Radial Artery Applanation Tonometry Research Articles

Augmentation Index and Systolic Load Are Lower in Competitive Endurance Athletes

Arterial stiffness increases with age, and chronic endurance exercise has been shown to attenuate increases in arterial stiffness in older individuals. The aim of this study was to assess the effect of varying fitness levels on wave reflection in young healthy adults. A total of 32 subjects (16 competitive endurance athletes and 16 recreationally active subjects) underwent brachial artery blood pressure (BP) measurement (by sphygmomanometry) and central aortic pressure (by noninvasive radial artery applanation tonometry and use of a generalized transfer function) measurements at rest. Central aortic augmentation index (AI), an index of wave reflection, and tension-time index (TTI), an indicator of systolic load, were calculated from the aortic pressure waveform. Physical fitness was determined through a maximal oxygen consumption (VO2max) test performed on a treadmill. The two groups did not differ in age, height, weight, resting BP, or blood lipids. The VO2max was significantly higher in the competitive group compared with the recreational group (65 +/- 1.9 v 49 +/- 1.8 mL/kg/min, P < .05). The AI was lower in the competitive group compared with the recreational group (-2.1% +/- 2.1% v 4.5% +/- 2.9%, P < .05), as was TTI (1679 +/- 61 v 1868 +/- 58, P < .05). Wave reflection is lower in competitive endurance athletes who have higher fitness levels and who exercise at a higher intensity, for a longer duration, and more frequently as compared with recreationally active individuals. These differences may be due to functional changes that occur as a result of training.

Arterial stiffness is increased in subjects with hypothyroidism

Background The association between hypothyroidism and increased vascular resistance, arterial wall thickening and endothelial dysfunction is well recognized. The aim of the present study was to examine if hypothyroid subjects have increased arterial stiffness, a risk factor for cardiovascular morbidity and mortality. Methods Sixty-five subjects (59 females and 6 males) with normal thyroid function or hypothyroidism of varying degree were investigated by radial artery applanation tonometry and pulse wave analysis, for evaluation of arterial stiffness. Results Serum TSH values were positively correlated with central systolic blood pressure ( r=0.258, p=0.037), central pulse pressure ( r=0.316, p=0.010), augmentation pressure ( r=0.299, p=0.015) and negatively with reflection time index (RTI), which indicates the pressure wave velocity ( r=−0.311, p=0.012). Hypothyroid patients presented higher central systolic pressure and pulse pressure, higher augmentation pressure and lower RTI, indicating increased arterial stiffness in these subjects. RTI was independently related to age, central systolic pressure and TSH. Mild changes of arterial stiffness were observed even in subjects with TSH range 2.01–4.0 μU/ml suggesting that this group may have an early stage of mild thyroid failure. Conclusions Hypothyroidism, even in the subclinical stage, is associated with changes in arterial stiffness. The observed abnormalities in arterial stiffness may have detrimental effects on left ventricular function and coronary perfusion in hypothyroid subjects.

EFFECTS OF EXERCISE TRAINING ON THE AMPLITUDE AND TIMING OF CENTRAL AORTIC PRESSURE WAVE REFLECTION IN CORONARY ARTERY DISEASE

Early return of wave reflection from peripheral reflecting sites augments systolic and pulse blood pressures and increases left ventricular external arterial load. Such changes are attributable to increased stiffening of the large elastic arteries and increased pulse wave velocity. PURPOSE The purpose of this study was to investigate the effects of 12 weeks of standard cardiac rehabilitation on the amplitude and timing of wave reflections in coronary artery disease. METHODS Ten coronary artery disease patients underwent 12 weeks of exercise training (ET) as part of a standard cardiac rehabilitation program and ten control patients (C) received 12 weeks of standard care and did not participate in supervised exercise. Brachial artery blood pressure was measured by sphygmomanometry and central aortic pressure was measured by noninvasive radial artery applanation tonometry and use of a generalized transfer function before and after the 12 week exercise or control period. Central aortic augmentation index (AIa) and delay of the reflected wave (Δt), indicators of arterial stiffness, were calculated from the aortic pressure waveform. RESULTS Twelve weeks of endurance exercise training did not alter heart rate, central or peripheral systolic, diastolic or pulse pressures but did result in a significant decrease in AIa (30.4% vs. 26.2%, p < 0.05) and a significant increase in Δt (136.2 vs. 144.4, p < 0.05) in the ET group. There were no changes in any of these parameters in the C group during the 12-weeks of standard care. CONCLUSION The present study is the first to investigate the effects of endurance training on arterial properties using pulse wave analysis in coronary artery disease patients. Pulse wave analysis demonstrated that 12-weeks of endurance training in coronary artery disease patients resulted in a reduction in arterial stiffness as evidenced by a reduction in AIa and an increase in Δt. Our results suggest that endurance exercise training improves systemic arterial stiffness.

