In this thesis four studies have been described that were primarily meant to investigate the psychophysiological mechanisms underlying the relationship between depression and increased cardiac risk in patients after first time cardiac surgery, and, secondarily, to test the effectiveness of a cardiorespiratory biofeedback training in reducing cardiac risk in these patients.
Findings from the first study confirm and extend previous data on depressed patients with cardiovascular diseases by showing that also depressed patients after first time cardiac surgery had lowered vagal control on the heart, compared to patients without depression. In the second study, this relationship has been shown to be partially mediated by altered emotion regulation as a trait, and, specifically, by excessive use of suppression of emotions. Findings from the third study displayed that patients with postoperative depression had significantly greater stress response, characterized by disproportionate vagal withdrawal, specifically during unpleasant stressors, compared to nondepressed patients after surgery. More importantly, findings from the fourth study provide new evidence supporting the usefulness of a biofeedback of respiratory sinus arrhythmia training, in increasing vagal control on the heart and improving depressive symptoms.
In conclusion, the present thesis provides further information on the psychophysiological mechanisms underlying the relationship between depression and increased cardiac risk, and more importantly, yields evidence in support of the effectiveness of biofeedback training in patients after cardiac surgery
