Raymond J. Strobel and Kenan Yount
Indications
Transcatheter aortic valve replacement (TAVR) has revolutionized the treatment of severe, symptomatic aortic stenosis (AS). Initially introduced in 2002 for patients deemed to not be candidates for a surgical aortic valve replacement (SAVR), TAVR is now available to patients across the spectrum of surgical risk and is the dominant technique for aortic valve replacement nationally.
In the United States, the Federal Drug Administration (FDA) has approved TAVR for use in severe, symptomatic AS patients of high (>8%), intermediate (~3-8%), and low (<3%) Society of Thoracic Surgeons (STS) predicted risk of mortality (PROM), in addition to inoperable/extreme risk patients (>50% preoperative risk of mortality and morbidity at 1 year). The intermediate and low-risk trials had a mean age in the mid-70s with an extreme minority of patients with less than 65 years of age. Given that valve durability is a higher priority in younger patients, who typically have a longer life expectancy, societal guidelines for such patients are still evolving. At present, SAVR is generally preferred under the age of 65 in the absence of high risk surgical comorbidities. AHA guidelines suggest TAVR and SAVR are both effective approaches to AVR in adults 65 to 80 years of age with factors such as vascular access, valve anatomy, comorbid cardiac and noncardiac conditions, expected functional status and survival after AVR, and patient preferences to be considered to guide decision making. Generally, over the age 80, TAVR should be considered first-line unless there are other considerations precluding TAVR.
Important contraindications to TAVR include patients with a subaortic membrane, endocarditis, intra-cardiac mass/thrombus, prohibitive access, mobile aortic atheroma, and isolated aortic insufficiency (AI without associated stenosis).
Bicuspid aortic valve anatomy continues to be a topic of debate. The Sievers classification below can help guide vocabulary, but the reality is that bicuspid disease occurs on a spectrum rather than as a binary condition. Bicuspid valves were excluded from the randomized TAVR trials but have yet to be excluded by the FDA. Generally, bicuspid aortic valves are associated with bulkier calcium, aortopathy or aneurysm (that may need to be addressed surgically), younger patients, eccentric annular shapes, mixed AS/AI mechanism, and horizontal aortas. Consequently, TAVR for bicuspid aortic valve stenosis is thought to be associated with slightly higher rates of stroke, annular rupture, paravalvular leak, and pacemaker implantation, and thus patients with higher risk bicuspid features and eccentric anatomy should be at least offered surgery. Further randomized studies comparing TAVR to SAVR for this population are being considered.
Sievers Classification of Bicuspid Aortic Valves
| Type | Definition | # of Raphe(s) |
| Type 0 | Congenitally bicuspid valve | 0 |
| Type 1 | Acquired fusion (L/R fusion is most common) | 1 |
| Type 2 | Acquired fusion | 2 |
Preoperative planning
Critical to successful TAVR is the full implementation of the Heart Team model, which includes close collaboration between interventional cardiology and cardiac surgery with shared decision-making.
Patients being evaluated for TAVR vs. SAVR will typically present to valve clinic with a transthoracic echocardiogram documenting severe aortic stenosis. Patients with reduced ejection fraction, and discordant echocardiographic evidence of aortic stenosis (Aortic valve area <1.0 cm2 and mean transaortic gradient <40 mm Hg, or vice-versa) should undergo dobutamine stress echocardiogram. Peri-procedural risk is estimated utilizing STS PROM, as well as markers of frailty. Markers of frailty include unintentional weight loss, sedentary lifestyle, exhaustion, grip strength and 5-meter walk test. Increasing STS PROM and frailty favor TAVR.
A multi-phase, multi-planar, cardiac-gated computed tomography angiography (CTA) of the chest/abdomen/pelvis with bilateral femoral runoff (often referred to as a “TAVR CT”) is utilized for valve measurements, as well as to guide vascular access planning. This is a thin slice (<1mm thickness) CT with cardiac-gating to allow for sizing of the aortic annulus during early systole, at which point it will be its largest. Cardiac magnetic resonance imaging (MRI) or transesophageal echocardiography (TEE) are alternatives for valve sizing for patients whose renal function precludes CTA. Non-contrast vascular CT C/A/P, time of flight MRI, or intravascular ultrasound can be utilized in these patients for assessment of vascular access. Pulmonary function tests should be obtained to rule-out pulmonary contribution to symptoms. Coronary angiogram is also crucial as the presence of concomitant coronary artery disease may favor SAVR; for low-risk patients who have no calcium on preoperative images, sometimes TAVR-CTA alone may suffice.
Sizing of the valve is critical as it directly influences the risk of intra- and postoperative complications associated with TAVR. Note that the balloon expandable systems (e.g., SAPIEN) rely on aortic valve area for sizing, whereas the self-expandable systems (e.g., Evolut) utilize valve perimeter.
