Cardiovascular technology and indication service

Series: Hypertension Management in Medical Practice

Today’s topic:

Blood pressure & pulse wave measurement combined in one procedureRe-classification of patients risks

„Blood pressurePWA measurement with the cuff is more efficient than other methods in routine practice. Specific therapy makes the measurement promising in terms of healthcare economics.”

Initial therapy can be individualized via risk classification and know-ledge of haemodynamics. In uncomplicated hypertension without increased arterial stiffness, inexpensive medications can also be utilised without specific effect on the vessel wall, although naturally this would basically be advantageous. Consider replacing this by sim-ply “This can lead to advantageous use of less expensive medications“

The offer of blood pressurePWA measurement in the medical practice leads to higher diagnostic accuracy and more specific therapy. The monitoring of therapy via PWA may enhance the physician/patient relationship, treatment adherence, and patient follow-up.

As of February 2013, CMS has provided reimbursement code 0311T which is an experimental code for the measurement of central blood pressure and associate parameters. We believe it carries a reimbur-sement rate of about $26–$29 depending on the location of the clinic. It has been shown that people in Germany are most willing to pay out of their pocket. A more targeted and effective treatment is achieved through the measurement of „vascular age”.

How can blood pressurePWA measurements reduce healthcare costs?

How is Blood PressurePWA measurement reimbursed?

Rev. 1.0 ENG © I.E.M. GmbH, www.iem.de

„Increased central blood pressure is an expression of increasing arterial stiffness and better represents the cardiovascular morbidity and mortality than the blood pressure value on the upper arm1“

© I.E.M. GmbH, www.iem.de

Paradigm shift in blood pressure evaluation – insight into arterial stiffness

Arterial stiffness is an independent and distinct “biomarker” of vascular health that is prognostic for cardiovascular risk.The fundamental physical characteristics of pulse waves in the cardiovascular system resemble those of acoustic waves. The form and velocity of the pulse wave depend on the stiffness of the arteries. Starting from the heart, the arterial tree tapers off into the periphery (funnel effect), which leads to an increase in blood pressure amplitude from the lower central pressure to a higher peripheral pressure, an effect called “blood pressure amplification”. At young ages, when arteries are more flexible, blood pressure amplification is more pronounced. As people age, central blood pressure increases and pressure amplification decreases. This process is caused by increased arterial stiffness with aging.

Analysis of the pulse wave provides various parameters. In addition to aortic pulse wave velocity, it provides such para-meters as augmentation index, a measure of the contribution of the reflected wave to the amplitude of the central pulse pressure. These parametery provide predictive values associated with risk of heart attack and stroke. They therefore add additi-onal cardiovascular to risk stratification, beyond the traditional factors such as brachial blood pressure, age or cholesterol levels. Every contraction of the left ventricle generates a pulse wave. Stiffening of the arterial vessel wall leads to early wave reflection during systole, which in turn leads to an increase of central aortic systolic pressure. This increased central aortic systolic blood pressure causes unfavourable increase in cardiac afterload. Because the wave reflection is early, during systole, rather than later, during diastole (as it is when the arteries are less stiff), there is reduction in diastolic blood flow into the coronaries and myocardial microcirculation. Recent research suggests that other organs such as the kidneys, eyes and brain can also suffer due to the increased central blood pressure associated with increased arterial stiffening.

fig. 2: Blood pressure 137/91 mmHg

fig. 2.1: Blood pressure 137/91 mmHgStructural differences of the vessel wall (sclerosing) can be indirectly assessed through the blood pressurePWA measurement.

fig. 1: Blood pressure is amplified from proximal to distal arteries among healthy persons.

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Literature and sources:1. Central Pressure More Strongly Relates to Vascular Disease and Outcome Than Does Brachial Pressure: The Strong Heart Study; Mary J. Roman et al.; Hypertension 2007;50;197-203;

2. Aortic Stiffness, Blood Pressure Progression, and Incident Hypertension; Bernhard M. Kaess, G. Mitchell et al.; JAMA. 2012;308(9):875-881

3. Differential Impact of Blood Pressure–Lowering Drugs on Central Aortic Pressure and Clinical Outcomes Principal Results of the Conduit Artery Function Evaluation (CAFE) Study; Bryan Williams et al; Circulation. 2006;113:1213-1225

4. Early vascular aging (EVA): consequences and prevention Vasc Health Risk Manag. Peter M Nilsson et al; 2008 June; 4(3): 547–552.

5. Oscillometric estimation of aortic pulse wave velocity:comparison with intra-aortic catheter measurements; Bernhard Hametner; Siegfried Wassertheurer, Johannes Kropf, Christopher Mayer, Bernd Eber and Thomas Weber; Blood Pressure Monitoring 2013

6. 2007 Guidelines for the Management of Arterial Hypertension The Task Force for the Management of Arterial Hypertension of the European Society of Hypertension (ESH) and of the European Society of Cardiology (ESC); Giuseppe Mancia et al.; Journal of Hypertension 2007, 25:1105–1187

7. Deutsche Mededizinische Wochenschrift 2010; 135:4–14, J. Baulmann et al., Arterielle Gefäßsteifigkeit

8. Value of Noninvasive Hemodynamics to Achieve Blood Pressure Control in Hypertensive Subjects; Ronald D. Smith et al.; Hypertension 2006;47:771-777

9. Normal Vascular Aging: Differential Effects on Wave Reflection and Aortic Pulse Wave Velocity, Carmel M. McEniery et al; Journal of the American College of Cardiology 2005, Vol. 46, No. 9

Imprint:Printing and publisher: I.E.M. GmbH, D – 52222 StolbergIn cooperation with the Society of Arterial Stiffness Germany-Austria-Switzerland www.degag.eu

