Advertisement
Advertisement
January/February 2010
Managing Transport for Primary PCI
A review of the literature and strategies to optimize patient outcomes.
Primary percutaneous coronary intervention (PCI) is the preferred reperfusion strategy for ST-segment elevation myocardial infarction (STEMI). In a meta-analysis of 23 randomized trials including 7,739 patients, primary PCI, as compared with fibrinolytic therapy, was associated with a 25% reduction in death (7% vs 9.3%; P < .0001), and a 53% reduction in total stroke (1% vs 2%; P = .0004).1 Additional benefits include greater myocardial salvage, reduced recurrent ischemia, and earlier hospital discharge. Unfortunately, less than 25% of hospitals in the United States have primary PCI capability.2 Nevertheless, 80% of the United States population lives within 60 minutes of a PCI facility, and 95% lives within 90 minutes, making primary PCI a legitimate reperfusion strategy for the majority of adults in the United States.3 The challenge is to provide timely reperfusion for these patients.
Several models have been envisioned in order to realize this objective. One is the direct emergency medical service (EMS) transport of STEMI patients to primary PCI centers, bypassing non-PCI hospitals. This is an attractive strategy to reduce the time to first balloon inflation. There are considerable barriers to achieving this in the United States, including fragmented EMS systems, laws in some states prohibiting EMS bypass of hospitals, a lack of local resources, and economic considerations of non-PCI hospitals. Another model, and the focus of this article, is the organized and efficient transfer of STEMI patients from non-PCI hospitals to PCI centers. Among the goals of the American Heart Association's (AHA) Mission: Lifeline is to facilitate the development of these systems of care.
TIME CONSIDERATIONS AND
DELAY IN REPERFUSION
Although primary PCI has clearly been shown to reduce
the risk of death, reinfarction, and stroke compared with
fibrinolytic therapy, these results were achieved in nontransfer
trials, except for one outlier, with door-to-balloon
times of 62 to 114 minutes. The major criticism of transfer
is that delays in treatment times may negate the benefit
of primary PCI, and in fact, benefit may tilt in favor of fibrinolytic
therapy. It has been shown that longer door-toballoon
times are associated with increased mortality
rates. Analysis of 29,222 patients in the National Registry
of Myocardial Infarction (NRMI)3,4 showed that the inhospital
mortality rates were 3%, 4.2%, 5.7%, and 7.4% for
door-to-balloon times of ≤ 90 minutes, 91 to 120 minutes,
121 to 150 minutes, and > 150 minutes, respectively
(P < .01).4 Other studies have shown similar gradations for
mortality in patients presenting early, but not in patients
presenting > 2 to 3 hours from symptom onset.5,6
Although fibrinolytic therapy can abort approximately 25% of MIs if administered < 1 hour from symptom onset, the efficacy of fibrinolytic therapy appears to diminish significantly with increasing time.7 A metaanalysis of 50,246 patients showed that the number of lives saved per 1,000 patients treated was 65, 37, 26, 29, and 18 for ischemic times of < 1 hour, 1 to 2 hours, 2 to 3 hours, 3 to 6 hours, and 6 to 12 hours, respectively.8 After 6 hours, marginal benefit is seen in terms of infarct size and mortality. This is likely due to resistance of organized thrombus to dissolution by fibrinolytics, as well as transformation of bland infarcts into hemorrhagic infarcts, resulting in increased mechanical complications. The time-dependent attenuation of fibrinolytic benefit may not apply as stringently to primary PCI.
An analysis including 192,509 STEMI patients in the NRMI corroborated the findings of other studies that for both primary PCI and fibrinolytic therapy, mortality increases as time to treatment increases. However, primary PCI was associated with lower mortality rates until an incremental treatment delay of > 114 minutes occurred.9 Acceptable PCI-related delay, however, was modified by age, infarct location, and symptom duration. For example, the threshold was 40 minutes for patients > 65 years of age with an anterior STEMI presenting < 120 minutes from symptom onset but 179 minutes for patients > 65 years of age with a nonanterior STEMI presenting > 120 minutes from symptom onset. In a meta-analysis of 10 randomized trials, the mortality benefit of primary PCI over fibrinolytic therapy was greatest in patients presenting > 4 hours from symptom onset (4.7% vs 12.1%).10
These studies suggest that increased treatment times are clearly associated with greater mortality rates. However, the relationship of time from symptom onset to treatment and mortality is weaker with primary PCI than with fibrinolytic therapy, particularly in patients presenting > 2 to 4 hours from symptom onset. Conceptually, this may have implications for the selection of the reperfusion strategy.
