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Aortic Valve Disease in the 2017 Focused Update: Questions Answered and Questions Raised

The publication of the 2017 Focused Update of the 2014 American Heart Association (AHA)/American College of Cardiology (ACC) Guideline for the Management of Patients with Valvular Heart Disease provides an opportunity for clinicians to reflect upon how closely their decision-making matches recommendations and to reconcile points of departure. The update includes new recommendations and changes to guidelines regarding the management of patients with aortic valve disease, treatment of bioprosthetic valve failure, and medical therapy of patients with valve disease or undergoing valve replacement (Table 1). In particular, the management of patients with aortic stenosis (AS) is undergoing rapid transition due to the maturation of transcatheter aortic valve replacement (TAVR), the changing nature of the patient population, and the availability of high-quality randomized controlled trials and large prospective registries reporting shortand long-term outcomes. The recognition of agedependent differences in the natural history of AS and the still incompletely characterized syndrome of low-gradient severe AS complicate decisions regarding timing and type of treatment. Comorbidities and advanced age make the assessment of risks and benefits a multidisciplinary exercise. It is therefore not surprising that the 2017 Focused Update introduces additional complexity into the decision-making algorithm for the treatment of AS in patients of intermediate and high surgical risk. Randomized trials have clearly established the non-inferiority of TAVR relative to surgical aortic valve replacement (SAVR) with respect to survival, disabling stroke, and improvement in quality of life in these patient populations. Recent trials and registry data have further demonstrated that improvements in technique and technology have reduced rates of mortality and disabling stroke with TAVR and have suggested possible superiority of transfemoral TAVR. The 2017 Focused Update therefore assigns TAVR a Class I recommendation for high-risk patients with symptomatic severe AS and a Class IIa recommendation for intermediate risk patients. However, in light of the subsequent publication of the randomized SURTAVI trial, reaffirming the non-inferiority of TAVR in intermediate risk patients, the latter recommendation now already appears to be overly conservative. This highlights an important problem with the guideline writing process, in which recommendations can quickly become outdated in a rapidly evolving field. In view of the current evidence, it would seem most rational for SAVR to be recommended in low-risk patients and both TAVR and SAVR to be recommended with equal strength in high and intermediate risk patients. A shared decision-making process, involving the heart valve team and focused on patient age and preferences, should inform individual judgments regarding the importance of a less invasive procedure versus limited data regarding TAVR durability beyond 5 years. The 2017 Focused Update does not change recommendations for the treatment of patients with asymptomatic severe AS. Given the lack of randomized data comparing TAVR or SAVR with medical follow-up in this population, it is unclear why the recommendation for treatment of asymptomatic patients with very severe AS (peak velocity ≥ 5.0 m/s, mean gradient ≥ 60 mmHg) is restricted only to SAVR. A recent prospective registry demonstrated that 43% of older patients (>age 70) with severe AS and low to intermediate surgical risk under clinical and echocardiographic 6-month follow-up at a valve center transitioned from being asymptomatic to highly symptomatic (class III/IV) without passing through a phase of mild (i.e. class II) symptoms. This was particularly true when very severe AS (peak velocity ≥ 5.0 m/s) was present. Importantly, advanced symptoms at presentation were also associated with increased 30-day and long-term mortality after AVR. The current indications for asymptomatic patients reflect markers of rapid progression to symptoms, which should be relevant regardless of treatment assignment to TAVR or SAVR. Indeed, new randomized trials are planned to examine the potential benefits of earlier treatment of asymptomatic patients with either SAVR or TAVR (NCT03042104, NCT02436655, NCT01161732). The 2017 Focused Update does not modify recommendations for the management of low-gradient (LG) (mean gradient < 40 mmHg, maximum velocity < 4 m/s), severe AS (valve area < 1.0 cm, indexed valve area < 0.6 cm/m). Since the release of the 2014 guidelines, however, several publications have examined the common clinical dilemma of patients with LG severe AS and normal ejection fraction. These studies have added to the conflicting data on the natural history and the relative benefit or lack thereof of valve replacement in this population compared to patients with classical high gradient AS and moderate AS.