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Interventional Neuroradiology 15: 17-28, 2009

Can Periprocedural Hypotension
in Carotid Artery Stenting Be Predicted?
A Carotid Morphologic Autonomic Pathologic Scoring
Model Using Virtual Histology to Anticipate Hypotension
A. TSURUMI, S. MIYACHI, O. HOSOSHIMA, T. IZUMI, T. OHSHIMA, N. MATSUBARA,
T. KINKORI, T. NAITO, T. WAKABAYASHI
Department of Neurosurgery, Nagoya University Graduate School of Medicine; Nagoya, Japan

Key words: carotid stenosis, stenting, carotid ultrasound, interventional neuroradiology, pathology, Virtual Histology

Summary
Periprocedural hypotension, which frequently
occurs during carotid artery stenting (CAS), is
an important risk factor for complications suchas stroke or death after CAS.
To determine if a scoring model can be established to predict periprocedural hypotension(systolic blood pressure < or = 90 mm Hg) andprolonged periprocedural hypotension (requiring vasopressor for > 3 hours) in CAS, we conducted a prospective cohort study of patients undergoing interventional treatment of cervicalcarotid artery stenosis in an urban tertiary referral hospital from April 2006 to April 2007.
Forty-eight stenotic lesions in 45 consecutive
patients treated with CAS were included in the
study. Multivariate analysis showed three independent risk factors of periprocedural hypotension; “fibrous plaque on Virtual Histology” (P =0.029), “stenotic lesion involving both the common carotid artery and internal carotid artery on
angiogram” (P = 0.004), and “patients without
history of diabetes mellitus” (P = 0.020). Further,“distance between carotid bifurcation and pointof minimum lumen size < or = 10 mm on angiogram” (P = 0.003) was an independent risk
factor of prolonged periprocedural hypotension.
Carotid morphologic autonomic pathologic
score (carotid MAPS), determined by adding
one point for each of those risk factors (total 0 to4), had good discrimination for both periproce-dural hypotension (area under receiver operating characteristic curve: ROC AUC = 0.876; SE
0.053) and prolonged periprocedural hypotension (ROC AUC = 0.811; SE 0.066).
Carotid MAPS is useful for predicting periprocedural hypotension and prolonged periprocedural hypotension during CAS.
Introduction
Carotid artery stenting (CAS) of cervicalcarotid artery stenosis has been increasingly
used as an alternative to carotid endarterectomy (CEA) 1. Several studies 2-11 have shown thatperiprocedural hypotension is more frequent in
CAS because CAS involves manipulation in
the vicinity of both the adventitial baroreceptors and the carotid sinus. Periprocedural hypotension increases in-hospital complications
and long-term risk of death after CAS 3,4. Therefore, predictive factors for hypotension havebeen evaluated in many studies 3-10. Predicting
which patients are at high-risk for periprocedural hypotension will enable us to pre-treat
them aggressively. This may, as a result, improve their prognoses.
Several studies of coronary 12-14 and carotid 15
artery plaque imaging have demonstrated that
virtual histology (VH; Volcano Corporation,
Rancho Cordova, CA), which is based on spectral and amplitude analyses of the intravascularultrasound (IVUS) radiofrequency (RF) bac-17

Can Periprocedural Hypotension in Carotid Artery Stenting Be Predicted?

kscatter signals, allows reliable identification offour atherosclerotic plaque types: fibrous, fibrofatty, dense calcium, and necrotic core. In
addition, the geometric and compositional output of VH IVUS has been reported to be reproducible 16. Therefore, VH IVUS has been applied to the evaluation of plaque characteristics
in both coronary interventions 17,18 and neurointerventions 19-21. Periprocedural hypotension in
CAS may be predicted by analyzing the plaquecomposition derived from VH IVUS.
The present study had three main aims, first
it sought to determine the risk factors forperiprocedural hypotension based on VH
IVUS, second the study aimed to develop an
accurate and simple scoring model. The third
aim was to evaluate the effectiveness of thescoring model for the prediction of periprocedural hypotension in CAS.
Methods
Study Design
We conducted a prospective cohort study ofthe patients who underwent interventional
therapy for cervical carotid artery stenosis in
Nagoya University Hospital from April 1, 2006
to April 30, 2007. This hospital is a tertiary referral center of Nagoya, a city of 2.2 million
people in central Japan. This neurosurgery department performs approximately 500 neurosurgery and neuroendovascular operations
each year.
All consecutive patients who underwent interventional therapy for cervical carotid arterystenosis in Nagoya University Hospital wereenrolled in the present study. All patients weretreated with CAS by using a balloon emboliprotection device. Patients with stenoses related to radiation therapy or with restenoses after
CEA were excluded from the present study.
The study was conducted in line with the requirements of the institutional review board.
The authors obtained informed written consent
from all individual subjects prior to the datacollection. The CAS procedures and periprocedural management were in accordance with theinstitutional guidelines.
Definition of Terms
Any episodes of hypotension (defined as systolic blood pressure < or = 90 mm Hg), hypertension (defined as systolic blood pressure> 160 mm Hg), or bradycardia (defined as heart

