A method and system for estimating the volume of blood ejected from the left ventricle of the heart to a succeeding chamber/conduit, or vice-versa, while imaging the intersection of such structures is described. The process utilizes either the M-mode to estimate volume differences in a view of the ventricle over time or Doppler processing techniques to obtain flow profiles across intersections (e.g., valves), or blood vessels, which are then utilized to calculate output. This process can be combined with ECG guidance/triggering to measure/track changes in output from beat to beat, or during the course of an evaluation or therapeutic procedure. This process can be specifically used for the placement of permanent pacemaker electrodes.