High dose angiotensin-converting enzyme inhibition prevents fluid volume expansion in heart transplant recipients

Angiotensin-converting enzyme inhibitor therapy after heart transplant: from molecular basis to clinical effects

The use of angiotensin-converting enzyme inhibitors is an important therapy for various cardiovascular diseases, such as hypertension, ischemic heart disease and heart failure. In heart transplant recipients, angiotensin-converting enzyme inhibitors have been demonstrated to be a keystone for the treatment of hypertension with a wide spectrum of pleiotropic molecular effects ranging from improvement of the peripheral vascular system to regulation of the fluid and sodium balance. In addition, angiotensin-converting enzyme inhibitors may be also useful in the prevention of graft failure, cardiac allograft vasculopathy and chronic kidney disease progression. Further tailored multi-center and randomized studies are warranted to confirm the pleiotropic clinical effects of ACEi therapy in HTRs and to support more extended use in daily clinical practice. Finally in the near future, the use of novel pharmacological agents that inhibit the renin-angiotensin-aldosterone system such as the neprylisin inhibitor sacubitril should be investigated in heart transplant recipients. This article is protected by copyright. All rights reserved.

Blood volume and hemoglobin mass in long-term heart transplant recipients with and without Anemia

BACKGROUND

In systolic chronic heart failure, a heterogeneous blood volume (BV) regulation can be found with plasma volume expansion in many cases, possibly leading to pseudoanemia. Little is known about the volume status after heart transplantation (HTX). So far, anemia of HTX recipients was solely investigated using hemoglobin-concentration that may be misleading in a clinical context. The objective of the study was whether a difference in plasma volume and red cell volume can be observed in clinically stable heart transplant recipients compared to matched control subjects. Secondary, the aim was to describe anemia in the long-term after HTX based on quantitative data.

METHODS

Blood volume and its constituents red cell volume and plasma volume were quantified using an abbreviated carbon monoxide rebreathing method (aCORM) with focus on its primary measure total hemoglobin mass (Hbmass) and coincidental anemia in 36 (7 women) heart transplant recipients. For comparison, a matched control group of 46 (5 women) healthy subjects was selected.

RESULTS

Neither Hbmass nor blood volumes were significantly different in HTX patients compared to matched healthy control group subjects. The prevalence of anemia 6.3 ± 4.3 years after transplantation was 19%. Hbmass and red cell volume were significantly lower in anemic HTX patients compared to non-anemic patients while plasma volume was not expanded. Various immunosuppressant regimens did not have an effect on Hbmass, plasma volume or red cell volume.

CONCLUSIONS

There was no difference in blood volumes and Hbmass between HTX patients and control subjects. The pathophysiologic blood volume regulation in chronic heart failure does not seem to be longer active in long-term HTX recipients. However, in the long-term after HTX, anemia occurs in a considerable number of patients as true anemia without a clear association with immunosuppression.

TRIAL REGISTRATION

German registry for clinical studies, DRKS00006078. Registered 09 May 2014, https://www.drks.de/drks_web/navigate.do?navigationId=trial . HTML&TRIAL_ID=DRKS00006078.

Pathophysiology of Hypertension: The Mosaic Theory and Beyond

Dr Irvine Page proposed the Mosaic Theory of Hypertension in the 1940s advocating that hypertension is the result of many factors that interact to raise blood pressure and cause end-organ damage. Over the years, Dr Page modified his paradigm, and new concepts regarding oxidative stress, inflammation, genetics, sodium homeostasis, and the microbiome have arisen that allow further refinements of the Mosaic Theory. A constant feature of this approach to understanding hypertension is that the various nodes are interdependent and that these almost certainly vary between experimental models and between individuals with hypertension. This review discusses these new concepts and provides an introduction to other reviews in this compendium of Circulation Research.

The detection of coronary stiffness in cardiac allografts using MR imaging

OBJECTIVE

To test the hypothesis that biomechanical changes are quantitatively related to morphological features of coronary arteries in heart transplant (HTx) recipients.

MATERIALS AND METHODS

With IRB approval, three-dimensional (3D) magnetic resonance (MR) angiography and two-dimensional (2D) black-blood stead-state free precession (SSFP) MR imaging were performed to image coronary arteries of 36 HTx patients. Contours of coronary wall were manually drawn. For each coronary segment, coronary wall thickness, wall area, lumen area (in systole and diastole) were acquired. Coronary distensibility index (CDI) and the percent of the coronary wall occupying the vessel area (PWOV) were calculated.

