Coronary Sinus Thrombosis: Causes, Symptoms, and Treatment

What Is Coronary Sinus Thrombosis (CST)?

Coronary sinus thrombosis is a life-threatening condition that involves the formation of clots within the coronary sinus (blood vessels of the heart). These blood clots inhibit blood flow, leading to complications. It is an extremely rare disease with no clear male or female predominance.

What Is a Coronary Sinus?

Located on the heart’s posterior surface, within the coronary sulcus (also known as the atrioventricular or AV groove), the coronary sinus refers to the largest and most conspicuous blood vessel of the coronary venous system. It is continuous with the great cardiac vein. It drains the majority (about 55 %) of the venous blood (also known as the deoxygenated blood) into the upper right chamber of the heart, otherwise known as the right atrium. The remainder of the deoxygenated blood, which does not travel via this route, is returned to the right atrium via the anterior cardiac vein and other tiny veins which open into the heart chambers themselves directly. The following blood vessels drain into the coronary sinus:

• Great cardiac vein.

• Oblique vein of the left atrium.

• Posterior vein of the left ventricle.

• Middle cardiac vein.

• Small cardiac vein.

What Is the Significance of the Coronary Sinus?

The coronary sinus is of great significance for clinicians as its location allows them to conveniently access the heart's blood vessels (myocardial capillary network). Cardiologists use this site for retrograde cardioplegia. Retrograde cardioplegia refers to the surgical procedure in which a cardioplegic solution (a solution capable of temporarily arresting the heart) is delivered via a catheter by introducing it to the coronary sinus to protect the heart (myocardium) during cardiac surgeries. From the cardiac electrophysiology standpoint, the coronary sinus also acts as a site for electrode implantation during mapping and ablation techniques.

What Are the Causes of Coronary Sinus Thrombosis (CST)?

The following diseases have established an association with coronary sinus thrombosis:

1. Atrial Fibrillation (AF): It is a heart condition in which electrical impulses travel through the upper chambers of the heart (right and left atrium) in a disorganized manner. This results in the muscle fibers contracting at different times, making the heart appear as if it is twitching or quivering. In simple terms, they beat very rapidly and irregularly, and this form of arrhythmia is very common. It is diagnosed by the finding of an irregular ventricular rhythm. The most concerning aspect of atrial fibrillation (AF) is that it leads to clot formation and embolism due to stasis in the atrium.

2. Right Heart Failure: This medical condition usually occurs due to left-sided heart failure but can also result from a heart attack that can damage the right ventricle (lower chamber of the heart). When the left ventricle weakens, there is an increase in fluid pressure, which forces blood back to the lungs. This damages the heart's right side, reducing the heart's pumping capacity. When this happens, fluid accumulates and backs up within the body's veins (blood vessels), leading to swelling of the lower extremities (feet, ankles, and legs).

3. Tricuspid Regurgitation: Also known as tricuspid valve regurgitation. It is a disease characterized by the backflow of blood into the heart's right upper chamber (right atrium) when the heart contracts. It could occur due to various reasons. A few of those reasons are:

• Blunt trauma to the chest.

• Carcinoid tumors (slow-growing tumors, arising at several places in the body).

• Ebstein anomaly.

• Infective Endocarditis.

4. Chronic Obstructive Pulmonary Disease( COPD): A chronic condition characterized by a group of lung diseases that lead to the blockage and inflammation of airways, eventually resulting in breathing difficulties. Emphysema( a condition that affects the tiny air sacs present in the lungs) and chronic bronchitis (a condition that is marked by a continuous, productive cough that lasts for at least three months and occurs due to the inflammation of the air passages) are the most common conditions which lead to COPD.

5. Chronic or Cor Pulmonale Due to Pulmonary Fibrosis: It is a medical condition wherein a disorder of the lungs causes the heart to malfunction. Typically, it is chronic but can also be acute and reversible. Pulmonary hypertension is the primary cause of cor pulmonale.

6. Kawasaki Disease: It is a vascular disease characterized by inflammation of the body's medium-sized blood vessels (arteries). Generally, they affect children between the ages of one to five years but can also affect teenagers and adults. It is a self-limiting condition associated with fever and inflammation. It can lead to devastating complications such as coronary artery aneurysms, myocardial infarction (heart attack), arrhythmias (irregular heartbeats), peripheral artery occlusion, and heart failure.

7. Acute Lymphoblastic Leukemia (ALL): It is a form of bone marrow cancer. Since it is acute, it gets worse quickly if it is not treated. It is the most common type of cancer in children but can also affect adults.

8. Crohn's Disease: This is an inflammatory bowel disease that causes inflammation in the bowel. It causes inflammation and tissue destruction anywhere along the gastrointestinal (GI) tract.

It can also occur as a side effect of invasive right heart surgeries. The heart surgeries which have been implicated with thrombosis in the coronary sinus are:

• Central venous catheter placement.

• Coronary sinus cannulation during retrograde cardioplegia.

• Bi-ventricular defibrillator placement in severe cardiomyopathy.

• Electrophysiologic ablations for arrhythmias.

• Coronary sinus instrumentation during ventricular lead placement.

• Ventriculoarterial shunt insertions.

How Can Coronary Sinus Thrombosis Be Diagnosed?

Typically, most people with coronary sinus thrombosis remain undiagnosed, and it is a finding which is seen during autopsies. Usually, it is an incidental finding in computed tomography (CT scan), angiography, or echocardiogram (ECG or EKG) during routine body scans.

What Is the Treatment for Coronary Sinus Thrombosis?

The treatment options for coronary sinus thrombosis are listed below:

• Thrombectomy - Treatment involves coronary sinus thrombectomy (removal of the blood clot from an artery or vein) along with the use of anticoagulants like Warfarin.

• Locally Administered Thrombolytics - These are the agents that can break down a clot. A few examples of these agents include Streptokinase, Urokinase, and Prourokinase.

• Corticosteroids - It helps to bring down levels of inflammation and edema (swelling) and is considered an adjunctive therapy. Examples of corticosteroids used are Dexamethasone and Hydrocortisone.

• Antibiotics - Intravenous antibiotics are recommended for a minimum of three to four weeks. Early and aggressive administration of antibiotics is preferred. Antibiotic therapy includes a Penicillinase-resistant Penicillin plus a third or fourth-generation Cephalosporin.

Conclusion

Coronary sinus thrombosis (CST) is an extremely rare condition with a complex nature. It can be caused due to cardiac surgical procedures which may lead to endothelial damage to the blood vessels or due to various underlying conditions. It requires immediate intervention, and routine body scans can help prevent fatal complications.