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Physicians' Recommendations to Patients
for Use of Antibiotic Prophylaxis to Prevent Endocarditis
Todd
B. Seto, MD, MPH; David Kwiat, BS; Deborah
A. Taira, ScD; Pamela S. Douglas, MD;
Warren J. Manning, MD
JAMA. 2000;284:68-71.
ABSTRACT
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Context The American Heart Association
recommendations for infectious endocarditis (IE)
prophylaxis, published in June 1997, sought to improve
patient and physician compliance by simplifying the
dosing regimen and clarifying endocarditis risk.
Adherence to these updated recommendations in patients
with echocardiographic verification of their endocarditis
risk profile is unknown.
Objective To determine the recommended and actual
use of IE prophylaxis as reported by patients undergoing
echocardiography.
Design, Setting, and Participants All patients who
underwent outpatient transthoracic echocardiography at a
university-based tertiary hospital in Boston, Mass,
during December 1997 were contacted 6 to 9 months later
to respond to a survey, completed by 218 (80%) eligible
subjects.
Main Outcome Measure Patients' report of their
physicians' instructions on actual use of IE prophylaxis
in accordance with patient risk category, determined by
echocardiographic data.
Results One hundred eight patients (49.5%) had
clinical or echocardiographic findings for which
prophylaxis was indicated. Of these 108 patients, 71
(65.7%) reported that they were instructed to take IE
prophylaxis. Sixteen high-risk patients (88.9%) but only
55 moderate-risk patients (61.1%) reported that they were
instructed to take prophylaxis. Among the 110
negligible-risk patients, 29 (26.4%) reported that they
had been instructed to take IE prophylaxis. Overall, 100
patients (45.9%) reported that they received physician
instructions to take IE prophylaxis. Of those who
subsequently underwent a procedure for which IE
prophylaxis was indicated (n=68), 9 (13.2%) elected not to
follow their physician's advice to take prophylaxis.
Conclusions We found that although most patients
reported receiving instructions for IE prophylaxis use
consistent with American Heart Association guidelines, IE
prophylaxis overuse among negligible-risk patients and
underuse among moderate-risk patients was common.
Continued physician and patient education may lead to
improved adherence to the current American Heart
Association recommendations.
INTRODUCTION
Infective
endocarditis (IE) continues to cause substantial morbidity
and carries a mortality rate up to 21% for patients with
native valve endocarditis and higher than 50% for
patients with prosthetic valve endocarditis.1-6
Used for more than 50 years, antibiotics to prevent IE
have become a medical7
and legal1
standard for appropriate care, despite the lack of
randomized controlled human trials demonstrating efficacy
and retrospective studies questioning their
effectiveness.8-10
First published in 1955, the American Heart Association's
(AHA's) recommendations for IE prevention were updated in
June 1997.7
Recognizing that 75% of patients with IE have preexisting
cardiac structural abnormalities,1
the AHA recommended IE prophylaxis for patients at
moderate and high risk for IE prior to procedures known
to produce bacteremia. With evidence of poor compliance
despite prior recommendations,11-16
a goal of the AHA's 1997 recommendations was to improve
patient and physician compliance by simplifying the
antibiotic dosing regimen and clarifying which patients
are at risk for IE.7
Although prior recommendations based the assessment of
risk on clinical or auscultatory findings, the 1997 AHA
recommendations7
recognized the widespread availability of
echocardiography and recommended it be performed for patients
with suspected valvular lesions to demonstrate the need
for prophylaxis. However, compliance with these updated
recommendations in patients with echocardiographic
verification of their IE risk profile is unknown.
We sought to determine the use of IE prophylaxis by
surveying patients who recently underwent elective,
outpatient transthoracic echocardiography (TTE) and
correlating echocardiographic data with clinical and
prophylaxis data.
METHODS
Study
Population
Eligible subjects included all 308 patients who underwent
elective, outpatient TTE at the Beth Israel Deaconess
Medical Center's east campus in Boston, Mass, during
December 1997 (6 months after widespread dissemination of
the AHA guidelines7).
Patients were excluded if they did not speak English
(n=10), did not have a forwarding address (n=17), were
unable to complete the survey due to stroke or dementia
(n=4), or had died (n=3). The study was approved by the
hospital's committee on clinical investigation, which
waived the requirement for written informed consent.
Survey Data
To allow for guideline dissemination and physician
follow-up, patients were contacted 6 to 9 months
following their index TTE. Over a 3-month period
(June-August 1998), subjects were contacted to complete a
brief survey. Eligible patients received 2 US Postal
mailings and 3 telephone calls before being considered
nonrespondents.
