Does pleurotomy during internal mammary artery harvest increase post-op issues?

Pleurotomy. No, during open heart surgery a chest tube will reinflate the lung and it usually heals rather quickly.
It may. Based on studies pleurotomy seems to increase rates of atelectasis (lung colapse) and pleural effusions (fluid around the lungs), although no impact on clinical outcome or length of hospital stay has been demonstrated.