What Is Structural Heart Disease?
Structural heart disease refers to heart disease that is acquired through wear and tear, or heart disease that people are born with. An example of structural heart disease acquired through wear and tear would be a tight or leaky heart valve. An example of structural heart disease people are born with would be a hole within the chambers of the heart. Heart valve disease is by far the most common structural heart disease encountered by structural heart specialists in clinical practice.
Structural Heart Disease – A Revolutionary Field
Structural heart disease is one of the most exciting and fastest growing fields in cardiovascular medicine. Incredible advancements in technology have allowed previously unthinkable procedures to become the norm. For many patients with structural heart disease, previously high-risk open-heart surgeries have been replaced by non-surgical minimally invasive procedures with lower risk, less trauma, and a faster recovery. Such procedures include heart valve repair and replacement that can be performed through small tubes known as catheters. Originally designed for high-risk populations, structural heart procedures are being performed on lower and lower risk populations.
Catheter Based Structural Heart Procedures
Structural heart disease procedures are performed through small tubes known as catheters. These catheters are hollow and through them a variety of instruments are passed up to the heart and used to deliver treatment devices. The catheters are typically placed through catheters in the leg. For example, in patients with diseased heart valves, a new valve is passed through a catheter and secured in to place. Incredible technology allows these valves to be passed up to the heart in a highly compressed state so it can pass through the catheter, and then when in the correct position, it can be expanded appropriately to the desired size where it becomes a fully functioning valve.
Structural Heart Disease and the Heart Team
Structural heart disease procedures require a great deal of expertise and a team approach. The term used for this is a heart team approach. The heart team generally consists of interventional cardiologists, heart surgeons and imaging specialists. Each member has a key role and ultimately the combination of these specialists allows development of optimal treatment plans. In many structural heart procedures the interventional cardiologist and the surgeon will perform the procedure together while the imaging specialist is guiding them.
Structural Heart Disease Procedures vs. Surgery – Which is Better?
In the leading centers, structural heart specialists and cardiac surgeons work hand in hand to provide the widest range of options for patients with structural heart disease. In some cases open-heart surgery is a better option, and in some cases catheter bases structural heart procedures are a better options.
When deciding on the best options for structural heart disease patients I will ask my self the following questions:
What does the evidence suggest? What will provide the best result? What is the acceptable degree of risk associated with the procedure? Will the result be durable in the long term? What does my patient want?
The best answer to the above questions lies in a meeting of the minds of both surgical and structural specialists who can discuss the pros and cons of each approach and come up with the best answer on a case-by-case basis.
Common Minimally Invasive Structural Heart Procedures
Transcatheter Aortic Valve Replacement (TAVR)
The most significant advancement in structural heart disease in the last decade has been the TAVR procedure for the aortic valve. TAVR stands for transcatheter aortic valve replacement. In this procedure a new aortic valve is placed inside the old diseased aortic valve. Most commonly the catheter is placed through a blood vessel in the leg and the valve passed up to the heart. Sometimes the valve is placed through a small incision on the chest wall. The TAVR procedure is currently the most commonly performed structural heart procedure in the world.
Transcatheter Mitral Valve Repair (TMVR)
The most common transcatheter mitral valve procedure currently performed in the US for structural heart disease is the Mitraclip procedure for patients with a leaky mitral valve known as mitral regurgitation. In the Mitraclip procedure, a clip is placed on the leaky portion of the valve reducing the leak. It’s an attempt to replicate an old surgical technique called the Alfieri stitch whereby a stitch was placed between the leaking portions of the valve. A current exciting field is the development of a transcatheter mitral valve replacement that will allow an entirely new valve to be placed in the mitral position.
Atrial Septal Defects (ASD) and Ventricular Septal Defects (VSD)
Atrial septal defects are holes in between the top chambers of the heart and ventricular septal defects are holes in between the bottom chambers of the heart. The majority of these defects are present from birth and if large enough can lead to heart enlargement and heart failure. The majority of these defects can be closed with catheter-based devices that cover the defects and are associated with excellent results in appropriately selected patients.
Hypertrophic Cardiomyopathy (HOCM)
In hypertrophic cardiomyopathy, or HOCM, there is enlargement of the heart that causes obstruction to blood flowing out of the heart. HOCM is a relatively common structural heart disease. In patients that remain with symptoms despite medicines there are two options, firstly is an operation known as a myomectomy which is an open heart operation that involves cutting out the area of tissue causing the obstruction. The minimally invasive option is known as alcohol septal ablation and is a catheter-based procedure that involves injecting a small amount of alcohol in to the area causing the obstruction causing it to shrink.
Patent Ductus Arteriosus (PDA)
The patent ductus arteriosus is a connection between the main blood vessels that leave the heart. The vessel supplying the body is known as the aorta and the vessel that sends blood to the lungs is known as the pulmonary artery. The PDA connects these structures so that before birth, when the baby is not breathing air, oxygen rich blood from the mother is able to reach the body. In about 2 out of every 2000 births the PDA stays open and can lead to heart enlargement if it stays open in to adulthood. In most patients the PDA can be closed by transcatheter techniques.
Left Atrial Appendage Occlusion
Patients with atrial fibrillation are at increased risk of stroke because of clots that can form inside a structure in the top chamber of the heart known as the left atrial appendage. The use of blood thinners can reduce the risk of stroke. Many patients however cannot take the blood thinning medications due to a high risk of bleeding. In such patients, a catheter based structural heart procedure known as left atrial appendage occlusion can be performed to eliminate the appendage. An example is the Watchman device.
Paravalvular Leak Repair
Hundreds of thousands of patients have had valve replacement surgery where a metallic or a tissue valve is used to replace the diseased valve. In some of these patients, the stitches used to sew the valve in to place can become loose resulting in a leak around the valve. This is known as a paravalvular leak. Traditionally repeat open-heart surgery was required to repair the defect. In a few specialist centers, such as Princeton Baptist Medical Center, transcatheter techniques can be used to close these defects avoiding the need for open-heart surgery.
Pulmonary embolisms are clots in the lung and are amongst the most common cause of death in the US. Large pulmonary embolisms are known as massive and submassive pulmonary embolisms and are critical situations for those patients that make it to hospital. Traditionally the only options for these large clots were open-heart surgery or clot busting medicines, both associated with significant side effects. Now catheter based treatments can effectively treat pulmonary embolisms while avoiding open-heart surgery or the bleeding risks associated with large doses of clot busting medicines.
Other Structural Heart Disease Procedures
Other procedures commonly performed by structural heart specialists may include:
- Repair of coarctation of the aorta
- Repair of aneurysms
- Repair of fistulas
- Balloon valvuloplasty for mitral stenosis
- Transcatheter mitral valve replacement
- Transcatheter pulmonary valve replacement
- Insertion of mechanical circulatory support
- Intracardiac biopsies
- Intracardiac ultrasound
Structural Heart Disease – The Future
Structural heart disease procedures are growing at a remarkable pace. Just a few years ago no one would have believed that heart valves could be replaced through small tubes inserted in to the vessels of the leg. Now hundreds of thousands of such procedures have been performed. It’s well accepted now that the majority of open-heart procedures will gradually be replaced by more minimally invasive options for patients with structural heart disease as technology progresses.