A 
system for accessing a patient's cardiac 
anatomy which includes an endovascular aortic partitioning device that separates the 
coronary arteries and the heart from the rest of the patient's arterial 
system. The endovascular device for partitioning a patient's 
ascending aorta comprises a flexible shaft having a distal end, a proximal end, and a first inner lumen therebetween with an opening at the distal end. The shaft may have a preshaped 
distal portion with a curvature generally corresponding to the curvature of the patient's 
aortic arch. An expandable means, e.g. a 
balloon, is disposed near the distal end of the shaft proximal to the opening in the first inner lumen for occluding the 
ascending aorta so as to block substantially all 
blood flow therethrough for a plurality of cardiac cycles, while the patient is supported by 
cardiopulmonary bypass. The endovascular aortic partitioning device may be coupled to an arterial bypass cannula for delivering oxygenated blood to the patient's arterial 
system. The heart 
muscle or myocardium is paralyzed by the retrograde delivery of a cardioplegic fluid to the myocardium through patient's 
coronary sinus and coronary veins, or by antegrade delivery of cardioplegic fluid through a lumen in the endovascular aortic partitioning device to infuse cardioplegic fluid into the 
coronary arteries. The pulmonary 
trunk may be vented by withdrawing liquid from the 
trunk through an inner lumen of an elongated 
catheter. The cardiac accessing system is particularly suitable for removing the 
aortic valve and replacing the removed valve with a 
prosthetic valve.