Prognostic implications of residual left ventricular hypertrophy and systolic dysfunction in aortic stenosis following transcatheter aortic valve replacement

The impact of left ventricle (LV) hypertrophy (LVH) regression on contractility-associated measures, the extent of residual cardiac dysfunction and prognostic implications after the initial remodeling process after transcatheter aortic valve replacement (TAVR) has not been investigated. We aimed to assess whether greater LV mass regression from pre-TAVR to 12-months after TAVR was associated with increased systolic function; and assess the prognostic value of residual LVH, systolic function and contractility-associated measures 12-months after TAVR. A total of 439 symptomatic patients were included and examined by echocardiography. LVH regression was assessed as percentage change in LV mass index (LVMi) from baseline to 12-months after TAVR. Midwall fractional shortening (mFS) and stress-corrected (SC-mFS) were used as contractility-associated measures. Primary outcome was all-cause mortality. SC-mFS increased from 0.94 (0.7) at baseline (BS) to 1.22 (0.7) (p < 0.05) 12-months after TAVR for patients with the most LVH regression, compared to patients with no LV regression (BS 1.06 (0.7) to 1.04 (0.5), NS). At 12-months after TAVR, multivariate analysis showed independent prognostic value of LVEF < 50% or GLS < 15% (HR 1.59, p = 0.049) and mFS < 14% (HR 1.99, p = 0.002) for future all cause death. LVH regression in AS after TAVR is associated with significant improvements of LV systolic function in contrast to patients without LV regression. Residual LVH and subsequent LV systolic dysfunction is substantial 12 months after TAVR and are associated with reduced survival. Impaired mFS and the combination of abnormal LVEF or GLS independently predicted all-cause mortality beyond 12 months after TAVR.

A systematic approach to weaning from extracorporeal membrane oxygenation in patients with refractory cardiac failure

BACKGROUND

Veno-arterial extracorporeal membrane oxygenation (V-A ECMO) is commonly used to provide haemodynamic support for patients with severe cardiac failure. However, timing ECMO weaning remains challenging. We aimed to examine if an integrative weaning approach based on predefined haemodynamic, respiratory and echocardiographic criteria is associated with successful weaning.

METHODS

All patients weaned from ECMO between April 2017 and April 2019 at Aarhus University Hospital, Denmark, were consecutively enrolled. Predefined haemodynamic, respiratory and echocardiographic criteria were assessed before and during ECMO flow reduction. A weaning attempt was commenced in haemodynamic stable patients and patients remaining stable at minimal flow were weaned from ECMO. Comparisons were made between patients who met the criteria for weaning at first attempt and patients who did not meet these criteria. Patients completing a full weaning attempt with no further need for mechanical support within 24 h were defined as successfully weaned.

RESULTS

A total of 38 patients were included in the study, of whom 26 (68%) patients met the criteria for weaning. Among these patients, 25 (96%) could be successfully weaned. Successfully weaned patients were younger and had less need for inotropic support and ECMO duration was shorter. Fulfilling the weaning criteria was associated with successful weaning and both favourable 30-d survival and survival to discharge.

CONCLUSION

An integrative weaning approach based on haemodynamic, respiratory and echocardiographic criteria may strengthen the clinical decision process in predicting successful weaning in patients receiving ECMO for refractory cardiac failure.

Impella CP Implantation during Cardiopulmonary Resuscitation for Cardiac Arrest: A Multicenter Experience

BACKGROUND

Impella CP is a left ventricular pump which may serve as a circulatory support during cardiopulmonary resuscitation (CPR) for cardiac arrest (CA). Nevertheless, the survival rate and factors associated with survival in patients undergoing Impella insertion during CPR for CA are unknown.

METHODS

We performed a retrospective multicenter international registry of patients undergoing Impella insertion during on-going CPR for in- or out-of-hospital CA. We recorded immediate and 30-day survival with and without neurologic impairment using the cerebral performance category score and evaluated the factors associated with survival.

RESULTS

Thirty-five patients had an Impella CP implanted during CPR for CA. Refractory ventricular arrhythmias were the most frequent initial rhythm (65.7%). In total, 65.7% of patients immediately survived. At 30 days, 45.7% of patients were still alive. The 30-day survival rate without neurological impairment was 37.1%. In univariate analysis, survival was associated with both an age < 75 years and a time from arrest to CPR ≤ 5 min (p = 0.035 and p = 0.008, respectively).

CONCLUSIONS

In our multicenter registry, Impella CP insertion during ongoing CPR for CA was associated with a 37.1% rate of 30-day survival without neurological impairment. The factors associated with survival were a young age and a time from arrest to CPR ≤ 5 min.

Distribution and prognostic value of left ventricular global longitudinal strain in elderly patients with symptomatic severe aortic stenosis undergoing transcatheter aortic valve replacement

Aims

The aim of present study was to examine the preoperative prevalence and distribution of impaired left ventricular global longitudinal strain (LVGLS) in elderly patients with symptomatic aortic stenosis (AS) undergoing transcutaneous aortic valve replacement (TAVR) and to determine the predictive value of LVGLS on survival.

