Aortic Pulse Wave Reflection Research Articles

Central blood pressure and aortic pulse wave reflection in water-exercised postmenopausal hypertensive women: A cross-sectional study.

Exercise training has been associated with the attenuation of cardiovascular impairment after menopause. This study aimed to compare central and peripheral blood pressure and aortic pulse wave reflection in sedentary and trained (aerobic exercise in the water) hypertensive postmenopausal women. Hypertensive postmenopausal women were divided into sedentary (SED, n=53) and trained groups (TR, n=31). Self-reporting from the trained group presented a mean of 1.7±0.3years of exercise practice in the water. Central blood pressure and amplification indexes (AIx) were obtained by the applanation tonometry of radial and aortic arteries. No changes were observed in systolic blood pressure (SBP) in the TR group than the SED group; however, office diastolic blood pressure (DBP) was reduced compared to the SED group. Central blood pressure and augmentation index (AIx@75%) values were similar in the SED and TR groups. These data suggest that self-reported long-term exercise training in the water could not improve central hemodynamic variables in postmenopausal hypertensive women compared to sedentary ones. However, it should be emphasized that DBP levels were reduced in trained subjects, which might reduce cardiovascular outcomes.

Influence of the cold pressor test upon aortic pulse wave reflection in individuals with increased arterial stiffness

Aortic pulse wave reflection is an indicator of LV after load, myocardial O2 demand and a predictor of cardiovascular events and is partly determined by muscular and elastic artery stiffness and pulse wave velocity. Acute stimulation of the sympathetic nervous system increases the vascular resistance of the muscular arteries thereby influencing arterial stiffness. The aim of this study was to examine the influence of acute sympathetic stimulation via the cold pressor test upon aortic pulse wave reflection in individuals with and without increased arterial stiffness. Eleven participants (4 males, 31±12yrs; 172±10cm; 75±15kg) completed a cold pressor test (CPT) wherein the left hand was immersed up to the wrist in 2–4°C water for 3 minutes. Blood pressure (mean arterial pressure; MAP) and pulse wave reflection (radial tonometry) were measured throughout. Stroke volume was calculated (photoplethysmography; NexFin) and heart rate measured (ECG; HR) throughout to provide cardiac output (Q). Aortic pulse wave velocity was measured before the CPT (Mobil‐O‐Graph®; aPWV). Pulse wave reflection was referenced to a heart rate of 75 bpm (augmentation index; Aix75). At baseline heart rate was 66±8 bpm and the change during CPT was variable between participants (Range: −11 to +14 bpm). Prior to CPT, Aix75 was 0±19% (Range −31 to 31%) and MAP was 87±10 mmHg. During the CPT Aix75 increased to 17±13% while MAP increased to 102±7 mmHg (both P ≤ 0.05). The change in Aix75 during CPT correlated poorly with age (R2 = 0.13), baseline MAP (R2 = 0.03), the change in MAP during CPT (R2 = 0.05) and baseline aPWV (R2 = 0.08) (all P > 0.05). However, the increase in Aix75 during the CPT correlated moderately with baseline Aix75 (R2 = 0.75; P = 0.0006) and the change in Q during CPT (R2 = 0.40; P = 0.049). Increases in aortic pulse wave reflection during the cold pressor test were inversely related to baseline aortic pulse wave reflection. This may be indicative of a ceiling effect where individuals with evidence of existing arterial stiffening demonstrate a reduced increase in pulse wave reflection during sympathetic stimulation via cold pressor test. Nevertheless individuals with evidence of increased arterial stiffness still experience acute increases in pulse wave reflection during sympathetic stimulation via the cold pressor test.

Effect of acute lower leg heating on aortic pulse wave reflection in postmenopausal women

Postmenopausal women exhibit greater aortic pulse wave reflection, a cardiovascular disease risk, compared with premenopausal women. This might be partly attributed to the elevated peripheral vascular resistance. In this study, we examined in postmenopausal women whether aortic pulse wave reflection was decreased by acute lower leg heating (LLH) which expectedly reduced local vascular tone. Using a chamber incorporated with far infrared radiation heater, 13 postmenopausal women (64±1 years) underwent 20 minutes of supine resting with and without LLH (at ∼44ºC and room temperature, respectively) on separate days by cross‐over design. Blood pressure, aortic and leg pulse wave velocity (PWV) and aortic augmentation index (AI) were measured before, 30 min and 60 min after each intervention. AI and leg PWV decreased 30 min after LLH (P<0.05 for both) and returned to the baseline 60 min after LLH, whereas blood pressure and aortic PWV did not change significantly. No significant changes were observed in these parameters in the control trial. Changes in the difference between leg PWV and aortic PWV (Δleg PWV – aortic PWV) correlated with corresponding changes in AI (r=0.686, P<0.05), suggesting that LLH‐induced change in impedance mismatch between central elastic and peripheral muscular arteries might be associated with the decrease in aortic AI. In postmenopausal women, LLH might be available for the acute reduction of left ventricular afterload.

