An assembly of an implanting accessory and of a flexible implantable stimulation lead, said lead comprising a lead body, and said lead being able to be combined with an active implantable medical device via its proximal end and being configured to be implanted through a heart wall, in particular through the free wall (VD') of the right ventricle, via its distal end, the implanting accessory comprising a needle with a pointed free puncturing end, the needle being, at least in its distal part, a hollow needle comprising an inner lumen opening onto the pointed free puncturing end, at least a first portion of the lead being able to be inserted via its distal end into the inner lumen of the needle, wherein: in a state where the first portion of the lead is inserted into the lumen of the needle, said first portion of the lead comprises at least a first branch that extends from the lead body in a direction oriented toward the pointed free end of the needle, the first branch extending from the lead body from a junction point arranged at a predetermined distance from the distal end that forms a second portion of the lead body between the junction point of the first branch and the distal end of the lead; and the lead body further comprises a third portion that is less rigid than said first branch and the second portion, the third portion extending toward the proximal end of the lead from the junction point of the first branch, such that the first branch and the second portion are configured to pivot securely with one another relative to said junction point in response to the free end of the first branch coming to abut against the inner wall of the heart, in particular against the inner wall (VD") of the right ventricle, during a removal movement of the lead from the inside of the heart, in particular from the inside of the right ventricle, toward the outside of the heart. said lead being able to be combined with an active implantable medical device via its proximal end and being configured to be implanted through a heart wall, in particular through the free wall (VD') of the right ventricle, via its distal end, the implanting accessory comprising a needle with a pointed free puncturing end, the needle being, at least in its distal part, a hollow needle comprising an inner lumen opening onto the pointed free puncturing end, at least a first portion of the lead being able to be inserted via its distal end into the inner lumen of the needle, wherein: in a state where the first portion of the lead is inserted into the lumen of the needle, said first portion of the lead comprises at least a first branch that extends from the lead body in a direction oriented toward the pointed free end of the needle, the first branch extending from the lead body from a junction point arranged at a predetermined distance from the distal end that forms a second portion of the lead body between the junction point of the first branch and the distal end of the lead; and the lead body further comprises a third portion that is less rigid than said first branch and the second portion, the third portion extending toward the proximal end of the lead from the junction point of the first branch, such that the first branch and the second portion are configured to pivot securely with one another relative to said junction point in response to the free end of the first branch coming to abut against the inner wall of the heart, in particular against the inner wall (VD") of the right ventricle, during a removal movement of the lead from the inside of the heart, in particular from the inside of the right ventricle, toward the outside of the heart. in a state where the first portion of the lead is inserted into the lumen of the needle, said first portion of the lead comprises at least a first branch that extends from the lead body in a direction oriented toward the pointed free end of the needle, the first branch extending from the lead body from a junction point arranged at a predetermined distance from the distal end that forms a second portion of the lead body between the junction point of the first branch and the distal end of the lead; and the lead body further comprises a third portion that is less rigid than said first branch and the second portion, the third portion extending toward the proximal end of the lead from the junction point of the first branch, such that the first branch and the second portion are configured to pivot securely with one another relative to said junction point in response to the free end of the first branch coming to abut against the inner wall of the heart, in particular against the inner wall (VD") of the right ventricle, during a removal movement of the lead from the inside of the heart, in particular from the inside of the right ventricle, toward the outside of the heart.