EM@3AM: Aortic Stenosis

An 83-year-old female presents to the ED with dyspnea at rest following a syncopal episode. Patient reports she was out for a walk with her husband when she began to feel lightheaded, short of breath, and then fainted. Triage vitals include BP 88/50, HR 115, RR 24, O2 98%. ECG is without signs of acute ischemia. On exam, the patient appears slightly tachypneic, with rales noted at bilateral lungs. There is a systolic murmur along with 2+ pitting edema at the lower extremities. Cardiac POCUS shows grossly decreased left ventricular ejection fraction (LVEF) with a hyperechoic structure at the aortic valve.

What is the most likely diagnosis?

Answer: Aortic stenosis causing acute decompensated systolic and diastolic heart failure, and cardiogenic shock.

Epidemiology:

• Affects 2-3% of patients > 65 years old^1-4
• 10% of patients > 80 years old^{2, 4}
• High mortality rate within 2-3 years of symptom onset in untreated patients^{2, 5, 6}
  • About 25% mortality rate per year⁷

Etiology:

• Degenerative
  • Tricuspid valve calcification due to aging (most common cause in developed countries)^{1, 5, 8}
  • Congenital bicuspid valve calcification (earlier symptom onset)^{1, 2, 5, 8}
• Rheumatic Heart Disease
  • Most common cause in developing countries^{1, 2, 5, 8}
  • Fusion of valve commissure ^{2, 5}
  • Usually with concomitant mitral valve stenosis⁸
• Other causes (less common): End stage renal disease, systemic lupus erythematosus, Fabry Disease, unicuspid valve⁵

Pathophysiology²:

• Narrow aortic valve opening => increased pressure gradient across valve => increased LV afterload
• Increased afterload => increased LV hypertrophy to maintain cardiac output
• LV hypertrophy decreases compliance => decreased filling => diastolic dysfunction & decreased stroke volume
• Decreased LV filling and decreased stroke volume => diastolic and/or systolic heart failure
• LV hypertrophy increases myocardial O2 demand and decreases coronary artery filling

Clinical Presentation:

• Asymptomatic during early part of disease; patients can go years without symptoms^{4, 5}
• Later in disease => LV cannot overcome aortic outflow obstruction => develop symptoms^{2, 5}
• Symptoms include angina, exertional syncope, dyspnea, fatigue^{2, 5, 8}

Evaluation:

• Gold Standard: transthoracic echocardiogram (TTE)^{2, 3}
  • Severe stenosis criteria³
    • Valve area < 1 cm¹
    • Peak velocity > 4 m/s
    • Mean gradient 40 mmHg or more
  • Qualitative POCUS can be helpful for hemodynamically unstable ED patient¹⁰
    • Views: Parasternal long, parasternal short, apical 5 view⁴
    • Assess aortic valve appearance⁴
      • Presence/absence of calcification
      • Leaflet mobility
    • Assess LV size⁸
      • LV wall hypertrophy
      • Increased overall LV size compared to RV
    • Estimate ejection fraction qualitatively via visualization ⁸
      • Evaluate for decreased movement of mitral valve and decreased movement of LV wall during systole

• ECG to evaluate for ischemia and LVH²
• CXR to evaluate for pulmonary edema, aortic valve calcification²

Management:

• Resuscitation and stabilization in the hemodynamically unstable patient:
  • Hypotension^{2, 8}
    • Preload dependent and prone to pulmonary edema
      • Administer IVF in small bolus with frequent reassessment of fluid status
    • Vasopressors
      • Phenylephrine is preferred (alpha1 receptor agonist)
        • increases diastolic BP => increases coronary blood flow
        • reflex bradycardia => increased diastolic filling
      • Low LVEF => consider norepinephrine for inotropic effects (alpha1, alpha2, beta receptors)
      • Avoid epinephrine => reflex tachycardia => decreased diastolic filling and increased O2 requirements of myocardium
  •  Tachycardia
    • Avoid beta-blockers and calcium channel blockers => decrease contractility^{2, 8}
    • Avoid epinephrine when choosing vasopressor^{2, 8}
    • Atrial fibrillation with RVR => loss of atrial kick + tachycardia => decreased diastolic filling => decreased preload^{3, 8}
      • Low threshold for cardioversion
  •  Severe decompensated CHF exacerbation^{2, 8}
    • Noninvasive ventilation (NIV)
    • Diuretics (use with caution as patients are preload dependent)
    • Nitrate use for afterload reduction is controversial due to preload reduction since aortic stenosis is preload dependent => consider cardiology consult
  •  Intubation^{2, 8}
    • Resuscitate before you intubate
      • IV fluids
      • Vasopressors
    • Use induction agents with good hemodynamic profile
      • Etomidate
      • Ketamine
• Stabilizing/bridging measures for patients unable to undergo immediate valve replacement²
  • Percutaneous aortic balloon dilatation
  • Extracorporeal membrane oxygenation
•  Definitive treatment: aortic valve replacement^{6, 11}
  • Surgical/open
    • Low and intermediate risk surgical candidates^{1, 3}
  • TAVR (transcatheter aortic valve replacement)^{1, 3}
    • High risk surgical candidates
    • Patients who are not surgical candidates
  • Indications³
    • Symptomatic severe aortic stenosis
    • Asymptomatic severe aortic stenosis plus:
      • Peak velocity > 5 m/s and mean pressure gradient > 60 mmHg
      • LVEF < 50%
      • Undergoing CABG or other heart surgery
      • Abnormal stress test

Disposition:

• Symptomatic aortic stenosis²
  • Unstable:
    • Admit to ICU
    • Consider emergent aortic balloon dilatation
    • Valve replacement once stabilized
  • Stable with worsening symptoms
    • Admit to medicine with telemetry
    • TTE
    • Cardiology consult
    • Evaluation for valve replacement

Key Takeaways:

• Once symptomatic, aortic stenosis has high mortality rate if left untreated.
• Look for aortic valve calcification and decreased valve movement on POCUS.
• Patients with aortic stenosis are preload dependent.
• Optimize preload with small IVF boluses, reassessing fluid status, and avoiding/treating tachycardia.
• Definitive treatment is aortic valve replacement.