Measurement accuracy of non-invasively obtained central blood pressure by applanation tonometry: A systematic review and meta-analysis

Background and objectives

Non-invasive methods based on applanation tonometry have been proposed to estimate central blood pressure. However, the accuracy of these methods hasn't been systematically examined.

Methods

We performed a systematic review and meta-analysis of studies comparing estimated and invasively measured central BP.

Results

Sufficient data were available in 22 studies for meta-analysis (857 subjects and 1167 measurements). Acquired arterial pressure waveforms in these studies were directly measured, calibrated to match invasive aortic mean BP and diastolic BP or calibrated to match brachial BP measured with a sphygmomanometer, cuff BP. Of the former 2 conditions, the errors of estimated central BP were small with a mean and standard deviation of difference − 1.1 ± 4.1 mm Hg (95% limits of agreement − 9.1–6.9 mm Hg) for central systolic BP; − 0.5 ± 2.1 mm Hg (− 4.6–3.6 mm Hg) for central diastolic BP; and − 0.8 ± 5.1 mm Hg (− 10.8–9.2 mm Hg) for central pulse pressure. However, the errors inflated to − 8.2 ± 10.3 mm Hg (− 28.4–12.0 mm Hg) for central systolic BP, 7.6 ± 8.7 mm Hg (− 9.5–24.6 mm Hg) for central diastolic BP, and − 12.2 ± 10.4 mm Hg (− 32.5–8.1 mm Hg) for central pulse pressure, when calibrated to cuff BP. The findings were still evident in subgroup analysis conducted with different central BP estimating methods and validated cuff BP monitors.

Conclusion

Present tonometry-based central BP estimating methods are acceptable in theory, with small errors. However, based on current available evidence, there is substantial room for improvement in measurement accuracy of central BP when cuff BP is used to calibrate the peripheral waveforms.     

Patients with refractory angina have increased aortic wave reflection and wasted left ventricular pressure energy

BackgroundEarly return of reflected blood pressure (BP) waves from the lower body augments central systolic BP and increases systolic pressure-time index (SPTI) and wasted left ventricular (LV) pressure energy, which increase afterload and myocardial oxygen (MVO₂) demand. Accordingly, we sought to determine wave reflection characteristics and diastolic timing in a group of patients with chronic stable angina resistant to anti-anginal therapy.MethodsRadial artery BP waveforms were recorded non-invasively by applanation tonometry in 36 patients with refractory angina (RA) and a reference control (CON) group of 36 successfully treated hypertensive patients without angina matched for age, gender, height, BMI, and mean BP. Pulse wave analysis (PWA) of the ascending aortic BP waveform was used to determine central hemodynamics, diastolic timing, wave reflection characteristics and wasted LV pressure energy (LVEw).ResultsCompared to the CON group, RA patients had higher central aortic augmented BP, augmentation index (Alx) and reflected pressure wave systolic duration (SDR). These modifications in wave reflection characteristics were associated with an increase in SPTI and LVEw and a decrease in pulse BP amplification and the diastolic pressure time fraction.ConclusionsRA patients have changes in systolic wave reflections and diastolic timing that increase LV afterload, MVO₂ demand and wasted LV energy and reduce coronary artery perfusion. These alterations in cardiovascular function contribute to an undesirable mismatch in the MVO₂ supply/demand ratio that favors ischemia and angina pectoris and may precipitate future adverse cardiovascular events.     

Comparison of two techniques for measuring pulse wave velocity and central blood pressure

Pulse wave velocity (PWV) is an important parameter in the assessment of overall cardiovascular risk and there is well documented predictions of mortality in special groups of patients. Several methods are available for measuring the velocity and other parameters of the pulse wave. Our aim was to assess the comparability of two methods; applanation tonometry, which is used by the SphygmoCor device and oscillometry employed by the Arteriograph system. Published data on their comparability are contradictory. Thirty-three patients of both sexes were examined in the study. Mean PWV was significantly higher with Arteriograph than SphygmoCor (10.2 m/s ± 3.9 vs. 8.9 m/s ± 2.5) and Aix was significantly higher with Arteriograph than SphygmoCor too (29.3 ± 16.3 vs. 21.2 ± 12.6). The lack of agreement between the two methods is confirmed also by the Bland–Altman plot. Due to working principle of the Arteriograph possible conclusion is that parameters provided by the Arteriograph are the measures of brachial stiffness and not aortic stiffness. However, the method used by the Arteriograph is definitely much simpler and more time-efficient than applanation tonometry used by the SphygmoCor device.     

Methods of assessment of the arterial pulse wave in normal human pregnancy

OBJECTIVES: The study was undertaken to obtain normal values for characteristics of the peripheral arterial pulse wave, in nonpregnant women and in pregnant women at three different stages of gestation, with two devices, to describe cardiovascular hemodynamic variables induced by pregnancy. STUDY DESIGN: Sixty pregnant women were enrolled in the study at three stages of pregnancy, 17 to 20 weeks, 25 to 28 weeks, and 33 to 36 weeks gestation. Results are presented for 53 of these subjects who remained normotensive throughout pregnancy. The values measured were compared with those from 10 nonpregnant women. The two devices used were the SphygmoCor and a monitor invented and developed by Professor Edward Hon, not yet commercially available, referred to in this article as the "Hon" monitor. RESULTS: An increase in heart rate was observed in all pregnant women. Blood pressure values were lower in pregnancy than in normal nonpregnant women. With respect to the SphygmoCor, the time from the start of the arterial waveform to the second peak/shoulder, was significantly shorter, and augmentation pressure and augmentation index were significantly lower in pregnancy. Data obtained from the "Hon" monitor showed no significant differences in pulse wave arrival time, but rapid ejection time was significantly shortened in pregnancy. CONCLUSION: The clinical findings confirm the known cardiovascular changes of pregnancy associated with vasodilatation of peripheral vessels and expansion of blood volume. The fall in augmentation pressure and index are consistent with these changes. Rapid ejection time and the time from the start of the arterial waveform to the second peak/shoulder, which should reflect similar cardiovascular physiologic events, were weakly correlated.