Aortic Dissection

Aortic dissection begins with a tear in the intima (inner layer) of the aortic wall, allowing pulsatile arterial blood to enter and separate the layers of the media, creating a blood-filled false lumen alongside the true lumen. The false lumen can propagate along the length of the aorta, compromise branch-vessel blood flow (malperfusion), cause aortic regurgitation by disrupting the aortic valve annulus, or rupture through the adventitia — the outermost layer — causing rapidly fatal hemorrhage.

The Stanford classification is the single most important organizing concept in this chapter, because it directly determines management:^[1]

Regardless of type, the immediate priority the moment dissection is suspected is heart-rate and blood-pressure control to reduce aortic wall shear stress (dP/dt) — started before, and independent of, the diagnostic workup being completed.^[2]

Classic presentation

• Sudden, severe, tearing or ripping pain — the hallmark description, often at maximal intensity from the very first moment (unlike the crescendo pattern typical of ACS) — located in the anterior chest for a proximal (Type A) dissection, or the back/interscapular region for a distal (Type B) dissection.
• Migrating pain that moves as the dissection propagates — chest pain moving to the back or abdomen is a genuinely specific clue, though its absence does not exclude dissection.
• Pulse deficit or a blood pressure differential greater than 20 mmHg between the arms (or between an arm and a leg) — reflects a false lumen compromising flow to one side.
• A new diastolic murmur of aortic regurgitation — suggests proximal (Type A) dissection disrupting the aortic valve annulus; may be accompanied by signs of acute heart failure or cardiac tamponade (Beck triad: hypotension, jugular venous distension, muffled heart sounds) if blood dissects into the pericardium.
• Syncope — can reflect tamponade, a cerebral malperfusion event, or a vagal response to severe pain, and is a poor prognostic sign.
• Focal neurologic deficit — from carotid artery involvement, mimicking acute ischemic stroke.

Why this is a critical ACS mimic

• Hypertension — present in roughly two-thirds of patients and the single most common risk factor, particularly when poorly controlled.
• Age over 60, and male sex.
• Known thoracic aortic aneurysm or prior aortic dissection.
• Bicuspid aortic valve.
• Atherosclerosis.
• Connective tissue disorders — Marfan syndrome, vascular Ehlers-Danlos syndrome, Loeys-Dietz syndrome — the dominant risk factor in younger patients (typically under 40) without hypertension or atherosclerosis.
• Vasculitis affecting the aorta — giant cell arteritis, Takayasu arteritis.
• Cocaine or other stimulant use — causes an acute, severe hypertensive surge that can precipitate dissection even without underlying aortic disease.
• Prior cardiac or aortic surgery, or a history of aortic instrumentation (e.g., cardiac catheterization).
• Chest trauma (deceleration injury).
• Pregnancy, particularly the third trimester and early postpartum period in a patient with an underlying connective tissue disorder or bicuspid aortic valve — an important and easily missed context (see Special Populations).
• Family history of aortic aneurysm or dissection, even without a confirmed genetic syndrome.

Immediate investigations

• 12-lead ECG — obtained immediately, primarily to evaluate for a concurrent or mimicking acute coronary syndrome. Often normal or shows nonspecific changes in dissection; a normal ECG does not exclude dissection, and conversely, ST-elevation (especially inferior) can be caused by dissection extending into a coronary ostium rather than primary ACS — do not let a positive ECG alone stop you from considering dissection.^[1]
• Chest x-ray — a widened mediastinum is the classic finding but is insensitive (absent in up to 30% of confirmed dissections) and must never be relied on to exclude the diagnosis; also assess for a pleural effusion (more common on the left) and loss of the aortic knob contour.
• D-dimer — a very sensitive marker; a value below the standard threshold in a patient with a low pretest probability (see ADD-RS below) makes dissection unlikely and can support a decision not to proceed to CT imaging. D-dimer should not be used in isolation to exclude dissection in a patient with a high-risk presentation, and it is not a substitute for definitive imaging once suspicion is more than low.^[3]
• Troponin and other cardiac markers — helpful for identifying concurrent myocardial injury, but do not rule out dissection.

