Contribution of the Optical Coherence Tomography in Calcified Lesions

Abstract

Coronary artery calcification is a complex process found predominantly in the elderly population. Coronary angiography frequently lacks sensitivity to detect, evaluate and quantify these lesions. Yet calcified lesions are considered stable, it remains associated with a higher rate of peri procedural complications during percutaneous coronary intervention (PCI) including an increased risk of stent under expansion and struts mal apposition leading to poor clinical outcome. Intracoronary imaging (Intravascular Ultra Sound (IVUS) and Optical Coherence Tomography (OCT)) allows better calcified lesions identification, localization within the coronary artery wall (superficial or deep calcifications), quantification. This lesions characterization allows a better choice of dedicated plaque-preparation tools (modified balloons, rotational or orbital atherectomy, intravascular lithotripsy) that are crucial to achieve optimal PCI results. OCT could also assess the impact of these tools on the calcified plaque morphology (plaque fracture, burring effects…). An OCT-guided tailored PCI strategy for calcified lesions still requires validation by clinical studies which are currently underway.

Keywords: coronary calcification; intravascular lithotripsy; optical coherence tomography; optical frequency domain imaging - rotational atherectomy; orbital atherectomy.

Fig. 1.

Examples of calcified lesions in Optical Frequency Domain imaging (OFDI). (A) thick calcified lesion between 1 and 5 o’clock. (B) annular calcified plaque. (C) Deep calcified lesions between 11 and 1 o’clock and between 3 and 7 o’clock. (C’) long axis view of large calcified plaque in lower part of the panel. (D) massive deep and annular calcified lesions. (E) calcified nodule with superficial (luminal) calcification between 11 and 2 o’clock with cauliflower aspect and deep calcification at the opposite. (F) Annular calcification lesion with variable depth.

Fig. 2.

PCI and calcified lesions in OCT. (A,A’) massive calcified nodule between 8 and 10 o’clock (represented in white on A’ panel) leading to significant under-expansion of the stent (in yellow dot line) and mal apposition of the nearby struts. (B) Localized stent mal apposition (between 1 and 3 o’clock) after intravascular lithotripsy with visible plaque fracture at 1 o’clock and small intimal dissection at 10 o’ clock. (C) Moderate intra stent restenosis with significant stent under expansion next to an annular calcified plaque in short axis (C) and long axis view (C’). PCI, percutaneous coronary intervention; OCT, optical coherence tomography.

Fig. 3.

Example of high risk calcified lesion with thickness $\mathrm{>}$0.5 mm, length $\mathrm{>}$5 mm and angular extension $\mathrm{>}$180°.

Fig. 4.

Representative comparison between calcified nodule and red thrombus in OCT. (A) typical aspect of red thrombus between 7 and 10 o’clock with significant attenuation of the signal. The normal aspect of the artery in 3 layers is clearly visible between 10 and 7 o’clock. (B) Calcified nodule with similar aspect in OCT (signal attenuation). The normal aspect of the wall is not present with an important calcified plaque between 6 and 11 o’clock. (C) Another example of calcified nodule at 9 o’clock and semicircular calcified plaque between 6 and 1 o’clock. (D) Another example of protrusing calcified lesion with lower signal attenuation and “cauliflower” aspect in short axis view. (E) Long axis view of the same lesion with abrupt transition between the calcified nodule and the normal aspect of the wall on the left side of the panel. (F) Post PCI imaging with moderate stent under expansion between 1 and 3 o’clock next to a calcified nodule. PCI, percutaneous coronary intervention; OCT, optical coherence tomography.

Fig. 5.

Intra coronary imaging after calcified plaques preparation. (A,A’) shows the effect of rotational atherectomy with a gutter aspect at the lower part of the artery. The burr is represented in (A’) by the grey circle. (B) Typical aspect of calcified plaque fractures at 1, 5 and 10 o’clock after intravascular lithotripsy. The fracture at 1 and 5 o’clock are associated with deep dissections. (C) Intimal dissection at 12 o’clock (white arrow) after calcified lesion preparation by orbital atherectomy.