Introduction: The diagnostic management of patients with symptoms indicative of acute myocardial infarction (MI) is based on the assessment of symptoms, ECG and diagnostic algorithms based on high-sensitivity cardiac troponin (hs-cTn). Additionally, guidelines recommend transthoracic echocardiographic evaluation (TTE) for patients neither eligible for rule-out nor rule-in. 

Purpose: To assess the diagnostic performance of adding TTE to the diagnostic management of patients with suspected MI.

Methods: We conducted a prospective, observational cohort study enrolling consecutive patients presenting with symptoms suggestive of MI to the emergency department of a tertiary care hospital. Management was at the discretion of the treating physician. The final diagnosis was adjudicated by two independent cardiologists according to the 4^th Universal Definition of MI. Evaluation in the emergency department included TTE with an assessment of left-ventricular (LV) ejection fraction (EF) and regional wall motion abnormalities (WMA). We calculated diagnostic performance parameters (negative and positive predictive value [NPV, PPV] specificity and sensitivity with 95% confidence intervals) to rule-out or rule-in MI, respectively, for the presence of WMA and separately for LVEF (normal vs. impaired) in the overall study population, and additionally in the observe and rule-in groups after application of the hs-TnI based ESC 0/1-hour algorithm. Patients without available TTE and those with STEMI were excluded. 

Results: Overall,  2,163 patients with available TTE were included . Median age was 64 (51, 75) years, 1,383 (63.9%) were males and 383 (17.7%) were diagnosed with MI. Data on LVEF was available in all and on WMA in 1,707 (78.9%) patients. In total, 435 (20.1%) had reduced LVEF and 360 (21.1%) had any WMA detected. Application of the ESC 0/1-hour algorithm resulted in assignment of 803 (37.1%) patients to the observe and 388 (17.9%) patients to the rule-in groups, respectively. Without TTE, the PPV to identify MI in the rule-in group was 62.6% (57.6, 67.5). In the observe group MI prevalence was 7.1% (57 patients). 

After combination of the ESC 0/1-hour algorithm with information on TTE (Figure 1) in the observe group, absence of WMA and normal LV function had high NPVs (94.0% [91.4, 95.8] and 94.5% [92.4, 96.1], respectively). However, sensitivity was low (37.8 [25.1, 52.4] and 42.1 [30.2, 55.0], respectively). The PPV for LV impairment or present WMAs to identify patients with MI was low (11.9% [8.1, 17.1] and 12.7% [8.1, 19.4], respectively). In the rule-in group, LVEF-reduction had a PPV of 60.1% (51.8, 67.9), while presence of any WMA resulted in a PPV of 71.0% (62.7, 78.1).  

Conclusion: The routine application of TTE in the diagnostic management of patients with suspected MI aids only modestly in patients neither eligible for rule-out nor rule-in using the ESC 0/1h algorithm. A finding of reduced LV function or the presence of WMA had low discriminatory power to identify patients with true MI, vice versa normal LVEF or absence of WMA only poorly excluded MI. Only in the rule-in group, the presence of WMA increased the PPV to identify patients with true MI. In conclusion, routine TTE assessment remains reasonable to diagnose or exclude differential diagnoses associated with acute chest pain, although the diagnostic performance of TTE in this all-comer setting does not exceed the performance of hs-cTn-based protocols to diagnose MI.