researchers found that aortic stiffness and pulsatile hemodynamic differences correlated with increased blood pressure and incident hypertension.

Results showed that a higher baseline carotid-femoral pulse wave velocity (β 1.5 mm Hg per 1 SD, 95% CI 0.5 to 2.6, P=0.006) and forward wave amplitude (β 1.3 mm Hg per 1 SD, 95% CI 0.5 to 2.1, P=0.002) were associated jointly with higher systolic blood pressure at follow-up.

Conversely, lower systolic blood pressure and carotid-femoral pulse wave velocity at baseline were associated with a higher diastolic blood pressure at follow-up.

When all three measures of aortic stiffness were higher at baseline, along with a lower mean arterial pressure, participants tended to have a higher pulse pressure at follow-up.

Mitchell and colleagues also found in a single multivariable model that incident hypertension at follow-up was associated with systolic and diastolic blood pressure, carotid-femoral pulse wave velocity, augmentation index, and forward wave amplitude.

However, blood pressure at baseline was not predictive of the risk of hypertension.


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