Effect of hemodialysis on cardiac performance and transmural myocardial perfusion

The effects of hemodialysis on cardiac performance and myocardial oxygen balance were evaluated by impedance cardiography in 16 patients with end-stage renal failure treated with regular hemodialysis. Cardiac symptoms and/or failure were present in 8 patients (group A) whereas 8 patients (group B) had no signs of heart dysfunction. The hemodialysis were carried out without ultrafiltration so that the body weight was the same before and after dialysis. The two groups did not differ significantly with regard to either biochemical values or hemodynamic parameters before dialysis. During dialysis mean cardiac output (CO) increased significantly 7.1 +/- 2.8 l/min to 9.1 +/- 3.6 l/min (P less than 0.01), mainly in patients group A, and was maximum after 90 min. The myocardial oxygen balance estimated from the supply/demand ratio (DPTI/SPTI) was significantly reduced after 20 min from 1.14 +/- 0.16 to 0.99 +/- 0.12 (P less than 0.01). After 60 min DPTI/SPTI decreased to its lowest value due to an excess of myocardial oxygen demand (SPTI) over myocardial oxygen supply (DPTI), signifying a transitory underperfusion of the subendocardium which occurred mainly in patients with cardiac failure (group A). Mean arterial blood pressure remained unchanged whereas mean heart rate increased significantly after 90 min and remained raised throughout the rest of dialysis (78.8 +/- 10.4 bpm to 87.1 +/- 12.6 bpm [P less than 0.01]). Total peripheral resistance (TPR) was decreased significantly after 5 min (P less than 0.01), but subsequent falls were not significant. Changes in the DPTI/SPTI ratio showed that the improvement in left ventricular performance was at the expense of myocardial oxygen balance, which caused a greater incidence of myocardial underperfusion, particularly in patients with cardiac failure.