High-Risk Percutaneous Coronary Interventions

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12 High-Risk Percutaneous Coronary Interventionsimage

Michael J. Lim, Todd K. Zynda, Morton J. Kern, Arnold H. Seto, William M. Suh

The risk of major complications such as myocardial infarction (MI), life-threatening arrhythmias, need for emergency coronary artery bypass surgery (CABG), and death during a percutaneous coronary intervention (PCI) is influenced by angiographic, patient-related, and clinical factors. Knowledge of these factors allows the interventionalist to identify the patient at high risk of complications and facilitates the essential discussion of the risks and benefits of the intervention with the patient, family, and hospital personnel (e.g., cardiac surgeons). Appropriate measures can then be taken before and during the high-risk PCI procedure to minimize the risk of a major adverse event, and the medical team can be optimally prepared to deal with complications should they occur.

Identifying the High-Risk PCI Patient

Retrospective studies and databases have been utilized to identify risk factors for adverse events occurring during PCI.

Angiographic Factors

The American College of Cardiology/American Heart Association (ACC/AHA) created a scoring system that classified lesions according to their complexity, likelihood of successful dilation, and the likelihood of an adverse event. Lesions were classified as either type A, B, or C, with C the highest risk lesions, based on lesion characteristics (Tables 12-1 and 12-2).

Table 12-1 The ACC/AHA Lesion Classification Scheme

Type A Lesions

• Discrete

• Concentric

• Ready accessibility

• Location in a nonangulated segment (<45°)

• Smooth contour

• Little or no calcification

• Absence of total occlusion

• Nonostial location

• Absence of major branch involvement

• Absence of thrombus

Type B Lesions

• Tubular (10–20 mm in length)

• Eccentric

• Accessibility influenced by moderate tortuosity of proximal segment

• Location in moderately angulated segment (45°–90°)

• Irregular contour

• Moderate or severe calcification

• Presence of thrombus

• Ostial location

• Bifurcation lesion requiring double wiring

• Total occlusion <3 months old

Type C Lesions

• Diffuse disease (>20 mm in length)

• Excessive tortuosity of proximal segments

• Location in an extremely angulated segment (>90°)

• Total occlusion >3 months old

• Inability to protect major side branches

• Degenerated vein grafts

ACC, American College of Cardiology; AHA, American Heart Association.

Table 12-2 Lesion Characteristics and the Increased Risk of Ischemic Complications (Based on Multivariate Analysis)

Lesion Characteristic Odds Ratio
Nonchronic total occlusion 4.74 (2.69–8.38)
Degenerated saphenous vein graft 4.18 (2.39–7.31)
Length ≥20 mm 2.77 (1.51–5.09)
Irregularity 1.88 (1.32–2.66)
Large filling defect 1.41 (1.17–1.70)
Length 10–20 mm 1.88 (1.26–2.82)
Moderate calcification with angulation >45° 4.44 (1.24–15.96)
Eccentric 2.12 (1.04–4.57)
Severe calcification 2.19 (1.04–4.57)
Saphenous vein graft age ≥10 years 1.81 (1.00–3.31)

Adapted from Ellis SG, Guetta V, Miller D, et al. Relation between lesion characteristics and risk with percutaneous intervention in the stent and glycoprotein IIb/IIIa era. Circulation 1999;100:1971–1976.

The ACC/AHA Lesion Classification Scheme has since been modified in that lesions with one “type B” characteristic are designated as “type B1” while lesions with two or more “type B” characteristics are designated as “type B2” lesions. Since this classification was first implemented in 1988, significant advances in PCI techniques have allowed treatment of more complex lesions with lower risks. In the current era of coronary stenting, it is primarily the type C lesions that are associated with lower success and higher complication rates.

In the mid-1990s, an era in which coronary stents and platelet glycoprotein IIb/IIIa inhibitors were frequently utilized, Ellis and coworkers analyzed a large database of patients undergoing PCI. Ten angiographic factors were identified that correlated with greater risk of complication. The two factors associated with the greatest increased risk were degenerated saphenous vein grafts (relative risk 4.18) and nonchronic total occlusion (relative risk 4.74). Other factors included long lesions, lesions with large filling defects, calcified angulated lesions, eccentric lesions, and old saphenous vein grafts (Table 12-2). The finding of marked increased risk in degenerated vein grafts supports the practice of using distal protection devices during PCI of such lesions.

