Ancillary techniques in interventional cardiology

21 Pages·2006·0.24 MB·English

Chapter 7
Ancillary techniques in interventional
cardiology
John M. Lasala, George Chrysant, Adrian Messerli
Introduction
The Ancillary Techniques in Interventional Cardiology Section will be diverse in covering a num-
ber of cutting balloon devices such as directional coronary atherectomy, rotational atherectomy,
and distal embolic protection. Limitations on space prevent an elaborate discussion on other
techniques that would qualify for the chapter. These three were chosen because they span over
a decade and a half of interventional cardiology. Some are more historical in nature; all have had
a substantial impact at one time during the development of interventional cardiology techniques.
The rotational atherectomy system was developed by Dr David C Auth PhD, two decades ago.
It consists of a nickel-plated brass elliptical burr coated on the leading edge with 20–30 micron
diamond chips. The chips protrude from the nickel plating forming a cutting surface of approxi-
mately 5 microns, therefore ablating atherosclerotic plaque to the size of a red blood cell. The
ablated material can then pass through the microcirculation and is consumed by the reticular
endothelial system. The burr is attached to a long flexible drive shaft with a central core clearance
of 0.009 inch stainless steel guidewire. The drive shaft is driven by compressed nitrogen and
housed in a Teflon sheath that can be irrigated with a flush solution containing a cocktail of heparin,
nitroglycerin or calcium channel blockers at the discretion of the operator. A fiber optic light probe
helps rotate the shaft at 140–180,000 rpm. A higher speed may be necessary when encountering
heavily calcified lesions. Reduction of friction of the drive shaft with the Teflon-coated sheath has
recently been improved by the addition of Rotaglide TM solution consisting of a phospholipid
emulsion constituting nature’s“10W40”. It minimizes heat and improves the efficiency of the drive
shaft. Rotational atherectomy is a very operator dependent technique. Though comprising less
than 10% of all procedures in the United States, it enables the operator to perform cases that
involve heavy degrees of calcification to be performed where other technologies fail. The rotabla-
tor is capable of cutting into elastic plaque whether or not it is calcified, by applying the principle
of differential cutting. The normal artery being more elastic in nature, will deflect from the burr itself,
similar to shaving one’s face in the morning – the beard reflected off the skin is preferentially cut.
Rotational atherectomy is successful only with diligent attention to technique and detail.
The field has been advanced by a number of high volume practitioners who have previously
published on optimal techniques, such as Maurice Buchbinder at La Jolla California; Mark
Reisman at Swedish Hospital, Seattle Washington; Samin Sharma, Mount Sinai Medical Center
in New York City; Gregory Braden, Winston Salem, North Carolina; and Ted Feldman at Abbott
Northwestern Hospital Chicago, Illinois.
Directional coronary atherectomy (DCA) was intended to improve the safety and efficacy of
revascularization compared to balloon angioplasty by controlling plaque removal. The device
was conceived and initially tested by Dr John B Simpson, MD at Sequoia Hospital in Redwood
City, California. The debulking strategy was developed in response to the major problems of
balloon angioplasty during the early 1980s and was designed to decrease the primary failure
and abrupt closure rates while minimizing restenosis.
The entire concept of atherectomy was introduced by Dr Simpson who developed the pro-
totype known as the Simpson Coronary AtheroCath. This consists of a metal housing with a
fixed balloon, a nose cone collection chamber and a hollow tube which accompanies a 0.014 inch
Ancillary techniques in interventional cardiology
guidewire. A cup-shaped cutter inside the housing is attached to a flexible drive shaft and is
activated by a hand-held battery operated motor driver unit. The AtheroCath is advanced into
the lesion with the cutting chamber directed into the plaque bulk. The blade is then withdrawn
exposing the plaque to the chamber and cutting surface. When the balloon is inflated it will fur-
ther push the cuttingwindow into the plaque. The cutter is manually advanced while rotating the
cutter at approximately 2000rpm. The excised atheroma is then pushed forward and stored in
the distal nose cone, allowing for collection.
