From the Division of Cardiology, Department of Medicine, Rhode Island
Hospital, Brown University School of Medicine, Providence, RI.
Correspondence to David O. Williams, MD, Division of Cardiology, APC 434A, Rhode Island Hospital, 593 Eddy St, Providence, RI 02903. E-mail davidwilliams{at}brown.edu
Directional
coronary atherectomy (DCA) was originally developed as a
potential replacement for balloon angioplasty. The design of the
catheter used to perform DCA offered several unique advantages. First,
it was capable of removing obstructive atherosclerotic lesions. Thus
rather than rearranging plaque within an artery as occurs with balloon
angioplasty, the obstruction was relieved by reduction of the plaque
mass. Second, certain lesions with characteristics unfavorable for
balloon angioplasty appeared to be ideally suited for DCA. Since the
atherectomy catheter had a cutting window that could be positioned
rotationally as well as longitudinally within an artery, eccentric
plaque could be removed selectively. Similar benefits were anticipated
from lesions located at important coronary bifurcations, such
as those involving the left anterior descending coronary artery
and origin of the diagonal branch. Finally, tissue removed by DCA was
available for analysis to expand our knowledge about
coronary atherosclerosis. Samples of
coronary atheroma could be examined grossly and
microscopically1 and studied by
immunohistochemistry.2
Initially, the value of DCA was assessed by means of a large
registry that catalogued acute and late clinical
outcomes.3 When compared with a historical
control, the results of DCA appeared comparable to or better than those
achieved by balloon angioplasty. There was a sense that the incidence
of serious coronary dissection and abrupt occlusion after DCA
was less than that after balloon
angioplasty.4
DCA became the first of the "new" percutaneous,
catheter-based devices approved for the treatment of coronary
disease in the United States. Interestingly, unlike current "new
devices," approval did not require the performance of a
randomized, clinical trial. DCA was quickly and enthusiastically
embraced by the interventional community. During this early phase of
its use, DCA was performed without adjunctive balloon angioplasty; that
is, the DCA catheter was used alone and not in combination with any
other device.
Shortly after commercialization, two randomized, controlled clinical
trials comparing the effectiveness and safety of DCA with that of
balloon angioplasty were undertaken. One (CCAT) was limited to patients
with lesions located in the left anterior descending coronary
artery; the other (CAVEAT) included patients with lesions in any of the
native coronary arteries. Because of a desire to complete these
trials promptly, enrollment was performed at many clinical sites at a
time when DCA itself was relatively new and when the operators who
performed DCA were early in their learning curves.
The results of CAVEAT and CCAT were unexpected. In CAVEAT, DCA was
associated with a higher incidence of death and myocardial infarction
than balloon angioplasty.5 6 Alarmingly,
multivariable analysis identified "having DCA
performed" as an independent predictor of poor outcome. Furthermore,
the rates of restenosis were high in both treatment groups,
with only a small difference favoring DCA. CCAT, the trial limited to
patients with left anterior descending disease, demonstrated a better
initial angiographic outcome in the DCA group than in the angioplasty
group but no difference in clinical outcome at 6 months of
follow-up.7 A third trial evaluated the value of
DCA in patients with diseased aortocoronary venous bypass
grafts.8 DCA was associated with a higher
incidence of embolization of debris to the distal coronary
circulation than balloon angioplasty; 6-month restenosis rates
were similar. These trials caused interventional cardiologists to
question the value of DCA. Accordingly, usage shifted from routine to
discretionary, primarily for problematic lesions that were
known to respond poorly to balloon angioplasty.
A more devastating blow to DCA came with the release of the
intracoronary stent. Convincing data showed superiority of
stenting over balloon angioplasty in improving both angiographic and
clinical outcome.9 10 Stents made angioplasty
safer, predictably more successful, and decreased the incidence of
restenosis by about one third. Importantly, stents were
particularly well suited for proximal, complex lesions in large
coronary vessels, the very same lesions in which DCA seemed
most applicable. Although no head-to-head comparison has been
performed, one case-matched study demonstrated lower rates of
restenosis and need to perform repeat target lesion
revascularization in stent patients compared with
DCA patients.11
We are now presented with new information about DCA. In this
issue of Circulation, Baim and coinvestigators report the
results of the Balloon Versus Optimal Atherectomy Trial
(BOAT).12 This randomized, controlled clinical
trial again compares coronary angiographic and clinical
outcomes of patients treated by balloon angioplasty with those treated
with DCA. In BOAT, DCA was performed differently than in prior trials.
