Intravascular Palpography for Vulnerable Plaque Assessment

Intravascular Palpography for Vulnerable Plaque Assessment Johannes A. Schaar, Anton F. W. van der Steen, Frits Mastik, Radj A. Baldewsing, Patrick W. Serruys Palpography assesses local mechanical tissue properties. In vitro validation using human specimens revealed significant difference in strain between fibrous and fatty tissue. High strain at the lumen has 88% sensitivity and 89% specificity for identifying vulnerable plaques. In vivo validation in animals showed higher strain in fatty plaques than in fibrous plaques. High strain at the lumen had high predictive value to identify macrophages. Three-dimensional palpography showed that patients with myocardial infarction or unstable angina have more high strain spots in their coronaries than patients with stable angina. In conclusion, palpography may become a decision tool for identifying vulnerable plaques. Palpography assesses the local mechanical properties of tissue using the deformation caused by the intraluminal pressure. The technique was validated in vitro using diseased human coronary and femoral arteries. Especially between fibrous and fatty tissue, a highly significant difference in strain (p = 0.0012) was found. Additionally, the predictive value to identify the vulnerable plaque was investigated. A high-strain region at the lumen vessel wall boundary has 88% sensitivity and 89% specificity for identifying these plaques. In vivo, the technique is validated in an atherosclerotic Yucatan minipig animal model. This study also revealed higher strain values in fatty than in fibrous plaques (p < 0.001). The presence of a high-strain region at the lumen-plaque interface has a high predictive value to identify macrophages. Patient studies revealed high strain values (1% to 2%) in noncalcified plaques. Calcified material showed low strain values (0% to 0.2%). With the development of three-dimensional palpography, identification of weak spots over the full length of a coronary artery becomes available. Patients with myocardial infarction or unstable angina have more high-strain spots in their coronary arteries than patients with stable angina. In conclusion, intravascular palpography is a unique tool to assess lesion composition and vulnerability. Three-dimensional palpography provides a technique that may develop into a clinically available tool for decision making to treat hemodynamically nonsignificant lesions by identifying vulnerable plaques. The clinical utility of this technique is yet to be det