18

A. Tsurumi

rate < 50 bpm) from the start of the interventional procedure to the fifth postprocedural
day were recorded and defined as periprocedural hypotension, hypertension, or bradycardia, respectively. Patients who required continuous vasopressor infusion for more than threehours during and/or after the procedure wereconsidered to have prolonged periprocedural
hypotension.
Protocol for Carotid Artery Stenting Procedure
All procedures were performed under local
anesthesia. Stenotic lesions with unstable andcomplex plaque were treated with proximal
protection systems to avoid the risk of distal
embolization by advancing the protection device through the stenosis 22. The other lesions
were treated with distal balloon protection. For
prophylaxis intravenous atropine was given ata dose of either 0.25 mg (n = 3) or 0.5 mg (n =45) before predilatation 8. After predilatation, aself-expanding stent was deployed, followed bypostdilatation.
Plaque Evaluation Using Virtual Histology
A VH IVUS was obtained before predilatation with the use of a VH IVUS console (Volcano Corporation). The total volume of eachplaque type (fibrous, fibrofatty, dense calcium,and necrotic core) was calculated using VH
IVUS software (version 1.3; Volcano Corporation) and expressed as cubic millimeters. The
proportion of each plaque type was also determined.
Statistical Analysis
A univariate binary logistic regression analysis was performed to examine the effect of eachvariable on periprocedural hypotension or prolonged periprocedural hypotension. Multivariate stepwise logistic regression analysis was
performed with entry criteria of P < 0.20.
We used the receiver operating characteristic(ROC) curve to quantify how well different
scoring models could be used for the predictionof periprocedural hypotension and prolonged
periprocedural hypotension 23. Using a nonparametric method, we estimated the diagnostic accuracy of different scoring models by calculating the area under the ROC curve (ROC
AUC). We also calculated the standard error(SE) and P value (null hypothesis, H0: AUC =0.5; alternative hypothesis, H1: AUC > 0.5). The
stratum specific likelihood ratios (SSLR) werewww.centauro.it

calculated with a method described by Peirce
et Al.23. We used the logit method to calculate
the 95% confidence intervals (CI) 23. All statistical analyses were performed with the SPSS statistical software package (version 15.0; SPSS
Inc, Chicago, IL).
Results
Fifty-four consecutive interventional therapies for cervical carotid artery stenosis in 50 patients were initially included in the present
study. Since the VH analyses of the plaquewere not available, six stenotic lesions (threestenotic lesions that had stenoses that were too
severe for the VH IVUS catheter to cross before predilatation; three stenotic lesions inwhich the raw RF data captured in the VH
IVUS console could not be recorded on a digital video disc because of technical difficulties)
were also excluded. For the remaining 48
stenotic lesions in 45 patients, the descriptive
characteristics are given in Table 1.
All the patients had successful dilatation of
the carotid lesion by CAS. The mean degree of
stenosis after the procedure was 3.3% (SD: 6.2;
range: 0 to 20%). In the periprocedural period,
no patients suffered from major adverse events,
including symptomatic cerebral infarction, myocardial infarction or death. No patients needed repeated procedures or blood transfusions
after the procedure. The mean degree of stenosis at the treated side was 74.0% (SD 14.8). The
severity of stenosis ranged from 50% to 99% in
all but 1 lesion (45% stenosis). In eight cases,
the contralateral internal carotid artery (ICA)
showed > 50% stenoses (four cases had complete occlusion).
The authors performed 47 predilatation procedures. In 41 of these procedures a Submarine-Rapido balloon (INVAtec, Roncadelle,
Italy) was used. An Amiia balloon (Johnson &Johnson, Miami, FL) was used in four cases. In
two procedures a Savvy balloon (Johnson &Johnson) was used. In one case the stent was
directly deployed and predilatation was unnecessary. Forty lesions were treated with a Precise
stent (Johnson & Johnson). The other eight lesions were treated with a WallstentRP (Boston
Scientific, Natick, MA). The authors also performed 42 postdilatation procedures. In 14 ofthese procedures a Submarine-Rapido balloon
was used. In 28 procedures the authors used an
Amiia balloon. In six cases no postdilatation

