Transcatheter Aortic Valve Replacement – “Beyond the Procedure”

INTRODUCTION

Transcatheter aortic valve replacement (TAVR) is increasingly being embraced in both developed and developing nations as a treatment modality for severe aortic stenosis. It has the potential to become the primary treatment option not only for patients at high surgical risk but also for those classified as intermediate risk. Market research has estimated the TAVR market in 2020 which was 4559 million dollars to a fourfold increase to 16,937 million dollars in 2030. Asia pacific region is expected to register the highest increase.

It is important to study the valve durability, mechanisms of transcatheter heart valve (THV) failure and long-term efficacy. Approximately, 200,000 patients worldwide undergo surgical aortic valve replacement. The modes of failure of surgical bio prostheses, including infective endocarditis (IE), thrombosis, and structural valve failure (SVF), have been clearly described. In contrast, comprehensive analysis and evaluation of THV failure, as outlined in Table 1, is yet to be done. Knowledge gap exists in the current understanding of THV performance and outcomes. In the coming days, we shall be seeing more and more TAVR patients who shall have unique challenges in their post procedural care. And many a times, the procedure itself would have been the easiest part of their TAVR journey. Post TAVR care needs to be a continuous and concerted team effort involving patient and caregiver.

IE OF TAVR VALVE

The incidence of TAVR IE is about 1.1% as per the data from the multicenter registry from Italy and Germany.^[1] Incidence of surgical prosthetic valve IE is 03–1.2%/patient year. There was no difference in rates of surgical and TAVR endocarditis in the placement of aortic transcatheter valves (PARTNER) trial. The median time of manifestation of IE is in the first 6 months [Table 2].

PROSTHETIC VALVE THROMBOSIS (PVT)

THV thrombosis is rare. PARTNER trial did not report any cases of clinically significant prosthesis thrombosis nor did large TAVR registries.^[5,6]

• A thrombus is classified as PVT as per the VARC criteria^[7] if it is attached to or near an implanted valve; if it occludes the blood flow; if it interferes with the valve function, or if it is sufficiently large to warrant treatment.

• PVT of a TAVR prosthesis is very rare (up to 0.8%). It usually occurs at a mean time of 9 ± 7 months after the THV implant.^[2]

POST TAVR ANTITHROMBOTIC THERAPY

Single-antiplatelet therapy is preferred in post-TAVR patients who have no indications for oral anticoagulation (Class 2a, Level of Evidence [LOE]: B). Pre-procedural loading dose of aspirin has not been proven useful. Dual-antiplatelet therapy with aspirin (75–100 mg) and clopidogrel 75 mg is a class IIb recommendation.^[8] Anti-coagulation with a VKA for at least 3 months (Class 2b, LOE: B) may be considered in patients at low risk for bleeding. Patients on oral anticoagulation will require careful prothrombin time international normalised ratio (PT INR) monitoring. There are notable gaps in the evidence regarding the use of direct oral anticoagulants in patients with atrial fibrillation (AF) with TAVR [Figure 2].

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Figure 2:

Antiplatelet therapy post TAVR. (PCI: Percutaneous coronary intervention, DAPT: Dual antiplatelet therapy, VKA: Vitamin K antagonists, OAC: Oral anticoagulation, AF: Atrial fibrillation, NOAC: Novel oral anticoagulants).

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The efficacy of clopidogrel in elderly patients is debatable for several reasons.^[13,14] They are at an increased risk of bleeding which may necessitate treatment cessation. Less than one-third patients require dual-antiplatelet therapy for patients who undergo TAVR with percutaneous coronary intervention (PCI) and stenting. Patients with THV and AF or with high CHA2DS2-VASc scores require anticoagulation rather than clopidogrel.

CORONARY ARTERY DISEASE POST TAVR

The incidence of acute coronary syndrome (ACS) following TAVR is approximately 10% after a mean follow-up period of 2 years. Vilalta et al. in their study of 774 over 25 months follow-up showed that 10% of patients had ACS in TAVR cohort^[15] with majority occurring within a year post-TAVR. Non ST elevation myocardial infarction (NSTEMI) was the most common presentation. Prior history of coronary artery disease or revascularization, presence of diabetes, acute kidney injury, and VIV^[16] were predictors of ACS. ACS post–TAVR has poor prognosis with very high in-hospital (10%) and late mortality rates. It is mainly related to difficult coronary access.^[17] ST-elevation myocardial infarction (STEMI) following TAVR is associated with high mortality rate. One-third of STEMI patients do not survive beyond 30 days. In a patient with stable coronary artery disease, timing of PCI is dependent on whether the patient is symptomatic and whether the lesion is proximal with demonstrable ischemia [Figure 3].

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Figure 3:

Timing of PCI in patients with stable CAD. (PCI: Percutaneous coronary intervention, TAVR: Transcatheter aortic valve replacement, CAD: Coronary artery disease).

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Nuances of coronary access

A baseline root aortogram may help delineate the coronary anatomy in relation to the THV. Left anterior oblique projection is used for delineating the origins of left main coronary artery (LMCA) and right coronary artery (RCA). Standard catheters can be used to engage BEVs. A case example is given in Figure 4.

