CARDIOVASCULAR JOURNAL OF AFRICA • Vol 21, No 2, March/April 2010
AFRICA
97
Cardiovascular Topics
Factors associated with mortality when chronic beta-
blocker therapy is withdrawn in the peri-operative period
in vascular surgical patients: a matched case–control
study
BRUCE M BICCARD
Summary
Background:
Withdrawal of chronic beta-blockade following
vascular surgery is associated with peri-operative mortality.
The aim of this study was to examine risk factors associated
with mortality in patients where chronic beta-blockade was
withdrawn.
Methods:
Two matched case–control studies were conducted,
one of patients withdrawn from beta-blockade who survived
and the other of patients who were maintained on beta-block-
ade and survived. Each case was matched with two controls.
Three potential risk factors were analysed: the increase in
heart rate postoperatively, the use of inotropes, and whether
withdrawal for the first three postoperative days was more
predictive than withdrawal for a single day. Multivariate
conditional logistic regression was conducted.
Results:
The only independent predictor of in-hospital mortal-
ity was a change in the mean daily heart rate of
≥
six beats
per minute from the day of surgery to the third postoperative
day, or death or discharge if this happened before the third
day (OR 13.7, 95% CI: 1.7–110,
p
=
0.014). The area under
the curve for the receiver operating characteristic curve was
0.787.
Conclusion:
Use of a postoperative heart rate threshold may
be clinically useful as an ‘early warning system’ in patients
withdrawn from chronic beta-blockade in the peri-operative
period.
Keywords:
mortality, cardiac, surgery vascular, pharmacology
beta-blockers
Submitted 22/7/09, accepted 13/10/09
Cardiovasc J Afr
2010;
21
: 97–102
A history of chronic beta-blockade has been associated with a
significantly increased incidence of peri-operative myocardial
infarction in non-cardiac surgical patients [odds ratio (OR) 2.14,
95% confidence interval (CI): 1.29–3.56].
1
Case series that have
documented withdrawal of chronic beta-blockade following
mixed vascular surgical procedures have reported extremely
poor outcomes; with an in-hospital mortality of 24 to 50%, an
early cardiovascular mortality of 29%, a peri-operative myocar-
dial infarction rate of 50% and a one-year mortality following
surgery of 38%.
2,3
A meta-analysis of these two studies shows
that the OR for mortality when chronic beta-blockade is with-
drawn in the peri-operative period in vascular surgical patients is
26.32, 95% CI: 8.95–77.44,
p
<
0.0001.
Despite the significantly increased risk of mortality, the
total number of cases reported is small (
n
=
29) and no attempt
has been made to identify risk factors associated with mortal-
ity in patients in whom chronic beta-blockade is withdrawn
in the peri-operative period. Chronic beta-blockade results in
beta-adrenergic receptor up-regulation and a lowering of the
ischaemic threshold,
1
with myocardial ischaemia evident at
lower myocardial oxygen demands. Withdrawal of chronic beta-
blockade in the peri-operative period and an associated increase
in heart rate therefore probably contributes to the increased
all-cause and cardiovascular mortality, secondary to myocardial
ischaemia. The relationship between postoperative heart rate and
chronic beta-blockade withdrawal as an independent predictor of
postoperative mortality following vascular surgery has recently
been confirmed.
4
The aim of this study was to examine clinically useful
predictors of mortality in patients withdrawn from chronic beta-
blockade in the peri-operative period. As it would be unethical
to investigate this problem prospectively, a case–control study
design was utilised.
Methods
Local ethical approval was granted by the Ethics Committee of
the Nelson R Mandela School of Medicine for this study. An
existing database of all vascular surgical patients over 39 years
of age admitted for both elective and emergency vascular surgery
at Inkosi Albert Luthuli Central Hospital between June 2003 and
June 2007 was used for this study. Only the most recent surgi-
cal procedure per patient is recorded in the database. Therefore
the mortality reported in this article represents the mortality per
patient and not per procedure. More recent data has not been
included as this is prospectively being collected for a Medical
Research Council-funded observational study.
Department of Anaesthetics, Nelson R Mandela School of
Medicine and Inkosi Albert Luthuli Central Hospital, Durban,
South Africa
BRUCE M BICCARD, MB ChB, FFARCSI, FCA (SA), MMed Sc,
