An impaired carotid sinus distensibility and baroreceptor sensitivity alter autonomic activity in patients with effort angina associated with significant coronary artery disease

Vascular function: a key player in hypertension

The major functions of the arterial system are to "efficiently deliver blood to the peripheral organs and maintain vascular homeostasis". Both the endothelial and medial layer contribute to the three major functions, namely, conversion of pulsatile to steady blood flow, appropriate distribution of blood flow to the target organs, and vascular protection and homeostasis. Vascular dysfunction contributes to the development of cardiovascular diseases through a combination of several mechanisms, including impaired coronary perfusion, cardiac systolic/diastolic dysfunction, microvascular damage, and abnormal hemodynamics in the arterial tree. The representative marker of endothelial function is flow-mediated vasodilatation and that of the medial layer function is pulse wave velocity, and that of the blood supply function of the arterial tree is the ankle-brachial pressure index. In hypertension, vascular dysfunction could also lead to the development of isolated systolic hypertension, isolated diastolic hypertension, and systolic/diastolic hypertension. Vascular dysfunction is involved in a vicious cycle with abnormal blood pressure variability. Furthermore, a vicious cycle may also exist between vascular dysfunction and hypertension. While the significances of vascular function tests to predict future cardiovascular events has been established in cases of hypertension, their usefulness in assessing the effectiveness of management of the vascular functions in hypertension on the cardiovascular outcomes has not yet been fully clarified. Thus, vascular dysfunction plays crucial roles in the pathophysiology of hypertension, and further research is warranted to establish strategies to improve vascular dysfunction in cases of hypertension. Vascular functions in the pathophysiology of hypertension. Vascular dysfunction and elevation of blood pressure are components of a vicious cycle even from their early stages, which including abnormal blood pressure variabilities. This vicious cycle is associated with hypertensive organ damage and also adverse cardiovascular outcomes. Strategies to break this vicious cycle have not yet been fully established.

Slow Heart Rate Recovery Is Associated with Increased Exercise-induced Arterial Stiffness in Normotensive Patients without Overt Atherosclerosis

BACKGROUND

This study evaluated whether blunted autonomic activity as measured by heart rate recovery (HRR) was associated with increased arterial stiffness, especially increased exercise-induced arterial stiffness, in normotensive patients without overt atherosclerosis.

METHODS

One hundred fifty-four normotensive patients without overt atherosclerosis who had undergone a treadmill exercise test were consecutively enrolled. HRR was measured at one minute after exercise. Brachial-ankle pulse wave velocity (baPWV) at rest was measured, and carotid arterial stiffness indices at rest (CSI at rest) and after exercise (CSI after exercise) were assessed.

RESULTS

Patients with slow HRR were older and tended to be male, and they had diabetes, higher resting and peak systolic blood pressures, higher resting heart rate, lower peak heart rate, lower metabolic equivalents, increased baPWV, and increased CSIs at rest and after exercise. HRR was inversely associated with baPWV and CSI after exercise when established cardiovascular risk factors were adjusted as confounding factors, and HRR was associated with CSI after exercise when resting systolic blood pressure and metabolic equivalent of tasks on cardiovascular risk factors were added as confounding factors.

CONCLUSIONS

Sympathovagal imbalance demonstrated by slow HRR was associated with increased arterial stiffness and, above all, was closely associated with exercise-induced arterial stiffness in normotensive patients without overt atherosclerosis. This phenomenon might have been observed because blunt carotid arterial vasomotion following exercise results from autonomic dysfunction as well as vascular endothelial dysfunction.

Autonomic dysfunction in ischemic stroke with carotid stenosis

OBJECTIVES

Impaired autonomic function is common in acute ischemic stroke. Previous limited studies have suggested that atherosclerosis may affect the distensibility of the carotid sinus and then impair the cardiovascular autonomic function. This study sought to investigate cardiovascular autonomic function in patients with ischemic stroke with carotid stenosis.

METHODS

Eighty-five patients with ischemic stroke (58 ones without carotid stenosis and 27 ones with carotid stenosis, average 6 months after stroke onset) and 37 elderly controls were recruited. All performed Ewing's battery autonomic function tests.

RESULTS

From Ewing's battery of autonomic function tests, atypical, definite, or severe autonomic dysfunction was identified in 69.0% patients without carotid stenosis and 88.9% with carotid stenosis, with significant difference between the two groups, and the prevalence of autonomic dysfunction in both groups was higher than that in controls (21.6%). Patients with carotid stenosis showed impairment of all parasympathetic tests (all P < 0.05) and one of the sympathetic tests [Mean fall in systolic blood pressure (BP) on standing: P = 0.051], and those without carotid stenosis only showed impairment in two parasympathetic tests (Valsalva ratio: P = 0.014; heart rate response to deep breathing: P < 0.001) in comparison with controls. Patients with carotid stenosis had significantly more impairment than those without carotid stenosis in some autonomic parameters (Valsalva ratio: P < 0.05; mean fall in systolic BP on standing: P < 0.05).

