Effects of potassium supplementation on plasma aldosterone: a systematic review and meta-analysis in humans

OBJECTIVES

Effects of potassium supplementation on blood pressure (BP) may be offset by an increase in plasma aldosterone. The magnitude of potassium-dependent regulation of aldosterone secretion in humans is not fully characterized; it is not clear whether this is mediated by activation of the renin-angiotensin-aldosterone system (RAAS), as a result of a reduction in BP or other mechanisms. We performed a systematic review and meta-analysis of clinical trials assessing effects of potassium on plasma aldosterone and renin in adult individuals.

METHODS

This was carried out in accordance with PRISMA guidelines. Three databases were searched: MEDLINE, EMBASE and CENTRAL. Titles were firstly screened by title and abstract for relevance before full-text articles were assessed for eligibility. The keywords used included "aldosterone", "potassium" and "RAAS".

RESULTS

6395 articles were retrieved and after title/abstract screening, 123 full-text articles were assessed for eligibility. Thirty-six met the prespecified inclusion/exclusion criteria (of which 18/36 also reported systolic BP). Potassium supplementation caused a significant decrease in systolic BP (mean difference [95% CI] -3.69 mmHg [-4.91, -2.46], P < 0.001) and increase in serum potassium (+0.37 [0.23, 0.52] mmol/l, P < 0.001). There was an increase in plasma aldosterone (standardized difference 0.426 [0.299, 0.553], P < 0.001) but not in plasma renin activity. Meta-regression showed a significant positive correlation between change in plasma aldosterone and change in serum potassium (P < 0.001).

CONCLUSIONS

Potassium supplementation increases plasma aldosterone concentrations, which correlates with the increase in serum potassium concentration which does not appear to be mediated by an increase in plasma renin activity.

Impaired β 2 -adrenergic endothelium-dependent vasodilation in patients previously hospitalized with coronavirus disease 2019

AIM

The pulse wave response to salbutamol (PWRS) - change in augmentation index (AIx) - provides a means to assess endothelial vasodilator function in vivo . Endothelial dysfunction plays a relevant role in the pathogenesis of hypertension and cardiovascular disease and appears to underlie many of the complications of coronavirus disease 2019 (COVID-19). However, to what degree this persists after recovery is unknown.

METHODS

Individuals previously hospitalized with COVID-19, those recovered from mild symptoms and seronegative controls with well known risk factors for endothelial dysfunction were studied. To assess the involvement of nitric oxide-cyclic guanosine monophosphate pathway (NO-cGMP) on PWRS, sildenafil was also administrated in a subsample.

RESULTS

One hundred and one participants (60 men) aged 47.8 ± 14.1 (mean ± SD) years of whom 33 were previously hospitalized with COVID-19 were recruited. Salbutamol had minimal effect on haemodynamics including blood pressure and heart rate. It reduced AIx in controls ( n  = 34) and those recovered from mild symptoms of COVID-19 ( n  = 34) but produced an increase in AIx in those previously hospitalized: mean change [95% confidence interval] -2.85 [-5.52, -0.188] %, -2.32 [-5.17,0.54] %, and 3.03 [0.06, 6.00] % for controls, those recovered from mild symptoms and those previously hospitalized, respectively ( P  = 0.001). In a sub-sample ( n  = 22), sildenafil enhanced PWRS (change in AIx 0.05 [-2.15,2.24] vs. -3.96 [-7.01. -2.18], P  = 0.006) with no significant difference between hospitalized ( n  = 12) and nonhospitalized participants ( n  = 10).

CONCLUSIONS

In patients previously hospitalized with COVID-19, there is long-lasting impairment of endothelial function as measured by the salbutamol-induced stimulation of the NO-cGMP pathway that may contribute to cardiovascular complications.

