Percutaneous pulmonary valve implantation
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Transcatheter pulmonary valve replacement (TPVR), also known as percutaneous pulmonary valve implantation (PPVI), is the replacement of the pulmonary valve via catheterization through a vein. It is a significantly less invasive procedure in comparison to open heart surgery and is commonly used to treat conditions such as pulmonary atresia.


Uses

TPVR can be used to repair congenital defects in the pulmonary valve or right ventricular outflow tract dysfunction, such as pulmonary atresia, Tetralogy of Fallot, or
persistent truncus arteriosus Persistent truncus arteriosus (PTA), often referred to simply as truncus arteriosus, is a rare form of congenital heart disease that presents at birth. In this condition, the embryological structure known as the truncus arteriosus (embryology), t ...
. TPVR can also be used to replace dysfunctional artificial heart valves. For those experiencing symptoms, TPVR is indicated when the right ventricular
systolic pressure Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" r ...
is above 60 mmHg and/or when there is moderate to severe pulmonary regurgitation. For those not experiencing any symptoms, TPVR is indicated if there is severe right ventricular outflow tract narrowing and/or severe pulmonary insufficiency, with decreased exercise capacity, progressive right
ventricular dilation Cardiomegaly (sometimes megacardia or megalocardia) is a medical condition in which the heart is enlarged. As such, it is more commonly referred to simply as "having an enlarged heart". It is usually the result of underlying conditions that make t ...
, progressive right ventricular dysfunction, progressive tricuspid valve regurgitation, right ventricular systolic pressure above 80 mmHg, or cardiac fibrillation. For dysfunctional artificial conduits, TPVR immediately resolves pulmonary regurgitation and normalizes the right ventricular outflow tract gradient, and is associated with significant improvements in symptoms and improvements in long-term ventricular function.


Contraindications

Active infection, central vein occlusion, coronary occlusion, and need for other surgeries such as for
arrhythmia Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults ...
are contraindications for TPVR. If coronary compression (which impairs coronary blood flow) is observed with
balloon dilation Angioplasty, is also known as balloon angioplasty and percutaneous transluminal angioplasty (PTA), is a minimally invasive endovascular procedure used to widen narrowed or obstructed arteries or veins, typically to treat arterial atheroscleros ...
in the right ventricular outflow tract, TPVR is also contraindicated. This test is performed to prevent potentially fatal complications, for which approximately 5% of candidates are at risk. TPVR is not recommended for tracts that are less than 16 mm or more than 29 mm in diameter.


Complications

There is a low incidence of major complications, which is likely due to pre-procedural assessments preventing individuals with unfavourable anatomy from undergoing the procedure. The most common complication is fracture of the stent frame. This is seen in up to 30% of cases. The majority of stent fractures are diagnosed by routine imaging and are not clinically relevant. Stent fractures leading to obstruction of the right ventricular outflow tract is the most common reason for repeat intervention and can be treated with valve-in-valve procedures (placing a new valve inside the failed valve). More severe fractures may require surgery. Risk factors for stent fractures include younger age, smaller tract diameter, and position of the valve directly below the sternum. Tears or ruptures of the right ventricular outflow tract may occur during the procedure, especially if the tract is already heavily calcified. This is reported to occur in up to 9% of procedures. Most cases are manageable by using a covered stent and do not lead to severe bleeding. Infective endocarditis occurs at a rate of about 1%-3%. Most cases do not directly impact the implanted valve, and most cases can be treated with antibiotics. However, infective endocarditis can also cause valve explantation or sepsis, which can lead to death. Rare complications that may require urgent surgery include valve migration, valve embolization, pulmonary artery occlusion, pulmonary artery rupture, or coronary artery compression impeding blood flow. Death is rare, and is usually attributable to other comorbidities rather than from the implantation procedure itself.


Procedure


Pre-procedural assessment

Several tests are performed before the procedure to assess whether the procedure is suitable for the individual and to record their anatomy in preparation for the procedure. Ventricular function and size are assessed with an echocardiogram. The right ventricle and the anatomy of the outflow tract, including any anatomical variations, are also assessed with cardiac magnetic resonance imaging. The severity of the outflow tract defect or pulmonary regurgitation is assessed with Doppler ultrasonography.


Operation

TPVR is a percutaneous procedure, meaning the device is brought into the body through the skin and into a vein. Patients are put under general anesthesia. The heart is typically reached by passing through the femoral vein, jugular vein, or
subclavian vein The subclavian vein is a paired large vein, one on either side of the body, that is responsible for draining blood from the upper extremities, allowing this blood to return to the heart. The left subclavian vein plays a key role in the absorption ...
. A balloon dilation test is performed first, to confirm that coronary compression will not occur and the procedure can continue. Stent fractures can be prevented by using pre-stenting, using a bare metal stent before TPVR. After the valve is implanted, balloon dilation is used to create the diameter of the valve. At the end of the procedure, pressure is applied to the area to encourage hemostasis (stop bleeding).


Recovery

Patients undergoing TPVR are typically ambulatory within 6 hours of finishing the procedure and can be discharged home within 24 hours. As cardiopulmonary bypass is not required, a stay in the intensive care unit and an extended hospital stay are generally not needed.


History

TPVR was developed as a less invasive alternative to other treatment options requiring open heart surgery, such as patch augmentation, replacing the native valve with an artificial heart valve, or using a
valved conduit Apicoaortic Conduit (AAC), also known as Aortic Valve Bypass (AVB), is a cardiothoracic surgical procedure that alleviates symptoms caused by blood flow obstruction from the left ventricle of the heart. Left ventricular outflow tract obstruction ( ...
. These surgeries typically require repeat surgeries to repair issues including pulmonary regurgitation, valve narrowing, kinking of the conduit, or calcification, leading to significant morbidity. The first TPVR was performed in 2000. This device was further developed into the Melody transcatheter pulmonary valve by
Medtronic Medtronic plc is an American medical device company. The company's operational and executive headquarters are in Minneapolis, Minnesota, and its legal headquarters are in Ireland due to its acquisition of Irish-based Covidien in 2015. While it ...
. The Melody device received approval from Health Canada in 2006 and from the US Food and Drug Administration (FDA) in 2010. A similar device, the Edwards Sapien pulmonic transcatheter heart valve, produced by
Edwards Lifesciences Edwards Lifesciences is an American medical technology company headquartered in Irvine, California, specializing in artificial heart valves and hemodynamic monitoring. It developed the SAPIEN transcatheter aortic heart valve made of cow tissue wi ...
, first received FDA approval in 2015. The comparatively lower risks of TPVR and reduced need for reintervention compared to traditional surgical treatments has led to a paradigm shift favouring earlier treatment for right ventricular outflow tract defects, which were previously postponed due to the risks of traditional surgery.


See also

*
Cardiac catheterization Cardiac catheterization (heart cath) is the insertion of a catheter into a chamber or vessel of the heart. This is done both for diagnostic and interventional purposes. A common example of cardiac catheterization is coronary catheterization that ...
* Percutaneous aortic valve replacement


References

{{Interventional cardiology Cardiac procedures