SPONTANEOUS CORONARY ARTERY DISSECTION (SCAD)
The heart is a great muscle pump that ensures blood circulation throughout the body. It's the engine of life.
This muscle uses oxygen delivered by "pipes" that are called coronary arteries. These arteries course over and penetrate the heart supplying oxygen-rich blood. Their diameter varies between 2 and 4 mm.
Any disease that alters the diameter of these arteries may compromise the function of the heart and sometimes affect it permanently.
READ: "Oxygenation of the heart and its blood circulation"
Three main types of obstacles
Three types of acute changes can create obstacles to coronary circulation. All three initiate in the muscle layer of the blood vessel, the media:
Coronary artery spasm, spontaneous or induced by a substance such as cocaine.
A coronary spasm is the contraction of the muscular layer of the media, which strangles the vessel.
The consequences of this constriction will depend on the importance of the spasm, that is to say, the complete or partial closure of the artery and how long the artery remains in spasm.
Dissection or spontaneous tearing of the media. The cause of this occurrence is not yet well known, but it is believed to be associated with an inherent anomaly of the media.
The consequences will depend, once again, on the importance of the internal tearing of the vessel, and whether there is a full or partial obstruction of the artery.
Atheromatous plaque rupture. Better known as the rupture of a cholesterol plaque, this is by far the most common cause of impaired coronary circulation.
Let's take a closer look at arterial dissection or spontaneous tearing of the media.
What is a Spontaneous Coronary Artery Dissection or SCAD?
A SCAD is, as the name implies, a tear in the wall of a coronary artery that occurs suddenly without any identified cause.
Components of an artery
2 main coronary arteries deliver blood to the heart.
These coronary arteries and all other arteries of the heart are made up of 3 layers: the intima, media, and adventitia.
•Intima, the inside layer
The innermost tunica or layer, the intima, consists of a smooth surface that may be compared to a layer of Teflon. It is responsible for maintaining the vessel in good working order and protects it from blood clot formation.
•Media, the middle layer
The middle layer or media is thicker and contains smooth muscular cells. It enables the artery to contract and dilate.
•Adventitia, the outer layer
The adventitia is the outer covering layer. It is the most resistant part of the artery. It provides added protection to the vessel.
A tear occurs
A tear may occur; it will be set in the muscle layer only, thus confined inside the coronary wall. This tear causes bleeding into the media.
Depending on the extent of the bleeding, the build-up of blood causes a bulge inside the vessel. A partial or full blockage of the blood flow ensues.
The dissection can include the fine interior layer of the vessel, the intima. In such a case, blood can seep into the wall of the vessel and tear it further.
And as if that were not enough!
Another process that may come to aggravate the SCAD, that of the formation of a thrombus, or more precisely a blood clot, at the arterial breakage site.
When the artery wall tears and exposes its inner components, the body initiates a process to close the breach. This is when blood platelets go into action.
It's a wake-up call for blood platelets
Platelets are tiny particles of cells that are found in the blood. More specifically, they are minuscule fragments of large cells found in the bone marrow. They play an important role in blood coagulation, the process by which blood changes from a fluid to a gel, forming a clot.
Understanding blood coagulation
When we cut ourselves, our wound bleeds. The blood flows out because there is a breach in the blood vessels. Our body sends an alarm signal because the breach needs to be covered or closed.
This is what blood coagulation is all about.
Thrombocytes or blood platelets are the first cells to go into action. On contact with elements under the thin layer of the intima vessel, the platelets change shape, produce tentacles, and clump together. They form the primary structure of a blood clot.
Platelets also release chemicals that attract other platelets; the coagulation process is activated, transforming certain blood proteins into long, thin filaments.
The accumulation of these fine filaments around platelets and the captive red blood cells forms a net that serves to further solidify the blood clot, which is now hermetically closed.
Partial or full obstruction
Whether the tear is within the coronary wall or includes the intima or not, the accumulation of blood in the arterial wall, with or without the formation of a clot in a coronary artery, can cause either of the following 2 situations: a partial or full obstruction in the vessel.
At the clinical level, these conditions can lead to a non-ST-Elevated Myocardial Infarction (NSTEMI) or an ST-Elevated Myocardial Infarction (STEMI).
Who is at risk?
According to medical records, about 1 to 4% of myocardial infarctions and 0.5% of cardiac arrests are caused by Spontaneous Coronary Artery Dissection (SCAD). Nearly 90% of cases affect women between 40 and 55 years of age.
What are the potential causes and risk factors for SCAD?
SCAD is not caused by atherosclerotic plaques. The precise source of this affection is still unclear. In more than 20% of cases, we do not know how this affection came to exist.
Here's what we know about some of the conditions that can lead to SCAD:
Fibromuscular Dysplasia (FMD): this is a condition, that is to say, a disease of the vascular muscle tissue itself. Blood vessels are abnormal throughout the body with areas of vessels that narrow and dilate. It most commonly affects blood vessels in the heart, the head, the neck, and the kidneys. This condition has been found in more than 60 % of SCAD patients.
Pregnancy: SCAD can occur during the pregnancy period or right after giving birth. It is more common in women who had more than one pregnancy or have given birth multiple times.
Emotional and physical stress: patients with SCAD have higher rates of physical and emotional stressors. For example, the loss of a loved one, a job, a relationship that ended, work stress, etc.
The following predisposing factors are worth considering:
certain connective tissue disorders, involving elements between the cells, namely the Marfan and Ehlers-Danos syndromes, among others,
a hereditary character was raised. Some mutations in the genetic code are under study,
hormonal estrogen therapy is also suspected, but no clinical evidence was found as yet.
