An endoventricular injection catheter (2; 202) with integrated echocardiographic capability, comprising: a first proximal housing; a second proximal housing including an injection cannula lumen (62; 262; 267; 662); an elongated body including a distal section (36; 236) at a distal end of the catheter, the distal section having an imaging core (12; 350) positioned therein, the imaging core coupled to the first proximal housing by a drive cable and arranged to transmit ultrasonic energy and to receive reflected ultrasonic energy at the distal section to provide electrical signals representing echocardiographic images to enable cardiac visualization; the elongated body having a telescoping section that comprises: an outer supporting member bonded to the second proximal housing, an inner tubular member bonded to the first proximal housing, and a primary inner member bonded to the second proximal housing and supporting the drive cable, the primary inner member slidably connected with the inner tubular member, the outer supporting member, the inner tubular member, and the primary inner member arranged in a longitudinally nested arrangement, the slidable connection between the inner tubular and primary inner members allowing longitudinal positioning of the imaging core (12; 350) between an un-extended position and a fully extended position; and an injector (400; 500) carried on the elongated body with the imaging core, the injector having a cannula (402; 502) received by the injection cannula lumen (62; 262; 267; 662) and being arranged to inject a therapeutic agent proximate the distal section, thereby injecting into tissue of the heart visualized by the imaging core during cardiac visualization. a first proximal housing; a second proximal housing including an injection cannula lumen (62; 262; 267; 662); an elongated body including a distal section (36; 236) at a distal end of the catheter, the distal section having an imaging core (12; 350) positioned therein, the imaging core coupled to the first proximal housing by a drive cable and arranged to transmit ultrasonic energy and to receive reflected ultrasonic energy at the distal section to provide electrical signals representing echocardiographic images to enable cardiac visualization; the elongated body having a telescoping section that comprises: an outer supporting member bonded to the second proximal housing, an inner tubular member bonded to the first proximal housing, and a primary inner member bonded to the second proximal housing and supporting the drive cable, the primary inner member slidably connected with the inner tubular member, the outer supporting member, the inner tubular member, and the primary inner member arranged in a longitudinally nested arrangement, the slidable connection between the inner tubular and primary inner members allowing longitudinal positioning of the imaging core (12; 350) between an un-extended position and a fully extended position; and an outer supporting member bonded to the second proximal housing, an inner tubular member bonded to the first proximal housing, and a primary inner member bonded to the second proximal housing and supporting the drive cable, the primary inner member slidably connected with the inner tubular member, the outer supporting member, the inner tubular member, and the primary inner member arranged in a longitudinally nested arrangement, the slidable connection between the inner tubular and primary inner members allowing longitudinal positioning of the imaging core (12; 350) between an un-extended position and a fully extended position; and an injector (400; 500) carried on the elongated body with the imaging core, the injector having a cannula (402; 502) received by the injection cannula lumen (62; 262; 267; 662) and being arranged to inject a therapeutic agent proximate the distal section, thereby injecting into tissue of the heart visualized by the imaging core during cardiac visualization.