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
Author: Peter Karamoskos
Med J Aust 2011; 194 (12): 666-669. || doi: 10.5694/j.1326-5377.2011.tb03166.x
Published online: 20 June 2011
Published online: 20 June 2011
To the Editor: Although Harper and Ko’s effort at proposing an algorithm1 to reduce unnecessary cardiac catheterisation and stenting is laudable, it is concerning that they advocate investigating patients with stable coronary artery disease (CAD) using computed tomography coronary angiography (CTCA), with an algorithm, furthermore, that has not been validated in terms of patient outcomes.
The COURAGE trial demonstrated that percutaneous coronary intervention (PCI) provided no survival advantage or reduction in myocardial infarction over 5 years of follow-up compared with optimal medical management in patients with chronic stable angina.2 PCI provided a relative symptomatic benefit only within the first 3 years. Therefore, it is debatable whether imaging most of these stable patients — much less catheterising them — provides any enduring favourable patient outcomes.
For those who do require intervention, fractional flow reserve (FFR) measurement does obviate unnecessary stenting during a cardiac catheterisation. But why perform CTCA — which cannot diagnose ischaemia — in the first place, only to then perform an expensive invasive catheterisation to compensate for it? Why not diagnose ischaemia with an initial non-invasive stress test (nuclear or echocardiography) and only proceed to catheterisation if revascularisation is warranted, thus also lessening the radiation dose? Modern gamma cameras allow nuclear stress studies with radiation doses as low as 2–3 mSv. Yes, CTCA can (as opposed to does) achieve comparable doses with prospective gating, but without the left-ventricular function analysis that nuclear or echocardiography studies provide. Advocating the elimination of the rebate for nuclear stress studies is thus premature, if not ill informed.
Harper and Ko’s algorithm relies on the assumption that medical therapy is appropriate in asymptomatic patients for any degree of coronary atherosclerosis, hence justifying the use of CTCA for its detection. However, there is considerable uncertainty about the benefits of medical therapy for primary prevention in low-risk patients.3 Furthermore, the use of CTCA has not been validated as a determinant of appropriate medical management leading to favourable patient outcomes. This contention remains speculative.
Indeed, contrary to the claims of CTCA supporters, the United States Centers for Medicare and Medicaid Services has declared that
there is uncertainty regarding any potential health benefits or patient management alterations from including coronary CTA [computed tomography angiography] in the diagnostic workup of patients who may have CAD. No adequately powered study has established that improved health outcomes can be causally attributed to coronary CTA ... the body of evidence is of overall limited quality and limited applicability ... in community practice.4
Consequently, the technology also poses significant potential to unnecessarily increase the population radiation burden.5
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.
- Boden WE, O’Rourke RA, Teo KK, et al; COURAGE Trial Research Group. Optimal medical therapy with or without PCI for stable coronary disease. N Engl J Med 2007; 356: 1503-1516. 0_CBBJHJHD
- Taylor F, Ward K, Moore THM, et al. Statins for the primary prevention of cardiovascular disease. Cochrane Database Syst Rev 2011; (1): CD004816. http://www2.cochrane.org/reviews/en/ab00481 6.html (accessed Mar 2011).
- Phurrough SE, Salive ME, Baldwin J, Chin J. Decision memo for computed tomographic angiography (CAG-00385N). Baltimore: Centers for Medicare & Medicaid Services, 2008. http://www.cms.gov/medicare-coverage-database/details/nca-decision-memo.aspx?NCAId=206&ver=17&NcaName=Computed+Tomographic+Angiography&DocID=CAG-00385N (accessed Mar 2011).
- Redberg RF, Walsh J. Pay now, benefits may follow — the case of cardiac computed tomographic angiography. N Engl J Med 2008; 359: 2309-2311. 0_CBBIJDEC