Determination of central blood pressure by a noninvasive method (brachial BP and QKD interval)

Abstract

The measurement of central blood pressure (BPc) has become a matter of importance. Several therapeutic trials have noted a different protective effect against cardiovascular complications with different antihypertensive strategies, but an identical decrease in brachial BP (BPb). A possible explanation lies in the different effects of the treatments on BPc. We propose a new noninvasive method for the automatic measurement of BPc based on the QKD interval, an arterial stiffness marker. This study was carried out on patients referred for cardiac catheterization. We simultaneously measured the central SBP (SBPc) invasively with a pigtail probe, and the BPb by a cuff coupled with recording of the QKD interval. Two cohorts were studied, one to define an algorithm of SBPc estimation and one to validate this algorithm. The first cohort included 65 patients. We performed 136 simultaneous measurements. In the multivariate analysis, four variables were significantly correlated with SBPc: mean BPb (mBPb), QKD, height and heart rate (HR) with the following regression equation: SBP = 105 + 1.29 × mBPb - 0.39 × HR - 0.30 × height - 0.11 × QKD. This equation estimated 81% of the variance of the invasive SBPc ± 13 mmHg. This algorithm was then tested in another cohort of 80 patients. Difference between measured and estimated SBPc was 2 ± 14 mmHg. This study showed that it is possible to estimate SBPc by simultaneous measurement of QKD and BPb. If further studies confirm these results, a noninvasive ambulatory method of monitoring of SBPc could be employed in clinical practice.