(Circulation. 2001;103:2928.)
© 2001 American Heart Association, Inc.
Clinical Investigation and Reports |
From the Catharina Hospital, Eindhoven, the Netherlands (G.J.W.B., N.H.J.P., E.B., J.J.K.); Cardiovascular Center, Aalst, Belgium (B.D.B, J.B., W.W.); Academic Hospital, Maastricht, the Netherlands (E.D.d.M.); Isala Clinics, Zwolle, the Netherlands (J.C.A.H.); Academic Hospital, Utrecht, the Netherlands (P.R.S.); and Hospital Universitario San Carlos, Madrid, Spain (J.E.).
Correspondence to Nico H.J. Pijls, MD, PhD, Catharina Hospital, Department of Cardiology, PO Box 1350, 5602 ZA Eindhoven, The Netherlands. E-mail Nico.Pijls{at}inter.nl.net
| Abstract |
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Methods and ResultsIn 325 patients for whom PTCA was planned and who did not have documented ischemia, FFR of the stenosis was measured. If FFR was >0.75, patients were randomly assigned to deferral (deferral group; n=91) or performance (performance group; n=90) of PTCA. If FFR was <0.75, PTCA was performed as planned (reference group; n=144). Clinical follow-up was obtained at 1, 3, 6, 12, and 24 months. Event-free survival was similar between the deferral and performance groups (92% versus 89% at 12 months and 89% versus 83% at 24 months) but was significantly lower in the reference group (80% at 12 months and 78% at 24 months). In addition, the percentage of patients free from angina was similar between the deferral and performance groups (49% versus 50% at 12 months and 70% versus 51% at 24 months) but was significantly higher in the reference group (67% at 12 and 80% at 24 months).
ConclusionsIn patients with a coronary stenosis without evidence of ischemia, coronary pressurederived FFR identifies those who will benefit from PTCA.
Key Words: coronary disease angioplasty pressure blood flow
| Introduction |
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Retrospective studies suggest that deferral of angioplasty in patients with FFR >0.75 is safe and results in an excellent clinical outcome.6 8 This has never been investigated, however, in a prospective study. Therefore, the present randomized study was undertaken in patients referred for PTCA without documented ischemia to investigate whether FFR discriminates patients in whom PTCA is appropriate from those in whom it is not.
| Methods |
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Randomization
Figure 1
depicts the flow chart of the study. Just before
the planned PTCA procedure, all patients were randomized to deferral or
performance of PTCA. After intracoronary administration
of 200 µg of nitroglycerin, control angiograms were
made, followed by measurement of FFR (see below). If FFR was >0.75,
randomization was applied. If FFR was <0.75, randomization was ignored
and PTCA was performed as planned. This resulted in 3 groups of
patients: (1) patients with FFR >0.75 in whom PTCA was deferred
(deferral group); (2) patients with FFR >0.75 in whom PTCA was
performed (performance group); and (3) patients with FFR <0.75
in whom PTCA was performed nevertheless (reference group).
Randomization was performed before coronary
catheterization, and thus before FFR measurement, for 2
reasons: first, to avoid selection bias by exclusion of eligible
patients by the operator after FFR had been determined; and second, to
account for possible complications related to the performance
of the pressure measurement itself.
|
Coronary Pressure Measurement and
Calculation of FFR
Coronary pressure measurement was performed
with a 0.014-in pressure guidewire (Radi Medical
Systems). The wire was introduced through a 6F or 7F
guiding catheter, calibrated, advanced into the coronary
artery, and positioned distal to the stenosis as described
previously.6
Adenosine was administered to induce maximum hyperemia,
either intravenously (140 µg ·
kg-1 ·
min-1) or intracoronary (15 µg
in the right or 20 µg in the left coronary
artery).9 10 FFR
was calculated as the ratio of mean hyperemic distal
coronary pressure measured by the pressure wire to mean aortic
pressure measured by the guiding
catheter.6 The measurement
was performed twice, and FFR was taken as the average of both
measurements. Next, optimum PTCA was performed in patients in the
performance and reference groups according to the local routine
of participating centers. The performance of further
coronary pressure measurements during the procedure was not
allowed.
End Points and Follow-Up
Clinical follow-up was performed at hospital
discharge and after 1, 3, 6, 12, and 24 months. The primary end point
was absence of adverse cardiac events during 24 months of follow-up.
