Definitions

 

Pericardium: Is a double-walled sac containing the heart and the roots of the great vessels. The pericardial sac has two layers, a serous layer and a fibrous layer.

 

Aorta: Is the biggest artery in the body that delivers oxygenated blood all throughout the body

 

Adventitia: The exterior layer of the aorta

 

Media: The middle layer of the aorta (one of the layers of the propagation)

 

Intima: The inner layer of the aorta (one of the layers of the propagation)

 

Lumen: The hollow inside of the aorta that the blood flows through

 

False Lumen: The blood contained in the propagation

 

Aortic Dissection (General Definition): This is a separation and tear in the median layer of the largest artery coming out of the heart called the aorta. Blood has the potential to build up in the separated layers of the artery, which can be detrimental to blood flow.

• Commonly during the ages of 50-65 years of age; more common in males than females

• Connective tissue disorder patients are more in risk in 20-40 years of age

• Most common sites of dissection occur either 2 centimeters above the aortic root (Type A) and just after the left subclavian artery (Type B)

  • Symptoms:

    • Sudden, severe central chest pain

    • Sweating

    • Nausea

    • Shortness of breath

    • Weakness

    • Syncope or Aka fainting

  • Diagnosis:

    • Transesophageal Echocardiogram (TEE)

      • Quick and cheap but can not see anything past the aortic valve and the thoracic aorta

    • Computerised Tomography Scan (CT) with iodide contrast

      • Best way of identifying and most used

      • Can see the entire aorta

    • Magnetic Resonance Angiogram (MRA)

      • 100% sensitive and specific

 

Connective Tissue Disease

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Marfan Syndrome: Is a genetic disorder that affects the body's connective tissue. Connective tissue holds all the body's cells, organs and tissue together. It also plays an important role in helping the body grow and develop properly.

 

Ehlers-Danlos Syndrome: Is a group of disorders that affect connective tissues supporting the skin, bones, blood vessels, and many other organs and tissues. Defects in connective tissues cause the signs and symptoms of these conditions, which range from mildly loose joints to life-threatening complications.

 

Stanford Classification

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Type A: Is a tear in the ascending aorta and/or arch before the origin of the left subclavian artery.

• 60% of aortic Dissections are Type A

• Requires immediate surgical treatment

• Blood is more turbulent in the beginning section due to the curve of the initial part of the aorta 

 

Type B: Is a tear in the aorta beyond the left subclavian artery and/or brachiocephalic vessels possibly extending downward.

• 40% of aortic dissections are Type B

• Is either operated on or medially treated through blood pressure control

 

DeBakey Classification

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Type I: Involves the ascending and descending aorta (Stanford Type A)

 

Type II: Involves only the ascending aorta (Stanford Type A)

 

Type III: Involves only the descending aorta after the origin of the left subclavian artery (Stanford Type B)

 

Malperfusion: The loss of blood supply to a vital organ caused by branch arterial obstruction secondary to the dissection

 

Hypertension: High blood pressure (more than 130/80)

 

Hypotension: Low blood pressure (less than 90/60)

 

Shock: An acute medical condition associated with a fall in blood pressure, caused by such events as loss of blood, severe burns, bacterial infection, allergic reaction, or sudden emotional stress, and marked by cold, pallid skin, irregular breathing, rapid pulse, and dilated pupils.

 

Trauma: Physical injuries of sudden onset and severity which require immediate medical attention. The insult may cause systemic shock called “shock trauma”, and may require immediate resuscitation and interventions to save life and limb.

 

Aneurysm: Weakening and bulging out of the wall of the aorta

 

Propagation: The tear in the artery in between the intima and media where the blood flows into the false lumen from the dissection

 

 

The Natural History of Aortic Dissections

What is an Aortic Dissection?