Interventional Neuroradiology 15: 17-28, 2009

was performed. The mean percentages for theplaque volumes in VH were as follows: 60.98%(SD 12.90) for fibrous tissue, 28.02% (SD15.39) for fibrofatty tissue, 3.94% (SD 6.31) for
dense calcium and 7.23% (SD 8.36) for necrotic core.
Univariate Influence of Characteristics
Periprocedural hypotension and prolonged
periprocedural hypotension were observed intreating 36 of 48 (75%) lesions and in 29 of 48(60%) lesions, respectively. The variables with a
P value < 0.20 (indicated in bold in Table 1) inthe univariate analysis of periprocedural hypotension were: 1) history of diabetes mellitus(DM; risk of no history of DM > risk of historyof DM); 2) distance between carotid bifurcation and minimum lumen site < or = 10 mm onangiogram; 3) stenotic lesion involving both the
CCA and ICA on angiogram (vs. involving
ICA only); 4) length of stent used (mm); 5)
stent covering both the CCA and ICA (vs. covering ICA only); 6) length of predilatation balloon used (mm); 7) diameter of postdilatation
balloon used (mm); 8) necrotic core (%) on
VH and 8) fibrous tissue > 60% on VH. The
variables with a P value <0.20 (indicated in italics in Table 1) in the univariate analysis of prolonged periprocedural hypotension were: 1) sex(male risk > female risk); 2) distance between
carotid bifurcation and minimum lumen site
< or = 10 mm on angiogram; 3) stenotic lesion
involving both the CCA and ICA on angiogram (vs. involving ICA only); 4) stent covering both the CCA and ICA (vs. covering ICA
only); 5) type of postdilatation balloon used; 6)
diameter of postdilatation balloon used and 7)
carotid occlusion time (min). All of these variables indicated in either bold (periprocedural
hypotension variables) or italics (prolonged
periprocedural hypotension variables) were incorporated into the multivariate analyses.
Multivariate Analysis
Stepwise logistic regression analysis wasused to derive the models for periprocedural
hypotension and prolonged periprocedural hypotension. The final model for periprocedural
hypotension consisted of the following independent variables: fibrous tissue > 60% on VH,
stenotic lesion involving both the CCA andICA on angiogram, and no history of DM(Table 2). All three variables were significant
independent risk factors for periprocedural hy-

19Can Periprocedural Hypotension in Carotid Artery Stenting Be Predicted?

potension. The P value of the Hosmer andLemeshow’s goodness-of-fit test (P = 0.998)
and the Nagelkerke R-square value (R-square= 0.507) indicate a good fit of the model to thedata.
For prolonged periprocedural hypotension,
the final model consisted of the following independent variables: distance between carotid bifurcation and minimum lumen site < or = 10mm on angiogram, and no history of DM(Table 2). The distance between carotid bifurcation and minimum lumen site < or = 10 mm
on angiogram was a significant independentrisk factor for prolonged periprocedural hypotension. The P value of the Hosmer andLemeshow’s goodness-of-fit test (P = 0.827)
and the Nagelkerke R-square value (R-square= 0.315) indicate a good fit to the data.
There were no correlations between the factor of “distance between carotid bifurcationand minimum lumen site < or = 10 mm” and thefactor of “fibrous tissue > 60% on VH”(Cramer’s coefficients of association = 0.072)
nor between the factor of “distance between
carotid bifurcation and minimum lumen site
< or =10 mm” and the factor of “no history ofDM” (Cramer’s coefficients of association =0.195). The factor of “stenotic lesion involving
both the CCA and ICA on angiogram” correlated weakly (Cramer’s coefficient of association = 0.369) with the factor of “distance between carotid bifurcation and minimum lumensite < or = 10 mm on angiogram.”
Carotid Morphologic
Autonomic Pathologic Score
The four significant multivariate risk factors
identified above can have 15 possible scoringmodels. Therefore, we calculate these 15 different scoring models with the four significant risk
factors for periprocedural hypotension and/or
prolonged periprocedural hypotension. Eachscoring model presented different test results.
We analyzed the diagnostic value of each scoring model with ROC AUC as shown in Figure
1. Of the 15 scoring models, the one which included all four significant risk factors (the “FSDN” model in Figure 1) performed the best
discrimination with ROC AUC of 0.876 (SE0.053, P < 0.001; for prediction of periprocedural hypotension) and 0.811 (SE 0.066, P< 0.001;
for prediction of prolonged periprocedural hypotension). We defined this scoring model
which included all four significant risk factors

