Letter by Neeland and de Lemos Regarding Article, “Rates of Cardiac Catheterization Cancelation for ST-Segment Elevation Myocardial Infarction After Activation by Emergency Medical Services or Emergency Physicians: Results From the North Carolina Catheterization Laboratory Activation Registry”
To the Editor:
We read with great interest the recent article by Garvey et al.1 The investigators found that 15% of cardiac catheterization laboratory activations in a state-wide percutaneous coronary intervention-capable hospital registry were inappropriate, defined as cancellation of catheterization as a result of electrocardiographic reinterpretation or the patient was not deemed suitable for the procedure. Interestingly, even among those who had an appropriate catheterization, 365 (10.8%) patients had false-positive laboratory activation, defined as no culprit artery identified on angiography. This finding is consistent with a previous report by Larson et al2 in which 14% of patients undergoing cardiac catheterization for suspected ST-elevation myocardial infarction (STEMI) did not have a culprit coronary artery on angiography.
Patients presenting with a suspected myocardial infarction in the setting of a new or presumed new left bundle-branch block (LBBB) are currently considered to have a STEMI equivalent with the recommendation to undergo early reperfusion therapy with fibrinolysis or percutaneous coronary intervention. However, LBBB has a low diagnostic specificity for STEMI-equivalent myocardial infarction and is a frequent cause of false-positive cardiac catheterization laboratory activation.3,4 For example, in the study by Larson et al,2 44% of patients presenting with LBBB did not have a culprit coronary artery identified by angiography. These findings have been confirmed in a recent study by Lopes et al5 demonstrating that 39% of the 98 patients with new LBBB did not have an occluded culprit artery at angiography.
Given that patients with LBBB were included in the RACE (Reperfusion of Acute Myocardial Infarction in Carolina Emergency Departments) registry (http://www.nccacc.org/RACE/RACEOperationsManualOct.09.pdf, page 20) but were not specifically discussed in the present analysis by Garvey et al,1 we inquire as to the appropriateness of catheterization laboratory activation in patients presenting with new or presumed new LBBB in this registry. Do the authors have data on what proportion of STEMI patients in the registry had catheterization laboratory activation attributable to a new or presumed new LBBB? What was the appropriateness (ie, percentage cancellations attributable to electrocardiographic reinterpretation or patient unsuitability) and false-activation rate (ie, percentage of patients without an occluded culprit artery on angiography) in patients with LBBB?
We believe that inclusion of patients with LBBB in analyses of false-positive or inappropriate catheterization laboratory activation is important for future studies on this topic. Understanding the impact of LBBB on cardiac catheterization laboratory practice patterns relative to ST-elevation with normal conduction (given the low specificity and positive predictive value of LBBB for STEMI-equivalent myocardial infarction) may allow improved STEMI quality reporting (eg, door-to-balloon times), which would provide more specific and accurate evaluation of systems of care and quality of outcomes in STEMI.
Ian J. Neeland, MD
James A. de Lemos, MD
Division of Cardiology
University of Texas Southwestern Medical Center
Dr de Lemos has received grant support from Roche Diagnostics and Abbott Diagnostics.
- © 2012 American Heart Association, Inc.
- Garvey JL,
- Monk L,
- Granger CB,
- Studnek JR,
- Roettig ML,
- Corbett CC,
- Jollis JG