The INCORRECT Statement is C: Chest MRI is the diagnostic test of choice
Statement C is incorrect because CT (computed tomography) is the preferred initial diagnostic imaging modality for acute aortic dissection, not MRI. 1, 2
Analysis of Each Statement
A) Target systolic blood pressure 100–120 mmHg - CORRECT
The 2010 ACC/AHA guidelines explicitly state that "reasonable initial targets are a heart rate less than 60 bpm and a systolic blood pressure between 100 and 120 mm Hg" 1. The 2024 ESC guidelines similarly recommend "reduction of the pulse pressure by lowering SBP below 120 mmHg" 3. This target is designed to reduce aortic wall stress and prevent dissection propagation.
B) Heart rate should be ≤60 bpm - CORRECT
Beta-blockade should be titrated to a target heart rate of 60 beats per minute or less 1. The guidelines emphasize that intravenous beta blockade should be initiated first to control heart rate before addressing blood pressure, as this reduces the force of left ventricular ejection (dP/dt) and prevents reflex tachycardia 1, 4.
C) Chest MRI is the diagnostic test of choice - INCORRECT
CT is recommended as the preferred initial imaging test for acute aortic dissection 2. The 2022 ACC/AHA guidelines state: "In patients with a suspected AAS, CT is recommended for initial diagnostic imaging, given its wide availability, accuracy, and speed, as well as the extent of anatomic detail it provides" 2. The 2014 Canadian guidelines similarly recommend CT as the preferred initial test 5.
While MRI has excellent diagnostic accuracy (sensitivity approaching 100%), it has significant limitations in the acute setting:
- Longer acquisition times
- Cannot be performed in unstable patients
- Contraindicated in patients with pacemakers/AICDs
- Less readily available 24/7 5
The guidelines specify that "selection of a specific imaging modality should be based on patient variables and institutional capabilities, including immediate availability" 1. TEE, CT, and MRI all have comparable diagnostic accuracy, but CT's speed, availability, and ability to image the entire aorta make it the first-line choice 1.
D) Chest X-ray may be normal - CORRECT
The guidelines explicitly state that "a negative chest x-ray should not delay definitive aortic imaging in patients determined to be high risk for aortic dissection" 1. Chest X-ray is neither sufficiently sensitive nor specific for diagnosis 2. While abnormal in 60-90% of cases, it can be normal and should not be used to exclude the diagnosis 4.
E) Intravenous morphine is administered for pain relief - CORRECT
The 2001 European guidelines explicitly recommend "pain relief (morphine sulphate)" as part of initial management 4. The FDA-approved morphine label confirms its indication "for the management of pain not responsive to non-narcotic analgesics" 6. Pain control is essential while arranging definitive imaging and helps reduce sympathetic stimulation that could worsen aortic wall stress.
Clinical Pitfalls
- Never delay definitive imaging for chest X-ray in high-risk patients - the X-ray may be normal
- Always control heart rate BEFORE adding vasodilators - to prevent reflex tachycardia that increases aortic wall stress 1
- Don't assume MRI is superior - in acute settings, CT's speed and availability make it the better choice despite MRI's theoretical advantages