Laser in Coronary Angioplasty

LASER stands for Light Amplification by Stimulated Emission of Radiation. Early forms of LASER were used in coronary angioplasty in the 1980s. These included Argon and Nd YAG LASER systems. These were costly and had disappointing results with lots of complications.

Re-emergence of LASER in coronary angioplasty came about with the development of “cold” LASER or Excimer LASER. Excimer is an acronym for the excited dimer that produces ultraviolet laser energy of pulsatile nature and short wavelength. The pulsatile nature ensured the precise ablation of plaque tissue with no significant thermal injury to the vessel. The short wavelength through less depth of penetration also limited collateral damage. Both of these properties of excimer lasers, in addition to improvement in catheter design, proper selection of patients, and development of safety protocols, played a crucial role in the reintroduction of laser technology in routine practice.

This technology has only very recently come to India and so far, this has given the interventional cardiologists a new precise weapon in the management of many problems during complex coronary angioplasty.

When is LASER Angioplasty recommended?

FDA in US has approved LASER angioplasty for

• Balloon un-crossable and un-dilatable lesions

• Thrombotic saphenous vein graft lesions (post CABG surgery)

• Chronic total occlusion (CTO)

• Moderately calcified lesions

• Ostial lesions

• Eccentric lesions

• Long lesions (> 20 mm)

• In-stent restenosis (blockages which have recurred inside previously implanted stents) In addition, LASER is also useful for:

  • Highly thrombotic lesions (during PCI in acute MI, acute coronary syndromes)

  • For angioplasty of under-expanded stents

  • Modification of proximal cap of calcified lesions, which cannot be crossed with wire

  • Similar blockages in peripheral arteries, carotids, etc,

  • Extraction of previous implanted pacemaker leads

What is the mechanism of action of LASER

LASER beams are high-energy light beams. Xenon gas and Hydrochloric acid react after passage of high voltage electricity to form excited dimers or excimers of XeCl salt that emit UV light. The light is amplified by mirror systems to yield high-energy light beams that can be targeted to the abnormal plaque tissue. The ablation of the tissue happens by 1) Photochemical, 2) Photothermal, and 3) Photomechanical/Photokinetic mechanisms to create micro-particles that are cleared by the body.

Treatment technique with LASER:

LASER is mostly used as an adjunct to the conventional tools of coronary angioplasty. The patient and all personnel in the cathlab are required to wear goggles to prevent eye damage due to UV light. After the guide catheter engages the coronary artery and the guidewire is threaded across the target lesion, the LASER catheter is advanced to the lesion over the wire. The other end of the catheter is connected to the console. LASER energy is then applied to the target tissue in short pulses with brief pauses in between. After successful lasing, further balloon dilatations and stenting may be done, as per need.

When is LASER NOT used?

LASER is NOT recommended if there is an acute angulation of the vessel, tortuosity, very heavy calcium, or dissection. It is also not recommended for the Left Main coronary artery.

How safe is LASER?

Used appropriately and in experienced hands, LASER is very safe. There are many inbuilt safety protocols to promote the safe use of LASER in coronaries. A saline infusion protocol is followed to prevent the development of dissections, insoluble gas bubbles, and to provide a clean interface to deliver the energy to the tissue without being obstructed by large molecules in the blood. Uncommon complications include vessel injury, vessel perforation, vessel spasm, embolism and bleeding.

5 S approach to achieve the best results from LASER Angioplasty:

• selection of patient
• Size of the laser catheter
• Settings (fluence and pulse rate)
• Saline infusion protocol
• Slow advancement

Advantages of LASER angioplasty:

Higher success rates and better results in complex interventions Avoidance of low reflow/no=reflow in highly thrombotic lesions

Distal protective devices are not a necessity in highly thrombotic lesions

Significant improvement in cases of in-stent restenosis, excellent results and many a time, avoiding the need for a new stent

Post-procedure Care:

This is similar to any complex angioplasty. After a LASER angioplasty procedure, the patient will recover in an intensive care setting overnight. If all things go well, he may be discharged on the 2nd or 3rd day. All routine preventive care steps should be taken, as with any regular angioplasty.

The patient should focus on an appropriate low fat, low salt, low/no sugar diet, exercise for 30 minutes daily and consume his prescribed medicines regularly to prevent recurrence of the blockages. Regular follow-up visits with the cardiologist are integral to good preventive care.