Severe chest pain radiating to the back

A 55 year old man presented to the emergency department with a two hour history of sudden onset chest pain radiating to his back. His past medical problems included hypertension, and he was a smoker.

Although initial observations were normal, within a few minutes he became drowsy, agitated, and started developing weakness of his left arm. The pulses in his left arm were absent.

All initial blood investigations, including cardiac enzymes, were within normal limits, with a haemoglobin concentration of 139 g/l. Twelve lead electrocardiography and chest radiography performed on admission were normal. Tests for cardiac enzymes were subsequently repeated, and results remained within normal limits.

An urgent computed tomogram of the chest and abdomen was performed (figs ¹ and ²).

Fig 1 Coronal reformat of computed tomogram of the chest at the level of aortic arch

Fig 2 Transverse computed tomogram of the abdomen at the level of L1 vertebrae

Questions

(1) What diagnosis do figures ¹ and ² indicate?

(2) At what does the unlabelled arrow in figure ¹ point?

(3) Can you identify the arterial branch, from figure ², affected by the condition?

Answers

(1) Figures ¹ and ² show aortic dissection involving the aortic arch and abdominal aorta.

(2) The arrow points to the dissection flap in the aortic arch.

(3) Figure ² shows the dissection flap involving the superior mesenteric branch of the abdominal aorta. The superior mesenteric artery can be identified because it usually arises at the level of the L1 vertebral body and just superior to the origin of the renal arteries.

Discussion

Aortic dissection is a condition that needs the clinician’s urgent attention and prompt treatment. The condition is twice as common in men as in women, with incidence greatest at ages 55-65.^{w3 w4}

Two anatomic classifications are widely used. Our case was Stanford type A or DeBakey type I.

The Stanford system classifies dissections into 2 types—A and B.^w1 Type A involves the ascending aorta and type B does not. Modified Stanford classification further denotes whether the tear is proximal or distal to the origin of the left subclavian artery because this has therapeutic implications.

The DeBakey classification is much less used and classifies dissections into three types.^w2 Type I involves the ascending aorta, aortic arch, and descending aorta. Type II is confined to the ascending aorta. Type III is confined to the descending aorta distal to the left subclavian artery. Type III dissections are further divided. Type IIIa involves the descending aorta as far as the diaphragm. Type IIIb involves the descending aorta below the diaphragm.

The important feature of aortic dissection is a tear in the intimal layer, regardless of cause,^w5 that allows blood into the medial layer of the arterial wall. If this blood re-enters at a different site a false lumen or channel is created (arrow in fig ²), which in turn can reduce blood flow to major arteries that arise from the aorta. If there is no re-entry site and the blood clots, the term “intramural haematoma” is used, and this can progress to frank dissection.

Underlying causes are either congenital or acquired.^w6 Congenital causes include Marfan’s syndrome, Ehlers-Danlos syndrome, bicuspid aortic valve, and coarctation. Acquired causes include longstanding hypertension, atherosclerosis (particularly by way of penetrating atherosclerotic ulcer) and cocaine misuse. Vascular inflammatory diseases—for example, giant cell arteritis—has also been implicated. Deceleration trauma and iatrogenic factors such as catheterisation and valvular surgery may contribute.

Clinical presentation

Symptoms include chest pain, with the location anterior in 61% and posterior in 36% of cases.^{w4 w6 w7} The quality of pain may vary between worst ever pain (91%), abrupt onset (85%), maximal at onset (85%), sharp (64%), and tearing or ripping pain (51%). The pain may be associated with syncope (9%). Six per cent of patients may not have any pain at all, and 8-13% of the patients may have recurrent abdominal pain.

The signs include aortic insufficiency murmur (32%), pulse deficit (15%), shock (8%), spinal cord ischaemia (10%), and stroke (5%).

