Bang for the Buck: Intensifying the Focus on Cardiogenic Shock in Order to Reduce Mortality in Acute Coronary Syndromes

Care for patients with acute cardiac disease has been characterized by a vigorous focus on patients with acute ST segment elevation myocardial infarction (STEMI). As a result, multiple organizations have motivated health care systems and regional health authorities to make drastic changes that have reduced the time between patient presentation and reperfusion therapy (largely primary PCI), with the effect that patient-specific mortality has been reduced, even though population mortality has changed little¹. During this same period, the proportion of patients with myocardial infarction presenting with cardiogenic shock (CS) has increased from 6% to 10%², while the frequency of CS in patients with out of hospital cardiac arrest is approximately 50%. Conversely about 80% of patients with CS initially present with acute coronary syndromes³. These cases account for most of the deaths among patients presenting with myocardial infarction. Interestingly, most patients who survive the acute phase of CS are alive one to six years later^4,5. The Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock (SHOCK) trial established that reperfusion reduced mortality in patients with CS complicating myocardial infarction⁶. Little progress has been made since then, however. Despite improved understanding of the pathophysiology of CS, mortality remains high – about 39% for patients < 75 years and 55% for those aged 75 or older². Importantly, the relatively easy to implement strategies such as intraaortic balloon counterpulsation and novel pharmacologic approaches alone have not been successful in reducing shock mortality^7,8. Data have accumulated from reports of more advanced mechanical support devices such as the Impella, suggesting strongly that early implementation of mechanical support may be associated with lower mortality⁹. These data and other aspects of pharmacologic and mechanical management of CS are reviewed in great detail in the current AHA/ASA Scientific Statement on Contemporary Management of Cardiogenic Shock¹⁰.

In addition, the statement makes a number of critically important points that are bound to attract attention. They are largely based on the assumption that earlier treatment and more closely coordinated care of patients with CS is likely to lead to the next round of mortality reduction.

1. Early recognition of CS, including its less common presentations, is essential. The classical “wet and cold” (high filling pressure with peripheral vasoconstriction) picture is most common, but is not the only presentation of CS. Practitioners should be aware of “cold and dry” and normotensive presentations as well as right ventricular shock. Another important point is that although the classic teaching has been that mechanical complications occur late in the course of myocardial infarction, ample evidence now demonstrates that they frequently occur early after presentation₁₁.
2. Following recognition, the application of various scoring systems, such as APACHE III may be useful in selecting patients for more advanced therapeutic strategies.
3. There is a graded relationship between center experience at managing CS and mortality of the syndrome, likely as a result of more frequent use of established therapies, availability of high volume PCI operators, and multidisciplinary management teams. After adjustment for baseline risk, CS mortality was reported to be approximately 27% lower when patients were managed in the highest compared with the lowest volume centers, even though the former group constituted only 3.2% of the hospitals studied¹².
4. Developing systems of care based on regional designation as specialized receiving centers has been successful in other serious illnesses whose outcomes are dependent on time to treatment, such as stroke, trauma, and out of hospital cardiac arrest. Such systems have also shorted reperfusion times for patients with STEMI. Early experience among surgical patients with post cardiotomy shock and in a French ambulance-based pilot trial¹³ has suggested that developing a similar system for shock may be useful. Such a system would necessarily be more complex than that used for STEMI as the number of centers would necessarily be smaller. The Statement proposes establishing specialized receiving centers, which would meet the following criteria:
1. Minimal Level 1 organizational standards as proposed in the 2012 AHA Scientific Statement Evolution of Critical Care Cardiology. Such standards include the capability of managing “all cardiovascular conditions and major noncardiovascular comorbid conditions¹⁴.
2. Multidisciplinary “Shock teams” consisting of cardiac surgeons, interventional cardiologists, advanced heart failure specialists, critical care specialists, transplantation teams, and other health professionals. This team must be able to select and implant appropriate circulatory support devices, perform complex revascularizations of coronary arteries that have not been addressed during primary PCI, manage the complex renal, respiratory and metabolic derangements that accompany CS and in many circumstances, perform triage to palliative care.
3. Dedicated ICUs for patients with CS, which would be distinct from standard cardiac care units. Obviously developing such units would vary from hospital to hospital as dictated by available space and other logistic considerations.
4. Availability 24 hours, 7 days a week with 30 minute response times to incoming phone calls
5. In certain situations, mobile CS support teams that are able to stabilize and transport patients to Level 1 facilities.
5. Extension of the AHA Mission Lifeline to include support for these recommendations. In the decade since its implementation, this initiative has demonstrated major success in promoting the proportion of patients with STEMI who receive timely reperfusion therapy.

These recommendations are perfectly logical and are fairly well, although imperfectly, supported by the existing evidence. It is important to recognize, though, that they will require fundamental changes in the way business is currently conducted. First, the recommendations would establish a three-tier system of managing CS, consisting of a primary hospital, a local PCI-capable hospital, and a designated “hub” institution. Currently, according to NCDR data, fewer than one out of four cases of CS are managed at high volume hospitals¹⁵. Revascularization will still need to be performed in the most rapid fashion possible. Once a primary PCI is performed, emphasis would shift to a formal assessment of the patient’s risk of developing CS and making plans for immediate transfer from “spoke” to “hub” hospitals when this risk is high. Unlike, the current approach, the third tier of care would become systematized, as the number of CS receiving hospitals would be considerably smaller due to the resources required to manage the 10% of infarctions in which CS develops. Adopting this mechanism would likely prove contentious as it would require alterations in referral patterns and would probably spur competition for designation as hub centers. Second, careful examination of the financial implications of this strategy will be required, as management of patients in CS is extremely resource-intensive and is likely to pose a burden on the spoke hospitals. Finally, as proposed in the statement alteration in the current public reporting system so that receiving centers are not penalized for managing these patients and do not become risk-averse. Precedent for this approach exists in some states in the US.

The hypothesis is clear – that a systematic approach to CS will reduce morbidity and mortality of the syndrome. The proof isn’t so clear – will such a strategy really work, and what will its downstream effects be? Surely a series of pilot studies is in order.