The development of directional coronary atherectomy and its practitioners, particularly
Drs Donald Baim and Richard Kuntz of Harvard, devised effective debulking strategies in an
optimal manner, proposing the “bigger is better hypothesis”. This hypothesis stated that
although there is an obligatory late loss of lumen diameter that occurs after coronary interven-
tion, a larger lumen would have a higher probability of avoiding restenosis and producing fewer
symptoms. Directional arthrectomy with its controlled debulking was developed as a means of
capitalizing on this hypothesis. Other operators, notably Chuck Simonton working at Charlotte,
North Carolina, have demonstrated that ultrasound guidance of debulking can further perfect
outcomes. In fact, directional coronary atherectomy, in common with stenting, is the only device
tested in a prospective randomized manner, to demonstrate a reduction in angiographic rates
of restenosis. Recovery of atheroma, unlike its destructive counter part, rotational atherectomy,
also was helpful to vascular biologists, providing a biopsy specimen that could be evaluated for
procoagulate activity, neointimal formation, and differences in the plaque composition in
patients with stable and unstable angina. Today, the device has largely been superseded by
intracoronary stenting which is considerably simpler and less operator dependent. It has found
use in bulky areas such as bifurcation lesions in the coronary tree while an updated version of
directional coronary artherectomy (Fox Hollow) has been employed in peripheral arteries to
debulk large lesions in the lower extremity.
Embolic protection devices round out the trio of ancillary technologies. This is the most
recently developed and currently, the most commonly used in contemporary intervention. This
is a rapidly burgeoning field with many major medical device companies currently pursuing FDA
approval with an embolic protection device. The landmark papers regarding the SAFER Trial
established embolic protection as the method of choice in reducing MB/CPK release related to
saphenous vein graft intervention. Application into both the coronary tree, carotids and renal
intervention will be helpful to protect against end-organ damage. The number of articles being
reviewed and published in this field will fill a rather large book chapter over the next three years.
The development of these techniques stand as testament to the ingenuity of the engineers,
private industries and interventional cardiologists who have helped make these devices a real-
ity. Necessity truly being the mother of invention has been the guiding force to the design and
construction of ancillary techniques involved in interventional cardiology. All have given us
important additions to our armamentarium in caring for our patients with coronary disease.
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Title 1
A comparison of directional atherectomy with coronary
angioplasty in patients with coronary artery disease
(The CAVEAT Study Group)
Author
Topol EJ, Leya P, Pinkerton CA, et al.
Reference
N Engl J Med 1993;329: 221–227
Abstract
BACKGROUND: Directional coronary atherectomy is a new technique of coronary revasculariza-
tion by which atherosclerotic plaque is excised and retrieved from target lesions. With respect to
the rate of restenosis and clinical outcomes, it is not known how this procedure compares with
balloon angioplasty, which relies on dilation of the plaque and vessel wall. We compared the rate
of restenosis after angioplasty with that after atherectomy. METHODS: At 35 sites in the United
States and Europe, 1012 patients were randomly assigned to either atherectomy (512 patients)
or balloon angioplasty (500 patients). The patients underwent coronary angiography at base line
and again after six months; the paired angiograms were quantitatively assessed at one labora-
tory by investigators unaware of the treatment assignments. RESULTS: Stenosis was reduced to
50% or less more often with atherectomy than with angioplasty (89% vs. 80%, p(cid:6)0.001), and
there was a greater immediate increase in vessel caliber (1.05 vs. 0.86mm, p(cid:6)0.001). This
was accompanied by a higher rate of early complications (11% vs. 5%, p(cid:6)0.001) and higher
in-hospital costs ($11,904 vs. $10,637; p(cid:1)0.006). At six months, the rate of restenosis was
50% for atherectomy and 57% for angioplasty (p(cid:1)0.06). However, the probability of death or
myocardial infarction within six months was higher in the atherectomy group (8.6% vs. 4.6%,
p(cid:1)0.007). CONCLUSIONS: Removing coronary artery plaque with atherectomy led to a larger
luminal diameter and a small reduction in angiographic restenosis, though the latter was not
statistically significant. However, atherectomy led to a higher rate of early complications,
increased cost, and no apparent clinical benefit after six months of follow-up.