Methods

We included 411 patients with symptomatic severe AS treated with TAVR during a 5-year period, where a baseline echocardiography including LVGLS assessment was available.

Results

Mean age was 80.1 ± 7.1 years and aortic valve area (AVA) index 0.4 ± 0.1 cm². 78 patients died during a median follow-up of 762 days. Mean left ventricular ejection fraction (LVEF) was 50 ± 13% and mean LVGLS was − 14.0%. LVEF was preserved in 60% of patients, while impaired LVGLS > − 18% was seen in 75% of the patients. Previous myocardial infarction, LVEF < 50%, LVGLS > − 14%, low gradient AS (< 4.0 m/s), tricuspid regurgitant gradient > 30 mmHg were identified as significant univariate predictors of all-cause mortality. On multivariate analysis LVGLS > − 14% (HR 1.79 [1.02–3.14], p = 0.04) was identified as the only independent variable associated with all-cause mortality. Reduced survival was observed with an impaired LVGLS > − 14% in the total population (p < 0.002) but also in patients with high AS gradient with preserved LVEF. LVGLS provided incremental prognostic value with respect to clinical characteristics, AVA and LVEF (χ² 19.9, p = 0.006).

Conclusions

In patients with symptomatic AS undergoing TAVR, impaired LVGLS was highly prevalent despite preserved LVEF. LVGLS > − 14% was an independent predictor of all-cause mortality, and survival was reduced if LVGLS > − 14%.

Prevalence of hereditary transthyretin cardiac amyloidosis (mATTR) in Western Denmark

Purpose

To investigate the prevalence of mATTR in a cohort of consecutive ATTR patients in a tertiary Danish Amyloidosis Center.

Methods

Consecutive patients in the period from 2001 to 2019 with a definite diagnosis of ATTR-CA or ATTR-FAP based on either 99-Tc-DPD-scintigraphy, or transthyretin deposition in the myocardium or fatty tissue proved by immunohistology or protein mass spectrometry underwent testing for exonic genetic TTR variants. The distributions of age at time of diagnosis of mATTR and wildtype ATTR (wtATTR) are described by mean age, standard deviations, and range.

Results

Seventy-four caucasian patients of Danish ancestry except one (Swedish) with ATTR were included (72 ATTR-CA, 2 ATTR-FAP). TTR missense variants were present in 13.5% (10/74) of ATTR patients concluded to have mATTR: c.148G&gt;A/p.Val50Met, n=1; c.187C&gt;T/p.Pro63Ser, n=1; c.193G&gt;T/p.Ala65Ser, n=2; c.218G&gt;C; p.Gly73Ala, n=1; c.391C&gt;A/p.Leu131Met, n=3; c.424G&gt;A/p.Val142Ile, n=2.

The mean age of mATTR patients was 57.6 years ±13.0, range 37.1–71.3 years, and was significantly lower than mean age for wtATTR patients: 79.4 years ±5.5, range 65.7–90.2 years, p=0.0004 (Welch's two-sample t-test with unequal variances). All patients with mATTR had familial disease proven by clinical phenotyping of family members or had a positive family history with heart failure and pacemaker use.

Conclusion

A minority of Danish patients (10–15%) with ATTR have mATTR. These mATTR patients are characterised by a significantly younger age at time of diagnosis than wtATTR patients. This observation indicates that TTR gene test may not be necessary in ATTR in patients older than 75 years. For the first time, the p.Val142Ile TTR variant, associated with mATTR and prevalent in 4% of African-Americans, was identified in a Danish family with mATTR-CA – a finding that may be explained by a common founder effect.

Funding Acknowledgement

Type of funding source: None

Direct Oral Anticoagulants After Percutaneous Patent Foramen Ovale (PFO) Closure: A Call for Caution

BACKGROUND Transient atrial fibrillation (AF) following percutaneous patent foramen ovale (PFO) closure is common. Anticoagulation therapy should be considered in selected cases of prolonged AF after PFO closure, but guidelines do not provide clear recommendations on indication or choice of anticoagulant therapy for patients with post-procedural AF. CASE REPORT A 45-year-old woman presented with cryptogenic stroke verified by magnetic resonance imaging (MRI). Echocardiography revealed a PFO, which was closed percutaneously using a Gore septal occluder (25 mm). She was discharged on aspirin monotherapy (75 mg oral daily) according to institutional standard. Three weeks later, she presented with atrial fibrillation (AF). A direct oral anticoagulant (DOAC) (rivaroxaban 20 mg once daily) was initiated and aspirin was discontinued. After 4 months of follow-up, a routine echocardiography revealed large thrombi attached to both sides of the PFO occluder. CONCLUSIONS DOACs may be ineffective in preventing thrombus formation on device surfaces. Until more evidence has been provided, we suggest that DOACs are not routinely used for stroke prevention in patients following PFO closure or similar procedures within the first 3 months after device implantation.

