Abstract 3636: Central Systolic Blood Pressure Can Be Estimated from the Point of Systolic Augmentation in the Finger Pressure Pulse
Central and peripheral systolic blood pressure and arterial waveforms differ due to effects of wave reflection and amplification. Use of a mathematical transform function applied to peripheral waveforms to predict central waveforms remains controversial. It may be possible to estimate central systolic pressure directly from a peripheral waveform. We investigated this in subjects undergoing cardiac catheterisation, and examined the effects of heart rate and the administration of intravenous nitroglycerin (NTG) on the relationship between central and peripheral pulse. Patients undergoing coronary angioplasty at this institution (n=11, 10 male, 1 female, 48 to 72 years) were studied. Patients underwent femoral arterial and venous cannulation, a pressure catheter was positioned in the proximal aortic root. In 5 subjects a Millar SPC-454D catheter was used and in 6 a fluid filled catheter. Digital arterial waveforms and pressure were recorded using a servo controlled finger cuff (Finapres). A temporary pacing wire was then sited in the right atrium. Pacing was commenced at a rate 20 beats above resting heart rate until haemodynamic parameters stabilised. Pacing was then stopped and haemodynamic parameters allowed to return to baseline. IV NTG was then infused at doses of 10 and 100 μg/min, each for 5 min. Simultaneous finger and central pressure recordings were obtained at baseline and during the last 1 min of each period of intervention. Finger pressure was calibrated assuming equality of central and peripheral mean and diastolic blood pressure. Pacing and NTG produced marked changes in central and finger pressure waveforms, reducing central augmentation index from 40.4±6.2 to 22.6±8.9 and from 40.4±6.2 to 12.7±7.0 for pacing and NTG 100 μg/min respectively (each P<0.01). At baseline and during all interventions, there was a close correlation between central systolic blood pressure and absolute finger systolic pressure at the point of late systolic augmentation (R=0.95, P<0.0001). These data suggest that central systolic blood pressure can be estimated directly from finger pressure waveforms. Further data will be required to quantify the accuracy of this approach within a larger groups and when diastolic and mean pressures are estimated non-invasively.