|Year : 2018 | Volume
| Issue : 1 | Page : 9-17
Transcatheter aortic valve implantation: Patient selection and technical considerations for the growing heart teams of India
Director for Interventional Cardiology, HeartTeam India, Chennai, India
|Date of Web Publication||24-Aug-2018|
Dr. A B Gopalamurugan
Director for Interventional Cardiology, HeartTeam India, Chennai
Source of Support: None, Conflict of Interest: None
Transcatheter aortic valve implantation (TAVI) is expanding exponentially across the world as a result of growing positive evidence on its efficacy and outcomes on selected patient cohorts. It is now a class IA indication for high-risk patients with aortic stenosis and class IIA indication for intermediate-risk patients. The guidelines are likely to be updated soon to make TAVI class IA indication for intermediate-risk patients too with the publication of surgical replacement and transcatheter aortic valve implantation trial data. However, given the complexity of this procedure, it is imperative for the heart team involved in the care of these patients to have thorough understanding of the technical aspects of this procedure to allow most appropriate patient selection and the best possible clinical outcomes. This review summarizes key technical considerations influencing patient selection and the outcomes with TAVI.
Keywords: Aortic stenosis, aortic valve replacement, structural heart disease interventions, transcatheter aortic valve implantation, transcatheter aortic valve replacement, valve interventions
|How to cite this article:|
Gopalamurugan A B. Transcatheter aortic valve implantation: Patient selection and technical considerations for the growing heart teams of India. Indian Heart J Interv 2018;1:9-17
|How to cite this URL:|
Gopalamurugan A B. Transcatheter aortic valve implantation: Patient selection and technical considerations for the growing heart teams of India. Indian Heart J Interv [serial online] 2018 [cited 2019 Mar 25];1:9-17. Available from: http://www.ihji.org/text.asp?2018/1/1/9/239776
Transcatheter aortic valve implantation/transcatheter aortic valve replacement (TAVI or TAVR) is expanding exponentially across the world as a result of growing positive evidence on its efficacy and outcomes on selected patient cohorts. The nomenclature “TAVR” and “TAVI” refer to the same treatment but TAVR appears to be the preferred nomenclature in the far West, whereas TAVI is the preferred nomenclature across the European countries. However, from an English language accurateness and the technical procedure from an anatomical perspective, TAVI would indeed be a more appropriate terminology as the artificial valve is “implanted” rather than “replaced” as in surgical aortic valve replacement (SAVR). But from a functional or physiological perspective, the net effect achieved is the replacement of the aortic valve function and therefore, the terminology “TAVR” could equally be argued as appropriate. Now across the world literature, both have become accepted terminologies. In 2011, PARTNER 1 trial showed similar rates of survival in high-risk patients treated with TAVI compared with SAVR, and in 2016, PARTNER 2 trial showed that TAVI was similar to SAVR in intermediate-risk patients.Other trials subsequently in these subsets of patients have shown similar outcomes. As a result, TAVI is now a class IA indication for high-risk patients with aortic stenosis and class IIA indication for intermediate-risk patients. The guidelines are likely to be updated soon to make TAVI class IA indication for intermediate-risk patients too with the publication of SURTAVI trial data.
| Indications for Transcatheter Aortic Valve Implantation|| |
The indications currently for TAVI have been for symptomatic calcific severe aortic stenosis who are at a high risk or intermediate risk for SAVR. The term “high risk” and “intermediate risk” comes from the Society of Thoracic Surgeons (STS) scoring system, which is discussed subsequently in this article. However, there is also a growing evidence for the use of TAVI technology for valve-in-valve procedures for bioprosthesis dysfunction in the aortic position. Following experience and positive outcomes from the valve-in-valve procedures in the aortic position, TAVI technology has now been widely used for valve-in-valve procedures in other valve positions such as tricuspid and mitral, achieving good outcomes in high-risk patients for surgical redo valve replacements.,,,, Although off label, a good number of cases of TAVI are also performed for isolated aortic regurgitation (AR).,This off-label indication has been used in very high-risk patients on compassionate grounds and does carry a significant risk of procedural complications.
| Patient Selection|| |
Heart team: It is most important to understand that TAVI or any transcatheter valve therapy does not come under the specific remit of a cardiologist or a cardiac surgeon. As the subspecialty of transcatheter valve therapy is so large, rapidly expanding, and covers a wide area of various specialties within, it has been a team-based approach comprising various specialists. They include interventional cardiologists, cardiothoracic surgeons, cardiac anesthetist, imaging cardiologist or cardiac radiologist, care of the elderly physician, cardiac rehabilitation team, specialist nurses and technicians, and other specialists on the basis of the patient specifics. This team is referred to as the “heart team.” Involvement of the entire heart team in patient selection, procedural planning, peri-, and post-procedural care delivers the best patient outcomes consistently.