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It is widely regarded in cardiothoracic surgery as one of the deadliest diseases known to man; killing nearly ¼ patients that are diagnosed. Even if the patient is diagnosed early, the six-hour long surgery and rigorous operation cause many surgeons to turn away such cases. What exactly is the disease that is so difficult that many ordinary cardiac surgeons avoid it at all costs? An Aortic Dissection is a tear in the inner layer of the largest blood vessel in the body coming off the heart called the aorta. This tear separates the walls of the aorta called the intima and the media, the first two layers from within the lumen of the aorta. This tear will cause the escape and build up of valuable, oxygenated, blood cells into a false lumen in between the 2 layers. Sadly, once this tear has been obtained it has the potential to spread down the length of the aorta as far down as possible. Causing the loss of even more blood cells. Which also means some vital organs are not getting enough blood to live and function properly, thus eventually causing the patient to die. The aorta is the biggest artery in the body that delivers oxygenated blood away from the heart and to the head, neck, chest, arms, abdomen, and legs. Clearly, a tear in this part of the heart is devastating to the circulatory system.

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The causes of this tear lead back to six main malfunctions of the hearts operations. The first and most common is chronic hypertension. This high blood pressure is found in over ⅔ of aortic dissection cases and occurs due to the excessive stress and degeneration of the aorta that takes place. Another possible cause is the appearance of other conditions such as Marfan Syndrome, which is a genetic disorder that affects the body's connective tissue. Connective tissue holds all the body's cells, organs and tissue together. It also plays an important role in helping the body grow and develop properly. Or Ehlers-Danlos Syndrome, which is a group of disorders that affect connective tissues supporting the skin, bones, blood vessels, and many other organs and tissues. These defects in connective tissues cause the signs and symptoms of these conditions, which range from mildly loose joints to life-threatening complications. A preexisting aneurysm can also weaken the wall of the aorta, causing a sort of bulging which can increase the chances of an aortic dissection to occur. Next, any sort of chest trauma will also make an individual more susceptible to the disease.  And lastly, gender and age play a huge role. Men are 2 or 3 times more likely to get an aortic dissection compared to women, and as the ages of 50-65 come around humans tend to have this disease be commonplace.  

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However, once the aortic dissection is diagnosed there are a few more hurdles that surgeons have to address. The first issue is identifying the type of tear the patient has endured. There are two types of tears that can occur called a Type A and Type B. Type A tears are on the first few centimeters of the ascending portion of the aorta and requires immediate surgery to fix. On the other hand, a Type B tear is a bit more risky to operate on. This is because a Type B tear occurs on the second half of the aorta which can knock off branches leading to the brain and the lower half of the body. If this occurs there are chances for strokes, dead gut ( a loss of blood flow to the intestines can damage intestinal tissue and possibly lead to death), and loss of circulation to limbs. This is what is referred to as the Stanford classification system. The other classification is called the DeBakey classification. In the DeBakey system the Type I involves the ascending and descending aorta. This is the same as the Stanford Type A. Next is the Type II which involves only the ascending aorta. This also pertains to parts of the Stanford Type A. Lastly there is the Type III, and this involves only the descending aorta after the origin of the left subclavian artery. The Type III is best related to the Stanford Type B.

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What can help with identifying and classifying the tear usually comes from the patient's symptoms and the signs the practitioner observes. Symptoms such as sudden/severe central chest pain, sweating, nausea, shortness of breath, weakness, and syncope (fainting) are sure giveaways that the patient might have an aortic dissection. And once the definite signs have been observed through definitive testing, a surgeon should be able to determine if he or she should operate on the heart or wait and fix the other part of the body that is a more pressing issue first. This can be determined with either a Computerised Tomography Scan (CT) with iodide contrast, a Transesophageal Echocardiogram (TEE), or a Magnetic Resonance Angiogram (MRA). These allos for a more thorough understanding of the characteristics of the tear, the effects of the tear, the patient's condition, and the seriousness of the effects of the tear. That way more time, money, and lives can be saved.  

