Cardiac arrest in cardiogenic shock: a complication or a different condition?

Background Cardiac arrest (CA) profoundly impacts outcomes in cardiogenic shock (CS), but differences between CS with and without CA remain unexplored. Methods The Cardiogenic Shock Working Group registry was queried for patients with CA. Comparisons were made between patients with and without CA. Continuous variables were compared using Wilcoxon’s test. Categorical variables were compared using Chi squared analyses. Results Out of 7,644 patients with CS, 2038 (26.7%) experienced CA. There was no difference in age or in male/female representation between those with and without CA. In-hospital mortality was 1156 (20.6%) in patients with no CA and 1094 (53.7%) in those with CA, p<0.001. Treatment intensity, including both vasoactive drugs and mechanical circulatory support (MCS), was higher in survivors of CA, and they had lower chances of having durable LVAD or heart transplantation (5.0% vs 17.9%, p<0.001). In terms of co-morbidities, patients with CA had a smaller proportion of individuals with the history of hypertension , diabetes, atrial arrhythmias, stroke, chronic kidney disease, valvular disease, percutaneous coronary interventions, and implantable defibrillators (Table). By echocardiography, patients with CA had higher left ventricular ejection fraction (LVEF) (25 [17, 40] vs 22.5 [15, 35], p<0.001). they also had smaller LV end diastolic dimension (5.0 [4.3, 5.8] vs 5.6 [4.7, 6.6], p<0.001) and lower proportion of patients with severe mitral regurgitation. While the systemic blood pressure and cardiac output, as well as right atrial pressure, were similar, pulmonary arterial pressures were lower in the CA group, and their cardiac power output was higher. Conclusions In cardiogenic shock, patients with cardiac arrest displayed some favorable features, such as fewer chronic comorbidities (hypertension, diabetes, atrial arrhythmias, history of stroke, chronic kidney disease, valvular disease, percutaneous coronary interventions, and implantable defibrillators), higher LVEF, smaller LV, lower pulmonary arterial pressures, less tachycardia, and higher cardiac power output that those who did not have CA. Despite that, they have higher mortality. Cardiac arrest, therefore, constitutes a separate entity within CS, and should not be automatically considered a complication of the latter. This questions the common practive of inclusion of patients with cardiac arrest in the studies on cardiogenic shock.