479Preoperative global longitudinal strain is the best predictor of mortality following transcatheter aortic valve replacement

Background

Prognosis after transcatheter aortic valve replacement (TAVR) is variable. This might depend on preoperative evaluation of myocardial performance by other measurements than ejection fraction (EF).

Purpose

The aim of this study was to investigate the predictive value of preoperative global longitudinal strain (GLS) and the guidelines specified subtypes of aortic stenosis (AS) on mortality following TAVR.

Methods

We included 511 patients with severe AS who underwent TAVR in the period July 2012–June 2017.

Patients were divided into guidelines-specified subgroups based on EF (EF: ≥50 (NEF) or <50% (LEF)), peak gradient (PG: ≥4 (HG) or <4 m/s (LG)) and flow status (stroke volume index (SVI): ≥35 (NF) or <35 ml/min/kg (LF)): (1) HG-NEF (n=228), (2) HG-LEF (n=91), (3) LG-LF-NEF (n=71) and (4) LG-LF-LEF (n=121). We also investigated the effect of replacing EF by GLS in the guideline specified subgroups (GLS ≤−14 (HGLS) and GLS >−14% (LGLS)).

Results

Mean follow up time was 1033 days. Mean age was 80.2±7.1 years. Median overall survival was 5.3±0.3 years. Comorbidity burden was higher in patients with LF – and LEF status in terms of a higher median plasma creatinine (103 [85; 135], p<0.001) and EurologII score (6.1 [3.4; 9.6], p<0.001).

LG-LF-LEF AS was associated with a significantly worse outcome compared with all other groups (p<0.005, Fig. 1A). High gradient status, irrespective of EF (p=0.88), was associated with the best prognosis with a median survival of 5.0±0.5 and 5.5±0.1 years for NEF and LEF, respectively.

Overall and in patients with HG-NEF, impaired GLS (>−14%) was associated with poor outcome (Fig. 1B–D). There was a trend towards a poorer prognosis with GLS >−14% in LG-LF-NEF AS (p=0.10).

In an univariate analysis impaired GLS >−14% (HR 2.04, p<0.005), LG-LF-LEF status (HR 1.82, p=0.001), PG <4m/s (HR 1.74, p=0.001) and tricuspid regurgitation gradient >30 mmHg (HR 1.63, p<0.001) were significant predictors of mortality in contrast to EF, SVI, age, gender and plasma creatinine.

GLS >−14% emerged as the only significant outcome predictor in a multivariate analysis (HR 1.93, p<0.05).

Figure 1

Conclusion

Impaired global longitudinal strain >−14% was the best individual echocardiographic predictor of overall survival in symptomatic severe AS and could identify a subgroup of patients with HG-NEF AS with a worse prognosis.

Renal denervation in treatment-resistant essential hypertension. A randomized, SHAM-controlled, double-blinded 24-h blood pressure-based trial

BACKGROUND

Renal denervation (RDN), treating resistant hypertension, has, in open trial design, been shown to lower blood pressure (BP) dramatically, but this was primarily with respect to office BP.

METHOD

We conducted a SHAM-controlled, double-blind, randomized, single-center trial to establish efficacy data based on 24-h ambulatory BP measurements (ABPM). Inclusion criteria were daytime systolic ABPM at least 145 mmHg following 1 month of stable medication and 2 weeks of compliance registration. All RDN procedures were carried out by an experienced operator using the unipolar Medtronic Flex catheter (Medtronic, Santa Rosa, California, USA).

RESULTS

We randomized 69 patients with treatment-resistant hypertension to RDN (n = 36) or SHAM (n = 33). Groups were well balanced at baseline. Mean baseline daytime systolic ABPM was 159 ± 12 mmHg (RDN) and 159 ± 14 mmHg (SHAM). Groups had similar reductions in daytime systolic ABPM compared with baseline at 3 months [-6.2 ± 18.8 mmHg (RDN) vs. -6.0 ± 13.5 mmHg (SHAM)] and at 6 months [-6.1 ± 18.9 mmHg (RDN) vs. -4.3 ± 15.1 mmHg (SHAM)]. Mean usage of antihypertensive medication (daily defined doses) at 3 months was equal [6.8 ± 2.7 (RDN) vs. 7.0 ± 2.5 (SHAM)].RDN performed at a single center and by a high-volume operator reduced ABPM to the same level as SHAM treatment and thus confirms the result of the HTN3 trial.

CONCLUSION

Further, clinical use of RDN for treatment of resistant hypertension should await positive results from double-blinded, SHAM-controlled trials with multipolar ablation catheters or novel denervation techniques.

The effect of renal denervation on arterial stiffness, central blood pressure and heart rate variability in treatment resistant essential hypertension: a substudy of a randomized sham-controlled double-blinded trial (the ReSET trial)

OBJECTIVES

To investigate, whether renal denervation (RDN) improves arterial stiffness, central blood pressure (C-BP) and heart rate variability (HRV) in patients with treatment resistant hypertension.