A pilot study to evaluate the erythrocyte glycocalyx sensitivity to sodium as a marker for cellular salt sensitivity in hypertension

Supressed plasma renin in patients with primary hypertension is thought to be an indirect marker of sodium-induced volume expansion which is associated with more severe hypertension and hypertension-mediated organ damage. A novel test for erythrocyte glycocalyx sensitivity to sodium (eGCSS) has been proposed as a direct measure of sodium-induced damage on erythrocyte surfaces and a marker of sensitivity of the endothelium to salt in humans. Here we explore if eGCSS relates to plasma renin and other clinical and biochemical characteristics in a cohort of patients with primary hypertension. Hypertensive subjects (n = 85, 54% male) were characterised by blood biochemistry (including plasma renin/aldosterone), urine analysis for albumin-creatinine ratio (ACR), 24-h urine sodium/potassium excretion. eGCSS was measured using a commercially available kit. Correlations between eGCSS and clinical and biochemical characteristics were explored using Spearman's correlation coefficient and characteristics compared across tertiles of eGCSS. eGCSS was inversely correlated with renin (p < 0.05), with renin 17.72 ± 18 µU/l in the highest tertile of eGCSS compared to 84.27 ± 146.5 µU/l in the lowest (p = 0.012). eGCSS was positively correlated with ACR (p < 0.01), with ACR 7.37 ± 15.29 vs. 1.25 ± 1.52 g/mol for the highest vs. lowest tertiles of eGCSS (p < 0.05). eGCSS was not correlated with other clinical characteristics or biochemical measures. These results suggests that sodium retention in hypertension characterised by a low-renin state is associated with cell membrane damage reflected by eGCSS. This may contribute to the hypertension-mediated organ damage and the excess mortality associated with sodium overload and "salt sensitivity".

Effect of diuretics on plasma aldosterone and potassium in primary hypertension: A systematic review and meta-analysis

AIM

By contrast with drugs inhibiting the renin-angiotensin-aldosterone system (RAAS), diuretics stimulate renin release by the kidneys. Although plasma aldosterone (PA) is thought to be mainly regulated by RAAS activity, serum potassium has been shown to be an important factor in animal models and humans. Here we perform a systematic review and meta-analysis of randomised controlled trials (RCT) in hypertension investigating the effects of diuretic therapy on PA and the correlation of change in PA with that of potassium and blood pressure (BP).

METHODS

Three databases were searched: MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials (CENTRAL). Titles were first screened by title and abstract for relevance before full-text articles were assessed for eligibility according to a predefined inclusion/exclusion criteria.

RESULTS

A total of 1139 articles were retrieved, of which 42 met the prespecified inclusion/exclusion criteria. The average standardised difference in mean PA was similar for all classes of diuretic: thiazide/thiazide-like 0.299 (95% confidence interval [CI] 0.150, 0.447), loop 0.927 (0.37, 1.49), MRA/potassium-sparing 0.265 (0.173, 0.357) and combination 0.466 (0.137, 0.796), Q = 6.33, P = .097. In subjects untreated with another antihypertensive, there was a significant relationship between change in PA and change in systolic BP but no relationship with the change in potassium.

CONCLUSION

In RCTs of diuretic therapy in hypertension, there is an increase in PA with all classes of diuretic and no significant between-class heterogeneity. Change in PA is not related with potassium but correlates with the change in BP in subjects untreated with another antihypertensive medication.

Sensitivity and Reproducibility of Inferior Vena Cava Diameter and Superior Vena Cava Flow Velocity Measurements to Changes in Cardiac Preload in Subjects with Hypertension

Objectives

We investigated the sensitivity and reproducibility of inferior vena cava (IVC) diameters and superior vena cava (SVC) flow velocities in detecting changes in cardiac preload in clinically euvolemic subjects with hypertension.

Methods

Measurements were obtained during passive leg raising (PLR) and lower limb venous occlusion (LVO), interventions which respectively transiently increase and decrease cardiac preload. Measurements were made in 36 subjects and repeated on two separate occasions to examine reproducibility.

Results

During PLR, there was no significant change in IVC diameters, but peak flow velocity of the SVC S wave increased by 6.5 (95% confidence interval 1.6-11.3) cm/s (P = 0.01). During LVO, IVC diameter in expiration decreased by 3.2 (1.7-4.7) mm and the SVC S wave decreased by 9.7 (4.4-14.7) cm/s (P < 0.001). Venae cavae-derived indices can be used to assess changes in preload within the physiological range in euvolemia.

