Clinical, electrocardiographic, and procedural characteristics of patients with coronary chronic total occlusions.

Abstract

Percutaneous coronary intervention for chronic total occlusion lesions is technically difficult despite equipment advances. Changes in electrocardiographic patterns, such as Q and T waves, during chronic total occlusion can provide information about procedural success and myocardial viability. In this study, we investigated clinical, electrocardiographic, and procedural characteristics of chronic total occlusions.
Patients (2,635) who underwent coronary angiography between January 2006 and July 2007 at six Catholic University Hospitals were identified using a dedicated Internet database.
A total of 195 patients had total occlusion lesions (7.4%). Percutaneous coronary interventions were attempted in 136 total occlusion lesions (66.0%) in 134 patients. Successful recanalization with stent implantation was accomplished in 89 lesions, with a procedural success rate of 66.4%. One procedure-related death occurred because of no-reflow phenomenon. After excluding 8 patients with bundle branch block, Q and T wave inversions were observed in 60 (32.1%) and 78 patients (41.7%), respectively. The presence of Q waves was associated with severe angina, decreased left ventricular ejection fraction, regional wall motion abnormality, and T wave inversion, but was not related to procedural success.
Percutaneous coronary intervention is a safe and useful procedure for the revascularization of coronary chronic total occlusion lesions. The procedural success rate was not related to the presence of pathologic Q waves, which were associated with severe angina and decreased left ventricular function.

Full text

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111
ORIGINAL ARTICLE
DOI 10.4070 / kcj.2009.39.3.111
Print ISSN 1738-5520 / On-line ISSN 1738-5555
Copyright ⓒ 2009 The Korean Society of Cardiology

Clinical, Electrocardiographic, and Procedural Characteristics
of Patients With Coronary Chronic Total Occlusions

Chan Seok Park MD, Hee-Yeol Kim, MD, Hun-Jun Park, MD, Sang-Hyun Ihm, MD, Dong-Bin Kim, MD,
Jong-Min Lee, MD, Pum-Jun Kim, MD, Chul-Soo Park, MD, Keon-Woong Moon, MD, Ki-Dong Yoo, MD,
Doo-Soo Jeon, MD, Wook-Seong Chung, MD, Ki Bae Seung, MD and Jae-Hyung Kim, MD
Department of Cardiology, College of Medicine, The Catholic University of Korea, Seoul, Korea

ABSTRACT
Background and Objectives: Percutaneous coronary intervention for chronic total occlusion lesions is technically
difficult despite equipment advances. Changes in electrocardiographic patterns, such as Q and T waves, during
chronic total occlusion can provide information about procedural success and myocardial viability. In this study, we
investigated clinical, electrocardiographic, and procedural characteristics of chronic total occlusions. Subjects and
Methods: Patients (2,635) who underwent coronary angiography between January 2006 and July 2007 at six Ca-
tholic University Hospitals were identified using a dedicated Internet database. Results: A total of 195 patients had
total occlusion lesions (7.4%). Percutaneous coronary interventions were attempted in 136 total occlusion lesions
(66.0%) in 134 patients. Successful recanalization with stent implantation was accomplished in 89 lesions, with a
procedural success rate of 66.4%. One procedure-related death occurred because of no-reflow phenomenon. After
excluding 8 patients with bundle branch block, Q and T wave inversions were observed in 60 (32.1%) and 78 patients
(41.7%), respectively. The presence of Q waves was associated with severe angina, decreased left ventricular ejection
fraction, regional wall motion abnormality, and T wave inversion, but was not related to procedural success. Con-
clusion: Percutaneous coronary intervention is a safe and useful procedure for the revascularization of coronary
chronic total occlusion lesions. The procedural success rate was not related to the presence of pathologic Q waves,
which were associated with severe angina and decreased left ventricular function. (Korean Circ J 2009;39:111-115)

KEY WORDS: : Coronary occlusion; Angioplasty; Electrocardiogram.