Pretest probability: the Aortic Dissection Detection Risk Score (ADD-RS)

The ADD-RS is a simple 3-category screening tool: 1 point for each of high-risk predisposing conditions (Marfan or other connective tissue disorder, family history of aortic disease, known aortic valve disease, recent aortic manipulation, known thoracic aortic aneurysm), 1 point for high-risk pain features (abrupt onset, severe intensity, tearing/ripping quality), and 1 point for high-risk examination features (pulse deficit or BP differential, focal neurologic deficit with pain, new murmur of aortic regurgitation with pain, hypotension or shock). A score of 0 with a negative D-dimer has a very high negative predictive value and supports pursuing an alternative diagnosis; a score of 1 or more, or any high-risk feature at all, warrants proceeding directly to definitive aortic imaging regardless of D-dimer result.^[3]

Definitive imaging

^[2][4]

• Reduce aortic wall shear stress (dP/dt) immediately to limit propagation and rupture risk, regardless of eventual type or definitive management.
• Achieve target heart rate under 60 beats per minute and target systolic blood pressure 100-120 mmHg as rapidly as safely possible.
• Control pain adequately — pain itself drives catecholamine release, heart rate, and blood pressure, working against the hemodynamic targets above.
• Route every confirmed Type A dissection to emergency surgery without delay.
• Identify malperfusion, rupture, or refractory symptoms in Type B dissection promptly, since these change management from medical to urgent intervention.
• Establish lifelong blood pressure control and structured imaging surveillance in every survivor, whether managed surgically or medically.

• Immediate ICU-level admission with continuous hemodynamic monitoring and an arterial line for beat-to-beat blood pressure measurement — a non-invasive cuff is not adequate for titrating IV antihypertensive infusions in this setting.
• Emergency cardiothoracic surgery consultation the moment Type A dissection is suspected, run in parallel with imaging rather than sequentially after it.
• Thoracic endovascular aortic repair (TEVAR) or open surgical repair for complicated Type B dissection, per Choose Initial Treatment.
• Strict bed rest and a calm, low-stimulation environment during the acute phase to avoid further catecholamine-driven blood pressure surges.
• Avoid any activity that raises intrathoracic or intra-abdominal pressure (straining, Valsalva, vigorous coughing) — provide antiemetics and stool softeners proactively.
• Multidisciplinary genetics referral for a patient with a suspected connective tissue disorder (young age, disproportionate body habitus, joint hypermobility, family history) — informs both the patient's own long-term management and screening of first-degree relatives.

Pregnancy

Dissection in pregnancy is rare but disproportionately affects patients with an underlying connective tissue disorder (Marfan syndrome especially) or bicuspid aortic valve, and clusters in the third trimester and early postpartum period — hormonal and hemodynamic changes of pregnancy increase aortic wall stress. Maintain a high index of suspicion in a pregnant or recently postpartum patient with severe chest or back pain, especially with a known connective tissue disorder or aortic root dilation on prior imaging; do not dismiss the presentation as musculoskeletal or reflux-related pain without considering it. Emergency multidisciplinary management (obstetrics, cardiothoracic surgery, maternal-fetal medicine) is required — the same Stanford-type-based approach applies, with delivery timing (often expedited via cesarean, sometimes combined with or immediately followed by aortic repair) individualized to gestational age and maternal stability. Labetalol is the preferred beta-blocker in pregnancy given the extensive safety experience with this agent in obstetric hypertension.

Connective tissue disorders (Marfan syndrome, vascular Ehlers-Danlos syndrome, Loeys-Dietz syndrome)

These patients dissect at smaller aortic diameters and younger ages than the general population, so the same absolute size thresholds used for atherosclerotic aneurysms do not apply — elective repair of an associated aneurysm is considered at a smaller diameter, per the syndrome-specific thresholds in current guidance. After an acute dissection, lifelong beta-blocker therapy is standard, and an angiotensin receptor blocker (losartan) has trial evidence supporting a reduction in aortic root growth rate in Marfan syndrome specifically and is frequently added or substituted for this reason. Refer for genetic counselling and cascade screening of first-degree relatives.^[2]

Renal impairment

Adjust contrast strategy for CT angiography where possible without delaying emergency imaging; if sodium nitroprusside is used, monitor closely for cyanide/thiocyanate accumulation, which occurs faster in renal impairment — consider nicardipine preferentially in this setting.

Older adults

Presentation is more likely to be atypical (less classic tearing pain, more often painless or presenting primarily with syncope or altered mentation), and comorbidity burden affects the surgical-risk discussion for Type A repair — but age alone is not a reason to withhold emergency surgical referral, since untreated Type A dissection is uniformly fatal without intervention.