Summary
The CAVEAT study was a randomized study that assigned 512 patients to directional coronary
atherectomy (DCA) and 500 patients to percutaneous transluminal angioplasty (PTCA). Patients
were enrolled at 35 sites in the USA and Europe, and underwent baseline and 6 month angio-
graphy to examine whether there was a difference in restenosis rates between the two modal-
ities. The primary end-point of the study was angiographical restenosis ((cid:7)50%). A composite
early clinical end point of death, MI, emergency coronary bypass surgery, and acute vessel
closure were determined. Both DCA and PTCA had 96% angiographical success rates accord-
ing to the site physicians; however, there was a slightly better reported success rate for DCA
when evaluated by the core laboratory (89% vs. 80%, p(cid:7)0.001). In terms of the clinical end-
points, there was no statistically significant difference in outcome (Table 1).
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Ancillary techniques in interventional cardiology
Table 1 Cumulative clinical outcomes (values in number (%)) at 6 months (from Topol et al.
N Engl J Med1993;329: 221–227)
Outcome Atherectomy (n(cid:1)512) Angioplasty (n(cid:1)500) p-value
Death 8 (1.6) 3 (0.6) 0.22
Myocardial infarction 39 (7.6) 22 (4.4) 0.04
Coronary artery bypass surgery 42 (8.2) 34 (6.8) 0.39
Need for subsequent non-surgical 145 (28.3) 152 (30.4) 0.42
coronary intervention
No adverse clinical end point 307 (60) 307 (63) 0.49
For the cumulative outcomes, patients may be included in more than one category. In addition, the
6-month composite clinical end point was prospectively defined as death, the worst outcome, followed in
order of rank by myocardial infarction, coronary artery bypass surgery, and the need for subsequent
coronary intervention. Patients were classified in the category that corresponded to the worst outcome they
had experienced. By ordinal logistic regression, there was no significant difference between the two groups
in the composite clinical end point (p(cid:1)0.19).
Strengths
This study was a large randomized study evaluating both angiographical success and clinical
outcomes in patients undergoing two different accepted methods of treating obstructive coronary
disease. The groups were equal in representation and both groups were treated with the same
basic pharmacological agents before and after their procedures including aspirin and a calcium
channel blocker prior to the baseline procedure with intracoronary nitroglycerin prior to the
baseline angiogram, and at 6-month follow-up angiogram.
Weaknesses
While the sites were chosen on the basis of their experience with DCA, the overall experience with
this new device (at the time) was relatively small compared to the operator’s cumulative skill with
PTCA. Each operator had to have experienced an 80% or higher success rate with a minimum
of 400 PTCAs compared to an 85% success rate with a minimum of 50 DCAs. Also, 26% of the
patients in the DCA arm crossed over to other technologies for revascularization, namely stents,
perfusion balloons, or other atherectomy devices compared with 14% in the PTCA arm.
Relevance
DCA was heralded as a potential replacement for PTCA due to the ability of DCA to excise and
remove plaque and plaque debris compared to treating the plaque with balloon expansion and
fracture. The trial was done on the heels of successful registry data and during a time when many
operators were early on what is now known to be a steep learning curve. The operators in the
trial were vastly more experienced with PTCA compared to DCA possibly hurting the outcome
of the trial. As stenting became more widespread and was proven to drastically reduce resteno-
sis rates, DCA faced a new challenge, which was not only to outperform PTCA, but also to out-
perform PTCA and stenting. Now with drug-eluting stent technology reducing the restenosis
rates into the single digits, it is clear that DCA does not compare favourably and its use is
restricted to a small number of centres.
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Title 2
“Optimal” directional coronary atherectomy, final results of
the Optimal Atherectomy Restenosis Study (OARS)
Author
Simonton CA, Leon MB, Baim DS, et al.
Reference
Circulation1998;97: 332–339
Abstract
BACKGROUND: Previous clinical trials of directional coronary atherectomy (DCA) have failed to
show significant improvement in early or late outcomes compared with balloon angioplasty
(PTCA). The present study tested the hypothesis that more aggressive “optimal” atherectomy
could be performed safely to produce larger initial lumen diameters and a lower late restenosis
rate. METHODS AND RESULTS: The present study was a prospective multicenter registry of
consecutive patients undergoing optimal DCA of de novoor restenotic lesions in 3.0- to 4.5-mm
native coronary arteries. Optimal DCA was defined as using a 7F atherectomy device and
adjunctive PTCA if necessary to achieve a(cid:6)15% residual stenosis. Six-month angiographic
and 1-year clinical follow-up was planned in all patients. A total of 199 patients with 213 lesions
met eligibility criteria for enrollment. Short-term procedural success was achieved in 97.5%, with
a major complication rate (death, emergency bypass surgery, or Q-wave myocardial infarction
[MI]) of 2.5%. There were no early deaths. Non-Q-wave MI (CK-MB(cid:7)3 times normal) occurred
in 14% of patients. Mean reference vessel diameter was 3.28mm. Mean diameter stenosis was
reduced from 63.5% to a final stenosis of 7%. Late 1-year clinical follow-up revealed one car-
diac death and a target lesion revascularization rate of 17.8%. The angiographic restenosis rate
at 6 months was 28.9%, with the major predictor of restenosis being a smaller postprocedure
lumen diameter. CONCLUSIONS: Optimal DCA produced a low residual % diameter stenosis
and a lower restenosis rate than seen in previous trials without an increase in early or late major
adverse events.
