INTRODUCTION AND AIMS: Carotid-femoral pulse wave velocity (cfPWV) is an established non-invasive standard to assess aortic stiffness (AS). It has been shown to be associated with increased cardiovascular mortality and morbidity independent of classic cardiovascular risk factors. However, cfPWV is strongly associated with blood pressure (BP) level. It is thus unknown whether particular measured cfPWV value reflects real vessel damage or current level of BP. Emerging non-invasive oscillometric devices use mathematic approaches and are able to deliver an estimated aortic PWV (eaPWV), which shows good correlation with cfPWV. Such devices allow easy and quick calculation of eaPWV, which can be repeated plenty of times under varying BP and patient position. The aim of the study was to establish an BP-independent eaPWV based on mathematical analysis of 24 hours ambulatory BP and pulse wave (PW) monitoring.
METHODS: 507 patients from our outpatient nephrology and hypertension unit were included. For every patient at least one 24 hours ambulatory BP and pulse wave monitoring was available. We used Mobil-O-Graph (I.E.M., Stolberg, Germany) to perform the recordings and data analysis was performed with HMS Client Software. Demographic parameters and available data from clinical recordings were also included in the analysis. The development of eaPWV in relation to central systolic BP (cSBP) was assessed using scatter plot. Based on this analysis new characteristics of the eaPWV were generated: PWVslope and PWVbaseline. Using multipe regression approach the impact of demographic and clinical parameters on eaPWV, PWVbaseline and PWVslope was analysed.
RESULTS: 48.7% of study collective was female. The mean age was 60.7 years and the mean body-mass index was 27.4 kg/m2. 92.5% have had established diagnosis of hypertension, 33.7% of hyperlipoproteinemia and 22.9% were smoker. 20.5% had diabetes mellitus and 29.6% eGFR <60 ml/min/1,73 qm. The mean brachial BP was 133/80 mmHg with the mean heart rate of 69.5 beats/min. The mean cSBP was 121.6±13.4 mmHg and the mean eaPWV was 9.2±2.2 m/s. The mean PWVslope was 0.035 and the mean PWVbaseline was 4.9 m/s. eaPWV correlated with cSBP in a linear manner and can be expressed with following equation: eaPWV=PWVslope*cSBP+PWVbaseline. Increased age, history of myocardial infarction and SBP were associated with increasing in eaPWV, while decreased diastolic BP (DBP) and eGFR were associated with increasing in eaPWV. DBP and age were significantly associated with PWVbaseline. No significant impact of any demographic or clinical parameter was observed for PWVslope.
CONCLUSIONS: We observed the linear correlation between eaPWV and cSBP in every single recording in our study collective. As shown in previous studies higher age, impaired renal function, higher SBP and lower DBP were associated with higher eaPWV.Based on single 24 hours BP and PW monitoring we were able to calculate an individual PWVslope and PWVbaseline for every patient. Using these parameters a BP-adjusted eaPWV (e.a. for SBP 120 mmHg) can be determined. The later can discriminate BP-associated change in PWV from the real vessel damage. Also, it makes this non-invasive parameter for the assessment of AS comparable along different recordings in the same subject or in different patients.
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