Angiographic Vatia
After Successful Single-Vessel
V&i&
BENNO
J. RENSING,
PIM J. DE FEYTER,
Ratrerdom.
MD,
MD,
WALTER
FACC,
R. M. HERMANS.
PATRICK
W. SERRUYS,
MD, JAAP
MD, PH,,,
VY. iX
FACC
The Netherlmds
Ubjechws. The Fiat of (his study was to determine which
qunntltative angiographic variable hes!describesfunctional s&tas
4 mnnths alter coronary balkon angiaplasty.
B&@mmd.
Several angiographic resten& criteria have
been developed. Thesecan be divided into (hose that describe the
chge in lesion severity and lhose that merely describe lesion
severity at follow-up mgiogtnphy. The functional signikance of
thesecriteria ls un!umwn.
MeUn&. We studied 350 paients with single-ves%l cmmwy
artery dim
who underwent a singk-site bakmn dilation. Sm.
tivity and specilicity curw were const~ckd I& thp @i&on
of rqhml status md en&se ekctrowdkgrapby
of four quanUtalive att&rqhic
variahl~ that describe resknosis. The point
of high& diqnmlic amtracy for the variaMes was dekrmined al
the i&rsectktl of the semitivily nodspxikity curves.
Rf!adts
of
exerciseekamurdiagnphywereeansidered
indkattve
for ischemia6 monthsafterar@@sty if t~rizentalor dowoskping ST
segment deprasim el mmaaxrrcd.
for dkgnostk aeeursq
varisbles were oblrdned
ers of ischemia suggsls
or inereose iit hion severity in majw epkardkl VW& at ahi&
wonary flow reserve is unabk to lneet myowdkI dcrrulsds.
Soon after the introduction of percutaneous ttansluminal
coronary balloon angioplasty the vexing ptobtem of restenasis became apparent. Approximately 30% to 40% of patients will show functional or an&graphic signs, or both, of
restenosis in the tist months after a successful angioplasty
procedure. A multitude of angiographic reslcnosis criterk
have been developed over the last I2 years (1). Restenosia
criteria currently in use ELUI
be divided In
those that
describe ihe change in lesion severity Lam the postangiop&y situation up to the follow-up angiognm and those tha?
meraly describe lesion severity at follow-upangiography. An
example of the first category is the loss in lumen diameter of
X1.72 mm as proposed by Serrttys et al. (Z), and ai -Y-‘~
of the latter category is the criterion of >50% diameter
stenosis at follow-up. Criteria that describe a change in
lumen diameter may ignore the functional significance of
the lesion at follow-up, especially in large vessels (3),
whereas criteria that only describe the situation at follow-up
Manuscript received December 17, 1991; revised manuscript received
July 6, 15% accepted July 14. 15%
Addrcrsrorcoricrwndence:
Patrick W. S:m~ys, MD, PhD. Cntheterizs
lian L&raton,Thordxccnter.
Erasmur University. P.O. Box 1738.3M DR
Rottcrdam. ‘be Nethtrlandr.
severity (change in minimal lumen diameter, change in
percent diameter stenosis) and variables that merely describe lesion severity at follow-up angiography (miniinn
lumen diameter and percent diameter stenosis).
to
, *n.q,.”
will preselect lesions with a suboptimal result after angioplasty and thereby disregard the magnitude of the reactive
intimal hyperplasia
[I). Recurrence
of a flow-limiting
stenesis can usuallybe identified by symptoms of chest pain
similar to those that occurred before angioplasty. In addition
to the medical history, exercise electrocardiogtaphic (KG)
testing is generally performed as a noninvasive approach to
con&m the recurrence of a coronary artery obstruction
t,ecause it is a relatively simple, safe and inexpensive test.