Operators attempted to achieve the largest possible
arterial lumen by using DCA more aggressively and
supplementing it with balloon angioplasty. Stenting in angioplasty
patients was restricted to those with suboptimal results.
BOAT showed the following. DCA achieved a larger initial lumen and a
higher procedural success rate than balloon angioplasty, without an
increased risk of death, Q-wave myocardial infarction, and need for
coronary artery bypass surgery. Furthermore, DCA resulted in a
lower rate of restenosis than did balloon angioplasty. On the
other hand, coronary perforation, although infrequent, was
observed only in DCA patients, and 34% of DCA patients experienced
detectable elevations in serum levels of CK-MB. Despite less
angiographic restenosis among DCA patients, DCA did not reduce
the chance of needing repeat revascularization.
The results of the "optimal" DCA performed in BOAT are different
from DCA performed in CAVEAT. Adjunctive balloon angioplasty was used
in 81% of BOAT patients assigned to DCA versus none in CAVEAT.
Acutely, the coronary lumen after DCA in BOAT was larger than
that in CAVEAT, and both the restenosis rate and the need for
repeat revascularization were lower in BOAT. Of
note, the results of balloon angioplasty in BOAT were also better than
balloon angioplasty in CAVEAT, reflecting overall improvements in
interventional technique and practice. Perhaps most importantly, BOAT
seemed to exonerate DCA from being a "toxic" procedure, as the
mortality rate of DCA patients was not higher than angioplasty
patients.
With the acceptance of this new information, what is the role
for DCA at this point? A balanced review warrants reexamining the
results of BOAT. DCA and balloon-treated patients had equal rates of
death, Q-wave myocardial infarction, and need for repeat
revascularization over the course of 1 year. In
terms of these major clinical events, there was no superiority of one
procedure over the other. DCA patients had a small but real chance for
coronary perforation, and one third experienced an increase in
CK-MB levels. In acknowledgment of the controversy about the
significance of asymptomatic increase in CK-MB
levels,13 if all else is equal and balloon
angioplasty is technically easier than DCA, then there is little reason
to select DCA over balloon angioplasty.
BOAT (and DCA) still needs to deal with the issue that contemporary
interventional cardiology means aggressive use of
stents. As the technique of stenting continues to be refined, clinical
results look better and better. Serious bleeding after stenting is now
uncommon, since aggressive anticoagulation has been replaced by
antiplatelet therapy.14 Certainly
subacute thrombosis remains a concern, but this event is now
infrequent. Currently, the scope of stenting extends to a broad range
of coronary disease settings,15 16 and
rates of restenosis and repeat
revascularization are reported in the single-digit
range.17 Adjunctive local radiation promises to
further enhance the durability of stenting
alone.18
The challenge of DCA is not to be better than balloon angioplasty but
to be better than angioplasty plus stenting. In the absence of hard
data showing either superiority over stenting or the value of combining
DCA with stenting, DCA will not be an everyday interventional
procedure. DCA will probably remain alive in some laboratories as a
"niche" technique. When DCA is used, attention should be paid to
incorporating "optimal" techniques to enhance the opportunity for a
favorable outcome. Concern exists, however, about the ability of
operators to maintain a high skill level for procedures that are
performed infrequently.
One final but very significant concern emerges as a consequence of
BOAT. When in the course of its development should a new, unique
treatment be compared with a conventional treatment by means of a
randomized controlled clinical trial? It is fair to say that CCAT and
CAVEAT evaluated DCA too early. The technique for performing DCA was
less than optimal, and DCA suffered as a result. Rather than leaping to
an early randomized trial, perhaps a stepwise series of sequential
observational studies should be considered as an initial approach. In
this fashion, the safety and effectiveness of a new device could be
characterized by a process analogous to dose-ranging trials of
pharmaceuticals. Gentle probing of the envelope will be necessary to
determine the limits of response and toxicity. We would prefer to get
the correct answer on the first pass rather than having to be told
"but wait, there's more."
Acknowledgments
The authors acknowledge the secretarial assistance of Arlene S.
Grant and the critical review of the manuscript by Barry L.
Sharaf, MD.
Footnotes
The opinions expressed in this editorial are not necessarily those of the editors or of the American Heart Association.
References
© 1998 American Heart Association, Inc.
Editorial
Directional Coronary Atherectomy
But Wait, There's More
Key Words: Editorials • atherosclerosis • surgery • trials
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