Summary
The OARS (Optimal Atherectomy Restenosis Study) trial followed two large randomized trials
(Coronary Angioplasty vs. Excisional Atherectomy Trial and Canadian Coronary Atherectomy
[CAVEAT and CCAT]) that examined the efficacy of directional coronary atherectomy (DCA) as a
method of treating obstructive atherosclerotic coronary disease versus standard balloon angio-
plasty. Both trials failed to show a significant benefit to using DCA. Moreover, there was a belief
that these trials were conducted too early in the development of the DCA technique, which is to
say that the operator’s experience was early on the learning curve. Another thought was that
“optimal” atherectomy had not been performed. The OARS trial tested the “bigger is better”
approach to atherectomy. The hypothesis was that more aggressive DCA would lead to a larger
early lumen diameter; and subsequently, better late clinical and angiographical restenosis rates.
The study involved 200 consecutive patients at four centres who underwent more aggressive
atherectomy and who were followed at 6 months (angiography) and 12 months (clinical). The
primary end-points were 6-month angiographical restenosis ((cid:7)50%) and 12 month target
vessel failure rate (myocardial infarction (MI), target vessel revascularization (TVR), or death).
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Ancillary techniques in interventional cardiology
(a) 100
90
80
70
60
%)
ns ( 50 DCA(cid:2)PTCA Ref
o
esi DCA(cid:2)PTCA Pre
L 40
DCA(cid:2)PTCA Post
30
DCA Only Ref
20
DCA Only Pre
10 DCA Only Post
0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
MLD (mm)
(b) 100
90
80
70
60
%)
ns ( 50
o
si
e
L 40
30 DCA(cid:2)PTCA Pre
DCA(cid:2)PTCA Post
20
DCA Only Pre
10
DCA Only Post
0
(cid:4)40 (cid:4)30 (cid:4)20 (cid:4)10 0 10 20 30 40 50 60 70 80 90 100
Diameter stenosis (%)
Figure 1 Baseline and acute angiographic results. (a) Cumulative distribution of reference vessel diameter
and minimal luminal diameter (MLD) at baseline (preprocedure) and after final treatment (postprocedure).
(b) Cumulative distribution of % diameter stenosis at baseline (preprocedure) and after final treatment
(postprocedure).
The results for angiographical restenosis, death, MI, TVR and target vessel failure were 29%,
1%, 1.5%, 21% and 24%, respectively. A large initial lumen diameter was achieved with an
average size of 3.16mm (in vessels with reference diameters of 3.0–4.5mm). The authors con-
cluded that “optimal” DCA could be performed safely and would result in larger initial lumen
diameters (Figure 1).
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Citation Count 66
Strengths
The trial was conducted at experienced centres capable of performing more aggressive DCA.
The follow-up included angiographical and clinical end points.
Weaknesses
The trial was not randomized and 87% of patients underwent post-DCA percutaneous translu-
minal coronary angioplasty (PTCA); therefore, in most cases the result was not 100% attribut-
able to DCA. There was a high incidence of periprocedural CK-MB elevation although this did
not manifest in poorer clinical outcomes.
Relevance
The overall benefit of DCA shown in this study is modest at best. Using a more aggressive DCA
strategy did lead to a larger early lumen; however, this was at a cost of higher CK-MB levels and
without a large clinical benefit. The OARS trial did collect early registry results of safety and effi-
cacy, but did not improve greatly on the shortcomings of CAVEAT and CCAT, which were larger
studies. Compared to PTCA, the restenosis rate of 29% achieved in this study compares
favourably; however, it falls short of newer era bare metal stents and is clearly inferior to drug-
eluting stents in terms of angiographical restenosis rates.
