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| Journal of the New Zealand Medical Association,
19-February-2010, Vol 123 No 1309
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Primary percutaneous intervention has become an increasingly
common strategy for the management of ST elevation MI. Metanalysis of 23 STEMI
trials9 has confirmed the benefits of PPCI,
reducing 30-day mortality, reinfarction and stroke. However, increased delay
before such intervention has been associated with poorer
outcomes.11–14,15 Both US and European
guidelines16,17 emphasise the importance of
prompt (<90 min) performance of PPCI, by skilled teams in high volume
centres.
The D2B Alliance, an association of professional bodies
interested in improving D2B times (i.e. the time from arrival in hospital to
first balloon inflation, http://www.d2balliance.com/Menu/D2BImplementationManual)
in the US They found that six strategies18 were
associated with significantly reduced D2B times (Table 1).
Waikato Hospital is in North Island New Zealand, with a
local population of approximately 200,000, around 20% Maori. A PPCI policy
(described below) was established a decade ago for all high-risk
patients presenting to Waikato Hospital with STEMI. It allows for testing of the
strategies of the D2B Alliance in a unit with smaller PPCI volumes, volumes
similar however to many units worldwide.
In-house audit of the existing admission procedure was
compared to the successful strategies outlined by the D2B alliance. Following
multidisciplinary discussions, changes in the admission process were instituted
and the results audited, comparing D2B times in the 6-month periods before and
after the changes were instituted.
Figure 1. Example feedback email used in
Waikato. Timing data allow staff members feedback for patients they have dealt
with personally
 Table 1. Strategies associated with reduced D2B
times. ED=emergency department, cath lab=cardiac catheterisation laboratory.
Strategies in bold were adopted wholly or partly during the study period. Data
from Bradley et al18
A D2B team was formed which took
responsibility for the new admission process. In-house teaching sessions were
arranged and feedback encouraged. A STEMI admission algorithm was prominently
displayed in ED and cath lab.
MethodsAudit of the current admission procedure identified to
what extent strategies recommended by the D2B Alliance were already in place or
where these strategies might be introduced. Ethical approval was not required as
the audit was performed as part of service improvement and review.
Study population—Changes were
made in February 2007, with data collection for 6 months before and after this
point. PPCI patients constituted a higher-risk subgroup of STEMI patients. They
were defined as patients presenting with anterior ST elevation, new left bundle
branch block or inferior and lateral myocardial infarcts with reciprocal changes
or right ventricular involvement. Any patients with hemodynamic instability,
including cardiogenic shock were included. All patients with contraindications
to thrombolysis were treated with PPCI.
The lower-risk remaining patients were given
thrombolysis.
Patients already in the hospital were not included in
the analysis, nor were patients transferred from other centres.
Changes instituted—After initial
audit and multidisciplinary discussion, three main changes (see Table 1) were
made to the admission process A target of achieving a door-to-balloon time of
<90 minutes for >75% of non-transfer PPCI patients was used to judge the
effect of these changes.
Definitions—D2B time = time from
hospital arrival to establishment of reperfusion by an interventional device.
ED=Emergency department
PPCI=Primary Percutaneous coronary intervention by
angioplasty, with or without stent, for STEMI.
Data collection and
analysis—Treatment times were recorded for all PPCI patients.
These were the time of symptom onset, time of arrival in ED, time of call to
cardiologist, time of cath lab arrival and time of first balloon inflation. This
allowed calculation of the D2B time, the primary endpoint of the study, as well
as analysis of the relative contribution of the various steps in admission to
the overall delay. The proportion of patients with D2B time <90 minutes and
median D2B time were calculated.
Statistical
methods—Non-parametric values were compared with the Wilcoxon
rank-sum test (for two samples) using StatPlus Professional 2007 software
(AnalystSoft). A Chi-squared (Pearson’s) test (http://www.quantitativeskills.com/sisa/)
was used to test for differences in baseline demographics and for 30-day
mortality before and after admission process was changed, although the study was
not powered for mortality as an endpoint. A value of P<0.05 was considered
significant.
Results:Baseline demographics between the cohorts were broadly
similar, although a higher incidence of smoking was seen in the earlier group
(see Table 2). None of the patients were undergoing repeat procedures, making
the two groups independent samples.
Effect of changed admission process on D2B
times—72 patients were triaged for treatment with PPCI during the
study period. Of these, 38/72 patients’ data were included in the study,
12 pre-change, 26 post-change. The remainder were excluded because the patient
was already in the hospital at the time of infarction (16/34), was an
inter-hospital transfers (3/34) or did not proceed to PCI (because of
non-occlusive coronary disease (7/34), surgical disease (1/34) and subsequent
diagnoses other than AMI (7/34)).
Table 2. Baseline demographic findings between
patients studied before the changed admission procedure (Pre) and after
(Post)
A trend towards shorter D2B times (74.5min vs. 59 min,
p=0.09) was seen (Figure 2), due to improved (50 min vs. 35 min, p=0.02) median
admission to cath lab arrival times. Prior to the changed admission process,
63.6% of patients had a D2B time <90 min. Subsequently 88.5% of patients were
treated <90 min. Other component parts of the total D2B time were not
different between the two groups. Two patients in each group died within 30 days
of the index procedure.