20

A. Tsurumi

as the “carotid morphologic autonomic pathologic score (carotid MAPS)” (Table 3). The
SSLRs of carotid MAPS with 95% CIs areshown in Table 4, demonstrating the discriminating power of the strata of the carotid
MAPS.
Discussion
The present study has two novel findings.
First, it shows that fibrous carotid plaque is arisk factor for periprocedural hypotension in
CAS. Second, the carotid MAPS, which includes the findings that are related to plaquemorphology, autonomic function and plaquepathology is clinically useful for predicting
both periprocedural hypotension and prolonged periprocedural hypotension in CAS.
Risk Factors for Periprocedural Hypotension
and Prolonged Periprocedural Hypotension
The present study confirmed that there arethree risk factors of periprocedural hypotension and one risk factor of prolonged periprocedural hypotension in CAS (Table 2). The
mean volume of fibrous tissue in this study was
60%. The factor of “fibrous tissue > 60% on
VH” shows that fibrous tissue is composed ofmore than 60% of the whole plaque volume. In
our study we detected that the factor of “fibrous tissue > 60% on VH” increased the riskof patients developing hypotension. Plaquethat has more than 60% fibrous tissue content
can be called fibrous plaque. Fibrous plaque isthought to create a hard surface in the circumference of the artery. As a result, carotid bulb
baroreceptors of patients with fibrous plaque
may be compressed directly and severely by dilatation balloons or stents. This may contributeto hypotension.
Our analysis has shown that patients who
have lesions involving both the CCA and ICA
are at higher risk of developing hypotension.
This result is in agreement with the results ofother studies 4,9 which reported that lesions involving the carotid bifurcation would predispose to the development of hypotension afterCAS. Nonaka et Al.11 reported, using univariate analysis, that the distance between carotid
bifurcation and maximum stenotic lesion < or= 10 mm is a risk factor for the presence of
prolonged hypotension. Our analysis has
shown that the distance between carotid bifurcation and minimum lumen site < or = 10 mm

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Interventional Neuroradiology 15: 17-28, 2009

Table 1 Association of hypotension with characteristics.

Periprocedural hypotension
Variables

Yes (n =36)

No (n =12)

Prolonged periprocedural hypotension
P valueYes (n =29)

No (n =19)

P value

Clinical characteristics
Age (years old)

68.7

(SD 7.2)

68.9(SD 6.8)

0.94

68.6

(SD 7.5)

69.1(SD 6.5)

0.79

Female (vs. male)

4

(11%)

2

(17%)

0.62

1

(3%)

5

(26%)

0.044

Hypertension

26

(72%)

7

(58%)

0.37

20

(69%)

13

(68%)

0.97

Diabetes mellitus

13

(36%)

7

(58%)

0.18

10

(34%)

10

(53%)

0.22

Hyperlipidemia

20

(56%)

8

(67%)

0.50

16

(55%)

12

(63%)

0.58

Beta blocker medication

2

(6%)

2

(17%)

0.25

2

(7%)

2

(11%)

0.66

Coronary artery disease

10

(28%)

5

(42%)

0.37

9

(31%)

6

(32%)

0.97

Myocardial infarction

5

(14%)

2

(17%)

0.81

5

(17%)

2

(11%)

0.52

Angina pectoris

9

(25%)

4

(33%)

0.58

8

(28%)

5

(26%)

0.93

Valvular heart disease

3

(8%)

1

(8%)

1.00

2

(7%)

2

(11%)

0.66

Arrhythmia

0

(0%)

1

(8%)

1.00

0

(0%)

1

(5%)

1.00

Congestive heart failure

2

(6%)

2

(17%)

0.25

2

(7%)

2

(11%)

0.6

Coronary artery
bypass graft operation

1

(3%)

0

(0%)

1.00

1

(3%)

0

(0%)

1.00

Chronic renal insufficiency

1

(3%)

1

(8%)

0.43

1

(3%)

1

(5%)

0.76

Arteriosclerosis obliterans

3

(8%)

0

(0%)

1.00

2

(7%)

1

(5%)

0.82

Malignant neoplasm

2

(6%)

0

(0%)

1.00

2

(7%)

0

(0%)

1.00

History

Preprocedural systolicblood pressure (mm Hg)