Several scenarios may warrant “undersizing”:
- Severe annular calcification – poses a risk for annular rupture with increasing radial force imposed on the root.
- Narrow aortic root/shallow sinus/low coronary ostia/bulky native leaflets – pose risk for coronary occlusion. Typically, a minimal coronary ostia height of 10 mm is used for safety, although a height <10 mm may be tolerated if the sinuses of Valsalva are deep.
- Porcelain aorta – poses risk of aortic rupture or dissection.
- Annular calcium burden – if minimal, oversize to 10%. If moderate, oversize to 5%. If severe, true size.
Transfemoral access is by far the favored and most common site of access. Common femoral diameter must be 5.0-5.5 mm to accommodate the sheaths necessary for device delivery. Other complicating anatomical features to consider in evaluating vascular access include:
- Vessel tortuosity: increased risk if calcium present in outer curve of a tortuous vessel
- High burden of calcification (>270◦)
- Common iliac calcification
Alternative access includes transcarotid, transaxillary, or transsubclavian arterial access. Transapical delivery has fallen out of favor due to the inferior outcomes (increased morbidity and mortality) observed among this subgroup. Transcaval access is used by highly specialized centers.
Patients with ICDs should have them inactivated, and pacemakers should be placed into VVI mode, prior to TAVR.
Lastly, a plan of action in case of a life-threatening complication requiring ECMO/CPB/emergent SAVR must be defined. This must include the patient’s wishes, as well as the patient’s expected likelihood of survival of said emergent interventions.
Available Devices
The two most commonly used systems are the Edwards SAPIEN and Medtronic Evolut:
| Valve | Mechanism | Deployment Zone | Steer-able? | Recaptur-able? | Stent frame profile |
| SAPIEN 3 Ultra | Balloon-expandable | Intra-annular | Yes | No | 22 mm |
| Evolut PRO+ (CoreValve) | Self-expanding | Supra-annular | No | Yes | 46 mm |
Minimal head-to-head data comparing the systems are available. In low-risk trials, self-expanding valves had higher incidence of permanent pacemaker (17.4% vs 6.5%) and perivalvular leak, relative to balloon-expandable. Conversely, the balloon-expandable valve had a slightly higher risk of annular rupture (0.2%).
Supra-annular deployment may afford better residual gradients, hemodynamics, and minimize the incidence of severe patient-prothesis mismatch. The lower stent frame profile of intra-annular deployment may make future PCI technically easier. The balance of such competing considerations for younger patients undergoing TAVR has yet to be worked out.
Intraoperative technique
Conscious sedation has rapidly become the standard for many patients undergoing TAVR. However, patients with difficult/non-femoral access, those who are “in between” valve sizes, difficult airways, and those with OSA should have a general anesthetic with endotracheal intubation.
The pre-procedural presence or absence of a pericardial effusion should be noted via TTE or TEE.
Percutaneous transfemoral TAVR is the most common access method. This entails bilateral femoral arterial and non-device-side femoral venous access. Percutaneous closure devices are placed prior to dilation of the vessel for the side on which the TAVR is to be deployed. Typically 6 Fr sheath access is obtained in the contralateral femoral artery for aortography. Balloon-expandable systems will require rapid ventricular pacing to prevent ejection of the valve during deployment and all systems typically require some form of back-up pacing, thus a transvenous pacer is typically inserted in the femoral or jugular vein. 70 U/kg of heparin (ACT goal 250-300) is given after access and prior to advancing into the aortic arch. Ascending aortography is obtained, and the valve is then crossed.
For patients who are deemed high risk for coronary obstruction, utilization of coronary protection may be indicated at this point. This entails insertion of a guidewire into the at-risk coronary.
A co-planar view of all 3 sinus nadirs must be obtained prior to balloon valvuloplasty and deployment. Frequently utilized views to obtain this view include straight AP to AP-caudal 20 degrees, slight LAO-cranial, and slight RAO-caudal. An attempt to predict deployment angle utilizing preoperative CTA should be made to save time and contrast load.
If the degree of aortic stenosis is of such severity that the patient may not tolerate the presence of the device in the aortic valve position prior to deployment, consider pre-deployment balloon valvuloplasty (e.g., 20 mm balloon valvuloplasty).
Following valve deployment, aortography and TEE are utilized to assess for perivalvular leak and aortic regurgitation.
Complications and management
Complications secondary to TAVR can be grouped into three general categories – those inherent to the technique, those related to undersizing of the valve, and those related to oversizing of the valve.
General Complications
Vascular injury: Aortic injury proximal to the left subclavian is associated with considerable morbidity and mortality and can manifest as aortic dissection or rupture; intervening surgically depends on the patient’s comorbidities. When a more distal injury is suspect, it is critical to maintain wire access across the suspected site of injury, if at all possible, to help facilitate balloon control of the injury. This will allow for the acquisition of angiograms to aid in guiding management. Iliac artery injuries can sometimes be managed with covered stent rather than open surgical repair, whereas femoral arterial injuries are often repaired surgically with patch angioplasty.
