Hemodialysis Fistulas May Cause Adverse Cardiac Effects
Pilot study reveals AV fistula (shown above) can increase cardiac output and dilation of all heart chambers.
Arteriovenous (AV) fistulas are considered the preferred form of vascular access for hemodialysis, but a new Australian pilot study using magnetic resonance imaging suggests these fistulas can result in adverse cardiovascular (CV) effects.
The study found that elective AV fistula creation in patients with chronic kidney disease (CKD) not yet on hemodialysis is associated with significant increases in left and right atrial and ventricular chamber volumes and left ventricular mass, as well as deterioration in systemic endothelial function.
Such alterations in cardiovascular structure and function may contribute to the poor health outcomes seen in patients with end-stage renal disease, researchers concluded in a report in the International Journal of Nephrology and Renovascular Disease (2014;7:337–345).
A team led by Matthew I. Worthley, MBBS, PhD, of the Royal Adelaide Hospital in Adelaide, South Australia, used cardiovascular magnetic resonance imaging, which they called a “gold standard imaging modality,” to evaluate the impact of AV fistula creation on cardiac and vascular structure and function in 24 patients with stage 5 CKD undergoing AV fistula creation. Patients underwent imaging at baseline and prior to and 6 months after fistula creation.
At follow-up, left ventricular ejection fraction (LVEF) remained unchanged, whereas mean cardiac output increased significantly by 25%, Dr. Worthley's group reported. Results also showed significant 21% and 18% increases in left and right ventricular end-systolic volumes, respectively, significant 11% and 9% increases in left and right atrial area, respectively, and a significant 12.7% increase in left ventricular mass. Endothelial-dependent vasodilatation had decreased significantly at follow-up, from 9% before fistula creation to 3% at 6 months after fistula creation. Fistula formation did not significantly alter aortic distensibility.
The authors wrote that “it is striking than an elective, purposeful medical intervention could cause such widespread maladaptation within the CV system of already high-risk individuals.”
The researchers explained that endothelial dysfunction is a known to be a critical precondition to the development of atherosclerosis and subsequent CV sequelae.
Commenting on the new study, Monnie Wasse, MD, Director of Interventional Nephrology at the Feinberg School of Medicine at Northwestern University in Chicago and Chair of the American Society of Nephrology's Interventional Nephrology Advisory Group, said the study examines an important subject, given the increased prevalence of AV fistula use among HD patients.
“Yet, it remains unclear whether these observed early cardiac adaptations to increased cardiac output attenuate following initiation of hemodialysis and improved volume and blood pressure control,” Dr. Wasse told Renal & Urology News. “Overall, while it remains unclear what impact early cardiac changes have on long-term survival, these findings warrant further investigation.”
The possible adverse cardiovascular effects of AV fistula creation should not dissuade its use, she said, adding that “It is important that a nephrologist individualize vascular access, taking into account a patient's baseline cardiovascular status, among other factors, when recommending a vascular access.”
Previous large studies consistently demonstrate that AV fistula use confers a significant survival benefit over catheter use on both cardiovascular and all-cause mortality, she stated.
Joseph Vassalotti, MD, Chief Medical Officer for the National Kidney Foundation in New York, noted that the study had no control group, so it is unclear whether some of the cardiovascular changes revealed by cardiac MRI resulted from AV fistula creation or the progression of kidney disease. CKD, he noted, is known to be associated with systemic inflammation and endothelial dysfunction with or without an AV fistula.
Dr. Vassalotti said the increased cardiac output is “something we need to pay attention to. That could affect our selection of patients for AV fistulas.” If patients have congestive heart failure or cardiomyopathy, for example, they might not be able to tolerate an AV fistula. “At what level of cardiac output do we start to be concerned?”
Dr. Vassalotti pointed out that a previous study published in Nephrology Dialysis Transplantation (2011;26:3296–3302) came to some different conclusions. For example, the study, which included 43 pre-dialysis patients who underwent AV fistula creation, showed that the fistulas resulted in a sustained decrease in arterial stiffness and an increase in LVEF
The authors of this study concluded that, overall, post-AV fistula adaptations “might be characterized as potentially beneficial in these patients and supports the widespread use of native vascular access, including older or cardiovascular compromised individuals.”