Figure 1. Response to Stressors.

When a frail patient is subjected to a stressor, such as cardiac surgery, there is a reduced ability to return to the prior level of functioning and frequently negative outcomes. They tend to attend a new “baseline”. As these stressors become more severe or more often, the baseline status continues to trend down. Patients with pre-existing vulnerabilities may undergo cardiac surgery at lower functional levels (i.e. cardiac surgery stress is shifted right).