Undersizing Complications
Perivalvular leak (PVL): When greater than mild PVL is seen post-deployment, wait 5-10 minutes prior to making any decision to intervene as this may spontaneously improve immediately following deployment. If greater than mild PVL remains after this period of observation, consider the following interventions: balloon dilation of the valve, deployment of a second valve in a different location, the use of peri-valvular vascular plugs, or revision to a surgical aortic valve replacement if the patient is truly low risk.
Valve migration/embolization: Management of this potentially catastrophic complication depends on patient comorbidities. Endovascular intervention by snaring the valve and stabilizing the embolized valve in the ascending or descending aorta may be warranted in high or prohibitive risk patients, accepting an associated risk of aortic injury/dissection. Lower risk patients should be managed with surgical extraction and SAVR.
Patient-prothesis mismatch: Patients who have high BSA relative to their aortic annulus and root anatomy are at greatest risk. This is quite rare in TAVR.
Oversizing Complications
Annular rupture: Suspect when new effusion, intracardiac shunt, mitral regurgitation, tricuspid regurgitation, or conduction abnormality diagnosed. Hemodynamically stable hematoma can be conservatively managed with reversal of heparin, pericardial drainage, and re-evaluation via CT following the procedure. Hemodynamically significant rupture is an indication for emergent surgical intervention with central cannulation often being most expeditious.
AV block/pacemaker risk: In addition to oversizing, an implantation depth of greater than 5mm, pre-operative right bundle branch block, pre-operative QRS > 140 msec, and valve oversizing ≥ 16% are risk factors for pacemaker requirement. If AV block is encountered in the hybrid OR, consider placement of R IVC transvenous pacemaker to allow for removal of femoral venous line and early ambulation.
Coronary obstruction: Most commonly a result of obstruction by displaced native aortic valve leaflets. Typically, interventional efforts may be used to reopen the occluded artery with PCI. CPR or ECMO may be needed to stabilize the patient in the meantime. In rare instances, surgical bypass and valve extraction may be required.
Postoperative care
A post-operative echocardiogram may be obtained. Patients are continued on telemetry with daily 12-lead electrocardiogram. Electrophysiology consultation is indicated for those a QRS interval >200 msec or an increase of >40 msec from their pre-TAVR baseline. Antiplatelet and anticoagulation regimens vary by institution.
Additional considerations
Valve-in-Valve TAVR (ViVTAVR)
For ViVTAVR, several important caveats bear mentioning. Transesophageal echocardiogram is mandatory preoperatively to assess for perivalvular AI (which will not be addressed by ViVTAVR). The potential for patient-prosthesis mismatch must also be seriously considered, and if likely, weighed against the risk of SAVR. The inner diameter of the indwelling prosthesis should be considered the “annulus diameter” used for sizing of the new device. Special consideration must be given to risk factors for coronary occlusion in these cases, which include those listed earlier in the chapter with the addition of high supra-annular position of the indwelling prosthesis or externally mounted leaflets (e.g., St. Jude Trifecta). Further randomized studies comparing TAVR to SAVR for this population are being considered.
Surgical TAVR-Explant
As TAVR adoption continues to spread, cardiac surgeons will be called upon to explant these devices with increasing frequency. While experience with these operations remains nascent, good outcomes have been reported both with and without root replacement accompanying valve explant and replacement. Important indications for explant (vs. ViVTAVR) include endocarditis, annular rupture or pseudoaneurysm, and perivalvular leak which is unable to be addressed via ViVTAVR or balloon dilation.
Suggested Readings
- Watkins AC, Gupta A, Griffith BP. Transcatheter Aortic Valve Replacement: A How-to Guide for Cardiologists and Cardiac Surgeons. Springer 2018.
- Scarsini R, De Maria GL, Joseph J, et al. Impact of Complications During Transfemoral Transcatheter Aortic Valve Replacement: How Can They Be Avoided and Managed? J Am Heart Assoc. 2019;8(18):e013801.
- Claessen BE, Tang GHL, Kini AS, Sharma SK. Considerations for Optimal Device Selection in Transcatheter Aortic Valve Replacement: A Review. JAMA Cardiol. 2021;6(1):102-112.
- Kumar V, Sandhu GS, Harper CM, Ting HH, Rihal CS. Transcatheter Aortic Valve Replacement Programs: Clinical Outcomes and Developments. J Am Heart Assoc. 2020;9(8):e015921.
- Spears J, Al-Saiegh Y, Goldberg D, Manthey S, Goldberg S. TAVR: A Review of Current Practices and Considerations in Low-Risk Patients. J Interv Cardiol. 2020;2020:2582938.
