A neuromodulation system for treating acute heart failure syndromes includes a first catheter having a parasympathetic therapy element adapted for positioning within a first blood vessel such as a superior vena cava, and a second catheter sympathetic therapy element adapted for positioning with a second, different, blood vessel such as the pulmonary artery. The catheters comprise a system in which one of catheters is slidably disposed over the other of the catheters. The system may further be slidably disposed over a third elongate element such as a Swan-Ganz catheter positionable within a pulmonary artery, such that the Swan-Ganz may be used for monitoring parameters such as blood pressure and cardiac output during neuromodulation therapy. The parasympathetic therapy element is energized to deliver neuromodulation therapy to a parasympathetic nerve fiber such as a vagus nerve, while the sympathetic therapy element is energized to deliver neuromodulation therapy to a sympathetic nerve fiber such as a sympathetic cardiac nerve fiber. For treatment of acute heart failure syndromes, the neuromodulation therapy may be used to lower heart rate and increase cardiac inotropy.