PCI in the calcified lesion

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Thomas Tu, M.D.; Brian C. Bigelow, M.D.

Challenges of Calcified Lesions

• Heavily calcified lesions add complexity to a percutaneous coronary intervention.

• The presence of coronary calcification reduces the compliance of the vessel, and it may predispose calcified plaque–normal wall interfaces to dissections after balloon angioplasty.

• The presence of coronary calcification also reduces the ability to cross chronic total occlusions. In severely calcified lesions, stent strut expansion is inversely correlated with the circumferential arc of calcium.

• The presence of extensive coronary calcification poses unique challenges for PCI as calcium in the vessel wall leads to irregular and inflexible lumens. It also makes the delivery of guidewires, balloons, and stents much more challenging.

• Extensive coronary calcification also renders the vessel wall rigid, necessitating higher balloon inflation pressures to obtain complete stent expansion, and occasionally leading to “undilatable” lesions that resist any achievable balloon expansion pressure.

Calcification in Saphenous Vein Grafts (SVGs)

Calcification noted within SVGs are generally within the reference vessel wall rather than within the lesion, and they are often associated with older graft age, insulin–dependent diabetics, and smoking.

Angiographic Evaluation

Coronary artery calcium is an important marker for coronary atherosclerosis. Conventional coronary angiography has limited sensitivity for the detection of smaller amounts of calcium, and has moderate sensitivity for the detection of extensive lesion calcium (sensitivity 60% and 85% for three- and four-quadrant calcium, respectively).

Treatment

There are a variety of diagnostic and treatment options for calcified lesions. Better early outcomes may be achieved by using a multi-device interventional strategy.

Percutaneous Transluminal Coronary Angioplasty (PTCA)

PTCA is an invasive cardiologic therapeutic procedure to treat the stenotic (narrowed) coronary arteries of the heart. The term balloon angioplasty is commonly used to describe this procedure, which describes the inflation of a balloon within the coronary artery to crush the plaque into the walls of the artery.

In the treatment of calcified lesions with PTCA, certain considerations must be made. For one, interventional cardiologists should consider using hydrophilic guidewires, as heavy calcification may make wire advancement difficult. Also, calcified plaques usually require higher balloon pressures to fully expand than normal plaques. Because of this, non-compliant balloons may be a better choice than compliant or semi-compliant balloons. Differential expansion of compliant or semi-compliant balloons inside a particular lesion may jeopardize less diseased segments if the balloon expands greater than the vessel's native diameter. On the contrary, non-compliant balloons allow for a more uniform expansion at high pressures and therefore may be a better choice to apply focused pressure at the calcified plaque. Another option is to place a second "buddy" wire adjacent to the balloon to improve the ability to dilate calcified plaque.

If pre-dilatation fails to fully expand a calcified stenosis, then the risks and benefits of stent deployment should be carefully considered due to the risk of incomplete expansion and future restenosis.

Intravascular Ultrasound (IVUS)

IVUS is a medical imaging methodology that uses a specially designed catheter with a miniaturized ultrasound probe attached to the distal end of the catheter. The proximal end of the catheter is attached to computerized ultrasound equipment. It allows the application of ultrasound technology to see from inside blood vessels out through the surrounding blood column, visualizing the endothelium (inner wall) of blood vessels in living individuals. IVUS is used in the coronary arteries to determine the amount of atheromatous plaque built up at any particular point in the epicardial coronary artery.

While coronary angiography by fluroscopy is limited in its detection and severity assessment of coronary calcification, IVUS can assess the extent of calcification and may be particularly useful for instances when the reason for poor balloon expansion is uncertain. Although this approach has its advantages over angiography, heavy involvement of superficial, sub-endothelial calcification may require rotational atherectomy.

Cutting Balloon and FX MiniRailTM

A cutting balloon is an angioplasty device used in percutaneous coronary interventions. It has a special balloon tip with small blades, that are activated when the balloon is inflated. This procedure is different from rotational atherectomy, in which a diamond tipped device spins at high revolutions to cut away calcific (chalky) atheroma usually prior to coronary stenting.

