(Circulation. 1995;92:1-7.)
© 1995 American Heart Association, Inc.
Articles |
Asymptomatic Cardiac Ischemia Pilot (ACIP) Study
Improvement of Cardiac Ischemia at 1 Year After PTCA and CABG
Correspondence to Martial G. Bourassa, MD, Montreal Heart Institute, 5000 Belanger St, Montreal, Quebec, Canada H1T 1C8.
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Abstract |
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 Top Abstract IntroductionMethods Results Discussion References |
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Background Cardiac ischemia on the ambulatory ECG (AECG) and/or on the exercise treadmill test (ETT) is associated with an increased risk of adverse outcome. Myocardial revascularization more often suppresses cardiac ischemia than does medical management alone. However, few studies have compared the effects of percutaneous transluminal coronary angioplasty (PTCA) with those of coronary artery bypass grafting (CABG) on cardiac ischemia and clinical outcome.
Methods and Results A total of 558 patients were randomly assigned to one of three treatment strategies in the Asymptomatic Cardiac Ischemia Pilot (ACIP) study: angina-guided medical strategy (n=184), ischemia-guided medical strategy (n=182), or revascularization (n=192). In patients assigned to revascularization, the choice of the procedure, PTCA or CABG, was made by the clinical unit staff and patient based on a coronary angiogram usually performed within 2 months of enrollment. CABG was selected in 78 patients and PTCA in 92 patients. At 12 weeks, ischemia on the AECG was suppressed in 70% of CABG patients versus 46% of PTCA patients (P=.002). Ischemia on the ETT was no longer present in 46% versus 23% of the patients, respectively (P=.005). Angina, within 4 weeks of the follow-up visit, was absent in 90% versus 68%, respectively (P=.001). These clinical variables remained improved in both groups at 1 year. Clinical events (myocardial infarction or repeat revascularization) occurred in 1 CABG patient versus 7 PTCA patients at 12 weeks, and in 1 versus 16 patients, respectively, at 12 months (P<.001).
Conclusions Ischemia on the AECG and ETT and angina were relieved in many patients after both procedures; however, CABG was superior to PTCA, and it was associated with a lower incidence of clinical events at 1 year. These results suggest that more complete revascularization relates to better clinical outcome. However, a large trial is needed to confirm these results.
Key Words: angioplasty • ischemia • exercise • electrocardiography • bypass
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Introduction |
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TopAbstractIntroductionMethods Results Discussion References |
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Cardiac ischemia documented on the AECG and/or on the ETT has been associated with an increased risk of adverse clinical outcome.1 2 3 4 While cardiac ischemia can be suppressed by medical therapy and by myocardial revascularization in a high percentage of patients, it has been shown in the ACIP study recently that revascularization is superior to medical management alone in the relief of cardiac ischemia.5 Whether this increased efficacy will result in a better clinical outcome, however, remains to be demonstrated in larger mortality and morbidity trials.
The relative efficacy and safety of PTCA compared with those of CABG in the suppression of cardiac ischemia have not been adequately documented prospectively. A recent ACIP report suggests that CABG is superior to PTCA in the early suppression of cardiac ischemia.6 However, it is not known whether this improvement persists over time. The purpose of this report is to describe the effects of PTCA versus CABG on cardiac ischemia and clinical events during the first year after revascularization in patients enrolled in the ACIP study and randomized to revascularization.
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Methods |
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TopAbstractIntroductionMethods Results Discussion References |
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Study Design
Details of the ACIP study design have been described previously.7 8 Briefly, patients who had angiographic evidence of obstructive coronary artery disease (
50%
diameter stenosis), evidence of stress-related
ischemia during an ACIP ETT (or an alternative stress test if
the patient could not exercise), and one episode or more of
asymptomatic cardiac ischemia (1-mm
ST-segment deviation from baseline, lasting 1 min, and separated from
other episodes by at least 5 minutes) on a 48-hour AECG were eligible
for enrollment in ACIP. After giving informed consent, they were
randomly assigned to one of three treatment strategies:
angina-guided medical strategy with titration of
anti-ischemia medication to relieve symptoms (n=184),
ischemia-guided medical strategy with titration of
anti-ischemia medication to eliminate both angina and AECG
ischemia (n=182), or revascularization of
all important stenoses in major coronary arteries
(n=192). Patients assigned to revascularization were to undergo either PTCA or CABG within 4 weeks (6 weeks if staged angioplasty was performed) of the baseline qualifying visit. The goal was to achieve correction of all important stenoses in major coronary arteries. The choice of PTCA or CABG was made by the clinical unit staff and patient, based on coronary angiography usually performed within 2 months of revascularization. In general, CABG was considered for patients with multivessel disease and PTCA for patients with single-vessel disease or multivessel disease when the important lesions in major coronary arteries were suitable for coronary angioplasty.
