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Clinical Practice/Controversy: Selection of Reperfusion Therapy and Transfer Strategies for Patients with ST-Elevation Myocardial Infarction
Case Presentation
A 57-year-old man presents to a community hospital without capability for primary percutaneous coronary intervention (PPCI) in the early morning (4 am ) with a 1.5-hour history of severe chest pain. His medical history is significant for hypertension. His wife called 911, and at the time of first medical contact by paramedics, he was hemodynamically stable. On cardiac examination, his jugular venous pressure is elevated to 7 cm above the sternal angle, and a third heart sound is noted. Respiratory examination revealed basilar crackles in the lower lung fields. His electrocardiogram (ECG), which was recorded within 10 minutes of arrival, shows an anterior ST-elevation myocardial infarction (STEMI) with a large territory of myocardium at risk without baseline Q waves. Emergency medical service (EMS) transfer times to a PCI-capable hospital for PPCI are estimated to be 60 minutes, notwithstanding the harsh winter conditions. Tenecteplase (TNK) is readily available to administer at the presenting hospital site.
Introduction
In the current era of evidence-based therapy, morbidity and mortality from STEMI have remarkably declined (see Chapter 2 ). This trend has been accompanied by infarct size reduction and improvement in left ventricular function, largely mediated by timely and effective reperfusion therapy (see Chapter 13 ). Furthermore, enhanced public education leading to earlier patient presentation, rapid emergency response from well-trained and equipped paramedical personnel, improved treatment in the field, and application of the best reperfusion strategy for the right patient, at the right time, in the right place—all integrated with streamlined triage—have enhanced the care of STEMI patients (see Chapter 5 ).
The appreciation that early risk assessment informs diagnosis and guides use of appropriate contemporary pharmacologic and/or invasive strategies are key components of optimal patient-based care (see Chapter 11 ). However, in many jurisdictions, the prevailing clinical belief is that PPCI is not only the preferred reperfusion strategy as supported by a class I guideline recommendation (provided PPCI can be delivered expeditiously in a skilled 24/7 facility), but that it should be the only strategy. Although timely PPCI can now generally be accomplished in those patients presenting to a PPCI center, the feasibility of achieving this goal in the majority of STEMI patients (i.e., those presenting to a non–PCI-capable center, such as featured in the previously described case) is much more challenging. Placing the large majority of STEMI patients in the context of their geographic location, access to timely and expert 24/7 PPCI, transfer logistics, and the total elapsed ischemic time (defined as the delay from symptom onset to effective reperfusion therapy) unmasks the stark reality of significant management challenges. Because the key modulator of STEMI outcome is total ischemic time, yet widespread evidence exists that this recommended temporal window is consistently exceeded in a large number of patients transferred for PPCI, alternate strategies need to be explored. A pharmacoinvasive (PI) strategy has now emerged as a legitimate alternative.
Our aim in this chapter is to provide insights with regard to the selection of reperfusion strategies in STEMI patients who require transfer to a PCI-capable hospital. As first articulated in the 2004 American College of Cardiology Foundation (ACCF)/American Heart Association (AHA) STEMI guidelines, these insights align with the four key components of the recommended approach to STEMI, namely, evaluation of (1) baseline attributable risk from the STEMI, (2) the risk of fibrinolytic therapy, (3) the time from first medical contact, and (4) the time required to reliably achieve expert PPCI.
Elements that Influence Reperfusion Delay for Primary Percutaneous Coronary Intervention in Transfer Patients
Primary PCI performed expeditiously in a high-volume expertise center has excellent outcomes. However, patients without ready access to PCI sites are particularly sensitive to delays that may offset these clinical benefits ( Figure 14-1 ; see also Chapter 5 ).
Patient Delay
Despite global public education efforts, many patients still do not seek medical attention for approximately 1 to 2 hours following symptom presentation. A profile of those patients who are most likely to delay activation of health care service has emerged and indicates they are more likely to be older adults, women, have diabetes, be African American, or of lower socioeconomic status. Clinical trial data from nearly 6000 STEMI patients who underwent PPCI within 6 hours of symptom onset emphasized the growing importance of older adults; whereas only 17% of this cohort was aged older than 65 years, they accounted for 64% of the deaths. An additional issue relates to patient choice of transportation to a health care facility. Because at least 50% of patients do not use the EMS system, they self-present as “walk-ins” to the nearest emergency room and are subject to further delays in diagnostic recognition and therapy (see Figure 5-12). Results from the Acute Coronary Treatment and Intervention Outcomes Network–Get With The Guideline (ACTION-GWTG) registry (>37,000 patients) found that only 60% of patients with STEMI activated EMS. The self-transport patients were more likely to be younger, men, hemodynamically stable, and have less co-morbid conditions. Longer ischemic times and extended treatment delays were noted, subjecting these patients to adverse outcomes.
Prehospital System Delay
In patients who directly activate EMS, continued challenges exist regarding transport to PCI-capable hospitals. Efforts have been made to bypass non-PCI sites and proceed to regional STEMI referral centers; however, 80% of such patients still do not achieve PPCI within 90 minutes (see Chapter 5 ). Despite major national efforts to reduce treatment times for PPCI, an analysis of more than 12,000 STEMI patients in the ACTION-GWTG registry (including patients from the “Mission: Lifeline” program [2008 to 2011]) found emergency department bypass occurred infrequently (10.5%) and occurred primarily during usual working hours only. Shorter first medical contact to device times were noted in patients who bypassed the emergency department, but these shorter times were associated with marginal improvements in adjusted in-hospital mortality (odds ratio [OR], 0.69; 95% confidence interval [CI], 0.45 to 1.03; P = .07).