Angiographic Risk Assessment Using the SYNTAX Score

The SYNTAX score, an angiographic grading tool to determine the complexity of coronary artery disease (CAD), was derived from pre-existing risk assessment classifications from numerous studies and expert consensus. The SYNTAX score is the sum of the points assigned to each individual lesion identified in the coronary tree with >50% diameter narrowing in vessels >1.5 mm diameter. The coronary tree is divided into 16 segments according to the AHA classification (see Fig. 12-1). Each segment is given a score of 1 or 2 based on the presence of disease, and this score is then weighted based on a chart, with values ranging from 3.5 for the proximal left anterior descending artery (LAD) to 5.0 for left main, and 0.5 for smaller branches. The branches <1.5 mm in diameter, despite having severe lesions, are not included in the SYNTAX score. The percent diameter stenosis is not a consideration in the SYNTAX score, only the presence of a stenosis from 50% to 99% diameter, <50% diameter narrowing, or total occlusion. A multiplication factor of 2 is used for non-occlusive lesions and 5 is used for occlusive lesions, reflecting the difficulty of PCI. Further characterization of the lesions adds points. (Fig. 12-1 shows the diagram of vessel segments used in the SYNTAX score.)

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Figure 12-1 Definition of the coronary tree segments from the SYNTAX study

1. RCA (right coronary artery) proximal: from the ostium to one half the distance to the acute margin of the heart.

2. RCA mid: from the end of first segment to acute margin of heart.

3. RCA distal: from the acute margin of the heart to the origin of the posterior descending artery.

4. Posterior descending artery: running in the posterior interventricular groove.

5. Left main: from the ostium of the LCA (left coronary artery) through bifurcation into left anterior descending and left circumflex branches.

6. LAD (left anterior descending) proximal: proximal to and including first major septal branch.

7. LAD mid: LAD immediately distal to origin of first septal branch and extending to the point where LAD forms an angle (RAO [right anterior oblique] view). If this angle is not identifiable, this segment ends at one half the distance from the first septal to the apex of the heart.

8. LAD apical: terminal portion of LAD, beginning at the end of previous segment and extending to or beyond the apex.

9. First diagonal: the first diagonal originating from segment 6 or 7.

9a. First diagonal a: additional first diagonal originating from segment 6 or 7, before segment 8.

10. Second diagonal: originating from segment 8 or the transition between segment 7 and 8.

10a. Second diagonal a: additional second diagonal originating from segment 8.

11. Proximal circumflex artery: main stem of circumflex from its origin of left main and including origin of first obtuse marginal branch.

12. Intermediate/anterolateral artery: branch from trifurcating left main other than proximal LAD or LCX (left circumflex). It belongs to the circumflex territory.

12a. Obtuse marginal a: first side branch of circumflex running in general to the area of obtuse margin of the heart.

12b. Obtuse marginal b: second additional branch of circumflex running in the same direction as 12.

13. Distal circumflex artery: the stem of the circumflex distal to the origin of the most distal obtuse marginal branch, and running along the posterior left atrioventricular groove. Caliber may be small or artery absent.

14. Left posterolateral: running to the posterolateral surface of the left ventricle. May be absent or a division of obtuse marginal branch.

14a. Left posterolateral a: distal from 14 and running in the same direction.

14b. Left posterolateral b: distal from 14 and 14a and running in the same direction.

15. Posterior descending: most distal part of dominant left circumflex when present. It gives origin to septal branches. When this artery is present, segment 4 is usually absent.

16. Posterolateral branch from RCA: posterolateral branch originating from the distal coronary artery distal to the crux.

16a. Posterolateral branch from RCA: first posterolateral branch from segment 16.

16b. Posterolateral branch from RCA: second posterolateral branch from segment 16.

16c. Posterolateral branch from RCA: third posterolateral branch from segment 16.

(From Sianos G, Morel MA, Kappetein AP, et al. The SYNTAX Score: an angiographic tool grading the complexity of coronary artery disease. EuroIntervention 2005;1:219–227.)

The SYNTAX score algorithm then sums each of these features for a total SYNTAX score. Table 12-3 summarizes the SYNTAX grade categories. A computer algorithm (available online at www.syntaxscore.com) is then queried, and a summed value is produced. Figure 12-2 shows two patients each with three-vessel CAD but very different PCI risk based on SYNTAX scores.

Table 12-3 The SYNTAX Score Algorithm

1. Dominance

2. Number of lesions

3. Segments involved per lesion, with lesion characteristics

4. Total occlusions with subtotal occlusions

a. Number of segments
b. Age of total occlusions
c. Blunt stumps
d. Bridging collaterals
e. First segment beyond occlusion visible by antegrade or retrograde filling
f. Side branch involvement

5. Trifurcation, number of segments diseased

6. Bifurcation type and angulation

7. Aorto-ostial lesion

8. Severe tortuosity

9. Lesion length

10. Heavy calcification

11. Thrombus

12. Diffuse disease, with number of segments

Reprinted from Sianos G, Morel MA, Kappetein AP, et al. The SYNTAX score: an angiographic tool grading the complexity of CAD. EuroIntervention 2005;1:219–227.

image

Figure 12-2 Angiographic examples of SYNTAX scores in patients undergoing PCI. Selected angiograms.