Angiographic characteristics making surgery preferable were diffuse coronary disease with lesions >20 mm in length, excessive tortuosity or angulation of the involved artery, occluded arteries, inability to protect major side branches, and lesions located so that abrupt vessel closure would result in high risk of cardiogenic shock.9
The patient was considered suitable for angioplasty if the lesions satisfied previously established guidelines.10 11 The immediate outcome of the intervention was classified as successful by the clinical unit staff if all attempted stenoses in major coronary arteries were reduced to <50% luminal diameter as measured by electronic calipers, and the patient was free of procedure-related complications such as death, myocardial infarction, or emergency CABG surgery. Anatomic success was defined by the Angiography Core Laboratory as a postangioplasty stenosis <50% for any lesion or for all lesions attempted.
Medical therapy after revascularization was based on local clinical practice. The patient's management of angina after revascularization was changed to the ACIP regimen (atenolol/nifedipine or diltiazem/isosorbide dinitrate), assigned randomly, unless one regimen was contraindicated.5 7 8
Outcome Assessment
In ACIP, the primary outcome measure was
complete suppression of
ischemic episodes on the 48-hour AECG obtained at the 12-week
visit (84 to 182 days) after enrollment or approximately 8 weeks after
revascularization. Secondary outcomes included
other measures related to ischemia from the 48-hour AECG, ACIP
protocol ETT, and clinical outcomes.
The protocol mandated a 48-hour AECG and an ACIP ETT (if done during screening) for all patients at the 12-week, 6-month, and 12-month visits. Anginal status was also assessed at those visits. Clinical outcome was documented for patients who died, who had a myocardial infarction, or who had nonprotocol revascularization. Patients who died, who had a myocardial infarction, or who had a nonprotocol repeat revascularization procedure before a scheduled visit were counted as having ischemia present on the 48-hour AECG at that visit, regardless of AECG findings. Classification of major clinical events, such as death and myocardial infarction, was performed by an independent Mortality and Morbidity Classification Committee.
The ACIP study protocol was approved by Institutional Review Committees at each participating site. Written informed consent was obtained from all patients before study entry. An independent Data and Safety Monitoring Board reviewed the safety of treatments as well as protocol adherence and potential protocol changes at 6-month intervals.
Statistical Methods
Statistical analyses of categorical data
were performed
using Fisher's exact test or a 
2 test, and
analyses of continuous data were performed using a Student's
t test. The Wilcoxon rank-sum statistic was used
for testing the distributions of AECG episodes. The percentage of
patients with ischemic ST-segment depression during the initial
10 minutes of the exercise test was estimated using the Kaplan-Meier
method12 ; patients who did not complete 10 minutes of
exercise for reasons other than ST-segment depression were censored
without the event at the time the test was stopped. This analytic
method was also used to estimate the time to angina onset and time to
onset of 1-mm ST-segment depression if the event rate was
>50%.
To take into account the many hypotheses tested in the ACIP study, in these secondary analyses P=.01 was regarded as showing some evidence against the null hypothesis, and P=.001 was regarded as strong evidence.
To adjust for
discrepancies in demographic factors, presence of risk
factors, and clinical differences between the PTCA and CABG groups
before treatment,6 multivariable analyses were performed to
account for these differences. The following 10 baseline variables were
used as adjusting variables in multivariable analyses using the Cox
proportional-hazards model13 and in multivariable logistic
regression analysis14: age, male sex, angina present, prior
MI, diabetes, hypertension, ever smoked, prior revascularization (PTCA
or CABG), number of vessels with stenosis 50%, and number of
ischemic episodes on qualifying AECG.
All data processed in the Clinical Coordinating Center as of January 18, 1995, were included in these analyses.
