Identification of 4th intercostal space using sternal notch to xiphoid length for accurate electrocardiogram lead placement

• Accurate ECG interpretation is dependent on proper lead placement.
• The right 4th intercostal space can be difficult to identify in obese patients.
• Right 4th intercostal space is 67% of the sternal notch to xiphoid process length.

ObjectivePrecordial ECG lead placement is difficult in obese patients with increased chest wall soft tissues due to inaccurate palpation of the intercostal spaces. We investigated whether the length of the sternum (distance between the sternal notch and xiphoid process) can accurately predict the location of the 4th intercostal space, which is the traditional location for V1 lead position.Materials and MethodsFifty-five consecutive adult chest computed tomography examinations were reviewed for measurements.ResultsThe sternal notch to right 4th intercostal space distance was 67% of the sternal notch to xiphoid process length with an overall correlation of r = 0.600 (p < 0.001).ConclusionThe above measurement may be utilized to locate the 4th intercostal space for accurate placement of the precordial electrodes in adults in whom the 4th intercostal space cannot be found by physical exam.