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Ancillary techniques in interventional cardiology
Title 3
Final results of the balloon vs. optimal atherectomy trial
(BOAT)
Author
Baim DS, Cutlip DE, Sharma SK, et al.
Reference
Circulation1998;97: 322–331
Abstract
BACKGROUND: Previous directional coronary atherectomy (DCA) trials have shown no signifi-
cant reduction in angiographic restenosis, more in-hospital complications, and higher 1-year
mortality than conventional balloon angioplasty (percutaneous transluminal coronary angio-
plasty [PTCA]). DCA, however, has subsequently evolved toward a more “optimal” technique
(larger devices, more extensive tissue removal, and routine postdilation to obtain diameter
stenosis(cid:6)20%). METHODS AND RESULTS: The Balloon vs. Optimal Atherectomy Trial (BOAT)
was conducted to evaluate whether optimal DCA provides short- and long-term benefits com-
pared with balloon angioplasty. One thousand patients with single de novo, native vessel lesions
were randomized to either DCA or PTCA at 37 participating centers. Lesion success was
obtained in 99% versus 97% (p(cid:1)0.02) of patients to a final residual diameter stenosis of 15%
versus 28% (p(cid:6)0.001)for DCA and PTCA, respectively, the latter including stents in 9.3% of
the patients. There was no increase in major complications (death, Q-wave myocardial infarction,
or emergent coronary artery bypass graft surgery [2.8% versus 3.3%]), although creatine kinase –
MB(cid:7)3(cid:3)normal was more common with DCA (16% versus 6%; p(cid:6)0.001). Angiographic
restudy (in 79.6% of eligible patients at 7.2(cid:5)2.6 [median, 6.9] months) showed a significant
reduction in the prespecified primary end point of angiographic restenosis by DCA (31.4% ver-
sus 39.8%; p(cid:1)0.016). Clinical follow-up to 1 year showed nonsignificant 13 to 17% reduc-
tions in the DCA arm of the study for mortality rate (0.6% versus 1.6%; p(cid:1)0.14), target vessel
revascularization (17.1% versus 19.7%; p(cid:1)0.33), targetsite revascularization (15.3% versus
18.3%;p(cid:1)0.23),and targetvessel failure (death, Q-wave myocardial infarction, or target vessel
revascularization, 21.1% versus 24.8%; p(cid:1)0.17). CONCLUSIONS: Optimal DCA provides sig-
nificantly higher short-term success, lower residual stenosis, and lower angiographic restenosis
than conventional PTCA, despite failing to reach statistical significance for reducing late clinical
events compared with PTCA with stent backup.
Summary
BOAT (Balloon vs. Optimal Atherectomy Trial) was a randomized, comparative clinical study
assessing late angiographic and clinical outcomes after directional atherectomy (DCA) vs. per-
cutaneous transluminal coronary angioplasty (PTCA) in 986 patients with focal stenoses in
native coronary arteries. BOAT demonstrated that acute lumen results and late angiographical
restenosis could be significantly improved by DCA, without a concomitant increase in procedural
complications or late cardiac events. Also, DCA resulted in lower rates of restenosis than PTCA.
Mortality and Q-wave MI rates were equivalent. The authors hypothesized that DCA had per-
formed poorly in prior trials because inexperienced operators had utilized less than “optimal”
technique. In BOAT, larger 7 French devices were used in 95% of procedures and balloon post-
dilation was performed in 81% of the 486 lesions.
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Citation Count 115
Related References
1. Adelman AG, Cohen EA, Kimball BP, et al. A comparison of directional atherectomy with balloon
angioplasty for lesions of the left anterior descending artery. N Engl J Med 1993;329: 228–233.
2. Bersin RM, Simonton CA. Rotational and directional coronary atherectomy. Catheter
Cardiovasc Interv 2003;58: 485–499.
3. Holmes DR, Topol EJ, Adelman AG, Cohen EA, Califf RM. Randomized trials of directional
coronary atherectomy: implications for clinical practice and future investigation. J Am Coll
Cardiol1994;24: 431–439.