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Figure 4:

A 70 year old lady had new onset regional wall motion abnormalities on echocardiogram a year following TAVR with balloon expandable valve with class II effort angina. Panel a] non selective left sinus angiogram. Panel b and c] guide catheter engagement and near selective angiogram following wiring of LCX. TAVR: Transcatheter aortic valve replacement, LCX: Left circumflex artery.

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Post-TAVR coronary angiographic study showed that coronary ostia were anatomically in unfavorable position (coronary ostium was below the upper part of the skirt or in front of the commissures of the TAVR valve) in 8% (RCA) to 15% left coronary artery (LCA) of cases with Sapien-3 valves, compared with 25% (RCA) to 35% (LCA) of cases with Evolut valves.^[18]

Cannulation failure rate of 7.7% was noted mostly with Evolut valve in reobtain coronary ostia cannulation beyond transcatheter aortic valve stent (RE-ACCESS) study^[19] where coronary angiography was systematically performed in post-TAVI cases. The study comprised one-third Evolut valve, one-third Sapien 3 valve, and one-third Accurate Neo valve.

The uppermost cell closest to the coronary ostia should be used to engage the coronaries in a self-expanding valve. The preferred access route is the right radial artery, followed by the right femoral artery. It is important to exchange catheters while being visually guided by a J-tipped 0.035 Teflon wire under fluoroscopy. It is important to direct the Teflon wire within the valve frame and not outside of it. Half-size smaller Judkins left catheter is preferred for engaging the left coronary artery, followed by the Judkins right 4, Ikari left 1/1.5 catheter. Extra back up catheters have to be avoided as they are at risk of entrapment in the valve frame. The Judkins right catheter, Ikari right 1.0, Multipurpose, and Amplatz right catheters are preferred for engaging the right coronary artery.

Non-selectively wiring the coronary vessel and later threading the guide extension and guiding catheter on the wire will facilitate selective angiography. Otherwise, a coronary wire can be introduced while the guide catheter is non-selectively engaged, and a short low profile balloon can be introduced on the wire. The wire and balloon shaft provide the necessary support for selectively threading the guide catheter. Second option is to balloon anchor the wire in a side branch and thread the guide catheter for selective intubation.

SVF OF THV

Structural failure (SVF) of TAVR valves is very rare. The causal pathology for structural degeneration of THV is very similar to that of surgical bio-prostheses [Table 4]. Chronic mechanical stresses on the leaflet tissue, glutaraldehyde fixation, residual leaflet antigenicity, and systemic atherosclerosis may also contribute to the pathogenesis of structural valve failure.^[22,23] It can present with severe aortic stenosis as a result of severe leaflet calcification or pannus formation and can also present with severe aortic regurgitation (AR) due to cuspal rupture. Multimodality imaging may be required to differentiate it from prosthetic valve thrombosis. The treatment of choice is valve replacement. Asymptomatic cases are managed conservatively; symptomatic patients are advised to undergo surgical aortic valve replacement.

Table 4: Risk factors for SVF

No patients in either the surgical or transcatheter groups had structural degeneration in the PARTNER trial (Cohort A) at 2 years of follow-up. Long-term data will be required to demonstrate the true incidence of SVF associated with TAVR. It may be difficult to accurately assess the SVF rates in elderly high-risk TAVR recipients. Valve durability is related to the age of the patient at the time of implantation and the time since implantation. Randomized study data are not available in elderly high-risk group. Aortic regurgitation is classified as valvular and paravalvular [Figure 5].

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Figure 5:

Mechanism of AR. (AR: Aortic regurgitation).

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POST-TAVR AR

The incidence of moderate-to-severe AR is seen in 11.7% of patients. It increases the risk of all-cause mortality and morbidity. The natural course of AR is it may remain stable, decrease, or increase over time. Echocardiography allows semi-quantitative assessment by assessing the ratio of AR jet width relative to LVOT diameter [Table 5].

Seller’s angiographic criteria can be used to assess AR severity perioperatively by assessing the degree of the left ventricular opacification.

CONDUCTION ABNORMALITIES

• Conduction abnormalities normalize in more than half of patients in few days. About 6% (4–13%) of patients however require a permanent pacemaker implantation.

• A higher prosthesis-to-LVOT diameter ratio and post-dilatation of the THV system were significantly associated with permanent pacemaker (PPM) implantation in self expanding valve (SEV).

• High-degree conduction defects are frequently seen with the self-expanding core valve (38–57%) and they often persist at hospital discharge and at 1-year follow-up.