118.5 (SD 17.2) 121.8 (SD 12.9)

0.55

118.4

(SD 17.7) 120.6 (SD 13.8)

0.65

Preprocedural diastolicblood pressure (mm Hg)

65.7(SD 12.2)

67.5(SD 10.2)

0.64

65.1

(SD 12.5)

67.7(SD 10.3)

0.44

Periprocedural hypertension

5

(14%)

2

(17%)

0.81

3

(10%)

4

(21%)

0.31

Periprocedural bradycardia

5

(14%)

2

(17%)

0.81

4

(14%)

3

(16%)

0.85

Lesion side: left (vs. right)

18

(50%)

7

(58%)

0.62

16

(55%)

9

(47%)

0.60

Distance between carotid
bifurcation and MLS< or = 10 mm (vs. > 10 mm)

30

(83%)

6

(50%)

0.028

26

(90%)

10

(53%)

0.007

Plaque ulceration
deeper than 2 mm

15

(42%)

4

(33%)

0.61

12

(41%)

7

(37%)

0.75

Stenotic lesion involving
both CCA & ICA(vs. ICA only)

18

(50%)

1

(8%)

0.029

15

(52%)

4

(21%)

0.039

Degree of treated stenosis (%)

73.3(SD 14.9)

74.6(SD 16.6)

0.80

73.7

(SD 14.8)

73.4(SD 16.1)

0.95

Lesion-related characteristics

21

Can Periprocedural Hypotension in Carotid Artery Stenting Be Predicted?

A. Tsurumi

Periprocedural hypotension

Prolonged periprocedural hypotension

Variables

Yes (n =36)

No (n =12)

P valueYes (n =29)

No (n =19)

P value

Intracranial ICA stenosis,
ipsilateral

4

(11%)

0

(0%)

1.00

2

(7%)

2

(11%)

0.66

Intracranial ICA stenosis,
contralateral

2

(6%)

0

(0%)

1.00

2

(7%)

0

(0%)

1.00

Vertebrobasilar arterystenosis(> 50%)

2

(6%)

0

(0%)

1.00

1

(3%)

1

(5%)

0.76

Contralateral ICA stenosis(> 50%) or occlusion

6

(17%)

2

(17%)

1.00

6

(21%)

2

(11%)

0.36

Contralateral ICA occlusion

3

(8%)

1

(8%)

1.00

3

(10%)

1

(5%)

0.54

Symptomatic carotid
stenosis, ipsilateral

17

(47%)

8

(67%)

0.25

13

(45%)

12

(63%)

0.22

Cerebral infarction,
ipsilateral

12

(33%)

6

(50%)

0.31

9

(31%)

9

(47%)

0.26

Cerebral infarction,
contralateral

6

(17%)

1

(8%)

0.49

3

(10%)

4

(21%)

0.31

Symptoms of carotid stenosis
within 3 months, ipsilateral

7

(19%)

4

(33%)

0.33

5

(17%)

6

(32%)

0.25

Cerebral infarction within
3 months, ipsilateral

4

(11%)

3

(25%)

0.25

3

(10%)

4

(21%)

0.31

History of CAS or CEA,
contralateral

5

(14%)

0

(0%)

1.00

4

(14%)

1

(5%)

0.36

Stent used: Wallstent RP(vs. Precise Stent)

7

(19%)

1

(8%)

0.39

5

(17%)

3

(16%)

0.90

Stent diameter (mm)9.8

(SD 0.4)

9.6(SD 1.1)

0.41

9.8

(SD 0.4)

9.7(SD 0.9)

0.71

Stent length (mm)33.2

(SD 8.1)

37.0(SD 5.4)

0.15

33.9

(SD 8.1)

34.4(SD 7.1)

0.83

Stent covering both CCA& ICA (vs. ICA only)

33

(92%)

9

(75%)

0.15

27

(93%)

15

(79%)

0.17

Amiia

3

(8%)

1

(8%)

0.98

3

(10%)

1

(5%)

0.53

Savvy

1

(3%)

1

(8%)

0.44

1

(3%)

1

(5%)

0.81

No predilatation

1

(3%)

0

(0%)

1.00

1

(3%)

0

(0%)

1.00

Balloon diameter (mm)3.7

(SD 0.8)

4.0(SD 0.7)

0.34

3.7

(SD 0.8)

4.0(SD 0.6)

0.23

Balloon length (mm)29.2

(SD 7.6)

34.2(SD 6.4)

0.050

29.3

(SD 8.3)

32.1(SD 6.1)