 

What is a Natural History?

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A Natural history, in terms of diseases, is the fundamental course of progression of disease prior to its inception, through the presymptomatic phase, through all the clinical stages, and until the point of either a cure or death. What makes it natural is the absence of any sort of treatment. Meaning that there are no external countermeasures acting on the body. The creation of this concept dates back to studies in the ancient Greco-Roman world and the medieval Arabic world, through to European Renaissance naturalists. Today's natural history is across many sciences. Some versions of natural history focus directly on the observation of organisms in their environment during the past and the present. A person who studied the natural history of an organism is known as a naturalist. Their main objective is to study, understand and spread the knowledge they gain with the world by observing plants and animals directly.

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The thought of something so ancient being used in today's medicine must seem obscene. But the importance if understanding what happens to the body when it is experiencing some sort of disease or trauma is critical to the treatment of these issues. The body can face attacks from an almost unlimited amount of threats. Getting to know how these threats affect the body is the key to discovering how to treat them as well. Any cure or treatment for a disease in the past has been done post observing and understanding the natural history of that specific disease. This allows medical professional the ability to know exactly what to fix and possibly how to fix it.

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The Natural History of Aortic Dissections?

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Aortic Dissections are one of the biggest killers in the field of cardiac surgery. Between the two classifications, approximately 62% of all aortic dissections are Type A and approximately 38% of all aortic dissections are Type B. Left untreated the mortality rate over the span of a week is over 60%. The rate of death varies between 1-3% per hour. Within 24 hours about 21 % do not survive, within 48 hours 38 % do not survive, and within 1 week 62 % of people do not survive, and within 2 weeks 74% of people do not survive. Even if a patient survives these timestamps and becomes a chronic aortic dissection patient, the survival rate over a 5 year time period is only 10-15%. These numbers all lead to one conclusion regarding the disease as a whole. That without any form of treatment a patient will die. And if they are not given the correct or best treatment, they may have prolonged lives but they will not survive very long. Sadly even with the best possible treatment the patients will be under constant medical monitoring and will most likely never live the same life as before.

 

The Natural History of Type A Aortic Dissections

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With 62% of all aortic dissections being of the Type A classification there are a few differences in its natural history compared to a Type B. Type A aortic dissections pertain to a tear that starts at the ascending portion of the aorta. A tear that begins at the ascending aorta but extends beyond that point or all the way down is still considered a Type A dissection. This classification of aortic dissection is considered to be the most dangerous of all. Symptoms of Type A aortic dissection are anterior thoracic pain in 85% of cases, and/or back pain in 46% of cases, abdominal pain in 22% of cases, syncope in 13% of cases, and stroke in 6% of cases. These dissections are always operated on no matter what the situation is. This is solely because of the causes of this tear. The ascending portion of the aorta comes vertically out of the heart and curves to the left of the body and runs the length of the spine. This sudden turn that coming out of the heart is what causes all the issues. Due to the immense pressure, the heart can create over the course of years, that one bend turns into a sort of wall for the pressurized blood. With every beat a pressurized amount of blood pounds at the inside of the aortic walls intima. And just like the erosion of rock the intima wall will eventually give and blood will puncture the intima and split the media of the vessel. This causes a dissection in the aorta where blood pools into a false lumen. Over time this false lumen can grow and burst. If there is a rupture in the aortic dissection, then the blood will fill the pericardium and surround the heart. Once the heart is surrounded with enough blood the pressure will cause a sort of suffocation and prohibit the heart from beating, which will eventually kill the patient. 