„Die Arzthelferin bereitet das Anlegen und das Auslesen vor. Der Arzt entscheidet, was er gerne sehen möchte. Oftmals reicht ein Blick um die Unterschiede zu erken-nen. Dabei werden die Grenzwerte für Jung und Alt automatisch hinterlegt.“

„Blood pressurePWA measurement supports a therapeutic decision making according to risk class and haemodynamic characteristics of antihypertensive agents.“

„Population-based study shows that central blood pressure is more important than peripheral pressure in predicting CV outcomes (Roman et al1).“

A current evaluation of the Framingham Heart Study2 (Kaes et al.) illustrates a relationship between blood pressure and aortic stiff-ness over a period of 7 years among 1,759 participants. Increased arterial stiffness was significantly associated with the subsequent incidence of hypertension In the CAFE Study3, antihypertensive treatment based on two different medications were analysed on the basis of central blood pressure compared to peripheral blood pressure with regard to mortality and morbidity. Blood pressure among 2,199 participants was measured on the arm and centrally, calculated by means of a generalised transfer function from the peripheral pulse waveform. Patients were randomized to either amlodipine or atenolol as baseline treatment. After a 5½ year follow-up, amlodipine treatment resulted in similar peripheral (brachial) blood pressure to atenolol treatment but resulted in a significantly lower central blood pressure and this translated to a more favourable effect on cardiovascular morbidity and mortality. This suggests that the effect of different drug therapies on central blood pressure was more predictive of outcome and vascular changes than their effect on brachial blood pressure. The biophysical basis of cardiovascular diseases in connection with individual vascular age has been analysed in a study by Nilson et al Study4. Among young people, the elastic fibres (elastin) of the vessels which are responsible for the elasticity of vessels expand by 10% with every heartbeat. Material fatigue arises due to this mechanical stress (approx. 300 million expansions in 10 years). Because elastin is reproduced extremely slowly, less flexible collagen fibers replace it, with ultimate medial sclerosis and calcificatio. The arteries become stiffer. However, vascular age increases not only with biological age but also due to genetic influence, lifestyle (physical inactivity, smoking, poor diet, etc.) or disease (diabetes, hypertension, chronic kidney disease, rheumatoid arthritis, etc). This increased arterial stiffening at a young age is termed “early vascular aging” – EVA syndrome.

Clinical background – scientific evidence. What is the clinical and prognostic significance of arterial stiffness?

„Pulse wave velocity (PWV) measures arterial stiffness (in m/s.) Aortic PWV improves risk classification.“

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The risk of cardiovascular events, particularly in people with medium risk, can be reclassified with the PWA measurement. A better therapeutic decision can be made on this basis and patient management can be optimised.

• Screening – detection of subclinical end-organ damage • Initiation of a specific therapy • Objective data for better patient motivation in an understandable metric – Vascular Age

Blood pressure measurement with pulse wave analysis (Blood PressurePWA) is offered to patients as a “vascular age measurement”. The measure-ment can be utilised within the framework of prevention programs (for example during check-ups) in order to recognize early vascular aging.

Non-invasive PWV and central aortic pressure are mostly measured using either tonometry or oscillometric systems. Measurement of both central blood pressure and pulse wave analysis (PWA) together, called blood pressurePWA measurement, is now possible and can be be tested and validated against the standard invasive catheter technology. Blood pressurePWA measurement provides parameters of arterial stiffness together with peripheral resistance and stroke volume, thus offering simple and concise information that can aid in decisions about appropriate therapies.

Important criteria when selecting a measurement system:The efficiency of Blood Pressure Pulse Wave measurement

Why is blood pressure pulse wave analysis so valuable?

Arterial stiffness is quantified via the aortic pulse wave velocity (PWV) (measured in meters/second). The stiffer the aorta, the higher the PWV. The prognostic significance of aortic PWV is very well documented.Central aortic pressures (central systolic pressure, central pulse pressure) are more accurate measurements of the actual haemody-namic burden on the heart and arteries. Increasing arterial stiffness inevitably leads to an increase of central pressure values.PWV and central systolic pressure are measured non-invasively either tonometrically or with oscillometric systems. The measu-rement of blood pressure and pulse wave analysis (PWA) by a single device is now possible – Blood pressurePWA measurement. The measurement accuracy compared with the standard invasive catheter technology has been validated and published. Additional information about peripheral resistance and cardiac stroke volume can also be obtained in order to provide additional information for therapeutic decisions.

Simple measurement method – the most important aspects in short form

The early diagnosis of subclinical (clinically still silent!) organ damage is of crucial importance in determining cardiovascular risk. Measuring pulse wave velocity is a simple method for assessing damage to the vascular system and it is included in the European recommendations for classification and treatment of hypertension. If subclinical end-organ damage is demonstrated, patients in this high-risk group (class 3/4) should start comprehensive therapy immediately. Furthermore, this treatment should be accurately monitored throughout treatment.

The added value in medical practice – risk classification in accordance with ESC/ESH recommendations6

Blood Pressure Groups

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Lowadded risk

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Moderateadded risk

Highadded risk

Very highadded risk

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Moderateadded risk

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Normal Grade 2

Moderateadded risk

Elastic

Stiff

fig. 4: Windkessel model

fig. 6: “Vascular age” practice marketing

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What does the term “vascular age” mean?

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fig. 3: Age-dependent progression of pulse wave velocity (PWV) among 998 normotensive7 healthy subjects.

fig. 5: Classification of risk classesBlood pressurePWA measurement reclassifies the risk

fig. 7: Oscillometric blood pressure measurementtogether with PWA measurement.