Surgical risk: The current key indications for TAVI are high- and intermediate-risk patients for SAVR as deemed by a heart team. The risk for SAVR has traditionally been calculated using scoring systems, which includes euroSCORE and STS risk score. The large randomized trials have used the STS score and therefore, the guidelines have generated their stance on the basis of the STS score. On the basis of the STS score for procedural mortality, the patients are classed into high risk, intermediate risk, and low risk. The STS score above 8 signifies high-risk, between 4 and 8 signifies intermediate-risk, and less than 4 signifies low-risk patients of SAVR. However, there are various factors that are not captured by the STS score, which are vital in predicting the risk for SAVR and have to be borne in mind. These include chest wall abnormality, hostile mediastinum, liver disease, pulmonary hypertension, aortic calcification (porcelain aorta), dementia, mobility of the patient, and general frailty. It is therefore crucial to understand that there are numerous factors apart from STS score to be borne in mind before selecting a patient for TAVI or SAVR. The Clinical Frailty Scale (CFS) provides a score to ascertain a patient’s frailty. The CFS score ranging from 1 (very fit) to 9 (terminally ill) provides a semiquantitative tool to assess patients. The fact remains that no specific or dedicated scoring system is validated for risk evaluation for TAVI. Therefore, the best practical assessment is through a robust “heart team” who can make a judgment on the patient’s overall risk on the basis of various factors that are not captured by any single scoring system to date.
Age: One of the most important aspects of patient selection is the appropriate age of the patient who can be considered for TAVI. TAVI was originally designed for old patients who were at a high risk for SAVR. For degenerative aortic valve stenosis, which is predominantly beyond the age of 60 years, no maximum age cutoff limit is reported. What would be more relevant is the general condition of the patient, in other words, the biological age, rather than the actual age of the patient. The patients beyond 90 years of age, who are otherwise mobile, and have had a good quality of life may be good candidates for TAVR as opposed to a 65-year-old patient who is predominantly bed bound or is hardly mobile for other reasons. In bicuspid aortic valve stenosis, the patients are younger but they would only qualify for a TAVI if their surgical risk for SAVR is high. TAVI has not been studied in pediatric patients.
To understand patient selection and technical considerations, there are several aspects of a TAVI procedure that one need to consider and evaluate. Sound understanding of all these aspects and meticulous evaluation is crucial for a successful TAVI outcome and to prevent immediate and long-term complications. The key to master them is through structured training and building experience with mentoring. In this article, the key anatomical and procedural factors are discussed alongside their relevant technical considerations, which need to be borne in mind during patient selection. The various devices discussed in this chapter are only confined to TAVI devices available in India until early 2018, which would be relevant for Indian patients. Among the numerous factors to consider, the primary procedural factors requiring consideration for a TAVI are as follows:
- Landing zone
- Aortic valve type
- Left ventricle
- Conduction system
- Access route
- Cerebral protection
- Renal protection
- Management of anticipated complications
| Landing Zone|| |
The “landing zone” for a TAVI in native aortic valve stenosis is a combination of various anatomical structures. They include the aortic annulus, aortic valve leaflets, left ventricular outflow tract (LVOT), aortic sinuses, sinotubular junction, and proximal ascending aorta [Figure 1]. Some structures are more relevant than others, and that is based on the device chosen for TAVI. One of the most important aspects is to know the mechanism of TAVI prosthesis anchoring and stability. The landing zone is the key for any TAVR prosthesis to seat and hold in its position. Various factors have to be considered while assessing the landing zone. In TAVR for native aortic valve stenosis, it is the native aortic valve annulus and leaflets that largely constitute the maximum contact points for the TAVR device at the landing zone. Most TAVR devices rely on two important factors for valve stability and anchoring. They include the radial strength of the TAVR prosthesis and a rigid landing zone for anchoring the valve. This rigid landing zone is provided by the calcium in native aortic valve stenosis that holds the implanted valve in position and prevents it from embolization or migration. Therefore, calcium is an important native aortic valve–related factor, which is necessary for a successful TAVR procedure. It is for this very reason that TAVR is not labeled for use in primary AR as there is rarely any calcium in the native aortic valve complex, and therefore does not offer a rigid landing zone for valve anchoring in these patients. Hence, the only factor for stability and