Where should we compress? Ultrasound identification of the ideal area of maximal compression for CPR

To characterize the spatial relationship between the ideal area of maximal compression (iAMC), the left ventricular outflow tract (LVOT), and the external chest landmarks using transthoracic echocardiography (TTE), and to assess whether guideline-recommended chest compression location aligns more closely with the LVOT than the iAMC.

We conducted a prospective observational study of adult emergency department patients and volunteers. TTE was used to identify the LVOT (parasternal long-axis view) and the iAMC (parasternal short-axis view). Cardiac structures were mapped to external chest coordinates using a grid referenced to the xiphoid process and compared with the sternal compression location.

A total of 152 participants were enrolled. The median horizontal distance from the sternum was 1.5 cm (interquartile range [IQR] 1-2 cm) for the LVOT and 4 cm (IQR 3-5 cm) for the iAMC. The LVOT was located within 1 cm of the sternum in 50% of participants, compared with 2.7% for the iAMC. The lateral positions of the LVOT and iAMC were moderately correlated (r = 0.489; 95% CI, 0.357-0.601; p < 0.001) but remained spatially distinct in most participants. Heat maps demonstrated overlap between the LVOT and the compression zone, while the iAMC was more lateral. Multivariable analyses demonstrated no independent association between prior intrathoracic surgery or overall body size and iAMC position.

TTE-based anatomic mapping demonstrates that guideline-recommended chest compression location frequently overlies the LVOT rather than the iAMC, suggesting the possibility of physiologic mismatch between CPR hand placement and optimal ventricular compression.