TTE Data
Transthoracic echocardiography reports were obtained from
medical records. Based on AHA recommendations,7
patients were classified into 3 categories: (1) high
risk, which included history of prosthetic heart valve,
prior IE, cyanotic congenital heart disease, and
surgically constructed systemic pulmonary shunt or
conduit; (2) moderate risk, which included other congenital
malformation, acquired valvular dysfunction, hypertrophic
cardiomyopathy, and mitral valve prolapse with mitral
regurgitation and/or thickened leaflets; (3) negligible
risk, which included isolated secundum atrial septal
defects, mitral valve prolapse without valvular
regurgitation, pacemaker or defibrillator implantation,
physiologic or functional murmurs with normal valve, or
absence of high- or moderate-risk characteristics. For
this study, we used a definition of acquired valvular
dysfunction based on the US Food and Drug
Administration recommendations for significant valvular
abnormalities17
and included patients with valvular stenosis, at least
mild aortic regurgitation, at least moderate mitral or
tricuspid, regurgitation, and thickened mitral valves
with at least mild mitral regurgitation. None of the TTE
reports specifically addressed the need for IE
prophylaxis.
Statistical Analyses
We compared subjects who reported with those who did not
report being instructed to take IE prophylaxis, using the
t test and Fisher exact test as appropriate for
continuous and categorical variables. P<.05 was
considered significant and all tests were 2-tailed.
Analyses were performed using STATA version 5.0
statistical software (STATA Corp, College Station, Tex).
RESULTS
Of the 274
eligible subjects, 218 (80%) completed the survey and
comprised our analytic cohort. There were no significant
differences between respondents and nonrespondents in age,
sex, or echocardiographic results, including the presence
of structural valvular disease or prosthetic heart
valves. A total of 18 patients (8.2%) were categorized as
being at high risk for IE based on echocardiography, 90
(41.3%) as moderate risk, and 110 (50.5%) as negligible
risk. All patients who reported prior rheumatic fever
(n=9) or IE (n=13) had findings on TTE that classified
them as being at either moderate or high risk for IE.
Thus, according to AHA recommendations, 108 (49.5%) of
the study patients should have received IE
prophylaxis.
Recommendations for Prophylaxis
Of the 218 patients, 100 (45.9%) reported that they were
instructed by their physician to use IE prophylaxis prior
to dental work or other nonsterile procedures (Table
1). Of these 100 patients, 32.0% were first given
these instructions after their index TTE and 66.0%
reported that they were told to use prophylaxis 1 hour
prior to the procedure (in accordance with 1997 AHA
recommendations). For the group, primary care physicians
wrote the prescriptions for antibiotics for IE most
frequently (49%), followed by dentists (38%), and
cardiologists (13%).
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| Table. Baseline Characteristics*
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Of the 218 patients, 162 (74%) reported that their TTE
results were reviewed by a health care professional, most
commonly by the ordering physician (209 patients
[95.9%]). Of the 108 moderate- or high-risk patients, 80
(74.1%) reviewed their TTE results with a health care
professional, most frequently by the ordering physician
(77 of 80 patients). One hundred thirteen (51.8%) of the
218 respondents reported having undergone a prior TTE. Of
the 108 patients who met AHA recommendations for IE
prophylaxis, 71 (65.7%) reported that they were told by
their physicians to take prophylaxis prior to dental work
or other nonsterile procedures, including 88.9% of
high-risk patients. Among the 110 patients at negligible
risk, 29 (26.4%) reported that they had been instructed
to take IE prophylaxis. Of the 32 patients first
instructed to take prophylaxis after their index TTE, 11
patients (34.4%) were at negligible risk for IE.
Because the majority of patients eligible for IE prophylaxis
are at moderate risk and because this category contains
the least specific criteria (eg, acquired valvular
dysfunction), we further examined the echocardiographic
data of this subgroup. Thirty-four percent of patients
with thickened mitral leaflets and mild or higher mitral
regurgitation and 44.0% of patients with mild or higher
aortic regurgitation reported that they were not told to
take prophylaxis. Additionally, because the decision to
recommend IE prophylaxis for the 113 patients who had
undergone prior TTE may have been based on data obtained
from that prior TTE, we reviewed the results of the 61
patients (54.0%) who had undergone the prior TTE at our
institution. There was very high (60/61) concordance
between the 2 studies, with only 1 patient (1.6%)
changing risk categories based on echocardiographic data
(from being considered at negligible risk following prior
TTE results to moderate risk following the index TTE
results).
Compared with patients who were not told to take IE
prophylaxis, patients instructed to take prophylaxis were
significantly more likely to have had a prior TTE,
rheumatic fever, prior valvular surgery, endocarditis,
heart murmur, or TTE evidence of valvular disease,
including regurgitation or stenosis (Table
1).
Use of Prophylaxis
Sixty-eight of the 100 patients who reported being
instructed to take IE prophylaxis visited their dentist
subsequent to the index TTE in December 1997. Of these
patients, 9 (13.2%, 7 at moderate and 2 at negligible
risk) failed to take IE prophylaxis, despite their being
aware of their physicians' suggestion that they take
it.