Differential diagnoses include myocardial infarction, aortic regurgitation, aortic stenosis, mechanical back pain, myocarditis, pancreatitis, pericarditis and cardiac tamponade, pleural effusion, and pulmonary embolism.^{w6 w7}

Investigations

Chest x ray and electrocardiography may be useful as initial investigations.^{w4 w6 w7} A chest x ray may show widened mediastinum in 50-62% of cases, abnormal aortic contour in 50%, and pleural effusion in 19%. Electrocardiography may show acute myocardial infarction, diagnosed by new Q waves or ST segment elevation in 3% of cases and non-specific ST or T wave changes in 41%.

Computed tomography, magnetic resonance imaging, and transoesophageal echocardiography have high degrees of sensitivity and specificity as diagnostic investigations. Aortography may also be helpful, but has less sensitivity and specificity.

Treatment

The aims of medical treatment are to eliminate pain and reduce systolic blood pressure.^{w7 w8 w9} The drugs used are systemic analgesics (morphine sulphate), intravenous β blockers (metoprolol, propranolol, labetalol) alone or in combination with intravenous vasodilators (sodium nitroprusside). Intravenous calcium channel blockers (verapamil, diltiazem) can be used if β blockers are contraindicated. The indications for medical treatment are uncomplicated type B dissection; stable isolated aortic arch dissection; and chronic stable type B dissection—that is, more than two weeks from onset of symptoms.

The aim of surgery in type A disease is to prevent rupture or development of pericardial effusion, which can lead to cardiac tamponade and death. Acute aortic regurgitation will also need immediate surgical intervention because it may lead to obstruction of coronary flow. Segmental resection of the dissection with interposition of a synthetic graft is usually performed with replacement of aortic valve when it is involved. The mortality rate in surgery ranges 15-35%^w8 and may approach 70%^w7 if associated complications and comorbid factors are present. Indications for surgery are acute type A dissection and acute type B dissection complicated by retrograde extension into the ascending aorta, rupture or impending rupture, and progression with compromise of vital organs.

Endovascular devices (stent-graft placement), which seal the entry to the false lumen and maintain the compressed true lumen, are an alternative treatment for type B disease that is gaining popularity.

In this case, hypertension and smoking might have contributed to the condition. After initial medical stabilisation, the man was immediately transferred to a tertiary referral centre where he underwent emergency surgery, but he died on the third day after operation as a result of subarachnoid haemorrhage.

Competing interests: None declared.

Patient consent: Obtained.

Provenance and peer review: Not commissioned; externally peer reviewed.

References w1-w9 are on student.bmj.com.

1. w1 Nienaber, C. A., Fattori, R., Mehta, R. H., Richartz,et al. on Behalf of the International Registry of Acute A, (2004). Gender-Related Differences in Acute Aortic Dissection. Circulation 109: 3014-3021
2. w2 Hagan PG, Nienaber CA, Isselbacher EM, et al. The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. JAMA 2000 Feb 16; 283(7): 897-903
3. w3 De Bakey ME, Beall AC, Cooley DA, et al. Dissecting aneurysms of the aorta. Surg Clin North Am. 1966;46:1045–1055.
4. w4 Daily PO, Trueblood HW, Stinson EB, et al. Management of acute aortic dissection. Am Thorac Surg. 1970;10:237–247.
5. w5 Wilson SK, Hutchins GM. Aortic dissecting causative factors in 204 subjects. Arch Pathol Lab Med 1982; 106:175-180
6. w6 Nienaber, C. A., Eagle, K. A. (2003). Aortic Dissection: New Frontiers in Diagnosis and Management: Part I: From Etiology to Diagnostic Strategies. Circulation 108: 628-635
7. w7 Khan, I. A., Nair, C. K. (2002). Clinical, Diagnostic, and Management Perspectives of Aortic Dissection. Chest 122: 311-328
8. w8 Nienaber, C. A., Eagle, K. A. (2003). Aortic Dissection: New Frontiers in Diagnosis and Management: Part II: Therapeutic Management and Follow-Up. Circulation 108: 772-778
9. w9 Sato F, Kitamura T, Kongo M, Okinaka T, et al. Newly diagnosed acute aortic dissection: characteristics, treatment modifications, and outcomes. Int Heart J. 2005 Nov;46(6):1083-98

   

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