Context Several lines of evidence have implied an association between Chlamydia pneumoniae infection and atherogenesis.
Objective To determine the effect of 12 weeks of antibiotic therapy on coronary
heart disease events in patients with stable coronary artery disease and known C pneumoniae exposure.
Design, Setting, and Participants Randomized, placebo-controlled trial of 7747 adults with previous myocardial
infarction that had occurred at least 6 weeks previously (median, 2.6 years)
and a C pneumoniae IgG titer of 1:16 or more. Patients
were recruited from 271 clinical practices in North America, Europe, Argentina,
and India, from October 10, 1997, to July 22, 2001.
Intervention The patients received either azithromycin (600 mg/d for 3 days during
week 1, then 600 mg/wk during weeks 2-12; n = 3879) or placebo (n = 3868).
Main Outcome Measures The primary event was the first occurrence of death from any cause,
nonfatal reinfarction, coronary revascularization, or hospitalization for
angina. Patients were followed up until 1038 events accrued.
Results After a median of 14 months of follow-up, there was no significant risk
reduction in the likelihood of a primary event with azithromycin vs placebo
(7% [95% confidence interval, −5% to 17%], P =
.23). Analysis of hazard ratios suggested early benefits of azithromycin on
the primary event and on death or reinfarction, but these decreased over time.
There were no significant risk reductions for any of the components of the
primary end point including death (8%), recurrent myocardial infarction (7%),
revascularization procedures (5%), or hospitalizations for angina (−1%).
Adverse events related to study drug were reported by 13.2% of those randomized
to receive azithromycin, predominantly a result of diarrhea, compared with
4.6% randomized to receive placebo, and resulted in discontinuation of drug
in 1.6% of those taking azithromycin and 0.4% taking placebo.
Conclusion Among stable patients with previous myocardial infarction and with evidence
of C pneumoniae exposure, a 3-month course of azithromycin
did not significantly reduce the clinical sequelae of coronary heart disease.
Cardiovascular disease is one of the most common fatal diseases in North
America and Europe, and its incidence is increasing in developing countries.
Although various factors may initiate the atherosclerotic process, inflammation,
with activation of macrophages and T lymphocytes, is central.1 Candidate
antigens for stimulation of this inflammatory response have included noninfectious
moieties, including modified low-density lipoprotein (LDL) cholesterol, and
more recently, antigens derived from intracellular pathogens such as cytomegalovirus
and Chlamydia pneumoniae.2 In
addition to these local stimuli, cytokines generated from infections remote
from the plaque may also play a role. This inflammatory process, coupled with
plaque characteristics, may place patients at high risk of plaque rupture,
which manifests clinically as an acute coronary syndrome.3,4
Several lines of evidence have led to the association between infection
with chlamydia and atherogenesis. In 1988, a serological association was reported
between coronary disease and antibodies to C pneumoniae.5 Numerous reports since then have
confirmed this association. In addition, multiple studies of atherosclerotic
plaques have found evidence of C pneumoniae by immunohistochemical
stains, polymerase chain reaction analysis, or culture.6-12 Several
animal models have confirmed the potential for the development of atherosclerosis
after respiratory tract inoculation with chlamydia.13-17 Pilot
clinical trials of preventive antibiotic treatment in patients with coronary
disease have shown conflicting results, with some studies supporting18-21 and
others not supporting22,23 the
benefit of intervention. Larger, adequately powered studies are needed to
make definitive conclusions about the effectiveness of antibiotic intervention
in such patients.
The objective of the Weekly Intervention with Zithromax for Atherosclerosis
and its Related Disorders (WIZARD) study was to compare the effect of 12 weeks
of treatment with azithromycin vs placebo on recurrent coronary events in
a large population of stable patients with previous myocardial infarction
and with evidence of C pneumoniae exposure.
To be eligible for inclusion in the trial, patients must have had a
history of myocardial infarction more than 6 weeks before screening documented
by electrocardiogram or by elevation of creatine kinase and have an IgG titer
to C pneumoniae of 1:16 or greater by microimmunofluorescence.
Those who met the inclusion criteria could not have had coronary artery bypass
graft surgery or percutaneous coronary intervention in the preceding 6 months,
did not require chronic antibiotic therapy and had not received antibiotics
in the previous 3 months. Patients were enrolled at 271 centers from the United
States, Canada, United Kingdom, Germany, France, Spain, Austria, India, and
Argentina. Each of the participating sites received approval from an investigational
review board and all participants in the trial provided written informed consent.
