A medical device and associated method for detecting arrhythmias that includes sensing cardiac electrical signals and cardiac hemodynamic signals, determining a long-term baseline hemodynamic measurement in response to a plurality of the sensed cardiac hemodynaic signals, detecting a period of increased metabolic demand in response to the sensed cardiac electrical signals, determining a sinus tachycardia baseline hemodynamic measurement in response sensing of cardiac hemododynamic signals during the detected period of increased metabolic demand, and detecting the arrhythmia and delivering therapy in response to one of only the sensed cardiac electrical signals and the sensed cardiac electrical signals in combination with one or both of the determined long-term baseline hemodynamic measurement and the sinus tachycardia baseline hemodynamic measurement.