CONCLUSIONS

Cardiovascular autonomic function is impaired in patients with ischemic stroke, but patients with carotid stenosis show more severely impaired parasympathetic and sympathetic functions.

Inter-relations among declines in arterial distensibility, baroreflex function and respiratory sinus arrhythmia

OBJECTIVES

We hypothesized that structural and neural cardiovascular (CV) deficits may be intimately linked. Specifically, decreased carotid distensibility with age may blunt the arterial baroreflex, thereby reducing resting cardiac vagal tone.

BACKGROUND

Increased CV risk is associated with lower carotid distensibility, impaired baroreflex function and reduced respiratory sinus arrhythmia (RSA), possibly representing a direct path between structural and neural CV deficits.

METHODS

We estimated the mechanostructural and neural components of baroreflex function and examined their relation to RSA in young (20 to 31 years) and older (59 to 71 years) subjects rigorously screened for CV and autonomic diseases.

RESULTS

In the older subjects, RSA was < 20% of that in the younger subjects. Moreover, mechanical transduction of pressure into barosensory vessel stretch was approximately 40% lower (p < 0.05) and arterial baroreflex gain more than 60% lower (p < 0.05) in the older group. Although neural transduction of stretch into vagal outflow only tended to be less (p < 0.08), it was an important determinant of baroreflex function. A path analysis model showed comparable contributions of both the mechanical and neural components to baroreflex gain; however, lower overall baroreflex gain in the older group did not relate to lower RSA.

CONCLUSIONS

These data suggest that decreased carotid distensibility does reduce baroreflex function with age, but this does not lead to reduced resting vagal outflow.

Comparison of aortic arch and carotid sinus distensibility in humans--relation to baroreflex sensitivity

We compared aortic arch (AA) and carotid sinus (CS) distensibility, and determined the relationship between baroreflex sensitivity (BRS) and distensibility coefficients of AA and CS (DCAA and DCCS, respectively). In 47 healthy 19-71-year-old subjects, AA and CS end-diastolic diameter (D) and pulsatile distension (delta D) was measured with ultrasound and arterial pressure by sphygmomanometer and Finapres. DC was calculated as 2delta D/(D x delta P), where delta P is the pulse pressure. BRS was determined by the sequence method. Data are given as mean +/- S.D.; significance was set at p < 0.05. DCAA and DCCS were linearly related across subjects (r = 0.80, p < 0.001). No difference between DCAA and DCCS (3.8 +/- 1.4 x 10(-3) and 4.2 + 2.2 x 10(-3) mm Hg(-1), respectively) was found for all subjects (paired t-test). However, at ages < 35 years, DCCS exceeded DCAA, whereas this relation was reversed at ages > 35 years. Age accounted for 53% of variability in DCAA and 73% of variability in DCCS. BRS was related to DC (linear regression), with the BRS-DCAA relation being steeper and closer (r = 0.73, p < 0.001) than the BRS-DCCS relation (r = 0.54, p < 0.05). It is suggested that aortic baroreceptors may have a dominant role in heart rate control.

Carotid arterial distensibility is an important determinant of improvement in autonomic balance after successful coronary angioplasty

OBJECTIVE

To determine whether arterial distensibility influences improvement of autonomic imbalance after left ventricular wall motion (LVWM) abnormality has been improved by percutaneous transluminal angioplasty (PTCA) in patients with ischemic heart disease (IHD).

METHODS AND RESULTS

The following variables were assessed before and 3 months after PTCA in 63 patients with IHD who had a successful PTCA: heart rate variability (standard deviation of all normal R-R intervals [SDNN] measured from 24 h Holter electrocardiograms), baroreceptor sensitivity (determined by the phenylephrine injection method), and carotid artery distensibility (determined by ultrasonography). Abnormalities of LVWM were assessed by cineventriculography. In a multivariate analysis, carotid artery distensibility before PTCA and changes in LVWM abnormality before and after PTCA were independently associated with changes in baroreceptor sensitivity and SDNN (P< 0.05). Patients were divided into two groups: one with impaired and one group with unimpaired initial carotid artery distensibility. After PTCA, LVWM was improved significantly in both groups, but baroreceptor sensitivity and SDNN were improved significantly (respectively from 5.0 +/- 3.3 to 5.9 +/- 3.9 ms/mmHg, P< 0.01 and from 111 +/- 47 to 128 +/- 54 ms, P < 0.01) only in patients with well-preserved carotid artery distensibility.

CONCLUSIONS

The beneficial effect of PTCA on autonomic balance was greater in patients with well-preserved carotid artery distensibility than in those with impaired carotid artery distensibility. These results suggest that the pathophysiological state of arterial distensibility may modify the autonomic balance even after myocardial ischemia-related LVWM abnormalities are improved.