As a cardiologist, your expertise is vital in supporting the Heart Team to make the right treatment choices for your patients
Accurately identifying and referring patients requiring treatment for severe aortic stenosis is essential to ensure the Heart Team can formulate the best treatment plan for your patient before their prognosis worsens. Read on for further up-to-date information in light of the 2017 ESC/EACTS (European Society of Cardiology/European Association for Cardio-Thoracic Surgery) Guidelines for the management of valvular heart disease.1
Defining severe Aortic Stenosis
The 2017 ESC/EACTS Guidelines provide an updated definition of severe aortic stenosis, which is now stratified into low-gradient and high-gradient severe aortic stenosis. The guidelines recommend using a step-by-step and integrated approach (as shown below) for the clinical diagnosis of severe aortic stenosis, which includes measurement of transvalvular velocity/gradient, valve area, valve morphology, flow rate, left ventricular morphology and function, blood pressure and symptoms.1,2 Use of this step-by-step approach is necessary to ensure patients with a more complex manifestation of aortic stenosis (e.g. low gradient severe aortic stenosis), have the best chance of being identified.1,2
Assessing Aortic Stenosis severity
Doppler echocardiography is preferred for the assessment of aortic stenosis severity.1
- Confirm stenosis
- Indicate the degree of valve calcification, left ventricular function and wall thickness
- Detect the presence of other associated valve diseases and aortic pathologies
Factors to consider during echocardiography are:
- Valve area
- Flow rate
- Mean pressure gradient
- Ventricular function
- Ventricular size and wall thickness
- Degree of valve calcification
- Blood pressure and functional status
Hypertensive patients should be reassessed when normotensive1
When is aortic valve replacement (AVR) appropriate?
- Symptomatic patients with severe, high-gradient aortic stenosis (mean gradient ≥40 mmHg or peak velocity ≥4.0 m/s).
- Symptomatic patients with severe low-ﬂow, low-gradient (<40 mmHg) aortic stenosis with reduced ejection fraction and evidence of ﬂow (contractile) reserve excluding pseudosevere aortic stenosis (see previous figure on ‘Assessment of aortic stenosis (AS) severity’).
- Symptomatic patients with low-ﬂow, low-gradient (<40 mmHg) aortic stenosis with normal ejection fraction after careful conﬁrmation of severe aortic stenosis
- Symptomatic patients with low-ﬂow, low-gradient aortic stenosis and reduced ejection fraction without ﬂow (contractile) reserve, particularly when computed tomography (CT) calcium scoring conﬁrms severe aortic stenosis.
What about asymptomatic patients?
- The majority of asymptomatic patients should be put on watchful waiting and periodically re-evaluated. However, in special cases some patients may be referred to the Heart Team for treatment of their aortic stenosis.1
- Patients with LVEF <50% may be considered for treatment.
- In patients with LVEF >50% who remain physically active, an exercise test is recommended to identify those with abnormal results, such as the appearance of symptoms related to aortic stenosis or a decrease in blood pressure below baseline.
- In asymptomatic patients who are unsuitable for exercise testing, there are special cases where referral to the Heart Team is recommended. This includes patients at low surgical risk with the following risk factors:
- peak velocity >5.5 m/s
- severe valve calcification with peak velocity progression ≥0.3 m/s per year
- markedly elevated neurohormones (>threefold age- and sex-corrected normal range) without other explanation
- severe pulmonary hypertension (systolic pulmonary artery pressure >60 mmHg).
Intervention should not be performed in patients with severe comorbidities when it would be unlikely to improve quality of life or survival.1
Assessing surgical risk – your role in ensuring optimal treatment
Assessment of surgical risk is an important consideration in the development of a patient’s treatment plan by the Heart Team.
Tools such as the EuroSCORE I, EUROSCORE II and the Society of Thoracic Surgeons (STS) score can be used to discriminate between patients suitable for transcatheter aortic valve implantation (TAVI) or surgical aortic valve replacement (sAVR) but both have major limitations for practical use. These limitations include, but are not limited to, an insufficient consideration of disease severity and the exclusion of major risk factors including frailty, porcelain aorta and chest radiation.1
Although EuroSCORE II better predicts 30-day mortality and (along with the STS score) can more accurately discriminate between high- and low-risk patients than EuroSCORE I, the 2017 ESC/EACTS Guidelines still reference the use of EuroSCORE I as it has been used in many previous TAVI studies/registries.1
Other important patient considerations when assessing a patient’s surgical risk and optimal treatment modality include:1
Frailty is an important parameter in assessing surgical risk
Frailty is associated with increased morbidity and mortality after sAVR and TAVI. Age alone does not determine frailty, meaning careful assessment is important. To help ensure that the Heart Team makes the best choice of intervention, this assessment should rely on a combination of different objective estimates. Several tools (e.g. the Essential Frailty Toolset) can provide objective estimates of frailty and should be used in preference to a subjective assessment of frailty such as the ‘eyeball’ test’.1
Guiding the best intervention
Due to the poor prognosis of untreated severe aortic stenosis, patients should be considered for AVR, with early therapy strongly recommended.1 According to the 2017 ESC/EACTS Guidelines, TAVI is currently recommended in patients considered not suitable for surgery by the Heart Team, based on the presence of severe comorbidities. In patients at increased surgical risk (STS ≥4%), various clinical, anatomical and technical aspects form the evidence base for the Heart Team’s decision between the use of TAVI and sAVR and these are summarised below.
Of note, the updated ESC/EACTS guidelines now recommend that TAVI should be favoured over sAVR in elderly patients (aged ≥75 years) at increased surgical risk, especially when transfemoral access is possible. In patients at low surgical risk (STS <4%), sAVR remains the recommended treatment option