4. Topol EJ, Leya F, Pinkerton CA, et al. A comparison of directional atherectomy with coronary
angioplasty in patients with coronary artery disease. N Engl J Med 1993;329: 221–227.
Strengths
A clear strength of this trial in contrast to prior direct coronary atherectomy (DCA) trials was the
operators’ intention to employ an aggressive “optimal” technique. As a result, the average
coronary lumen was larger in BOAT than in CAVEAT.
Weaknesses
The authors acknowledge that a conceivable limitation of the study was that atherectomy
results might still be suboptimal. Intravascular ultrasound was not utilized routinely; had it been,
even more effective plaque debulking could theoretically have been achieved. Another impor-
tant caveat is that BOAT did not address the value of combining DCA with stenting. Larger
lumen gains and lower rates of restenosis can be obtained by deployment of stents alone, and
obviate the need for DCA.
Key message
Although“optimal” DCA resulted in improved angiographical outcomes with lower rates of resteno-
sis,TVR at 1 year was not statistically different. Also, the rate of peri procedural non-Q-wave MI
(defined in BOAT as CK-MB elevation(cid:7)3 times normal) was more than twice as frequent for
DCA vs. for PTCA (16% and 6% respectively, p(cid:6)0.001).Finally, as mentioned above, the role
of provisional DCA in an era of nearly routine stent deployment has not been defined. This issue
was to be addressed in a prospective randomized trial, the Atherectomy before Multilink
Improves lumen Gain and clinical Outcomes (AMIGO) trial, in which excisional atherectomy
combined with stenting will be tested against stenting alone. This trial did not show an overall
benefit to debulking prior to stenting except in a few subsets such as bifurcation disease.
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Title 4
Saphenous vein graft angioplasty free of emboli randomized
(SAFER) Trial Investigators: randomized trial of a distal
embolic protection device during percutaneous intervention
of saphenous vein aorto-coronary bypass grafts
Author
Baim DS, Wahr D, George B, et al.
Reference
Circulation2002;105: 1285–1290
Abstract
BACKGROUND: Stents provide effective treatment for stenotic saphenous vein bypass grafts,
but their placement carries a 20% incidence of procedure-related complications, potentially
related to the distal embolization of atherosclerotic debris. We report the first multicenter ran-
domized trial to evaluate use of a distal embolic protection device during stenting of such lesions.
METHODS AND RESULTS:Of 801 eligible patients, 406 were randomly assigned to stent place-
ment over the shaft of the distal protection device, and 395 were assigned to stent placement
over a conventional 0.014-inch angioplasty guidewire (control group). The primary end point–a
composite of death, myocardial infarction, emergency bypass, or target lesion revascularization
by 30 days–was observed in 65 patients (16.5%) assigned to the control group and 39 patients
(9.6%) assigned to the embolic protection device (p(cid:1)0.004). This 42% relative reduction in
major adverse cardiac events was driven by myocardial infarction (8.6% versus 14.7%,
p(cid:1)0.008) and “no-reflow” phenomenon (3% versus 9%, p(cid:1)0.02). Clinical benefit was seen
even when platelet glycoprotein IIb/IIIa receptor blockers were administered (61% of patients),
with composite end points occurring in 10.7% of protection device patients versus 19.4% of
control patients (p(cid:1)0.008). CONCLUSIONS:Use of this distal protection device during stenting
of stenotic venous grafts was associated with a highly significant reduction in major adverse
events compared with stenting over a conventional angioplasty guidewire. This demonstrates the
importance of distal embolization in causing major adverse cardiac events and the value of
embolic protection devices in preventing such complications.
Summary
This randomized, multicentre study supports the efficacy of the Medtronic PercuSurge
GuardWire for retrieval of plaque debris and prevention of atheromatous embolization in degen-
erated saphenous vein grafts (SVG). Use of the device during stenting of stenotic venous grafts
was associated with significantly fewer major adverse cardiac events (MACE), including death,
MI, emergency bypass, or target lesion revascularization at 30 days. Importantly, the Saphenous
vein graft angioplasty free of emboli randomized (SAFER) cohort was in fact representative of
the typical SVG population; their mean age was 68, about 35% had diabetes; 75% had class III
or IV angina, and 40% had rest angina. Target lesion length averaged 16mm and about 39% of
lesions had angiographically noteworthy thrombus.
Citation Count 110
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