 The left phrenic nerve courses around the left side of the heart and terminates at the diaphragm. Left ventricular pacing leads are typically placed within a coronary vein on the left ventricle to provide cardiac resynchronization therapy. The nearby left phrenic nerve can be inadvertently stimulated as a result of this therapy. The purpose of our study is to assess the extent which the human left phrenic nerve overlays the coronary veins to better understand the potential for undesired phrenic nerve stimulation during cardiac resynchronization therapy. We used 15 perfusion fixed human heart lung blocks obtained from our institution's anatomy bequest program. For each specimen, we located the phrenic nerve. We glued a small wire to the nerve to highlight the nerve's anatomy under computed tomography, also known as CT. We placed the specimen in the CT scanner and injected contrast into the coronary veins with the vinaigram balloon catheter while scanning. From the resulting diagram images, we created three-dimensional models of the coronary veins and left phrenic nerve anatomy. Using these reconstructions, we were able to take various clinically relevant measurements to characterize the locations where the phrenic nerve overlapped the coronary veins. We measured the distance between the nerve and the vein, the distance along the vein to the coronary sinus, the distance along the vein to the coronary sinus ostium, and the proximal angle between the nerve and the vein. We found that the phrenic nerve overlaps with the left marginal vein in 53% of specimens. Note that the left marginal vein is a common location for a left ventricular pacing lead. We also found the nerve course closest to the left marginal vein and the middle cardiac vein. The nerve was typically located on basal regions at the anterior and apical regions at the inferior side of the heart. The distances to the coronary sinus ostium was consistent between overlaps, and there was high variation in the overlapping angles. We will continue to expand this novel anatomical database to provide further insights for avoiding phrenic nerve stimulation during the application of left-sided pacing for cardiac resynchronization therapy.