Figure 1. A schematic representation of the protocol. All measurements and interventions were performed in the same patients, both awake and after induction of anesthesia. Intermittent measurements included blood sampling from the radial artery and coronary sinus and measurement of cardiac output and pulmonary capillary wedge pressure. Continuous recordings included coronary sinus thermodilution signals, arterial blood pressure, pulmonary artery pressure, right atrial pressure, and electrocardiographic lead II. Heart rate (HR) steps-up were induced by pacing; HR steps-down, by discontinuation of pacing.