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.