Improved neoangiogenesis in transmyocardial laser revascularization combined with angiogenic adjunct in a pig model

Recent research has revealed neoangiogenesis as a basic phenomenon in transmyocardial laser revascularization (TMLR). Theoretically, myocardial neoangiogenesis could be further enhanced by the addition of angiogenic growth factors. Triads of TMLR channels were created in the lateral wall of the left ventricles of 12 pigs (mean body weight 73±5 kg), using a holmium:yttrium—aluminium garnet (YAG) laser. The animals were allocated randomly either to receive an injection of 100 µg of a bovine bone-derived growth factor mixture within the triads (n = 6), or to a control group (n = 6). Animals were killed 1 month later. Capillary and arteriolar densities were determined by computed morphometric analysis of histological sections of the triads. The capillary density of myocardial areas within the triads was significantly greater in the group receiving the bovine bone-derived growth factor mixture than in the control group (14.3±3.5/mm² and 5.7±1.4/mm² respectively; P < 0.001). The difference was also significant when considering arteriolar density (0.7±0.4/mm² and 0.2±0.1/mm² respectively; P < 0.001). For comparison, capillary and arteriolar densities of the TMLR channel scars were 48.7±9.7 and 1.9±0.5/mm² respectively in the angiogenic group, and 46.3±13.7 and 2.3±1.3/mm² respectively in the control group (no significant differences). These results demonstrate that the addition of angiogenic factors to TMLR stimulates neoangiogenesis significantly in the areas adjacent to the channels, but not within the channel scars. The latter are themselves strongly vascularized. Hence this combined approach, potentiating the effect of TMLR by establishing vascular connections between the neovessels of the channel scars, has the potential for improved clinical outcome.