Renal infarction is associated with acute kidney injury in patients with cardiac amyloidosis

Systemic amyloidosis is a major cause of renal injury, mostly due to direct kidney damage caused by deposits of abnormal protein called amyloid, in the kidney parenchyma. In patients with cardiac amyloidosis, renal infarction is associated with acute kidney injury according to a new study in Mayo Clinic Proceedings, published by Elsevier. Investigators recommend that a diagnosis of renal infarction should be systematically considered in patients with unexplained acute kidney injury in the context of cardiac amyloidosis.

Amyloidosis is a heterogeneous group of diseases, classified according to the main precursor protein forming the amyloid fibrils. The most prevalent types are acquired systemic immunoglobulin light chain amyloidosis (AL amyloidosis); circulating acute-phase reactant serum amyloid A protein amyloidosis (AA amyloidosis); non-mutated or wild-type transthyretin amyloidosis; and hereditary forms caused by genetic variants which encode abnormal proteins. Cardiac involvement (the most relevant prognosis factor) is increasingly being diagnosed in these patients and is frequently accompanied by significant dysfunction of other major organs. Amyloid cardiomyopathy may be associated with thromboembolic events, mostly due to atrial fibrillation, leading to intracardiac thrombus formation, or promoted by the hypercoagulability state observed in patients with nephrotic syndrome.

“The prevalence of renal infarction and the risk factors for this condition have never before been assessed in this patient population,” explained lead investigator Vincent Audard, MD, PhD, Service de Néphrologie et Transplantation, Groupe Hospitalier Henri Mondor-Albert Chenevier, Université Paris Est Créteil, Créteil, France. “Computed tomography scans and magnetic resonance imaging are the gold standard method for confirming renal infarction but may be unsuitable in patients with systemic amyloidosis because these patients frequently exhibit impaired renal function and/or have heart devices.”

In this observational study, investigators at the Amyloidosis Referral Center of Henri Mondor Hospital assessed the frequency of renal infarction in 87 patients with confirmed cardiac amyloidosis who underwent ^99mTc-labeled DMSA renal scintigraphy from October 1, 2015, through February 28, 2018. Three groups of patients were defined on the basis of the underlying amyloidosis disorder: AL amyloidosis in 24 patients; mutated-transthyretin amyloidosis in 24 patients; and wild-type transthyretin amyloidosis in 39 patients.

One of the study’s most significant findings is that acute kidney injury in a context of cardiac amyloidosis may be due to renal infarction. The prevalence of renal infarction was relatively high (20.7 percent) among the 87 patients with a definitive diagnosis of confirmed cardiac amyloidosis. These cases were evenly distributed between the three groups. At the time of renal scintigraphy, the frequency of acute kidney injury was higher in patients with renal infarction, and the likelihood of renal infarction diagnosis according to the presence or absence of acute kidney injury was 47.1 percent and 14.5 percent, respectively.

The investigators suggest that several factors, including direct kidney damage due to deposits of amyloid and indirect mechanisms of damage, such as renal failure due to low cardiac output, may be involved in the renal failure observed in these patients.

This study showed that after excluding heart transplant cases, patient survival did not differ significantly between patients with and without a diagnosis of renal infarction. By contrast, the authors found that death- and heart transplant—censored renal survival was significantly lower in patients with renal infarction.

“Overall, these data suggest that renal infarction should probably be added to the spectrum of renal manifestations related to systemic amyloidosis in cases of heart involvement,” concluded Dr. Audard. “We recommend that a diagnosis of renal infarction should be systematically considered in patients with unexplained acute kidney injury in the context of cardiac amyloidosis.”

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The article is “Renal Infarction and Its Consequences for Renal Function in Patients With Cardiac Amyloidosis,” by Julien Dang, MD; Mukedaisi Abulizi, MD; Anissa Moktefi, MD; Khalil El Karoui, MD, PhD; Jean-François Deux, MD, PhD; Diane Bodez, MD, PhD; Fabien Le Bras, MD; Karim Belhadj, MD; Philippe Remy, MD; Pauline Issaurat, MD; Violaine Plante-Bordeneuve, MD, PhD; Valérie Molinier-Frenkel, MD, PhD; Pascale Fanen, MD, PhD; Soulef Guendouz, MD; Mounira Kharoubi, PhD; Emmanuel Itti, MD, PhD; Thibaud Damy, MD, PhD; and Vincent Audard, MD, PhD (https://doi.org/10.1016/j.mayocp.2019.02.012). It appears in Mayo Clinic Proceedings, volume 94, issue 6 (June 2019) published by Elsevier.

About Mayo Clinic Proceedings
The flagship journal of Mayo Clinic and one of the premier peer-reviewed clinical journals in general medicine, Mayo Clinic Proceedings is among the most widely read and highly cited scientific publications for physicians, with a circulation of approximately 125,000. While the Journal is sponsored by Mayo Clinic, it welcomes submissions from authors worldwide, publishing articles that focus on clinical medicine and support the professional and educational needs of its readers. www.mayoclinicproceedings.org

About Mayo Clinic
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About Elsevier
Elsevier is a global information analytics business that helps scientists and clinicians to find new answers, reshape human knowledge, and tackle the most urgent human crises. For 140 years, we have partnered with the research world to curate and verify scientific knowledge. Today, we’re committed to bringing that rigor to a new generation of platforms. Elsevier provides digital solutions and tools in the areas of strategic research management, R&D performance, clinical decision support, and professional education; including ScienceDirect, Scopus, SciVal, ClinicalKey and Sherpath. Elsevier publishes over 2,500 digitized journals, including The Lancet and Cell, 39,000 e-book titles and many iconic reference works, including Gray’s Anatomy. Elsevier is part of RELX Group, a global provider of information and analytics for professionals and business customers across industries. www.elsevier.com