anchoring of most TAVR devices in primary AR with no calcium is the radial strength of the TAVR device, which explains the high risk of migration or embolization of the TAVR valve in these patients. Calcium is both a friend and enemy. As much as one needs calcium for TAVR valve anchoring, too much calcium or calcium in the wrong location can be hazardous. Excessive calcium is associated with a significant risk of paravalvular leak, especially if it is irregularly distributed. Although newer generation devices have addressed these with some paravalvular reduction measures, they have not completely negated this potential adverse outcome. It is worthwhile bearing in mind that Calcium in the LVOT has been a predictor for LVOT rupture, especially with balloon-expandable TAVR valves [Figure 2]. The most reliable way of assessing the landing zone to evaluate all these factors would be with a gated cardiac computerized tomography (CT) scan. Echo, indeed, offers a valuable real-time data, but data on calcium distribution, coronary assessment, and multiplane reconstruction combined together are better achieved with CT imaging. In valve-in-valve TAVR, which is predominantly for dysfunctional prosthesis, the rigid landing zone is offered by the previously implanted surgical valve. Therefore, stability and anchoring is usually not a major concern as long as the TAVI valve is positioned appropriately within the dysfunctional bioprosthetic valve. To enable this, sound knowledge of the bioprosthetic implanted is vital.
|Figure 1: Various anatomical structures that form the landing zone are visualized on this CT scan image|
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|Figure 2: CT scan image demonstrating LVOT calcification, which is a risk factor for LVOT rupture during TAVI valve implantation|
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Relevant technical considerations: If the degree of calcification is too less, then one would be safer to consider a self-expanding, retrievable, and repositionable system that offers more safety. With fully retrievable systems such as Evolut R (Medtronic, USA) or Portico (Abbott Medical, USA), or Venus A Plus (Venus Medtech, China), one has the ability to recognize any instability or valve migration during deployment and correct them by retrieving and repositioning the valve. This is not possible with balloon-expandable systems. Significant LVOT calcification should prompt avoidance of balloon-expandable systems. Excessive calcification should also raise the option of turning down the patient for TAVI.
| Aortic Valve Type|| |
TAVI was originally studied and evidenced in tricuspid aortic valve stenosis. But it is not uncommon to see bicuspid aortic valve stenosis, especially in Asia and in younger patients [Figure 3] and [Figure 4]. In tricuspid valves, the landing or anchoring predominantly occurs at the true annulus level in addition to some anchoring from the leaflets. However, in bicuspid aortic valves, a significant proportion of anchoring occurs at the leaflet level, predominantly at the leaflet tips. The annulus is often elliptical rather than near circular, which is an important observation to make. Given the heterogeneous nature of bicuspid valves with varying types of cusp fusion, heavy calcification, and asymmetrical valve annulus and orifice, one has to aware of significant problems with TAVI valve expansion in these anatomies. This leads to increase in complications such as inadequate valve expansion leading to valvular AR from the implanted TAVR valve and paravalvular AR in addition to increased risk of device embolization or migration. Attention to valve type is crucial to predict and plan procedural outcomes.
|Figure 3: Demonstration of bicuspid aortic valve as seen on the aortic valve short axis on CT imaging|
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|Figure 4: Demonstration of bicuspid aortic valve as seen on the aortic valve long axis on CT scan|
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Relevant technical considerations: On the basis of the morphology of the bicuspid aortic valve, one has to modify the choice of TAVI valve size. Both balloon-expandable valves and self-expanding valves may be used for bicuspid valves. It is often necessary to undersize and not oversize, as one would do with traditional trileaflet aortic valves. This is because conventional sizing is based on the annulus diameter. Knowing that significant anchoring in these anatomies is at the leaflet level, one may have to undersize and not oversize based on the expected native leaflet orifice area. In addition to these changes in valve sizing, valve positioning during implantation may have to be slightly higher than in conventional trileaflet valve positioning. Bicuspid valves often require balloon pre-dilatation with simultaneous contrast injection, which not only dilates the native valve but also gives some indication on the valve size needed and how the implanted valve is likely to behave. One has to also be prepared for post-dilatation of the TAVI valve if the expansion is not adequate. The success is largely down to pre-procedural imaging assessment in bicuspid valves and demands a lot of procedural expertise.
