Clinical use of the maximum radial wall strain (RWSmax) value can be considered an additional tool for physiological and plaque assessment in the diagnosis and prognosis of coronary artery disease, a new study finds. The investigation, which appears in the Jan. 8 issue of JACC: Cardiovascular Interventions, also concludes that a higher RWSmax is associated with coronary physiology and plaque morphology but shows independent prognostic value. “Distinguishable strain patterns assessed by RWSmax have also been observed between the stenotic and angiographically healthy segments, as well as between progressive and nonprogressive lesions,” said the research team, led by Seokhun Yang, MD, from Seoul National University Hospital in South Korea, and Zhiqing Wang, MD, of Shanghai Jiao Tong University and Fujian Medical University Union Hospital in Fuzhou, China. “Its derivation suggests the possibility of incorporating biomechanical properties into the diagnostic process of CAD in clinical practice, which has mainly been restricted to the research domain so far.” More findings Results from the investigation, which was also published Monday online, reveals that the mean fractional flow reserve (FFR) was 0.89±0.07 and RWSmax was 11.2% ± 2.5%. Further findings by the team based in South Korea, China and Japan noted that while 27.7% of lesions had high-risk plaque (HRP), 15.1% had FFR ≤0.80. An increase in RWSmax was associated with a higher risk of FFR ≤0.80 and HRP, which was consistent after adjustment for clinical or angiographic characteristics (all P < 0.05), the paper’s authors said. An increment of RWSmax was related to a higher risk of target vessel failure (TVF) (hazard ratio: 1.23 (95% confidence interval: 1.03-1.47); P=0.022) with an optimal cutoff of 14.25%. RWSmax >14% was a predictor of TVF after adjustment for FFR or HRP components (all P<0.05) and showed a direct prognostic effect on TVF, not mediated by FFR ≤0.80 or HRP in the mediation analysis, the paper’s authors added. When high RWSmax was added to FFR ≤0.80 or HRP, there were increasing outcome trends (all P for trend <0.001). Additional prognostic information Commenting on the findings, Hector M. Garcia-Garcia, MD, PhD, from MedStar Washington Hospital Center in Washington, D.C., and Christos V. Bourantas, MD, PhD, from Barts Health NHS Trust in London, said that RWS may provide additional prognostic information to plaque pathologic characteristics derived by computed tomographic coronary angiography (CTA). The two commentators pointed out that this was something not previously shown in palpography studies. Despite the possibilities of RWS’ role in prognosis, the editorial comment also noted that the study excluded nearly one-fourth of the studied vessels due to “insufficient angiographic image quality for RWS analysis.” “This is in line with previous studies in which large proportions of vessels were not included in the analyses because of an inability to accurately perform RWS computation, and this is likely to introduce bias and affect the reported results,” they said. Study limitations Other limitations of the study include the use of a new maximum RWS cutoff (14%) to predict lesions at risk instead of the established 12% cutoff used in previous studies. The expert commenters said that standardization of data analysis and cut points to stratify risk are essential before advocating the use of this index in clinical practice. The researchers had also defined high-risk plaques on CTA as those with plaque burden >70% and minimal luminal area (MLA) <4 mm2 According to the commentators, the selection of these criteria was not justified, commenting that in CTA, morphologic characteristics, such as napkin-ring sign, attenuated plaques, spotty calcification and positive remodeling, appear to be predictors of cardiovascular events. “It is well known that CTA has moderate agreement with intravascular imaging in assessing the luminal dimensions and limited efficacy in quantifying plaque burden,” the experts concluded. “Therefore, it remains unclear whether RWS provides incremental prognostic information to CTA and should be used to better stratify risk in patients who undergo a comprehensive assessment of plaque pathology using noninvasive imaging.” Study methodology The research team included 484 vessels (351 patients) deferred after FFR measurement with available RWS data and coronary CTA. The mean age of the patients was 66.0±9.6 years, and 69.8% were men. The mean angiographic percent diameter stenosis was 40.1% ± 14.6%, and 42.6% of lesions were on the left anterior descending coronary artery. On coronary CTA, HRP was defined as a lesion with both minimum lumen area <4 mm2 and plaque burden ≥70%. The primary endpoint was TVF, a composite of cardiac death, target vessel related myocardial infarction or target vessel ischemia-driven revascularization. Sources: Yang S, Wang Z, Park S-H, et al. Relationship of Coronary Angiography Derived Radial Wall Strain With Functional Significance, Plaque Morphology, and Clinical Outcomes. JACC Cardiovasc Interv. 2024;17: 46–56. Garcia-Garcia HM, Bourantas CV. Does Radial Wall Strain Really Carry Incremental Prognostic Information to Plaque Composition? JACC Cardiovasc Interv. 2024;17:57-59. Image Credit: flik47 – stock.adobe.com