Letters to the Editor
Central Versus Peripheral Blood Pressure Measurements
To the Editor:
One of the major difficulties of blood pressure (BP) measurements in clinical and experimental studies1 is the presence of systolic BP (SBP) and pulse pressure (PP) amplification.2 Because of the summation of the forward and backward pressure waves along the arterial tree, SBP and PP are significantly higher (≈14 mm Hg in humans) in peripheral than in central arteries, whereas diastolic and mean BP are similar or even somewhat lower (−1 mm Hg).2 This finding, widely accepted as a classical scientific result, has never been noted in any guideline of the literature on hypertension but has major consequences, which are poorly considered as relevant and are not discussed in the present recommendations.1 First, brachial (humans) and tail (rodents) BPs are quite indirect measurements to consider whether the goal of BP determinations is to establish a diagnosis and to evaluate end organ damage.3 In small animals, tail SBP measurements may even be considered very semiquantitative determinations, quite inappropriate compared with central BP measurements. Second, the phenotypic aspects of the BP curve differ markedly in peripheral and central arteries, and also according to age, because they are largely depending on the level of arterial stiffness and the timing of wave reflections for each particular artery. For instance, in the thoracic aorta of men, there are at least two phenotypes of the BP curve: one in younger and the other in older subjects.2 Third, SBP and PP amplifications are highly influenced by heart rate, with major consequences in animals of small size as rodents. For instance, in rats, PP amplification is present in normotensive rats4 but absent in hypertensive rats because of the association of reduced arterial length and BP-induced increase of arterial stiffness. In hypertensive rats, SBP and PP amplification may be restored after acute BP reduction by converting enzyme inhibitors and calcium entry blockers but not dihydralazine.4 In this respect, comparisons between rats and mice, which are characterized by quite different heart rate levels, have not been extensively performed, with potential major differences in the interpretation of BP level, organ damage, genes, and even level of myogenic tone.5
Kurtz TW, Griffin KA, Bidani AK, Davisson RL, Hall JE. Recommendations for blood pressure measurement in humans and experimental animals: part 2: blood pressure measurement in experimental animals: a statement for professionals from the subcommittee of professional and public education of the American Heart Association Council on High Blood Pressure Research. Hypertension. 2005; 45: 299–310.
Nichols WW, O’Rourke M. McDonald’s Blood Flow in Arteries: Theoretical, Experimental and Clinical Principles. 4th ed. London, Sydney, Auckland: Arnold Publication. 1998; 54–401.
Safar ME, and Laurent P. Pulse pressure and arterial stiffness in rats: comparison with humans. Am J Physiol. 2003; 285: H1363–H1369.
Loutzenhiser R, Bidani A, Chilton L. Renal myogenic response: kinetic attributes and physiological role. Circ Res. 2002; 90: 1316–1324.