Letter by Budryte et al. regarding article “Cardiac implications of upper-arm arteriovenous fistulas: A case series”

To the Editor

We read with considerable interest the recent Research Article by Pucchio et al., ¹ presenting a prospective case series of cardiac imaging 12-months following upper-arm arterio-venous fistula (AVF) creation, demonstrating adverse changes in patients’ cardiac morphology—increases in left ventricular mass (LVM), changes of the ejection fraction (EF), and left atrial volume (LAV). Because of a scarcity of such research, it is a great essay presenting the timeline for cardiac involvement due to hemodynamic changes as a result of AVF formation. However, there are some issues about the article which merit further discussion and investigation.

Initially, 50 patients were enrolled in this study, however, only eight fulfilled eligibility criteria. As a result, the sample size was too small to make appropriate conclusions with statistically significant findings. There is no comparative control group that would allow separating outcomes of cardiac morphology and function of ESKD patients with and without AVF creation. Also, shortcomings of this research come in the form of patient selection: all enrolled patients had hypertension, most of them had hyperlipidemia or diabetes, half of the patients had overweight (part of all BMI’s was calculated incorrectly), and all patients were previous or active smokers. Interaction between these risk factors and comorbidities (CKD) causes aging of cardiovascular function and limited cardiac regeneration capacity which contribute to the development of heart failure. ² It is predisposed to the idea that all patients have already had changes in cardiac tissue, AVF formation caused an acceleration of cardiac remodeling. From the paper it is unclear if the eight patients had started dialysis. Uncontrolled hypertension and high fluid gains are also important factors that affect cardiac morphology.

In addition, in the article cardiac morphology or function changes were described using only visual cardiovascular magnetic resonance (CMR) imaging without relation to any circulating cardiac biomarkers or other factors that may be associated with these changes. Cardiac biomarkers like NT-proBNP, high-sensitivity troponin, or soluble suppression of tumorigenesis-2 can predict and monitor the presence, direction, and magnitude of heart structural and functional alterations. ³ BNP and NT-proBNP are useful screening tests for HF or asymptomatic LV dysfunction, also they are strong predictors of cardiovascular morbidity and mortality. ⁴ Although the authors suggested that the AVF flow rate was dependent on the fistula’s position and had significant hemodynamic implications, they neither evaluated patients’ blood flow in AVF nor related its results with CMR. According to Stoumpos et al., ⁴ AVF creation for renal replacement therapy resulted in a significant increase of LVM, which was proportional to the fistula flow. Even if AVF location has an impact on the fistula flow rate ⁵ (upper-arm AVFs have higher flow than lower-arm AVFs), every AVF itself has a particular flow rate that determines various cardiac implications. Therefore assessment of blood flow rate is critical for scientific research, clinical outcomes, and significant findings.

Finally, we feel that Pucchio et al. ¹ did a great job by measuring cardiac alterations due to AVF formation. We believe, however, that the impact of AVF creation on clinical and mortality outcomes remains to be proven. Further investigations with more patients are needed, as well as evaluation of surrogate markers and AVF flow rate, factors that are strongly associated with cardiovascular outcomes.