METHODS

ReSET was a randomized, sham-controlled, double-blinded trial (NCT01459900). RDN was performed by a single experienced operator using the Medtronic unipolar Symplicity Flex^TM catheter. C-BP, carotid-femoral pulse wave velocity (PWV), and HRV were obtained at baseline and after six months with the SphygmoCor^®-device.

RESULTS

Fifty-three patients (77% of the ReSET-cohort) were included in this substudy. The groups were similar at baseline (SHAM/RDN): n = 27/n = 26; 78/65% males; age 59 ± 9/54 ± 8 years (mean ± SD); systolic brachial BP 158 ± 18/154 ± 17 mmHg; systolic 24-hour ambulatory BP 153 ± 14/151 ± 13 mmHg. Changes in PWV (0.1 ± 1.9 (SHAM) vs. -0.6 ± 1.3 (RDN) m/s), systolic C-BP (-2 ± 17 (SHAM) vs. -8 ± 16 (RDN) mmHg), diastolic C-BP (-2 ± 9 (SHAM) vs. -5 ± 9 (RDN) mmHg), and augmentation index (0.7 ± 7.0 (SHAM) vs. 1.0 ± 7.4 (RDN) %) were not significantly different after six months. Changes in HRV-parameters were also not significantly different. Baseline HRV or PWV did not predict BP-response after RDN.

CONCLUSIONS

In a sham-controlled setting, there were no significant effects of RDN on arterial stiffness, C-BP and HRV. Thus, the idea of BP-independent effects of RDN on large arteries and cardiac autonomic activity is not supported.

Effects of Renal Denervation on Insulin Sensitivity and Inflammatory Markers in Nondiabetic Patients with Treatment-Resistant Hypertension

Increased sympathetic activity is important in the pathogenesis of hypertension and insulin resistance. Afferent signaling from the kidneys elevates the central sympathetic drive. We investigated the effect of catheter-based renal sympathetic denervation (RDN) on glucose metabolism, inflammatory markers, and blood pressure in nondiabetic patients with treatment-resistant hypertension. Eight subjects were included in an open-labelled study. Each patient was studied before and 6 months after RDN. Endogenous glucose production was assessed by a 3-³H glucose tracer, insulin sensitivity was examined by hyperinsulinemic euglycemic clamp, hormones and inflammatory markers were analyzed, and blood pressure was measured by office blood pressure readings and 24-hour ambulatory blood pressure monitoring. Insulin sensitivity (M-value) increased nonsignificantly from 2.68 ± 0.28 to 3.07 ± 0.41 (p = 0.12). A significant inverse correlation between the increase in M-value and BMI 6 months after RDN (p = 0.03) was found, suggesting beneficial effects on leaner subjects. Blood pressure decreased significantly, but there were no changes in hormones, inflammatory markers, or endogenous glucose production. Our results indicate that RDN may improve insulin sensitivity in some patients with treatment-resistant hypertension, albeit confirmation of these indications of beneficial effects on leaner subjects awaits the outcome of larger randomized controlled studies.

Rotigaptide protects the myocardium and arterial vasculature from ischaemia reperfusion injury

AIM

Ischaemia-reperfusion injury (IRI) causes impaired endothelial function and is a major component of the adverse effects of reperfusion following myocardial infarction. Rotigaptide increases gap junction conductance via connexin-43. We tested the hypothesis that rotigaptide reduces experimental myocardial infarction size and ameliorates endothelial IRI in humans.

METHODS

Myocardial infarction study: porcine myocardial infarction was achieved by catheter-induced occlusion of the left anterior descending artery. In a randomized double-blind study, rotigaptide (n = 9) or placebo (n = 10) was administered intravenously as a 10 min bolus prior to reperfusion and continuously during 2 h of reperfusion. Myocardial infarction size (IS) was assessed as proportion of the area at risk (AAR). Human translational study: forearm IRI was induced in the presence or absence of intra-arterial rotigaptide. In a randomized double-blind study, forearm arterial blood flow was measured at rest and during intra-arterial infusion of acetylcholine (5-20 μg min(-1) ; n = 11) or sodium nitroprusside (2-8 mg min(-1) ; n = 10) before and after intra-arterial infusion of placebo or rotigaptide, and again following IRI.

RESULTS

Myocardial infarction study: Rotigaptide treatment was associated with a reduction of infarct size (IS/AAR[%]: 18.7 ± 4.1 [rotigaptide] vs. 43.6 ± 4.2 [placebo], P = 0.006). Human translational study: Endothelium-dependent vasodilatation to acetylcholine was attenuated after ischaemia-reperfusion in the presence of placebo (P = 0.007), but not in the presence of rotigaptide (P = NS). Endothelium-independent vasodilatation evoked by sodium nitroprusside was unaffected by IRI or rotigaptide (P = NS).

