An assembly and method for effecting the condition of a mitral valve annulus of a heart includes a guide wire configured to be fed into the coronary sinus of the heart, and a mitral valve annulus therapy device configured to be slidingly received on the guide wire and advanced into the coronary sinus of the heart on the guide wire. A guide tube may further be employed for guiding the device into the coronary sinus. An introducer which may be employed for pushing the device into or pulling device out of the heart has a mechanism for releasably locking to the device. This enables substitution of the device if needed. Also, the crossover point of the circumflex artery and coronary sinus may be determined and avoided when the device is deployed.