Conclusions

Despite suboptimal reproducibility of baseline measurements, high agreeability between the changes in IVC diameter and SVC flow after LVO suggests that these indices can be used to monitor changes in cardiac preload.

Effect of diuretics on plasma renin activity in primary hypertension: A systematic review and meta-analysis

AIMS

Plasma renin activity (PRA) is regarded as a marker of sodium and fluid homeostasis in patients with primary hypertension. Whether effects of diuretics on PRA differ according to class of diuretic, whether diuretics lead to a sustained increase in PRA, and whether changes in PRA relate to those in blood pressure (BP) is unknown. We performed a systematic review and meta-analysis of trials investigating the antihypertensive effects of diuretic therapy in which PRA and/or other biomarkers of fluid homeostasis were measured before and after treatment.

METHODS

Three databases were searched: MEDLINE, EMBASE and The Cochrane Central Register of Controlled Trials. Titles were firstly screened by title and abstract for relevancy before full-text articles were assessed for eligibility according to a predefined inclusion/exclusion criteria.

RESULTS

A total of 1684 articles were retrieved of which 61 met the prespecified inclusion/exclusion criteria. PRA was measured in 30/61 studies. Diuretics led to a sustained increase in PRA which was similar for different classes of diuretic (standardised mean difference [95% confidence interval] 0.481 [0.362, 0.601], 0.729 [0.181, 1.28], 0.541 [0.253, 0.830] and 0.548 [0.159, 0.937] for thiazide, loop, mineralocorticoid receptor antagonists/potassium-sparing and combination diuretics respectively, Q = 0.897, P = .826), and did not relate to the average decrease in blood pressure.

CONCLUSION

In antihypertensive drug trials, diuretics lead to a sustained increase in average PRA, which is similar across different classes of diuretic and unrelated to the average reduction in blood pressure.

Post-exertional increase in first-phase ejection fraction in recreational marathon runners

OBJECTIVES

Running a marathon has been equivocally associated with acute changes in cardiac performance. First-phase ejection fraction is a novel integrated echocardiographic measure of left ventricular contractility and systo-diastolic coupling which has never been studied in the context of physical activity. The aim of this study was to assess first-phase ejection fraction following recreational marathon running along with standard echocardiographic indices of systolic and diastolic function.Design and participants: Runners (n = 25, 17 males), age (mean ± standard deviation) 39 ± 9 years, were assessed before and immediately after a marathon race which was completed in 4 h, 10 min ± 47 min.

MAIN OUTCOME MEASURES

Central hemodynamics were estimated with applanation tonometry; cardiac performance was assessed using standard M-mode two-dimensional Doppler, tissue-doppler imaging and speckle-tracking echocardiography. First-phase ejection fraction was calculated as the percentage change in left ventricular volume from end-diastole to the time of peak aortic blood flow.

RESULTS

Conventional indices of systolic function and cardiac performance were similar pre- and post-race while aortic systolic blood pressure decreased by 9 ± 8 mmHg (P < 0.001) and first-phase ejection fraction increased by approximately 48% from 16.3 ± 3.9% to 22.9 ± 2.5% (P < 0.001). The ratio of left ventricular transmitral Doppler early velocity (E) to tissue-doppler imaging early annular velocity (e') increased from 5.1 ± 1.8 to 6.2 ± 1.3 (P < 0.01).

CONCLUSION

In recreational marathon runners, there is a marked increase in first-phase ejection fraction after the race despite no other significant change in cardiac performance or conventional measure of systolic function. More detailed physiological studies are required to elucidate the mechanism of this increase.

