How to assess central arterial blood pressure?

Noninvasive assessment of local pulse pressure: importance of brachial-to-radial pressure amplification

The advocated SphygmoCor procedure uses a radial-to-aorta transfer function with calibration on brachial instead of radial artery pressure to assess the central pulse pressure. We compared these values with carotid artery pulse pressures obtained from a validated calibration method, assuming mean minus diastolic blood pressure constant throughout the large artery tree. From 44 healthy subjects (21 males; 22 to 68 years) pressure waves were obtained at the radial, brachial, and carotid artery with applanation tonometry. Using the calibration method, radial and carotid artery pressures were assessed from brachial artery waves and pressures. The effect of brachial-to-radial pulse pressure amplification, brachial pulse pressure, mean pressure, age, gender, height, body mass index, and smoking on differences between the 2 methods was assessed. Brachial artery pressure was 118+/-12/72+/-10 mm Hg. SphygmoCor central pulse pressure was 9.7+/-4.6 mm Hg lower (P<0.001) than the carotid artery pulse pressure (33.0+/-6.8 versus 42.7+/-8.9 mm Hg). The difference between the 2 methods strongly depended (P<0.001) on brachial-to-radial artery pulse pressure amplification (5.8+/-5.1 mm Hg; 12+/-11%) and less on brachial artery pulse pressure (P=0.005). After calibration of the radial pressure wave with radial instead of brachial artery pressures, the difference between SphygmoCor central pulse pressure and carotid pulse pressure decreased with 4 mm Hg. The advocated SphygmoCor procedure systematically underestimates the central pulse pressure with brachial-to-radial pulse pressure amplification as important determinant. Therefore, calibration of radial artery pressure waves on brachial artery pressures should be avoided. The underestimation of central aortic pulse pressure caused by the radial-to-aorta transfer function itself is much less than previously reported.

Ascending aortic, but not brachial blood pressure-derived indices are related to coronary atherosclerosis

A recent study has demonstrated that pulse pressure (PP) measured in the ascending aorta is related to the extent of coronary artery disease in patients undergoing coronary angioplasty. However, no study so far has analyzed the relation between pulsatility of the ascending aorta and the extent of coronary artery disease in consecutive patients undergoing coronary angiography. Therefore, we investigated the relation between ascending aorta pulsatility and the extent of coronary atherosclerosis in unselected patients with angiographically confirmed coronary artery disease. The study group consisted of 423 consecutive patients (334 men and 89 women; mean age: 58.6+/-9.7 years) with angiographically confirmed coronary artery disease and ejection fraction < or =60% PP, fractional pulse pressure (the ratio of pulse pressure to mean pressure, FPP), and the ratio of pulse pressure to diastolic pressure (pulsatility index, PI) derived from intraaortic measurements differentiated patients with one-, two- and three-vessel coronary artery disease (PP, 63.0+/-16.0 versus 64.2+/-18.3 versus 71.8+/-19.1 mmHg (P < 0.0001); FPP, 0.68+/-0.14 versus 0.69+/-0.15 versus 0.76+/-0.17 (P < 0.0001); PI 0.89+/-0.25 versus 0.92+/-0.27 versus 1.04+/-0.32 (P < 0.0001)). After multivariate stepwise adjustment, the odds ratio (OR) and confidence interval (CI) of having three-vessel disease was: PP per 10 mmHg OR 1.15 (95% CI 1.02-1.31); FPP per 0.1 OR 1.18 (95% CI 1.02-1.37); and PI per 0.1 OR 1.11 (95% CI 1.03-1.21). None of brachial blood pressure indices was independently related to the extent of coronary atherosclerosis.

CONCLUSION

Pulse pressure, fractional pulse pressure, and pulsatility index of the ascending aorta are related to the risk of three-vessel disease in patients with coronary artery disease and preserved left ventricular function.

Protective effects of ascorbic acid on arterial hemodynamics during acute hyperglycemia

Mortality increases when acute coronary syndromes are complicated by stress-induced hyperglycemia. Early pulse wave reflection can augment central aortic systolic blood pressure and increase left ventricular strain. Altered pulse wave reflection may contribute to the increase in cardiac risk during acute hyperglycemia. Chronic ascorbic acid (AA) supplementation has recently been shown to reduce pulse wave reflection in diabetes. We investigated the in vivo effects of acute hyperglycemia, with and without AA pretreatment, on pulse wave reflection and arterial hemodynamics. Healthy male volunteers were studied. Peripheral blood pressure (BP) was measured at the brachial artery, and the SphygmoCor pulse wave analysis system was used to derive central BP, the aortic augmentation index (AIx; measure of systemic arterial stiffness), and the time to pulse wave refection ( Tr; measure of aortic distensibility) from noninvasively obtained radial artery pulse pressure (PP) waveforms. Hemodynamics were recorded at baseline and then every 30 min during a 120-min systemic hyperglycemic clamp (14 mmol/l). The subjects, studied on two separate occasions, were randomized in a double-blind, crossover manner to placebo or 2 g intravenous AA before the initiation of hyperglycemia. During hyperglycemia, AIx increased and Tr decreased. Hyperglycemia did not change peripheral PP but did magnify central aortic PP and diminished the normal physiological amplification of PP from the aorta to the periphery. Pulse wave reflection, as assessed from peripheral pulse wave analysis, is enhanced during acute hyperglycemia. Pretreatment with AA prevented the hyperglycemia-induced hemodynamic changes. By protecting hemodynamics during acute hyperglycemia, AA may have therapeutic use.

Ascending aortic blood pressure waveform may be related to the risk of coronary artery disease in women, but not in men

Recent studies have demonstrated that fractional pulse pressure and fractional diastolic pressure are related to the risk of coronary artery disease. However, the effect of the ascending aortic pressure waveform on the risk of coronary artery disease in men and women analyzed separately has not been reported. The objective of the study was to assess the relation between ascending aortic blood pressure waveform and the presence of coronary artery disease in men and in women. The study group consisted of 447 patients (302 men and 145 women; mean age: 57.6+/-9.8 years) with preserved left ventricular function who were undergoing first diagnostic coronary angiography. After multivariate stepwise adjustments, the odds ratio (OR) and confidence interval (CI) of having coronary artery disease in women was (OR are reported for standard deviation increase in each variable): pulse pressure OR 1.61 (95% CI 1.06-2.46); fractional systolic pressure OR 1.72 (95% CI 1.08-2.71); fractional diastolic pressure OR 0.58 (95% CI 0.37-0.92); fractional pulse pressure OR 1.72 (95% CI 1.08-2.71); and pulsatility index OR 1.74 (95% CI 1.09-2.78). None of the studied variables was independently related to the presence of coronary artery disease in men. In conclusion, fractional systolic and diastolic pressure, pulse pressure, fractional pulse pressure and the ratio of pulse pressure to diastolic pressure may be independently related to the risk of coronary artery disease in women, but not in men.