In a key observational registry of 6209 Danish patients with STEMI transported by EMS for PPCI (35% who were transferred prehospital direct to a PCI center, with the remaining patients transferred from a non–PCI-capable hospital), long-term mortality (median 3.4 years, interquartile range [IQR], 1.8 to 5.2) increased with system delays (see Figure 5-9 ). Hence, the impact of total ischemic time is critically important and prognostically relevant as represented by the system delay (i.e., first medical contact to procedure) when considering transfer for PPCI. These data are especially noteworthy because (1) they demonstrate the inability to provide timely PPCI for most of the patients in the small country of Denmark, where drive times are short and PPCI facilities are abundant; (2) Denmark has substantial experience in conducting trials of transfer strategies that strongly influenced the movement towards PPCI; and (3) short-term mortality (in-hospital, 30 day, or even 1 year) is a blunt instrument to assess the longer term implications of delayed reperfusion. This issue is explored further in the section on Future Perspectives.
Interhospital System Delay
In the United States, most STEMI patients do not present to a PCI-capable site because the majority (approximately 80%) of health care institutions across the country are community hospitals without PPCI capability. For those patients who self-present to a non–PCI-capable facility and who require transfer, door-to-balloon times remain well above the targeted recommendation (transfer door to balloon ≤90 minutes) to improve timely access to care (7.6% in 2007 to 18.7% in 2009). Using the National Cardiovascular Data Registry (NCDR)-CathPCI Registry data between 2005 and 2007, Wang and colleagues assessed more than 115,000 STEMI patients who underwent PPCI at 790 hospitals across the United States. Of these, 25% of patients presented to non-PCI hospitals. Treatment of STEMI patients who had to be transferred significantly exceeded the guideline limits, with longer median door-to-balloon times than those who presented directly to PPCI centers (median 149 minutes vs. 79 minutes). Only 10% of transfer patients achieved a door-to-balloon time within 90 minutes of presentation. The ACTION Registry–GWTG reviewed more than 20,000 fibrinolysis-eligible STEMI patients who presented to a non–PCI-capable center with interhospital drive times of 30 to 120 minutes. Of these, most patients (70.5%) were transferred to a PCI-capable facility for PPCI. Disappointingly, only 51.3% were able to achieve ACC/AHA guideline-recommended first medical contact to reperfusion time within 120 minutes. Figure 14-2 highlights the proportion of patients who achieved successful mechanical reperfusion times, stratified according to drive times for transfer. Of note, only 52.7% of patients with a drive time longer than 60 minutes received fibrinolysis (see Figure 14-2 ). Hence, this persistent delay in achieving timely PPCI in those patients transferred from other institutions is still unacceptably high and does not meet current guideline metrics for STEMI.
Door-in-Door-out Time
Because of the delays that occur at the referral site (i.e., awaiting transport and emergency department delay), increased efforts have been initiated to reduce the delay between arrival to a non-PCI hospital and transfer to a PCI facility. Termed as door-in-door-out (DIDO) time, the 2008 ACC/AHA Clinical Performance Measures for Acute Myocardial Infarction recommended a DIDO time of less than 30 minutes. This quality metric was evaluated in nearly 15,000 STEMI patients who participated in the NCDR ACTION-GWTG registry who were initially seen in a non–PCI-capable hospital and subsequently transferred. The median DIDO was 68 minutes (IQR 43 to 120 minutes), with a DIDO time of ≤30 minutes achieved in only 11% of patients (see Figure 5-10 ). Predictors of longer DIDO times included older age, female gender, off-hour presentation, and non-EMS arrival to the referring hospital.
Mode of Transfer
Transfer times are also dependent on geographic constraints. Even in a well-developed STEMI transfer system of care, first door-to-device (D2D) times of 90 to 120 minutes can only be achieved for those hospitals located within a 30-minute transfer drive time (median D2D time of 93 minutes for drive times ≤30 minutes, 117 minutes for drive times of 31 to 45 minutes, and 121 minutes for drive times >45 minutes). Air transport has been explored to help expedite transport of STEMI patients, but without consistent success. In a study of 140 patients transported from 16 hospitals by helicopter service within a 150-mile radius to 6 PCI-capable centers in Cincinnati, Ohio for PPCI, 111 ultimately underwent PCI, with 97% of cases exceeding a D2D time of 90 minutes (median 131 minutes). Compared with ground transport, helicopter transport delayed D2D times irrespective of the distance-associated transfer drive time (helicopter transfer median D2D time 125 minutes for drive times of 31 to 45 minutes and 138 minutes for drive times >45 minutes).
Primary Percutaneous Coronary Intervention Center Logistics Delay
Even if rapid transfer of patients to a PPCI-capable facility can be achieved, obstacles to delivering timely PPCI still exist. In an observational study of approximately 83,000 STEMI patients in the NCDR CathPCI Registry (2009 to 2011), delays to PPCI occurred in 14.7% of patients because of informed consent, concerns about obtaining vascular access, and difficulties crossing the infarct-related artery. Not surprisingly, the in-hospital mortality was substantially higher in patients with a delay compared with patients without a PPCI center logistics delay even after adjustment for baseline risk (15.1% vs. 2.5%; P <.01). This observation reinforces the importance of the skill set developed in a high-volume experienced PPCI center and constitutes a cautionary reminder about the propensity to build low-volume PPCI centers in areas already well served by such facilities. Strategies to develop systems to minimize such delays in an ideal STEMI system are discussed in detail in Chapter 5 .
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