Researchers found that anxiety independently raises health risks in patients with coexisting depression.
Risks of depression in heart disease are well understood, but more attention must be paid to the harm caused by anxiety, they said.
A team from Duke University in North Carolina measured levels of anxiety and depression among 934 patients with CHD who were due to undergo a cardiac catheterisation.
Patients with anxiety were more likely to be sleeping less and have a history of hypertension. Those with depression had a reduced left ventricular ejection fraction and greater rates of heart failure.
Patients who had both were more likely to be smokers.
There were 133 deaths during the three years after the procedures. Higher anxiety levels led to a 2.3 times greater risk of mortality after accounting for established risks such as age, heart failure and renal disease. Depression led to a 2.2-fold raised mortality risk.
Patients with both anxiety and depression faced a 3.1 times higher risk than those with neither.
Anxiety is believed to cause elevated nervous system activity, inflammation and hypertension.
Lead author Dr Lana Watkins of Duke University Medical Centre said clinicians should 'assess patients for both anxiety and depression, and continue to monitor these symptoms on a regular basis'.
She added: 'It's now time for anxiety to be considered as important as depression'.