From the Guidelines
The location of an aortic dissection significantly affects bilateral blood pressure measurements, and blood pressure should be measured in both arms to determine the highest central blood pressure, as discrepancies of 20 mmHg or more can occur between arms in proximal dissections. In aortic dissections proximal to the left subclavian artery (Stanford Type A or DeBakey Types I and II), blood pressure differences between arms are common, with potential discrepancies of 20 mmHg or more, as the dissection flap can partially obstruct blood flow to one or both subclavian arteries, reducing pressure in the affected limb 1. In contrast, dissections distal to the left subclavian artery (Stanford Type B or DeBakey Type III) typically don't cause upper extremity blood pressure differences since both subclavian arteries receive blood from the true lumen before the dissection begins. However, these distal dissections may cause lower extremity blood pressure differences if the dissection extends into the iliac arteries.
Key Considerations
- The false lumen created by the intimal tear can compress the true lumen or branch vessels, altering blood flow dynamics throughout the arterial system.
- Accurate systemic blood pressure measurement may be complicated by dissection-related occlusion of aortic branch arteries, resulting in erroneously low blood pressure readings in the affected limb 1.
- When evaluating suspected aortic dissection, a significant difference in blood pressure (>20 mmHg) between arms is a clinical clue suggesting proximal dissection.
Management
- The cornerstone of management is initial reduction of the pulse pressure by lowering systolic blood pressure (SBP) below 120 mmHg and heart rhythm ≤60 beats per minute (b.p.m.) to decrease aortic wall stress, as recommended by the 2024 ESC guidelines for the management of peripheral arterial and aortic diseases 1.
- Intravenous beta blockade is generally accepted as the best option for initial treatment, with labetalol as a first choice due to its alpha- and beta-blocking properties.
Clinical Implications
- In-hospital mortality correlates with aortic dissection type, location, patient comorbidities, and treatment, with risk rising with complications like pericardial tamponade, coronary involvement, or malperfusion 1.
- Early placement of an arterial line to monitor blood pressure invasively is mandatory, and admission to an intensive care unit is advisable.
From the Research
Location of Aortic Dissection and Bilateral Blood Pressure Readings
- The location of an aortic dissection can affect bilateral blood pressure readings, with differences in blood pressure between the two arms being a characteristic sign of acute aortic dissection (AAD) 2, 3.
- Studies have shown that patients with type A AAD (TAAD) tend to have lower blood pressure in the right arm compared to the left arm, with an inter-arm difference in blood pressure (IADBP) being more pronounced in TAAD patients 2.
- In contrast, patients with type B AAD (TBAD) do not exhibit significant differences in blood pressure between the two arms, suggesting that the location of the dissection plays a role in the development of IADBP 2.
Factors Influencing Bilateral Blood Pressure Readings
- The presence of an aortic dissection extending to the brachiocephalic artery (BCA) and/or left subclavian artery (LSCA) can influence bilateral blood pressure readings, with patients having a higher prevalence of IADBP 2.
- The use of certain medications, such as esmolol, can also affect blood pressure readings in patients with acute aortic dissection, although the exact role of these medications in managing AAD is still being studied 4, 5.