Cardiac impact of arteriovenous fistulas: what tools to assess?

The relationship between arteriovenous access flow (Qa) and cardiovascular changes is complex. Several studies have shown cardiac remodeling and symptoms of heart failure for high-flow arteriovenous fistulas (AVF). To evaluate the early cardiovascular impact of AVF. Forty-seven patients with an AVF, hospitalized for the evaluation of high-flow AVF or a pre-kidney transplant assessment were included. We collected clinical and biological data. We also collected data of the assessment by transthoracic echocardiography, functional evaluation by 6-min-walk test and peak oxygen consumption, and measurement of coronary flow reserve by dynamic myocardial perfusion imaging. The measurement of Qa was performed by color Doppler ultrasound and then indexed to the body surface area (Qai) and to the cardiac output (CO) (Qa/CO). Patients were poorly symptomatic (18 and 1 patients NYHA stage 2 and 3, respectively). There was no correlation between Qa, Qai, or Qa/CO and functional status, assessed by peak oxygen consumption (P = 0.891; P = 0.803; P = 0.939, respectively). Symptomatic patients did not have higher Qa, Qai or Qa/CO than asymptomatic (2260 vs 2197 mL/min, P = 0.402; 1257 vs 1256 mL/min/m2 , P = 0.835; and 34% vs 37%, P = 0.701, respectively). There was no correlation between Qa, Qai or Qa/CO and left ventricular end-diastolic volume or left ventricular ejection fraction. There was no correlation between coronary flow reserve and these 3 parameters of vascular access flow. However, the global longitudinal strain (GLS) was correlated with Qa and Qa/CO (R = 0.331, P = 0.023 and R = 0.380, P = 0.008, respectively). Increase of Qa or Qa/CO was associated with an alteration of the GLS. A cut-off value of 2250 mL/min for Qa allowed 83% sensitivity and 63% specificity for detecting an alteration of the GLS > - 18%. A cut-off value of 33% for Qa/CO allowed 92% sensitivity and 65% specificity. Impact of AVF on cardiac parameters is weak. However, GLS is the first parameter to be impacted by the flow of the fistula. Systematic transthoracic echocardiography evaluation with measurement of GLS should be proposed for all patients with Qa > 2250 mL/min or Qa/CO > 33%, to detect those at higher risk of cardiac impact of the AVF.