CONCLUSIONS

Rotigaptide reduces myocardial infarction size in a porcine model and protects from IRI-related endothelial dysfunction in man. Rotigaptide may have therapeutic potential in the treatment of myocardial infarction.

[Mechanical circulatory treatment of advanced heart failure]

Heart failure is one of the most common causes of morbidity and mortality worldwide. When patients cease to respond adequately to optimal medical therapy mechanical circulatory support has been promising. The advent of mechanical circulatory support devices has allowed significant improvements in patient survival and quality of life for those with advanced or end-stage heart failure. We provide a general overview of current mechanical circulatory support devices encompassing options for both short- and long-term ventricular support.

Cardiovascular effects of cholecalciferol treatment in dialysis patients--a randomized controlled trial

Background

Patients on chronic dialysis are at increased risk of vitamin D deficiency. In observational studies plasma 25-hydroxyvitamin D (p-25(OH) D) levels are inversely correlated with plasma BNP and adverse cardiovascular outcomes. Whether a causal relation exists has yet to be established. The aim of this study was to test the hypothesis that cholecalciferol supplementation improves cardiac function and reduces blood pressure (BP) and pulse wave velocity (PWV) in patients on chronic dialysis.

Methods

In a randomized, placebo-controlled, double-blind study, we investigated the effect of 75 μg (3000 IU) cholecalciferol daily for 6 months, in patients on chronic dialysis. We performed two-dimensional echocardiography, with doppler and tissue-doppler imaging, 24-h ambulatory BP (24-h BP), PWV, augmentation index (AIx), central BP (cBP) and brain natriuretic peptide (BNP) measurements at baseline and after 6 months.

Results

Sixty-four patients were allocated to the study. Fifty dialysis patients with a mean age of 68 years (range: 46–88) and baseline p-25(OH) D of 28 (20;53) nmol/l completed the trial. Cholecalciferol increased left ventricular (LV) volume, but had no impact on other parameters regarding LV structure or left atrial structure. LV systolic function, LV diastolic function, PWV, cBP, AIx and BNP were not changed in placebo or cholecalciferol group at follow-up. 24-h BP decreased significantly in placebo group and tended to decrease in cholecalciferol group without any difference between treatments.

Conclusion

Six months of cholecalciferol treatment in patients on chronic dialysis did not improve 24-h BP, arterial stiffness or cardiac function.

Trial registration

NCT01312714, Registration Date: March 9, 2011.

Effect of amiloride and spironolactone on renal tubular function and central blood pressure in patients with arterial hypertension during baseline conditions and after furosemide: a double-blinded, randomized, placebo-controlled crossover trial

This study demonstrates that the increased potassium content in the body seems to change both the blood pressure and renal tubular function. We wanted to test the hypotheses that amiloride and spironolactone induced potassium retention reduces ambulatory blood pressure (ABP) and central blood pressure (CBP) during baseline conditions and after furosemide and that the tubular transport via the epithelial sodium channels (ENaCs) and aquaporin-2 (AQP2) water channels was increased by furosemide in arterial hypertension. Each of three 28-day treatment periods (placebo, amiloride, and spironolactone) was completed by a 4-day period with standardized diet regarding calories and sodium and water intake. At the end of each period, we measured pulse wave velocity (PWV), central systolic blood pressure (CSBP), central diastolic blood pressure (CDBP), glomerular filtration rate (GFR), free water clearance (CH2O), fractional excretion of sodium (FENa) and potassium (FEK), urinary excretion of AQP2 (u-AQP2), urinary excretion of γ-fraction of the ENaC (u-ENaCγ), and plasma concentrations of renin (PRC), angiotensin II (p-Ang II), and aldosterone (p-Aldo) at baseline conditions and after furosemide bolus. Ambulatory blood pressure and CBP were significantly lowered by amiloride and spironolactone. During 24-hour urine collection and at baseline, GFR, CH2O, FENa, FEK, u-AQP2 and u-ENaCγ were the same. After furosemide, CH2O, FENa, FEK, u-AQP2, u-ENaCγ, PRC, p-Ang II, p-Aldo, PWV and CDBP increased after all treatments. However, during amiloride treatment, FEK increased to a larger extent than after spironolactone and during placebo after furosemide, and CSBP was not significantly reduced. The increases in water and sodium absorption via AQP2 and ENaC after furosemide most likely are compensatory phenomena to antagonize water and sodium depletion. Amiloride is less effective than spironolactone to reduce renal potassium excretion.

Catheter-based renal denervation for treatment of resistant hypertension

INTRODUCTION

Activation of renal sympathetic nerves is associated with the development of hypertension. Catheter-based renal sympathetic denervation with radiofrequency energy ablation is a new promising treatment option for resistant hypertension. We here report the first Danish experiences and results with this technique.

