To further investigate if the increased risk of death associated with digoxin and/or beta-blockers was influenced by HF, abnormal kidney function, and angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs), a post-hoc interaction analysis was performed to evaluate if the risk was modified by different sub-groups of patients. The gene discussed is ACE; the disease is hydrops fetalis.