A review of the prescribing trend of thiazide-type and thiazide-like diuretics in hypertension: A UK perspective

Thiazide diuretics have been the cornerstone of hypertension treatment for >5 decades. Most recent European and American guidelines recommend both thiazide-type and thiazide-like diuretics as first-line drugs for all patients with hypertension. In contrast, diuretics are not regarded as first-line treatment in the UK and in patients who are to be initiated on a diuretic treatment, thiazide-like molecules, such as chlortalidone and indapamide are the preferred option. This review examines the prescribing trend of the 4 most commonly prescribed thiazide diuretics for the treatment of hypertension in the UK. Prescription cost analysis data were obtained for both 2010 and 2016/2017 for each region of the UK to analyse the impact of the 2011 National Institute for Health and Care Excellence hypertension guidelines on the trend in thiazide diuretic prescribing. Overall, the prescriptions of thiazide diuretics declined over the years. Bendroflumethiazide is the most commonly prescribed diuretic in the UK and despite some geographical differences, thiazide-type diuretics are more widely used than thiazide-like. The use of indapamide increased significantly between 2010 and 2016/2017 while chlortalidone was rarely employed. Of the many factors affecting trends in prescriptions, clinical inertia, treatment adherence, availability of the products and the lack of fixed dose combinations may play a role.

Influence of mental stress on the pulse wave features of photoplethysmograms

Mental stress is a major burden for our society. Invasive and non-invasive methods have been proposed to monitor and quantify it using various sensors on and off body. In this Letter, the authors investigated the use of the arm photoplethysmogram (PPG) to assess mental stress in laboratory conditions. Results were in correspondence with their previous in-silico study which guided the present study. Three wave shape parameters were identified for stress assessment from the PPG signal: (i) the time from dicrotic notch to end diastole; (ii) the time from pulse onset to systolic peak; and (iii) the ratio of diastolic to systolic area. The proposed in-vivo results showed that the two first parameters responded significantly to increased mental stress and to a breathing relaxation procedure, complementing heart rate, heart rate variability, and pulse transit time as indices of stress.

Arterial Stiffness Can Be Modulated by Pressure-Independent Mechanisms in Hypertension

Background Effects of short-term interventions on large-artery stiffness assessed by pulse wave velocity (PWV) have mainly been explained by concomitant changes in blood pressure (BP). However, lower body negative pressure, which increases sympathetic activity and has other hemodynamic effects, has a specific effect on PWV in healthy volunteers. Methods and Results We examined effects of lower-limb venous occlusion (LVO), a similar intervention to lower-body negative pressure that reduces BP but increases sympathetic activity and device-guided breathing (DGB), which reduces both BP and sympathetic activity, on PWV in patients with essential hypertension (n=70 after LVO, n=45 after DGB and LVO in random order). The short-acting calcium channel antagonist nifedipine was used as a control for changes in BP. LVO produced a small but significant reduction in mean arterial pressure of 1.8 (95% CI 0.3-3.4) mm Hg. Despite this, aortic and carotid-femoral PWV increased during LVO by 0.8 (0.2-1.4) m/s and 0.7 (0.3-1.05) m/s, respectively. DGB reduced PWV by 1.2 (0.9-1.4) m/s, to a greater extent than did nifedipine 10 mg (reduction of 0.7 [0.1-1.3] m/s, P<0.05 compared with reduction during DGB). This occurred despite a greater decrease in BP with nifedipine compared with DGB. Conclusions Arterial stiffness can be modulated independently of BP over the short term. The mechanism could involve alterations in sympathetic activity or other as yet uncharacterized effects of LVO and DGB.

Why are there ethnic differences in cardio-metabolic risk factors and cardiovascular diseases?

Europe's population is becoming increasingly ethnically diverse, and epidemiological studies indicate that there are remarkable differences in cardio-metabolic risk factors between ethnic groups living in the same area. Variations observed in the distribution of cardiovascular risk factors in these communities may therefore help explain-at least in part-the different burdens on cardiovascular diseases. So far, the underlying pathophysiology leading to ethnic variations in the prevalence of cardio-metabolic risk factors is still poorly understood but it is likely to represent the complex interactions from several innate and environmental factors. Tailored prevention and treatment strategies should therefore be implemented in those "high-risk populations," but data derived from randomized clinical trials are still limited. This article will provide an overview on the role of ethnicity on cardio-metabolic risk factors and cardiovascular diseases, focusing on type 2 diabetes and dyslipidemia based mainly on Dutch and British data.

