Incidence, Predictors, and Outcome of Plaque Prolapse after Stent Implantation in Patients

with Acute Myocardial Infarction: An Intravascular Ultrasound Analysis

Young Joon Hong, MD, PhD; Myung Ho Jeong, MD, PhD, FACC, FAHA, FESC, FSCAI;

Youngkeun Ahn, MD, PhD, FACC, FSCAI; Doo Sun Sim, MD; Jong Won Chung, MD; Jung

Sun Cho, MD; Nam Sik Yoon, MD; Hyun Ju Yoon, MD; Jae Youn Moon, MD; Kye Hun Kim,

MD, PhD; Hyung Wook Park, MD, PhD; Ju Han Kim, MD, PhD; Jeong Gwan Cho, MD, PhD,

FACC; Jong Chun Park, MD, PhD; Jung Chaee Kang, MD, PhD

The Heart Center of Chonnam National University Hospital, Chonnam National University Research Institute of Medical Sciences, Gwangju, Korea

● Coronary angiography

-- provides only simple, planar projections of three-

dimensional coronary lumen anatomy.

-- is limited to detect intrastent plaque prolapse (PP).

● Previous studies have shown that

-- PP is not a rare phenomenon.

-- PP has been detected frequently by intravascular

ultrasound (IVUS).

Background (I)

● It has been known that several pre-intervention IVUS

factors and aggressive stenting procedure have been

associated with PP.

● Some studies have demonstrated that PP was associated

with stent thrombosis.

● However, data on the characteristics of PP in patients

with acute myocardial infarction (AMI) are lacking.

Background (II)

Objectives

● to assess the incidence, predictors, and outcome of PP

after stent implantation for infarct-related arteries in

AMI patients.

● a total of 310 patients with a first AMI

- 125 ST segment elevation and 185 non-ST segment

elevation MI

- From January 9, 2001 to July 31, 2007

- who underwent pre-intervention IVUS within 24 hours from

symptom onset

- were stented successfully

- had post-intervention IVUS imaging

Patient Population (I)

Patient Population (II)

● Exclusion

- prior MI, subacute or late stent thrombosis, restenosis

after stenting, coronary artery bypass graft failure, patients

studied with IVUS more than 24 hours after symptom

onset,

and patients in whom adequate IVUS images could not be

obtained

● Identification of infarct-related arteries

- electrocardiographic findings

- left ventricular wall motion abnormalities on left ventricular

angiogram or echocardiogram

- coronary angiographic findings

Laboratory Analysis● Venous blood samples were obtained within 24 hours after

stenting.

● The blood samples were centrifuged, and serum was

removed and stored at -70°C until the assay could be

performed.

● Absolute creatine kinase-MB (CK-MB) levels were

determined by radioimmunoassay (Dade Behring Inc., Miami,

Florida).

● Cardiac-specific troponin I (cTnI) levels were measured by a

paramagnetic particle, chemiluminescent immunoenzymatic

assay (Beckman, Coulter Inc., Fullerton, California).

IVUS Imaging

● All IVUS examinations were performed before PCI after

intracoronary administration of 200 µg nitroglycerin

● Commercially available IVUS system (Boston Scientific

Corporation/SCIMed, Minneapolis, MN)

● IVUS catheter was advanced distal to the target lesion, and

imaging was performed retrograde to the aorto-ostial

junction at an automatic pullback speed of 0.5 mm/sec

IVUS Analysis (I) ● according to the American College of Cardiology Clinical

Expert Consensus Document on Standards for Acqusition,

Measurement and Reporting of Intravascular Ultrasound

Studies

● using planimetry software (TapeMeasure, INDEC Systems

Inc., Mountain View, CA)

-- external elastic membrane (EEM) cross-sectional area

(CSA)

