Central Artery Pressure Wave Analysis

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Central artery blood pressure (CAP) is the pressure in the aorta, the large artery that sends blood from the heart throughout the body.  Experts believe that central blood pressure is more accurate and useful than typical blood pressure taken in the upper arm (brachial pressure), because a CAP measurement better predicts the risk of heart disease, stroke, and damage to the heart, brain, and kidneys.  In addition to the blood pressure numbers, the waveform of each heartbeat/pulse (Pulse Wave Analysis or PWA) allows insight into not only the major blood vessels your but also the function of the heart.  Evaluating your CAP in addition to your arm blood pressure is important because:

1.  There can be significant and clinically important difference between central and upper arm pressures in a given individual.

2.  Central pressures cannot be reliably inferred from brachial/arm pressures.

3.  Medications may have different effects on arm blood pressure than on the central arterial pressure.

SphygmoCor® offers noninvasive assessment of the central arterial pressure waveform, including both pressures and indices of arterial stiffness—providing noninvasive measurement of pressure effecting the heart, brain, and kidneys.  SphygmoCor technology is featured in more than 1,600 peer-reviewed publications and all “Top 20 Hospitals” in the USA use SphygmoCor technology to measure central blood pressure.

The information in the Patient Clinical Report has 3 areas indicated below.

Average Aortic Pressure Pulse – A graphical representation on the right side of the report page that shows the derived average pressure on the aorta.  The shape of the aortic pressure pulse is determined by the heart ejecting blood from the left ventricle and flexibility of the arterial system.  The waveform shape changes with changes in arterial stiffness.

Aortic Parameters – A summary of the derived average central pressure waveform parameters in the center of the report:

• SP (Aortic Systolic pressure) is the highest pressure in the aorta.

• DP (Aortic Diastolic pressure) is the lowest pressure in the aorta.

• PP (Aortic Pulse Pressure) is the difference between the highest and lowest pressures in the aorta.  PP above 50 indicates stiffness of the arteries and increases your risk for a heart attack, stroke, and kidney damage.

• MAP (Mean Arterial Pressure) is the average pressure over a single beat.

• HR (Heart Rate) is the number of heart beats per minute.
   

Aortic Clinical Parameters – A bar graph representing the aortic clinical parameters in reference to a healthy population range based on age and gender.  Reported on the left side of the report:

• SP: Aortic Systolic Pressure (mmHg) is the maximum aortic pressure during cardiac ejection.  A high aortic SP indicates high cardiovascular load.  High arterial stiffness increases the reflected pressure wave in the arterial system, which augments or increases Aortic Systolic Pressure.

• PP: Aortic Pulse Pressure (mmHg) is the height of the aortic pressure pulse.  PP can also be described as the difference between the maximum and minimum of the aortic pressure pulse, or the Aortic Systolic pressure minus the Aortic Diastolic pressure.  High aortic PP has been shown to predict cardiovascular events.

• AP: Aortic Augmented Pressure (mmHg) is the difference between the two aortic pressure peaks during ejection (systole). AP is a measure of wave reflected back from lower body. The value of AP is affected by both the magnitude and speed of the reflected wave, which is an indicator of arterial stiffness.  With aging, the arteries become stiffer, consequently, wave reflection increases, leading to increased Aortic Augmented Pressure and resulting in increased risk of cardiovascular disease or organ damage.

• AIx: Augmentation Index (%) is the ratio of AP to PP.  AIx has been shown to correlate with the extent of coronary artery disease, LV heart muscle hypertrophy, urinary albumin excretion, diabetic retinopathy, maximal aortic intima-media thickness, cardiovascular events, and all-cause mortality.

AIx 75: is normalized for a heart rate of 75 beats per minute.  AIx75 enables comparison of reports from patients with different heart rates and enables comparison of arterial stiffness between visits of the same patient.

A more detailed PulseWave Analysis report is provided to the doctor and includes additional information about the health of the heart muscle:

• Cardiac Ejection Duration (LVET):  this measures the time during which the left ventricle actively ejects blood through the aortic valve into circulation.  The cardiac ED can estimate cardiovascular disease risk and the progression of heart failure.  It is inversely related to heart rate and as such must be sex and heart rate adjusted (Male LVETI=1.7xHR+ED; Female LVETI-1.6xHR+ED).  Low LVETI correlates with reduced systolic LV function (possibly due to ischemia, CHF or prior heart attack) and extent of coronary artery disease but a prolonged LVETI is related to age, hypertension, diastolic dysfunction, and arterial stiffness.  Thus, both short and long LVETI are associated with poor health outcomes.

• Buckberg SEVR:  is an estimation of the myocardial blood supply‐demand ratio.  Research shows that the subendocardium is extremely susceptible to an increase myocardial oxygen demand and/or restrict blood supply.  Metabolic disease, excessive weight, aging, low red blood cell counts, hypertension, arterial stiffness, etc. are associated with lower and decreasing SEVR values, which are associated with increased cardiovascular risk.

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