The design of the WIZARD trial has been previously published.24 The trial began on October 10, 1997, and follow-up
concluded December 7, 2001. After a screening visit at which C pneumoniae antibody titers were measured, patients meeting eligibility
criteria were randomly assigned to receive either azithromycin 600 mg or a
matching placebo once daily for 3 days then once weekly for the subsequent
11 weeks. Sites were provided blinded medication in block sizes of 4, with
an equal proportion of each treatment assignment. Sealed envelopes containing
the treatment assignment were provided to each site, to be opened only in
case of an emergency. The sponsor monitored the integrity of these envelopes
at each monitoring visit. Patients, investigators, clinical site monitors,
and the sponsor project team remained blinded through study completion.
Patients were seen in the clinic for collection of blood samples or
contacted by telephone specifically at 6-week to 4-month intervals throughout
the trial. Blood samples were analyzed for red blood cell indices, creatinine,
and liver function.
A primary event was defined as death by any cause, recurrent myocardial
infarction, coronary revascularization procedure (coronary artery bypass graft
surgery or percutaneous coronary intervention), or hospitalization for angina,
whichever came first. A committee blinded to treatment assignment reviewed
detailed documentation of potential primary events for consistency with end
point criteria defined in the protocol. Reinfarction was defined by the presence
of 2 of the 3 following signs: the investigator's assessment of clinical signs
and symptoms of ischemia, an elevation in levels of cardiac markers, specifically
creatine kinase (CK) more than 2 times the upper limit of normal, CK-MB% at
least 3%, troponin I or T more than 2 times the upper limit of normal, or
new, diagnostic Q-waves in 2 contiguous leads. Hospitalization for angina
was defined as exacerbation of the patient's usual symptoms that resulted
in urgent hospitalization, supported by either electrocardiographic evidence
of ischemia or an elevated level of a cardiac marker (troponin I or T, CK,
or CK-MB) greater than normal but not diagnostic for myocardial infarction.
Components of the primary end point were analyzed separately. Predefined secondary
events included a noncoronary atherosclerotic event (stroke, transient ischemic
attack, or intervention for peripheral vascular disease, whichever occurred
first), cardiovascular death, and hospitalization for congestive heart failure.
A data and safety monitoring board was responsible for monitoring for
safety and efficacy. To preserve the overall type I error, an α-spending
approach was used to determine interim monitoring boundaries. A conditional
power calculation was used for determining the probability of a positive result.
An independent statistical analysis center prepared data and safety monitoring
board reports on the accumulating data.
The original sample-size calculations assumed that there would be a
primary-event rate of 8% per year in the placebo group and that the treatment
effect would be a 25% reduction in the hazard rate.24 If
these assumptions were met, the study with a total enrollment of 3300 patients
and a total of 522 primary events would have 90% power to detect a treatment
difference at a significance level of .05. The maximum study duration was
originally estimated to be 36 months. During the course of the trial, information
newly available provided support for the clinical utility of treatment effects
of as low as 15%. As a consequence, after approximately 83% of the original
targeted number of events had accrued, without unblinding the data, in April
2000, the protocol was amended to retain 90% power to detect a smaller treatment
effect of 18.5% such that the study would then conclude when 1038 end points
had accrued. To detect this effect within 12 to 24 months, approximately 4000
additional patients were enrolled.
Data analyses were conducted using a modified intention to treat approach
(all enrolled patients who received at least one dose of study drug). An evaluable
patient assessment was also performed that included patients who met inclusion
and exclusion criteria and took at least 80% of their assigned study drug
with patients censored after use of an antibiotic from the tetracycline, macrolide,
or quinolone classes. The primary analysis of the time to the primary event
was performed using the χ2 log-rank test. Components of the
primary event and secondary end points were analyzed in a similar manner.
Patients were censored at last contact or if all scheduled visits were completed
at study end. For secondary end points without death, patients were censored
at date of death. The Cox proportional hazards model was used to compute hazard
ratios (HRs) and to consider possible confounding variables while the cumulative
event curves were estimated by the product-limit (Kaplan-Meier) method. Risk
reduction was calculated as 100% × (1 − HR). Annualized event
rates are the number of events divided by person-years of follow-up. An assessment
for departures from the proportional hazards assumption was prespecified in
the protocol and formally tested by considering a Cox proportional hazards
model with a time-dependent time-treatment interaction. In addition, a series
of log-rank tests were performed on the observed data in which patients were
censored at 6 months, 12 months, and every 6 months thereafter until 4 years.
