Aortic Valve Replacement for Aortic Stenosis with Syncope
Patients with severe aortic stenosis and syncope should undergo urgent aortic valve replacement, as this represents a Class I indication with Level B evidence, and syncope in this context signals dramatically worsened prognosis with rapid clinical deterioration. 1
Immediate Surgical Indication
Symptomatic patients with severe AS presenting with syncope require urgent surgery and should not have intervention delayed. 1 The presence of syncope, along with angina or dyspnea, marks the transition from the relatively benign asymptomatic phase to a high-risk symptomatic phase where prognosis deteriorates rapidly 1. Once any of these cardinal symptoms appear, the risk of sudden cardiac death increases substantially, ranging from 8-34% in different studies 1.
Defining Severe Aortic Stenosis
Surgery is indicated when syncope occurs in the context of severe AS, defined by 1:
- Aortic valve area <1.0 cm² (or indexed area <0.6 cm²/m² BSA)
- Peak velocity ≥4.0 m/s
- Mean gradient ≥50 mmHg
Critical Distinction: Syncope on Exertion vs. Rest
The mechanism and timing of syncope provides important prognostic information 2:
- Syncope on exertion is typically hemodynamic in nature, caused by inability to augment cardiac output during exercise, and completely resolves after valve replacement 1, 2
- Syncope at rest may have alternative etiologies (arrhythmic, neurocardiogenic, conduction disease) and recurs in approximately 38% of patients post-intervention, requiring thorough evaluation before proceeding to valve replacement 2
Before attributing syncope solely to AS, other causes must be considered and excluded, particularly in patients with syncope at rest. 1
Syncope as a High-Risk Marker
Recent evidence demonstrates that syncope represents an underestimated threat in AS, associated with significantly worse outcomes after surgical aortic valve replacement compared to other symptoms 3. Patients with pre-operative syncope have:
- Adjusted hazard ratio of 2.27 for 1-year mortality after surgery 3
- Adjusted hazard ratio of 2.11 for 10-year mortality after surgery 3
- Smaller aortic valve areas, smaller cardiac cavities, and lower stroke volumes compared to patients without syncope 3
Importantly, dyspnea, angina, and reduced left ventricular function were NOT associated with worse post-operative outcomes, making syncope a uniquely concerning symptom 3.
Asymptomatic Patients with Positive Exercise Testing
Asymptomatic patients with severe AS who develop syncope during exercise testing should undergo surgery (Class I, Level C). 1 Similarly, those with a fall in blood pressure below baseline during exercise should be considered for surgery (Class IIa, Level C) 1.
Special Circumstances
Low Ejection Fraction
Regardless of symptoms, surgery should be performed when systolic LV dysfunction (LVEF <50%) is present in severe AS, unless due to other causes (Class I, Level C). 1 Even patients with severely reduced ejection fraction (mean 0.37) and clinical heart failure show dramatic improvement in LV function after valve replacement, with ejection fraction increasing from 0.34 to 0.63 post-operatively 4.
High Surgical Risk Patients
For patients with prohibitive surgical risk (≥50% mortality or irreversible morbidity at 30 days), transcatheter aortic valve replacement (TAVR) is recommended as an alternative 1. TAVR has proven safe and effective in reducing perioperative risk for severe AS patients requiring major non-cardiac surgery 5.
Urgent Non-Cardiac Surgery
When patients with symptomatic severe AS require urgent elevated-risk non-cardiac surgery and cannot undergo definitive valve replacement first, balloon aortic valvuloplasty may be considered as a bridging strategy 1, 6.
Common Pitfalls
- Do not delay surgery in symptomatic patients for medical optimization - symptomatic patients require urgent surgery, and medical treatment is reserved only for non-operable patients 1
- Do not assume all syncope in AS patients is valve-related - particularly with syncope at rest, evaluate for arrhythmias, conduction disease, and neurocardiogenic causes 2
- Do not use vasodilators (ACE inhibitors, ARBs) liberally - these may cause substantial hypotension in severe AS and should be used with great caution 1
Prognosis Without Intervention
The natural history is stark: sudden cardiac death is rare (3-5%) in asymptomatic patients but increases dramatically once symptoms develop 1. In asymptomatic patients followed for 2.5 years, sudden cardiac death did not occur in any of 123 patients, but once symptoms appeared, cardiac mortality increased substantially 1.