To determine which quantitative angiogaphic variable best
predicts the functional status of the individual patient, we
studied the recnrrenee of anginal complaints and positive
ECG exercise test results 6 months after successful anginplasty in a selected patient group with single-vessel disease
and single-site dilation. The functional variables (recurrence
of angina and a positive exercise test result) were correlated
with quantitative angiogmphic variables of change in lesion
57.07. (67 of IBll
28.7Tc (25 of $7)
38.7% (14 of 62)
of the gain achieved at angioplasty WHLBI
4); 5) increase of
lesion severicy tc‘ 2-B?% diameter stenosis at follow-up: and
6) deterioration in minimal lumen diameter of ~0.72 mm
from immediately postangioplasty to follow-up. The latter
criterion is based on the long-term variability of minimal
lumen diameter measurements using the CAAS system
(0.36 mm). This variability is
of the mean difference of
two measurements of the same lesion filmed at two catheterization sessions an average of 90 days apart 15). This
long-term variability reflects the long-term random variation
in lesion measurements from coronarv aneioenms made at
different catheterization sessions us& the 2AA.S sy~tcm
(5). The use of SD would include 68.3% of the variability.
while the use of 2 SD (2 x 0.36 = 0.72 mm) includes 95.5%
of the variability.
0.91’
I $3
I
Results
Table I summarizes the baseline characteristics of the 350
study patients. No differences were found in the proportion
of patients with recurrent angina and ST depression at
exercise with respect to the vessel dilated (Table 2). The
occurence of Q waves in the area supplied by the dilated
artery as an indicator of pnor transmural infarction (Table 2)
was low.
Recurrent an@na and qumtitative an’&raphy.
At follow-up 102 (29%) of 350 patients had recurrent angina.
Percent correct classitka!ion Fif recurrence of angina (sensitivity) and percent correct classikation of absence ofangina
at fallow-up (specificity) as a function of cutoff points for the
different quantitative angiographic variables are given in
Figure I. The point of intersection of the sensitivity and
specificity curves represents the cutoff point for which
diagnostic accuracy was best. The static variables of minimal lumen diametct
follow-up and percent diameter
stenosis at follow-up performed equally well with a sel4ivity and specificity slightly >70% at cutoff points of I .45 mm
and46.5%, respectively. Variables that reflect the change in
lesion severity from immediately postangioplasty to follow-up performed on!y slightly less favorably. vritk a sensitivity and specificity of just <7&% at cutoff points of
-0.30 mm for the change in minimal Idmen diameter and
at
-10% for the change in percent diameter stenosis. To
compare the diagnostic accuracy of the different variables,
receiver operator characteristic (ROC) curves were EMIstrttcted (Fig. 2). Quantitative angiographic variables denoting a change in lesion severity arc only slightly less accurate
than those that denote a static measurement of lesion severity at follow-up.
Pasitive exereisa test and quantitative angiopphy.
The
exercise lest result was abnormal in I16 patients (35%).
Percent correct classification for an abnormal test Wnsitivity) and percent correct classification for a normal test
(specificity) as a function of cmoff points for the different
quantitative angiographic variables are given in Table 3. It is
clear that the diagnostic accuracy of exercise testing was
lower than for anginal status at follow-up. The optimal
combination of sensitivitv and saecificitv was 44% fo: all
angiographic variables, with the’static vsiables performing
slightly better
the variables of change (Table 3). How&r, the cuto~Tpoints associated with the point of interscction of ihe sensitivity and specificity curYes were similar to
those obtained with anginal status. This was 45.5% diameter
stenosis at follow-up, 1.46 mm minimal lumen diameter at
follow-up, achange of 10% in diameter stenosisand a change
of 0.32 mm in minimal lumen diameter. The RDC curves for
the different quantitative angiographic variables are shown
in Figure 3.
fkurrenr
angina* pnsitiwe exercise test MUR and mterk
ask criteria in current me. Tables 4 and 5 list the sensitivity.
specificity and predictive values for recurrent angina and a
positive exercisetes( result of different previous:yproposed
than
diameter stemsis (%)
restenosis criteria. None of the criteria predicted recurrent
angina and positive exercise test results with great accuracy.