0.23

Balloon inflationpressure (atm)

7.4(SD 2.0)

7.8(SD 1.3)

0.48

7.3

(SD 2.0)

7.8(SD 1.5)

0.35

Treatment-relatedcharacteristics

Predilatation
Balloon catheter used(vs. Submarine)22

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Interventional Neuroradiology 15: 17-28, 2009

Periprocedural hypotension
Variables

Yes (n =36)

No (n =12)

Balloon inflation
duration (sec)

33.4(SD 12.3)

31.3

Amiia

22

(61%)

No postdilatation

3

Balloon diameter (mm)Prolonged periprocedural hypotension

P valueYes (n =29)

No (n =19)

P value(SD 9.6)

0.58

33.1

(SD 12.5)

32.5(SD 10.3)

0.86

6

(50%)

1.00

19

(66%)

9

(47%)

0.13

(8%)

3

(25%)

0.21

2

(7%)

4

(21%)

0.34

4.9

(SD 1.6)

4.1(SD 2.4)

0.20

5.1

(SD 1.5)

4.1(SD 2.2)

0.10

Balloon length (mm)20.1

(SD 7.9)

18.3(SD 11.4)

0.55

20.5

(SD 7.8)

18.4(SD 10.4)

0.44

Balloon inflationpressure (atm)10.2(SD 3.7)

8.5(SD 5.2)

0.24

10.3

(SD 3.5)

8.9(SD 5.0)

0.28

Emboli-protection method:
proximal protection(vs. distal protection)

1

(3%)

4

(33%)

0.79

2

(7%)

3

(16%)

0.98

Occlusion time (min)11.0(SD 4.68)

11.6(SD 2.81)

0.68

11.6

(SD 4.70)

10.4(SD 3.45)

0.14

Fibrous tissue (%)

62.0(SD 12.4)

57.9(SD 13.4)

0.35

61.8

(SD 13.4)

59.7(SD 11.5)

0.59

Fibrofatty tissue (%)

28.6(SD 15.3)

26.2(SD 14.8)

0.63

29.0

(SD 16.8)

26.6(SD 12.3)

0.60

Dense calcium (%)

3.2(SD 3.2)

6.1(SD 10.9)

0.24

3.1

(SD 3.2)

5.2(SD 8.9)

0.33

Necrotic core (%)

6.3(SD 7.0)

10.1(SD 10.8)

0.19

6.2

(SD 7.4)

8.8(SD 9.2)

0.31

Fibrous tissue > 60%

21

(58%)

4

(33%)

0.14

17

(59%)

8

(42%)

0.27

Fibrofatty tissue > 28%

14

(39%)

6

(50%)

0.50

11

(38%)

9

(47%)

0.52

Dense calcium > 3%

13

(36%)

4

(33%)

0.86

11

(38%)

6

(32%)

0.65

Necrotic core > 7%

13

(36%)

5

(42%)

0.73

9

(31%)

9

(47%)

0.26

Postdilatation
Balloon catheter used(vs. Submarine)

Virtual Histology findingsof plaque volumetriccomposition analysis

Dichotomous variables(dichotomized at mean)

Variables with a P value < 0.20 for periprocedural hypotension (indicated in bold) and prolonged periprocedural hypotension(indicated in italics) were incorporated into the multivariate analyses.
P values were derived from the univariate binary logistic regression. Continuous data are shown as the mean (SD).
Categorical data are shown as counts (%). MLS = minimum lumen site; CAS = carotid artery stenting;
CEA = carotid endarterectomy.

is an independent risk factor of prolonged
periprocedural hypotension. We obtained thisresult by using multivariate analysis. These risk
factors cause periprocedural hypotension or
prolonged hypotension probably because of

the higher concentration of baroreceptors at
this location.
Diabetes mellitus was found to be an independent variable that reduces the risk of patients developing hypotension. This result is in23

Can Periprocedural Hypotension in Carotid Artery Stenting Be Predicted?

A. Tsurumi

Table 2 Determinants of hypotension derived from multivariate logistic regression.