Introduction

Percutaneous coronary intervention (PCI) of chronic
total occlusion (CTO) lesions has a low success rate and
is technically difficult regardless of operator experience
and despite advances in equipment. CTO treatment re-
mains a major challenge and is a frequent reason for pa-
tient referral for coronary artery bypass surgery (CABG),
leading some to refer to the treatment as the “last fron-
tier” of PCI.1)2) However, CTOs account for 10% of all
PCI,3) with the majority of patients treated with either
CABG or medical therapy. The choice of therapy de-
pends on center policies and operator experience. Se-
veral studies performed during the bare metal stent
(BMS) era showed high rates of restenosis (32-55%) and
re-occlusion (8-12%).4)5) Drug-eluting stents are safe
and effective in this challenging lesion subset because
they markedly reduce the incidence of restenosis and
the need for target lesion revascularization.6-9) Several
retrospective observational studies have reported the
clinical impact of successful percutaneous CTO revas-
cularization on long-term survival.10) Other studies have
demonstrated statistically significant improvements in
left ventricular function and regional wall motion with
successful CTO recanalization.11-13)
Electrocardiogram (ECG) is performed for almost all
patients who undergo cardiologic evaluation. In old Q
wave myocardial infarctions, persistent negative T wave
inversion in infarction-related leads (IRL) is associated
with transmural infarction with a thin fibrotic layer,14-16)
and normalization of the T wave can identify viable myo-
cardium.17) The absence of a Q wave, which confers the
Received: September 16, 2008
Revision Received: December 10, 2008
Accepted: January 5, 2009
Correspondence: Hee-Yeol Kim, MD, Department of Cardiology, College
of Medicine, The Catholic University of Korea, 2 Sosa-dong, Wonmi-gu,
Bucheon 420-717, Korea
Tel: 82-32-340-2018, Fax: 82-32-340-2669
E-mail: cumckhy@catholic.ac.kr

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112·Electrical and ECG Characteristics of CTOs

non-existence of a previous myocardial infarction, is a
predictor of improved left ventricular systolic function
after successful recanalization of the CTO.18)
Here, we analyzed the clinical and angiographic cha-
racteristics and trends in revascularization and the treat-
ment of CTOs at the six hospitals in the Catholic Med-
ical Center, Korea, between January, 2006, and July,
2007. We also analyzed Q and T wave patterns, which
predict myocardial viability, in CTO patients.

Subjects and Methods

Demographic and procedural data for all patients
undergoing coronary angiography at Catholic Medical
Center were prospectively entered into a dedicated in-
ternet database. All data, including age, gender, medical
history, coronary angiographic results, ejection fraction,
and treatment recommendations, were prospectively
collected at the time of cardiac catheterization. All ch-
ronically occluded vessels observed between January 2006,
and July 2007, were retrospectively identified. Patients
with previous bypass surgery or recent (<3 months)
myocardial infarction were excluded.
Significant coronary disease was defined as ≥1 lesion
of ≥70% luminal diameter stenosis. Total coronary
artery occlusion was defined as 100% luminal diameter
stenosis without a discernable lumen and the absence
of anterograde flow. CTO was defined as total coronary
artery occlusion of ≥1 month in duration. Multivessel
disease was defined as ≥70% stenosis in ≥2 vessels.
Before the procedure, all patients were treated with
a loading dose of ≥300 mg clopidogrel and 100 mg
aspirin. At the start of the procedure, patients received
a single bolus of unfractionated heparin (80-120 U/kg
body weight). Procedures were performed using a stand-
ard femoral approach. In more than 90% of cases, guide-
wires with microcatheter support were used to cross the
lesion, but newer techniques were also attempted, such
as intravascular ultrasound (IVUS)-guided manipulation
of the guidewire. Procedural success was defined as re-
duction of residual lumen diameter stenosis to <50%
and successful stent employment in the CTO segment
without a major adverse cardiac event (MACE). MACE
consisted of in-hospital death, myocardial infarction,
urgent or emergent CABG, or a cerebrovascular event.
An ECG was performed at the time of admission for
coronary intervention. The presence of a Q wave ≥30
msec in leads III and aVF was regarded as the Q wave
area in right coronary artery occlusion, while the pre-
sence of a Q wave ≥30 msec or R waves ≤20 mV in
leads V3 and V4 was defined as the Q wave area in left
anterior descending artery occlusion. Q waves longer
than 30 msec in two or more leads of V5, V6, and aVL,
were defined as the Q wave area in left circumflex artery
occlusion. Patients with left or right bundle branch block
(QRS duration ≥120 msec) were excluded from ECG
analysis. In-hospital and 30-day clinical data were also
accessed from the internet registry.

Statistical analysis
Discrete variables are presented as percentages and
compared with the Fischer’s exact test. Continuous vari-
ables are expressed as mean±SD and compared using
the Student’s t-test.

Results

Between January 2006, and July 2007, 2,635 patients
underwent coronary angiograms and 195 had at least
one CTO (7.4%). Eleven patients had 2 CTO lesions,
giving a total of 206 detected CTO lesions. The baseline
demographics of the patients are presented in Table 1.
About half of the patients had 3-vessel disease, and
CTOs were most commonly observed in the right coro-
nary arteries (Table 2).
PCI was not attempted in 61 patients: 58 patients
decided to only take medication and 3 patients were
referred for CABG. Recanalization using PCI was at-
tempted in 134 patients for 136 CTO lesions. Success-
ful recanalization with stent implantation was accom-
plished in 89 patients and 89 CTO lesions, giving a
procedural success rate of 66.4% (Table 2).
Recanalization was most frequently attempted for
CTO of the left anterior descending artery. In most
cases, coronary lesion passage was initially attempted
with a soft guidewire with microcatheter support. CTO
lesion passage was accomplished in 61 cases (success
Table 1. Baseline characteristics (n=195)
No (%)
Sex (M：F)
Age, year
Diabetes
Hypertension
Current smoker
CCS class III or IV angina
Creatinine >1.3 mg/dL
Total cholesterol >200 mg/dL
Triglyceride >150 mg/dL
LVEF measured by echocardiography
≤40%
>40%
Not available
Left ventricular RWMA
Yes
No
Not available
CCS: Canadian Cardiovascular Society classification system for an-
gina, LVEF: left ventricular ejection fraction, RWMA: regional wall
motion abnormality