Adverse cardiac events were defined as all-cause mortality, myocardial
infarction, CABG, coronary angioplasty, and any
procedure-related complication necessitating major intervention or
prolonged hospital stay. Myocardial infarction was defined as the
development of pathological Q-waves on the ECG or an increase of serum
creatinine kinase levels to more than twice the normal
value.11 12 An
independent end-points committee reviewed all events, and
analysis was based on the committees classification of
events. Secondary end points included freedom from angina (Canadian
Cardiovascular Society class I) at 1, 3, 6, 12, and
24 months of follow-up and the use of antianginal drugs. Repeat
coronary angiography was only performed if clinically
indicated. Decisions regarding additional treatment and medication
during follow-up were entirely at the discretion of the referring
cardiologist.
Statistical Analysis
All comparisons were made on an intention-to-treat
basis. Comparisons between continuous data were tested by use of paired
and unpaired t test.
Categorical data were tested by use of Fishers
exact test or
2 test and McNemars test.
Patient survival curves for absence of adverse cardiac events were
constructed according to the method of Kaplan and Meier and compared by
the log-rank test. A P value
<0.05 was considered significant; all tests were 2-tailed. Values are
presented as
mean±SD.
| Results |
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In-Hospital Adverse Events
Table 3
shows in-hospital adverse events. None of the
patients in the deferral group had an in-hospital event. In the
performance group, 5 patients (5.5%) had an in-hospital event
(P=0.03 for comparison with
deferral group). In the reference group, 12 patients (7.6%)
experienced an in-hospital event (no difference versus
performance group,
P=0.61;
P=0.004 for comparison with
deferral group).
|
Long-Term Follow-Up
Complete follow-up was obtained in 325 patients (100%)
after 12 months and in 317 (98%) after 24 months. As presented
in
Figure 3
, event-free survival was 89% in the deferral group
and 83% in the performance group
(P=0.27; 95% CI of absolute
difference -15.7% to 4.6%). Event-free survival in the reference
group was 78%, which was not different from the performance
group (P=0.31) but was
significantly lower than in the deferral group
(P=0.03). Adverse events are
listed in
Table 3
. The incidence of death was similar among the 3
groups. The incidence of myocardial infarction or
revascularization was similar in the deferral and
performance groups
(P=0.14) but was significantly
higher in the reference group
(P<0.001 compared with
deferral group and P<0.05
compared with performance group).
|
Angina and Medication Usage
The percentage of patients who were free from angina
increased significantly in all groups and persisted throughout the
study
(Figure 4
). The increase was similar for the deferral and
performance groups after 1 year but was higher for the
reference group (P<0.0001).
After 2 years, this percentage was higher in the deferral group than in
the performance group
(P=0.02) but was still highest
in the reference group
(P<0.001). Use of antianginal
and lipid-lowering drugs was similar in the 3 groups, both at baseline
and at the end of the study
(Table 4
).
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| Discussion |
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The incidence of angiographically visible coronary
artery disease increases with age and is
40% in a 60-year-old
population.13 However, the
prognosis in such a population is not primarily determined by the
angiographic presence and severity of the stenosis but by the
extent and severity of inducible
ischemia.14
Therefore, it is generally accepted that when objective evidence of
inducible ischemia is demonstrated and medical therapy fails,
coronary revascularization is
warranted.1 In contrast, if
noninvasive stress testing is either negative, inconclusive, or simply
not performed, it is unclear whether PTCA should be performed. In these
patients, who represent a considerable proportion of the
general PTCA population, the decision to perform PTCA is often based on
the coronary angiogram alone, and its benefit is
unproven.2 15
FFR, calculated from coronary pressure measurement,
is a reliable index of the functional severity of a coronary
stenosis, and a value of 0.75 discriminates stenoses
associated with inducible
ischemia.3 4 5 6
In the present study, FFR was used to divide patients within a
group in which physiological significance of the
stenosis was most likely (FFR <0.75) and within a group in
which that was not the case (FFR >0.75). Although average angiographic
severity was slightly greater in stenoses with FFR <0.75, the
overlap between both groups was so large that angiography could not be
used to predict the absence or presence of inducible ischemia
in individual patients
(Figure 2
).
