Percutaneous Coronary Intervention

Anatomy and Physiology

Access to the bloodstream is achieved through either the femoral or radial artery. Real-time X-ray fluoroscopy is used to visualize the location of the catheter and tissues. The catheter is advanced to ascending aorta. Coronary arteries are engaged using different catheters for the right and left coronary artery.  IV contrast is introduced in the coronary artery to delineate the anatomy. Pictures of coronary arteries are taken from different angles to help access the three-dimensional nature of the narrowing.

Indications

The following are the clinical indications that could require a percutaneous coronary intervention.

• Acute ST-elevation myocardial infarction (STEMI)
  • Primary PCI is the recommended method of reperfusion when it can be performed in a timely fashion by experienced operators.[1]
  • STEMI and ischemic symptoms of less than 12 hours' duration.[2]
  • STEMI and ischemic symptoms of less than 12 hours' duration and contraindications to fibrinolytic therapy
  • PCI improves survival in patients with significant (>50%) stenosis
• Non–ST-elevation acute coronary syndrome (NSTE-ACS) 
  • Early invasive therapy (within 2 hours of symptoms) recommended with refractory angina, recurrent angina, symptoms of heart failure, new or worsening mitral regurgitation, hemodynamic instability, or sustained ventricular tachycardia/fibrillation.
  • A worsening of troponin levels should trigger an early therapy (within 24 hours)

• Unstable angina
• Stable angina
• Anginal equivalent (e.g., dyspnea, arrhythmia, or dizziness or syncope)
• High-risk stress test findings
• PCI is indicated for critical coronary artery stenosis, which does not qualify for coronary artery bypass surgery (CABG).[3]

Contraindications

Absolute Contraindications

• Noncompliance with the procedure and inability to take dual antiplatelet therapy.
• High bleeding risk (thrombocytopenia, peptic ulcer, severe coagulopathy)
• Multiple percutaneous coronary intervention restenosis

Relative Contraindications

• Intolerance for oral antiplatelets long-term
• Absence of cardiac surgery backup
• Hypercoagulable state
• High-grade chronic kidney disease
• Chronic total occlusion of SVG
• An artery with a diameter of <1.5 mm
• Stenosis of <50%
• Critical left main stenosis with no collateral flow or patent bypass graft.

Equipment

Percutaneous coronary intervention is performed during an angiogram in the angiography suite. Other than standard equipment, the following supplies may be used on a case-to-case basis. 

• Introducer needle
• Sheath introducer
• Guide catheters
• Radioopaque dye (IV contrast)
• Guidewire
• Balloon catheter
• Stents
  • Bare metal stents (BMS)
    • Preferred if the patient is not able to take a longer duration of dual antiplatelet therapy (DAPT). A minimum of 1 month of DAPT is required.
  • Drug-eluting stents (DES)
    • Found to have reduced restenosis and revascularization rates compared with BMS.
  • Bioresorbable vascular scaffold (BVS)
  • Drug-eluting balloons (DEB)
• Thrombus aspiration:
  • Not recommended routinely 
• Guidelines
• Atherectomy devices
  • Rotational
  • Laser
• Cutting balloons
• Radiation beads
• Lithoplasty/lithotripsy systems

Door to Balloon Time

The door-to-balloon time (D2B time) is used as a measure to improve the timing of PCI in patients with STEMI.  It defines a time taken between a patient's arrival to balloon inflation during the angiogram.  Studies have shown improved in-hospital mortality, which showed a shorter door to balloon times. ST-elevation myocardial infarction (STEMI) patients in the NRMI-3 and 4 registries (1999 to 2002) who were treated with percutaneous coronary intervention (PCI) within six hours of presentation, longer D2B times were significantly associated with increased in-hospital mortality (3.0, 4.2, 5.7, and 7.4 percent for D2B time of less than or equal to 90 minutes, 91 to 120 minutes, 121 to 150 minutes, and greater than 150 minutes, respectively).[4]

Access Type: Femoral vs. Radial Access

Coronary arteries can be accessed for angiogram through a radial or femoral approach. In general, the radial artery approach is preferred to reduce the risk of access site bleeding because the radial artery can be easily compressed against the radial bone compared to the femoral artery. However, access to the radial artery requires more experience and expertise because of its small size.

Before access through the radial artery, palmar arch circulation should be assessed to avoid ischemia of the hand from complications during the procedure.

A meta-analysis was done in 2016, based on 24 trials for acute coronary syndrome patients: RIVAL, MATRIX, RIFLE-STEACS, and STEMI RADIAL: Showed a reduction in following endpoints in patients who had the procedure done through the radial approach.

