Association between preexisting electrocardiographic abnormalities and shockable initial rhythm in out-of-hospital...

Area of Science:

• Cardiology
• Emergency Medicine
• Public Health

Background:

• Initial rhythm in out-of-hospital cardiac arrest (OHCA) is a key determinant of survival.
• The relationship between pre-arrest electrocardiogram (ECG) abnormalities and OHCA initial rhythm is not well understood.

Purpose of the Study:

• To investigate the association between ECG abnormalities recorded 30-365 days before OHCA and the initial rhythm during the event.
• To determine if specific ECG findings predict a shockable initial rhythm in OHCA.

Main Methods:

• Retrospective analysis of OHCA cases from the Danish Cardiac Arrest Registry (2016-2021).
• Linking OHCA data with preceding hospital-recorded ECGs.
• Logistic regression used to estimate odds ratios (ORs) for shockable rhythms, stratified by witness status.

Main Results:

• Among bystander-witnessed OHCA with preceding ECGs, abnormalities were associated with a higher likelihood of a shockable rhythm (OR 1.44).
• Specific abnormalities like pathological Q-waves, left ventricular hypertrophy, atrial fibrillation, intraventricular conduction delay, and left bundle branch block showed increased odds of a shockable rhythm.
• Left bundle branch block demonstrated the highest odds (OR 2.03) for a shockable initial rhythm in witnessed OHCA.

Conclusions:

• Certain pre-arrest ECG abnormalities, including left bundle branch block and atrial fibrillation, are significantly associated with a shockable initial rhythm in bystander-witnessed OHCA.
• These findings suggest that pre-existing cardiac conditions identified by ECG may predispose individuals to specific initial rhythms during cardiac arrest.