The present invention relates to improved therapies for the treatment of heart disease, particularly the improved delivery of therapeutic agents to heart tissue by direct infusion into the coronary circulation. A preferred embodiment of the invention is a method of treating or preventing a cardiovascular disease by transfecting cardiac cells of a large mammal, the method comprising, identifying a mammal in need of treatment or prevention of heart disease, supplying NO to the coronary circulation prior to, and/or during the infusion of a therapeutic polynucleotide into a blood vessel of the coronary circulation
