Introduction
PVL is not a common but severe complication that develops post-surgical and transcatheter aortic value replacement. PVLs occur due to a gap being present between the native annulus and the prosthetic valve’s outer edge1. When the prosthetic valve detaches, it forms a channel between the implanted valve and the cardiac tissue through which blood flows; the flow of blood through this channel is referred to as a PVL2. PVL is caused by sewing ring suture disruption that can be triggered by infective endocarditis which may be associated with abscess formation, annulus fibrotic scars or calcification. Although clinically silent in most cases, PVLs can also develop into severe regurgitation, which manifest into clinical symptoms of heart failure and haemolysis, and increased mortality3. The gold standard treatment for severe PVL has been treated surgically. However, two studies suggested that re-intervention can cause a high mortality rate 45.
The long-term outcomes and functionality after transcatheter aortic-value replacement (TAVR) were investigated in 2032 patients (from 57 different centres) who had aortic stenosis. The patients were randomly assigned to either the TAVR group or the surgical replacement treatment group 6. In this study, PVL was reported to be higher in TAVR cohort (TAVR: 33.3% and Surgical treatment: 6.3%). Those in the TAVR group also had more hospitalizations and aortic valve re-interventions than those in the surgery group (TAVR: 33.3% and Surgical treatment: 25.2%, hazard ratio of 1.28, 95% confidence interval, 1.07 to 1.53). Despite the TAVR group having more undesirable outcomes, a similar health status improvement was seen in both groups6.
Classification of PVL
PVL can be graded using mainly three different grading systems: the 3-class, 4-class, and 5-class systems. The 3-class system involves grading PVL severity using the categories; mild, moderate, and severe7 . Whereas the 4-class system involves grading PVL into grade 1, 2, 3, and 4. As some PVLs may fall into ‘in-between’ groups, it is difficult to place them into categories, for example a PVL may be not mild nor moderate so cannot be placed into a group. For this precise reason, it may be advisable to grade PVLs using the 5-class system that covers the ‘in-between’ groups; the categories are: mild, mild to moderate, moderate, moderate to severe and severe. Some argue that the presence of more classification categories will create inconsistency in the classification. However, others argue that this system brings unification and clarification to the classification system7.
The major structural parameters that govern the grading of the PVL include: the shape, size, number, location of the PVL defect, the anatomical landmarks present, and the size of the left atrium and ventricle. 2-dimensional (2D) echocardiography can be used to assess the dehiscence and severity of PVL associated with the aortic value, whilst 3D echocardiography is usually used pre-operatively/intra-operatively for anatomical localization. PVLs that are graded ‘moderate to severe’ or ‘severe’ are usually due to a poorly placed valve or calcium build up in between the stent and the native annulus. The increase in left ventricle size can be a good indicator of chronic PVL (a PVL that have been present for more than three months), as those with acute PVL do not have a significant change in ventricle size or functionality. A mild, moderate, severely enlarged ventricle can indicate a mild, moderate, or severe PVL respectively7. Using qualitative echocardiography, it can be seen that in mild PVLs, the colour doppler jet width is less than 25% of the left ventricular width8. Whilst, in the moderate and severe PVL, the jet width is 25- 60% and more than 60% less than the left ventricular width respectively. The severity can also be classified using semi-qualitative echocardiography- which uses the total of the PVL jet circumference divided by the valve circumference as the circumferential extent. Mild PVLs have a circumferential extent of less than 10%, moderate PVLs extent is between 10-30% and severe PVLs have an extent that is more than 30%8.
Diagnosis and evaluation of PVL
Investigation tools such as transthoracic echocardiography (TTE), transoesophageal echocardiography (TOE), cardiac computerised tomography (CT) and cardiovascular magnetic resonance (CMR) are used to diagnose PVLs. The tool used is selected based on the outcome required and the patient’s health status. Following are the advantages and disadvantages of each imaging modality; a summary can also be found in Table 1 .
Echocardiogram
The first line diagnosis method for suspected PVL, alongside clinical assessment and physical examination, involves transthoracic echocardiogram (TTE). The non-invasive method provides evaluation on the functionality of the prosthetic valve. The prosthetic valve is assessed using 2D imaging techniques and doppler. This assessment is used to determine factors such as: the size of both the atria and ventricles, valvular disease and the possible masses that may be present in either the original or prosthetic valve. Although there are benefits of using TTE, its use is restricted by shadowing seen on images, which may be caused by the prosthetic valve components or calcification of the annulus. The inaccurate imaging can result in the doppler signal having no colour ultimately resulting in underestimation of the severity of PVL and poor aetiology differentiation9. An example of a patient’s scan with aortic PVL can be seen in Figure 110.