Continuous arterial-line blood pressure and heart-rate monitoring throughout the acute admission, with the same HR <60 bpm and SBP 100-120 mmHg targets maintained until definitive repair (Type A) or through the full acute medical-management period (uncomplicated Type B). After the acute phase — whether managed surgically or medically — every patient needs lifelong blood pressure control (target generally under 130/80 mmHg, individualized) and continuation of beta-blocker therapy indefinitely, since recurrent dissection and late aneurysm formation both remain elevated risks for life.^[2]

Structured imaging surveillance is mandatory for life: CT or MR angiography before discharge to establish a new baseline, then repeated at 1, 3, 6, and 12 months after the acute event or repair, and annually thereafter if stable (more frequently if any change is detected or the aortic diameter is enlarging) — the goal is early detection of aneurysmal degeneration of the residual false lumen, an endoleak after TEVAR, or a new dissection before it becomes symptomatic.^[2][4]

Counsel every patient to avoid heavy resistance/isometric exercise and activities involving Valsalva-type straining indefinitely, and to seek immediate emergency care for any recurrence of severe chest, back, or abdominal pain rather than waiting for the next scheduled follow-up.

1. Heart rate or blood pressure remains above target despite an adequately titrated beta-blocker plus a vasodilator: reassess for uncontrolled pain, anxiety, urinary retention, or an underlying secondary cause driving catecholamine release, and treat those directly rather than simply escalating drug doses further; involve critical care for a third agent if genuinely refractory.
2. New or worsening malperfusion signs (neurologic deficit, limb ischemia, oliguria, abdominal pain) in a previously uncomplicated Type B dissection: this converts the case to complicated Type B — obtain urgent vascular/cardiothoracic surgery reassessment for TEVAR rather than continuing medical management alone.
3. Hemodynamic instability or new signs of tamponade at any point: treat as rupture until proven otherwise and escalate for immediate surgical intervention — do not wait for scheduled repeat imaging.
4. Recurrent or progressive dissection identified on surveillance imaging: repeat cross-sectional imaging promptly and refer back to the surgical team that performed the original repair (or vascular/cardiothoracic surgery if managed medically) for reassessment rather than simply extending the surveillance interval.
5. New aortic regurgitation murmur or heart failure symptoms developing after initial stabilization: obtain echocardiography promptly — may indicate progression of valve annular disruption requiring surgical reassessment.

• Starting a vasodilator (nicardipine, nitroprusside, or any other) before a beta-blocker has achieved adequate rate control — the single most important sequencing error in this condition, since reflex tachycardia from an unopposed vasodilator raises dP/dt and can propagate the dissection.^[2]
• Giving a thrombolytic or therapeutic-dose anticoagulant for presumed ACS or pulmonary embolism without first considering dissection, especially when the pain is tearing/migrating, a pulse deficit or limb BP differential is present, or the chest x-ray shows a widened mediastinum.
• Treating an inferior STEMI pattern on ECG as routine ACS without considering that dissection extending into the right coronary ostium can produce the identical ECG picture.
• Relying on a normal chest x-ray, a normal ECG, or the absence of the classic pain/pulse-deficit/murmur triad to exclude dissection — each of these is individually insensitive, and the full classic triad is present together in only a minority of confirmed cases.
• Delaying emergency surgical consultation for a suspected Type A dissection while completing an extensive diagnostic workup — surgical notification should happen in parallel with, not after, confirmatory imaging.
• Treating uncomplicated Type B dissection as a surgical emergency, or conversely, continuing medical management alone once a genuine complication (malperfusion, rupture, refractory pain/hypertension) has developed.
• Stopping surveillance imaging after the first year, or after surgical repair feels "complete" — lifelong imaging surveillance is required regardless of management strategy.
• Missing an underlying connective tissue disorder in a younger patient (under 40) presenting without the usual hypertension/atherosclerosis risk factors — this changes both acute counselling and long-term aortic-size thresholds for family members.

How to use this table: Doses are adult doses for acute IV heart-rate/blood-pressure control and require patient-specific confirmation, including renal/hepatic adjustment and institutional protocol. Select any drug name to open its complete Pharmasist Drug Database page.

Beta-blockers (give first, before any vasodilator)

Titrate to heart rate under 60 bpm before adding a vasodilator. Use a non-dihydropyridine calcium channel blocker instead only if a beta-blocker is contraindicated.

Vasodilators (add only after adequate beta-blockade)

Never start before heart rate is controlled with a beta-blocker — an unopposed vasodilator causes reflex tachycardia that raises aortic wall shear stress (dP/dt) and can propagate the dissection.

Analgesia

Treat pain proactively alongside heart-rate/BP control — uncontrolled pain sustains catecholamine-driven tachycardia and hypertension.

Long-term therapy after repair or medically managed Type B

Continue indefinitely in every survivor, alongside structured lifelong imaging surveillance.