Amplitude and timing of central aortic pressure wave reflections in heart transplant recipients

Background Hypertension (HTN) assessed by sphygmomanometer is a common finding in heart transplant recipients (HTR); however, little is known about the contribution of arterial wave reflection to central aortic pressure in these patients. The aim of this study was to measure the central aortic pressure wave in HTR on antihypertensive therapy and determine the effects of amplitude and timing of wave reflection on the various components of the wave. Methods A total of 53 stable adult HTR on antihypertensive medication underwent brachial artery blood pressure ([BP]; by sphygmomanometry) and central aortic pressure (by noninvasive radial artery applanation tonometry and use of a generalized transfer function) measurements at rest. Central aortic augmentation index (AIa), an indicator of arterial stiffness, was calculated from the aortic pressure waveform. Patients were divided into three groups (A, B, and C) based on the amplitude of AIa. Results Mean brachial BP was 136 ± 15/84 ± 9.4 mm Hg. Group A patients ( n = 25) had a higher AIa (average 21% ± 7.6%) than group B ( n = 18, AIa = 6.5% ± 3.0%, P < .001) or group C ( n = l0, AIa = −8.7% ± 8.1%, P < .001) patients. The amplitude of AIa was inversely related to the travel time (Δt p/2) of the reflected pressure wave from the periphery to the heart (r = −0.78, P < .001). Despite this clear stratification of patients by aortic pulse wave analysis, standard cuff pressure was similar among the groups. Conclusions Noninvasive analysis of the central aortic pressure wave identified a subgroup of hypertensive HTR with increased arterial stiffness, increased propagation of the reflected wave, and augmented aortic systolic and pulse pressure not identified with the sphygmomanometer.

Assessment of endothelial function using peripheral waveform analysis: A clinical application

ObjectivesThe study was done to determine whether radial artery applanation tonometry can be used as a noninvasive method of assessing global endothelial function. BackgroundIt is known that beta2-receptor stimulation results in endothelial release of nitric oxide. Furthermore, for over a century glyceryl trinitrate (GTN) has been known to markedly affect the arterial pressure waveform, even in the absence of significant blood pressure (BP) changes. Therefore, it was hypothesized that the change in the peripheral pressure waveform, as measured using tonometry and quantified using the augmentation index (AIx) and in response to Salbutamol (Salb), would allow assessment of global endothelial function. MethodsThe study contained three parts. In the first study, Salb (400 μg) was administered to 11 healthy subjects via inhalation after either intravenous N-ω-nitro-monomethyl-l-arginine (l-NMMA) (3 mg/kg over 5 min) or control solution (normal saline) in the supine, rested, fasted condition. The BP, heart rate and waveform responses were recorded each 5 min following Salb for 20 min. Next, GTN was given and responses recorded 5 min later. In the second study, both the reproducibility of Salb and the GTN responses were assessed in 9 subjects studied twice on separate days. In the third study, the Salb and GTN responses of 12 subjects with angiographic coronary artery disease (CAD) were compared with 10 age-matched control subjects with no atherosclerotic risk factors. ResultsAfter control infusion, AIx decreased following Salb, from 50.8 ± 4.3% to 44.8 ± 4.2%, a change of −11.8 ± 3.7%, p < 0.01. After l-NMMA, AIx did not significantly change following Salb (54.2 ± 5.1% vs. 52.9 ± 5.3%, −2.0 ± 3.1%). The GTN-induced decreases in AIx were similar after either infusion (35.1 ± 3.3% vs. 36.5 ± 3.3%). Reproducibility of Salb-induced changes in AIx between studies performed on separate days was good (r = 0.80, p < 0.01). Salb-induced changes in AIx in CAD patients were significantly less compared to control subjects (−2.4 ± 1.9% vs. −13.2 ± 2.4%, respectively, p < 0.002). The GTN-induced changes were not significantly different (−27.6 ± 4.2 vs. −38.9 ± 4.4%, p = 0.07). ConclusionsThe peripheral arterial pressure waveform is sensitive to beta2-stimulation. Changes are related to nitric oxide release, are reproducible and can distinguish between clinical subject groups. Arterial waveform changes following Salb may thus provide a noninvasive method of measuring “global” arterial endothelial function.

