Although dissection may originate anywhere along the aorta, it occurs most commonly at areas of greatest hydraulic stress, which are the Right lateral wall of the ascending aorta (within 5 cm of the aortic valve) Proximal segment of the descending aorta (just beyond the origin of the left subclavian artery) Rarely, dissection is confined to individual arteries (eg, coronary or carotid arteries), typically in pregnant or postpartum women.