Paced Electrocardiogram Requiring Fast Emergent Coronary Therapy (PERFECT) Study (PERFECT)

BACKGROUND Diagnosis and management of ACO (the anatomic substrate for ST-elevation myocardial infarction) is time sensitive. Diagnosis necessitates emergent reperfusion therapy. An important predictor of death from ACO includes time to reperfusion.1 Delays in reperfusion therapy, including primary percutaneous coronary intervention (PCI) or fibrinolysis, are associated with worse 30-day and 1-year mortality. American Heart Association (AHA) guidelines for treatment of ACO recommend that the first medical contact to device time be less than 120 minutes in patients who have no contraindications to treatment.2 Though cardiac biomarkers are helpful in making the diagnosis in uncertain cases, the time sensitive nature of intervention for ACO precludes their use to direct emergent reperfusion therapy. Furthermore, biomarkers do not diagnose ACO but rather any AMI, including those without occlusion that do not need emergent intervention.

The "traditional" ECG diagnosis of ACO, which includes ST-elevation cutoffs based upon age and sex, excludes patients with ventricular paced rhythm (VPR).3 The small field of research on the topic of ACO in VPR has extrapolated and analyzed data from patients with left bundle branch block (LBBB). That is because VPR with right ventricular pacing and LBBB both result in depolarization from right to left through myocardium (not through conducting fibers) and thus result in similar ECG findings (e.g. wide QRS, delayed onset of depolarization, and abnormal repolarization with "discordant" [in the opposite direction of the QRS] T-waves and ST-segment deviation). In the presence of known LBBB, AHA guidelines recommend using the Sgarbossa criteria to make the diagnosis of ACO.4 Sgarbossa et al. proposed requiring at least 3 points from the following criteria for the diagnosis of acute myocardial infarction in the presence of LBBB: (1) concordant ST-segment elevation of 1 mm (0.1 mV) in at least 1 lead (5 points), (2) concordant ST-segment depression of at least 1 mm in leads V1 to V3 (3 points), or (3) excessively discordant ST-segment elevation, defined as greater than or equal to 5 mm of ST-segment elevation when the QRS complex is negative (2 points). There have been only a handful of evaluations of Sgarbossa's criteria in VPR, with variable methodologies and patient populations; sensitivities in the studies ranged from 10-53% and specificities ranged from 84-99%.5,6 Neither study used angiographic endpoints, but only used biomarker definitions of AMI; one study used a very flawed biomarker definition with no adjudication. Thus, the number of occlusions is entirely unknown and probably very small.

For LBBB, Smith et al. derived and validated a "modified Sgarbossa rule" in which they replaced Sgarbossa's third criterion (excessively discordant ST elevation as defined by 5 mm) with a proportion-based criterion (defined by > 25% of the previous S-wave) (see Table 1). This rule resulted in much higher sensitivity and accuracy for diagnosis of ACO than the original Sgarbossa.7,8

Table 1: MODIFIED SGARBOSSA CRITERIA

1. ST-segment elevation >= 1 mm and concordant with the QRS in any lead
2. ST-segment depression >= 1 mm and concordant with the QRS in any of leads V1- V3
3. Proportionally excessive discordant ST-segment elevation in at least one lead, as defined by ST/S (</= -0.25) with at least 1 mm of STE

The modified Sgarbossa criteria have never been evaluated in patients with VPR and very few additional criteria have ever been evaluated. To our knowledge, no criteria have been evaluated using an angiographic outcome, the only outcome relevant to guiding emergency reperfusion therapy. The primary purpose of this study will be to investigate the diagnostic performance of selected ECG criteria for the diagnosis of ACO in VPR. Through the process of answering this question, a database will be formed to answer multiple additional questions on this patient population that is underrepresented in clinical trials.

STUDY DESIGN The primary analysis will be designed as a multicenter, retrospective case-control study. Additionally, data will be collected to create a database of de-identified patient information that will allow researchers to investigate numerous additional questions.

Study sites will include Hennepin County Medical Center (HCMC, the lead site) and academic and community centers (study sites) located internationally. Because AMI was redefined in 2007 by a rise and/or fall of troponin, with at least one value above the 99% reference value,9 our study will only include subjects that presented from January 1, 2008 through December 31, 2015.