RESULTS

There are totally 98 coronary segments eligible for quantitative analysis from 27 HTx patients. The CDI is 4.90 ± 2.44 mmHg(-1). The mean wall thickness is 1.49 ± 0.24 mm and the PWOV is 74.6% ± 7.5%. CDI has moderate correlations with wall thickness (r=-0.531, P<0.001) and with PWOV (R=-0.435, P<0.001).

CONCLUSIONS

Detected with coronary MR imaging, CDI is quantitatively correlated with the morphological features of the coronary artery in HTx patients. Coronary stiffness has the potential to become an alternative imaging biomarker for the quantitative assessment of the status of cardiac allografts.

The usefulness of chronic heart failure treatments in chronic cardiac graft failure

Following cardiac transplantation, registry data has demonstrated a gradual improvement in survival over the last several decades, which is testament to continual improvement in aftercare strategy. However, a significant number of patients will eventually develop a new syndrome of chronic heart failure, owing to the multitude of physiological processes that occur after transplantation. This condition, referred to as chronic graft failure (CGF) should be regarded as a unique illness rather than one that is simply analogous with chronic heart failure. In particular, the unique pathophysiological (and pharmacological) environment in the setting of CGF presents a challenging situation to the transplant physician. There is uncertainty over which treatments to offer given a paucity of clinical trial data to support the use of standard heart failure treatments in CGF. In this review, we discuss which chronic heart failure treatments could be considered in the setting of CGF based on their mechanisms of action, benefits within the native heart failure setting, and the relevant issues within the posttransplant environment.

Kidney disease after heart and lung transplantation

Kidney disease is a commonly recognized complication of heart and lung transplantation and is associated with increased morbidity and mortality. While the spectrum of kidney disease in this population is wide-ranging, studies indicate that between 3% and 10% of these patients will ultimately develop end-stage renal disease (ESRD). This review examines the risk factors for both acute and chronic kidney injury, with a particular emphasis on the role of calcineurin inhibitor-mediated nephrotoxicity in both these settings. Against the background of current National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines, we have further considered and recommended appropriate strategies for long-term management of kidney disease-related manifestations in heart and lung transplant recipients. Specific aspects addressed include retarding progressive renal injury and minimizing nephrotoxicity, as well as treatment of hypertension, hyperlipidemia and anemia. Finally, for patients in this population with advanced kidney disease, renal replacement therapy options are discussed. Based on the impact of chronic kidney disease on outcomes in both heart and lung recipients, we advocate early referral to a nephrologist for patients displaying evidence of significant renal dysfunction.

High-dose angiotensin-converting enzyme inhibition restores body fluid homeostasis in heart-transplant recipients

OBJECTIVES

We tested the hypothesis that salt and fluid retention in heart-transplant recipients (HTRs) is caused by a failure to reflexively suppress the renin-angiotensin-aldosterone system (RAAS).

BACKGROUND

It is known that extracellular fluid volume is expanded (12% to 15%) in HTRs who develop hypertension.

METHODS

Responses to volume expansion were measured in eight HTRs (ages 57 +/- 6 years) and six liver-transplant recipients (LTRs) (ages 52 +/- 2 years) both before and after treatment with captopril (225 mg/day). After three days of a standardized diet, 0.154 mol/l saline was infused at 8 ml/kg/h for 4 h. Blood pressure, hormones, and renal function were monitored for 48 h. After four months, the same subjects received captopril (225 mg/day), and the protocol was repeated.

RESULTS

Before captopril, saline infusion suppressed the RAAS in LTRs but not in HTRs, resulting in elimination of 86 +/- 12% versus 50 +/- 11% of the sodium load by 48-h postinfusion. Blood pressure increased only in the HTRs (+16 +/- 5/9 +/- 3 mm Hg) and remained elevated for 48 h (p < or = 0.05). After captopril, sodium elimination was comparable in the liver (87 +/- 13%) and heart groups (86 +/- 12%) and blood pressure did not change in either group. CONCLUSIONS; Heart transplant recipients have blunted diuretic and natriuretic responses to volume expansion that is mediated by their inability to suppress the RAAS. Pharmacologic suppression of the RAAS normalized defects in blood pressure and fluid homeostasis. These findings indicate that hypertension in HTRs is caused, in part, by a failure to reflexively suppress the RAAS when these patients become hypervolemic.