| On October 25, 1760, George II, then 76, rose at his normal hour of 6 am, called as usual for his chocolate, and repaired to the closet-stool. The German valet de chamber heard a noise, memorably described as “louder than the royal wind,” and then a groan; he ran in and found the King lying on the floor, having cut his face in falling. Mr. Andrews, surgeon to the household, was called and bled His Majesty but in vain, as no sign of life was observed from the time of his fall. At necropsy the next day, Dr. Nicholls, physician to his late Majesty, found the pericardium distended with a pint of coagulated blood, probably from an orifice in the right ventricle, and a transverse fissure on the inner side of the ascending aorta 3.75 cm long, through which blood had recently passed in its external coat to form a raised ecchymosis, this appearance being interpreted as an incipient aneurysm of the aorta. |
Anatomy of a Dissection
Like any reliable high pressure hose, our arteries are made up of layers.
- The intima, or inside layer, is in ‘intimate’ contact with the circulating blood.
- The media, or middle layer, is made up of smooth muscle cells and elastic fibers that allows the artery to expand and contract, thus propagating the pulsatile flow of blood.
- The adventitia, or outer layer, is made up of strong connective tissue to help control over distention.
An arterial dissection occurs through a tear in the intima, allowing the blood to dissect or open the space between the intima and the outer layers. This most commonly occurs in the ascending aorta, which receives the initial force of ejected blood from the left ventricle into the circulatory plumbing.
This high pressure ejection is repeated an average of 70 times a minute, 4200 times an hour, and over 100,000 times a day. It’s amazing that dissections don’t happen more often. The separation occurs less frequently in the descending aorta due to a straighter pipe and less applied pressure. A dissection is not a ‘true’ aneurysm, which is a bulge or weak area involving all three layers of an artery. True aneurysms are more common in the abdominal aorta.
Presenting signs and symptoms of an aortic dissection are varied. The aorta’s anatomy provides some insight as to why this is so. The aorta is a large cane-shaped artery consisting of ascending, descending and abdominal segments. It receives the blood pumped from the left ventricle for body wide distribution. Aortic branch arteries in the chest include the:
- coronary arteries that supply the heart muscle
- innominate artery that splits into the right subclavian supplying the right arm and the right carotid artery supplying the brain
- left common carotid supplying the brain
- left subclavian supplying the left arm
If a dissection blocks flow to one or more of these branch arteries, the patient may present with signs and symptoms of a myocardial infarct or cardiac tamponade or a stroke or decreased circulation to one or both upper extremities or even a combination of any of these presentations. Makes it a little difficult, doesn’t it?
Take Home Message
When treating the patient presenting with chest pain, make it a habit to run through your list of potential non-cardiac causes — this includes aortic dissection. Although dissections are relatively uncommon (an estimated five to 30 per one million people versus 4400 per one million for myocardial infarction), using blood thinners and clot busters for treatment of chest pain, thought to be an acute coronary syndrome, can be devastating for a patient with an aortic dissection.
Here are some clues to help make you suspicious of an aortic dissection:
— Patients experiencing dissection pain more often describe it as a sharp pain with a sudden onset, and less frequently as the classically taught “tearing” or “ripping” pain.
— Older age and hypertension increase the risk for a dissection.
— Younger folks at risk for a tear in the intima include those with a connective tissue disease, such as Marfan’s Syndrome, or an inflammatory disease of the blood vessels (arteritis).
— At any age, a previous history of surgery involving the heart or aorta increases the risk of a dissection.
— On exam you may find a difference between the radial pulse and/or blood pressure between the arms (if you check!). Be sure to relay your findings to the receiving facility. They may not get to that bilateral blood pressure or pulse check or the patient may not be as able to provide the vital historical information you have already collected.
So What About George?
George had a few of the risk factors and some of the symptoms of a dissecting aneurysm or aortic dissection: older age (nowadays age 60-70), male gender, pain (groan from the toilet facility), and syncope or fainting, which may indicate cardiac tamponade or stroke caused by aortic dissection and a worse outcome (death) — as it was in George’s case.
For those who do survive the initial separation, they can benefit from your expertise if you remember to consider dissection for any patient complaining of chest pain. Doing so can help prevent you from missing an opportunity to help your patient.
References
- Hagan PG, Nienaber CA, Isselbacher EM, et al. The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. JAMA 2000;283:897-903.
- Bushnell J, Brown J. Clinical Assessment for Acute Thoracic Aortic Dissection. Ann Emerg Med. 2005;46:90-92.
- Nallamothu BK, Mehta RH, Saint S, et al. Syncope in Acute Aortic Dissection: Diagnostic, Prognostic, and Clinical Implication. Am J Med. 2002;113:468-471.
- von Kedolitsch Y, Schwartz AG, Nienaber, CA. Clinical Prediction of Acute Aortic Dissection. Arch Intern Med. 2000;160:2977-2982.