High-output cardiac failure is one of the cardiovascular problems associated with multiple myeloma and frequently seen in patients with extensive bone lesions. The purpose of this study was to search arteriovenous shunting in patients with multiple myeloma and cardiac failure. Methods: After the exclusion of other causes of congestive heart failure, 11 patients whose cardiac indices were higher than or equal to 4 liter/min/m(2) were selected for the study (7 women, 4 men; mean age 59.64 +/- 8.92 yr). All patients had Stage II-III disease and femoral involvement in radiological examination. Arteriovenous shunting was determined by means of intra-arterial injection technique of Tc-99m-macroaggregated albumin (MAA) particles. A quantitative analysis of all scans was performed, and the results were correlated with cardiac index. Results: Mean cardiac index was 4.33 +/- 0.36 liter/min/m(2) in the study group. In all cases, arteriovenous shunting was detected (18.70% +/- 17.29%), and inhomogenous, increased radioactivity accumulation was revealed in the femoral region (lesion-to-background ratio 2.71 +/- 2.08). This zone corresponded to the area of infiltration in a radiograph. A significant correlation was found between shunting values and cardiac indices (r = 0.7899, p = 0.004, Spearman). Although all patients had varying degrees of anemia, we did not find such a relationship between the degree of anemia and cardiac index. Conclusion: Arteriovenous shunting within involved skeleton contributes significantly to the development of high-output cardiac failure in multiple myeloma.