In particubs a posirive exercise lest result was very hard to
predict with all angiographic restenosis criteria. Criteria that
require a large change INHLBI
1 and the 20.72mm
triterion) and the NHLBI
2 criterion that requires an extraordinary high diameter stenosis at follow-up had a low sensitivity. In fact, the NHLBI
2 crikrion is more a predictor of
total occlusions because 22 of 26 lesions that fulfilled this
criterion were totally occluded at follow-up. Among the 330
patients who underwent exercise testing, 19 of the 22 lesions
that fulfilled the NHLBI 2 criterion were totally occludd at
follow-up. The NHLBI
3 and 4 criteria and the 250%
diameter stenosis criterion Performed better. The 50% diameter stenosis cutoff point lies close to the optimal cutoffpoint
of 46.5% and is therefore one of the best predictors of
recurrent angina or a positive exercise test r&It
whereas
the NHLBI
criterion (change in diameter stenosis ~30%)
and the ~0.72~mm criterion are clearly remote from the
optimal cutoff points of - IW and -0.32 mm, respectively
(Fig. 1, C and D, Table 3).
Diagnostic aecuraey of quantitative anglography tn large
Venus small vessels. Coronary artecies taper from proximal
IO distal. The comparison of proximal with distal coronary
1
Figure I. Percent correct cla5rilication of recurmx of angina (sensitivity [&us] %, darker
curve) and percent correct classification of ab
sence of angina at follow-up (specificity [Spec]
%, lighter curve) as a function of cutoff points
for the different quantitative angiograpbic vtiables. The point of intersection of the two
wwes denotes the cutoff point with the hiiest
diaauodc accuracy. Where appropriate. the
50% diameter stenosis and the 20.72.mm
loss in minimal lumen diameter [MLD] r&enosis criteria were drawn in the figure. A, Curves
for minimal lumen diameter at follow-up.
8, Curves for percent diameter stenosis at
f&w-up.
C, Curves for change in minimal
lumen diameter at follow-up. D. Curves for
change in percent diameter stenosis (DS) al
follow-up.
Figure 2. Receivaoperalorchamcleristic furverforcomparison of
the diagnostic accuracy of an&al stagesat follow-up for minimal
Minimal lumen diameler
bum)
Diamelerstenosis (%)
Change in minimal lumen
&am&3 (InIn,
Change in diameter
stenc5is(%)
*Paintat which sen&ivity equalsspecificity.At lhepoint of intersection.
dimrustic accuracy is rlaximal and sensitivity= speclficily.
vessels carries the disadvantage of grouping together vessels
of diierent diameter. To study whether the quantitative
angiogragbiL values found apply io bo::h large nnd small
vessels we determined the points of intersection of the
sensitivity and spci$city curves for all four measuremems
of restenosis. The vessels were therefore divided into two
equally large groups according to fhe reference diameter so
that each g~oup contained 50% of the study ressels (Table 6).
Large -JesseIs had a reference diameter 22.63 mm (n = 176)
and small vessels had a reference diameter ~2.63 mm. The
point of intersection of the sensitivity and specificity curves
of the absclute diameter at follow-up was the only quantitative angiographic cutoff point that was diierent in large
vessels as compared with smaller vessels.
Diiussion
Patienl
sekctian
and methodologic considerations. In this
study we preferentially studied patients with single-vessel
disease and with a single lesion that was successfully dilated.
In these patients only restenoais of this lesion can be held
responsible for an abnormal ECG response at follow-up
exercise testing or recurrent angina. whereas in multivessel
disease the responsible lesion is not always easily idcntifiable. Moreover, coronary angioplasty in multivessel disease
will not result in complete revascularization in a considerable number of cases (IO).
With conventional exercise protocols, ECG leads and
ECG criteria, exercise testing is characterized by a high
specificity and a moderate sensitivity (Ii). Furthermore, its
sensitivity increases with the extent of coronary artery
disease, which implies a low sensitivity in patients with
single-vessel disease (12-14). This explains the low predictive accuracy found in our population of patients with singlevessel disease for the diierent restenosis criteria. These
findings are comparable with the findings of Bengtson et al.