| Coronaries|| |
Assessment of the patient’s coronary anatomy is an absolute must before embarking on a TAVR procedure. There are two aspects of the coronary tree, which require assessment. The first is the presence of critical stenosis in the dominant coronary vessels. The second is the relation of the coronary ostia to the “landing zone.” Current recommendations are that significant CAD with ≥70% reduction in luminal diameter in major coronary arteries or ≥50% reduction in luminal diameter in the left main coronary artery undergo revascularization before SAVR or TAVR.However, no evidence suggests that revascularization provides any benefit in patients undergoing TAVR who are asymptomatic of angina. The risk of patients undergoing TAVR having a myocardial infarction is very low. A reasonable approach would be to consider FFR-guided revascularization with PCI in the patients with TAVR who are asymptomatic. This may be best performed before or during TAVR. The other important aspect of coronary anatomy is its origin in relation to the landing zone. The vital assessment one has to make is the chance of coronary ostial obstruction during TAVR or after TAVR valve deployment. The risk of coronary ostial obstruction during TAVR for native aortic valve disease is very low. However, it is disastrous when it occurs.,Predictors for coronary ostia obstruction are female gender, use of balloon-expandable TAVR valves, and previous surgical aortic bioprosthesis. In addition to coronary height in relation to the annulus, the diameter of sinus of Valsalva is crucial too. During TAVR, the native aortic valve leaflets are squashed into the sinus of Valsalva. Therefore, if there is little room within the sinus of Valsalva, the native leaflets or bioprosthetic leaflets (in valve-in-valve procedures) can lead to coronary ostial occlusion.
Relevant technical considerations: The imaging modality most studied to assess this aspect is a gated cardiac CT scan. Measuring coronary ostial height is from the annulus to the lower margin of each coronary [Figure 5]. Our practice is to approach any coronary height less than 12mm and any sinus of Valsalva with diameter less than 30mm cautiously. However, this is not an absolute rigid number. The patients with small annulus who are likely to get a 23-mm TAVI prosthesis are likely to be safe even with a sinus of Valsalva (diameter, 28mm). The risk is highest with valve-in-valve procedures in bioprosthetic aortic valves. If in doubt in case of high-risk patients, a useful procedural maneuver is to perform balloon aortic valvuloplasty (BAV) with an appropriately sized balloon for the annulus with simultaneous aortography during BAV to assess coronary flow. This gives a good indication of the possibility of coronary occlusion with the TAVI device deployment. In patients who are at a high risk for coronary occlusion, it is safer to use recapturable and repositionable TAVI devices to allow recapturing the device, should coronary occlusion be evident. But when the patients with high-risk parameters for coronary occlusion have to undergo TAVI, then one option is to have simultaneous coronary angioplasty guide with wire and stent positioned within the coronary artery of concern before deploying the TAVI device. Should there be ostial occlusion, the stent can be positioned ostially and deployed to salvage the situation. With regard to revascularization in coronary stenosis, our approach is that we do not perform PCI in asymptomatic patients (asymptomatic of typical angina) before TAVI, unless there is angiographically critical disease in a dominant vessel.
|Figure 5: Measurement of coronary ostial height from the annulus level on CT scan|
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| Left Ventricle|| |
Poor left ventricular (LV) function is a risk factor for SAVR, making such patients suitable for TAVI. However, very sick ventricles could also pose a risk for TAVI too. This is specifically the case when these ventricles are associated with bicuspid aortic valves that may require multiple sequences of rapid pacing for pre-dilatation, TAVI deployment, and sometimes post-dilatation. The other subgroup of patients with poor ventricles is the patients with fully graft-dependent coronary circulation. In such patients, rapid pacing sequences may lead to stunning of the very sick ventricle leading to fatal drop in cardiac output, requiring chemical or mechanical circulatory support. Coronary blood flow is significantly reduced in graft-dependent patients, leading to decreased myocardial perfusion and poor cardiac output. The other factor to consider within the ventricle is the presence of a sigmoid septum. The patients with a sigmoid septum may pose difficulty at the landing zone and may increase the risk of device migration or embolization.