COMMENT
The updated
1997 AHA recommendations were intended to improve
physician and patient compliance by clarifying which
patients are at risk for IE and simplifying the
antibiotic dosing regimen.7
Comparison of our study results with historical data12,
18-20
suggests that this goal has been accomplished, especially
with respect to patient compliance.11
However, our results indicate that there remains room for
improvement, with substantial underuse of prophylaxis for
moderate-risk patients and overuse of prophylaxis for
negligible-risk patients.
Studies that predated the 1997 AHA recommendations reported
poor compliance with guidelines for IE prophylaxis. In
patients with TTE evidence of mitral valve prolapse and
mitral regurgitation, only 29% to 66% of patients
received prophylaxis in accordance with contemporary
guidelines.12,
18-20
In a study of patients with cardiac lesions predisposing
to endocarditis, 70% of patients received advice on
prophylaxis from their physician, but only 22% actually
took prophylaxis as suggested.11
Similarly, in patients who underwent a nonsterile
procedure, only 25% of patients with known structural
heart disease took prophylaxis prior to that
procedure.21-22
The reasons for noncompliance with established guidelines
are numerous and likely related to both patient- and
physician-specific factors.23-25
Studies questioning the effectiveness of IE prophylaxis,8-10
unfamiliarity with guidelines,13-16,23
patient preferences, and noncompliance11
may result in the underuse of prophylaxis. Our findings
that nearly 40% of moderate-risk patients were not
instructed to take prophylaxis may reflect uncertainty about
the criteria that define this category. Although we used
criteria published by the US Food and Drug Administration
to define acquired valvular disease,17
it is possible that physicians are unfamiliar or may
disagree with these criteria or with the recommendations.
Nevertheless, physicians must decide whether to recommend
prophylaxis for their patients, and our data highlight
the need for further clarification of the criteria used
to define the moderate-risk category.
Conversely, physicians may unnecessarily recommend IE
prophylaxis based solely on physical examination findings
(eg, click and murmur), being unaware that the AHA
recommendations were updated to include echocardiographic
criteria for IE risk. Additionally, although our data
suggest a high concordance between prior echocardiographic
studies and the index TTE, physicians may have been
influenced by findings from prior TTE studies. Moreover,
even if physicians interpret and apply the AHA
recommendations appropriately, difficulties implementing
the recommendations may affect our measure of compliance.
For example, although clinical data were available via our
institution's computerized medical record, physicians may
have had difficulty accessing the TTE report or
communicating their recommendations to their patients or
other health care professionals.
There are several limitations to our study. First, there may
be reasons to recommend IE prophylaxis based on a medical
history beyond that of prior endocarditis or rheumatic
heart disease, the data that were obtained from the
patient survey. With no clear consensus from the
literature, physicians may recommend IE prophylaxis for
patients with a history of rheumatic fever or a murmur on
auscultation but without echocardiographic abnormalities.
Second, our study consists of patients referred to an
urban, university-affiliated medical center; therefore,
our results may not be generalizable to other
populations. Third, because we asked patients rather than
physicians about what physicians had recommended, it is
possible that some patients did not recall their
physicians' recommendations. Finally, we chose patient-reported
use of IE prophylaxis as our outcome, rather than pill
counts or prescriptions filled, recognizing that both
patient- and physician-related factors ultimately affect
our estimate of compliance. However, because much of the
initiative to take IE prophylaxis depends on the patient,
we believe that patient reported prophylaxis use is an
appropriate and clinically relevant measure.
In conclusion, the majority of patients receive IE
prophylaxis in accordance with current AHA
recommendations, although there may be substantial
underuse among patients with moderate risk and overuse
among patients with negligible risk. Further clarification
of specific at-risk categories, particularly those with
acquired valvular dysfunction, as well as continued
physician and patient education,11-12,18-20
may lead to improved compliance with the current AHA
recommendations.
AUTHOR INFORMATION
Corresponding Author and Reprints: Warren J.
Manning, MD, Cardiovascular Division, Beth Israel
Deaconess Medical Center, 330 Brook-line Ave, Boston, MA
02215 (e-mail: wmanning@caregroup.harvard.edu).
Author Affiliations: The Center for Best Healthcare
Practices (Dr Seto), The Queen's Medical Center and the Department
of Medicine, Divisions of Cardiology (Dr Seto) and Clinical
Epidemiology (Drs Seto and Taira), John A. Bums School of Medicine,
University of Hawaii; and Hawaii Medical Services Association,
Honolulu (Dr Tiara); and the Harvard-Thorndike Laboratory of the
Charles A. Dana Research Laboratory, Department of Medicine,
Cardiovascular Division, Beth Israel Deaconess Medical Center and
Harvard Medical School, Boston, Mass (Drs Douglas and Manning and Mr
Kwiatt).
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