[Photodynamic therapy in cardiac and vascular surgery]

One of the major drawbacks to therapeutic cardiovascular intervention is intimal hyperplasia and constrictive remodeling, which result in vascular restenosis. Neointimal hyperplasia is characterized by proliferation and migration of smooth muscle cells. These cells also produce new extracellular matrix, leading to narrowing of vessels. Photodynamic therapy (PDT) represents one of the most promising approaches to the inhibition of intimal hyperplasia. PDT requires the interaction among 3 factors: a source of light, usually a laser, a photosensitizer and oxygen. When the inert photosensitizer absorbs light of a specific wavelength, it is activated to an excited triplet state, generating reactive oxygen species. These free radicals are able to induce apoptosis of the smooth muscle cells that had absorbed the photosensitizer; they also induce changes in the extracellular matrix, reducing cell migration. Because of continued success of PDT in inhibiting intimal hyperplasia in experimental animal models, it is now being tested in clinical trials for vascular diseases. PDT offers many advantages to the surgeon since it can act on numerous factors responsible for vascular lesions. In the future PDT could be used in helping to overcome the inherent failures associated to vascular reconstruction. This treatment modality is emerging as an encouraging therapeutic option, either alone or as an adjunct to conventional treatment. However, more detailed clinical investigation are necessary to determine its full potential.