Volume 194 - Issue 12
A new algorithm for the management of stable coronary artery disease incorporating CT coronary angiography and fractional flow reserve: how we can improve outcomes and reduce costs
Authors: Nathan Better, Myles B Webb, David L Prior, Steven A Unger and George Larcos
Med J Aust 2011; 194 (12): 666-669. || doi: 10.5694/j.1326-5377.2011.tb03167.x
Published online: 20 June 2011
Published online: 20 June 2011
To the Editor: Harper and Ko stress the importance of differentiating the presence of atherosclerosis from ischaemia,1 a concept that has been well understood for years. We agree that identifying myocardial ischaemia is important in the management of atherosclerosis; there are a variety of well validated non-invasive tools for this, including exercise electrocardiography, stress echocardiography, and nuclear myocardial perfusion imaging (MPI).
However, we have concerns about some of the sweeping changes suggested by the authors — in particular, replacing nuclear MPI with stress echocardiography. While published studies report similar accuracy for these modalities, it is clear that each has strengths and weaknesses. Stress echocardiography is an excellent tool that will often suffice but it is operator-dependent, while MPI is more accurate for single-vessel ischaemia. It is well known that a diagnostic stress echocardiogram cannot be achieved in some patients, so an alternative modality may be required. This is particularly problematic in Australia, where there is no mechanism in place to fund the use of ultrasound contrast imaging.
MPI remains a widely accepted technique globally, with a substantial evidence base to support its diagnostic and prognostic impact. For instance, a negative MPI study is generally associated with a cardiac event rate of < 1% in the following year.2 Further, its role in directing the mode of treatment on the basis of extent of ischaemia and its cost-effectiveness as the “gatekeeper” to cardiac catheterisation have been amply demonstrated.3
The use of radiation in medical procedures is always subject to the ALARA (as low as reasonably achievable) principle, and prescribed doses in Australia are typically lower than those quoted in the American literature cited by Harper and Ko. Recent advances in hardware and software with MPI have achieved additional gains in reducing radiation exposure.4 The cost of MPI is greater than stress echocardiography, but remains less than angiography and fractional flow reserve (FFR) measurement. Further, Harper and Ko’s proposed cost savings will not be realised with their call for an increased use of computed tomography coronary angiography and FFR measurement.
The job of a good clinician is to choose the right test for the patient; in some cases this is a stress echocardiogram but it is often an MPI study, as supported by international guidelines.5 Thus, readers should be mindful that Harper and Ko’s views about replacing nuclear stress tests with stress echocardiography and abolishing the Medicare item number for nuclear stress tests are personal and may be contrary to sound evidence.
References
- Harper RW, Ko BS. A new algorithm for the management of stable coronary artery disease incorporating CT coronary angiography and fractional flow reserve: how we can improve outcomes and reduce costs. Med J Aust 2011; 194: 186-189. 0_CBBGBDDJ
- Hachamovitch R, Hayes S, Friedman JD, et al. Determinants of risk and its temporal variation in patients with normal stress myocardial perfusion scans: what is the warranty period of a normal scan? J Am Coll Cardiol 2003; 41: 1329-1340. 0_i1095852
- Freeman MR. Growing evidence that radionuclide imaging identifies management strategies that improve outcome. J Nucl Cardiol 2009; 16: 844-845. 0_i1095854
- Cerqueira MD, Allman KC, Ficaro EP, et al. Recommendations for reducing radiation exposure in myocardial perfusion imaging. J Nucl Cardiol 2010; 17: 709-718. 0_i1095856
- Brindis RG, Douglas PS, Hendel RC, et al. ACCF/ASNC appropriateness criteria for single-photon emission computed tomography myocardial perfusion imaging (SPECT MPI): a report of the American College of Cardiology Foundation Quality Strategic Directions Committee Appropriateness Criteria Working Group and the American Society of Nuclear Cardiology endorsed by the American Heart Association. J Am Coll Cardiol 2005; 46: 1587-1605. 0_i1095860