Statistical analyses were performed using SAS version 6.12 (SAS Institute
Inc, Cary, NC). For binomial data, the Pearson χ2 test was
Screening, Treatment, and Follow-up
Of the 11 451 patients who were screened, 7747 were randomized,
3538 of whom were randomized between October 10, 1997, and July 3, 1998, and
4209 between July 17, 2000, and July 22, 2001 (Figure 1). The primary reason for screening failure was an antibody
titer to C pneumoniae of less than 1: 16 (19.5%).
There was an equal distribution of patients by demographic variables including
cardiac risk factors (Table 1).
All but 25 randomized patients received the study drug. More than 90% of patients
completed the 12 weeks of study treatment. The median time since the patient's
most recent myocardial infarction was 2.6 years. The mean and median follow-up
times were 25 months in the 1997-1998 group and 14 months in the 2000-2001
group. Forty-six percent of the patients were followed up for at least 42
months whereas only 35% were followed up for fewer than 12 months. Approximately
4.5% of patients chose not to continue through the December 7, 2001, close
of the study.
Analyses of Primary and Secondary Events
The annualized primary event rate for patients receiving placebo was
8.02%. Treatment with azithromycin was associated with a 7% nonsignificant
reduction in the risk of the primary event (Figure 2) (95% CI, −5% to 17%; P =
.23). There were no significant reductions in the risk for any components
of the primary end point: death (8%), recurrent myocardial infarction (7%),
revascularization procedures (5%), or hospitalizations for angina (−1%).
Adjustment for cardiac risk factors including age, total cholesterol level,
and history of smoking, hypertension, or diabetes, produced a similar result
(RR, −6.5%; 95% CI, −5% to 17%; P = .27).
A variety of other sensitivity analyses were performed on the primary end
point (Figure 3). No difference
in conclusions was seen after analyzing the data with nonadjudicated, investigator-specified
end points (RR, 8%; 95% CI, −2% to 18%; P =
.13) or including only evaluable patients (RR, 9%; 95% CI, −4% to 21%; P = .16). The time to other events related to the progression
of atherosclerosis, including noncoronary disease (stroke, transient ischemic
attack, peripheral vascular disease), coronary angiograms, and hospitalizations
for congestive heart failure, was no different for either treatment regimen.
The proportional hazards assumption was examined because the length
of the treatment period was 12 weeks and there was concern that the effect
of treatment might be transient, a violation of this assumption. A Cox proportional
hazards model that included a time × treatment interaction suggested
an initial treatment effect that decreased with time for both the primary
end point (P = .15) and the composite of death or
recurrent myocardial infarction (P = .09). An analysis
of the treatment effect through various observation periods is provided in Figure 4.
No significant association between C pneumoniae titers
and treatment effect was observed (Figure
5). In addition, no association between titers to C pneumoniae and the likelihood of developing a primary event was seen
within the group of patients randomized to either azithromycin or placebo.
There was no difference between treatment groups at baseline or after baseline
in the distribution of C pneumoniae titers. The risk
reduction for the primary event was unchanged when the log of the baseline C pneumoniae titer was included in the Cox proportional
To investigate the effect of treatment within subpopulations, several
different analyses were performed. Within groups of patients sharing specific
cardiovascular risk factors, trends in reduction of risk attributed to treatment
were most apparent in men, patients with diabetes, active smokers at baseline,
and those with a history of hypercholesterolemia (Figure 5). In the subgroup of patients who had diabetes and smoked
(n = 237), the annualized event rate for the primary end point was 14.6% for
those receiving azithromycin vs 53% for those receiving placebo (HR, 0.47;
95% CI, 0.25-97).
In examining the treatment effect within the subsets of patients taking
aspirin, statins, angiotensin-converting enzyme inhibitors, or calcium channel
blockers (data not shown), no difference between the azithromycin and placebo
groups was identified. In addition, an analysis assessing treatment effect
by the total number of any one of these medications did not have a noticeable
impact on study end point. No significant difference in treatment effect was
observed when patient subpopulations were assessed by the time since their
most recent myocardial infarction.
Adverse events related to study drug were reported by 13.2% of those
randomized to azithromycin compared with 4.6% randomized to placebo. The most
common adverse effects were related to the gastrointestinal tract, including
diarrhea (8.1% vs 1.4%) and abdominal pain (2.2% vs 0.8%). Discontinuations
from drug occurred in 1.6% and 0.4% of patients receiving azithromycin and
placebo, respectively. There were fewer episodes of respiratory tract infection,
bronchitis, pneumonia, or sinusitis reported during study drug dosing among
patients taking azithromycin compared with those taking placebo (6.4% vs 9.4%,
respectively; P<.001). Patients receiving azithromycin
reported less use of other antibacterial drugs during the course of the study
(32.7% vs 36.6%, P<.001).
