Severe carotid barochemoreceptor involvement in stroke

Prevalence of orthostatic hypertension and its association with cerebrovascular diagnoses in patients with suspected TIA and minor stroke

Purpose

We aimed to compare the rate of stroke, transient ischemic attack, and cerebrovascular disease diagnoses across groups of patients based on their orthostatic blood pressure response in a transients ischemic attack clinic setting.

Materials and Methods

We retrospectively analysed prospectively collected data from 3201 patients referred to a transient ischemic attack (TIA)/minor stroke outpatients clinic. Trained nurses measured supine and standing blood pressure using an automated blood pressure device and the patients were categorized based on their orthostatic blood pressure change into four groups: no orthostatic blood pressure rise, systolic orthostatic hypertension, diastolic orthostatic hypertension, and combined orthostatic hypertension. Then, four stroke physicians, who were unaware of patients' orthostatic BP response, assessed the patients and made diagnoses based on clinical and imaging data. We compared the rate of stroke, TIA, and cerebrovascular disease (either stroke or TIA) diagnoses across the study groups using Pearson's χ² test. The effect of confounders was adjusted using a multivariate logistic regression analysis.

Results

Cerebrovascular disease was significantly less common in patients with combined systolic and diastolic orthostatic hypertension compared to the "no rise" group [OR = 0.56 (95% CI 0.35–0.89]. The odds were even lower among the subgroups of patients with obesity [OR = 0.31 (0.12–0.80)], without history of smoking [OR 0.34 (0.15–0.80)], and without hypertension [OR = 0.42 (95% CI 0.19–0.92)]. We found no significant relationship between orthostatic blood pressure rise with the diagnosis of stroke. However, the odds of TIA were significantly lower in patients with diastolic [OR 0.82 (0.68–0.98)] and combined types of orthostatic hypertension [OR = 0.54 (0.32–0.93)]; especially in patients younger than 65 years [OR = 0.17 (0.04–0.73)] without a history of hypertension [OR = 0.34 (0.13–0.91)], and patients who did not take antihypertensive therapy [OR = 0.35 (0.14–0.86)].

Conclusion

Our data suggest that orthostatic hypertension may be a protective factor for TIA among younger and normotensive patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02600-1.

Autonomic innervation of the carotid body as a determinant of its sensitivity: implications for cardiovascular physiology and pathology

The motivation for this review comes from the emerging complexity of the autonomic innervation of the carotid body (CB) and its putative role in regulating chemoreceptor sensitivity. With the carotid bodies as a potential therapeutic target for numerous cardiorespiratory and metabolic diseases, an understanding of the neural control of its circulation is most relevant. Since nerve fibres track blood vessels and receive autonomic innervation, we initiate our review by describing the origins of arterial feed to the CB and its unique vascular architecture and blood flow. Arterial feed(s) vary amongst species and, unequivocally, the arterial blood supply is relatively high to this organ. The vasculature appears to form separate circuits inside the CB with one having arterial venous anastomoses. Both sympathetic and parasympathetic nerves are present with postganglionic neurons located within the CB or close to it in the form of paraganglia. Their role in arterial vascular resistance control is described as is how CB blood flow relates to carotid sinus afferent activity. We discuss non-vascular targets of autonomic nerves, their possible role in controlling glomus cell activity, and how certain transmitters may relate to function. We propose that the autonomic nerves sub-serving the CB provide a rapid mechanism to tune the gain of peripheral chemoreflex sensitivity based on alterations in blood flow and oxygen delivery, and might provide future therapeutic targets. However, there remain a number of unknowns regarding these mechanisms that require further research that is discussed.

Carotid barochemoreceptor pathological findings regarding carotid plaque status and aging

BACKGROUND

Carotid barochemoreceptor pathological lesions have been studied in animals, but few human necropsies have been performed. Therefore, data rely on case patients following surgery, radiotherapy and carotid endarterectomy. Almost no data are available regarding whether the effect of aging prevails over pathological conditions, despite the classic description that glomic fibrosis increases with age.

OBJECTIVE

To morphometrically characterize the alterations of the carotid barochemoreceptors and their supplying arteries.

METHODS

Patients (n=23) who had suffered and died from stroke, with and without complicated internal carotid atheromatosis, were divided by age (group 1: older than 80 years; group 2: 65 to 80 years; and group 3: younger than 65 years). Carotid segments were obtained at autopsy. The specimens were stained for light microscopy and immunohistochemistry.

RESULTS

Carotid glomus presented from moderate-to-severe atrophy and fibrosis. A focal decrease in vascularization (CD34-positive) of the glomus (greater than 50%) was observed in areas of atrophy and fibrosis. Damaged nerve endings (S100 protein-positive) were observed at the media of the carotid sinus. Morphometric data showed no differences between groups for glomus area, number of type 1 and 2 cells, and the wall to lumen arteriole ratio. No statistical differences were demonstrated in the pathological findings of the carotid glomus when comparing complicated with noncomplicated plaques or age groups.

CONCLUSION

Severe carotid chemoreceptor damage exists in patients who have died from stroke and suffered from carotid atheromatosis. These findings were independent from aging and plaque type. However, damage was correlated with a marked narrowing of the supplying arterioles as a consequence of hemodynamic and/or metabolic alterations (dyslipidemia, diabetes).