Relevant technical considerations: In the patients with very sick ventricles, having immediate availability of mechanical support may be useful. We tend to have a primed ECMO circuit and femoral arterial and femoral venous accesses available and ready to go on ECMO, should there be a significant drop in cardiac output. In some patients, we also have ECMO circuit initiated before starting any rapid pacing sequence. This allows safe maintenance of cardiac output throughout the procedure, and thereby maintaining coronary flow and showing positive outcomes in many reported cases.,In the patients with a sigmoid septum, where there is an anticipated possibility of a hyperdynamic landing zone, it may be useful to consider a recapturable device that is deployed with rapid pacing and then leaving the device in place for some time to assess stability before fully releasing the system. This allows for recapturability, in case, migration is observed.
| Conduction System|| |
TAVI continues to risk the possibility of permanent pacemaker implantation (PPI) because of mechanical disruption of the conduction system by the TAVI device. The risk of this complication has been reported to be as high as 25%. PPI is associated with increased morbidity, prolonged stay in intensive care unit (ICU), infection risk, and worsening of heart failure. Complete heart block noted in the peri-procedural period is an indication for PPI.,Predictors for PPI implantation include preexisting first degree AV block, right bundle branch block, left bundle hemiblock, depth of implantation of the TAVI prosthesis in relation to the annulus, and the type of device used. Some conduction abnormalities that develop post-TAVI do recover too, but it is hard to predict which patients will follow this trend. It is important to bear in mind the predictors for PPI and approach such patients accordingly.
Relevant technical considerations: Minimizing ICU/hospital stay and quick mobilization is the key to early recovery. Therefore, the patients left with temporary pacing wires in situ for too long and delaying PPI implantation may not be cost-effective and may delay recovery of the patient post-TAVI. Pacing from the jugular vein using a screw in lead in the RV externalized to a VVI generator allows the patients to mobilize early and also allows one to monitor pacemaker dependency and PPI need. The patients with any high-risk indicators for PPI and who develop any degree of worsening of their conduction system immediately after TAVI may benefit from implantation of a PPI on the same procedure as TAVI. We have implanted PPI before TAVI in the patients who are at a high risk for CHB. In addition, one has to consider implantation of a CRT device if the patients have a preexisting poor LV function.
| Access Route|| |
Vascular complications were as high as 25% with the first-generation transfemoral TAVR systems predominantly because of the caliber of the delivery systems in relation to the patient’s vasculature. Thankfully, this has steeply reduced to minimal numbers with the newer generation delivery systems with smaller calibers and increasing operator experience of predicting and managing vascular complications. Meticulous assessment of the vascular system with a high-quality CT aortogram is the key to predict and manage vascular complications. An important aspect to be noted on the CT scan is the feasibility of safe entry and exit at the common femoral artery level and adequate caliber of the vascular lumen in its entirety from the entry point to the aorta to allow the chosen delivery system. Majority of the transfemoral TAVI procedures in the current era are performed fully percutaneously, and the vascular closure devices used are predominantly Prostar XL and Perclose ProGlide (both Abbott Vascular, California, USA). The choice of femoral closure method is largely operator experience based. Transapical and transaortic routes for TAVI are less common in the current era of low-profile TAVI delivery systems. In the patients with no safe femoral access option, the next choice is largely down to center experience and some patient characteristics. The alternative access routes available include transapical, transaortic, trans-subclavian, and transcarotid routes. There is also the possibility of cavoaortic access, if none of the aforementioned is possible or safe.
