A 46-year-old man with autosomal dominant polycystic kidney disease comes to the clinic after an arteriovenous fistula was placed 2 weeks ago in preparation for hemodialysis. He is feeling well and has no concerns. The surgical site shows good healing with no evidence of infection. Doppler interrogation shows high fistula flow rates. Compared to the presurgical state, which of the following is most likely present in this patient?

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Hemodialysis access is commonly obtained through a surgically created arteriovenous fistula. The fistula forms an enlarged vein, which serves as an access point and facilitates adequate blood flow to and from the hemodialysis machine. enlarged vein An arteriovenous fistula also causes hemodynamic changes. Because the fistula allows a portion of blood to bypass the high resistance of the systemic arterioles, systemic vascular resistance (SVR) is effectively decreased (decreased afterload). In addition, blood passing through the fistula returns to the right atrium more quickly and easily, creating an increase in venous return (increased preload). Both the increased venous return and decreased SVR contribute to increased cardiac output (CO); decreased SVR necessitates an increase in CO to maintain organ perfusion pressure (mean arterial blood pressure = CO × SVR). Marked changes in these hemodynamic parameters can lead to high-output heart failure; therefore, care must be taken to ensure that a surgically created arteriovenous fistula is not too large. (Choices A and B) Sepsis involves a decrease in both afterload and preload. CO is initially increased but eventually decreases in late sepsis when tissue ischemia and the accumulation of cytotoxic mediators begin to depress cardiac contractility and heart rate. (Choice D) Administration of an adrenergic agent affecting both alpha and beta receptors (eg, epinephrine) leads to venoconstriction, arterioconstriction, and increased contractility to increase preload, afterload, and CO. (Choice E) Hypovolemia causes decreased preload with a resulting decrease in CO and a responsive increase in SVR (afterload). (Choice F) Increased afterload and preload with decreased CO is seen with decompensated heart failure resulting from left ventricular dysfunction (low-output heart failure). Educational objective: An arteriovenous fistula allows blood to bypass the high-resistance systemic capillaries, resulting in decreased systemic vascular resistance (afterload), increased venous return (preload), and increased cardiac output. A large arteriovenous fistula can lead to high-output heart failure.

A 46-Year-Old Man with Autosomal Dominant Polycystic Kidney Disease Comes