We have developed a sonomicrometer and continuous wave-length (CW) Doppler flowmeter for a multichannel telemetry system. These developments will enable us to measure ventricular dimension and coronary artery blood velocity, which are valuable parameters to characterize sudden cardiac death (SCD) in ambulatory animal models of ventricular arrhythmias. The design goals for the sensors were accuracy, low power consumption, small size and compatibility with each other. The circuits were designed successfully and tested simultaneously in vivo. The CW Doppler flowmeter draws 9 mA and the sonomicrometer draws 28 mA on a 5-V supply. The ability to measure heart dimension and blood velocity will add significantly to our understanding of the sequence of events leading up to spontaneous sudden cardiac death. © 2005 IEEE.