Abstract: A medical lead adaptor that provides a rapid, secure, insulated connection of the lead connector end assembly of a cardiac lead having electrodes adapted to be placed in or on the body with an external medical device. The adaptor connector assembly is configured with an elongated receptacle to accept a bipolar, in-line, or a unipolar lead connector end sharing common dimensions. The elongated receptacle includes connector pin and ring receptacle contacts spaced apart from one another therein. In a preferred embodiment, an elongated slot that extends laterally of the elongated receptacle cooperates with a lock mechanism to allow the lateral insertion of the lead connector end assembly, with a stylet wire inserted into the cardiac lead body lumen, into the elongated receptacle. When inserted therein, the lead connector ring and/or pin are nested into contact with the ring and/or pin receptacle contacts and are held there by the lock mechanism.