(IS), who found a sensitivity of 32% and 9 specificity of 79%
for a positive exercise ECG.
It is known that diagnostic accuracy for restenosis of
recurrent angina is better than for ST segment change
(15,16). From the data of Benglson et al. (15). a sensitivity
for recurrent angina of 5% and a specificity of 73% can be
Figure 3. Receiver
opaator
characteristic
wrwfor comfison
of
the diagnostic xcuracy of exercise electrocardiogmphy
for minimat
lumen diameter at followup
(kavy S&I Ike)+ percent diameter
stznkr at f&w-up
(lk& z&d IW.
change in minimaI lumen
diameter (dasknl Ibe with sqa&
and change in percent diameter
stenosis (d.Wed liw with Merkks).
calculated. They applied the 50% diameter crMon
for
restenosis. Zaidi et al. (17) reported a sensitivity of 70% and
a specificity of 66% for recurrence angina as a test for
restenosis.
Although the predictive accuracy of quantitative
angiographic variables was generally poor in the present
study. it is remarkable that the points of intersection of
sensitivity and specificity curves were similar for two different markers of myocardial ischemia.
Angioplasty of the left anterior descending artery made
up 55.4% of all procedures in this study. It might be argued
that the IaEe mass of mylcardium supplied by this artery,
which is potentially iscbemic in case of severe renarrowing.
would render the tindings of this study applicable only to left
anterior descending artery lesions. However, no dlerences
were found in the proportion of patients with recurrent
angina and ST depression at exercise whh respect to the
vessel dilated (Table 2). prior myocardial infarction is known
to falsely increase the accuracy of exercise testing (18).
However, the occurrence of Q waves in the area supplied by
the dilated artery (Table 2) was low, indicating only a small
possible influence on our findings.
Angiographic r&en&s and funclid
st&us. Reslenosis
after a successful angioplasty procedure is now viewed as a
fibroproliferative repair process in response to traumatic
injury to the vessel wall (19,20). We recently showed that
lumen narrowing after angioplasty Occurs to a certain exten!
in all dilated lesions (21) and that angiographie resrenosis is
the tail end of a normally distributed phenomenon. The
restenosis
rate is then dependent on the cu10iT criterion
applied. Generally two types of angiographic restenosis
criteria have been developed: criteria that denote the change
the
322
RPNSlNO
ET AL.
ANO,mK*PHY
AND
T&k
4. Diagnostic
Accuracy
lSCHEMlA
AFTER
ANGlDPLASTY
of Different Angiegraphic RestenosisCriteria for Patients With Recurrent Angina
CrilUiOll
Spccificily
PVP
WN
95.6%
I237 of 248)
12.5%
(29 of 40)
76.5%
(237 oi 310)
NHLB, 2
NifLBi 3’
NHLBI 4.
250% DS
20.72 mm
7.4%
(26 of 350)
20.6%
(21 of 102)
98%
I243 of 248.1
80.8%
31.2%
(MY of 30)
t4.8W
(62of 102)
81%
12w of 247)
56.9%
(62of IWi
83.3%
(2@3OE240)
34.7%
(121of 149)
&.7%
(66of 1112)
77.7%
[I92 oil411
54.5%
31.7%
(Illof
63.7%
(65 of 102,
81.5%
(202of 248)
58.6%
17.7%
(62 Of3501
lY.2%
&loOf lo?)