TRANSFER FOR PRIMARY PCI: RANDOMIZED
TRIAL DATA
The transfer of STEMI patients for primary PCI has
been evaluated in eight randomized trials.11-18 A total of
4,155 patients were randomized to transfer for primary
PCI versus fibrinolytic therapy. The incremental PCI-related
delays ranged from 48 to 103 minutes, and the first
door-to-balloon times ranged from 85 to 174 minutes.
Despite these treatment delays, transfer for primary PCI
was associated with a 20% nonsignificant reduction in
mortality (5.9% vs 7.4%; P = .06), a 67% reduction in reinfarction
(1.8% vs 4.8%; P < .0001), and a 70% reduction in
stroke (0.6% vs 1.9%; P = .0001) (Table 1).19
Not only are the results promising, but the risk of transfer is low. The risk of death was 0% to 0.005%; ventricular arrhythmias, 0% to 0.14%; and advanced heart block, 0% to 0.02%.11-18 A similarly low risk for transfer was seen in a large registry of transfer including 1,048 patients.20 There were no deaths during transfer, but 0.7% of patients required endotracheal intubation, and 2% were successfully resuscitated from cardiac arrest.
PATIENT SELECTION FOR TRANSFER
The current American College of Cardiology (ACC)/AHA
guidelines recommend an invasive strategy for (1) expected
< 3 hours from symptom onset, (2) patients presenting
> 3 hours from symptom onset, (3) patients with cardiogenic
shock and severe congestive heart failure, and (4)
patients with contraindications for fibrinolytic therapy.21
These patients should be considered for immediate transfer
for primary PCI. For patients presenting early and with longanticipated
door-to-balloon times, fibrinolytic therapy is
preferred. This may be particularly true for high-risk patients
presenting < 1 to 2 hours from symptom onset. Based on
the results of CARESS-AMI and TRANSFER-AMI, the 2009
ACC/AHA Focused Update for STEMI recommends a pharmacoinvasive
strategy for high-risk patients in which
patients are transferred for routine PCI after fibrinolysis.22 This topic is covered by Dr. Michel R. Le May on page 57 of
this issue.
SYSTEMS OF CARE
A well-organized and coordinated system is essential to
the rapid and efficient transfer of patients in order to
minimize reperfusion time and maximize clinical outcomes.
Developing a system of care is paramount to all
successful transfer programs. Only dedicated, organized,
and coordinated regional systems with clear standard protocols
and processes can successfully orchestrate timely
patient transfers.
Unlike many European countries, only a handful of regions in the United States have developed integrated transfer systems. They tend to be organized into huband- spoke models where the hub is the PCI center and the spoke is the referring non-PCI hospital. Clear and well-established protocols are used to determine which patients are transferred for primary PCI and which are treated with fibrinolytic agents. The mechanics of triage and transport are also executed according to standardized protocols.
In accordance with ACC/AHA STEMI guidelines, all patients presenting with chest discomfort should have an electrocardiogram (ECG) obtained and interpreted by an emergency physician within 10 minutes of arrival.21 In patients who access EMS, prehospital ECG may expedite emergency department care. In some regions, prehospital ECG may trigger direct transport to a PCI center, bypassing non-PCI hospitals. In some instances, prehospital ECG may prompt initiation of prehospital fibrinolytics. Unfortunately, only a minority of EMS systems has prehospital ECG capability, and only half of all STEMI patients access EMS.
Once a STEMI is diagnosed, formal protocols should be used to determine which patients are treated with fibrinolytics and which are transferred to a PCI center. Standardorder sets should be used to initiate treatment. If transfer is decided upon, there should be a single designated contact number that the emergency physician calls to initiate transfer and activate the catheterization laboratory without the need to check on bed availability or confer with a cardiologist. For patients brought in by EMS with a prehospital ECG, it is prudent to keep them on the stretcher while they are triaged to minimize delays. Additionally, continuous intravenous infusions may increase delays and should be minimized. Pumps and tubing frequently need to be changed between the referring hospital, the ambulance, and the accepting hospital.
Upon arrival at the PCI hospital, the patient should bypass the emergency department and be taken directly to the catheterization laboratory. A “concierge” service is desirable, where a team member at the receiving hospital meets EMS and the patient at the door and escorts them directly to the catheterization laboratory. The preactivated team is then ready and waiting for the patient.
A robust quality assurance program is critical to continually improve systems for efficient patient triage and transfer, adherence to protocols and guidelines, and the seamless integration of EMS, the non-PCI emergency department, and the PCI center. Every stage across the continuum of care must be scrutinized to maximize efficiency and minimize delays.
