PCI in the calcified lesion
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Challenges of Calcified Lesions
- The presence of coronary calcification reduces the compliance of the vessel, and may predispose to dissections at calcified plaque–normal wall interface after balloon angioplasty
- The presence of coronary calcification also reduces the ability to cross chronic total occlusions, and, in severely calcified lesions, stent strut expansion is inversely correlated with the circumferential arc of calcium. [1]
- The presence of extensive coronary calcification poses unique challenges for PCI as calcium in the vessel wall leads to irregular and inflexible lumens, and 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, on occasion, leading to “undilatable” lesions that resist any achievable balloon expansion pressure.
Calcification in Saphenous Vein Grafts (SVGs)
Calcifications noted within SVGs are generally within the reference vessel wall rather than within the lesion, and are associated with older graft age, insulin–dependent diabetics, and smoking. [2]
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 only moderately sensitive for the detection of extensive lesion calcium (sensitivity 60% and 85% for three- and four-quadrant calcium, respectively). [3]
Treatment
There are a variety of diagnostic and treatment options for calcified lesions, but better early outcomes may be achieved by using a multi-device interventional strategy.
Percutaneous Transluminal Coronary Angioplasty (PTCA)
Percutaneous transluminal coronary angioplasty (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, additional 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. This is because 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)
Intravascular Ultrasound is a medical imaging methodology using a specially designed catheter with a miniaturized ultrasound probe attached to the distal end 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 blockage from an artery in the body and subsequently widening arteries 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 creates micro-fractures, removes calcified plaque, and increases vessel compliance, thereby facilitating PTCA. Despite its usefulness in treating calcified lesions, certain precautions should be taken. In an effort to limit the risk of vessel laceration, smaller diameter [[Burr (cutter)|burrs] are now recommended. A general guideline to use is that the initial burr: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[4], including stent dislodgement.
- Rotational atherectomy in mild-moderate calcifications: In less severely calcified lesion, no differences in restenosis rates were found after paclitaxel-eluting stent implantation in calcified and non calcified vessels. [5]
Directional Coronary Atherectomy (DCA)
Directional coronary atherectomy 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 removed from the artery once they are caught within the catheter.
One problem that may arise with the procedure is that heavy calcification proximal to the target lesion may limit deliverability of the device and its success.
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 lesion, 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.
References
- ↑ Vavuranakis M, Toutouzas K, Stefanadis C, Chrisohou C, Markou D, Toutouzas P (2001). "Stent deployment in calcified lesions: can we overcome calcific restraint with high-pressure balloon inflations?". Catheter Cardiovasc Interv. 52 (2): 164–72. PMID 11170322. Unknown parameter
|month=ignored (help) - ↑ Castagna MT, Mintz GS, Ohlmann P; et al. (2005). "Incidence, location, magnitude, and clinical correlates of saphenous vein graft calcification: an intravascular ultrasound and angiographic study". Circulation. 111 (9): 1148–52. doi:10.1161/01.CIR.0000157160.69812.55. PMID 15723972. Unknown parameter
|month=ignored (help) - ↑ Mintz GS, Popma JJ, Pichard AD; et al. (1995). "Patterns of calcification in coronary artery disease. A statistical analysis of intravascular ultrasound and coronary angiography in 1155 lesions". Circulation. 91 (7): 1959–65. PMID 7895353. Unknown parameter
|month=ignored (help) - ↑ Wilensky RL, Selzer F, Johnston J; et al. (2002). "Relation of percutaneous coronary intervention of complex lesions to clinical outcomes (from the NHLBI Dynamic Registry)". Am. J. Cardiol. 90 (3): 216–21. PMID 12127606. Unknown parameter
|month=ignored (help) - ↑ Moussa I, Ellis SG, Jones M; et al. (2005). "Impact of coronary culprit lesion calcium in patients undergoing paclitaxel-eluting stent implantation (a TAXUS-IV sub study)". Am. J. Cardiol. 96 (9): 1242–7. doi:10.1016/j.amjcard.2005.06.064. PMID 16253590. Unknown parameter
|month=ignored (help)