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Results |
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TopAbstractIntroductionMethods Results Discussion References |
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Performance of Protocol Revascularization
Data reported here are for 558 patients (all 60 patients from one clinical unit have been excluded as reported by Conti et al).15
Of 192 patients assigned to undergo revascularization in the ACIP study, 94 had PTCA attempted, 79 had CABG performed, and 19 did not have any revascularization procedure performed because the patient or treating physician refused after enrollment. Three patients, 2 in the PTCA group and 1 in the CABG group, who had their procedures done after the 12-week visit were excluded from the analysis. Thus, this report is based on 92 patients in whom PTCA was attempted and on 78 patients in whom CABG was performed. The median time interval from study entry to revascularization was 18 days for PTCA and 32 days for CABG.
Multivessel disease was present in 86% of patients undergoing CABG and single-vessel disease in 14%. The average number of grafts was three, and the number of grafts matched or exceeded the number of diseased major coronary arteries in 95% of patients. Internal thoracic artery grafts were used in 85% of patients (one graft in 71% and two grafts in 14%). One patient had another arterial graft.
Multivessel disease was present in 62% of patients undergoing PTCA and single-vessel disease in 38%. By clinical unit assessment, the procedure was successful in 83% of patients. Angiography Core Laboratory assessment of anatomic success was 82% when defined as postangioplasty stenosis <50% for any lesion attempted and 78% for all lesions attempted. One lesion was successfully dilated in 73% of patients, two in 23%, and three in 4%. One vessel was dilated in 89% of patients and two vessels in 11%. Complete revascularization was achieved after PTCA in 32% of patients.
There was no death or myocardial infarction during the 24 hours after CABG. Five patients had other complications: One patient had a stroke followed by recovery with no residual neurological impairment, and four patients were reoperated on for bleeding. Within 24 hours of PTCA, there were three events in two patients: One patient had a nonfatal myocardial infarction and CABG, and another patient had emergency CABG surgery.
AECG Results
At the baseline qualifying visit, patients
considered for CABG had
more ischemic episodes (median, 5 versus 3; P<.001)
and a longer duration of ischemia (median, 28 versus 21
minutes) per 48 hours than patients selected for PTCA (Table
1
).
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At the 12-week visit, the percentage of patients
with no
ischemic episodes (primary outcome) was 70% in the CABG
patients versus 46% in the PTCA patients (P=.002). The
proportion of patients without ischemia on the 48-hour AECG
remained practically unchanged at the 6-month (64%), and 12-month
(71%) visits in the CABG patients, whereas it increased slightly but
not significantly (49% at the 6-month visit and 52% at the 12-month
visit) in the PTCA patients (Table 1
and Fig 1).
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Mean and maximum heart rates for the 48-hour recording were
significantly lower in the PTCA than in the CABG patients, probably
because of greater use of heart rate–lowering
anti-ischemia medication in these patients (Table 1).
AECG results were available at the qualifying, 12-week, 6-month, and
12-month visits in 100%, 91%, 96%, and 95% of the PTCA patients,
respectively, and in 100%, 95%, 99%, and 94% of the CABG patients,
respectively (Table 1).
ETT Results
At the qualifying visit, of those selected for
CABG there were
more patients with 1-mm ST-segment depression, more
exercise-induced angina, a lower total exercise time, a lower time
to 1-mm ST-segment depression, and a lower percentage of age maximum
heart rate than patients selected for PTCA (Table 2).
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At
the 12-week visit, the percentage of patients without ST-segment
depression on the ETT was higher in the CABG group than in the PTCA
patients (46% versus 23%, P=.005). The percentage of
patients without exercise-induced angina was also higher in the
CABG than in the PTCA group (90% versus 70%, P=.01). Time
to 1-mm ST-segment depression was greater in the CABG than in the PTCA
patients (7.6 versus 6.5 minutes, P=.005) and the number of
abnormal ECG leads (1.7 versus 3.1, P<.001), the sum of
ST-segment depression (3.6 versus 7.0, P<.001), and the
maximum depth of ST-segment depression in any lead (0.9 versus 1.7,
P<.001) were less in the CABG than in the PTCA patients,
respectively. Finally, the percentage of age maximum heart rate was
greater in the CABG than in the PTCA patients (93% versus 85%,
P<.001). All these differences, except for the incidence of
exercise-induced angina, persisted relatively unchanged on the ETTs
performed at the 6-month and 12-month visits (Table 2
and Fig 2).