Transesophageal echocardiogram (TEE) is an invasive imaging technique, preferred for intraprocedural guidance, that can be used to accurately determine the severity, mechanism, and the location of the PVL. In addition to this, TEE can be used to visualise any tears in the prosthetic valve. Regardless of the benefits, like TTE, this imaging modality can also be limited by shadowing due to anterior aortic annulus9. TEE’s use is restricted due to it being an invasive procedure that requires trained physicians, patient sedation, mechanical ventilation for the patient and a possible injury to the oesophagus11.
Cardiac CT
In cases where both TTE and TEE cannot determine conclusively the grade or location of the PVL, cardiac CT can be used 9. Cardiac CT is usually used as an imaging technique preoperatively for those who are due for TAVR; it can aid in verifying the annulus’ size and shape and calcification degree12. Multiple studies which have investigated the effect of calcification on the presence of PVLs have found a correlation between calcification, which can only be removed by surgically, and aortic regurgitation post TAVI13 14. The downfalls of cardiac CT scanning, however, need to be considered before a patient undergoes it. Cardiac CT involves the use for intravenous iodinated contrast agents which can potentially cause nephropathy15 and anaphylactic shock (which is rare but serious life-threatening condition that requires urgent care)16. The patient will be exposed to radiation and poor resolution is seen in those with tachycardia 9. There is also a need for a specialist radiologist report after a CT is performed which may be time consuming and that is not ideal in an emergency setting. In emergency cases, it would be advisable to use echocardiography instead as it can be easily read by cardiologists and surgeons17.
Cardiac magnetic resonance (CMR)
CMR can also be used in all patients especially when the TTE and TEE cannot conclusively predict the PVL degree or location in patients9. As mentioned previously, there is a risk of nephropathy when using CT in patients with renal failure. CMR is a novel non-contrast imaging modality that can be used in elderly patients18. This imaging technique can also be used in all patients, even those with mechanical valve prostheses if the imager has the necessary equipment. A major limitation seen with CMR is the overestimation of the severity of the PVL. To overcome this hurdle, it is necessary to utilise other imaging in assessing the severity of PVL. Due to the components of the mechanical valve, CMR also provides a poor image with mechanical valves in comparison to bioprosthetic valves. In addition to this, the assessment accuracy is also affected by tachyarrhythmias 9 and presence of claustrophobia in some patients (usually due to the nature of the technique or the duration of the procedure) 19 In those who are claustrophobic, a relaxant such as diazepam could be used to obtain a successful image 19,20.
Clinical impact of PVL:
The presence of PVL may cause many major consequences including clinical and haemodynamic complications that reduces the long-term survival. Clinical presentation of PVL is primarily due to heart failure12. Chronic regurgitation can cause left atrial and ventricular pressure increase and volume overload including symptoms of pulmonary oedema and heart failure. Whilst a less severe regurgitation can only cause heart failure should the receiving chamber be non-compliant, making it difficult to attribute the patients’ symptoms to the PVL. 21 Patients with small PVLs are more likely to experiences symptoms of haemolytic anaemia (significant anaemia is usually treated with blood and/or platelet transfusion) whereas those with larger PVLs have symptoms of heart failure and infectious endocarditis. 22 Recent studies have suggested that moderate to severe PVL occurs in 2.5% of patients after the TAVR 23. It was believed that moderate to severe PVL is more likely to cause mortality. However, a Placement of AoRTic TraNscathetER valve (PARTNER) trial had proven that even a mild PVL is connected with increased mortality 24, rejecting this theory.
Available management options
PVL can be treated through an invasive open-heart surgery or through a catheter-based treatment. As PVLs vary in shape and size, the correct device must be used to ensure successful closure of PVLs. There are 6 most frequent devices that are used to manage paravalvular leak. The devices, seen in Figure 2 , include Amplatzer vascular plugs (AVP2, AVP3 and AVP4), Amplatzer Duct Occluder (ADO), muscular Ventricular Septal Defect Occluder (mVSD) and Paravalvular Leak Device (PLD)25. The properties of the device vary by material, occlusive planes, waist length, size difference (between the waist and the disk) and are summarized in Table 2 . The device selected for use depends on the factors such as the distance of the landing zones, the size of the PVL, and the type of blood flow at the location of the PVL. AVP1, for example, is used in short landing zones and, since it can be repositioned, it also provides a precise and rapid occlusion whereas AVP2 can be utilised in variable landing zones. In situations where the PVL is in a high blood flow area or in demanding wall apposition cases, AVP3 can be used. In situations where the anatomy is tortuous, it is best to use AVP4. The use of AVP relies on the patient having an effective coagulation system. Should the patients have an ineffective coagulation system, AVP might not provide complete occlusion. The delivery of the AVP also requires a guiding catheter and large access sheath and as the delivery wires are hard, it may also be challenging to guide the device to the appropriate area26.