The first successful open-heart surgery was performed in Chicago in 1893 on a patient who had a knife wound. At that time, medical authorities did not support performing cardiac surgery because it was too dangerous. It wasn’t until the 1950s, following the development of the heart-lung machine, that cardiac surgery as we know it today really began.
Surgical Approaches Evolve
In the last 10-12 years, we have seen significant changes in the surgical approach to valvular heart disease (VHD). Initially, heart valve surgery was performed via a left thoracotomy with an incision that started on the lower left chest near the sternum and wrapped around laterally to the back. This procedure evolved into a “less” invasive approach by thoracic surgeons who performed median sternotomies, which was the gold standard for many years. Today, 70 years later, in many centers cardiothoracic surgeons are partnering with interventional cardiologists in hybrid ORs and performing transcatheter procedures to treat valvular stenosis and regurgitation. Heart valve teams have been implemented in many cardiac surgery centers in the U.S. The team consists of cardiologists, cardiothoracic surgeons, echocardiology and others to review patients who were identified as possible candidates for a valve procedure. The patient’s history and invasive/noninvasive findings are discussed by the team followed by a recommendation for either an invasive or minimally invasive surgical intervention.
Overview of VHD
The heart has four valves whose sole purpose is to maintain normal one-way blood flow through the heart chambers. The tricuspid and pulmonic valves are on the right side, which receives and sends venous blood to the lungs. The mitral and aortic valves are on the left side, which receives and sends arterial blood flow out to the body. (The valves open and close based on changes in pressure within the heart chambers during diastole and systole. Components of the valves include the valve leaflets, the size of the valve ring or annulus (opening), and chordae tendineae and papillary muscles (mitral and tricuspid).
The CDC estimates 2.5% of the U.S. population has VHD. It is more common in adults over the age of 65 years. Common causes of VHD include:
- Rheumatic disease
- Congenital abnormality (failure of one leaflet to develop)
- Aging: commonly due to the development of calcium deposits on the valve leaflets impairing the ability of the valve to either open or close properly
- Myocardial infarction: myocardial ischemia may weaken or rupture a papillary muscle and limit its ability to hold a valve leaflet in place
- Dilated cardiomyopathy
Signs and Symptoms
VHD often develops very slowly; therefore, signs and symptoms associated with VHD may not be apparent until the valve abnormality is advanced. When VHD develops suddenly, symptoms are more apparent and may include one or more of the following:
- Shortness of breath
- Atrial fibrillation
- Weight gain
- Chest pain
- Heart murmur
Interventions: Medical vs. Surgical
VHD may be managed medically or surgically. Depending on the severity of the abnormality, medical management is initially focused on managing symptoms and the cause (e.g., endocarditis). Our discussion will focus on surgical management.
Aortic stenosis (AS) and mitral insufficiency are the two most common types of VHD requiring surgery: either valve replacement or valve repair. The ACC/AHA clinical practice guideline for the management of patients with VHD was updated recently. Many procedures may be performed that use a minimally invasive approach as opposed to a median sternotomy. Minimally invasive approaches include using a transcatheter approach for the dysfunctional valve, or a small surgical incision along the right sternal border with mitral valve replacement or repair. Many surgeons have transitioned to a minimally invasive approach as their preferred technique.
In the case of a stenosed mitral valve, the recommended ACC/AHA guideline for valve repair is minimally invasive percutaneous balloon valvotomy to separate the valve leaflets and open the valve. This procedure is recommended when the mitral valve area is less than 1.5 cm2. These patients frequently have pulmonary hypertension, right ventricular failure, peripheral edema, ascites and hepatomegaly. Tricuspid regurgitation occurs and the onset of atrial fibrillation is common. This procedure involves advancing a balloon-tipped catheter via the femoral vein into the right atrium, across the intra-atrial septum through the mitral valve. The balloon is inflated and pulled back across the valve, enlarging the valve opening. First approved in 2010, this procedure improves survival, reduces pulmonary hypertension and prevents atrial fibrillation.
