What is Spontaneous Coronary Artery Dissection?
Also referred to as SCAD, spontaneous coronary artery dissection is a medical condition that needs immediate attention. It represents less than one percent of heart attacks (myocardial infarction or MI) and four percent of cases of an acute coronary syndrome (an umbrella term used for diseases that decrease the blood flow to the heart). Although it occurs most commonly in females (between the ages of 45 and 55), it can also occur in males.
Why Does Spontaneous Coronary Artery Dissection Occur(SCAD)?
The coronary arteries are made of several layers and are muscular. Occasionally, a tear develops inside the coronary arteries, leading to a split between the different layers of the blood vessel. This split creates pockets in each layer of the vessels, and the blood flowing through them gets trapped within them. When this happens, the blood clots and forms an intramural hematoma (IMH), which blocks the blood flow within these blood vessels and deprives the heart tissue of oxygen and nutrients. When the heart does not have oxygen, its cells and tissues die, leading to myocardial infarction (otherwise known as MI or a heart attack).
What Are the Causes of Spontaneous Coronary Artery Dissection (SCAD)?
In most individuals, spontaneous coronary artery dissection (SCAD) is idiopathic. However, studies have established several risk factors which can precipitate its episode, such as:
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The female sex (especially postmenopausal women).
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Fibromuscular dysplasia (FMD).
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Hypertension (high blood pressure).
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Connective tissue diseases (such as Ehlers- Danlos syndrome, Loeys- Dietz, and Marfan syndrome).
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Childbirth and pregnancy.
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Inflammatory conditions (like lupus).
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Substance abuse.
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Smoking.
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Hypercholesterolemia (increased levels of cholesterol in the blood).
What Are the Signs and Symptoms Associated With SCAD?
The symptoms associated with spontaneous coronary artery dissection (SCAD) are similar to those of heart attack. The symptoms include:
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Severe central chest pain.
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Chest pain radiating to arms, neck, and jaws.
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Numbness in the left arm.
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Nausea and vomiting.
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Fatigue, especially at rest.
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Dyspnea (shortness of breath).
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A sudden unexplained episode of hyperhidrosis (excessive sweating which is not related to heat or exercise).
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Heart palpitations.
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Irregular heartbeats.
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Lightheadedness.
How Is Spontaneous Coronary Artery Dissection Classified?
Spontaneous coronary artery dissection (SCAD) can be classified into the following three types:
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Type 1: In this type, multiple radiolucent lumens are seen within the arterial walls. This can also be seen as increased staining when a contrast medium is used.
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Type 2: Diffuse stenosis (narrowing) of varying severity and length (usually greater than 20mm) within the arteries is seen in this type. This type of spontaneous coronary artery dissection can be further classified into two subtypes, namely:
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Type 2A: It is marked by diffuse arterial narrowing, bordered by normal segment, proximal and distal to the intramural aortic hematoma (IMH).
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Type 2B: It is marked by diffuse narrowing that extends to the distal tip of the artery.
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Type 3: This type of spontaneous coronary artery dissection is much more challenging to diagnose since it mimics atherosclerosis (hardening of the arteries due to the deposition of a waxy-fat-like substance called cholesterol plaque on the inner surface of blood vessels). Focal or tubular stenosis of the arteries can be seen, affecting arteries that are less than 20 mm in length. Special optical devices, such as optical coherence tomography (OCT) and intravascular ultrasound (IVUS), are required to diagnose lesions of this category.
Studies show that type 2 lesions are the most commonly found in individuals diagnosed with spontaneous coronary artery dissection (affecting 67 percent of the individuals). Type 1 lesions are the second most common, affecting thirty percent of diagnosed individuals, followed by type 3 lesions, affecting three percent of the diagnosed individuals.
How Does a Clinician Diagnose Spontaneous Coronary Artery Dissection (SCAD)?
Imaging techniques are used in conjunction with the analysis of clinical signs and symptoms to evaluate spontaneous coronary artery dissection. The imaging tests include:
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Coronary Angiogram - It is the standard diagnostic test for diagnosing spontaneous coronary artery dissection. It is an invasive imaging technique for visualizing the arteries surrounding the heart and identifying obstructions or narrowings. A catheter (thin-flexible-wire-like tube) is inserted in the arm or upper leg and passed until it reaches the heart. X-ray pictures are taken to determine the location of occlusion within the blood vessels.
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Intravascular Ultrasound (IVUS) - A diagnostic test that allows the clinician to visualize the inner aspect of the blood vessels by using sound waves. It provides a high spatial resolution to image the coronary artery wall to detect the tears within it. A general view of the coronary arteries is provided through an angiogram. However, it cannot display the arterial walls. An intravascular ultrasound (IVUS) can show cholesterol and fat deposits and disclose the arterial wall. These deposits can accumulate and make an individual susceptible to a heart attack.
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Optical Coherence Tomography (OCT) - A technique used in medicine for imaging cross-section tissue. Unlike other imaging techniques, OCT is restricted to more superficial tissues. It gives an excellent view of the inside view of the vessel, which enables the clinician to determine the best size of the stent and treat the vessel adequately.
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Cardiac Computerized Tomography Angiography (CCTA) - Also known as a cardiac CT, it is a non-invasive diagnostic imaging test that shows detailed images of the heart and its associated structures, such as blood vessels, valves, etc. It gives more comprehensive images when compared to those of traditional angiograms. At times, doctors may advise a ‘contrast cardiac CT’ - it involves the use of a special dye (also known as contrast) injected and helps amplify the images.
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Enzyme Marker Test - Refers to a series of blood tests that help evaluate the levels of cardiac enzymes. Elevated cardiac enzymes can indicate an underlying cardiac disease or injury to the cardiac tissue.
How Does a Clinician Treat Spontaneous Coronary Artery Dissection (SCAD)?
While treating individuals diagnosed with spontaneous coronary artery dissection, the primary target is to improve the blood flow to the heart. The blocks in the blood vessels starve the heart tissue of oxygen and nutrients, damaging the cardiac tissue and leading to a heart attack. In most cases, symptoms improve by managing hypertension (increased blood pressure) and hypercholesterolemia (high cholesterol levels). Anti-platelet medications also help improve the blood flow to the heart by preventing the formation of blood clots. If symptoms persist after conservative approaches, surgical intervention may be required. Surgical interventions include:
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Cardiac catheterization and coronary angioplasty with the placement of a stent.
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Coronary artery bypass (CABG).
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Left ventricular assist device.
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Implantable cardioverter defibrillator (ICD).
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Heart transplant.
Conclusion
Although symptoms of spontaneous coronary artery dissection (SCAD) are similar to that of a heart attack, it is not a heart attack essentially. When an individual presents with a heart attack, treatment involves unblocking the artery by placing a stent to open up the clot. But, in the case of spontaneous coronary artery dissection (SCAD), it may not always be required. Often medications (including blood thinning medications) can improve symptoms, and it has been seen that the coronary blood vessel does heal within a few months without needing to put a stent in the artery. In most cases, patients recover completely and lead normal lives without long-term consequences.