MATERIAL AND METHODS

Nine patients with resistant hypertension and a day-time 24-hour ambulatory blood pressure (BP) of 152/89 mmHg ± 10/10 (standard deviation) mmHg despite treatment with 5.4 ± 1.4 anti-hypertensive drugs underwent catheter-based renal sympathetic denervation with the Symplicity catheter.

RESULTS

No periprocedural complications or adverse events during follow-up were observed. Seven patients received complete ablation and two patients only partial ablation. Five patients responded to the treatment with a reduction in day-time 24-hour ambulatory BP from 158/94 ± 13/9 mmHg to 139/82 ± 10/8 mmHg (p < 0.05) at the one month follow-up and a reduction in the number of anti-hypertensive drugs from 5.4 ± 1.6 to 3.4 ± 0.9 (p < 0.05). BP in the remaining four patients was not significantly changed and antihypertensive therapy was not changed.

CONCLUSION

Catheter-based renal sympathetic denervation is a feasible and in several cases also effective treatment option for patients with resistant hypertension. Adequately designed controlled trials are needed to assess the long-term safety and the full potential of this treatment.

Abnormal increase in urinary aquaporin-2 excretion in response to hypertonic saline in essential hypertension

Background

Dysregulation of the expression/shuttling of the aquaporin-2 water channel (AQP2) and the epithelial sodium channel (ENaC) in renal collecting duct principal cells has been found in animal models of hypertension. We tested whether a similar dysregulation exists in essential hypertension.

Methods

We measured urinary excretion of AQP2 and ENaC β-subunit corrected for creatinine (u-AQP2_CR, u-ENaC_β-CR), prostaglandin E2 (u-PGE₂) and cyclic AMP (u-cAMP), fractional sodium excretion (FE_Na), free water clearance (C_H2O), as well as plasma concentrations of vasopressin (AVP), renin (PRC), angiotensin II (Ang II), aldosterone (Aldo), and atrial and brain natriuretic peptide (ANP, BNP) in 21 patients with essential hypertension and 20 normotensive controls during 24-h urine collection (baseline), and after hypertonic saline infusion on a 4-day high sodium (HS) diet (300 mmol sodium/day) and a 4-day low sodium (LS) diet (30 mmol sodium/day).

Results

At baseline, no differences in u-AQP2_CR or u-ENaC_β-CR were measured between patients and controls. U-AQP2_CR increased significantly more after saline in patients than controls, whereas u-ENaC_β-CR increased similarly. The saline caused exaggerated natriuretic increases in patients during HS intake. Neither baseline levels of u-PGE₂, u-cAMP, AVP, PRC, Ang II, Aldo, ANP, and BNP nor changes after saline could explain the abnormal u-AQP2_CR response.

Conclusions

No differences were found in u-AQP2_CR and u-ENaC_β-CR between patients and controls at baseline. However, in response to saline, u-AQP2_CR was abnormally increased in patients, whereas the u-ENaC_β-CR response was normal. The mechanism behind the abnormal AQP2 regulation is not clarified, but it does not seem to be AVP-dependent.

Clinicaltrial.gov identifier

NCT00345124.

Effect of potassium supplementation on renal tubular function, ambulatory blood pressure and pulse wave velocity in healthy humans

BACKGROUND

Potassium is the main intracellular cation, which contributes to keeping the intracellular membrane potential slightly negative and elicits contraction of smooth, skeletal and cardiac muscle. A change in potassium intake modifies both cardiovascular and renal tubular function. The purpose of the trial was to investigate the effect of dietary potassium supplementation, 100 mmol daily in a randomized, placebo-controlled, crossover trial of healthy participants during two periods of 28 days duration. The participants (N = 21) received a diet that was standardized regarding energy requirement, and sodium and water intake.

METHODS

24-hour ambulatory blood pressure (ABP) and applanation tonometry were used to assess blood pressure, pulse wave velocity (PWV), augmentation index (AIx) and central blood pressure (CBP). Immunoassays were used for measurements of plasma concentrations of vasoactive hormones: renin (PRC), angiotensin II (Ang II), aldosterone (Aldo), atrial natriuretic peptide (ANP), vasopressin (AVP), pro-brain natriuretic peptide (pro-BNP),endothelin (Endo), urinary excretions of aquaporin 2 (AQP2), cyclic AMP (cAMP), and the β-fraction of the epithelial sodium channel (ENaC(ß)).

RESULTS

AQP2 excretion increased during potassium supplementation, and free water clearance fell. The changes in urinary potassium excretion and urinary AQP2 excretion were significantly and positively correlated. Aldo increased. GFR, u-ENaC- β, PRC, Ang II, ANP, BNP, Endo, blood pressure and AI were not significantly changed by potassium supplementation, whereas PWV increased slightly.

CONCLUSIONS

Potassium supplementation changed renal tubular function and increased water absorption in the distal part of the nephron. In spite of an increase in aldosterone in plasma, blood pressure remained unchanged after potassium supplementation.