Abstract P226: Reducing Sympathetic Activity and Cardiac Pre-Load Have Differential Effects on Mean and Pulsatile Blood Pressure Components

Objective: Blood pressure (BP) can be divided into steady state (mean arterial pressure, MAP) and pulsatile (pulse pressure, PP) components that are differentially associated with target organ damage and cardiovascular events. Here, we tested the effects of non-pharmacological interventions that reduce sympathetic activity (SA) and cardiac pre-load on MAP and PP.

Material and Methods: Pulse-wave analysis of the radial artery (SphygmoCor, AtCor Medical, Sydney, Australia), calibrated from 3 consecutive readings of brachial BP, was used for the evaluation of central PP and MAP. Measurements were obtained before and after supervised device-guided paced breathing (DGB), and bilateral lower limb venous occlusion (LVO, performed non-invasively using thigh cuffs), in random order. DGB reduces SA whereas LVO produces an acute reduction in pre-load. High resolution heart rate variability (HRV) as log-ratio of low-frequency/high-frequency range (LF/HF),( Schiller Medilog AR12plus, United States) was used to assess the effects of DGB on SA, while reduction of pre-load was evaluated by inferior vena cava diameter (IVCd) measured with cardiac ultrasound.

Results: Thirty six HT patients (16 female) age (mean±SD) 46±12 years, BP 144.8±17.7/88.2±10.3 mmHg were studied. DGB decreased log LF/HF from 0.306±0.27 to 0.171±0.3 and LVO decreased IVCd from 15.16±3.96 mm to 12.39±3.43mm. Reduction of brachial BP was greater during DGB compared to LVO: (mean (95% confidence interval)):-9.7(-11.6,-7.8) mmHg vs -3.8(-5.8,-1.7) mmHg for systolic BP and -4.1(-5.6,-2.5) mmHg vs 1.1(-0.1, 2.2) mmHg for diastolic BP, respectively ( P<0.05) . Effects of DGB and LVO were similar on PP: -3.5(-4.8,-2.3) mmHg for DBG and -3.1(-5.5,-0.7) mmHg for LVO, P>0.1. MAP reduction was significant only during DBG (-6.4 (-8.1,-4.7) mmHg) compared to LVO (-1.2 (-2.7, 0.1) mmHg, P<0.01 between the interventions.

Conclusion: Reducing sympathetic activity via DGB decreases both steady state and pulsatile components of BP whereas pre-load reduction selectively decreases PP. Depending on individual BP components, interventions targeting sympathetic activity and/or pre-load might be used to personalized treatment.

Assessing mental stress from the photoplethysmogram: a numerical study

OBJECTIVE

Mental stress is detrimental to cardiovascular health, being a risk factor for coronary heart disease and a trigger for cardiac events. However, it is not currently routinely assessed. The aim of this study was to identify features of the photoplethysmogram (PPG) pulse wave which are indicative of mental stress.

APPROACH

A numerical model of pulse wave propagation was used to simulate blood pressure signals, from which simulated PPG pulse waves were estimated using a transfer function. Pulse waves were simulated at six levels of stress by changing the model input parameters both simultaneously and individually, in accordance with haemodynamic changes associated with stress. Thirty-two feature measurements were extracted from pulse waves at three measurement sites: the brachial, radial and temporal arteries. Features which changed significantly with stress were identified using the Mann-Kendall monotonic trend test.

MAIN RESULTS

Seventeen features exhibited significant trends with stress in measurements from at least one site. Three features showed significant trends at all three sites: the time from pulse onset to peak, the time from the dicrotic notch to pulse end, and the pulse rate. More features showed significant trends at the radial artery (15) than the brachial (8) or temporal (7) arteries. Most features were influenced by multiple input parameters.

SIGNIFICANCE

The features identified in this study could be used to monitor stress in healthcare and consumer devices. Measurements at the radial artery may provide superior performance than the brachial or temporal arteries. In vivo studies are required to confirm these observations.