Accupril is an angiotensin-converting enzyme (ACE) inhibitor. ACE is involved in certain chemical reactions that constrict (narrow) blood vessels and cause sodium and fluid retention by the kidney. This can cause an increase in blood pressure. ACE inhibitors lower elevated blood pressure by interfering with ACE and cause blood vessels to relax (widen). Blood flows more freely and at a lower pressure. ACE inhibitors ... increase the heart's ability to pump blood in some types of heart failure.