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Circulation. 2019;140:e804–e805. DOI: 10.1161/CIRCULATIONAHA.119.042028 e804 Yogesh N.V. Reddy, MBBS, MSc Karl A. Nath, MBChB Barry A. Borlaug, MD To the Editor: We read with interest the study from Rao and colleagues reporting cardiac changes following arteriovenous fistula ligation in 27 dialysis-independent renal transplant recipients, compared with 27 patients followed without fistula closure.1 All patients underwent cardiac magnetic resonance imaging at baseline and 6-month follow-up. The authors demonstrated reductions in left ventricular volume and mass, left atrial size, and right atrial size following ligation. Furthermore, fistula closure decreased the hyperdynamic circulatory state, with reductions in cardiac output and a trend to reduction in pulmonary artery systolic velocity. Fistula ligation reduced NT-proBNP (N-terminal pro-B-type natriuretic peptide) levels and improved Borg dyspnea scores during 6-minute walk testing.1 We commend the authors on this important contribution. To our knowledge, this is the first randomized trial proving that adverse cardiac remodeling induced by fistula creation may be ameliorated by ligating the fistula.1 The authors focus on remodeling of the left heart, but we wonder about the effects of fistula ligation on the right ventricle (RV). We have previously shown that RV remodeling and dysfunction greatly exceed corresponding changes in the left heart after fistula creation, and it is important to note that those changes correlate strongly with increased mortality and the development of heart failure (HF).2 The right heart tolerates chronic volume loading less effectively than does the left, as evidenced by frequent and greater RV dilation in endurance athletes, who are exposed to intermittent increases in volume loading as a result of training.3 The authors did not report RV volumes or ejection fraction before and after ligation, but we hypothesize that RV volume was also reduced favorably after ligation, potentially with improved RV function. The participants had multiple risk factors for HF, including hypertension (81%), renal disease (100%), and diabetes mellitus (25%).1 They also exhibited elevated NT-proBNP levels (~500 ng/l) and substantial dyspnea with ambulation, which improved after ligation. This suggests that some of the participants had (potentially occult) HF with preserved ejection fraction. Was echocardiography data available to estimate the likelihood of undiagnosed HF with preserved ejection fraction,4 which is common in these patients? In addition, the mean cardiac index was borderline elevated (3.4 L/min/m2, normal <4 L/min/m2), suggesting that some of the participants might have had an element of high output HF, which may develop following fistula placement.5 Could the authors stratify the response to ligation among the cohort with potential high-output HF or undiagnosed HF with preserved ejection fraction? These patients may be more likely to respond favorably to ligation. Arteriovenous fistulas are the preferred dialysis access in patients with advanced kidney disease because they carry less risk of infection and thrombosis compared with dialysis catheters and are less thrombogenic and more durable as compared with arteriovenous grafts. Besides showing the benefits of ligating fistulas in patients no longer © 2019 American Heart Association, Inc. LETTER TO THE EDITOR