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KEY POINTS

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  • Potentially the most important diagnosis with highest life-saving capability in medicine.

  • Challenging diagnosis requiring high clinical suspicion and quick, efficient use of diagnostic modalities.

  • Clinically, the typical pain, incongruous poor tissue perfusion despite hypertension, and/or evidence of aortic branch occlusion suggest the diagnosis.

  • Emergent control/support of blood pressure and pain is imperative.

  • Investigation with urgent CT angiogram or TEE to confirm diagnosis and complications.

  • Categorize as type A (ascending aorta involved) versus type B (only descending aorta involved) to direct definitive treatment.

  • Type A requires emergency cardiac surgical repair.

  • Type B managed with emergency medical management versus endostenting or surgery if complicated.

  • Long-term strict control of hypertension and surveillance important to identify need for late intervention and maximize long-term survival.

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INTRODUCTION

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Aortic dissection occurs much more frequently than previously appreciated and is actually the most common catastrophe affecting the aorta, occurring 2 to 3 times more commonly than acute abdominal aortic aneurysm rupture.1-3 Although the diagnosis is sometimes obvious, the majority of cases are not clear-cut and the patient’s survival will depend on a high index of suspicion by the physician despite a myriad of different clinical presentations. Time is of the essence as the mortality is 50% for the first 48 hours without treatment and 85% to 90% over 3 months. The typically hypertensive patient must have their blood pressure and pain controlled quickly followed by rapid diagnosis with definitive imaging and immediate relegation to the appropriate therapy of either emergency surgery or medical management/endostenting.

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PATHOGENESIS

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Previously, aortic dissections were referred to as dissecting aneurysms, as originally coined by Laënnec. This is a misnomer in that the pathology is a dissecting hematoma that separates the intima and inner layers of the media from the outer medial and adventitial layers (Fig. 42-1). The intima is therefore not aneurysmal, and is, if anything, narrowed. Blood invades the media through a tear in the intima and proceeds ante- or retrogradely through the aortic wall, forming a false lumen.4 In type A dissections (originating in the ascending aorta) the hematoma commonly spirals around the right and posterior aspects of the ascending aorta, supraposteriorly along the arch, and then down the left and posterior aspects of the descending aorta. The hematoma may then have several serious sequelae. It may rupture into the pericardial space causing tamponade or into the pleural space with exsanguinating hemorrhage, especially in type B dissections (begin after the left subclavian artery). This occurs less frequently than expected because the adventitial layer represents 66% of the overall strength of the aortic wall. It may also cause occlusion of aortic branch arteries or prolapse of one or more of the aortic valve cusps, resulting in acute aortic insufficiency.

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FIGURE 42-1

Aortic dissection begins with an intimal tear (1) leading to a hematoma that separates the layers of the aortic wall. The sequelae are ...

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