91.1%
(226 of 248)
166of 121)
84.2%
(I92 of 2181
(65 of
84.5%
(202or 239)
(21 of 26)
77.3%
(243 of 314)
in stenosis severity at follow-up angiography (e.g., the
r0.72-mm change criterion) and criteria that assess stenosis
severity at follow-up angiography (e.g., the 150% diameter
stenosis at follow-up criterion). From a functional aoint of
view restenosis can be detected by recurrence of an, +a and
by several noninvasive tests. These tes!: ?re anaed at
detecting myocardial ischemia due to a flow-limiting
stenosis
artery and give no informaticb
on the
magniiude of the lumen-narrowing process in the individual
lesion. An&graphic
restenosis criteria that give a static
assessment of lesion severity at iolow-up
have the disadvantage of presetecting lesions with a marginal angioplasty
result (I). This means that these lesions have to undergo only
a small deterioration to cross the cutoff point and be classified as “restenosed.” Classically the 50% diameter stenosis
criterion is applied to classify lesions or patients as “restenosed” at follow-up angiography after angioplasty. This
definition is historically based on the physiologic concept of
coronary gow reserve introduced by Gould and others (22) in
1974 and is taken because it represents the approximate
value in animals with normal coronary arteries at which
in an epicardial
TaMe 5. Diagnostic Accuracy of Dierent
at Follow-Up
1III
61.5%
of 62)
78.5%
(226ol 2%)
I40
blunting of the hyperemic response occurs. Although the
50% diameter stenosis criterion is attractive because it links
the angiographic appearance of a lesion with the clinical
situation of the patient, it tells us nothing about the dynamic
behavior of the restenosis process. Our findings underscore
the significance of the 5056 diameter stenosis criterion because the optimal cutoff point for prediction of functional
status 6 months after coronary angioplasty was found to be
close to this value (46.5% diameter stenosis). However,
diagnostic accuracy of ihe absolute stenosis diameter at 6
month follow-up was similar to percent diameter stenosis
(Fig. 2 and 3) with a point of intersection of the sensitivity
and specificity curves for both angina1 status and exercise
test results at approximately
I.45 mm. This observation
indicates that ao absolute measure of stenosis severity is
equally predictive of clinical status after angioptasty as a
relative measurement. These values correspond well with
the findings of Wilson et al. (23). They found that coronary
Bow reserve dropped below 3.5 (the lower threshold of
normal) at a minimal cross-sectional area of I.5 mm2 and a
percent area stenosis of 75%, which corresponds to a mini-
Angiograptlic Restenaais Criteria for Patients With a Positive Bicycle Ergometry Response
ClifUtOil
Characteristic
Prevalence of reslenoris
Scnsilivity
Specificily
PVP
PVN
NHLBI
1
11.2%
(37 of 330)
14.7%
11701116)
9C.15
‘!94 d 214)
45.%
(17 of 371
66.2%
(1Y.iof 293)
NHLBl2
6.7%
(22 of 130)
9.5%
(II of 1161
94.%
(203 of 2141
sD9F
(II or221
BS.Y’%
no3 Of3081
NHLBI 3’
30.7%
(101 of 329)
37.9%
(44 of 116)
73.2%
(I56of213)
43.6%
(44 Of 101)
68.4%
(156of 2281
NHLBI 4’
a5G%DS
zo.72 mnl
34.7%
I4 of 3291
46.5%
(5: of 116)
71 .a%
(IS3 al 2131
41.4%
31.2%
I103 of 3343)
41.4%
148 of I lb)
74.3%
(I59 of 214)
46.6%
17%
(S6 of 3301
26.1%
(3lafll6)
88.3%
(I89 or 214)
55.4%
(54 of 114)
71.2%
I153 or 215)
I48 of 1031
7o%
(159of 227)
(31 Of56)
6%
,189 of T14)
(I
<z 61 mm
1ajmm
Change in Mismd
-0.41 (II = 169;
-0.17 mm tn = 174
-0.30 In = 1611
mat lumen diameter of 1.4 mm and a percent diamctcr
stenosis of 50%. respectively. Wijns et al. (24) demonsimted
a steep increase in pressure drop over Left anterior descending artery stenoses once a Critical value of minimal crosssectional atea of 2.5 mm* was reached. This corresponds to
d minimal lumen diameter of 1.78 mm. The pressure measurements were made with a dilation catheter across the
stenosis (cross-sectional areaaf catheter = 0.64 mm’). If this
value is subtracted from the 2.5mm* value, a minimal Lumen
diameter value of 1.54 mm emerges, which is close to the
1.45 mm found in the present study.