Several regions in the United States have developed integrated STEMI transfer programs. The Minneapolis Heart Institute program accepted 1,048 STEMI patients from 30 non-PCI hospitals between 2003 and 2006.20 The median first door-to-balloon time was 95 minutes for patients transported < 60 miles (half-dose tenecteplase) and 120 minutes for patients transported 60 to 210 miles (full-dose tenecteplase). In-hospital mortality rates were very favorable at 4.2%. Although this trial did not address primary PCI, it demonstrates that large networks and refined systems can be established to transfer patients efficiently. The Mayo Clinic STEMI protocol involved 28 hospitals within 150 miles of the Mayo Clinic. Patients presenting < 3 hours from symptom onset were treated with fibrinolytics.23 One hundred five patients presenting to a non-PCI hospital with symptom duration > 3 hours were transferred for primary PCI. Median first door-to-balloon time was 116 minutes despite long transport times. This also illustrates that well-structured programs can effectively transfer patients long distances, and algorithms can be created to tailor reperfusion strategy according to simple patient and logistical factors.
The Reperfusion of Acute Myocardial Infarction in North Carolina Emergency Departments (RACE) study developed regionalized systems of care with protocols for primary PCI at PCI centers as well as strategies and protocols at non-PCI hospitals for either fibrinolytics or transfer to a PCI center. First door-to-balloon times were evaluated for transfer patients before and after the implementation of strategies to reduce transfer times.24 Among these strategies were prehospital ECG, keeping the patient on the ambulance stretcher while triaged in the emergency department, ECG obtained within 10 minutes of arrival to the emergency department, formal order sets for STEMI, a single call number to activate the catheterization team, and elimination of intravenous drips for transfer. The median first door-to-balloon time was reduced from 165 minutes to 128 minutes (P < .001). The RACE study demonstrates that implementing strategies to shorten transport time can reduce first door-to-balloon time. However, despite their integrated systems of care, all of these studies reported median door-toballoon times exceeding the ACC/AHA recommendations. Additional process improvements and refinements may further reduce first door-to-balloon times in transfer patients. However, realistic estimations of transport times for particular networks should be considered when deciding to transfer patients. Both clinical trial results and actual transport times for unique regional systems must be used to devise algorithms for triaging patients to transfer for primary PCI versus a pharmacoinvasive approach. These algorithms may be based on simple clinical characteristics and anticipated transfer times.
MEDICAL THERAPY
All transfer patients should be treated with aspirin and
unfractionated heparin. There are no clinical trial data to
support thienopyridine loading before transfer. However,
based on pharmacokinetics, it is reasonable to initiate
thienopyridine therapy early, particularly if clopidogrel is
used. There are no data that suggest up front glycoprotein
IIb/IIIa inhibition improves outcomes in primary PCI. In
the ON-TIME 2 trial, pretreatment with tirofiban did not
reduce death or recurrent MI.25 In FINESSE, the 90-day
mortality rates were 5.5% and 4.5% for the abciximab-facilitated
PCI group and primary PCI groups, respectively.26
Based on these studies, up front glycoprotein IIb/IIIa therapy
is not recommended to treat patients who are transferred
for primary PCI.22 Lastly, beta blockers may be initiated,
assuming there are no contraindications.
CONCLUSIONS
Despite many logistical complexities, transfer for primary
PCI has been shown to be feasible and safe. Despite
PCI-related delays of 48 to 103 minutes, a meta-analysis of
the eight randomized trials confirms the benefit of transfer
for primary PCI over fibrinolytics. Clearly, patients in cardiogenic
shock or with contraindications for fibrinolytics
should be transferred. Although more controversial, much
of the clinical trial data discussed support transfer of
STEMI patients for primary PCI if the expected door-toballoon
time is ≤ 90 minutes for patients presenting < 3
hours from symptom onset and for most patients presenting
> 3 hours from symptom onset. Establishing formal,
coordinated, regional systems of care is crucial in accomplishing
the goal of efficient transfer, and therefore, to
maximize the number of patients eligible for primary PCI.
The AHA's Mission: Lifeline initiative will facilitate the creation
of these systems and thereby increase access to
prompt percutaneous reperfusion.
George S. Hanzel, MD, FACC, FSCAI, is Director of Structural Heart Disease at William Beaumont Hospital in Royal Oak, Michigan. He has disclosed that he holds no financial interest in any product or manufacturer mentioned herein. Dr. Hanzel may be reached at (248) 898-4176; ghanzel@beaumont.edu.
Advertisement
Advertisement