(Reprinted from Sianos G, Morel MA, Kappetein AP, et al. The SYNTAX score: an angiographic tool grading the complexity of CAD. EuroIntervention 2005;1:219–227 with permission.)

In patients with SYNTAX score <33, equal outcomes after revascularization were obtained with regard to major adverse cardiac events for both PCI and CABG. For higher SYNTAX scores, CABG had fewer adverse events than PCI. The conclusion of the SYNTAX study showed that the overall safety outcomes (death, cerebrovascular accident, MI) were similar in CABG and PCI patients at 12 months (7.7 vs. 7.6%). There was a higher rate of revascularization in the PCI group (13.7 vs. 5.9%), balanced by a higher rate of cerebrovascular accident in the CABG group (2.2 vs. 0.6%). Of note, the overall PCI major adverse cardiac and cerebrovascular event rate (MACCE) was higher (17.8 vs.12.1%) primarily due to an excess need for repeat revascularization. If one accepts a repeat revascularization as part of the natural history of PCI and not an adverse event, then the difference between revascularization strategies becomes even less (Fig. 12-3).

image

Figure 12-3 Outcomes of SYNTAX study by SYNTAX scores. Rates of major adverse cardiac or cerebrovascular events among the study patients, according to treatment group and SYNTAX score category. Kaplan-Meier curves are shown for the percutaneous coronary intervention (PCI) group and the coronary artery bypass grafting (CABG) group for major adverse cardiac or cerebrovascular events at 12 months. The 12-month event rates were similar between the two treatment groups for patients with low SYNTAX scores (0–22) (A) or intermediate SYNTAX scores (23–32) (B). Among patients with high SYNTAX scores (=33, indicating the most complex disease), those in the PCI group had a significantly higher event rate at 12 months than those in the CABG group. SYNTAX scores were calculated at the core laboratory. The I bars indicate 1.5 SE. P values were calculated with the use of the chi-square test.

(Reprinted from Serruys PW, Morice, MC, Kappetein AP, et al. Percutaneous coronary intervention versus coronary-artery bypass grafting for severe coronary artery disease. N Engl J Med 2009;360(10):961–972.)

Based on angiographic assessment and the operators’ experience in the cath lab, the number and type of complex anatomic lesions determines which revascularization approach might be selected. However, the physiology of coronary lesions and stenting are strongly related to outcomes. A recent publication by Tonino et al. from the FAME study group reported on what truly constituted three-vessel and two-vessel CAD, making clear that one cannot equate angiographic three-vessel CAD with physiologic three-vessel CAD. Fractional flow reserve thus has important implications for the decision-making process in patients with multivessel disease.

Patient-Related Factors

Several clinical factors can be utilized to identify high-risk PCI, such as the presence of multivessel disease, angioplasty to more than one lesion, suboptimal activated clotting time (ACT), residual stenosis above 30%, depressed ejection fraction, old age (>65 years), unstable angina and recent MI (Table 12-4). A retrospective study from the Mayo Clinic, examining the risk of PCI with the use of glycoprotein IIb/IIIa inhibitors and coronary stents, found that clinical factors such as left main or multivessel disease, an ejection fraction below 35%, or a recent MI were more important than angiographic factors for predicting complications. Other studies have identified the presence of diabetes mellitus and renal disease as indicators of high-risk patients (Table 12-5).

Table 12-4 Patient and Clinical Factors Associated With Higher Risk PCI

Presence of left main coronary artery or multivessel disease

PCI of more than one lesion

Suboptimal activated clotting time

Residual stenosis above 30%

Depressed ejection fraction (<35%)

Age over 65 years

Unstable angina and/or recent myocardial infarction

Severe comorbid disease

PCI, percutaneous coronary intervention.

Table 12-5 Elective PCI Patient and Lesion High-Risk Characteristics

High-Risk Patient

• Decompensated CHF (Killip Class 3-4)

• Recent (<8 weeks) cerebrovascular accident

• Known clotting disorder

• Left ventricular ejection fraction < or = 30%

• Renal failure (creatinine >2.0 mg/dL)

• Malignant ventricular arrhythmias
High-Risk Lesion

• Left main stenosis > or = 50% or three-vessel disease (>70% proximal or mid lesions)

• Unprotected by prior bypass surgery

• Target lesion that jeopardizes an extensive amount of myocardium (Jeopardy scoring systems, such as SYNTAX, may be useful in defining the extent)

• Diffuse disease (>20 mm length)

• Greater than moderate lesion calcification

• Extremely angulated segment or excessive proximal or in-lesion tortuosity

• Inability to protect side branches

• Older SVGs with friable lesion

• Thrombus in vessel or at lesion site

• Vessel characteristics that, in the operator’s judgment, would impede stent deployment

• Chronic total occlusions

CHF, congestive heart failure; SVG, saphenous vein graft.