An approach that more closely retlects the magnitude
of the reactive intimal hyperplasia after angioplasty is applying criteria that describe the change in lesion severity at
follow-up angjography. The major critique of this type of
criterion is that it might disregard the functional significance
of a lesion at follow-up. For instance a lesion with a
postangioplasty percent diameter stenosis in the range of0 to
15% can undergo a large deterioration and still not he flow
limiting, However, our study shows not only that the static
variables of minimal lumen diameter and percent diameter
stenosis perform equally well in predicting .clinical significance of a lesion 6 months after successful caronary angiap!asty, but also that the variables of change in lumen
diameter and change in percent diameter stenosis were only
slightly less accurate in predicting the clinical significance of
the lesions (Fig. 2 and 3). Therefore, variables of change.
apart from their usefulness in reflecting the magnitude of the
reactive hvmrolasia. also reflect nearlv to the same extent as
the static vatiables,‘the clinical signif;cance of the lesion at
follow-up. The optimal cutoff point for the variables of
changewas -0.36mm for the changein lumen diameter and
-10% for change in percent diameter stenosis with nearly
equal diagnostic accuracies showing that absolute change in
lesion severity (in mm) and relative changein lesiou severity
(in percent) perform equally well in the prediction of recur-
.. .
Lumen mameter
-0.z I”nl I” 7 ,761
rent angina or a positive exercise ECG response 6 months
after coronary angioplasty.
Liiitatious uf the &rQ_ Fin:, arc.-e sophisticated invasive and noninvasive methods are available for the assessment of the functional significance of a coronary stenosis. It
is known that exercise thallium scintigraphy has a higher
diagnostic accuracy than does ECG exercise testing (25).
The present data originate from a multicenter trial and
therefore it is logistically diicuh to srandardiie the methodology of radionuclide exercise tests or flow reserve measurements in all panicipatirtg centers. Exercise ECG testing
on the other hand is inexpensive and safe, and identical
exercise protocols can be easily implemented in the participating centers. As proposed by Popma et at. (26). paired
stress tests (shortly after angioplastyand at 6 monthsfollow
up) should ideally be obtained, otherwise the interpretation
of au ischemic exercise test at foltow-up may be more
ditfrcult, especially in patients with multivessel coronary
artery disease. Our study group consisted of patients with
single-vessel disease in whom complete revasculatization
was achieved. However, the absence of myocardial ischemia
at hospital discharge after angioplasty was not objectively
confirmed by exercise testing. The diagnostic accuracy of
quantitative angiographic variables for the prediction of
recurrent angina and an abnormal ECC response at exercise
was not very high. Nevertheless, the absolute values of
sensitivity and specificity were not crucial to this study, hut
rather tbe point of intersection of the sensitivity aad specificity curves. Angina! medication was not standardized in
this study. This factor might have influenced the assessment
of functional status; however, an attempt was made to
withdraw antianginal medication at least 24 h before exercise
testing. Finally, all angiograms were preceded by an intracoronary dose of nitrates and not all patients were using
vasodilator drugs at the time of exet-cise testing, This factor
might have shifted the points ofintersection toward a higher
minimal
lumen
diameter
and a lower
percent
diameter
ste-
nosis.
number of patients studied and
the fact that the same optimal values for diagnostic accuracy
of the various quantitative am&graphic variables were obtained for the prediction of two diierent markers of ischemia
(angina1 status and ST depression at exercise) suggest that
these values reflect the lesion severity or increase in lesion
severity in major epicardial vessels at which coronary flow
reserve is unable to meet myocardial demands. Relative
measurements (percent diameter stenosis) and absolute measurements (minimal lunen diameter) were found to be
equally predictive of isI .lemia. Because the minimal lumen
diameter is the most txxnbiguous measurement of lesion
severity (independent of an arbitrary normal part of the
artery), this measmc can be a more reliable sumgate for
clinical outcome than the classic percent diameter stenosis
measurement in the many restenosis prevention trials with
drugs and new devices currently underway or in the design
phase.
Conclusions.
The
large
Tbc technical asririance oflaap Pamc~er is aratefullv acknwkdwd.
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