Echocardiographic clues of the "atrial pump mechanism" during cardiopulmonary resuscitation

Instead of the ventricles, atria may be the cardiac structures mainly compressed during cardiopulmonary resuscitation (CPR). This study aimed to assess the prevalence and the mechanical characteristics of atrial compression, named the "atrial pump mechanism", in patients undergoing CPR. A retrospective cohort study was conducted on patients with witnessed refractory out-of-hospital cardiac arrest who were admitted to a tertiary referral center for extracorporeal CPR. The area of maximal compression (AMC) by chest compressions was assessed by transesophageal echocardiography. Right atrial wall excursion (RA(WE)), left atrial fractional shortening (LA(FS)), right ventricular fractional area change (RVFAC), and left ventricular fractional shortening (LVFS) were measured. Common carotid and middle cerebral artery peak velocities were assessed using color-Doppler imaging as markers of cardiac outflow and cerebral perfusion. Forty patients were included in the study. Five (12.5%) had AMC over the atria. The atrial pump pattern was characterized by marked atrial compression with higher RA(WE) and LA(FS) values compared to the other patients (p < 0.001). Common carotid Doppler and transcranial Doppler-velocity patterns were detectable in all patients with open left ventricular outflow tract, without differences between patients. CPR was successful in four patients (80%) with atrial pump compared to 14 (40%) with no atrial pump mechanism (p = 0.155). In this series of selected patients with witnessed cardiac arrest, the prevalence of the atrial pump mechanism was not negligible. It may contribute to forward blood flow and the maintenance of cerebral perfusion during prolonged cardiopulmonary resuscitation.