Cardiac computed tomographic angiography (CTA) is an accurate noninvasive test for diagnosing coronary artery disease (CAD). To investigate whether increasing use of CTA is correlated with left heart catheterization (LHC) rates, we performed a retrospective review of existing outpatient and inpatient catheterization lab and CTA electronic medical records from July 1, 2004 to June 30, 2008. Comparing the previous 2 years (July 2004-June 2006) to the 2 years after addition of CTA (July 2006-June 2008), monthly LHC rates decreased 20 +/- 6% (p = 0.08) and percutaneous coronary intervention (PCI) rates decreased 47 +/- 6% (p<0.001). Cardiology clinic volume declined 34%. CTA rates increased 64 +/- 7% (p<0.001). Radionuclide myocardial perfusion scan (MPS) usage remained stable. Despite increased utilization over the past 2 years, CTA was not correlated with significantly reduced LHC rates. The decline of outpatient LHC rates at our institution over 4 years is mainly influenced by decreasing outpatient Cardiology clinic volume.