SCAD may be precipitated in patients with fragile arteries. It may also be attributable to the following:
- severe emotional or physical stress,
- strenuous exercise,
- the use of stimulants such as cocaine, for instance.
What are the symptoms?
Symptoms of spontaneous coronary artery dissection are very similar to those experienced in a coronary plaque rupture injury.
The sudden onset of chest pain can be described as chest discomfort with or without extension to:
- the neck,
- the jaw,
- the left arm.
The pain can also bring on arrhythmia or a heart attack.
Why is there a similarity between symptoms?
Symptoms that characterize a coronary event due to a cholesterol plaque rupture, Acute Coronary Syndrome (ACS), and SCAD symptoms, are very much alike as they share the same origin: a blood circulation restriction or blockage.
This is how it is understandable that there may be some hesitation in arriving at a diagnosis between either a spontaneous dissection or a cholesterol plaque rupture.
How is a diagnosis established?
SCAD should be suspected in a patient presenting with a heart attack, who...
has no risk factors for atherosclerotic coronary artery disease,
is fairly young, under the age of 50,
has experienced severe physical or emotional stress,
has health problems that predispose him to SCAD.
Variations or changes may be seen on the electrocardiogram and at times on the echocardiographic exam (heart ultrasound) as well.
Blood proteins released from damaged heart muscle (Troponin) are also increased. However, the definitive diagnosis can only be established by coronary angiography, which allows attending specialists to directly visualize the coronary arteries.
A conservative approach is often preferred, that is to say, doctors will simply observe the clinical evolution because the arteries do tend to heal on their own with time.
For the sake of accuracy, conservative treatment is a medical therapy meant to avoid the patient being subjected to invasive measures such as a catheter intervention and similar procedures.
It is advisable to avoid using coronary stents to treat the artery since blood vessels are fragile and there is a risk of causing the dissection to extend further.
Medications are given to slow down the heart rate and lower blood pressure, to help the healing process. An antiplatelet agent may be used, but until now no clinical benefit was evidenced.
Generally speaking, full healing of the coronary artery may be expected after 3 months in 95% of the patients.
If symptoms persist despite conservative treatment or if the patient's condition worsens, then coronary angioplasty with or without stents is sometimes tried, with mixed results because some artery tears are very extensive.
Resorting to cardiac surgery very rarely happens, but at times it is necessary to do so.
What tests can be expected?
Some of the first tests that are ordered when evaluating chest pain include a blood test, an electrocardiogram (ECG), and a chest X-ray.
Transthoracic echocardiography allows us to see the impact on SCAD’S cardiac muscle function.
Coronary angiography confirms the diagnosis by showing the breakage of the coronary wall and its impact on the blood flow within it.
Recent medical articles suggest the need for CT scans of the neck, chest, and abdomen to screen for fibromuscular dysplasia.
Can a dissection recur?
In the largest medical studies regarding SCAD, a recurrence in less than 3% of patients in 3 years has been described.
After an episode of coronary dissection, the patient should conscientiously follow his attending specialist's advice and instructions.
What to do after a spontaneous coronary dissection?
Keep blood pressure normal-low normal.
Beta-blockers will be prescribed to reduce shear stress on the patient’s arteries (the force that blood applies to arteries with each heartbeat).
Patient should engage in moderate-intensity exercise, which should include the following weight restrictions: 30 lbs for women and 50 lbs for men.
Future pregnancies are to be avoided because SCAD can recur in up to 14% of patients who become pregnant. (Second-tier studies.)
Participation in a cardiac rehabilitation program is considered beneficial and allows a patient to start light to moderate exercise safely.
A psychological support program is recommended if the patient feels the need for it, as SCAD can be an overwhelming experience.
Driving a car
Driving depends on the extent of cardiac damage and the class of driver to which it is directed. This issue will be discussed with the patient's doctor.
In some provinces, it could be described as follows.
After a STEMI- type myocardial infarction, driving unfortunately has some constraints. It is generally recommended that driving not be resumed until 1 month after the cardiac event.
In the case of commercial driving (bus and truck drivers, and similar category vehicles): this recommendation is further extended to 3 months, starting from the day of hospital discharge.
For smaller infarcts of the NSTEMI type, which only required a period of observation and a non-urgent coronary intervention, driving may be resumed as early as 48 hours after the cardiac intervention. However, an ultrasound study will be needed, to confirm minimal damage to the heart.
In the case of commercial driving, the patient will have to wait up to 7 days before resuming driving. Several other recommendations exist in other situations: for example, a small infarction without arterial intervention, absence of valvular or arrhythmic complications, and so forth.
It is wise for the patient to refer to his cardiologist for his professional opinion as to the delay to be respected before driving again.
Doctors do not automatically report to the SAAQ when this or that patient just had a heart attack.
It all depends on the patient's willingness to comply with the medical recommendations he received.
Such is the law in several provinces
However, if the patient, unfortunately, causes an accident due to a symptom or a cardiac complication while driving during the time that it was not recommended for him to do so, the patient could be held responsible for the outcome of the accident, having put his life and that of others at risk.
What is the recommended follow-up?
A medical follow-up with a healthcare provider is necessary after a SCAD.
A long-term follow-up with a cardiologist is warranted because this is a relatively new disease, and health professionals have so much to learn about it still. The schedule will depend on the clinical presentation and the severity of the dissection.