Septal Myectomy In Hypertrophic Cardiomyopathy (HCM) Patients: Procedure, Risks, Recovery

Hypertrophic cardiomyopathy (HCM), the most common type of inherited heart disease, affects up to one in 200 people. It’s characterized by an abnormal thickening of parts of the heart muscle that can impair the heart’s pumping ability.

A thickened septum (a muscular wall between the right and the left side of the heart) can limit the passage of the blood from the heart to the rest of the body. That often leads to symptoms like breathlessness, chest pain, fatigue, and dizziness. HCM can cause serious complications like heart failure, stroke, and sudden cardiac death.

How does HCM affect the heart?

Your heart consists of four chambers — two upper chambers called atria, and two lower chambers called ventricles. Valves direct blood from the atria to the ventricles. The mitral valve sits on the left side, while the tricuspid valve is located on the right side. The part of the septum that separates the left and right ventricles is called the ventricular septum.

The aorta is the main artery that carries oxygen-rich blood from the heart to all of your other organs and cells. The blood travels to the aorta from the left ventricle through the aortic valve, which is positioned just above the left side of the septum. If the septum becomes too thick, it can bulge into the left ventricle and block or limit the passage of blood. This is known as outflow tract obstruction, and it happens in a subtype of HCM called hypertrophic obstructive cardiomyopathy (HOCM). In people with this condition, the left ventricle needs to work harder to pump blood out.

HOCM has been associated with a higher risk of ventricular arrhythmias (irregular heartbeat) and sudden cardiac death compared to other types of HCM. This can partially be explained by the fact that most HOCM patients have an abnormal diastolic function, which means their heart doesn’t fill with blood in the way in it’s supposed to.

Septal myectomy: Details of the procedure

Before the procedure, a cardiothoracic anesthesiologist will administer general anesthesia, which ensures that you will be asleep the whole time.

The surgery starts with a six to eight inch vertical incision along the sternum (breastbone), after which the sternum is divided, exposing the heart. The pericardium (a sack that holds the heart) is opened with a vertical incision just above the center of the aorta.

Many open-heart surgeries are easier to perform on a still and bloodless heart. For this reason, a machine called cardiopulmonary bypass or heart-lung machine is used, which takes over the role of your heart. It ensures that oxygenated blood circulates through the body while the heart is stopped.

The surgeon will access the septum through the aorta, which removes the need to cut the heart muscle. Excess septum tissue is excised, usually anywhere from three to 12 grams.

The heart-lung machine is turned off and the heart starts beating on its own. The surgeon may perform tests using transesophageal echocardiography (echo) to check if all of the tissue that was obstructing blood outflow is removed. Temporary pacing wires are placed on the atria and the ventricles, and a chest tube may be inserted to drain excess fluid. The tissue is closed with internal, absorbable sutures. The surgery lasts anywhere from three to six hours.

What are the benefits and risks of septal myectomy?

Septal myectomy is considered to be a gold standard strategy for treating outflow obstruction and it has been performed for over 50 years. It comes with many benefits:

• The majority of patients enjoy symptom improvement immediately after the surgery.
• There is a low risk of death during the surgery, with mortality rates less than one percent.
• A study that did a long term follow up found that life expectancy of HCM patients who underwent septal myectomy approached that of the general population (survival rates for one, five, and 10 years were 98 percent, 96 percent, and 83 percent, respectively).
• HCM patients who underwent septal myectomy were less likely to die from cardiomyopathy related complications than both obstructive and non-obstructive HCM patients.
• Life expectancy (including deaths that were unrelated to the cardiomyopathy) was greater for HCM patients that had the procedure than for HCM patients who didn’t.

 Risks during surgery

• Iatrogenic ventricular septal defects (VSDs). This means that there is a puncture on the septum which allows blood from the right and left ventricle to mix; it can happen if too much of the septum wall is excised, in which case it’s repaired right away.
• Bleeding.
• Formation of clots (that may lead to stroke).
• Complications of general anesthesia.

Risks after surgery

• Conduction problems can lead to abnormalities in heart rhythm and pace, including conditions like heart block and different types of arrhythmias (irregular heartbeat) that can be life-threatening. The cause is not always known, but it can happen due to the damage of bundle of pacemaker cells in the heart (called the bundle of His) during surgery; some patients who didn’t require pacemakers will need permanent pacemaker after the surgery.
• Aortic valve replacement.
• Pericardial effusion (accumulation of fluid around the heart).
• Lung insufficiency (when the lungs can't meet the needs of the body).
• Infections that can lead to sepsis (a life-threatening condition if left untreated).
• Bleeding.
• Formation of cloths (that may lead to stroke).
• Re-operation.

Recovery from septal myectomy

Even though septal myectomy is considered a safe and reliable procedure, it's open-heart surgery and your body will need some time to heal, usually between six and eight weeks for a full recovery. Right after the surgery, you may feel sore, but you shouldn't be in serious pain. You can start sitting and walking with help the next day. Time spent in the hospital is usually not longer than five days. You will require follow-up procedures, first to remove the stitches and after to monitor your condition. While you're recovering, you shouldn't lift heavy objects and your doctor will tell you when it's safe for you to drive.