Assessment of Baroreflex Sensitivity Using Time-Frequency Analysis during Postural Change and Hypercapnia

On the accuracy of sequence methods for baroreflex sensitivity estimation

In the absence of a true gold standard for non-invasive baroreflex sensitivity estimation, it is difficult to quantify the accuracy of the variety of techniques used. A popular family of methods, usually entitled 'sequence methods' involves the extraction of (apparently) correlated sequences from blood pressure and RR-interval data and the subsequent fitting of a regression line to the data. This paper discusses the accuracy of sequence methods from a system identification perspective, using both data generated from a known mathematical model and spontaneous baroreflex data. It is shown that sequence methods can introduce significant bias in the baroreflex sensitivity estimate, even when great care is taken in sequence selection.

Assessment of baroreflex sensitivity during isometric handgrip exercise and oscillatory lower body negative pressure

Objectives

Baroreflex sensitivity (BRS) is an estimate of autonomic control of cardiovascular system via the baroreflex arc. It has been suggested that exercise pressure reflex and muscle metaboreflex override baroreflex during exercise to decrease baroreflex gain, which facilitates the simultaneous rise in blood pressure (BP) and heart rate during the exercise. This study investigated the effects of isometric handgrip exercise (IHE) on baroreflex gain and frequency dependence of baroreflex sensitivity while fluctuations in arterial BP were generated.

Methods

Thirteen healthy men performed IHE at 20% and 30% of their maximum voluntary contraction (MVC), while oscillatory lower body negative pressure (OLBNP) of 40 mmHg was applied in 0.1 and 0.25 Hz frequencies.

Results

Compared to the OLBNP at 0.25 Hz frequency alone, the baroreflex gain for diastolic BP (DBP) was significantly reduced with the addition of IHE at 20% and 30% of MVC in the high frequency band. At rest (without IHE and OLBNP) the baroreflex gain was significantly more in the high frequency band for DBP, but the baroreflex gain for DBP was not significantly different when IHE + OLBNP were applied at 20% and 30% of MVC in both frequencies.

Conclusions

The significant reduction of DBP baroreflex gain with the addition of graded IHE might indicate that exercise pressure reflex and muscle metaboreflex override baroreflex during exercise to decrease baroreflex gain at a high frequency band (0.25 Hz). The frequency-dependent phenomenon of BRS was altered when IHE and OLBNP were applied, meaning that the frequency dependence of BRS was nullified during IHE.

Blood Pressure Variability Can Predict Carotid Sinus Reaction After Carotid Stenting

BACKGROUND

Carotid stenting has become an important treatment for carotid disease. Carotid sinus reaction (CSR), a complication which is not uncommon and affects the outcome of carotid stenting. We investigated the predictors of CSR, including blood pressure variability and heart rate variability (BPV and HRV, respectively).

METHODS

We enrolled patients who underwent carotid stenting. CSR was defined as any episode of systolic blood pressure (SBP) <90 mm Hg or heart rate (HR) <60 beats/min after stent deployment or balloon inflation. BPV and HRV were measured before stent insertion and were represented by coefficient of variation (CoV) and SD. Multivariable logistic regression was performed to predict CSR.

RESULTS

Among the 176 patients, 61 (34.7%) patients showed CSR. Blood pressure and HR were measured 14 times before carotid stenting on average. The risk of CSR was independently associated with the use of longer stent (odds ratio: 1.08, 95% confidence interval: 1.00-1.16, P = 0.042) and increased SBP SD (1.07 [1.00-1.14], P = 0.048). Moreover, when the SBP parameter changed to SBP CoV, total stent length (1.08 [1.00-1.16], P = 0.042) and SBP CoV (1.12 [1.02-1.23], P = 0.023) were associated with the occurrence of CSR.

CONCLUSIONS

The use of a longer stent and increased SBP variability before carotid stent insertion were associated with the risk of CSR after carotid stenting. Underlying autonomic dysregulation may increase the risk of CSR during carotid stenting. SBP variability before carotid stenting might be considered a predictor of CSR.

The Effect of Wet Cupping on Baroreceptor Sensitivity in Hypertensive Patients in Sidenreng Rappang Regency, South Sulawesi

Wet cupping therapy  removes toxins  thereby increasing blood flow and  stimulating baroreceptors sensitivity which provides a stimulus to the autonomic nerves. This stimulus reduces the sympathetic nerves’ work and inhibits  the vasomotor center, leading to vasodilation, therefore decreasing blood pressure and pulse frequency. This research aims to determine the effect of wet cupping therapy on baroreceptors sensitivity with blood pressure and pulse frequency indicators. It was conducted in Sidenreng Rappang Regency, South Sulawesi, eastern Indonesia from February to May 2021. Randomized Controlled Trial (RCT) method was used including two groups of 31 respondents each. The intervention group used wet cupping therapy to regulate anti-hypertensive drugs and the control group used anti-hypertensive drugs with blood pressure and pulse frequency measurements until 6 weeks after the therapy. Wet cupping affects baroreceptor sensitivity by reducing the indicators. The result showed a significant difference in blood pressure measurement (systolic; diastolic) before and after the 2-week follow-up period (P = 0.000; P = 0.001), and between 2 and 4 weeks (P = 0.000; P = 0.000), but between 4 and 6 weeks there was no significant difference in the intervention group (P = 0.248; P = 0.583). There was a significant difference in pulse frequency at 2 and 4 weeks after the intervention (P = 0.016). In conclusion, wet cupping therapy effectively increases baroreceptor sensitivity by reducing blood pressure and pulse frequency indicators in hypertensive patients up to 4 weeks limit after the therapy, without any serious side effects experienced by respondents.

Blood Pressure Drop Rate After Standing Up Is Associated With Frailty and Number of Falls in Geriatric Outpatients

Background

The relationship between orthostatic hypotension and clinical outcome in older adults is poorly understood. Blood pressure drop rate (ie, speed of blood pressure drop) may particularly reflect the imposed challenge to the baroreflex and the associated clinical outcome (ie, frailty and number of falls). This study aimed to compare orthostatic blood pressure drop rate and drop magnitude with regard to their association with frailty and number of falls.

Methods and Results

Blood pressure was measured continuously during a standardized active stand task in 168 patients (mean age 81.4±7.0; 55.4% female) who visited a geriatric outpatient clinic for cognitive or mobility problems. The association of orthostatic blood pressure drop rate, blood pressure drop magnitude, and baroreflex sensitivity (ie, increase in heart rate divided by systolic blood pressure drop magnitude) with frailty (Fried criteria and 4 frailty markers) and self‐reported number of falls was assessed using linear regression models, adjusting for age and sex. Systolic blood pressure drop rate had the strongest association with frailty according to the 4 frailty markers (β 0.30; 95% CI, 0.11–0.49; P=0.003) and number of falls (β 1.09; 95% CI, 0.19–1.20; P=0.018); diastolic blood pressure drop magnitude was most strongly associated with frailty according to the Fried criteria (β 0.37; 95% CI, 0.15–0.60; P<0.001). Baroreflex sensitivity was associated with neither frailty nor number of falls.

Conclusions

Orthostatic blood pressure drop rate was associated with frailty and falls and may reflect the challenge to the baroreflex rather than drop magnitude.