The impact of haemodialysis arteriovenous fistula on haemodynamic parameters of the cardiovascular system

Abstract

BackgroundSatisfactory vascular access flow (Qa) of an arteriovenous fistula (AVF) is necessary for haemodialysis (HD) adequacy. The aim of the present study was to further our understanding of haemodynamic modifications of the cardiovascular system of HD patients associated with an AVF. The main objective was to calculate using real data in what way an AVF influences the load of the left ventricle (LLV).MethodsAll HD patients treated in our dialysis unit and bearing an AVF were enrolled into the present observational cross-sectional study. Fifty-six patients bore a lower arm AVF and 30 an upper arm AVF. Qa and cardiac output (CO) were measured by means of the ultrasound dilution Transonic Hemodialysis Monitor HD02. Mean arterial pressure (MAP) was calculated; total peripheral vascular resistance (TPVR) was calculated as MAP/CO; resistance of AVF (AR) and systemic vascular resistance (SVR) are connected in parallel and were respectively calculated as AR = MAP/Qa and SVR = MAP/(CO − Qa). LLV was calculated on the principle of a simple physical model: LLV (watt) = TPVR·CO2. The latter was computationally divided into the part spent to run Qa through the AVF (LLVAVF) and that part ensuring the flow (CO − Qa) through the vascular system. The data from the 86 AVFs were analysed by categorizing them into lower and upper arm AVFs.ResultsMean Qa, CO, MAP, TPVR, LLV and LLVAVF of the 86 AVFs were, respectively, 1.3 (0.6 SD) L/min, 6.3 (1.3) L/min, 92.7 (13.9) mmHg, 14.9 (3.9) mmHg·min/L, 1.3 (0.6) watt and 19.7 (3.1)% of LLV. A statistically significant increase of Qa, CO, LLV and LLVAVF and a statistically significant decrease of TPVR, AR and SVR of upper arm AVFs compared with lower arm AVFs was shown. A third-order polynomial regression model best fitted the relationship between Qa and LLV for the entire cohort (R2 = 0.546; P < 0.0001) and for both lower (R2 = 0.181; P < 0.01) and upper arm AVFs (R2 = 0.663; P < 0.0001). LLVAVF calculated as % of LLV rose with increasing Qa according to a quadratic polynomial regression model, but only in lower arm AVFs. On the contrary, no statistically significant relationship was found between the two parameters in upper arm AVFs, even if mean LLVAVF was statistically significantly higher in upper arm AVFs (P < 0.0001).ConclusionsOur observational cross-sectional study describes statistically significant haemodynamic modifications of the CV system associated to an AVF. Moreover, a quadratic polynomial regression model best fits the relationship between LLVAVF and Qa, but only in lower arm AVFs.

Effect of hemodialysis access blood flow on cardiac events after coronary artery bypass grafting using an internal thoracic artery

“…The major finding in this study is association of left ventricle load with AVF flow only in lower arm, but not in upper arm AVFs. Our study results are in agreement with Basile et al (21), showing that higher AVF flow (more commonly seen in upper arm access) failed to associate with higher cardiac risk.…”

The complex relationship among arteriovenous access, heart, and circulation

“…However, recent data suggest that the relationship between Qa and CO is not linear; a third‐order polynomial regression model best fits this relationship with a curve consisting of an initial plateau of CO followed by a steep slope with CO rising more sharply at greater Qa (Table ). Furthermore, Basile et al recently showed that the relationship between Qa and the workload of the LV also follows a third‐order polynomial regression model. The causes of this phenomenon are not known, but one can hypothesize a sort of myocardial functional reserve and, then, of myocardial adaptation, capable of sustaining increases of Qa in the long‐term without the precipitation of heart failure (HF).…”

“…Of note, the arteriovenous access and the systemic circulation are connected in a parallel way. Reproduced from Basile et al with permission from Oxford University Press. [Color figure can be viewed at wileyonlinelibrary.com]…”

Controversies in the management of the haemodialysis-related arteriovenous fistula following kidney transplantation

“…The causal link between access flow and increased morbi-mortality probably exists, but still needs to be directly proven [8, 50]. …”

“…AVF referral within ∼12 months of the estimated time to dialysis performed best among time frame strategies, although the timing of referral is classically guided by the patient’s age and by his/her individual likelihood and rate of progression to ESRD [6, 7]. The AVF flows in the forearm usually reach 500–900 mL/min, whereas those in the upper arm are 900–1500 mL/min [2, 8]. Inherently, AVF causes significant haemodynamic changes in patients under chronic HD, which may lead to serious complications, including arterial steal, pulmonary hypertension (PH) and high-output cardiac failure [9].…”