Effects of arteriovenous fistulas on cardiac oxygen supply and demand

Background Arteriovenous (AV) fistulas used for hemodialysis access may aff ect cardiac load by increasing the preload while decreasing the afterload. In dogs, AV fistulas have also been shown to affect coronary perfusion nega tively. We investigated the net effect of AV fistulas on cardiac oxygen sup ply and demand. Methods. Aortic pressure waves were reconstructed from finger pressure reco rdings obtained on the nonfistula arm using a wave-form filter. Changes in systolic, mean, and diastolic aortic pressure were calculated, together wit h changes in heart rate (HR), stroke volume (SV), cardiac output (CO), and systemic vascular resistance (SVR) during a 60-second compression of AV fis tulas in 10 patients. Changes in cardiac supply and demand were estimated b y calculating the area under the aortic pressure curve during diastole [dia stolic pressure time index (DPTI)] and systole [systolic pressure time inde x (SPTI)], respectively. Results. During fistula compression, systolic, mean and diastolic pressure increased by 4.2 +/- 4.3, 2.6 +/- 3.0, and 2.8 +/- 2.9 mm Hg (mean +/- SD, all P < 0.05). The HR decreased by 3.8 +/- 2.5 beats per minute (P < 0.01), and SV decreased 3.7 +/- 6.1% (NS). CO decreased 9.4 +/- 8.6%, and SVR inc reased 14.3 +/- 11.7% (both P < 0.05). The SPTI increased by 1.5 +/- 1.5 mm Hg.sec (P < 0.01), and the DPTI increased by 7.6 +/- 8.1 mm Hg.sec (14.8% increase, P < 0.05) during compression. The ratio of supply and demand (DPT I/SPTI) improved by 13.5 +/- 13.0% (P < 0.01) when the fistula was compress ed. Conclusion. AV fistulas have a small effect on left ventricular oxygen dema nd, but decrease cardiac oxygen supply considerably.