The heart is asymmetrical, but it’s in roughly the center of the chest. The left auricle and ventricle are larger muscles because they’re pumping through the descending aorta to the extremities, that’s the systemic circulatory branch, the plumbing for which is also largely to the right, while the right are pumping into the lungs alone as part of the pulmonary circulatory branch. The left lung (right on those with situs inversus) has two lobes and basically accommodates the extra muscle mass on its side of the heart, but if you really want to kill someone you stab them through the sternum, kind of dead center, not where they hold their hand when performing patriotism.