What the guidelines say
The 6-year-old U.S. guidelines on the diagnosis and management of patients with stable ischemic heart disease are clearly out of date on the topic of silent ischemia (Circulation. 2014 Nov 4;130[19]:1749-67). The recommendations are based on expert opinion formed prior to the massive amount of new evidence that has since become available. For example, the current guidelines state as a class IIa, level of evidence C recommendation that exercise or pharmacologic stress can be useful for follow-up assessment at 2-year or greater intervals in patients with stable ischemic heart disease with prior evidence of silent ischemia.
“This is a very weak recommendation. The class of recommendation says it would be reasonable, but in the absence of an evidence base and in light of newer information, I’m not sure that it approaches even a class IIa level of recommendation,” according to Dr. O’Gara.
The 2019 European Society of Cardiology guidelines on chronic coronary syndromes are similarly weak on silent ischemia. The European guidelines state that patients with diabetes or chronic kidney disease may have a higher burden of silent ischemia, might be at higher risk for atherosclerotic cardiovascular disease events, and that periodic ECGs and functional testing every 3-5 years might be considered.
“Obviously there’s a lot of leeway there in how you wish to interpret that,” Dr. O’Gara said. “And this did not rise to the level where they’d put it in the table of recommendations, but it’s simply included as part of the explanatory text.”
What’s coming next in stable ischemic heart disease
“Nowadays all the rage has to do with coronary microvascular dysfunction,” according to Dr. O’Gara. “I think all of the research interest currently is focused on the coronary microcirculation as perhaps the next frontier in our understanding of why it is that ischemia can occur in the absence of epicardial coronary disease.”
He highly recommended a review article entitled: “Reappraisal of Ischemic Heart Disease,” in which an international trio of prominent cardiologists asserted that coronary microvascular dysfunction not only plays a pivotal pathogenic role in angina pectoris, but also in a phenomenon known as microvascular angina – that is, angina in the absence of obstructive CAD. Microvascular angina may explain the roughly one-third of patients who experience acute coronary syndrome without epicardial coronary artery stenosis or thrombosis. The authors delved into the structural and functional mechanisms underlying coronary microvascular dysfunction, while noting that effective treatment of this common phenomenon remains a major unmet need (Circulation. 2018 Oct 2;138[14]:1463-80).
Dr. O’Gara reported receiving funding from the National Heart, Lung, and Blood Institute; from Medtronic in conjunction with the ongoing pivotal APOLLO transcatheter mitral valve replacement trial; from Edwards Lifesciences for the ongoing EARLY TAVR trial; and from Medtrace Pharma, a Danish company developing an innovative form of PET diagnostic imaging.