Variables

Coefficient

SE

Wald

P value

OR (95% CI)

Fibrous tissue > 60% on Virtual
Histology (vs. < or = 60%)

2.54

1.16

4.78

0.029

12.69

Stenotic lesion involving both CCA
and ICA on angiogram (vs. ICA only)

4.59

1.59

8.33

0.004

98.38 (4.36 to 2220)

No history of diabetes mellitus

2.81

1.21

5.40

0.020

16.60

(1.55 to 178)

Constant

-2.69

1.28

4.45

0.035

Distance between carotid bifurcationand MLS < or = 10 mm on angiogram(vs. > 10 mm)

2.61

0.88

8.75

0.003

13.66

(2.42 to 77.2)

No history of diabetes mellitus

1.49

0.76

3.82

0.051

4.45

(1.00 to 19.9)

Constant

-2.32

0.96

5.84

0.016

Periprocedural hypotension(1.30 to 124)

Prolonged periprocedural hypotension

SE = standard error; Wald = Wald statistic; OR = odds ratio; CI = confidence interval; MLS = minimum lumen site.

agreement with the findings of another study 4that demonstrated that patients with DM areprotected from hypotension. Autonomic function is impaired in patients with DM 24. Thismay be the reason patients with DM have an
impaired ability to develop hypotension duringballoon inflation and stent deployment.

As described above, the risk factors which
we identified are in agreement with the findings of earlier studies by other authors. In addition, we identified fibrous carotid plaque as anovel risk factor of periprocedural hypotension
in CAS. This is the first demonstration of thecorrelation between the findings of Virtual His-

Table 3 Carotid Morphologic Autonomic Pathologic Score

Modality

FactorPoint

Morphology(Angiography)

Distance between carotid bifurcation and MLS < or = 10 mm
Distance between carotid bifurcation and MLS > 10 mm

10Morphology(Angiography)

Stenotic lesion involving both CCA and ICA
Stenotic lesion involving ICA

1
0Autonomic function(Patient's characteristic)

No history of diabetes mellitus
History of diabetes mellitus

10Pathology(Virtual Histology)

Fibrous tissue > 60%
Fibrous tissue < or = 60%

1
0

Total

0 to 4
MLS = minimum lumen site.

24www.centauro.it

Interventional Neuroradiology 15: 17-28, 2009

Figure 1 The receiver operating characteristic curves of all 15 scoring models showing the diagnostic value of each scoringmodel for the prediction of periprocedural hypotension (A) and prolonged periprocedural hypotension. All 15 scoring models are based on the four significant multivariate risk factors for periprocedural hypotension and/or prolonged periprocedural hypotension. The best discrimination was achieved by carotid MAPS (carotid morphologic autonomic pathologic score;
the model “FSDN”). F = fibrous tissue > 60% on Virtual Histology; S = stenotic lesion involving both the common carotid
artery and internal carotid artery on angiogram; D = distance between carotid bifurcation and minimum lumen site < or = 10mm on angiogram; N = no history of diabetes mellitus.

Table 4 Strata of carotid morphologic autonomic pathologic score and stratum specific likelihood ratios.

No of patients
Carotid MAPS

Likelihood ratio

Yes

No

Sensitivity

Specificity(95% CI)

Probability

4

3

0

0.08

1.00

> 999

1.00

3

16

0

0.53

1.00

> 999

1.00

2

15

5

0.94

0.58

1.00

(0.48 to 2.08)

0.75

1

2

6

1.00

0.08

0.11

(0.03 to 0.41)

0.25

0

0

1

1.00

0.00

0.00

(0.00 to 0.00)

0.00

4

3

0

0.10

1.00

> 999

1.00

3

13

3

0.55

0.84

2.84

(1.02 to 7.93)

0.81

2

13

7

1.00

0.47

1.22

(0.61 to 2.41)

0.65

1

0

8

1.00

0.05

0.00

(0.00 to 0.00)

0.00

0

0

1

1.00

0.00

0.00

(0.00 to 0.00)

0.00

Hypotension

Prolonged
hypotension

Carotid MAPS = carotid morphologic autonomic pathologic score

25

Can Periprocedural Hypotension in Carotid Artery Stenting Be Predicted?