• Major bleeding
• All-cause mortality
• Major adverse cardiovascular events

Preparation

Antiplatelet Therapy and Indication in Percutaneous Coronary Intervention

1. Aspirin 162 to 325 mg is given on the day of PCI.
2. Unfractionated heparin may be used at the time of PCI
3. Glycoprotein IIb/IIIa inhibitors: (abciximab, tirofiban, and eptifibatide) have shown a reduction in complications with PCI. 
4. Dual antiplatelet therapy (DAPT) is a combination of aspirin (usually low dose, 81mg) with a P2Y12 inhibitor (clopidogrel, prasugrel, ticagrelor).
   1. Duration of DAPT after PCI:[5]
      1. PCI after Acute Coronary Syndrome (STEMI and non-STEMI): The minimum duration is 1 year irrespective of stent type.
      2. In patients with stable ischemic heart disease, who required PCI, DAPT should be continued for at least
         • 1 month in patients who required BMS
         • 6 months in those who required DES.
   2. Interruption of DAPT:
      1. High bleeding risk:[6]
         • Reasonable to stop after 6 months in patients with ACS who had PCI
         • Reasonable to stop after 3 months in patients with SIHD who had PCI with DES
         • Reasonable to stop after 1 month in patients with SIHD who had PCI with BMS

Technique or Treatment

Angiography

After preparing the access site for approach, usually the groin for the femoral artery approach, an introducer needle is inserted in the artery. A guidewire is passed, and the needle is withdrawn. Once the access is gained, a "sheath introducer" is inserted over the guidewire, which helps to keep the artery open. A sheath is then inserted through the sheath introducer. The sheaths are flexible hollow tubes used to introduce different catheters. Different types of sheaths are used to access different locations like right and left coronary arteries and left ventricle. With X-ray fluoroscopy, contrast material is introduced in the coronary artery to delineate its anatomy. Stenosis or occlusion of the coronary artery is then visualized, and severity is estimated through pictures at different angles. If stenosis or occlusion is located, the cardiologist then introduces a guidewire through the catheter and positions the tip of the wire distal to the stenosis in the artery. This guidewire is then used to introduce the balloon or stent catheter over it for angioplasty or stent placement, respectively. For stent placement, the catheter has the stent positioned over the balloon, and once in the right location, the balloon can be expanded, which stretches the stent open over the balloon. The catheter can then be withdrawn. Images are taken to confirm the proper location of the stent and resolution of stenosis.

Percutaneous coronary intervention

1. Balloon Angioplasty
   • A form of PCI involving the inflation of a balloon inside a coronary artery to open the narrowing. It leads to the disruption of plaque. This procedure is not the primary intervention anymore because, over time, the ballooned artery returns to the stenotic state. It is, however, performed when stent placement is either not possible or will be harmful. It can also be performed as a bridge to CABG or future PCI.
2. Stent Implantation
   • If a coronary stent is required, the catheter containing a stent (over the balloon) is advanced over the guidewire and appropriately positioned in the stenotic segment of the coronary artery; the balloon is then expanded. The stent, which is located over the balloon, expands and deploys in position, relieving the stenosis.
   • Stent placement can be done mainly by 2 methods: direct stenting or pre-dilation and stenting. Pre-dilation involves dilation of the balloon in the stenosed segment, followed by stent placement. Direct stenting involves a low-profile stent delivery system, which can be introduced directly to the lesion, and the stent is deployed without pre-dilation. The efficacy of this approach was best evaluated in a randomized trial of 206 patients with an acute STEMI who underwent primary stenting with or without pre-dilation. Although the incidence of TIMI flow grade 3 and the corrected TIMI frame count was the same with both approaches, the incidence of the composite angiographic endpoint (slow and no-reflow or distal embolization) was significantly lower with direct stenting (12 versus 27 percent with pre-dilation before stenting), and ST-segment resolution was more frequent (80 versus 62 percent).[7]
3. Atherectomy
   • Coronary atherectomy is an invasive procedure to physically remove blockage (atheroma, calcium, or cellular debris) from coronary arteries. It works by cutting the lesions with a cutter, usually a burr or crown. Directional coronary atherectomy and laser atherectomy are two major types of atherectomy. Atherectomy is typically followed by balloon and stent placement. 
   • If a calcified segment prevents the delivery of a stent in a blood vessel, atherectomy is useful; however, routine use of atherectomy before stenting has not been shown to improve the outcomes and should be avoided when not required.[8]
   • Rotational atherectomy may be infrequently required for internal mammary artery graft stenosis, although common practice is angioplasty.
   • Atherectomy is a less favored procedure for saphenous vein graft lesions.
   • In patients with diabetes, Angiographic restenosis at 6 months post atherectomy was found to be higher, and this atherectomy should be avoided if not necessary.[9]
   • The complications of atherectomy include:
     • arterial dissection
     • coronary artery perforation
     • coronary spasm
     • particle embolization
4. Brachytherapy
   • Involves intracoronary irradiation to prevent restenosis of stents. It showed a reduction in-stent restenosis in BMS, but after DESs were introduced, in-stent restenosis has decreased, so did the use of brachytherapy.

5. IVUS

   Intravascular ultrasound (IVUS) enables visualization up the coronary artery wall using a mini ager ultrasound transducer at the end of the flexible catheter; it helps in delineating the plaque morphology and distribution and helps in rationalizing the PCI. The benefit of IVUS is in the utility of intra-lumen measurements, which is not possible with coronary angiography as the view taken is usually two-dimensional and does not represent the true lumen diameter accurately because of limitations of contrast enhancement, angle of view, especially in asymmetric narrowing and complex luminal shapes.

