Shyam Sunder Tipparaju, Gopinath Ramachandran,

Ravinuthala Venkat Kumar, and Muppiri Vijay Kumar

A 57-year-old male patient with long-term, poorly controlled hypertension developed severe precordial chest pain, radiating to the back while gardening. The physical examination showed temperature 99°F, pulse 110/min, respiration 20/min, BP 200/100 mmHg (right arm) and 180/90 mmHg (left arm), decreased left brachial and radial pulses, and diastolic murmur along the left sternal border.

Aortic dissection is a relatively uncommon disorder as compared to other cardiac emergencies such as acute myocardial infarction (AMI) or congestive heart failure (CHF). It carries a high mortality of 1% every hour for initial 48 h, if not properly recognized and managed.

Step 1: Resuscitate urgently

•Emergent control of hypertension and maintaining organ perfusion is the priority in initial resuscitation (see Chap. 24).

Step 2: Assess urgently

•Time is of essence in managing aortic dissection, and a focused history and focused physical examination should be quickly performed to differentiate causes of acute chest pain (Tables 25.1 and 25.2).

S.S. Tipparaju, M.D., P.D.C.C. (*)

Critical Care, Continental Hospitals, Hyderabad, India e-mail: shyamsundert@rediffmail.com

G. Ramachandran, M.D., F.F.A.R.C.S.

Department of Anaesthesiology & Critical Care, Nizam Institute of Medical Sciences, Hyderabad, India

R.V. Kumar, M.S., M.Ch. • M.V. Kumar, M.S., M.Ch.

Department of Cardiothoracic Surgery, Nizam’s Institute of Medical Sciences, Hyderabad, India

Table 25.2 Clinical features of aortic dissection

•An urgent 12-lead ECG should be performed to look for features of AMI.

•If aortic dissection is a possibility, antiplatelet, anticoagulant, and thrombolysis should be avoided.

•Chest X-ray—a routine chest radiograph is abnormal in 60% of cases with suspected aortic dissection; the commonest finding are widening of mediastinum and left-sided pleural effusion.

•D-dimer may be falsely elevated in some cases.

Step 3: Initiate treatment for suspected aortic dissection (Table 25.3)

•All patients suspected of having acute aortic syndrome should be admitted to the ICU for invasive monitoring and hemodynamic stabilization.

•Pain control with morphine should be started.

•An arterial line in the well-perfused hand should be inserted.

•Reduction of systolic blood pressure, decreasing heart rate, and diminution of the rate of rise of the left ventricular ejection time (dP/dT) are the goals of the primary medical treatment.

•Beta-blockers (labetalol and esmolol) as a group of drugs that have the most desirable effect in reducing the force of the left ventricular ejection (dP/dT). However, if beta-blockers alone do not control hypertension, vasodilators are ideal additional agents to control blood pressure. Because vasodilators alone can increase the left ventricular ejection, they should always be combined with beta-blockers.

•The goal of therapy is to manage the heart rate less than 70 beats/min and to keep blood pressure as low as possible without compromising organ perfusion.

•In patients with hypotension at presentation, possible volume depletion, which may be the result of blood sequestration in the false lumen, pleura, or pericardial space, has to be ruled out.

•Pericardiocentesis is usually avoided for cardiac tamponade secondary to dissection, as bleeding is recurrent. A definitive surgery is indicated in these cases.

Step 4: Perform confirmatory investigation for acute aortic dissection (Table 25.4)

•The diagnostic goal of imaging is to achieve the following:

–Confirm diagnosis.

–Classify the dissection/delineate the extent.

–Differentiate true and false lumen, localize intimal tears, and distinguish between communicating and noncommunicating dissection.

–Assess side branch involvement (including coronary arteries).

–Detect and grade aortic regurgitation.

–Detect extravasation (periaortic or mediastinal hematoma, pleural or pericardial effusion).

•Assess clinical stability (for transport), availability, and experience with the investigation before deciding on the confirmatory imaging modality.

•Because of good sensitivity and specificity, CT angiography and MRI angiography are considered current standards of evaluation.

•If the patient is hemodynamically unstable and cannot be shifted for imaging, transesophageal echocardiography can be done to confirm the diagnosis.

•Transthoracic echo has a low sensitivity and specificity especially for type B dissection.

•Coronary angiography—because the recent generation CT/MRI imaging modalities can demonstrate proximal third of coronary arteries, routine use of conventional coronary angiogram is not recommended.

Step 5: Understand types of aortic dissection and their outcome (Fig. 25.1)

•Aortic dissection refers to formation of a tear in aortic intima, directly exposing the blood to the diseased medial layer and splitting the aortic wall, producing true lumen and false lumen with driving force (pulse pressure).

Fig. 25.1 Classification of aortic dissection

•The dissecting process extends antegradely but sometimes retrogradely from the site of intimal tear.

•For prognostic and therapeutic reasons, aortic dissections are classified into three major types, which share the basic principle whether the ascending aorta is involved (Fig. 25.1).

•Proximal dissection (involves ascending aorta) includes De Bakey type I and type II or Stanford type A.

•Distal dissection (spares ascending aorta) includes De Bakey type III or Stanford type B.

•For prognostic reasons, dissection has also been classified as acute or chronic depending on duration (less or more than 2 weeks).

•Recent years have brought recognition of two important variants of aortic dissection.

–Intramural hematoma (IMH)

•Aortic IMH is considered as a precursor of dissection originating from ruptured vasa vasorum in the aortic medial wall layer and resulting in an aortic wall infarct that may provoke a secondary tear, causing a classic aortic dissection. Although clinical manifestations of IMH are similar to acute aortic dissection, IMH is an imaging diagnosis in an appropriate clinical setting. Treatment is similar to classic aortic dissection.

–Penetrating aortic ulcer

•Deep ulceration of atherosclerotic plaque can lead to IMH, aortic dissection, or perforation. In association with IMH, these ulcers are seen almost exclusively with type B dissection.

•At present, these three lesions—aortic dissection, IMH, and penetrating aortic ulcers—are called acute aortic syndromes.

•Acute aortic dissection of ascending aorta (De Bakey type I and type II, Stanford type A) is highly lethal, with a mortality rate of 1–2% every hour after the onset of symptoms. Without surgery, the mortality rate exceeds 50% after 1 month.

•Uncomplicated type B (De Bakey type III) aortic dissection has a 30-day mortality of 10% and may be managed medically.

•Intramural hematoma of ascending aorta has a prognosis similar to type A dissection.

Step 6: Definitive surgery

•Type I and II (A) dissections are managed primarily by surgery.

•Type III (B) is managed conservatively, and surgery is only indicated if complications such as organ hypoperfusion, refractory hypotension, refractory pain, or aortic rupture occur.

•There is increasingly use of percutaneous endovascular stent grafting in selected cases of distal dissection.

Step 7: Identify underlying risk factors for aortic dissection

•These include hypertension, hyperlipidemia, trauma, hereditary connective tissue disorders like Marfan’s syndrome, arteritis, and cocaine use.

Step 8: Long-term follow-up and treatment

•The cornerstone of medical therapy is with beta-blockers. Excellent blood pressure control, less than 120/80 mmHg, is paramount to prevent long-term complications. Close follow-up by a specialized team includes the assessment of signs of aortic expansion, aneurysm formation, signs of leakages at anastomoses/ stent sites, and malperfusion.