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ETT results were available and interpretable
at the qualifying,
12-week, 6-month, and 12-month visits in 99%, 91%, 92%, and 90% of
the PTCA patients, respectively, and in 99%, 91%, 95%, and 92% of
the CABG patients, respectively (Table 2).
Anginal Status and Antianginal Medication Within 4
Weeks
At the qualifying visit, the percentage of patients who were
angina-free within 4 weeks before entry was 28% in the CABG
patients compared with 42% in the PTCA patients (NS). According to the
Canadian Cardiovascular Society classification, angina
was class I in 37% versus 24% of patients, respectively; class II in
30% versus 33%, respectively; class III in 5% versus 1%,
respectively; and class IV in 0% versus 0%, respectively (Table
3).
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At the 12-week visit, 90% of the CABG patients
versus 68% of the PTCA
patients (P=.001) had not experienced any angina within the
previous 4 weeks. In those who were still symptomatic,
angina was mild to moderate, Canadian Cardiovascular
Society class I or II, in all but one PTCA patient. No patient
experienced unstable angina before the 12-week visit. The percentage of
patients taking study medication (background or open label to relieve
angina) within 4 weeks before the follow-up visit was 10% after
CABG versus 49% after PTCA; the percentage of patients taking one drug
was 12% versus 36%, respectively, and the percentage taking two drugs
was 0% versus 13%, respectively. All these differences remained
significant at the 6-month and 12-month visits (Table 3 and Fig
3).
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The angina and medication data were available at the
qualifying visit
in all patients of both revascularization groups,
and at the 12-week, 6-month, and 12-month visits in 100%, 100%, and
100% of PTCA patients, respectively, and in 99%, 100%, and 96% of
CABG patients, respectively (Table 3).
Clinical Events
At 12 weeks, only 1 patient had had a
clinical event (myocardial
infarction) in the CABG group, whereas 7 patients had had clinical
events (3 myocardial infarctions, 2 repeat PTCAs, and 4 CABG surgeries)
in the PTCA group. There was no death or additional myocardial
infarction in either group during follow-up at 6 and 12 months. A
PTCA was performed between 3 and 6 months after study entry in one
surgical patient. On the other hand, the number of patients requiring
repeat revascularization (PTCA and/or CABG) in the
angioplasty group increased from 6 at 84 days to 11 at 183 days and to
15 by 365 days. Overall, the number of clinical events was 1 in the
CABG patients versus 12 in the PTCA patients at 183 days
(P=.004) and 1 versus 16 at 365 days (P<.001,
adjusted P=.006) (Table 4 and Fig
4).
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Follow-up for clinical events was 100% complete in both treatment groups through 365 days.
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Discussion |
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TopAbstractIntroductionMethods Results Discussion References |
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This report describes the 1-year follow-up of patients who were assigned to revascularization in the ACIP trial and extends the observations previously made 12 weeks after randomization.6 The frequency and severity of cardiac ischemia on the 48-hour AECG and on the ACIP protocol ETT and the frequency and severity of angina within the previous 4 weeks were markedly reduced 12 weeks after entry (approximately 8 weeks after randomization) after both PTCA and CABG. However, CABG was more effective than PTCA in suppressing cardiac ischemia and angina at the 12-week visit in the ACIP trial. Cardiac ischemia on the 48-hour AECG, the primary outcome of the study, was eliminated at 12 weeks in 70% of CABG patients versus 46% of PTCA patients, and within 4 weeks of the 12-week visit angina was no longer present in 90% of patients after CABG versus 68% after PTCA. The present report shows that the improvement in angina and ischemia seen at 12 weeks remained significant at the 1-year follow-up visit and that the difference in efficacy between the two procedures also persisted at 1 year. Moreover, the surgical patients had a lower incidence of clinical events at 1 year in the ACIP trial. Clinical events defined as death, nonfatal myocardial infarction, and nonprotocol repeat revascularization were observed at 1 year in only 1 surgical patient compared with 16 angioplasty patients. The incidence of death or myocardial infarction at 1 year was not different in the two treatment groups: 1 event in the surgical patients versus 3 in the angioplasty patients. However, the incidence of repeat revascularization (PTCA or CABG) during the 1-year follow-up period was much higher in the PTCA than in the CABG patients: 15 repeat procedures after the index PTCA versus 1 after the initial CABG.
