ABSTRACT & COMMENTARY
Inpatient STEMIs: Are They as Complicated as They Seem?
Jeffrey Zimmet, MD, PhD
Associate Professor of Medicine, University of California, San Francisco, Director, Cardiac Catheterization Laboratory, San Francisco VA Medical Center
Dr. Zimmet reports no financial relationships relevant to this field of study.
This article originally appeared in the February 2014 issue of Clinical Cardiology Alert. It was edited by Michael H. Crawford, MD, Professor of Medicine, Chief of Clinical Cardiology, University of California, San Francisco, and peer reviewed by Ethan Weiss, MD, Assistant Professor of Medicine, Division of Cardiology and CVRI, University of California, San Francisco. Dr. Crawford reports no financial relationships relevant to this field of study, and Dr. Weiss is a scientific advisory board member for Bionovo.
SOURCE: Garberich RF, et al. ST elevation myocardial infarction diagnosed after hospital admission. Circulation Jan 3, 2014. [Epub ahead of print.]
The link between time to reperfusion and mortality in ST-elevation myocardial infarction (STEMI) is well established, and has led to a national initiative to improve prehospital and hospital systems to speed recognition of STEMI and delivery of primary percutaneous coronary intervention (PCI). Much of the emphasis in the door-to-balloon initiative has focused on earlier identification of these patients by emergency medical services (EMS) in both the ambulance and emergency department (ED) settings. Pathways for STEMI recognition and activation of the cath lab have greatly improved time to treatment for these patients. However, patients who are already in the hospital at the time of STEMI development have been specifically excluded from most analyses. The reasons for this seem appropriate to those of us involved in the care of these patients. The ED admission who was well until the sudden development of chest pain an hour ago is in most cases more straightforward than the sick inpatient with multiple comorbidities who develops STEMI as a complication of another illness. Does this mean that inpatients have been left behind in the door-to-balloon revolution? Who are these patients anyway?
The authors of the current study, who are leaders in development of systems of acute MI care, have developed a comprehensive, prospective program database of patients treated using the Minneapolis Heart Institute regional STEMI program. Like many other systems, their program initally excluded inpatients from the regional protocol established in 2003. In 2010, the standard protocol was expanded to include inpatients. Of the 3795 consecutive STEMI patients treated under this program from 2003-2013, 990 presented directly to the PCI center. Of these, 640 were taken via EMS, 267 arrived driven by themselves or family, and only 83 were already inpatients at these facilities. Notably, only 26 inpatients with STEMI were identified in the 7 years prior to implementation of the standard protocol in 2010, while 57 were detected after implementation. In total, inpatients represented 8.4% of all patients presenting with STEMI during the 10-year period.
Were inpatients presenting with STEMI more complex than outpatients? Of the recorded variables, patient age, body mass index, and rates of hypertension and coronary disease were all greater in the inpatient group. Patients already admitted to the hospital at the time of STEMI presentation also were more likely to present with cardiac arrest or cardiogenic shock, and had a higher average Killip score than those presenting to the ED. Perhaps more telling is the effect of inpatient status on indices of acute MI care. Time from diagnostic ECG to reperfusion was greater for inpatients when compared with door-to-balloon times for patients presenting via EMS (76 minutes [53, 100] vs 51 minutes [38, 71]; P < 0.001), although there was only a nonsignificant trend when compared with those patients arriving by themselves or with family (76 minutes [53, 100] vs 66 minutes [41, 78]; P = 0.13). Only 68.3% of inpatients were reperfused within 90 minutes of the diagnostic ECG, compared with 94% of those arriving by EMS and 85.7% of those arriving by self or family. There was a trend toward greater in-hospital mortality among the inpatient group (8.4% vs 5.5% vs 2.6%; P = 0.061), and an increased rate of death for these patients at 1 year.
Who were these patients? Of the 83 patients identified, only 25 had been admitted with acute coronary syndrome prior to developing ST elevation. Eight had been admitted for PCI and subsequently had either stent thrombosis or a post-PCI dissection. The remainder was a heterogeneous group, and included patients who were post-surgery, admitted for respiratory failure, and patients with cancer or gastrointestinal illness. Unsurprisingly, when compared with the non-cardiac patients, those admitted for primary cardiac reasons showed a trend toward shorter ECG-to-balloon times and had lower in-hospital mortality as well as mortality at 30 days and 1 year. Although the numbers for comparison are small, inpatients who developed STEMI after implementation of the standard protocol had decreased mortality at 1 year compared to patients who developed STEMI prior to the protocol being in place (10.5% vs 30.8%; P = 0.022).
Patients already admitted to the hospital who present with STEMI are indeed complex. Recent examples from my own experience have included a patient with disseminated cancer and HIT, as well as another who was just hours post major vascular surgery. This study does the field a significant service by characterizing these patients. As compared to patients presenting to the emergency department, inpatients clearly have more comorbidities and longer times to reperfusion. Patients admitted with cardiac diagnoses generally had better outcomes. As seen here, although tracking of inpatient STEMIs is generally not done in most systems, it can be highly illustrative.
Importantly, this study is limited in that it only tracked patients who were ultimately brought to the cath lab. Prior studies that were not focused on the procedure have shown that a significant proportion of inpatients are ineligible and are never offered reperfusion.
More importantly, however, this study demonstrates that implementation of standardized STEMI protocols for inpatients can have tangible results, despite the greater complexity and illness severity of these patients.