ECG can’t be used to rule out hyperkalemia. It may be present and electrocardiographically silent. But if you see the changes, ECG can be used to rule it in. Sensitivity was 19%; specificity 97%.
The original Sgarbossa criteria have a high specificity (96%) but low sensitivity (36%), meaning it is useful when positive, but a negative result does not rule out MI. The modified Sgarbossa criteria by Smith et al., have a much better sensitivity (91%) with a slight decrease in specificity (90%). You should apply the modified Sgarbossa criteria to evaluate for MI in LBBB and paced rhythms.
In this single center, the Generation 5 high-sensitivity troponin T assay would have allowed acute MI rule out at baseline in 29% of patients and 41% at 30 minutes with 100% NPV and sensitivity. This needs multicenter prospective confirmation, but it shows the future feasibility and utility of high sensitivity troponin pathways.