A cardiac rhythm management system comprising: a medical electrical lead (14, 114, 214) including: an elongated, flexible body (37, 137, 237) made of an electrically insulative material, the body having a proximal end and distal end, the body being sized to permit the distal end to be advanced through a right atrium and coronary sinus and into a first coronary vein adjacent to a left ventricle of a patient's heart; a first opening (53, 153, 253) in the body at a point intermediate the proximal and distal ends; a lumen (72, 255) extending longitudinally within the lead body and in communication with the first opening; and at least one electrode (50, 150) coupled to the lead body proximate the distal end; a pressure sensing element (16, 116, 216) movably disposed at least partially in the lead lumen and having a distal end portion dimensioned to be extendable through the opening and to be positioned in the first coronary vein or a second coronary vein adjacent to the left ventricle of the patient's heart, the pressure sensing element including: a flexible, elongated conductive member (56, 156) electrically insulated over a portion of its length; and a pressure transducer (60, 160, 260) fixedly and operatively coupled to the conductive member in the distal end portion of the pressure sensing element; and an implantable pulse generator including a detection/energy delivery system coupled to the lead and the pressure sensing element, the detection/energy delivery system configured to receive cardiac rhythm signals from the at least one electrode and signals indicative of fluid pressure parameters from the pressure transducer, and to deliver an electrical signal to the at least one electrode. a medical electrical lead (14, 114, 214) including: an elongated, flexible body (37, 137, 237) made of an electrically insulative material, the body having a proximal end and distal end, the body being sized to permit the distal end to be advanced through a right atrium and coronary sinus and into a first coronary vein adjacent to a left ventricle of a patient's heart; a first opening (53, 153, 253) in the body at a point intermediate the proximal and distal ends; a lumen (72, 255) extending longitudinally within the lead body and in communication with the first opening; and at least one electrode (50, 150) coupled to the lead body proximate the distal end; an elongated, flexible body (37, 137, 237) made of an electrically insulative material, the body having a proximal end and distal end, the body being sized to permit the distal end to be advanced through a right atrium and coronary sinus and into a first coronary vein adjacent to a left ventricle of a patient's heart; a first opening (53, 153, 253) in the body at a point intermediate the proximal and distal ends; a lumen (72, 255) extending longitudinally within the lead body and in communication with the first opening; and at least one electrode (50, 150) coupled to the lead body proximate the distal end; a pressure sensing element (16, 116, 216) movably disposed at least partially in the lead lumen and having a distal end portion dimensioned to be extendable through the opening and to be positioned in the first coronary vein or a second coronary vein adjacent to the left ventricle of the patient's heart, the pressure sensing element including: a flexible, elongated conductive member (56, 156) electrically insulated over a portion of its length; and a pressure transducer (60, 160, 260) fixedly and operatively coupled to the conductive member in the distal end portion of the pressure sensing element; and a flexible, elongated conductive member (56, 156) electrically insulated over a portion of its length; and a pressure transducer (60, 160, 260) fixedly and operatively coupled to the conductive member in the distal end portion of the pressure sensing element; and an implantable pulse generator including a detection/energy delivery system coupled to the lead and the pressure sensing element, the detection/energy delivery system configured to receive cardiac rhythm signals from the at least one electrode and signals indicative of fluid pressure parameters from the pressure transducer, and to deliver an electrical signal to the at least one electrode.