There is a large body of evidence that high or prolonged stress, depression and low social support are predictive of coronary artery health [1–4]. In particular, depression has been identified as a psychosocial factor with enormous potential to influence the course and outcome of coronary artery disease [3, 5, 6]. Despite the empirical evidence that depression increases the risk of cardiovascular morbidity and mortality itself, there is no common accepted model that describes the underlying mechanisms [7, 8]. Both direct and indirect pathways have been put forward. On one hand, direct influences of depression on physiological factors may lead to atherosclerosis or coronary events. On the other hand, depression leads to an increase in coronary risk factors (that is, inflammation), which in turn may cause heart disease. Finally, there may be some underlying factors (that is, distress, personality, social environment and health behavior) influencing the risk for both depression and heart disease . Psychosocial and behavioral factors correlate both with depression and heart disease. Depression is associated with poor health behavior, maladaptive coping style, social isolation, and chronic life stress . Behavioral risk factors, such as smoking, low physical activity, a poor diet, and the failure to adhere to medical recommendations mediate the relationship of depressive disorders with heart disease [11, 12].
Several studies have focused on the treatment of depressive symptoms in cardiac patients. The study, enhancing recovery in coronary heart disease patients with depres-sion (ENRICHD), examined the efficacy of psychotherapy (cognitive-behavioral approach) on depression . The effect size (ES) of short-term efficacy in comparison to the control group were small (ES = 0.35), and disappeared on long-term follow-up. Furthermore, the Canadian cardiac randomized evaluation of antidepressant and psychotherapy efficacy (CREATE) study, investigating the benefit of an interpersonal psychotherapy (IPT) , only detected a tendency towards a reduced depression level in the IPT group compared to the non-treated group (ES = 0.20). Larger ES over 0.70 were reported for psychotherapy in depressed but otherwise healthy people. However, these effects might be overestimated due to publication bias .
One of the greatest challenges of a psychotherapeutic approach to support treatment success of cardiac patients with depression is the time and resource intensity of most traditional approaches of treatment delivery. The opportunity to develop new forms of intervention, for example, web-based treatment, has never been more feasible. To date, there is sparse evidence that psychotherapy influences the progress of heart disease.
Many people are now web-literate and many have access to the Internet. Today, internet-based technologies are used at almost all levels of psychosocial services. Apart from possible cost-effectiveness and the fact that web-based interventions can flexibly be used independently of time and place, a major advantage of the web-based approach is that it offers support to people who may not otherwise seek or reach treatment.
Over recent years, web-based treatments have been used with success to promote health [16, 17] and have shown promising outcomes for several psychiatric conditions, including depression [18–20]. Particularly web-based guided self-help approaches, in which the presentation of a web-based self-help program is combined with minimal but regular therapist contact via e-mail, have shown promising results. Emerging evidence from meta-analyses [19, 21] and from a reanalysis of data across trials  suggests a superiority of guided versus unguided self-help, both in terms of efficacy and drop-out rates.
There are only a few web-based interventions for cardiac patients that have been developed and evaluated so far . Preliminary results confirm that a web-based intervention for cardiac patients can help to change psychosocial risk factors. Web-based interventions can reduce symptoms of depression [24, 25] and anxiety [25, 26] and help to increase social support . Besides this, cardiac patients report improvements in managing their physical condition by knowing more about their disease, and therefore increase their perception of control  and change their health behavior [29, 30]. In addition, improvements in quality of life [27, 31, 32], and even improvements in adherence due to the presentation of a cardiac-specific information tool [25, 33] have been reported.
There are only two web-based psychological treatment programs to have been developed so far: a specific web-based distress management program for patients with cardioverter defibrillator  and a web-based treatment for cardiac patients with depression .
In consideration of the difficulties of treating cardiac patients, this intervention study InterHerz strikes a new path by implementing a proven and promising web-based approach called Deprexis in a somatically ill patient group with depression [36–38]. Deprexis has been developed to reduce depressive symptoms in physically healthy patients with a depressive disorder. To our knowledge, this is the only psychological treatment for German-speaking patients with depression, and in contrast to other web-based tools, it integrates different psychotherapeutic approaches .