Intravascular delivery system is designed for a safe and efficient access to secondary and tertiary vascular structures, such as the branches of the coronary sinus, to enhance the delivery and deployment of various catheters, such as, for example, pacemaker electrical leads. The over-the-wire system features a straight, or alternatively shaped, micro-catheter distal tip of an inner catheter that seamlessly cooperates with a peel-away reinforced outer catheter. The inner catheter and the peel-away reinforced outer catheter are advanced in their engaged mode of operation towards (or beyond) the target site. Subsequently, the inner and outer catheters are disengaged, and the inner catheter is removed from the outer catheter. A pacemaker lead may be advanced over the wire inside the outer catheter to the target site for deployment. Subsequently, the outer catheter is easily split and may be rapidly removed from the blood vessel.