This technique can be useful in treating calcified lesions because the microsurgical blades on the surface of the balloon may help to score and modify calcified plaques. Generally, if a cutting balloon will cross the lesion, a stent can be delivered. Although this technique has its advantages, there are certain additional considerations that must be made before deciding to use this procedure. For one, despite their usefulness, these balloons are often more difficult to deliver past tortuous or calcified segments, so extra care must be used. Also, there were no significant differences observed in rates of restenosis when using this procedure.

Rotational Atherectomy

Rotational atherectomy is a minimally invasive method of removing plaque and blockages from an artery and subsequently widening arteries that have been narrowed by arterial disease. Unlike angioplasty and stents of blocked arteries that simply push blockages aside into the wall of the artery, rotational atherectomy involves inserting a thin catheter with a rotating blade on its end into the artery. The rotating edge is used to remove plaque buildups, thereby opening the artery and restoring normal blood flow.

Rotational atherectomy is frequently employed following unsuccessful pre-dilating PTCA to perform plaque modification. This procedure facilitates PTCA by creating micro-fractures, removing calcified plaque, and increasing vessel compliance. Despite its usefulness in treating calcified lesions, certain precautions should be taken. In an effort to limit the risk of vessel laceration, smaller diameter burrs are now preferred. A general guideline to use is that the initial burr to luminal ratio should be 1:2. Additional caution should be taken when a coronary dissection is present, as rotational atherectomy may propagate the dissection.

• Rotational atherectomy in severe lesion calcification: Rotational atherectomy is the preferred pretreatment method in patients with severe lesion calcification, particularly ostial lesions, and facilitates the delivery and expansion of coronary stents by creating microdissection planes within the fibrocalcific plaque. Yet even with these contemporary methods, the presence of moderate or severe coronary calcification is associated with reduced procedural success and higher complication rates, including stent dislodgement.

• Rotational atherectomy in mild-moderate calcifications: In less severely calcified lesions, no differences in restenosis rates were found after paclitaxel-eluting stent implantation in calcified and non-calcified vessels.

Directional Coronary Atherectomy (DCA)

DCA involves inserting a thin, flexible catheter with a small blade on its end into the artery, which cuts off plaque buildups. These plaque shavings are caught with the catheter and are subsequently removed from the artery.

One problem that may arise during the procedure is that heavy calcification proximal to the target lesion may limit deliverability of the device and its success.

Excimer Laser Coronary Atherectomy/Angioplasty (ECLA)

ECLA uses a laser, instead of a traditional blade, to perform atherectomy and angioplasty. The excimer laser is a pulsed ultraviolet laser that can erode calcified plaque while also causing minimal thermal tissue injury.

One advantage of using ELCA is that it fractures calcified plaques, thereby facilitating PTCA. However, it also has a higher equipment cost and has a lesser ease of use than rotational atherectomy. Furthermore, it is more commonly used in lower extremity peripheral arterial disease than in coronary artery disease (CAD).

Stents

In cardiology, a stent is a tube that is inserted into an artery to counteract significant decreases in vessel diameter by acutely propping it open.

In the treatment of calcified lesions, stents are frequently used in conjunction with PTCA or atherectomy to decrease the risk of restenosis. Extra care should be taken in deploying stents in lesions where incomplete expansion occurs following pre-dilation, as incomplete expansion of a target lesion will increase the likelihood of restenosis. Stents should be deployed only after ensuring full balloon expansion.

Summary

In summary, heavily calcified lesions add complexity to a percutaneous coronary intervention. Other major points to remember include:

• Incomplete expansion of a target lesion will increase the likelihood of restenosis.
• Rotational atherectomy is frequently employed following unsuccessful pre-dilating PTCA to perform plaque modification.
• Stents should be deployed only after ensuring full balloon expansion.

References

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