What are the symptoms and expected laboratory findings of acute aortic dissection in an older adult with a history of spine-related conditions?

Acute Aortic Dissection: Definition, Symptoms, and Laboratory Findings

What is Acute Aortic Dissection?

Acute aortic dissection is a life-threatening tear in the inner layer of the aorta that creates a false lumen as blood dissects through the medial wall, with mortality reaching 50% within 48 hours if untreated and 1-2% per hour after symptom onset. 1, 2 The condition is classified as Type A (involving the ascending aorta) or Type B (involving only the descending aorta), with Type A requiring emergency surgery and Type B often managed medically unless complications develop. 1

Clinical Symptoms

Pain Characteristics (Most Common Presentation)

The hallmark symptom is abrupt onset of severe pain at maximum intensity from the very beginning, occurring in 74-84% of patients. 1, 3 This differs critically from myocardial infarction, where pain builds gradually over time. 1

• Type A dissections present with anterior chest pain (retrosternal) in 71% of cases, though back pain occurs in 47% as the dissection extends into the descending aorta 3
• Type B dissections present with interscapular back pain in 64% of cases 3
• Pain is described as sharp or stabbing in 51-64% of patients, not the "classic" tearing or ripping quality many clinicians expect 4, 3
• Migrating pain occurs in 12-55% as the dissection extends along the aorta 3
• Abdominal pain occurs in 21% of Type A and 43% of Type B dissections 3

Painless Presentations (Critical Pitfall)

Up to 6.4-15% of patients present without pain, particularly older adults, those on steroids, and patients with Marfan syndrome. 1, 3 These patients more commonly present with:

• Syncope (occurring in approximately 13-15% overall, associated with 34% mortality versus 23% without syncope) 1
• Acute congestive heart failure from severe aortic regurgitation 1
• Stroke or altered mental status (more common in women) 1, 3
• Abnormal chest radiograph discovered incidentally 1, 5

Cardiovascular Manifestations

• Blood pressure abnormalities: 71% of Type B patients are hypertensive (>150 mmHg systolic) versus only 36% of Type A patients 1
• Hypotension or shock occurs in nearly 20%, indicating cardiac tamponade, aortic hemorrhage, severe aortic regurgitation, or myocardial ischemia—all associated with significantly higher mortality 1
• Pulse deficits occur in less than 20% of patients (historically reported as 50% in older series), may be transient due to flap movement 1
• Blood pressure differential between arms requires measuring all four extremities to determine true central pressure 1
• Cardiac tamponade occurs in 8-10% of Type A dissections and is an ominous predictor requiring truly urgent repair 1

Neurological Complications

Neurological symptoms occur in 17-40% of patients and may dominate the clinical picture, masking the underlying aortic pathology. 1 This is particularly important in older adults with spine-related conditions where symptoms may be misattributed:

• Ischemic stroke occurs in 53% of those with neurological symptoms, predominantly right hemispheric 1
• Ischemic neuropathy with limb pain and sensory/motor deficits occurs in 37% 1
• Acute paraplegia from spinal cord malperfusion occurs in 1-3% and may be painless, potentially mimicking Leriche syndrome 1, 6
• Up to 50% of neurological symptoms are transient, and one-third of patients with neurological deficits present without chest pain 1
• Patients with neurological deficits have significantly higher mortality (34% versus 23%) and more frequently present with hypotension, shock, or tamponade (46.8% versus 25.2%) 7

Pulmonary and Other Manifestations

• Pleural effusion occurs in 15-20% at presentation, usually small and inflammatory, though large effusions suggest aortic bleeding 1
• Dyspnea from pulmonary artery compression or aortopulmonary fistula 1
• Hemoptysis (3% of cases) from lung compression or direct rupture into lung parenchyma 1
• Mesenteric ischemia occurs in approximately 5% of Type A dissections with 63% mortality versus 24% without this complication 1
• Oliguria or anuria from renal artery involvement 1

Expected Laboratory Findings

D-Dimer

D-dimer >0.5 µg/mL has 91-100% sensitivity for acute aortic dissection and is the most useful laboratory marker, with levels typically immediately very high compared to other conditions where D-dimer rises gradually. 1, 4, 3 However:

• D-dimer should never be used alone to rule out dissection 4, 3
• False negatives occur with chronic dissections, thrombosed false lumen, intramural hematoma without intimal flap, short dissection length, or in young patients 3
• Negative D-dimer does not exclude intramural hematoma or penetrating aortic ulcer 1
• Highest diagnostic value occurs within the first hour of presentation 1

Other Laboratory Findings

• Elevated creatine kinase may indicate acute skeletal muscle ischemic necrosis from limb malperfusion 6
• Elevated serum creatinine and decreased glomerular filtration rate suggest acute kidney injury from renal artery involvement 6
• Elevated lactate dehydrogenase and acute phase proteins with persistent abdominal pain indicate celiac or mesenteric artery involvement (8-13% of cases) 1
• High fever can occur from release of pyrogenic substances from the aortic wall and may persist, potentially mimicking inflammatory disease 1

Critical Diagnostic Considerations for Older Adults with Spine Conditions

In patients over 70 years, typical symptoms (abrupt pain onset) and signs (aortic regurgitation murmur, pulse deficits) are significantly less common, requiring extra vigilance. 1 This is particularly relevant when:

• Back pain may be attributed to pre-existing spine pathology rather than dissection 3
• Acute paraplegia may be misdiagnosed as a spine-related emergency rather than spinal cord malperfusion from dissection 1, 6
• Painless presentations are more common in elderly patients 3

The misdiagnosis rate for acute aortic dissection ranges from 14-31%, with myocardial infarction being the most common incorrect diagnosis. 8, 9 Maintaining high clinical suspicion is essential, particularly when patients present with catastrophic illness and unexplained vascular symptoms. 5