tology and periprocedural clinical course in patients undergoing neurointerventions. The result of the present study indicates the usefulness of plaque evaluation with the use of VH
IVUS in neurointerventions as well as coronary interventions.
Clinical Usefulness of the Carotid
Morphologic Autonomic Pathologic Score
The carotid MAPS is clinically useful for predicting both periprocedural hypotension andprolonged periprocedural hypotension in CAS.
Periprocedural hypotension and prolonged hypotension, which often occur in CAS 2-6,11, are important risk factors for complications such as
stroke or death after CAS 3,4. Predicting periprocedural hypotension and prolonged hypotension may be important for preventing complications in CAS. In addition, identification of patients at high risk has gained more importancebecause of the possibility of same-day discharge
for some of these patients 25.
We propose the use of carotid MAPS, which
includes the findings that are related to plaquemorphology (angiography), autonomic function(history of DM), and plaque pathology (Virtual
Histology). We evaluated the 15 different scoring models based on the four significant multivariate risk factors (Figure 1). As a result, thecarotid MAPS (Table 3) was determined to be
the best. The carotid MAPS can significantly
predict both hypotension (P < 0.001) and prolonged hypotension (P < 0.001) in CAS.
We evaluated the SSLRs of carotid MAPS
(Table 4) for clinical use. With the use of
SSLRs, carotid MAPS is generalizable to the
CAS procedures with the wide variation inprevalence of periprocedural hypotension invarious hospitals. According to Bayes’ theorem, the probability of the presence of theevent (periprocedural hypotension or prolonged periprocedural hypotension) is calculated with the formula:
PROB = SSLR / (SSLR – 1 + 1 / PREV)
where:PROB = the probability of the presence of theevent in CAS
SSLR = the likelihood ratio of the carotid
MAPS of the patient
PREV = the prevalence of the event in a given
hospital

26

A. Tsurumi

For example, the prevalence (PREV) of prolonged hypotension in our hospital is 0.60. Fora patient with a carotid MAPS 3, the likelihood ratio (SSLR) is 2.84 for prolonged hypotension. Therefore, the probability (PROB)of the presence of prolonged hypotension is
calculated as 0.81, i.e. the probability that thepatient suffers from prolonged hypotension after CAS will be 81%. Note that the prevalence(PREV) of hypotension or prolonged hypotension differs from one hospital to another.
By contrast SSLRs are universal because eachscoring model has fixed sets of sensitivity andspecificity. However, the probability of thepresence of the event (the positive predictive
value) depends upon the prevalence of theevent in a given population. As describedabove, the carotid MAPS can predict both
periprocedural hypotension and prolonged
periprocedural hypotension. In addition, withthe use of SSLRs, carotid MAPS is generalizable to the CAS procedures in other hospitals.
In light of these results, carotid MAPS will beclinically useful for predicting both periprocedural hypotension and prolonged periprocedural hypotension in CAS.
Limitations of the Present Study
There are some weaknesses in our study.
The first is that the number of patients in thepresent study is relatively small. The series of
48 CAS procedures in 45 patients had sufficient power for the construction of the good-fit
multivariate logistic regression models. However, a larger series may help to identify better-fit multivariate models with a more accurate and simpler scoring model. The second
weakness is that the present study was performed in a single center. Although SSLRs canbe applied to other hospitals, it is more complicated to calculate the probabilities of the presence of hypotension and prolonged hypotension with the use of SSLRs. After a consensus
is reached on periprocedural management andCAS procedures, the wide variation of theprevalence of hypotension among the hospitals will decrease. The third is that the carotid
MAPS should also be evaluated with use of atest set. We are conducting an ongoingprospective clinical study to describe the discrimination ability of the carotid MAPS. The
forth is that a VH IVUS catheter has a short
detection range (10 mm in diameter). We wereable to evaluate the plaque only within the de-www.centauro.it

tection range. The development of new VH
IVUS catheters with longer range is needed
for the more accurate evaluation of carotid
plaque. The fifth is that it is unclear whether
pre-treating high-risk patients aggressively
may prevent hypotension or prolonged hypotension, and subsequently reduce the risk ofadverse vascular events. Further investigationis required with respect to the effects of predicting hypotension on the prognoses of thesepatients. The results of the present study may
contribute to the improvement in prognosis
and comfort of patients undergoing CAS.
Identifying the patients at high risk of periprocedural hypotension will enable them to receive stricter periprocedural management that

Interventional Neuroradiology 15: 17-28, 2009

may result in further improvement in patient
prognosis in CAS. Moreover, the results of thepresent study may allow patients at low risk ofperiprocedural hypotension to undergo ambulatory CAS. Consequently, this will enhance
the applicability of CAS by increasing patient
comfort and potentially reducing procedural
costs.
Conclusions
The results of the present study indicate thepossible use of the carotid MAPS in discriminating patients at high or low risk of periprocedural hypotension and prolonged periprocedural hypotension in CAS.

27

Can Periprocedural Hypotension in Carotid Artery Stenting Be Predicted?

A. Tsurumi

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Shigeru Miyachi, M.D.
Department of Neurosurgery
Nagoya University
Graduate School of Medicine,
65 Tsurumaicho, Showaku
Nagoya 466-8550, Japan.
E-mail: smiyachi@med.nagoya-u.ac.jp