• Pre-existing right bundle branch block (RBBB) is a predictor of pacemaker requirement and mortality at follow-up as evidenced in OCEAN TAVI trial.^[27]

• 10–13% of individuals undergoing TAVR have preexisting left bundle branch block (LBBB). The mere presence of LBBB has not been correlated with PPM requirement. A meta-analysis has shown that new-onset LBBB increases the risk of cardiac death.^[28]

• New-onset conduction disturbances hinder the recovery of ejection fraction and left ventricular remodeling.^[29,30]

• Post-TAVR increase in the PR interval was found to be a predictor of late pacemaker implantation in a study by Mangieri et al.^[31]

• Continuous electrocardiogram (ECG) monitoring is recommended for a minimum of 48 h before being discharged for all patients who exhibit a new LBBB

• The criteria for long-term follow-up remain somewhat unclear; however, it is essential to perform an ECG at each follow-up visit. ECG, Holter monitoring, and external loop recorders can be considered in the presence of conduction disturbances.

POST-TAVR LATE STROKE

Ischemic stroke may occur perioperatively or during follow-up. In the SWISS-TAVI registry of 11,957 patients,^[32,33] the 30-day cumulative incidence of stroke was 3.0%. About 69% of strokes occurred within 48 h after TAVR. The incidence at 1 year was 4.3% and increased to 7.8% at 5 years. The 30-day incidence of stroke was higher in TAVR patients as compared with medical and surgical ones in the PARTNER trial.

• TAVR versus medical therapy 6.7% versus 1.7% (P = 0.03);

• TAVR versus SAVR in 5.5% versus 2.4% (P = 0.04).

• Late strokes are of thromboembolic origin. It could be due to concurrent AF or due to subclinical thrombosis.

LATE EMBOLIZATION OF PROSTHETIC VALVE (LPE)

• It is of very rare occurrence. Embolization is usually to left ventricle in 89% of cases, and rarely to the ascending aorta.^[34,35]

Risk factors for LPE are as follows:

• Prosthesis under-sizing, or under-expansion due to aortic root calcification,

• Unstable prosthetic positioning,

• Lower implant depth into the LVOT,

• Insufficient prosthesis anchoring due to large annular calcification,

• Bicuspid valve anatomy,

• Pre-existing mitral prosthetic valve,

• Basal septal bulging.

  • The timing of LPE varies from as early as 2 days to more than a year in its occurrence. It results in acute left ventricular failure and/or cardiogenic shock and mostly patients do not survive.

  • Moderate paravalvular regurgitation in conjunction with high transvalvular gradients should arouse the suspicion of probable LPE. Emergent surgery is the treatment of choice.

PROSTHESIS COMPRESSION

• It consists of mechanical deformation of the prosthesis due to external chest compression after attempts at cardiopulmonary resuscitation (CPR). The rarely reported cases^[36] have been with the BEV.

  • It should always be looked for after CPR in patients with THV with BEV. Reported cases are with Sapien valve^[37-39] as Stainless steel and Cobalt chromium (XT) do not have shape memory. It is therefore pertinent to give chest compressions in the left hemithorax than the conventional site to avoid this rare but albeit potential complication.

  • One potential treatment option for prosthetic compression after resuscitation, although reported in only a single case, may involve the re-dilatation of the prosthesis.

PROSTHESIS DURABILITY

Theoretically, the durability of a TAVR prosthesis should be comparable to that of a surgical bio-prosthesis. Durability of the valve is a function of time lapsed after implantation of the valve and the age of the patient at the time of implantation. Durability also varies depending on whether patients are at low-risk, intermediate-risk, or high-risk category.

In a published series, only 3.4% of patients developed a moderate stenosis at 5-year follow-up. The Nordic aortic intervention trial^[40] was the first to randomize patients of low risk to TAVR versus SAVR. STS score was 3 ± 1.7%. The patient’s mean age was 79 years and showed no difference in 5-year follow-up for composite outcome for TAVR and SAVR. Greater valvular regurgitation and pacemaker requirement were noted in the TAVR group whereas risk of bioprosthetic failure was similar. No randomized data exists for high-risk elderly TAVR patients as the valves tend to outlive the patient.

POST-TAVR SURVIVAL

The overall survival of TAVR population in the Denmark registry involving 2670 patients majority of whom had self-expanding valve was 58% at 5 years and 20% at 10 years.^[41] TAVR in low-risk patients data will help us understand the survival rates in the future.

TIMING OF NON-CARDIAC SURGERY FOLLOWING TAVR

In a cohort study involving 300 patients who underwent TAVR, it was observed that these patients are able to safely undergo non-cardiac surgery shortly after the TAVR procedure when necessary. Patients with moderate-to-severe paravalvular regurgitation and patient-prosthetic mismatch had increased adverse events.^[42]

CAN A PATIENT WITH TAVR UNDERGO MRI?

All prosthetic heart valves, mechanical or bioprosthetic, and all co ronary stents are considered safe in the magnetic resonance (MR) environment at field strengths of up to 1.5 Tesla^[43] regardless of the value of the spatial gradient magnetic field. It is also prudent to read the package insert label regarding the safety of the device with respect to MRI.

The MRI examination must be performed using the following parameters:^[44]

• Whole body averaged specific absorption rate of 2 W/kg, operating in the normal operating mode of the MR system

• Maximum imaging time of not more than 15 min per pulse sequence (multiple sequences per patient are allowed).

CONCLUSION

Post TAVR care needs to be regularly monitored for achieving long term success. It is important to be aware of the challenges that can arise and ways to tackle them.