The valve leaflets do not close properly in the setting of mitral regurgitation. Repair of the valve is recommended using a minimally invasive approach. The goal is to reduce or prevent blood flow leaking back into the left atrium during ventricular systole.
Transcatheter Mitral Valve Repair
In 2013, the MITRACLIP (Abbott Vascular, Santa Clara, California) was FDA approved for mitral valve repair. This procedure is performed in a hybrid OR (operating room with fluoroscopy/cath lab equipment). A catheter with the device, which is about the size of a dime and is attached on the end of the catheter, is advanced via the femoral vein to the right atrium, across the atrial septum into the left atrium. It is subsequently deployed by attaching it to the edges of two valve leaflets. The catheter is then withdrawn. The procedure is now referred to as transcatheter mitral valve repair (TMVr). The average length of stay post-procedure is two days. Studies have shown an 89% decrease in the severity of mitral regurgitation, and 78% of patients experience an improvement in their AHA functional class to a I or 11 at one year. Following the procedure, left ventricular dysfunction may appear since it is now unmasked. The patient may also have pulmonary hypertension as a result of the increased left atrial pressures.
AS is commonly caused by age-related calcium deposits on the aortic valve leaflets reducing the size of the valve opening and impeding blood flow from the left ventricle during systole. Initially, the patient may be asymptomatic, but as the stenosis worsens, they begin to exhibit classic signs, including angina, dyspnea on exertion, syncope, heart failure and sudden cardiac death (SCD). Studies have shown that once a patient displays one of these classic symptoms, an intervention is recommended. Mild AS is characterized by a valve area of 1.5 cm2 and severe AS is associated with a valve area less than 1.0 cm2. The outcome is poor if the stenosis is not addressed when there is an 11.6% increase in the risk of SCD. ACC/AHA guidelines now recommend either a surgical valve replacement or a transcatheter aortic valve procedure for patients with a low or intermediate risk. These procedures are also recommended for patients considered to be high risk after evaluation by the heart valve team.
Transcatheter Aortic Valve Replacement
Transcatheter aortic valve replacement (TAVR) has become the standard of care for patients requiring aortic valve surgery. The procedure is performed in a hybrid OR with the cardiologist introducing and advancing the catheter. A cardiothoracic surgeon is in attendance if emergency surgery is required. A prosthetic tissue valve is collapsed and embedded within a stent-like frame. The device is mounted around a balloon on a catheter, which is commonly introduced via the femoral artery up through the aorta and optimally positioned across the native aortic valve. The balloon is inflated, expanding the frame and opening the valve. The balloon catheter is then removed. TAVR is also FDA approved for a repeat TAVR procedure in someone with a previous prosthetic valve procedure. This is referred to as an aortic transcatheter heart valve (THV) in a previous THV (THV in THV) procedure. Studies have demonstrated improved outcomes in patients who have had this procedure. Complications are few, the most significant being dislodgement of the valve from the orifice up into the ascending aorta. In most cases the valve can be retrieved. However, in the rare situation when it is not, the patient will undergo a traditional sternotomy approach with a valve replacement.
Aortic insufficiency is present when the aortic valve fails to close completely and regurgitant blood flows back into the left ventricle. A common cause is the presence of a bicuspid aortic valve. Generally, symptomatic patients are recommended to undergo an aortic valve replacement.
Ongoing studies will help evaluate the future use of transcatheter interventions for abnormalities of the tricuspid and pulmonary valves.
Minimally Invasive Procedures Benefit Patients
The transition to minimally invasive procedures benefits our patients in many ways. Compared with the traditional sternotomy approach, transcatheter procedures are less invasive and less traumatic. General anesthesia may not be required, pulmonary complications are fewer, and hospital length of stay is shorter. For those of you caring for these patients, I encourage you to attend a heart valve team meeting if available at your facility. It will help you understand the evaluation process and considerations by the cardiologists and surgeons. It’s an exciting time to watch the progress to minimally invasive procedures as technological advances are made.
When are you going to attend a heart valve team meeting?