Chest compressions are pivotal determinants of successful resuscitation. The aim of our study was to identify the variations of the anatomical structures underneath the sternum and to investigate possible implications for chest compressions.

A retrospective study of all patients who underwent a routine chest computed tomography from January 2009 to January 2010 in a tertiary teaching general hospital was performed. The sternum and the area underneath were divided in 2 regions, one consisting of the second and third intercostal spaces, referred to as 2-3 segment, and one consisting of the fourth and fifth intercostal spaces, referred to as 4-6 segment.

During the study period, 677 consecutive scans were analyzed. The most frequent structures beneath 2-3 segment were the left atrium (77.42%) and right atrium (69.82%), followed by the right ventricle (36.64%), left ventricle (35.94%), and left ventricular outflow (31.80%). Underneath 4-6 segment, the most frequent structures were the right ventricle (99.31%) and left ventricle (99.77%), followed by the right atrium (97%), left atrium (96.77%), and left ventricular outflow (36.64%). Interestingly, the difference in occurrence of atria and ventricles in both segments was significant irrespective of sex.

The occurrence of cardiac chambers under the lower part of the sternum is very high, making it a reasonable position for hand placement during chest compressions. However, optimal hand position may differ with age and among healthy individuals owing to variations in thoracic anatomy.