 

The Natural History of Type B Aortic Dissections

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On the other hand, 38% of all aortic dissections are the Type B classification. These also have a few differences in its natural history compared to a Type A. Type B aortic dissections pertain to a tear that starts beyond the ascending aorta and can extend all the way down the length of the aorta. Symptoms are sudden initial pain located in the back in 64% of cases, and in the abdomen in 43% of cases. Cerebrovascular accidents and syncope are less frequent in this type of tear. However, 12% of type B dissections presented hypotension or shock, there is a periaortic hematoma in 19% of cases, and arterial vessel disease with bad perfusion in 22% of cases. Compared to a Type A aortic dissection, Type Bs are a lot less lethal. These tears usually are looked at by cardiologists and/or surgeons and decided not to be operated on. This is due to the fact that Type B aortic dissections tend to affect other parts of the body. Namely, it can cut off circulation to the brain, limbs, stomach, and other parts of the body. In these situations, doctors will wait to see what the real issue is. This is done to avoid operating on the aorta when other parts of the body are in need of medical attention first. The complications that usually appear are coma/altered consciousness in 58% of cases, hypotension/shock/tamponade in 47% of cases, mesenteric or limb ischemia in 28% of cases, periaortic hematoma in 26% of cases, acute renal failure in 22% of cases, and mediastinal enlargement  in 16% of cases. For example, a surgeon could be conducting the 6-hour operation on the patient when all of a sudden one of his legs turns pale due to loss of circulation, the kidneys could cease to work due to loss of circulation, or the patient could endure a stroke. All of these things show a sign that there were other damages elsewhere on the body that needs attention before the dissection. And addressing the wrong part of the body first can result in an avoidable loss of life.

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However, Type B dissections also have the potential to be relatively harmless. Sometimes it is possible for the dissection to cause 2 other types of tears. One can be from within the false lumen, but reentering the true lumen. In this situation, the aortic dissection is left alone and monitored closely because the false lumen is now returning blood flow back to the true lumen and there is no real risk. On the other hand, the second tear can be outward into the body. This will cause internal bleeding and if not treated will result in the death of the patient. Showing that even waiting is sometimes a risk. This is one of the many reasons why treating this condition is so difficult. Even before the grueling 6 hours long, extremely complicated, surgery. 

 

Conclusion- Best Treatment

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To conclude, understanding what truly happens to the body when it is experiencing an aortic dissection, with no medical countermeasures, can be extremely valuable. The true danger of the disease is exposed and those who serve to save the lives of others will understand what it is that they are fighting. Building from the natural history is what allowed the pioneers in the field to advance medicine to the point it is today. Understanding the fundamentals and forging a new path is what was needed in the past and it is what will be needed in the future to allow for the success rates to become higher, the surgeries to get shorter, and for the operations to become more efficient. However, from this point forward what must be done is to utilize the tools and knowledge we have today to save as many lives as possible. This means identifying the symptoms listed above as early as possible, interpreting the signs more accurately and quickly, and performing any surgeries necessary to correct the disease. If any of the symptoms listed above are felt, immediately take the patient to a hospital. Have the patient explain his or her symptoms to the best of their ability to the doctor. Then allow for any tests that have been recommended  to occur. Preferably a CT scan because it is the gold standard for identifying aortic dissections. There are other tests like the TEE and the MRA, but both are less accurate and reliable compared to the CT scan. Even if it is more expensive or might take more time, it is worth the extra effort to get more accurate results on such a life-threatening condition. Getting these tests can be the difference between early detection of the disease or death.