Relevant technical considerations: In our center, we have completely come off performing invasive aortograms and peripheral angiograms before TAVI as superior data is available from a good-quality CT aortogram than a two-dimensional cine angiogram. Meticulous analysis of multi-place reconstruction slices of the CT scan is crucial to understand the vascular system and plan the best approach [Figure 6] and [Figure 7]. It is the key to make sure that there is no calcification at the femoral artery entry point, which is required for successful percutaneous closure. It is safer to consider a surgical arteriotomy if the access site at the common femoral level is not optimal. Upfront surgical exposure and subsequent surgical closure are more controlled, safer, and easy for the surgeon than bail-out surgical closure. Transapical access poses the highest risk in the patients with poor LV and poor lung function. Transaortic access may prove a challenge with functioning grafts anastomosed to the aorta and in the patients with severe ascending aortic calcification [Figure 8]. These access approaches for a TAVI are increasingly vanishing because of smaller caliber delivery systems and increasing experience with vascular access site management. Attention to detail on the precise outer diameter of the delivery system in relation to the patient’s vascular lumen diameter in its entirety is the key to predict complications and manage them. Circumferential calcium, where the vessel lumen diameter is smaller than the delivery system, may predict deadly complication of vessel rupture. Switching to alternative access routes may be wiser in such circumstances. Pelvic vessel dissections or ruptures are the common vascular complications, which need meticulous attention. Many pelvic vessel complications may not be clinically apparent until the large delivery sheath is removed. Therefore, it is important to have alternative access (usually, the contralateral femoral artery) available to manage such complications. It is an absolute must to have covered stent grafts and endovascular expertise available to manage such complications. It is paramount not to embark on a TAVI without expertise available in endovascular and aortic interventions and surgery.
|Figure 6: CT aortogram reconstruction demonstrating significant calcification of iliac vessels especially just after aortic bifurcation suggesting transfemoral access for TAVI may not be optimal|
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|Figure 7: CT aortogram reconstruction demonstrating significant calcification at the common femoral artery suggesting suboptimal vascular access at the entry site of this femoral artery|
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|Figure 8: CT scan reconstruction demonstrating patient coronary graft positions and significant calcification on the greater curvature of the distal ascending aorta making transaortic access for TAVI challenging|
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| Cerebral Protection|| |
Embolization of calcific debris during BAV and TAVI is well recognized. The debris originate from the aortic valve complex or the ascending or arch aorta because of the mechanical disruption during the procedure. Although reported high in the early experience of TAVI, the current rates of clinical strokes are minimal. On the basis of current data from the two largest randomized studies namely PARTNER 2 and SURTAVI trails, stroke rates were no different among the patients treated with TAVI or SAVR.,In the SURTAVI trial, the incidence of early stroke was slightly higher in the SAVR cohort favoring TAVI over SAVR. Several cerebral embolic protection devices have been developed and studied [Figure 9]. To date, none of the studies using cerebral embolic protection devices have demonstrated any statistically significant benefit in reducing clinical strokes acutely. This may be possible because of underpowered studies as consistently such embolic protection devices have shown reduction in debris embolizing to the brain and have shown the reduction of silent infarctions to the brain. As a result of these facts, recently, the Food and Drug Administration approved the Sentinel Device (Claret Medical, USA) for cerebral protection from embolic events during TAVI even though there was no new lesion volume on magnetic resonance imaging or strokes within 30 days while using the device compared to controls.
|Figure 9: Cerebral embolic protection devices that have been developed and studied|
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Relevant technical considerations: As of 2018, no cerebral embolic protection devices are available in India for use. Minimizing mechanical contact with the aortic valve complex and the ascending and arch aorta does decrease the possibility of embolization of debris. Therefore, avoiding the steps such as BAV, if feasible, can minimize cerebral embolization. Calcified and diseased ascending aorta and arch aorta pose a risk of mechanical disruption while crossing these areas with the delivery system. Attention to minimize friction and contact with these areas with gentle traction of the stiff wire might help. Adequate planning and minimizing the time spent in the vascular system anywhere proximal to the arch can only be beneficial in minimizing stroke risk.
| Renal Protection|| |
A considerable proportion of the patients for TAVI have renal impairment. Workup for TAVI and the TAVI procedure poses significant risk of either worsening of their renal function or renal replacement therapy because of renal failure. Numerous reasons are present for the renal insult on these patients; however, contrast load and ischemic time to the kidney are the key contributors. Experienced interventional cardiologists are well versed with minimizing the risk of contract nephropathy, and the same precautions are needed for a TAVI. In the patients who are at a high risk of worsening renal function, it may be useful to minimize contrast volume to the bare minimum and at the same time not losing valuable diagnostic information. The minimal imaging data set requiring contrast that would be usually required for an elective TAVR would include a coronary angiogram, a CT aortogram, and a gated cardiac CT for annulus sizing and planning TAVR. The CT scan would have to be a 64-slice CT with 0.5mm slice thickness.