Previous observational studies have shown that each PTCA or CABG can safely and effectively reduce myocardial ischemia in patients with symptomatic or asymptomatic coronary artery disease.16 17 18 19 20 21 These studies have not clearly established, however, whether ischemia suppression is related to completeness of revascularization18 19 20 and whether ischemia suppression after revascularization influences long-term prognosis.17 19 20
Four randomized trials comparing the efficacy and safety of PTCA versus CABG in the management of patients with symptomatic coronary artery disease have been published recently.22 23 24 25 These trials have shown that, as a rule, the incidence of major coronary events including death and nonfatal myocardial infarction is not different between 1 and 3 years after revascularization among patients assigned to either PTCA or CABG. However, compared with CABG surgery, PTCA is associated with a fourfold to tenfold increase in repeat revascularization during this time period. The design of these trials differs from the ACIP protocol in several respects. Except for the Randomized Intervention Treatment of Angina (RITA) trial in which approximately one half of the patients had single-vessel disease,22 all the other trials were performed in patients with multivessel coronary disease. In the four trials, the patients were randomly assigned to either PTCA or CABG and thus had to present angiographic lesions that were suitable for both procedures. In the ACIP trial, the patients had to have angiographic lesions that were suitable for either PTCA or CABG; they were randomly assigned to revascularization, and the choice of the procedure, PTCA or CABG, was made by the physician and patient, based on the angiographic results. Thus, the ACIP protocol captured a much greater patient population. Yet, the clinical outcome at 1 year after revascularization by PTCA or CABG in the ACIP trial was similar to that of these other trials.
A reduction in mortality for up to 10 years after CABG, compared with medical management, in medium-risk and high-risk patients with stable coronary artery disease has been documented in several previous trials.26 There is also evidence suggesting that, in patients with triple-vessel disease and patients with double-vessel disease in whom a critical lesion of the left anterior descending artery is present, 5-year survival is greater after CABG surgery than after PTCA.27 In view of the current evidence that cardiac ischemia is associated with an increased risk of adverse clinical outcome1 2 3 4 and that revascularization, and in particular CABG surgery, offers the best strategy to eliminate cardiac ischemia,5 a long-term trial evaluating the effect of ischemia suppression on clinical outcome using the ACIP protocol is warranted.
The present study has several limitations. First, the revascularization procedure was not randomly assigned. However, we feel that the ACIP study design where the choice of PTCA or CABG was determined by the physician and patient corresponds closely to the usual pattern of routine clinical practice. Second, the degree of revascularization achieved by PTCA and CABG was not ascertained by a follow-up coronary angiogram relatively late (1 year) after revascularization. This information would have been very helpful to correlate the reduction of ischemia with completeness of revascularization in both procedures. Finally, the number of events in both treatment groups is too small to allow any definitive conclusions, and the effect of ischemia suppression after revascularization on clinical outcome will require a much larger and more long-term mortality trial.
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Selected Abbreviations and Acronyms |
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Acknowledgments |
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The present study was funded by the National Heart, Lung, and Blood Institute, Cardiac Diseases Branch, Division of Heart and Vascular Diseases, Bethesda, Md, by research contracts HV-90-07, HV-90-08, and HV-91-05 through HV-91-14. Study medications and placebo were donated by Zeneca Pharma Inc, Marion-Merrell Dow, and Pfizer. Support for ECG data collection was provided in part by Applied Cardiac Systems, Marquette Electronics, Mortara Instrument Incorporated, and Quinton Instruments.
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Footnotes |
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Reprint requests to ACIP Clinical Coordinating Center, Maryland Medical Research Institute, 600 Wyndhurst Ave, Baltimore, MD 21210.
1 A list of participating centers and investigators is included in
"Asymptomatic Cardiac Ischemia Pilot (ACIP) Study: Outcome at One Year
for Patients With Asymptomatic Cardiac Ischemia Randomized to Medical Therapy
or Revascularization," J Am Coll Cardiol (in press). 