Figure 2. Effect of changing PPCI admission
process within Waikato Hospital.
 Door to balloon time (D2B) shows a trend (*74.5 min vs.
59 min, p=0.09) to improvement from the six month period “Pre”
change to the six month period “Post” change. This was due to a
statistically significant improvement (†50 min vs. 35 min, p=0.02) in the
time from admission to emergency department to the time of arrival in the
catheterisation laboratory, which appeared to be mainly occurring in the period
after initial referral to a cardiologist (‡30 vs 15 min, p=0.001).
DiscussionOverall changes to the admission process resulted in a
15-minute reduction in D2B times. It was not possible to determine the relative
contribution the individual changes had on this improvement. The time from
hospital arrival to cardiologist being called was not reduced, yet the time from
hospital arrival to cath lab arrival was. This suggests that preparation for
cath lab was minimised and that the physical journey to cath lab was being
accelerated. On some occasions, ED physicians pushed patients to cath lab
themselves. Other unquantifiable variables, such as the immediate availability
of ED physicians to deal with PPCI patients (rather than other emergencies in
ED) may have played a part.
Pain to balloon times in Waikato were not different between
the two groups, despite the reduction in D2B times. This reflects the relatively
small contribution triage (hospital arrival to cath lab) times have on overall
treatment delays. Patient presentation delays comprise the major component of
this overall. Only community education is likely to improve this.
Calling the cardiologist on call directly to access the cath
lab removed initial cardiology registrar assessment, although they still came to
assess the patient in preparation for cath lab. Further reduction in D2B times
might be anticipated if the ED physician or nurse, were to call the cath lab
team without discussion with a cardiologist,.
18 A selective PPCI policy makes this more
difficult since the decision to call in the cath lab team is made on a
case-by-case basis, by the senior cardiology clinician.
The test call was changed to become weekly after feedback
from switchboard operators.
Staff in ED were generally very positive to the feedback
innovation although it is not possible to know what proportion of feedback
emails were actually read. The feedback reports were used in departmental
teaching sessions.
Prehospital activation of the cath lab with telemetered ECGs
was not introduced in this study as it would have required additional IT
infrastructure and training. No requirement was made for the on-call
cardiologist to be resident. In Waikato, with around 70 PPCI patients per year,
this was felt to be unreasonable, with major resource implications.
A selective policy for PPCI, as in Waikato, attempts to
target higher-risk patients with the most to gain from PPCI,. The Zwolle trial
20 showed that non-anterior MIs had similar
mortality with either PPCI or thrombolysis. Retrospective analysis of the
DANAMI-2 (Danish Multicentre Randomized Study on Fibrinolytic Therapy Versus
Acute Coronary Angioplasty in Acute Myocardial Infarction) suggested that
patients without hemodynamic upset or pulmonary congestion had no benefit in
mortality or composite endpoints with PPCI over thrombolysis.
21 It is unknown whether the selective policy
used in Waikato may have influenced D2B times.
Study limitations—Study numbers are
small, but are similar to the primary angioplasty workload seen in a year in
many centres worldwide. The Wilcoxon rank sum test may be less accurate when
sample sizes are less than 20. These small numbers mean the results have to be
interpreted with some caution. The influence of an ongoing audit may have
altered behaviour of staff members to accelerate the admission process
independent of the altered admission algorithm. It has not been established that
a reduction in D2B times results in reduced adverse events. This would require a
much larger study, powered for a mortality difference. Accelerating the D2B
times may risk increasing the number of patients taken to cath lab
inappropriately, although this was not observed during the study. The
generalisability of these findings to units with a non-selective PPCI approach
may be limited.
ConclusionsThe benefits of PPCI may be reduced by long delays. Part of
this delay, which clinicians have some ability to reduce, is the D2B time.
This study has shown that change involving several hospital
departments can be successfully initiated. This approach allows the adoption of
evidence-based, simple strategies resulting in significant reductions in the
time spent prior to cath lab arrival. This requires commitment and organisation,
but not greatly increased resources.
Competing interests: None known.
Author information: Neil Swanson,
Cardiologist, Cardiology Department, James Cook University Hospital,
Middlesbrough, United Kingdom; Christopher Nunn, Cardiologist, Cardiology
Department, Waikato Hospital, Hamilton; Steve Holmes, senior audit
administrator, Cardiology Department, Waikato Hospital, Hamilton; Gerry Devlin,
Cardiologist, Cardiology Department, Waikato
Hospital, Hamilton.
Acknowledgements: The authors acknowledge M
Burningham and K Golding for their roles in data collection.
Correspondence: Neil Swanson, Cardiology
Department, James Cook University Hospital, Middlesborough, TS4 3BW, United
Kingdom. Fax: +44 1642 854190; email: neil.swanson@stees.nhs.uk
References:
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