Increased renal sodium absorption by inhibition of prostaglandin synthesis during fasting in healthy man. A possible role of the epithelial sodium channels

BACKGROUND

Treatment with prostaglandin inhibitors can reduce renal function and impair renal water and sodium excretion. We tested the hypotheses that a reduction in prostaglandin synthesis by ibuprofen treatment during fasting decreased renal water and sodium excretion by increased absorption of water and sodium via the aquaporin2 water channels and the epithelial sodium channels.

METHODS

The effect of ibuprofen, 600 mg thrice daily, was measured during fasting in a randomized, placebo-controlled, double-blinded crossover study of 17 healthy humans. The subjects received a standardized diet on day 1, fasted at day 2, and received an IV infusion of 3% NaCl on day 3. The effect variables were urinary excretions of aquaporin2 (u-AQP2), the beta-fraction of the epithelial sodium channel (u-ENaCbeta), cyclic-AMP (u-cAMP), prostaglandin E2 (u-PGE2). Free water clearance (CH2O), fractional excretion of sodium (FENa), and plasma concentrations of vasopressin, angiotensin II, aldosterone, atrial-, and brain natriuretic peptide.

RESULTS

Ibuprofen decreased u-AQP2, u-PGE2, and FENa at all parts of the study. During the same time, ibuprofen significantly increased u-ENaCbeta. Ibuprofen did not change the response in p-AVP, u-c-AMP, urinary output, and free water clearance during any of these periods. Atrial-and brain natriuretic peptide were higher.

CONCLUSION

During inhibition of prostaglandin synthesis, urinary sodium excretion decreased in parallel with an increase in sodium absorption and increase in u-ENaCbeta. U-AQP2 decreased indicating that water transport via AQP2 fell. The vasopressin-c-AMP-axis did not mediate this effect, but it may be a consequence of the changes in the natriuretic peptide system and/or the angiotensin-aldosterone system

TRIAL REGISTRATION

Clinical Trials Identifier: NCT00281762.

Direct effect of methylprednisolone on renal sodium and water transport via the principal cells in the kidney

BACKGROUND

Glucocorticoids influence renal concentrating and diluting ability. We tested the hypothesis that methylprednisolone treatment increased renal water and sodium absorption by increased absorption via the aquaporin-2 (AQP2) water channels and the epithelial sodium channels (ENaCs) respectively.

METHODS

The effect of methylprednisolone was measured during fasting in a randomized, placebo-controlled, single-blinded cross-over study of 15 healthy humans. The subjects received a standardized diet on day 1, fasted on day 2, and received 500 mg methylprednisolone intravenously on day 3. The effect variables were urinary excretions of AQP2 (u-AQP2), urinary excretion of the beta-fraction of the ENaC (u-ENaC(beta)), cAMP (u-cAMP), prostaglandin E(2) (u-PGE(2)), free water clearance (C(H2O)), and fractional excretion of sodium (FE(Na)), and plasma vasopressin (p-AVP), angiotensin II (p-Ang II), aldosterone (p-Aldo), atrial natriuretic peptide (p-ANP), and brain natriuretic peptide (p-BNP).

RESULTS

Methylprednisolone treatment increased u-AQP2, u-ENaC(beta), and p-AVP significantly, but did not change u-cAMP, c(H2O), and FE(Na). P-ANP increased during methylprednisolone treatment, but after the increase in u-AQP2 and u-ENaC(beta). U-PGE(2), p-Ang II, and p-BNP were unchanged. Heart rate increased and diastolic blood pressure fell.

CONCLUSIONS

Methylprednisolone increased u-AQP2 and u-ENaC. Neither the AVP-cAMP axis nor changes in the renin-angiotensin-Aldo system, or the natriuretic peptide system seems to bear a causal relationship with the increase in either u-AQP2 or u-ENaC. Most probably, the effect is mediated via a direct effect of methylprednisolone on the principal cells. The lack of decrease in urinary output and sodium reabsorption most likely can be attributed to the diuretic and natriuretic properties of the increased secretion of ANP.

Protein-enriched diet increases water absorption via the aquaporin-2 water channels in healthy humans

BACKGROUND

According to animal experiments, a protein-enriched diet increased renal absorption of sodium and water. We wanted to test the hypothesis that a protein-enriched diet would increase the expression of the aquaporin-2 water channels and the epithelial sodium channels in the distal part of the nephron using biomarkers for the activity of the two channels.

METHODS

We performed a randomized, placebo controlled crossover study in 13 healthy humans to examine the effect of a protein-enriched diet on renal handling of water and sodium during baseline condition and during hypertonic saline infusion. We measured the effect of the protein-enriched diet on urinary excretions of aquaporin-2 (u-AQP2), the beta-fraction of the epithelial sodium channels (u-ENaC(beta)), free water clearance (C(H2O)), fractional excretion of sodium and vasoactive hormones.