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After the aortic dissection is identified and classified, the best course of treatment is what the surgeon recommends. The surgeon will operate on the aorta or on another part of the body first depending on the classification of that specific tear. This is done so the part of the body that needs the most urgent attention will be dealt with first and that does not always have to be the aorta. Usually one of of these many procedures named next are performed. Local fenestration procedure, transthoracic fenestration technique, insertion of an aortic valve and separate ascending aortic grafts, compositive valve graft, bentall  technique, button technique, cabrol method, elephant trunk procedure, homograft or pulmonary autografts, repairs of the distal aorta combined with repairs of the proximal aorta, descending thoracic aorta replacement, thoraco-abdominal aortic repair, second stage elephant trunk procedure, glue aortoplasty, sutureless intraluminal grafts, cylinder-type balloon catheters,  or intraluminal sutureless prothesis. And if any of those seem to fail there are other procedures that can be done as a last resort. Such as a repair of the distal aorta combined with repairs of the proximal aorta through the left chest, descending thoracic aorta replacement, thoraco-abdominal aortic repair, or a second stage elephant trunk procedure. Once all the surgical measures are completed, allow for time to recover before getting back into a working lifestyle. The key to stopping an aortic dissection from reoccurring or even completely avoiding the development of one is to keep low blood pressure. The best source of treatment for any disease is the prevention of that disease. Because even once an aortic dissection has been treated the mortality rate for in-hospital aortic dissection patients is 27%. So it is critical to do everything in one's power to prevent and avoid getting an aortic dissection. This is can include and not be limited to losing extra pounds, watching waistline size, exercising regularly, eating a healthy diet, reducing sodium in the diet, limiting alcohol consumption, quitting smoking, reduce caffeine consumption, reducing stress, and constantly monitoring the blood pressure at home in tandem with frequent visits to the doctor. These things will not guarantee a low blood pressure and completely avoiding an aortic dissection but, it will go a long way in bettering health and hopefully prolonging lives.

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Work Cited

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Berent, Robert, et al. “Aortic Dissection: Incidence, Natural History and Impact of Surgery.” Research Gate, Research Gate, Jan. 2000, www.researchgate.net/publication/242746609_Aortic_Dissection_Incidence_Natural_History_and_Impact_of_Surgery.

 

Cheng, Stephen W.K. “What Is the Natural History of Aortic Dissection?” Ucsfcme.com, UCSFCME, 7 Apr. 2011, www.ucsfcme.com/2011/slides/MSU11003/27ChengWhatIsTheNaturalHistoryOfAorticDissection.pdf.

 

Cherry, Kenneth J, and Michael D Drake. “ Comprehensive Vascular and Endovascular Surgery (Second Edition).” Aortic Dissection - an Overview | ScienceDirect Topics, Science Direct, 2009, www.sciencedirect.com/topics/medicine-and-dentistry/aortic-dissection.

 

D'Souza, Donna, and Daniel J Bell. “DeBakey Classification | Radiology Reference Article.” Radiopaedia Blog RSS, Radiopaedia.org, 2014, radiopaedia.org/articles/debakey-classification?lang=us.

 

D'Souza, Donna, and Daniel J Bell. “Stanford Classification of Aortic Dissection | Radiology Reference Article.” Radiopaedia Blog RSS, Radiopaedia.org, 2014, radiopaedia.org/articles/stanford-classification-of-aortic-dissection-1?lang=us.

 

Hoffman, Matthew. “The Aorta (Human Anatomy): Picture, Function, Location, and Conditions.” WebMD, WebMD, 2013, www.webmd.com/heart/picture-of-the-aorta#1.

 

Jewell, Nicholas P. “Natural history of diseases: Statistical designs and issues.” Clinical pharmacology and therapeutics vol. 100,4 (2016): 353-61. doi:10.1002/cpt.423

 

Masip, Arturo Evangelista. “Natural History and Therapeutic Management of Acute Aortic Syndrome.” Revista Española De Cardiología, Masip, 1 July 2004, www.revespcardiol.org/en/natural-history-and-therapeutic-management/articulo/13064218/.

 

Mayo Clinic Staff. “10 Drug-Free Ways to Control High Blood Pressure.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 9 Jan. 2019, www.mayoclinic.org/diseases-conditions/high-blood-pressure/in-depth/high-blood-pressure/art-20046974.

 

Punwani, Vishal, director. What Is an Aortic Dissection?Khan Academy, Khan Academy, 2014, www.khanacademy.org/science/health-and-medicine/circulatory-system-diseases/aortic-dissection-and-aneurysm/v/what-is-aortic-dissection.