Cardiac MRI requires substantial training to acquire the images appropriately and interpret them correctly. A number of less expensive methods can be used to get similar data and so MRI is usually the method of last choice.

It is possible to get pressure readings directly from MRI and by that to get the resistance. See the following article from Rich Thompson concerning one technique.

Thompson RB and McVeigh ER. Fast Measurement of Intra-Cardiac Pressure Differences with 2D Breath-Hold Phase-Contrast MRI, Magn. Reson. Med. 49, 1056 - 66 (2003)

Is your context solely research ? Or do you look for a method that can be implemented on a more widely scale i.e. in routine patient care ?