Baroreceptors in the Aortic Arch and Their Potential Role in Aortic Dissection and Aneurysms

Radiographic complicated and uncomplicated descending aortic dissections: aortic morphological differences by CT angiography and risk factor analysis

AIMS

To identify radiographic differences between patients with uncomplicated and complicated descending aortic dissections.

METHODS AND RESULTS

Between April 2009 and July 2021, 209 patients with acute descending aortic dissections were analysed as complicated (malperfusion, rupture, diameter progress, and diameter ≥ 55 mm) or uncomplicated. Detailed CTA measurements (slice thickness ≤ 3 mm) were taken in multiplanar reconstruction. A composite endpoint (early aortic failure) was defined as reoperation, diameter progression, and early mortality. Seventy-seven patients were female (36.8%) [complicated n = 27 (36.5%); uncomplicated n = 50 (37.0%) P = 1.00]. Seventy-four (35%) patients were categorized as morphologically complicated, and 135 (65%) as uncomplicated. In patients with complicated dissections, the dissection extended more frequently to the aortic bifurcation (P = 0.044), the coeliac trunk (P = 0.003), the superior mesenteric artery (P = 0.007), and both iliac arteries (P < 0.001) originated less frequently from the true lumen. The length of the most proximal communication (entry) in type B aortic dissection was longer, 14.0 mm [12.0 mm; 27.0 mm] vs. 6.0 mm [4,0 mm; 13.0 mm] in complicated cases (P = 0.005). Identified risk factors for adverse aortic events were connective tissue disease [HR 8.0 (1.9-33.7 95% CI HR)], length of the aortic arch [HR 4.7 (1.5-15.1 95% CI HR)], a false lumen diameter > 19.38 mm [HR 3.389 (1.1-10.2 95% CI HR)], and origin of the inferior mesenteric artery from the false lumen [HR 4.2 (1.0-5.5 95% CI HR)].

CONCLUSION

We identified significant morphological differences and predictors for adverse events in patients presenting complicated and uncomplicated descending dissections. Our morphological findings will help guide future aortic therapies, taking a tailored patient approach.

The effects of cold exposure (cold water immersion, whole- and partial- body cryostimulation) on cardiovascular and cardiac autonomic control responses in healthy individuals: A systematic review, meta-analysis and meta-regression

BACKGROUND

Cryostimulation and cold-water immersion (CWI) have recently gained widespread attention due to their association with changes in cardiovascular and cardiac autonomic control responses. Therefore, the aim of the present systematic review and meta-analysis was to identify the global impact of such cold exposures on cardiovascular and cardiac autonomic activity.

METHODS

Three databases (PubMed, Embase, Web-of-Science) were used. Studies were eligible for inclusion if they were conducted on healthy participants using cryostimulation and/or CWI. The outcomes included measurements of blood pressure (BP), heart rate (HR), and heart rate variability (HRV) indices: RR interval (RR), Root mean square of successive RR interval differences (RMSSD), low frequency band (LF), high frequency band (HF), and LF/HF ratio.

RESULTS

Among the 27 articles included in our systematic literature review, only 24 were incorporated into the meta-analysis. Our results reveal a significant increase in HRV indices: RMSSD (Standardized mean difference (SMD) = 0.61, p < 0.001), RR (SMD = 0.77, p < 0.001), and HF (SMD = 0.46, p < 0.001), as well as significantly reduced LF (SMD = -0.41, p < 0.001) and LF/HF ratio (SMD = -0.25, p < 0.01), which persisted up to 15 min following cold exposure. Significantly decreased heart rate (SMD = -0.16, p < 0.05), accompanied by slightly increased mean BP (SMD = 0.28, p < 0.001), was also observed. These results seem to depend on individual characteristics and the cooling techniques.

CONCLUSION

Our meta-analysis suggests that cryostimulation and/or CWI exposure enhance parasympathetic nervous activity. There is scarce scientific literature regarding the effect of individual characteristics on cold-induced physiological responses.

eNOS plays essential roles in the developing heart and aorta linked to disruption of Notch signalling

eNOS (NOS3) is the enzyme that generates nitric oxide, a signalling molecule and regulator of vascular tone. Loss of eNOS function is associated with increased susceptibility to atherosclerosis, hypertension, thrombosis and stroke. Aortopathy and cardiac hypertrophy have also been found in eNOS null mice, but their aetiology is unclear. We evaluated eNOS nulls before and around birth for cardiac defects, revealing severe abnormalities in the ventricular myocardium and pharyngeal arch arteries. Moreover, in the aortic arch, there were fewer baroreceptors, which sense changes in blood pressure. Adult eNOS null survivors showed evidence of cardiac hypertrophy, aortopathy and cartilaginous metaplasia in the periductal region of the aortic arch. Notch1 and neuregulin were dysregulated in the forming pharyngeal arch arteries and ventricles, suggesting that these pathways may be relevant to the defects observed. Dysregulation of eNOS leads to embryonic and perinatal death, suggesting mutations in eNOS are candidates for causing congenital heart defects in humans. Surviving eNOS mutants have a deficiency of baroreceptors that likely contributes to high blood pressure and may have relevance to human patients who suffer from hypertension associated with aortic arch abnormalities.

A Rare Case of Profound Sinus Bradycardia in a Patient With Descending Aortic Dissection

A 34-year-old uncontrolled hypertensive male presented with chest pain radiating to the back. Despite severe pain, he was persistently bradycardic at 38 beats per minute. The workup at the emergency department confirmed the presence of an acute Stanford B aortic dissection. Stanford B dissections are not usually associated with bradycardia. It is Stanford A dissections that are mostly linked with bradycardia because Stanford A dissections can cause concomitant coronary artery extension and involvement of the atrioventricular node. This case demonstrates that sinus bradycardia can exist in the acute setting of any painful aortic dissection, even though it might not necessarily involve the coronary arteries.

Analysis of Mechanisms for Increased Blood Pressure Variability in Rats Continuously Infused with Angiotensin II

Objective

We reported that rats infused with angiotensin II (Ang II) are not only a model of hypertension but also of augmented 24 h blood pressure variability (BPV). In this study, we examined the mechanisms for Ang II-induced BPV, focusing on BP, heart rate (HR), baroreceptor reflex sensitivity (BRS), and medial area of the aortic arch.

Methods

Nine-week-old male Wistar rats were infused with subcutaneous 5.2 μg/kg/h Ang II with or without oral administration with 30 mg/kg/day azelnidipine for 14 days. BP and HR were recorded every 15 min under an unrestrained condition by a radiotelemetry system, while BPV was evaluated by standard deviation of BP. BRS was quantified by a sequence analysis, and medial thickness of the aortic arch was measured by microscopic examination.

Results

BPV increased at days 7 and 14 following continuous infusion of Ang II. Before the infusion, a positive correlation was found between BP and HR, but it became negative at day 7 and then weakened or disappeared at day 14. BRS was slightly impaired at day 7 and significantly lowered at day 14, a phenomenon accompanied by thickened medial area of the aortic arch in Ang II-infused rats. Those Ang II-induced alterations were all significantly attenuated by azelnidipine.

Conclusions

The present findings suggest sequential changes in the mechanisms behind augmented BPV in rats continuously infused with Ang II over 14 days.