141：54 (72：28)
62.6±11.3
80 (41.0)
118 (60.5)
48 (24.6)
56 (28.4)
35 (17.9)
63 (32.3)
55 (28.2)

27 (14.6)
142 (76.8)
16 (8.7)

68 (36.8)
101 (54.5)
16 (8.7)

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Chan Seok Park, et al.·113
rate: 44.1%). In 3 cases, guidewires with stiffer tips were
used initially. In the remaining 72 cases, coronary guide-
wires with stiffer tips were subsequently used to cross
over the CTO lesion, and lesion crossing was accom-
plished in 28 cases. After adequate balloon dilatation,
stent implantation was attempted. Sirolimus-eluting cor-
onary stents (SES) (CypherTM stent, Cordis Johnson and
Johnson, Miami, FL, USA) were the most common stent.
One patient died during the procedure due to no-reflow
phenomenon (Table 2).
Failure of guidewire crossover through the CTO le-
sion was the most common reason for unsuccessful pro-
cedures (38 CTO lesions: 80.9%). In 8 cases (17%), the
stent could not pass the CTO lesion although balloon
dilatation was successful. Unacceptable engagement of
the guiding catheter was the reason for failure in one
CTO lesion (2.1%).
Eight patients were excluded from the ECG analysis
because they had bundle branch block. More than 90%
of patients had regular sinus rhythm (n=181, 96.8%),
and atrial fibrillation was observed in 6 patients (Table
3). The presence of a Q wave was related to more severe
anginal symptoms according to the Canadian Cardio-
vascular Society (CCS) classification system for angina;
decreased left ventricular ejection fraction and regional
wall motion abnormality were observed by echocardio-
graphy (p<0.01), but other clinical and laboratory find-
ings did not differ whether the patients had Q waves
or not. The Q wave was not related to the procedural
success rate (p=0.55) (Table 4).

Discussion

Here we measured the clinical, electrocardiographic,
and procedural characteristics of CTO lesions in multi-
ple Korean centers. While the technical and procedural
success rates of PCI in CTOs have steadily increased
over the last 15 years because of greater operator expe-
rience and improvements in equipment and procedural
techniques,19)20) PCI of CTO lesions still has a low suc-
cess rate and is technically difficult. In a series of 1,074
consecutive patients undergoing PCI, the primary suc-
cess rate was 90% in non-occluded lesions, 78% in
functional total occlusions {Thrombolysis in Myocar-
dial Infarction (TIMI) flow grade 1}, and 63% in true
CTOs.21) Contemporary series found procedural success
Table 2. Angiographic and procedural characteristics of chronic
total occlusion lesions

Number of diseased vessels
Single
Multi
CTO vessel
LAD
LCX
RCA
Ramus
Target vessel of the lesion
LAD
LCX
RCA
Reference diameter (mm)
Lesion length (mm)
Guidewire that accomplished successful
lesion passage (n=97)
Soft wire
Choice PTTM
Stiff wire
Number of implanted stents
Implanted stents (n=135)
CypherTM
TaxusTM
EndeavorTM
CTO: chronic total occlusion, LAD: anterior descending coronary
artery, LCX: left circumflex artery, RCA: right coronary artery,
MACE: major adverse cardiac event

No (%)

33 (16.9)
162 (83.1)

62 (30.1)
44 (21.4)
99 (48.0)
1 (0.5)

41 (46.1)
17 (19.1)
31 (34.8)
3.00±0.32
32.66±16.80

30 (30.9)
33 (34.0)
34 (35.1)
1.5±0.8

92 (68.1)
29 (21.5)
14 (10.4)
Table 3. Electrocardiographic patterns in chronic total occlusion
patients

Sinus rhythm
Atrial fibrillation
Absence of Q wave and positive T wave
Absence of Q wave and T wave inversion
Q wave and positive T wave
Q wave and T wave inversion
No (%)
181 (96.8)
6 (3.2)
96 (51.3)
41 (21.9)
23 (12.3)
27 (14.5)

Table 4. Clinical, laboratory, and procedural characteristics ac-
cording to the presence of a Q wave

