Evaluation of main arteries rigidity indices according to the bifunctional 24-hour BP and ECG monitoring data with the use of BPLab device

N.M. Moiseeva, Y.A. Ponomarev, M.V.Sergeeva, A.N. Rogoza
A.L. Myasnikov
Institute of Clinical Cardiology of Research and Production Center of Russian Federation Health Ministry

Resume
Presented are the results of research of one of the main arteries rigidity index – pulse transit time (PTT) acquired during 24-hour monitoring, data obtained by the portable recorder BPLab. The work shows correlation of PTT index and BP in 24-hour dynamics. It demonstrates stable correlation of PTT value with other arteries rigidity indices taken by stationary equipment (VS-1000, Fukuda).
Portable ambulatory arterial blood pressure monitor (trademark: “BPLab”) manufactured by OOO “Petr Telegin” measures by oscillometric BP and registers all the data required for PTT measurement, precisely – oscillometric curve records (sphygmograms)  and echocardiogram signal with discretization 10 ms. Registered signals can be automatically processed for current PPT value determination, averaged during BP measurement (usually from 10 to 50 cardiac cycles), and for study of the present value correlation with systolic, diastolic and pressure blood pressure values. The presented results of research were acquired on basis of BP and ECG measurements by BPLab device.

Groups of patients and methods.
27 patients with arterial hypertension I-II degree (17 male, 10 female) from 45 to 73 years were inspected. They were treated as resident patients in arterial hypertension department at a hospital and they received antihypertensive therapy.
PTT rate was measured with the use of series-produced device for bifunctional monitoring of 24-hour BP and ECG (BPLab Standard) in the current research. The device enables obtaining PTT value for every measurement cycle. Time interval from maximum R-wave till beginning of pulse wave registered in shoulder cuff is measured for this purpose.
PTT values of every cardiac cycle within one BP measurement were averaged for accuracy increase. The present procedure enables estimating of PTT values within the whole monitoring day and receiving daily profiles of BP and heart rate (as it was in earlier BPLab-software versions) and PTT as well in such a way. An alternative unit Vasera VS-1000 measuring pulse wave speed in aorta and main arteries of right (R-PWV) and left limbs (L-PWV) was used for comparison.

Results
Daily BP and ECG-monitoring with PTT measurement was successful among all patients.
Every patient daily PTT was averaged for correlation with data acquired by Vasera VS-1000. Interrelation between PTT and main arteries stiffness index R-PWV was analyzed by linear regression analysis. A reliable correlation of PTT-index measured by BP Lab device and R-PWV (R=0,45, p<0,05). 
Main arteries stiffness indices applied in the present time are closely interrelated with pulse BP. An interrelation degree between average daily PTT and average daily BP was also defined by regression analysis. Correlation coefficient was 0,51 (p<0,05).
It is well-known that arterial stiffness increases essentially at blood pressure rising. We observed this relationship among all patients while detecting interrelation between systolic and diastolic blood pressure with PTT-indices acquired by every BP measurement. Correlation coefficients varied from 0,5 till 0,9.

Discussion
The acquired data demonstrated an interrelation between PTT-index measured by BP Lab Standard device during daily blood pressure and ECG-monitoring and other indices of main arteries stiffness for patients with increased BP clearly. Besides the above-mentioned index showed a close interrelation between pulse pressure rising which is now considered to be an important factor of undesired dynamic pressory load on target-organs and systolic and diastolic blood pressure rising.