PCI in a Patient with a Complex Coronary Anatomy: Procedure and Clinical Outcome
Dr Kursat Tigen, of Istanbul, Turkey discussed the challenges of PCI in complex coronary anatomy, which includes unprotected LM stenosis, bifurcation lesions, CTOs, long lesions, diffuse lesions, severe calcification and tortuosity, and thrombotic and undilatable lesions. Atraumatic delivery and precise positioning of a stent across the target lesion are the most basic requirements of a successful intervention. This requires careful preparation, including selection of the access site, guiding catheter (type, size and curve), guidewire and dedicated devices for lesion crossing, as well as a planned procedure, including the decision whether to perform predilation, direct stenting and single- or double-stent strategy. The need for surgical back-up and pharmacotherapy to reduce the risk of thrombotic complications should also be considered.
Stent selection is an important part of planning an intervention, with the aim of avoiding procedural failure. Unfavourable mechanical properties of stent delivery systems such as rigidity, poor deliverability and crossability can reduce the success rates in complex coronary PCI procedures. Resistance to longitudinal deformations is also important and is influenced by strut thickness, connector number and design. The open-cell design is preferred to increase the flexibility of the stent at the expense of reduced radial force. The mechanical response of coronary stent systems has been described using terms such as pushability, trackability, crossability, flexibility and conformability. Each of the three delivery parameters (pushability, trackability and crossability) is based on the resisting forces that can be quantified along the delivery path.
Pushability represents the transmission of the applied force to the catheter tip, and hence ‘feel’ of the operator. The bending stiffness of the stent system also contributes to the pushability. Bending stiffness is a measure of the structure’s resistance to bending deformation and is the reciprocal of flexibility. Trackability is the ability of stent delivery system (SDS) to track or move easily through the curved vascular pathway. The ability of the SDS to bend and twist will most likely depend on the geometry of the connections and raw material. Low tracking forces are necessary to prevent stent dislodgement or mechanical vascular injury. Crossability is the ability of SDS to pass through the target lesion. Crossability depends mainly on the profile of the crimped stent. Low-profile SDS devices appear to be essential in cases with extremely tight and complex target lesions. Flexibility is critical in preservation of the function and the integrity of the stent in complex coronary interventions. Flexible stents are easily inflated and show great adaptability to vessel shape compared with a rigid stent. The ability of a stent system to conform to the geometrical shape of the vessel after stent implantation is defined as conformability. Stent conformability is associated with efficient and homogeneous diffusion of the anti-proliferative drugs in the coronary vessels. Stents with biodegradable polymer technology are also desired devices for complex lesions as they have been associated with lower rates of late stent thrombosis.
To illustrate these factors, Dr Tigen presented the case of a 50-year-old man who had exercise angina (Canadian Cardiovascular Society Grade III) and dyspnoea. He had arterial hypertension, diabetes and a family history of coronary artery disease, and had been a smoker for 40 years. Echocardiography showed inferior hypokinesia with preserved ejection fraction, as well as mild mitral regurgitation. The angiogram showed mild proximal LAD disease but severe stenosis in the body and the side branch of the LCX artery. The RCA also had sub-total occlusion from the proximal to the distal end of the vessel; this was a long lesion. Fractional flow reserve measurement of the proximal LAD disease revealed a haemodynamically non-significant lesion (basal: 0.89; maximum hyperaemia: 0.81). The procedure was carried out with PCI to the complex RCA lesion. Peri-procedural management included a loading dose of 300 mg clopidogrel and 100 mg aspirin, and 8000 IU heparin for anti-coagulation. A right femoral approach was selected with a 7F sheath, a JR4 AlviguideBlue+ guiding catheter used for coronary engagement and a BMW Universal 0.014 inch guidewire was used for lesion crossing. This passed the lesions easily despite marked complexity. Predilation was performed using a 1.25 x 15 mm balloon, then a 2.0 x 20 mm balloon. Stenting was performed using a full-metal jacket procedure from the proximal segment of the postero-lateral branch to the osteal RCA. A 2.5 x 28 mm Coracto DES was followed by 2.75 x 28 mm, 3.0 x 32 mm and 3.0 x 21 mm Coracto DES, and the procedure was finalised with 3.0 x 15 mm non-compliant balloon postdilation up to 24 atmospheres. The final angiogram revealed good stent expansion and strut coverage with a TIMI-III flow. Despite severe tortuosity and calcification, the stent conformability was excellent. One year angiographic follow-up demonstrated an intact RCA with all stents open and no significant restenosis.
In addition to the favourable mechanical properties increasing the success rate, such as stent design, thin struts and low polymer thickness, resulting in a DES that is easy to manipulate, several factors influenced the choice of Coracto DES in this complex coronary procedure. Its 100 % absorbable (PLGA) coating is quickly absorbed, assuring no long-term inflammation with optimised endothelialisation and reduced rates of stent restenosis. Controlled elution of sirolimus is also associated with excellent efficacy in terms of anti-proliferative properties.
In challenging endovascular anatomy, usually more than one important mechanical property of SDS and the stent platform may come in to play. In practical terms, the design of the Coracto DES presents numerous advantages in complex coronary interventions. Greater pushability is useful for small vessels and diffuse atherosclerotic disease with narrow proximal access. Good trackability and flexibility are beneficial in diffuse or calcified lesions, highly tortuous proximal vessels and distal target lesions. Furthermore, a high demand on crossability is required in cases with tight and complex target lesions. Finally, stent conformability is essential in homogeneous diffusion of the anti-proliferative drugs in the coronary vessels.
In conclusion, the Coracto DES is a safe and effective option in PCI of complex coronary anatomy cases with high procedural success rates and long-term beneficial effects.
The publication of this article was supported by Alvimedica.