Tom Archer, MD, MBA UCSD Anesthesiology May 9, 2011

Radial pulse analysis, central blood pressure and cardiovascular health:

an historical curiosity makes a comeback.

Tom Archer, MD, MBA

UCSD Anesthesiology

May 9, 2011

http://www.itmonline.org/image/pulse2.jpg

Pulse analysis was practiced in Chinese medicine thousands of years ago.

Pulse analysis was also serious business in the 19th century

in Europe and the USA

• Sphygmographs in common use.

• Insurance companies relied on their results.

http://www.mamweb.org/modules.php?name=Content&pa=showpage&pid=32000

Etienne-Jules Marey (1830-1904) invented the sphygmograph to record the arterial pulse on smoked paper. It was used by Engelmann, Mackenzie and Wenckebach.

Sphygmograph 1876

Life insurance examination manual from 1891 discussed pulse analysis by sphygmography.

Tom Archer, 58 y.o., good general health. Takes Crestor for high cholesterol.

Radial and predicted ascending aortic pressure waveform when subject is cold.

Scipione Riva-Rocci introduced the mercury sphygmo-manometer in 1896.

Measured systolic BP only.

history.library.ucsf.edu/.../chapter2_03.html

Harvey Cushing used it.

Korotkoff introduced auscultation for diastolic pressure in 1905.

In the 20th century, Riva-Rocci and Korotkoff’s sphygmomanometer

eclipsed pulse analysis

• Two simple numbers: systolic / diastolic.

• Easy to use.

• Pulse analysis fell into disuse.

• 20th century saw tremendous gains from simple sphygmomanometry: dangers of high BP.

But simple sphygmomanometry ignores valuable information within

the pulse trace.• Extra information can be extracted from the pulse

using high fidelity transducers, computers and a “generalized transfer function”, which has been validated.

• Specifically, the Central Blood Pressure (CBP) can be calculated using the radial pulse contour and the non-invasive brachial blood pressure.

• CBP is the pressure in the ascending aorta.

health.yahoo.com/topic/heart/overview/article...

LV “sees” the SBP in the ascending aorta.

With normal aortic valve, LV wall tension depends on pressure in ascending aorta

(and diameter of LV chamber).

SphygmoCor system for measuring central blood pressures

Central blood pressure (CBP)

• Diastolic and mean pressures are very similar at radial / brachial and central sites, but

• Systolic CBP is not the same as brachial or radial systolic BP!

AIR

BLOOD

#3 Systemic vascular resistance (resistance arterioles)

#2 Stiffness of aorta (“windkessel”)

heart

veins

arteries

#1 SV

#4 Wave reflection–

timing and amount

Muscular arteries

Central BP

What creates central BP?

Kozo Hirata, MD; Masanobu Kawakami, MD; Michael F O’Rourke, MD, DSc*Circ J 2006; 70: 1231–1239

Augmentation Index (AIx) =

Augmentation Pressure /

Pulse Pressure

If reflected wave travels fast and arrives during systole it creates “augmentation pressure”, extra pressure work for the heart during systole.

A high augmentation index is a deadly backdraft of pressure which exhausts the heart over time.

Run animation

• Wave reflection animation can be found at:

• http://atcormedical.com/wave_reflection.html

Augmentation Index (AIx)

• High AIx = unnecessary heart work.

• High AIx leads to LVH and cardiomyopathy.

• Lower AIx is better.

• Treatments that lower AIx help the patient.

When is AIx high-- chronically?

• Normal aging

• Obesity

• Atherosclerosis

• Diabetes

• Pre-eclampsia

• Inflammatory arthritis

• Renal failure

WW Nichols Curr Opin Cardiol 2002, 17:543–551

As healthy individuals age, reflected wave arrives at ascending aorta earlier and increases augmentation index and central pulse pressure. Three members of same family.

Central BPs– ASCOT / CAFE study

• Lower central BPs are associated with better CV outcomes.

• Amlodipine achieved lower central BPs and had better CV outcomes than atenolol, despite achieving the same brachial artery BPs.

CAFE / ASCOT study, M. O’Rourke (Circulation. 2006;113:1213-1225.)

Four months Rx with lisinopril decreased central aortic pulse pressure and augmentation index.

WW Nichols Curr Opin Cardiol 2002, 17:543–551

6 months Rx with atorvastatin decreased central aortic pulse pressure and augmentation index.

WW Nichols Curr Opin Cardiol 2002, 17:543–551

Adams KF, Am J Health-Syst Pharm—Vol 61 May 1, 2004 Suppl 2

ACE inhibitors and aldosterone antagonists reverse LV hypertrophy– via central BP effects?.

ACE inhibitors, statins and aldosterone antagonists

can reverse LV hypertrophy—

is this due to decreased AIx and strain on the heart?

What makes AIx go down-- chronically?

• Exercise

• Weight loss

• Red wine

• Statins

• Control of blood pressure (ACEI and CCB)

• NTG

Ultra-marathon runner, 30 yo, at rest, seated. AIx = -14%. Note high diastolic radial and CBP.

When is AIx high– acutely?

• Arterial compression in legs (squatting)

• Cold body temperature.

• Nicotine ingestion

Tom Archer, 58 y.o., while squatting.

AIx = 21%

Tom Archer, seated, very cold from being outside in winter.

AIx = 27%

David G. Edwards,1 Amie L. Gauthier,2 Melissa A. Hayman,2 Jesse T. Lang,2 and Robert W. Kenefick2J Appl Physiol 100: 1210–1214, 2006.

Exposure of healthy young adults to cold air for 30 min increases augmentation index.

What makes AIx decrease-- acutely?

• Exercise

• Alcohol

• Lowering blood pressure

• NTG

Tom Archer, 58 yo, after work, seated comfortably. AIx = 11%.

Tom Archer, 58 yo, after exercise and wine.

AIx = 1%

Perioperative hypothermia increases cardiac event rate.

Is this due to increased AIx with hypothermia?

Could AIx guide therapies in anesthesia and intensive care?

• NTG in low doses may work by decreasing wave reflection, CBP and afterload.

• First trial of AIx guided treatment would seem to be afterload reduction for the depressed LV– as in coming off CPB.

• SphygmoCor Mx does analysis on arterial line tracing, so it is continuous and hands-free.

Is this an area which deserves more attention in Critical Care

Medicine?

The End