Aortic augmentation index and pulse wave velocity in response to head-up tilting

Aortic augmentation index (AIx) but not carotid-femoral pulse wave velocity (cfPWV) has reported to decrease in response to vasodilators, which has been related to changes in the timing and/or intensity of wave reflection. Yet, recent evidence indicates that arterial reservoir pressure rather than wave reflection is the most important determinant of AIx. Using radial artery applanation tonometry and a general transfer function AIx, aortic pulse wave reflection time and cfPWV (foot-to-foot method) were determined in 10 patients with severe autonomic failure and in 14 healthy individuals during supine rest and graded head-up tilting. During supine rest, mean blood pressure (BP) (127.6 ± 21.5 and 97.5 ± 9.4 mmHg), AIx (32.4 ± 13.0 and 23.1 ± 8.7%) and cfPWV (12.1 ± 3.6 and 8.9 ± 1.6 m/s) were higher in patients than in controls. In patients, BP decreased by 18.7 ± 9.8 and 39.6 ± 11.7%, AIx by 39.2 ± 27.5 and 100.9 ± 78.1% and cfPWV by 12.0 ± 10.5 and 27.7 ± 13.5% in response to 30 and 60° head-up tilting. Decreases in AIx and cfPWV correlated with the BP fall (r = 0.67, P = 0.001 and r = 0.75, P < 0.001), but changes in AIx and cfPWV were unrelated. In controls, AIx during head-up tilting decreased despite increases in vascular tone and cfPWV. Aortic reflection time in patients and controls during tilting did not change. Stepwise regression analysis revealed that 68% of the variation in AIx could be explained by the BP fall and reflection time and 76% of the variation in cfPWV by the BP fall and sex. In a clinical model of autonomic failure, both AIx and cfPWV largely depend on instantaneous BP, but these two variables are unrelated, supporting the contention that aortic reservoir pressure rather than wave reflection is the main determinant of AIx.

Arterial Stiffness and Dialysis Calcium Concentration

Arterial stiffness is the major determinant of isolated systolic hypertension and increased pulse pressure. Aortic stiffness is also associated with increased cardiovascular morbidity and mortality in patients with chronic kidney disease, hypertension, and general population. Hemodynamically, arterial stiffness results in earlier aortic pulse wave reflection leading to increased cardiac workload and decreased myocardial perfusion. Although the clinical consequence of aortic stiffness has been clearly established, its pathophysiology in various clinical conditions still remains poorly understood. The aim of the present paper is to review the studies that have looked at the impact of dialysis calcium concentration on arterial stiffness. Overall, the results of small short-term studies suggest that higher dialysis calcium is associated with a transient but significant increase in arterial stiffness. This calcium dependant increase in arterial stiffness is potentially explained by increased vascular smooth muscle tone of the conduit arteries and is not solely explained by changes in mean blood pressure. However, the optimal DCa remains to be determined, and long term studies are required to evaluate its impact on the progression of arterial stiffness.

News on migraine: genetics, genetics, and aortic stiffness

Migraine is the most frequent episodic neurological disorder. In Europe about 8% of males and 17% of females are affected. It has a complex pathophysiology, which also involves genetic factors. In contrast to hemiplegic migraine, for instance, the genetic background of migraine had so far not been identified. In a recent study published in Nature Genetics, a common susceptibility variant was found on chromosome 8q22.1. This is located between two genes which are involved in glutamate homeostasis. This seems quite appropriate, since an accumulation of glutamate most likely increases the susceptibility to migraine due to increased sensitivity to cortical spreading depression, the likely mechanism for migraine aura. In the second article, the frequency of de novo mutations in the CACNA1A and ATP1A2 genes in young subjects with early-onset sporadic hemiplegic migraine was evaluated. In the population of 25 patients, mutations were found in 19 patients, i.e. 76%. This is quite a high percentage that might be related to the patient group evaluated. However, it also shows that genetic testing is indicated in these patients. The third article deals with aortic stiffness and pulse wave reflection in young subjects with migraine. It shows a significantly higher aortic pulse wave reflection and aortic augmentation. Both are assumed to be risk factors for ischemic stroke and other cardiovascular events. These findings may be the link between the known increased risk of stroke and cardiovascular events in subjects suffering from migraine.

Systolic hypertension in the elderly: pushing the frontiers of therapy--a suggested new approach.

In elderly patients with systolic hypertension resistant to treatment with conventional therapy, increased aortic pulse wave reflection and a high augmentation index are often present. These findings are indicative of endothelial dysfunction and deficient generation of nitric oxide, a potent vasodilator in the arterial tree. In such patients, treatment with the nitric oxide donor extended-release isosorbide mononitrate characteristically produces prompt and sustained falls in both pulse wave reflection and systolic blood pressure. The adjunct use of this nitrate produces useful additional decreases in systolic blood pressure ranging from 10 to 45 mm Hg, often achieving target blood pressure goals in isolated systolic hypertension. By combining this endothelium-independent nitric oxide donor with angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, the potential exists to address both the nitric oxide deficiency and endothelial dysfunction of the vascular endothelium in these patients. Other possibilities for synergism with this combination include complementary hemodynamic, circadian, and metabolic actions together with prevention of nitrate tolerance. Isosorbide mononitrate may also be used successfully with calcium channel blockers, beta blockers, and diuretics.