In the present study, the event rate at 2 years was 11%
in the deferral group and 17% in the performance group (NS,
P=0.27). In those patients in
the deferral group with an event at follow-up, initial FFR values were
evenly distributed, which indicated that the cutoff value of 0.75 was
appropriate. After 2 years of follow-up, symptomatic
improvement was greater in the deferral group than in the
performance group
(P=0.02). This means that in
patients with FFR >0.75, no benefit of PTCA was present, either in
terms of adverse events or in functional class. The event rate was
highest (23%) in the reference group. Such an event rate is generally
reported after single-vessel PTCA and is accepted because it is
outweighed by the considerable symptomatic improvement, as
was clearly the case in the present study
(Figure 4
).16 17
In addition, the significantly larger improvement in anginal status in
the reference group also suggests that chest pain in these patients was
indeed due to the target stenosis. This provides post hoc
support to the decision to perform PTCA in those patients.
The present study also allowed comparison of patients
who undergo PTCA of a hemodynamically significant
stenosis (reference group) and of a nonsignificant
stenosis (performance group). It showed that event
rates were similar but that symptomatic improvement was
significantly more pronounced in case of significant stenosis
(Figure 4
.) It is unclear why Canadian
Cardiovascular Society class also improved in patients
with FFR >0.75, even without revascularization.
Similar observations have been made in other studies, and the
reassurance of both the patient and physician that was provided by an
additional method of excluding functional significance of the
stenosis may have played a
role.7 16 18 19
Similarly, it is not obvious why the number of patients with angina at
2 years of follow-up was higher in the performance group than
in the deferral group. One may wonder whether this was related to the
PTCA. In this respect, no difference in the use of antianginal or
lipid-lowering drugs was present between the deferral and
performance groups either at baseline or during 2 years of
follow-up
(Table 4
).
Some previous studies20 21 22 suggested that acute ischemic events occur predominantly at the site of previously insignificant or mild stenoses. This has been extrapolated into a belief that mild stenoses would have a worse prognosis than severe stenoses and that the use of PTCA in such mild lesions would be beneficial.23 However, our data show that PTCA of such lesions without functional significance did not improve outcome or anginal status and did not reduce the use of antianginal medication. These findings are in accordance with a recent study showing that deferral of PTCA on the basis of intravascular ultrasound analysis of stenosis resulted in a favorable outcome.24 In this context, it should be emphasized that in the present study, the event rate in patients in the deferral group was 11%, which was 3 to 4 times higher than in an age-matched population without heart disease. Therefore, it is evident that the presence of a functionally nonsignificant stenosis poses an increased risk. However, the issue addressed here is that such risk cannot be reduced by performing PTCA. In such patients, modification of risk factors and adequate medical treatment are probably of greater prognostic value than a mechanical coronary intervention.8 15
According to the American Heart Association/American College
of Cardiology
guidelines,1 PTCA should
preferably be performed after inducible ischemia has been
documented. Yet, the present study also indicates that in
50%
of patients without previously documented ischemia, FFR
identifies a significant stenosis that warrants subsequent
PTCA. The present multicenter study confirms that such measurement
of coronary pressure and FFR is feasible, safe, and
reproducible.
This study has several limitations. First, it does not provide any data as to the adverse cardiac event rate that would have occurred in the reference group (patients with FFR <0.75) when angioplasty would also have been deferred. Second, control angiography was not performed during follow-up except when clinically indicated. This strategy was chosen to prevent the sudden increase in re-PTCA at follow-up when systematic control angiograms are performed.25 Finally, in some patients enrolled in the present study, exercise-induced spasm superimposed on a functionally nonsignificant stenosis or microvascular disease cannot be ruled out.
In conclusion, in patients with a coronary stenosis who are referred for PTCA without objective evidence of ischemia, measurement of coronary pressure just before the planned intervention identifies patients with FFR >0.75 who do not benefit from PTCA and patients with FFR <0.75 in whom PTCA is an appropriate treatment and markedly improves functional class.
| Appendix 1 |
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Spain
C. Macaya, J. Cortés Lawrenz, University Hospital
San Carlos, Madrid.
South Korea
W. Ro Lee, G. Hyeon-cheol, Samsung Medical Center,
Seoul.
Belgium
V. Legrand, Center Hospitalier Universitaire
Sart-Tilman, Liège; Guy Heyndrickx, F. Staelens, A. Roets,
Cardiovascular Center Aalst.
Germany
C. Kühn, Center for Cardiology, Prof
Mathey, Schofer und Partner, Hamburg; D. Baumgart, M. Haude, S.
Vetter, Universitätsklinikum Essen.
Sweden
P. Albertsson, L. Grip, Sahlgrenska Hospital
Göteborg.
Japan
A. Hirayama, K. Kodama, Osaka Police
Hospital.
Received December 15, 2000; revision received March 27, 2001; accepted April 3, 2001.
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