Interventional medical systems and associated assemblies and methods

An interventional medical system comprising a relatively compact implantable medical device and a catheter assembly;

• the medical device comprising an electronic controller, a hermetically sealed housing containing the controller, an electrode electrically coupled to the controller, and a fixation member mounted to a distal end of the housing;
• the catheter assembly comprising an elongate inner tubular member, an elongate outer tubular member, and an end-cap subassembly;
• the outer tubular member defining an elongate lumen in which the inner tubular member extends, the outer tubular member extending from a proximal end thereof to a distal terminal end thereof, the distal terminal end defining a distal-most opening of the lumen, the lumen, in proximity to the distal-most opening, being sized to contain an entirety of the medical device therein, and the distal-most opening allowing passage of the medical device therethrough;
• the inner tubular member including a distal end configured to engage with a proximal end of the medical device, and the outer tubular member being moveable between a retracted position and an advanced position relative to the inner tubular member;
• and the end-cap subassembly of the catheter assembly comprising:
• a cap including a proximal end, a distal end, a first portion extending from the proximal end, a second portion extending from the distal end of the cap, and a transition zone extending between the first and second portions, the first portion having a girth sized to fit within the distal-most opening of the lumen of the outer tubular member, the second portion having a girth that tapers from a first size at the transition zone to a second, smaller size at the distal end, the girth of the second portion at the transition zone being too large to fit within the distal-most opening of the lumen of the outer tubular member;
• and
• a spring-biased tethering member secured to the catheter assembly and extending within the lumen of the outer tubular member, a distal end of the tethering member being coupled to the cap so that the tethering member extends from the proximal end of the cap, the tethering member being configured extend alongside the medical device, when the device is contained in the lumen of the outer tubular member, and to hold the cap in a closed position and in an open position;
• and
• wherein, when the outer tubular member of the catheter assembly is in the advanced position, a distance between the distal end of the inner tubular member and the distal-most opening of the outer tubular member is sufficient to accommodate the entirety of the medical device, the first portion of the cap, and the spring-biased tethering member extending alongside the device;
• when the first portion of the cap extends within the distal-most opening of the lumen of the outer tubular member of the catheter assembly, the tethering member holds the cap in the closed position, at which the first portion of the cap is approximately concentric with the distal-most opening;
• and
• when the cap is separated from the distal-most opening of the lumen of the outer tubular member of the catheter assembly, and the spring-biased tethering member extends out from the distal-most opening, the tethering member holds the cap in the open position, at which an entirety of the cap is laterally offset from the distal-most opening.