Review ArticleLow risk TAVR: Long- term considerations and appropriate patient selection
Introduction
It is estimated that 500,000 patients are currently living with aortic stenosis (AS) in the United States (US) and the prevalence of severe AS is increasing with an aging population.1,2
Prior to the advent of Transcatheter Aortic Valve Replacement (AVR;TAVR), most patients with symptomatic AS were treated with surgical valve replacement (SAVR). Over the preceding decade, rapid advances have been made in the technique and technology used in TAVR.3., 4., 5. The US Food and Drug Administration (FDA) initially approved TAVR for patients determined to be inoperable but has since expanded this to include high, intermediate and, most recently, low surgical risk patients based on high quality outcomes in clinical trials.3., 4., 5., 6., 7., 8.
Despite the sustained benefit of TAVR over SAVR in high and intermediate surgical risk patients, the widespread use of TAVR in low surgical risk patients is of concern. Low risk TAVR patients are generally younger with longer life expectancy. The current trials referenced above have insufficient data on the durability of TAVR valves over time. In this comprehensive review, we outline the potential future long-term considerations and complications of TAVR in low risk patients.
Section snippets
Summary of low risk TAVR trials
In 2019, the PARTNER 3 trial compared balloon expandable TAVR to SAVR in low risk patients. The authors concluded that TAVR had lower rates of the composite outcome of death, stroke, or rehospitalization at 1 year compared to SAVR5 (Fig. 1). TAVR also resulted in lower rates for new onset atrial fibrillation (AF), shorter index hospitalization length of stay (LOS) and lower risk of poor treatment outcome. Major or life-threatening bleeding was also noted to occur less frequently in the TAVR
Long term considerations for low risk TAVR implantation
It is important to evaluate who were those patients who were included in the aforementioned trials. Despite being labeled as “low risk” these patients shared certain characteristics that are of paramount importance to mention: they were mostly in their seventh decade of life, did not have bicuspid aortic valves and were all good transfemoral candidates (Table 1). When discussing with patients the therapeutic options available it is important to recognize the following points.
Structural valve deterioration (SVD)
Durability of the TAVR bioprosthetic valve is among the most important consideration in patients with few co-morbidities who are expected to have a longer lifespan. Prior studies have demonstrated that the durability of surgical bioprosthetic valves are as high as 85% at 10-year follow-up,9,10 including a recent large meta-analysis that showed the lowest and highest reported freedom from SVD was 86% and 96.2%, respectively, at 8 years follow up.11 However, there is significant variability in
Pacemaker implantation
Conduction abnormalities associated with TAVR implantation include complete atrioventricular block, bundle branch block, and AF. These may occur after implantation of TAVR due to the close anatomical proximity of the aortic valve and the intracardiac electrical conduction system.19 The reported pacemaker rate for TAVR and SAVR in prior trials have not shown much difference in the balloon expandable valves,5 however, the self-expanding valve trials showed that TAVR had higher permanent pacemaker
Coronary obstruction
One of the rare, but fatal complications with TAVR is the potential obstruction of either or both ostia of the left and right main coronary arteries. Risk factors for acute coronary obstruction (ACO) and/or delayed coronary obstruction (DCO) include narrow sinus of Valsalva, low coronary height, or VIV procedure.28 Coronary obstruction has been seen more specifically in female patients, patients receiving self-expanding valves, newer generation balloon-expandable valve (due to its higher frame
Subclinical valve thrombosis
Since its discovery in 2013, multiple studies have described subclinical leaflet thrombosis (SLT) in follow-up scans of TAVR patients (Fig. 3). Multi-detector computed tomography (MDCT) has emerged as the gold standard.34 SLT is determined when there is evidence of hypo-attenuated leaflet thickening (HALT) demonstrated on MDCT which are hypo-attenuating defects on the aortic side of the leaflets secondary to a thin layer of thrombus involving one or more leaflets and associated reduced leaflet
Appropriate low-risk patient selection for TAVR vs SAVR
The selected treatment strategy between TAVR and SAVR has been constructed predominantly on the patient's surgical risk for AVR using validated risk scoring systems, including STS-PROM, frailty, major organ system compromise, and procedure-specific impediment. However, there exists special patient populations where the most efficacious and long-lasting approach may favor SAVR or has not been well delineated in current studies.
Bicuspid aortic valves
Bicuspid aortic valve (BAV) disease is the most common congenital heart defect with current prevalence estimated between 0.5% to 2% of the general population.42 Within the population of severe AS, BAVs have been estimated to comprise up to 50% of cases requiring surgical intervention.43 Circular and complete expansion of TAVR valves is paramount for proper valve function following implantation. With noncircular expansion, there is an increased risk of AR, particularly with BAV or unicuspid
Comorbid cardiac conditions
Patients require assessment of preexisting cardiac conditions which may require concomitant intervention. For example, patients with severe multivessel CAD may benefit from SAVR when coronary artery bypass grafts surgery (CABG) is a consideration. Another special population exists in patients with septal hypertrophy which may not only require surgical myomectomy but were excluded from current trials. Current American College of Cardiology/American Heart Association, European Society of
Conclusions
With the expansion of TAVR for low risk severe AS patients, multiple inherent long-term complications should be considered prior to implantation. In addition to patient risk stratification, we suggest the additional assessment of life expectancy. The long-term durability of the TAVR valve remains to be seen in comparison to SAVR. Patients with longer life expectancy should be considered for a longer durability procedure such as a mechanical SAVR.
Disclosures
The authors report no conflicts of interest.
Declaration of competing interest
None.
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