Ever heard the phrase “the aorta will F#*k you up”? Well this blog will cover one aortic pathology that can do just that, the Aortic Dissection.
Sir William Osler said it best:
“The tragedies of life are largely arterial”
You are dispatched to a community access hospital to transfer a patient who had presented with an acute onset of chest pain back to your tertiary hospital.
When you arrive you are met by the patient who is just returning from radiology. The patient is a 74-year-old male with a history of hypertension who advised that while walking he developed an acute onset of chest pain, which radiated to his back, specifically between his shoulder blades. He further describes the pain as a tearing sensation. You note his vital signs to be a heart rate of 94, blood pressure of 154/70, respiratory rate of 20 and pulse ox of 97% on ambient air.
As you are packaging the patient the ER physician advises you that the patients CT scan revealed a type A aortic dissection and you discuss a treatment plan.
You receive orders for a HR goal of <60 and a systolic blood pressure of <100.
How will you proceed? What medications will you utilize?
Blood vessels are composed of three layers, the intima, media and adventitia. The inner most layer being the intima, the outer most being the adventitia with the media residing in the middle. If you were to look at a blood vessel in a cross sectional view you would notice a lumen in which blood flows through.
An aortic dissection occurs with a tear or let’s say a DISSECTION of the intimal layer Creating a pathway from blood to pass into the medial layer creating a false lumen. With the development of a the false lumen, blood will flow either antegrade or retrograde from its origin, which can result in aortic regurgitation, pericardial effusion or tamponade or end-organ malperfusion.
There are two main anatomic classifications of aortic dissection; the DeBakey coming from the famous cardiothoracic surgeon Michael DeBakey and the Standford classification system. Both of these systems differentiate aortic dissection by the area of aorta that is involved, either ascending or descending. Of the two classifications systems the Stanford classification is more commonly used due to its ease of use.
Type A: Ascending
Type B: Descending
I: Beginning in the ascending aorta but continuing till at least the aortic arch
II: Confined to the ascending aorta
III: Beginning in the descending aorta but can continue both distally and/or proximally, however not passing the left subclavian.
Differentiation of Type A and B aortic dissections is important as types A dissections managed surgically whereas type B dissections are traditionally managed medically. Type A aortic dissections are a surgical emergency and surgical management is the gold standard with mortality increasing 1-2% per hour, leading to a 50% mortality rate at 48 hours without surgery.
So why are Type A dissections going to the operating room and Type B dissections being admitted to the ICU?
Type A dissections are a surgical emergency and operative repair is the gold standard due to their higher risk of mortality secondary to their complications such as MI, stroke and cardiac tamponade. Mortality increases by 1-2% each hour, leading to a 50% mortality rate at 48 hours.
Type B dissection on the other hand are usually managed medically with endovascular repair being taken in patients with malperfusion or dissection of expansion.
Incidence & Risk Factors:
The incidence of aortic dissection is approximately 3 per every 100,000. Aortic dissection is most common in men between the ages of 60-80.
- Cocaine orMethamphetamine Use
- Connective Tissue Disorders
- Marfan Syndrome
- Ehlers-Danlos Syndrome
- Aortic Instrumentation or surgery
- Vasculitis secondary to Inflammatory disease
- Giant Cell Arteritis
- Rheumatoid Arthritis
- Family History
We all know the textbook picture of aortic dissection, a sudden onset chest or back pain that is described as ripping or tearing.
The hallmark presentation of aortic dissection is an abrupt onset of sharp pain that is described as ripping or tearing located to the chest or back. Chest pain is a more common presentation in patients experiencing type A dissections, whereas back and abdominal pain is more common in type B dissections.
While hypertension is an associated risk factor of aortic dissection it is important to note that most type B dissections will present hypertensive whereas type A dissections will be hypotensive.
A number of other clinical signs and symptoms that may present with an aortic dissection are syncope, abdominal pain, neurological deficits, cardiac tamponade, nausea and vomiting.
While physical examination is imperative it is important to note that specific physical exam findings are found in less than 50% of patients with aortic dissection.
Physical examination findings associated with aortic dissection:
- Diminished or absent pulses
- Pulse deficit
- New Murmur
- Blood pressure differential (>20mmHg)
The gold standard for diagnosis of aortic dissection is CT angiography, so unless you are working in a mobile stroke CT ambulance that won’t be an option. So our presumptive diagnosis of aortic dissection will be based on history and physical exam in the prehospital setting.
Point of care ultrasound can be helpful in the diagnosis of aortic dissection, as well as the diagnosis of other pathologies related to aortic dissection , such as pericardial effusion or aortic regurgitation.
Examination of the descending aorta using the abdominal short view, can aide in the diagnosis of type B dissection by visualization of a intimal dissection flap. Type A dissection are more difficult to diagnosis, using POCUS, however this can be done utilizing a parasternal long axis or suprasternal notch view.
Initial management aims at controlling pain, heart rate and blood pressure for both type A and B dissections.
Controlling a patients pain through the use of narcotic analgesics such as fentanyl can assist in decreasing heart rate and inotropy by decreasing the release of endogenous catecholamines experienced with pain. By decreasing both heart rate and blood pressure it will decrease the shear forces being placed on the intimal wall as well as expansion of the dissection and the risk of aortic rupture.
Consider the heart rate as a mallett that is pushing blood through the aorta and a wedge has been placed at the site of the dissection. With each beat, the mallett swings, propelling the blood against the wedge, driving it into the dissection. Using this analogy you can see why it is important to reduce both heart rate as well a blood pressure. As the heart rate is decreased, the fewer the amount of times the malett strikes the wedge, further driving it into the dissection.
Control of heart rate and blood pressure is best accomplished with a beta blocker such as Esmolol, as it will decrease heart rate, inotropy and blood pressure. While Calcium Channel Blockers can be utilized as a second line agent to control blood pressure, they should not be used initially as they can cause a reflex tachycardia resulting in increased aortic wall stress.
HR & BP Goals:
There has been no specific blood pressure or heart rate goal that has shown a reduction in morbidity or mortality, though most recommend a systolic blood pressure <100-110 mmHg and a heart rate <60.
A radial arterial line is placed for continuous blood pressure monitoring and your patient is packaged for transport. You administer Fentanyl and administer a loading dose of Esmolol and initiate an infusion. During your 45 minute flight you titrate up the Esmolol and shortly after, her HR and blood pressure goal are met. You administer a second dose of Fentanyl just prior to your arrival. She is taken directly to the operating room. Upon follow up you learn the patient had a succesfful repair of her aortic dissection.
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