30 Jun '09

Cardio Pulse Wave :: What does it test?

by synergy

Cardio Pulse Wave (CPW) uses the BPro device and A-PULSE software. This is the state-of-the-art equipment, technology and software. Now learn what the measurements mean. This is somewhat technical so bear with me.

A-PULSE CASP is a revolutionary product patented by HealthSTATS International Pte Ltd. It is able to measure accurately the Central Aortic Systolic Pressure or CASP, which is the blood pressure at the root of the aorta. It is the only device which can be used in common clinical setting. CASP has been shown in many recent studies as an important determinant for strokes and CVS events. It has been validated via invasive study and achieved an accuracy (co-relation) R= 0.9917 independently. A-PULSE CASP is FDA and CE MDD approved. It is also being used in large drug trials by Pharmaceutical companies.

A-PULSE CASP® is designed to measure the CASP in a simple clinic or Pharmacy setting. The BPro device is used, together with a computer or laptop, using a USB port. It gives real time recording of the arterial waveforms which can be replay at any later time for further study. Another strong feature of A-Pulse is the ability to compare the various waveforms on different dates of the same patient, or different patients. All the parameters including the CASP are displayed instantaneously, the waveforms superimposed for comparison. The A-PULSE CASP® is the only device that can measure the CASP in a clinic setting, easy to use and accurate. It is the evidence-based approach to the management of hypertension.

What is arterial pulse waveform?

idealPulseWave

Diagrammatic Representation of a Radial Arterial Pulse Wave

When the left ventricle ejects blood into the aorta in systole, the perturbation generates a wave that initially travels through the arteries from the heart towards the arterial tree.

Pulse waveform has 2 components.
1. Forward traveling wave when the left ventricle contracts and
2. Reflected wave returning back from the peripheral.

What is CASP (Central Aortic Systolic Pressure)?

CASP (Central Aortic Systolic Pressure)

CASP (Central Aortic Systolic Pressure)

This is the blood pressure at the root of the aorta or the largest artery in the body, as the blood is being pumped out of the heart. This pressure is called Central Aortic Systolic Pressure or CASP. CASP has been shown to be an important factor in the relation to strokes and cardiovascular events, more so than the brachial pressure, or the pressure at the arm commonly.

CASP is different and usually lower than the brachial pressure in normal people. When we are young, below 40 years old, the difference between CASP and the brachial pressure can be significant (up to 30 mmHg). However, as we age, the aorta gets stiffer and the compliance reduces. As a result, the CASP increases and comes much closer to the brachial pressure. In patients with high blood pressure, the CASP can be abnormally high for his age, showing “pre-mature stiffening of the aorta.

It has also been shown that certain class of drugs used in the treatment of high blood pressure can also have an adverse effect on the CASP, increasing it instead of reducing, as shown in the CAFÉ study. Therefore it is important to show that the treatment a patient is taking actually result in lowering the CASP and not the reverse. By reducing the CASP of the patient, we are reducing the risks of stroke and heart events.

How to measure CASP? The Invasive Method

Catheter Method of Measuring the Cardio Pulse

Fig 1. Catheter Method of Measuring the Cardio Pulse - Invasive Method

This is direct measurement and has been considered as the most accurate method. To perform the measurement, a catheter must be inserted into the aortic root from bronchial or femoral artery, which is obviously an invasive method and could result in complications (Fig.1). This invasive method of measuring CASP is not available in clinical setting. However, A-PULSE CASP can be used in clinic and the accuracy
has been validated against this invasive method, the result is R=0.9917 (co-relation). (What this means, for those of you who are like me and don’t quite get the point, is the CPW is 99.17% as accurate as the catheter method!)

How to measure CASP? The Non-Invasive Method

Fig 2. CASP with A-PULSE CASP Software :: Non-Invasive Method

Fig 2. CASP with Computer

HealthSTATS (HS) invented a device named BPro which is able to capture radial pressure waveforms. Furthermore, HS developed a proprietary formula to derive central aortic systolic pressure (CASP) from the calibrated radial pressure waveform (Fig. 2).

Fig. 2 Non-invasive measurement of CASP using the Cardio Pulse Wave (which is the combination of HealthSTATS BPro device and A-PULSE software)

Augmentation index is the difference between the second and first systolic peaks expressed as a percentage of the pulse pressure.

Arterial compliance is the ability of an artery to increase the volume in response to a given increase in blood pressure is called compliance.

Pulse wave velocity or PWV is the speed at which the pressure waveform travels (wave propagation) along the aorta and large arteries, during each cardiac cycle.

Applanation tonometry is the principle of applanation tonometry is that the force acting on the plunger is proportional to the pressure in the artery when where the artery surface is flattened.

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