Development of a method for measuring myocardial contractility with gated myocardial SPECT and arterial tonometry

Background. Gated myocardial single photon emission computed tomography (SPECT) and radial artery applanation tonometry were used, respectively, to quantify the time-volume curve of the left ventricle and to estimate ventricular pressure wave. We developed ways of determining end-systolic elastance (Ees) with the normalized-single-beat method and tested the reproducibility of these measurements. Methods and Results. In patients with coronary artery disease (male/female = 33:2, age 66 ± 10 years, ejection fraction 22% to 77%), rest thallium-201 gated/poststress technetium-99m sestamibi gated SPECT/24-hour rest Tc-99m sestamibi gated SPECT and arterial tonometry were performed. Quantitative gated SPECT software yielded a systolic time-volume curve, and tonometrically measured radial artery pressure wave yielded central aortic pressure wave. With systolic half of pressure-volume curve, void volume (Vo) was estimated and Ees was calculated. Over 71 measurements Ees ranged from 1.7 to 5.3 and Vo from −4 to 200 mL. Ejection duration, other indexes of central pressure waveform, end-diastolic volume, end-systolic volume, and ejection fraction were reproducible. The reproducibility of Vo was excellent ( r = 0.97). Ees at rest (n = 15) showed fair reproducibility between Tc-99m-sestamibi and Tl-201 SPECT (r = 0.51). Conclusion. With gated myocardial SPECT, a noninvasive method of quantifying myocardial global contractility was developed. Reproducibility of this measurement was sufficient for use in clinical routine. Ees measured by this method warrants validation by invasively measured Ees.

Use of radial artery applanation tonometry and a generalized transfer function to determine aortic pressure augmentation in subjects with treated hypertension

Objectives. The purposes of this study were to investigate the use of radial artery applanation tonometry and a generalized transfer function for the assessment of central aortic pressure augmentation in subjects taking commonly used antihypertensive agents (angiotensin-converting enzyme inhibitors, beta-adrenergic blockers, Ca2+antagonists, diuretic therapy).Background. Applanation tonometry of the radial artery with a generalized transfer function has been proposed as a means of assessing central aortic blood pressure. Recently, a commercial apparatus based on this technique has become available; we therefore examined the effect of a generalized transfer function on derived central aortic pressure compared with measured brachial blood pressures and also investigated the potential of this technique to assess the influence of differing drug therapy.Methods. Two hundred and sixty-two hypertensive patients on stable medication were studied using the PWV Medical Blood Pressure Analysis System (version 2, DAT-1).Results. In univariate analysis, augmentation index showed association with age, sex, height and heart rate. In multivariate analysis, diastolic blood pressure and age (positively), height and heart rate (negatively) and sex were significantly associated. After adjustment for these variables, pressure augmentation was not associated with any antihypertensive treatment investigated. Linear relationships were demonstrated between brachial blood pressures and corresponding central pressures derived by transfer function methods.Conclusions. Our findings suggest that if adjustment for central-peripheral pressure difference is necessary, simple linear relationships may be sufficient. Age, heart rate and height but not the class of antihypertensive medication affected the degree of pressure augmentation observed using this technique.