-- lumen CSA

-- plaque plus media (P&M) CSA: EEM CSA minus lumen CSA

-- plaque burden: P&M CSA divided by EEM CSA

Proximal Proximal ReferenceReference

LesionLesionSiteSite

Distal Distal ReferenceReference

EEMEEM

LumenLumen

P+MP+M

Max P+M Max P+M ThicknessThickness

Min P+M Min P+M ThicknessThickness

CaCa++++

IVUS Analysis (II) ● The lesion was the site with the smallest lumen CSA

-- if there were multiple image slices with the same minimum

lumen CSA

the image slice with the largest EEM and P&M was

measured

● Plaque morphology

-- Hypoechoic plaque: less bright compared with the

reference adventitia

-- Hyperechoic, noncalcified: as bright as or brighter than

the reference adventitia without acoustic shadowing

-- Calcified plaque: hyperechoic with shadowing

: lesion contained >90° of circumferential

calcium

IVUS Analysis (III) ● Coronary artery remodeling

-- was assessed by comparing the lesion site to the

reference EEM CSA

● Remodeling index (RI): the lesion site EEM CSA divided by

the average of the proximal and distal reference EEM CSA

-- Positive remodeling: RI >1.05

-- Intermediate remodeling: RI between 0.95 and 1.05

-- Negative remodeling: RI <0.95

● Thrombus

-- an intraluminal mass

-- having a layered or lobulated appearance

-- evidence of blood flow (microchannels) within the mass

-- speckling or scintillation

IVUS Analysis (IV) ● A ruptured plaque

-- contained a cavity that communicated with the lumen with

an overlying residual fibrous cap fragment.

-- a fragmented and loosely adherent plaque without a

distinct cavity and without a fibrous cap fragment was not

considered a plaque rupture.

-- rupture sites separated by a length of artery containing

smooth lumen contours without cavities were considered

to represent different plaque ruptures.

-- plaque cavity was measured and extrapolated to the

ruptured capsule area.

Example of Plaque Rupture with Thrombus

Thrombus

Ruptured plaque cavity

Thin fibrous cap

IVUS Analysis (V)

● At post-intervention

-- minimum stent CSA

-- Percent stent expansion: minimum stent CSA divided by

mean reference lumen CSA

-- PP was defined as tissue extrusion through the stent strut

at post-intervention

-- Volume of PP: subtracting lumen volume from stent

volume

Baseline Characteristics (I)

Plaque Prolapse (n=85)

No Plaque Prolapse (n=225)

p value

Age (yrs) 65±13 65±11 1.0

Male gender, # (%) 49 (58) 130 (58) 1.0

Clinical presentation, # (%)     0.081

  Non-ST segment elevation MI 44 (52) 141 (63)  

  ST segment elevation MI 41 (48) 84 (37)  

Diabetes mellitus, # (%) 31 (37) 80 (36) 0.9

Hypertension, # (%) 64 (75) 154 (68) 0.2

Smoking, # (%) 30 (35) 75 (33) 0.7

Family history of coronary artery disease, # (%)

18 (21) 34 (15) 0.2

Previous percutaneous coronary intervention, # (%)

3 (10) 9 (8) 0.8

Thrombolytic therapy, # (%) 11 (13) 21 (9) 0.4

Glycoprotein IIb/IIIa inhibitors, # (%) 20 (24) 44 (20) 0.4

Use of distal protection devices, # (%) 12 (14) 12 (5) 0.010

Baseline Characteristics (II)

Plaque Prolapse (n=85)

No Plaque Prolapse (n=225)

p value

Aspirin at admission, # (%) 11 (13) 21 (9) 0.4

Statin at admission, # (%) 10 (12) 20 (9) 0.4

Ejection fraction (%) 46±13 43±13 0.11

White blood cells (103/mm3) 8.9±3.1 9.2±3.6 0.6

Hemoglobin (g/dl) 12.2±2.0 12.3±2.2 0.7

Platelet count (103/mm3) 220±90 231±86 0.4

Creatinine clearance (ml/min) 60±31 66±35 0.15

Total cholesterol (mg/dl) 181±47 165±42 0.029

Triglyceride (mg/dl) 132±67 127±65 0.6

LDL cholesterol (mg/dl) 110±43 100±37 0.091

HDL cholesterol (mg/dl) 45±12 42±13 0.11

Coronary Angiographic Findings

Plaque Prolapse (n=85)

No Plaque Prolapse (n=225)

p value

Infarct-related artery, # (%) 0.024

Left main 0 (0) 5 (2)

LAD 36 (42) 131 (58)

LCX 14 (17) 28 (12)

RCA 35 (41) 61 (27)

Lesion location, # (%) 0.8

Ostium 1 (1) 3 (1)

Proximal 31 (37) 90 (40)

Middle 46 (54) 109 (48)

Distal 7 (8) 23 (10)

Multivessel disease, # (%) 41 (48) 112 (50) 0.8

Thrombus, # (%) 14 (16) 22 (10) 0.10

Calcium, # (%) 7 (8) 23 (10) 0.6

TIMI flow grade 0, # (%) 19 (22) 30 (13) 0.052

Procedural Results

Plaque Prolapse (n=85)

No Plaque Prolapse (n=225)

p value

Stent type, # (%) 0.15

Sirolimus-eluting stent 35 (41) 103 (46)

Paclitaxel-eluting stent 19 (22) 30 (13)

Bare-metal stent 31 (37) 92 (41)