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P. Taggart, P. M.I Sutton, T. Opthof, R. Coronel, R. Trimlett, W. Pugsley, and P. Kallis Transmural repolarisation in the left ventricle in humans during normoxia and ischaemia Cardiovasc Res, June 1, 2001; 50(3): 454 - 462. [Abstract] [Full Text] [PDF]
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S. J. Conway, J. Bundy, J. Chen, E. Dickman, R. Rogers, and B. M. Will Decreased neural crest stem cell expansion is responsible for the conotruncal heart defects within the Splotch (Sp2H)/Pax3 mouse mutant Cardiovasc Res, August 1, 2000; 47(2): 314 - 328. [Abstract] [Full Text] [PDF]
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K. A. Eagle, R. A. Guyton, R. Davidoff, G. A. Ewy, J. Fonger, T. J. Gardner, J. P. Gott, H. C. Herrmann, R. A. Marlow, W. C. Nugent, et al. ACC/AHA guidelines for coronary artery bypass graft surgery: A report of the American College of Cardiology/ American Heart Association task force on Practice Guidelines (Committee to revise the 1991 Guidelines for Coronary Artery Bypass Graft Surgery) J. Am. Coll. Cardiol., October 1, 1999; 34(4): 1262 - 1347. [Full Text] [PDF]
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J. J. Munoz, N. J.O. Birkmeyer, L. J. Dacey, J. D. Birkmeyer, D. C. Charlesworth, E. R. Johnson, S. J. Lahey, M. Norotsky, R. D. Quinn, B. M. Westbrook, et al. Trends in rates of reexploration for hemorrhage after coronary artery bypass surgery Ann. Thorac. Surg., October 1, 1999; 68(4): 1321 - 1325. [Abstract] [Full Text] [PDF]
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J. R. Kaseta, D. F. Skafar, J. L. Ram, S. J. Jacober, and J. R. Sowers Cardiovascular Disease in the Diabetic Woman J. Clin. Endocrinol. Metab., June 1, 1999; 84(6): 1835 - 1838. [Abstract] [Full Text]
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I. Gussak, C. Antzelevitch, P. Bjerregaard, J. A. Towbin, and B. R. Chaitman The Brugada syndrome: clinical, electrophysiologic and genetic aspects J. Am. Coll. Cardiol., January 1, 1999; 33(1): 5 - 15. [Abstract] [Full Text] [PDF]
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M. R. Rosen, I. S. Cohen, P. Danilo Jr., and S. F. Steinberg The heart remembers Cardiovasc Res, December 1, 1998; 40(3): 469 - 482. [Full Text] [PDF]
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B. Z. Simkhovich, K. Przyklenk, and R. A. Kloner Role of protein kinase C as a cellular mediator of ischemic preconditioning: a critical review Cardiovasc Res, October 1, 1998; 40(1): 9 - 22. [Abstract] [Full Text] [PDF]
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R. H. Dave, S. L. Hale, and R. A. Kloner The Effect of Melatonin on Hemodynamics, Blood Flow, and Myocardial Infarct Size in a Rabbit Model of Ischemia-Reperfusion Journal of Cardiovascular Pharmacology and Therapeutics, January 1, 1998; 3(2): 153 - 159. [Abstract] [PDF]
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P. J. Nestel, T. Yamashita, T. Sasahara, S. Pomeroy, A. Dart, P. Komesaroff, A. Owen, and M. Abbey Soy Isoflavones Improve Systemic Arterial Compliance but Not Plasma Lipids in Menopausal and Perimenopausal Women Arterioscler. Thromb. Vasc. Biol., December 1, 1997; 17(12): 3392 - 3398. [Abstract] [Full Text]
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M. R. Bennett, V. Lindner, D. DeBlois, M. A. Reidy, and S. M. Schwartz Effect of Phosphorothioated Oligonucleotides on Neointima Formation in the Rat Carotid Artery : Dissecting the Mechanism of Action Arterioscler. Thromb. Vasc. Biol., November 1, 1997; 17(11): 2326 - 2332. [Abstract] [Full Text]
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P. Holm, M. Shalmi, N. Korsgaard, B. Guldhammer, S. O. Skouby, and S. Stender A Partial Estrogen Receptor Agonist With Strong Antiatherogenic Properties Without Noticeable Effect on Reproductive Tissue in Cholesterol-Fed Female and Male Rabbits Arterioscler. Thromb. Vasc. Biol., October 1, 1997; 17(10): 2264 - 2272. [Abstract] [Full Text]
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