Inflammation probably contributes to the development and progress of heart failure. Proteins called cytokines, which are produced by damaged tissues and leukocytes as part of the inflammatory response, affect the heart both directly and indirectly. They exacerbate hemodynamic imbalances, act as negative inotropes, stimulate left ventricular hypertrophy, and promote the production of still more cytokines, which continue the cycle. Several medications counter these effects in vitro, and some are in clinical testing.