Should NICE Guidelines Be Universally Accepted for the Evaluation of Stable Coronary Disease?

A Debate

Harvey S. Hecht; Leslee Shaw; Y.S. Chandrashekhar; Jeroen J. Bax; Jagat Narula

Disclosures

Eur Heart J. 2019;40(18):1440-1453. 

In This Article

Con: Anatomic Approaches for Stable Chest Pain Miss the Mark

For the patient at intermediate-high pretest risk of obstructive CAD, the diagnostic evaluation of a patient presenting with de novo chest pain has for decades begun with some form of stress testing. Primary goals of this index stress test are the documentation of the presence and severity of ischaemia, which are critical to interpreting a patient's pattern of symptoms and eliciting demand ischaemia. Evidence of ischaemia and its severity are critical to guide clinical decision-making notably for the prompt initiation and intensification of anti-ischaemic therapies. During stress testing, a patient's physical work capacity and an ischaemic threshold remain fundamental to interpreting patterns of chest pain during daily living and for exercise prescription purposes. This approach to the diagnostic evaluation has been the mainstay of clinical management for patients with stable CAD for more than three decades and it remains a valuable means to guide therapeutic decision-making. Within the clinical practice guideline, a variety of stress test modalities have preferred indications, which are reflective of the depth and quality of evidence supporting widespread application of ETT and stress imaging with SPECT/PET, echocardiography, and MRI.[4] The use of stress imaging has been a core means of defining CAD treatment and has been the focus of many prior trials[26,27] including the ongoing NIH-NHLBI ISCHEMIA trial.[28]

In the recent NICE update stress testing has been relegated as a second-line test for patients without documented CAD.[29,30] The impetus for this change in the NICE guidance document was the superior accuracy of CTA to detect obstructive CAD when compared with traditional stress testing modalities. It is a foregone conclusion that a (non-invasive) anatomic procedure will have significantly greater concordance with ICA. However, the concept of demand ischaemia aims to identify not a high-grade stenosis alone but functionally significant obstructive CAD. This difference is fundamental to understanding how NICE 'misses the mark' on their guidance document.

There remain several concerns regarding the use of CTA as an index procedure; with much having to do with the state-of-the-evidence. Computed tomography angiography is a relatively new procedure and standards of care have yet to be put forth from recent randomized trials[13,15–17,19] To date, the construct of a CTA-guided therapeutic strategy is not defined and accordingly several challenges exist with regards to its effective implementation. First, there was initial evidence that an index anatomic procedure leads to a higher rate of downstream ICA and revascularization when compared with index functional testing;[13] this has subsequently been disproven[18,19] but further data would be helpful. Details as to the appropriateness of follow-up invasive testing is not available[31] including the application of ischaemia measurements [either stress testing or (invasive or non-invasive) FFR measurement] to guide revascularization decision-making. On the contrary, evidence suggests that follow-up ICA occurs promptly after index CTA[32–34] Secondly, our current treatment algorithm for CAD supports index medical therapy with revascularization reserved for patients with worsening or persistent anginal symptoms. The CAD clinical practice guideline bases this recommendation on several large randomized trials, which failed to demonstrate a benefit in terms of risk reduction for coronary revascularization.[26,27] Thus, the higher rates of invasive procedure use and subsequent revascularization are concerning as they suggest that these patients will not derive a clinical outcome benefit and may lack sufficient evidence on stress-induced ischaemia to guide optimal medical therapeutic management. Finally, there is the concern that the CTA approach has eliminated functional testing, as reports do not document the use of ischaemia testing among patients with intermediate-high grade stenosis. Although much is made of the focus of ischaemia-guided revascularization, the wealth of evidence available on the presence and severity of ischaemia along with functional capabilities is fundamental to initiation and intensification of anti-ischaemic therapies. Moreover, the use of stress testing is a core component of clinical management including the tracking a patient's course for clinically worsening or persistent symptoms and the appropriate use of serial testing. For patients with CAD, identifying vascular territories with new or worsening ischaemia, vis-a-vis comparison of serial stress tests, is a means to define the acuity of change in a patient's status and supports a re-evaluation of their coronary anatomy.

Consequently, there is reason for concern regarding this drastic revision to the approach to stable chest pain within this NICE guidance document. The NICE committee's primary focus on detection of obstructive CAD disregards much of the evidence on prognostication and the effectiveness of risk stratification as well as the abundant SIHD trial evidence detailing ischaemia-guided management approaches. These ischaemia-guided management trials have failed to demonstrate a clinical outcome benefit with angiographic-guided approaches alone.[26,27,35,36] There certainly is enough evidence supporting CTA as a frontline procedure since it has demonstrated similar effectiveness and a wealth of prognostic evidence, as based on large multicentre trials and multinational registry data.[18,19,37] The integration of ischaemia testing, however, has yet to be fully elucidated. It remains vital to patient care that CTA-guided care incorporate timely ischaemia testing to assess the functional significance of a documented coronary stenosis. Although data is available with CT-derived fractional flow reserve measurements, its accuracy is reportedly suboptimal (46%) within the range of values from 0.7 to 0.80; critical values for revascularization decision-making,[38] With an ever-increasing evidence base as to the prognostic significance of high-risk plaque features (e.g. low attenuation plaque or positive remodelling), clinical trial evidence should be forthcoming as to therapeutic intervention trials,[39–41] particularly, the use of statins for patients with evidence of a large burden of non-calcified plaque. These trials could help to solidify the role of CTA to guide prevention and lifestyle modifications. In lieu of this evidence, it will be important for NICE to document appropriate use of invasive procedures and to foster educational initiatives on ischaemia-guided management. An evaluation algorithm should be forthcoming that provides guidance to physicians as to the timely and targeted use of ischaemia testing for those patients undergoing an index CTA evaluation. Learning from our prior evidence is important so that we do not recreate or eliminate important standards of care. Lessons learned from the past include the importance of integrating physiology measures with anatomy as fundamental to caring for the patient with CAD. For the NICE, it is important to understand that there is more to SIHD care than detection of obstructive CAD. To improve patient outcomes, we must incorporate guided treatment strategies which effectively reduce the burden of symptoms and improve patient outcomes.

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