Andrew D. Bowser
June 17, 2020
For diabetes patients with no cardiovascular symptoms despite certain risk factors, incorporating coronary calcium scoring into a silent myocardial ischemia screening algorithm may be an effective and cost-conscious strategy that avoids missed coronary stenoses suitable for revascularization, results of a recent study suggest.
Zero patients in need of revascularization were missed in a risk stratification model in which screening for silent myocardial ischemia (SMI) was done only for patients with peripheral artery disease, severe nephropathy, or a high coronary artery calcium (CAC) score, according to investigator Paul Valensi, MD.
In practical terms, that means stress myocardial scintigraphy to detect SMI could be reserved for patients with evidence of target organ damage or a CAC score of 100 or higher, according to Dr. Valensi, head of the department of endocrinology, diabetology, and nutrition at Jean Verdier Hospital in Bondy, France.
"The strategy appears to be a good compromise, and the most cost effective strategy," Dr. Valensi said in a presentation of the results at the virtual annual scientific sessions of the American Diabetes Association.
Utility of CAC Scoring in Diabetes
This algorithm proposed by Dr. Valenti and colleagues is a "reasonable" approach to guide risk stratification in asymptomatic diabetes patients, said Matthew J. Budoff, MD, professor of medicine and director of cardiac CT at Harbor-UCLA Medical Center in Torrance, Calif.
"Calcium scoring could certainly help you identify those patients (at increased risk) as a first-line test, because if their calcium score is zero, their chance of having obstructive disease is probably either zero or very close to zero," Dr. Budoff said in an interview.
Using CAC scores to assess cardiovascular risk in asymptomatic adults with diabetes was supported by 2010 guidelines from the American College of Cardiology and the American Heart Association, Dr. Budoff said, while 2019 guidelines from the European Society of Cardiology (ESC) describe CAC score combined with CT as a potential risk modifier in the evaluation of certain asymptomatic patients with diabetes.
"We are starting to see that we might be able to understand diabetes better and the cardiovascular implications by understanding how much plaque (patients) have at the time that we see them," Dr. Budoff said in a presentation on use of CAC scans he gave earlier at the virtual ADA meeting.
In the interview, Dr. Budoff also noted that CAC scores may be particularly useful for guiding use of statins, PCSK9 (proprotein convertase subtilisin kexin 9) inhibitors, or other treatments in patients with diabetes: "There are a lot of therapies that we can apply, if we knew somebody was at higher risk, that would potentially help them avoid a heart attack, stroke, or cardiovascular death," he said.
CAC Scoring and Coronary Artery Stenoses
Although about 20% of patients with type 2 diabetes have SMI, screening for it is "debated," according to Dr. Valensi.
The recent ESC guidelines state that while routine screening for coronary artery disease in asymptomatic diabetics is not recommended, stress testing or coronary angiography "may be indicated" in asymptomatic diabetics in the very-high cardiovascular risk category.
That position is based on a lack of benefit seen with a broad screening strategy, the guidelines say, possibly due in part to low event rates in randomized controlled trials that have studied the approach.
Using CAC scoring could change the equation by helping to identify a greater proportion of type 2 diabetics with SMI, according to Dr. Valensi.
"The role of the CAC score in the strategy of detection of SMI needs to be defined, and this role may depend on the a priori cardiovascular risk," he said.
Dr. Valensi and colleagues accordingly tested several different approaches to selecting asymptomatic diabetic patients for SMI screening to see how they would perform in finding patients with coronary stenoses eligible for revascularization.
Their study included 416 diabetes patients with diabetes at very high cardiovascular risk but with no cardiac history or symptoms. A total of 40 patients (9.6%) had SMI, including 15 patients in which coronary stenoses were found; of those, 11 (73.5%) underwent a revascularization procedure.
They found that, by performing myocardial scintigraphy only in those patients with peripheral artery disease or severe nephropathy, they would have missed 6 patients with coronary stenosis suitable for revascularization among the 275 patients who did not meet those target organ damage criteria.
By contrast, zero patients would have been missed by performing myocardial scintigraphy in patients who either met those target organ damage criteria, or who had an elevated CAC score.
"We suggest screening for SMI, using stress myocardial CT scanning and coronary stenosis screening, only the patients with peripheral artery disease or severe nephropathy or with a high CAC score over 100 Agatston units," said Dr. Valensi.
Dr. Valensi reported disclosures related to Merck Sharp Dohme, Novo Nordisk, Pierre Fabre, Eli Lilly, Bristol-Myers Squibb, AstraZeneca, Daiichi-Sankyo, and others. Coauthors provided no disclosures related to the research. Dr. Budoff reported that he has served as a paid consultant to GE.