A portable ultrasound unit and docking cart for the unit are provided. When the portable unit is mounted to the docking cart, the docking cart transforms the portable unit into a cart-based system with enhanced features and functionality such as improved ergonomics, ease of use, a larger display format, external communications connectivity, multiple transducer connections, and increased data processing capabilities. A clinician display and patient display may be provided on the cart. Communications circuitry in the docking cart may be used to support communications between the docking cart's processor and external networks and devices. The docking cart may receive physiological signals such as cardiac signals and may use this information to synchronize ultrasound imaging operations with a patient's physiological condition. Adjustable user interface controls, data handling features, security features, power control functions, and thermal management capabilities may be provided in the docking cart.