In stable patients with a previous myocardial infarction and evidence
of previous exposure to C pneumoniae, 12 weeks of
azithromycin therapy was not associated with a significant reduction in the
occurrence of death, nonfatal reinfarction, hospitalization for angina, or
coronary revascularization. The size of our study, the largest antibiotic
treatment trial to date, essentially rules out the possibility of a large
and durable benefit in secondary prevention with a 3-month course of azithromycin
therapy and should point investigators toward consideration of alternative
durations of therapy or analyses of different subsets of patients with cardiovascular
disease. There may have been a greater likelihood of observing an effect in
patients with conventional risk factors for cardiovascular disease, including
men, patients with diabetes, and those who smoked or had a history of elevated
total cholesterol levels. Studies focused on these subpopulations will be
required to confirm these preliminary observations.
The use of an antibiotic to prevent the development of clinical coronary
heart disease is based on the hypothesis that an underlying infection could
predispose an individual to progression of an atherosclerotic plaque. Work
by Espinola-Klein et al25 has suggested that
patients with seropositivity to multiple pathogens have an increased prevalence
of advanced atherosclerosis and a greater risk of death, with mortality rates
ranging from 1.4% with 0 to 3 seropositive findings and limited atherosclerosis,
to 20% with 6 to 8 seropositive results and more advanced atherosclerosis.
Although a number of pathogens have been proposed to serve as the infectious
stimuli, it is for C pneumoniae that the most supportive
data exists. Although patients in this trial were enrolled if they had evidence
of previous exposure to C pneumoniae, no evidence
of a treatment effect related to the degree of antibody titer was identified.
Titers were also not predictive of the likelihood of developing an event during
the study. Does this imply that C pneumoniae does
not contribute to the development and progression of the atherosclerotic plaque?
This trial was not designed to assess the role of C pneumoniae in cardiovascular disease. The limited utility of antibody
titers to C pneumoniae has been well described26 and the findings in this study regarding antibody
titers are not inconsistent with those views. Selecting patients based on
the actual presence of the organism, perhaps by polymerase chain reaction
analysis of circulating white blood cells, may prove to be a better way to
test for the role of antibiotic therapy directed against C pneumoniae.
The observation that a treatment effect may have waned over time is
supported by a possible treatment × time interaction, suggesting that
if there was an effect, future study designs may need to consider repeated
dosing or longer durations of therapy. The dosing regimen for this study was
chosen based on providing exposure of C pneumoniae to
intracellular levels of azithromycin that exceeded the known 90% minimum inhibitory
concentration of the organism but the duration of that exposure was empirically
selected to exceed prior exposures with macrolides for this purpose. The incidence
of death or nonfatal reinfarction was reduced by 30% at 6 months, with CIs
for the hazard ratio that exclude 1 (Figure
4), shortly after stopping therapy. There was a similar trend shown
for the primary composite end point, with an upper limit of 1.02 for the CI.
In trials in which the observation period extends over a number of years,
the duration of therapy may need to be longer. The fact that we saw this possible
trend (a reduction in events that wanes over time) provides some support for
the argument that longer suppressive therapy may be advantageous in this patient
population. Indeed, the effect of longer-duration antibiotic therapy is being
evaluated in the Azithromycin and Coronary Events study.27 Although
azithromycin has significant activity against C pneumoniae, certain subpopulations of organisms may be less susceptible to eradication.
Further efforts to understand the organism in this state may prove fruitful,
both for selection of antibiotics or combinations of antibiotics and for manipulating
the microenvironment to move organisms out of this state.
The goal of the WIZARD trial was to investigate a practical short-term
regimen of antibiotic therapy for stable patients who had a low to moderate
risk of secondary cardiovascular events and previous exposure to C pneumoniae. Based on our findings, we cannot recommend this therapy
for prevention of recurrent coronary heart disease in this patient population.
These data do, however, establish a safety profile for the use of this antibiotic
in this type of cardiovascular patient.
In summary, a 12-week course of azithromycin did not significantly reduce
the incidence of coronary heart disease–related events in stable postmyocardial
infarction patients with evidence of previous exposure to C pneumoniae. In a post hoc analysis, there appeared to be a possible
early treatment effect that was not sustained over the observation period.
While subgroup analyses are intriguing, justification for the use of antibiotics
to treat patients with coronary heart disease must await results of future
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