Methods and systems for determining whether an implanted catheter used to deliver fluids to a selected internal delivery site is malfunctioning. The malfunctions may include that the infusion section of the catheter is not located at or has migrated away from the selected internal delivery site, is leaking, is blocked, etc. The determination is made by analyzing the pressure modulation of fluid within the catheter and determining whether the pressure of the fluid in the catheter is modulated by physiologic pressure changes experienced at the selected internal delivery site. The physiologic pressure modulations at the selected internal delivery site may be caused by, e.g., cardiac activity, respiration, changes in patients posture, etc.