No. of deployed stents, # (%) 1.5±0.6 1.1±0.3 <0.001

Stent diameter (mm) 3.28±0.40 3.24±0.46 0.7

Stent length (mm) 31±13 21±8 <0.001

Inflation pressure (mmHg) 15.3±2.9 14.1±2.6 0.001

Reference diameter (mm) 3.32±0.85 3.27±0.72 0.5

Pre-MLD (mm) 0.63±0.32 0.68±0.51 0.18

Lesion length (mm) 23±12 15±8 0.001

Intravascular Ultrasound Findings Plaque Prolapse

(n=85)No Plaque Prolapse

(n=225)p value

Reference

EEM CSA (mm2) 12.8±4.6 12.9±4.7 1.0

Lumen CSA (mm2) 8.3±3.0 8.3±3.1 0.9

P&M CSA (mm2) 4.6±2.6 4.5±2.6 1.0

Plaque burden (%) 35±11 34±11 0.7

Minimum lumen site

EEM CSA (mm2) 13.1±4.1 12.3±4.8 0.2

Lumen CSA (mm2) 2.5±1.5 2.8±1.3 0.063

P&M CSA (mm2) 10.6±4.2 9.4±4.3 0.040

Plaque burden (%) 79.5±13.0 75.2±10.6 0.003

IVUS lesion length (mm) 28±12 18±8 <0.001

Calcium arc (º) 114±76 195±81 <0.001

Calcium length (mm) 3.6±2.7 5.5±3.7 0.008

Superficial calcium, # (%) 51 (60) 158 (70) 0.087

Minimum stent CSA (mm2) 8.14±2.99 7.25±2.27 0.029

Stent expansion (%) 98±25 87±29 0.014

51

31

0

15

30

45

60

PP(n=85)

No PP(n=225)

P=0.001

Plaque Rupture

(%)

21

13

0

10

20

30

PP(n=85)

No PP(n=225)

(%) P=0.089

Multiple Plaque Rupture

3.1

2.5

0

1

2

3

4

5

PP(n=85) No PP(n=225)

P=0.008

Plaque Cavity Area(mm2)

40

21

0

10

20

30

40

50

PP(n=85)No PP(n=225)

P=0.001

Thrombus (%)

9

17

13

60

9

28

18

44

0

15

30

45

60

Hypoechoic Hyperechoic,noncalcified

Calcified Mixed

PP(n=85)

No PP(n=225)

(%)

P=0.044

Plaque Morphology

Remodeling Index

1.040.98

0

0.5

1

1.5

PP(n=85) No PP(n=225)

P=0.017

15

26

50

0

15

30

45

60

Stent length (mm)

≤18 >18, ≤28 >28

(20/137)

(23/89)

(42/84)

Pla

qu

e p

rola

pse

(%

)

p<0.001

Incidence of Plaque Prolapse according to the Stent Length

38

21

0

10

20

30

40

Plaque rupture (+)

(43/112)

(42/198)

Pla

qu

e p

rola

pse

(%

)

p=0.001

Plaque rupture (-)

Incidence of Plaque Prolapse according to the Presence/Absence of Plaque Rupture

36

28

19

0

10

20

30

40

Positive remodeling

(41/113)

(21/75)

(23/122)

Pla

qu

e p

rola

pse

(%

)

p=0.011

Intermediate remodeling

Negative remodeling

Incidence of Plaque Prolapse according to the Remodeling Pattern

Changes of Cardiac Enzymes at FU

12.3 16.3-4.9 -1.5

-60

-40

-20

0

20

40

60

80

Plaque prolapse

No plaque prolapse

CK-MB cTnI

Plaque prolapse (+)

Ste

nt

thro

mb

osi

s (%

)

p=0.3

Plaque prolapse (-)

30-Day Stent Thrombosis Rate

(2/85)

(2/225)

2.4

0.9

0

1

2

3

4

5

Thrombus (OR=1.84, 95% CI 1.08-3.13, p=0.026)

Multivariate Predictors of Post-PCI CK-MB Elevation

Plaque rupture (OR=1.95, 95% CI 1.10-3.46, p=0.023)

Plaque prolapse (OR=7.34, 95% CI 3.55-15.19, p<0.001)

Positive remodeling (OR=1.72; 95% CI 1.01-2.92, p=0.044)

Multivariate Predictors of PP

Stent length (OR=2.39; 95% CI 1.17-3.89, p=0.003)

Plaque rupture (OR=1.96; 95% CI 1.14-3.37, p=0.015)

Conclusions

The incidence of PP after stenting for infarct-related artery

was 27%.

Pre-intervention IVUS lesion characteristics – plaque rupture

and positive remodeling – and longer stent length predict

PP, and PP is associated with myonecrosis after stenting for

infarct-related artery in patients with AMI.