Introduction: Emergency vs. delayed cardiac catheterisation (CC) continues to be the subject of considerable debate in resuscitated out-of-hospital cardiac arrest (OHCA). This study aimed to investigate whether cardiologists can reliably determine, from a brief clinical summary and ECG, those patients for whom delayed or no CC is appropriate without missing acutely ischaemic cases.
Hypothesis: We hypothesised that there is agreement on ECG diagnosis, working diagnosis and CC timing between cardiologists, and that cardiologists can identify OHCA patients not requiring immediate PCI
Methods: Presenting clinical details (within 2hrs) and ECGs from 112 consecutive OHCA patients admitted to an Australian hospital from 2011-14 were compiled retrospectively. Three OHCA-experienced interventional cardiologists, blinded to patient outcome, independently determined ECG diagnosis, working diagnosis, and consequent CC timing. Results were linked with CC findings (n=72) and final diagnosis. Free-marginal kappas of agreement, positive (PPV) and negative (NPV) predictive values were calculated.
Results: Cardiologist agreement for ECG diagnosis (κ = 0.60) and working diagnosis (κ = 0.50) was moderate. Agreement for CC timing was good (κ = 0.63), and reached very good agreement in cases where the final diagnosis was ischaemic (κ = 0.89), vs. cardiac non-ischaemic (κ = 0.44) and non-cardiac (κ = 0.57). For any instance where immediate CC was selected PPV for PCI was 52% (95% CI: 48.22% to 55.51%; cardiologist range 46-63%), NPV was 98% (CI: 87.7 - 99.7%; cardiologist range 94-100%). Instances of true negatives (delayed or no CC and no PCI) ranged from 21-44% between cardiologists.
Conclusions: Despite moderate agreement amongst the 3 cardiologists for ECG and working diagnoses, there was very good agreement for CC timing for ischaemic aetiologies. The primary finding of our study is that cardiologists, using only a brief clinical summary and ECG, can exclude OHCA patients not requiring immediate PCI without missing acutely ischaemic cases with up to 100% accuracy. These patients represent 21-44% of the population suggested by current guidelines to undergo immediate CC that instead should be investigated to exclude non-ischaemic aetiologies.