ACE Inhibitors, Congestive Heart Failure, and ICD-9-CM Codes

In examining the conclusions of Stafford et al,¹ I feel the International Classification of Diseases, Ninth Revision (ICD-9-CM) codes that they used to identify cases of congestive heart failure should be examined.²

The specified codes that Stafford et al used in their analysis include the 404 series, which pertains to hypertensive heart disease and renal disease, and the 402 series, which pertains solely to hypertensive heart disease. Both diagnostic groups may be expected to have a substantial proportion of cases of congestive heart failure secondary to diastolic, not systolic, dysfunction. By the American College of Cardiology/American Heart Association³ guidelines, diastolic dysfunction is best treated with diuretics and nitrates, with angiotensin-converting enzyme (ACE) inhibitors being one of several acceptable secondary agents. In view of the listed precautions for the use of ACE inhibitors with diuretics in patients with renal insufficiency, substantially lower use of ACE inhibitors would also be expected for patients with diagnoses in the 404 series.