RESULTS

During baseline conditions, u-AQP2 increased, and C(H2O) decreased during the protein-enriched diet, whereas u-ENaC(beta) was unchanged, although the urinary sodium excretion increased. During hypertonic saline infusion, the response in the effect variables did not deviate between protein-enriched and normal diet. Plasma concentrations of angiotensin II and aldosterone increased as well as pulse rate. Vasopressin in plasma was unchanged, and prostaglandin E(2) fell during the protein-enriched diet.

CONCLUSIONS

The protein-enriched diet increased water absorption via an increased transport via the aquaporin-2 water channels. The increased u-AQP2 might be due to a reduced prostaglandin level. The increase in renal sodium excretion seems to be mediated in another part of the nephron than the epithelial sodium channels.

Effects of dihydralazine on renal water and aquaporin-2 excretion in humans

OBJECTIVE

Dihydralazine is a vasodilator that lowers blood pressure, but often also leads to significant water and sodium retention. To characterize the effect of dihydralazine on renal sodium and water handling, we tested the hypothesis that dihydralazine causes water retention parallel with an increase in urinary excretion of aquaporin-2 (u-AQP2) in healthy humans.

MATERIAL AND METHODS

The effect of intravenous infusion of dihydralazine in three doses (3.125 mg, 6.250 mg and 9.375 mg) on urinary AQP2, water and sodium excretion, heart rate (HR), blood pressure (BP) and vasoactive hormones was measured in a randomized, placebo-controlled, double-blind, crossover study in 17 healthy subjects. Glomerular filtration rate (GFR) and renal tubular function were determined with the continuous infusion clearance technique and vasoactive hormones with radioimmunoassays.

RESULTS

Dihydralazine compared to placebo had no impact of u-AQP2 (effect of dihydralazine versus placebo +/-SE) (-0.074+/-0.048 ng/min versus -0.015+/-0.034 ng/min; p = 0.42), despite significant reductions in urine output and free water clearance after 9.375 mg of dihydralazine. Dihydralazine significantly lowered BP and increased HR, plasma levels of angiotensin II and (except after 3.125 mg) atrial natriuretic peptide, while plasma levels of vasopressin, GFR and fractional excretions of sodium and lithium were not significantly changed.

CONCLUSIONS

These findings suggest that dihydralazine increases water re-absorption in the distal tubules, independently of vasopressin and of sodium re-absorption. Furthermore, our study does not support an effect of the sympathetic nervous system, the renin-angiotensin system and the natriuretic peptide system on u-AQP2 regulation.

Eprosartan modulates the reflex activation of the sympathetic nervous system in sodium restricted healthy humans

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

A sympatho-inhibitory effect of ACE-inhibitors and AT(1) receptor antagonists has been widely demonstrated in animal models, but in humans this effect tends only to be present during chronic treatment in conditions with pre-existing high levels of sympathetic activity. Sodium restriction increases renal sympathetic nerve activity and the activity of the renin-angiotensin system and may be a favourable condition to demonstrate sympatho-inhibition as a short-term effect of the AT(1) receptor antagonist eprosartan in healthy humans.

WHAT THIS STUDY ADDS

Results from our study indicate that during sodium restriction eprosartan has a small inhibitory effect on nonbaroreflex mediated activation of the sympathetic nervous system. During arterial baroreflex mediated activation of the sympathetic nervous system this effect is, however, completely overruled by an increased sensitivity of the arterial baroreflex. AIMS To test the hypothesis that eprosartan inhibits both nonbaroreflex and arterial baroreflex mediated activation of the sympathetic nervous system, assessed by renal tubular function, systemic haemodynamics and vasoactive hormones, in sodium restricted healthy humans.

METHODS

The effect of eprosartan on urinary sodium, lithium and water excretion, heart rate (HR), blood pressure and vasoactive hormones was measured before, during and after a cold pressor test (CPT) and sodium nitroprusside (SNP) infusion in a randomized, placebo controlled, double-blind, crossover study in 17 healthy subjects. Glomerular filtration rate and renal tubular function were determined by a continuous infusion clearance technique and vasoactive hormones by radioimmunoassays.

RESULTS

Eprosartan attenuated the impact of the CPT on HR (mean difference from placebo (95% confidence interval) (3.9 (0.7, 7.0) min(-1)) and mean arterial pressure (MAP) (4.7 (0.3, 9.2) mmHg), but no effect of eprosartan was observed on the impact of the CPT on renal tubular function. During a SNP induced reduction in MAP of 10 mmHg eprosartan decreased fractional excretions of sodium (0.46 (0.14, 0.76)%) and lithium (5.1 (2.5, 7.6)%) and tended to increase HR (4.1 (-0.26, 8.4) min(-1)) and plasma concentrations of norepinephrine (33.8 (-5.8, 72.1) pg ml(-1)). CONCLUSIONS; These findings suggest that during mild sodium restriction eprosartan has a small inhibitory effect on nonbaroreflex mediated activation of the sympathetic nervous system. During arterial baroreflex mediated activation of the sympathetic nervous system this effect is, however, completely overruled by an increased sensitivity of the arterial baroreflex.