Abstract 115: Relationship of Body Mass Index (BMI) to Minimum Distance from Skin Surface to Myocardium: Implications for Neuromuscular Incapacitating Devices (NMID)
Introduction: It is controversial whether NMIDs can induce cardiac arrhythmias in humans. Studies in swine models have shown varying results. Two reported no induced VF, while a third showed 1 case of induced VF during epinephrine infusion. Two studies showed site sensitivity of cardiac capture depending on location of NMID electrodes. Human studies have not shown any induced arrhythmias. However, it is unclear whether electrodes were placed at the most vulnerable regions of the chest. This study sought to assess the thoracic location and range of minimum skin-to-heart distances (mSHD) and its relationship to BMI.
Methods: Forty-five patients who had undergone cardiac CT scans were randomly selected for evaluation. These scans were analyzed to determine the mSHD and the location of this point on the chest surface relative to anatomic landmarks (horizontal distance from midsternum and vertical distance from sternal insertion of the lowest left rib). Linear regression analysis was performed using BMI and mSHD.
Results: mSHD ranged from 1.8 cm to 6.4 cm. FIGURE 1⇓ shows the linear regression of mSHD vs. BMI. mSHD was to the left of mid sternum (2.5 ± 2.5 cm) and slightly inferior (0.5 ± 2.0 cm) to the lowest left rib sternal insertion. The area of myocardial contact with the anterior chest wall averaged 51 ± 25 cm2, and was unrelated to BMI.
Conclusions: In this study of adults, the average location of the site of mSHD was slightly to the left of mid sternum and just below the lowest rib insertion. There is a linear relationship between BMI and mSHD. The size of a person and the anatomic relationship of the heart to the anterior chest wall can influence the potential cardiac capture by NMIDs at the site of mSHD.