A pair of cooperating catheters, chosen from an inner catheter and two possible outer catheters, are used together to provide rapid access to the Left heart for diagnostic or therapeutic interventions. The pair of catheters can be used to carry out an electrographic determination of the location of the Fossa Ovalis on the septum. Features on the Catheter system permit quick and reliable confirmation of the catheter location via echo or x-rays. Once across the septum the inner catheter is removed from the outer catheter and a standard intervention may be carried out through the lumen of the outer catheter.