Modified from King SB, III, Walford G, for the New York State Cardiac Advisory Committee. Percutaneous coronary interventions in New York State, 2005–2007. Albany: New York State Department of Health, April 2010;1–52; and Dehmer GJ, Blankenship J, Wharton TP, Jr., et al. The current status and future direction of percutaneous coronary intervention without on-site surgical backup: an expert consensus document from the Society for Cardiovascular Angiography and Interventions. Catheter Cardiovasc Interv 2007;69:471–478.

Operator Experience

Another factor that has been correlated with PCI risk is operator volume and experience. Several studies have found that those operators with greater experience have lower complication rates, the correlate being that those with lower procedural volume and experience have higher complication rates. Operators with limited high-risk PCI volume and experience should consider referral to a tertiary center where advice and expertise are available.

Myocardium at Risk

In patients with depressed ejection fraction, it is particularly important to assess which myocardial territories (anterior, lateral, inferior) are akinetic and/or infarcted and which myocardial territories are doing the majority of the “work” of left ventricular function. In a patient with infarcted lateral and inferior walls in which the only functioning territory is the anterior wall and septum, PCI of the left anterior descending coronary artery carries extreme risk; if there is compromised blood flow during the procedure, the patient can be expected to tolerate this poorly. To some extent, a situation such as this should be considered as a “left main equivalent,” and decisions regarding PCI and pharmacologic and/or mechanical support must be made accordingly.

Vascular Disease

An often underappreciated factor in the high-risk PCI patient is vascular access and vascular disease. During the high-risk PCI procedure, an intra-aortic balloon pump (IABP) may be placed either prophylactically or emergently, requiring knowledge of the presence of iliac/femoral arterial disease beforehand. Palpation of strong bilateral femoral pulses should be coupled with angiography. When possible, angiography of the iliac and common femoral arteries should be performed prior to a high-risk PCI to determine if the patient is a candidate for IABP support.

Specific High-Risk Subsets

Left Main Coronary Artery PCI (also see Chapter 11)

Several registries and retrospective studies have examined procedural success and short- and intermediate-term complication rates in patients undergoing PCI of unprotected left main (UPLM) lesions. Some patients underwent PCI because they were poor candidates for CABG, some because of strong patient preference, and a few because of acute myocardial infarction (AMI).

The results of UPLM balloon angioplasty without stenting have been poor, with in-hospital mortality rates of up to 9.1% and a 3-year survival rate of 36%.

Reports of UPLM coronary stenting provide relatively encouraging data, including some with no in-hospital or late death attributable to the PCI procedure. However, in general, these reports are retrospective, limited to carefully selected patients, and from institutions with a high degree of experience and expertise. Thus, despite enthusiasm and encouraging results from small patient series, until randomized data are available comparing UPLM PCI to CABG, a UPLM stenosis should generally be considered a contraindication to PCI and should be preferentially treated with CABG.

In patients who are not candidates for, or who adamantly refuse, CABG, PCI of the left main appears to be a viable option but should be considered a very high–risk PCI, undertaken only with all the precautions discussed above. Any decision regarding UPLM PCI should be made in consultation with the cardiothoracic surgery service. Patients receiving successful UPLM PCI should undergo routine surveillance angiography during the restenosis window, in light of the high rate of mortality observed during the first 6 months after the procedure.

PCI for AMI

PCI for AMI can be performed before (primary PCI) or after thrombolysis (facilitated or rescue PCI). Primary PCI is the approach of choice for acute ST-segment elevation MI, but is not available in all facilities. Primary PCI for AMI is indicated in patients who present within 12 hours from the onset of symptoms and in whom the infarct vessel can be recanalized within 90 minutes of presentation. Primary PCI is also indicated for patients in whom thrombolytics are contraindicated and for patients in cardiogenic shock. Figure 12-4 shows angiograms of PCI for AMI.

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Figure 12-4 Angiograms of patient with acute inferior myocardial infarction (MI) with thrombus in the right coronary artery (RCA) (top left,A).B shows post balloon dilation, C, during stent implantation, and D, final result with no significant residual narrowing.

(Courtesy of Drs. Wil Suh and Igor Palacios.)

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