CBM, the only way that hit would be fatal would be from infection. There are no major arteries above the spine, only muscle. The majority of deer hit there would likely survive. I would say the vast majority of " dead space" shots are actually above the spine. Unless you have a background in anatomy most people would be surprised how low the actual chest cavity is.
Try this. When you kill a deer this fall get a tapemeasure and measure the distance from the bottom of the spine to the sternum inside the chest cavity. Now put your tape on the outside of the deer and measure the width of the chest from top to bottom. I' ll bet you will be surprised.