Q wave
n=60 (%)
Absence of
Q wave
n=127 (%)
62.7±10.8
91 (71)
22 (17)
51 (40)
72 (57)
33 (26)
23 (18)
45 (35)
35 (28)
56.9±11.5
28 (24)
41 (32)
56 (64.8)
p
Age, years
Male
CCS III or IV symptom
DM
Hypertension
Current smoker
Cr ≥1.3 mg/dL
TC ≥200 mg/dL
TG ≥150 mg/dL
EF
RWMA
T wave inversion
Procedural success rate
CCS: Canadian Cardiovascular Society classification system for an-
gina, DM: diabetes mellitus, Cr: creatinine, TC: total cholesterol,
TG: triglyceride, EF: left ventricular ejection fraction, RWMA: re-
gional wall motion abnormality
61.3±12.6
43 (71)
26 (43)
22 (37)
37 (62)
15 (25)
10 (17)
18 (30)
16 (27)
48.1±11.4
36 (64)
37 (62)
26 (70.2)
NS
NS
p<0.01
NS
NS
NS
NS
NS
NS
p<0.01
p<0.01
p<0.01
0.55

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114·Electrical and ECG Characteristics of CTOs

rates from 55% to 80%, with the variability reflecting
differences in operator technique and experience, av-
ailability of advanced guidewires, CTO definition, and
case selection.2)3)10)
We sampled subjects for a year and a half beginning
in Jan, 2006, when the internet-based coronary artery
database from Catholic Medical Center became avail-
able. Drug-eluting stents (DESs) became commercially
available in March, 2003, in Korea. Thus, bare metal
stents were not used in this study. The SES (CypherTM
stent, Cordis Johnson and Johnson, Miami, FL, USA)
was most common DES, in part because it was available
sooner than other DESs. In this study, the operator chose
the coronary stent.
The most common cause of the inability to cross the
lesion was failure to traverse the lesion with a guidewire,
which occurred at a similar percentage as previously
reported.22) The success rate for percutaneous CTO re-
canalization has improved over the last five years due to
the introduction of stiffer, more powerful, and more
supportive wires with greater torque responses.2) In this
study, we observed that a guidewire with a soft tip cros-
sed the CTO lesion in almost 70% of cases when the
operator was accustomed to manipulating the guidewire
and when the backup power was increased using a mi-
crocatheter. The procedural success of CTO was partic-
ularly dependent on operator skill and on case selec-
tion; therefore, every operator should be accustomed to
manipulating the guiding catheter and guidewire and
the coronary angiogram should be reviewed carefully
to identify anatomical structures, including collateral
flows, before the CTO procedure.
Although the procedural success rate was similar to
that in previous studies, MACE occurred in only one
patient during the procedure, perhaps due to differ-
ences in defining MACE. However, this finding also
suggests that PCI for CTO is a safe treatment choice
when the operator is comfortable with procedure and
the case is carefully selected. Many new techniques and
devices have improved the success rate of CTOs recan-
alization.23)24) Although successful PCI for CTO lesions
confers a long-term clinical advantage,24) controversies
remain whether all CTOs should be recanalized.
Various ECG parameters, such as T wave normaliza-
tion, help assess myocardial viability or recovery of func-
tion.17) We could not examine whether negative T waves
were normalized because our study was observational
in nature, using a internet-based registry in which fol-
low-up data were not available. The absence of a Q wave
predicts improved LV systolic function after successful
recanalization of CTO.18) Also, ECG before PCI can pre-
dict the functional outcome of intervention for CTO. Ac-
cording to our data, CTO patients with Q waves showed
more severe angina symptoms (CCS class III or IV); how-
ever, previous studies reported that LV function was less
likely to improve in these patients after successful PCI.25)
Thus, CTO patients with Q waves cannot be helped by
successful PCI for CTOs. However, our study also sug-
gests that improved LV function can be expected in
more than half of patients after successful PCI for CTO
lesions based on ECG patterns. The procedural success
rate was not influenced by ECG patterns.
This study has several limitations. The most impor-
tant limitation is that this is only an observational
study based on data in an internet-based registry. Also,
predictors of long-term survival or procedural success
cannot be explained in this study. The results of this
study were also influenced by differences in selection
criteria, operator experience, and technique among the
participating centers.
These data represent a multicenter series of consec-
utive patients with CTO in Korea. A relatively high suc-
cess rate with a low incidence of complications was ob-
served, indicating that further standardization of proce-
dures, especially of guidewire manipulation, will improve
the rate of successful PCI for CTO. PCI for CTO should
be seriously considered in selected CTO patients for
better clinical outcomes. Furthermore, all operators who
perform PCI for CTO should be accustomed to new
devices and techniques, such as the TornusTM cathe-
ter or the retrograde approach,2)23)24) to improve the suc-
cess rate of the procedure.

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