What are the ideal systolic and diastolic blood pressure which do not injure the intima of iliac and coronary arteries?
Authors: Hsu W , Nguyen T , Le T , Pham T , Le T , Dang C , Nguyen B , Vu P , Cao T , Vu L , Talarico E 
Published: October 2022

Abstract

For patients with coronary artery disease, hypertension (HTN) is a major risk factor. How could uncontrolled HTN start atherosclerosis? In our prior research, laminar flow in coronary arteries prevented the formation of plaques while turbulent flow injured the intima and triggered atherosclerosis. In this present study our question was: Which blood pressure (BP) level is optimal in not producing turbulence and so not injuring the intima?

Methods
At first, a systolic BP&lt;120mmHg and diastolic BP&lt;75mmHg) were arbitrarily set as controlled (group A) while a BP of &gt;160/105mmHg as uncontrolled (group B). All patients underwent a dynamic coronary angiogram recorded at 15 images/second or 0.06 seconds per image. The first image was of the index artery completely filled with contrast. In subsequent images the blood in white color moved in over a background of black contrast (Figure 1A). In 1B, 0.06 seconds later, the blood arrived at the mid segment (white arrow). In 1C, the flood moved forward, however there was darker contrast hanging at the mid segment, marking the location of collision from the retrograde against the antegrade flow (white arrow). The reason was that in uncontrolled BP the contraction of the left ventricle was stronger so in systole, the coronary blood could reverse its course, run on a retrograde direction, collide against the antegrade flow and create turbulence (1C).
At the end, before deploying a vascular closure device, an iliac angiogram was performed. In Figure 2, on a black background of contrast, the blood in white color moved forward with a pointed tip of laminar flow. 0.06 seconds later, the laminar tip was stopped abruptly with all the layers recoiling on each other like a falling stack of dominoes. In the next image. a large swirl of disorganized mixing of blood and contrast suggested the presence of turbulence caused by the collision.
The data to be collected were (1) the duration of the antegrade and retrograde flow, (2) duration of the collision (turbulence at the collision site)

Results
In the group A (BP &lt;120/75 mmHg), 90% of 20 patients had no retrograde flow nor collision in the iliac and short collision in coronary arteries (&lt;0.12 secs). In 30 patients of group B (BP &gt;160/105 mmHg), the duration of retrograde flow and collision in the iliac artery were prolonged at &gt;0.24 msecs. In the coronary arteries, the duration was prolonged at 0.18 msecs (all p&lt;0.05 compared with group A). These locations of turbulence correlated with the location of plaques in our prior studies.

Conclusion
In patients with uncontrolled HTN, the retrograde flow was prolonged, and the turbulence was intense. In contrary, for patients with controlled BP, there was no retrograde flow and weaker collision in coronary arteries. The results suggest that a BP of &lt;120/75 mmHg may not trigger the atherosclerotic process. New clinical trials with larger number of patients should be performed in search for the lowest ideal blood pressure.

Funding Acknowledgement
Type of funding sources: None.