Relevant technical considerations: Over the last few years, experienced centers have developed their own protocols of mitigating contrast nephropathy from TAVI. This is largely down to center availability and experience with various imaging modalities. In our center, a symptomatic patient with echo evidence of severe aortic stenosis, who qualifies for a TAVI, starts with a gated cardiac CT scan and CT aortogram in the same sitting with minimal contrast based on the body weight. To optimize the CT images, we make sure that the heart rate and rhythm is optimal with intravenous (IV) beta blockers or IV calcium channel blocker, if possible. A good-quality gated cardiac CT offers adequate coronary imaging. Unless the CT coronary angiogram shows severe calcification making interpretation of coronary lumen difficult, we do not routinely perform invasive coronary angiogram in the patients with TAVI. If the patients are symptomatic of angina, and CT coronary angiogram shows a significant lesion, then we would proceed with a coronary angiogram and angioplasty as appropriate. Should this be required in high-risk patients for contrast nephropathy, we prefer to do it before the TAVI procedure and wait for a week to allow contrast to be cleared before embarking on TAVI. We never perform invasive angiography of peripheral vessels as a good-quality CT aortogram that includes the peripheral vessels provides much more valuable information from multiplane reconstruction than an invasive angiogram. During TAVI, we take specific precautions to minimize contrast. Wherever possible, we mix contrast volume with 50% saline and perform hand injections. Digital subtraction angiography may be preferred for imaging peripheral vessels during TAVI, which may require minimal contrast. Other precautions that one would take during coronary angioplasty to minimize contrast nephropathy such as IV hydration and N-acetyl cysteine may be added too. In the patients with severe renal dysfunction, attempts to avoid multiple rapid pacing sequences should be taken to minimize ischemic time to the kidneys. If technical aspects allow, using a self-expanding TAVR prosthesis and avoidance of pre-dilation would add benefit to such patients.
| Management of Anticipated Complications|| |
Expecting the unexpected and the ability to manage the unexpected appear to be vital during TAVI or any invasive procedure for that matter. Every patient is different and some potential complications are likely in some than others, on the basis of their pre-procedural workup and technical aspects as described above. It is therefore crucial to study the patient in detail and have a clear schematic of potential complications and management strategy for each patient. This may involve having another specialist available or a specific equipment available. Attention to detail can truly help prevent complications and manage complications effectively when they occur.
Relevant technical considerations: A robust heart team discussion with all the patient data and a protocolar approach may help pick up potential complications, which will allow a robust management plan to be derived in its advance. The members of the heart team as discussed above are invaluable in contributing to this discussion. Complications that are largely vascular complications, requiring immediate attention should be thought about and an immediate plan should be made available. We always make sure that we have a selection of peripheral stent grafts for iliac and femoral artery use in addition to aortic stent grafts. A large soft balloon for distal aorta occlusion such as a 30-mm ASD sizing balloon or Coda Balloon is useful, if there was a distal aortic or aortic bifurcation perforation to control bleeding and maintain hemodynamics temporarily. Expertise in endovascular procedures such as iliac and aortic interventions can be invaluable in managing such complications. Availability to initiate immediate cardiopulmonary support such as ECMO in the catheterization lab or ability to be connected to a bypass machine is an absolute must for any center performing TAVI. Having a selection of large-caliber snares is also a “must keep kit” in the catheterization lab.
The aforementioned is not an exhaustive list but a bare minimal list of patient factors and relevant technical considerations to be borne in mind. However, experience gained from structured training programs for transcatheter valve therapies and good mentoring from an experienced structural interventionist has no comparison toward mastering the art of transcatheter valve therapies. Dedicated courses and didactic lectures are valuable. In India, the dedicated course for transcatheter valve therapies for the entire heart team is “India Valves” (www.indiavalves.in), where all the various device therapies and patient selection techniques and imaging modalities are discussed and demonstrated through live cases, hands-on training, and didactic lectures. As mentioned earlier, attention to detail and learning from others is the key to TAVI or any aspect of interventional cardiology.
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