   • The routine use of this technology to identify nonobstructive lesions at increased risk was evaluated in a study of 1563 patients with suspected coronary artery disease who underwent cardiac catheterization with possible ad hoc percutaneous coronary intervention. The rate of adverse events attributable to the procedure was low. The two-year incidence of non-culprit major adverse cardiovascular events was 9 percent, and NIRS IVUS identified patients and non-culprit segments at high risk for future events.[10]
   • In the ADAPT–DES study in which 813 STEMI patients were enrolled, IVUS use was associated with improved outcomes in STEMI patients.[11]
6. Shockwave Lithotripsy/Lithoplasty
   • This system delivers circumferential, pulsatile mechanical energy to disrupt the calcium deposits within the atherosclerotic lesion. This facilitates stent deployment later.

PCI in Non-Coronary Vessels

1. PCI in saphenous vein graft: Saphenous vein graft is still used in patients undergoing CABG. It usually connects the ascending aorta to the target blood vessel. The rate of complication in saphenous vein graft is historically higher than left internal mammary graft. Multiple studies have shown poor outcomes with saphenous vein grafts in long-term follow-up compared with arterial graft. These grafts would usually require PCI if atherosclerosis is worse. DES is preferred compared to other stents, if possible, based on antiplatelet therapy requirements.[12]
2. PCI in the Left Internal Mammary Vessel: Left internal mammary artery, which is now preferred as a conduit for CABG, has a better survival rate compared with a saphenous vein graft.  However, when compared after PCI, LIMA had 50% residual stenosis and repeat CABG requirements in the hospital, compared with saphenous vein graft PCI.[13]

Complications

Coronary Artery or Aortic Injury

• Dissection
• Rupture

Bleeding

• Usually, at the access site, groin (femoral approach) or wrist (radial approach). It could be internal or external.

Infection

• Local: involving the infection of the access site.
• Systemic: bacteremia after percutaneous coronary intervention.

Renal Failure

• The contrast used in angiograms can worsen renal function, especially in patients with prior renal dysfunction.

Stroke

• From blood clots generated during the procedure.

Myocardial Infarction

• secondary to dissection or thrombosis. Thrombosis could be within the stent or distal to PCI from plaque debris. 

 Complication Rate Increased

• Age greater than 65 years
• Female gender
• Renal dysfunction
• Diabetes
• Systolic heart disease
• Extensive coronary artery disease
• Low BMI patients (higher inpatient bleeding complications)[14]

Clinical Significance

Percutaneous coronary intervention is being used extensively over the last many years. 80% of PCI is being done with stents. Over the past 20 years, short-term mortality, MI, and target vessel revascularization have shown a significant reduction in patients with PCI. 

Comparing the outcomes in different trials for PCI vs. CABG and medical therapy, the following are the preferred treatments for different patient categories. SYNTAX score is a tool used to estimate the complexity of coronary lesions and helps determine the decision-making process between PCI or CABG.[15][16]

PCI vs. CABG

• CABG is preferred in patients with two or three-vessel disease with high SYNTAX scores.[17]
• CABG is also preferred in patients with the left main disease or one or two-vessel disease and low SYNTAX score.
• CABG has shown better outcomes with multivessel disease in patients with diabetes compared with PCI.[18][19][20]
• LIMA to LAD graft has better survival irrespective of other grafts present.[21]
• Studies have shown better patency of internal mammary graft compared with SVG.[22]

PCI vs. Medical Therapy

• Medical therapy with high-dose statins is preferred over balloon angioplasty in patients with mild anginal symptoms.[23][24]
• PCI is preferred over medical therapy if the patient has;
  • Severe symptoms
  • Failed medical therapy
  • High-risk coronary anatomy
  • Worsening LV function

Enhancing Healthcare Team Outcomes

An interprofessional heart team approach is recommended in patients with multivessel disease or severe left main disease and a high Syntax score. This team includes the family clinician, cardiologist, mid-level practitioners, and cardiology specialty-trained nurses. The team consists of interventional cardiology and cardiac surgery. Pharmacists can offer input for post-procedure medications and perform medication reconciliation.

Same-day discharge after percutaneous coronary intervention showed comparable results with overnight admission in two metanalyses.[25]

Nursing, Allied Health, and Interprofessional Team Interventions

Early Team Discharge in Patients with STEMI after PCI

In low-risk patients with ST-elevation MI, who undergo percutaneous coronary intervention, early discharge (defined as discharge at 72 hours) had shown improved outcomes.

One study used the Zwolle risk index and classified two-third of its patients at low risk of 3 or less [classified as a low risk]. Mortality for these patients was 0.1% at 2 days and 0.2% from 2 to 10 days post; therefore, it was suggested that such patients could be discharged safely after 48 hours of PCI.

PAMI-2 Trial had low-risk patients after PCI assigned to accelerated care or traditional care. Patients with accelerated care received a discharge on day 3. They showed a significant cost reduction. There was no difference in mortality, unstable angina, reinfarction, stroke, and heart failure between the 2 groups at 6 months.