A Case of Syncope
Hey Team,
Let's start with a case of syncope.
A 55-year-old woman with a history of obesity and hypertension presents to the ED following a syncopal episode at work. She had walked from the parking lot to her desk when she developed progressive lightheadedness, ultimately losing consciousness and awakening on the floor. She reports a similar episode the previous week at home, although without complete loss of consciousness.
She currently denies chest pain, shortness of breath, fatigue, or other associated symptoms. Her ROS is otherwise negative.
What's on your differential?
Physical Exam
Notable for a systolic crescendo-decrescendo murmur best heard at the right upper sternal border.
How does this change your differential?
Why does identifying the most likely diagnosis matter?
Aortic Stenosis: A Quick Review
Pathophysiology
The most common causes of aortic stenosis (AS) include calcific degeneration, congenital abnormalities (particularly bicuspid aortic valves), and rheumatic valvular disease.
Calcific AS develops through progressive inflammation, fibrosis, and calcification of the valve, driven in part by endothelial injury and mechanical stress.
Degenerative AS involving a tricuspid valve typically becomes clinically significant later in life, whereas patients with bicuspid valves may develop stenosis decades earlier.
Risk factors include advanced age, male sex, hypertension, hyperlipidemia, and smoking.
As the valve progressively narrows, the LV must generate higher pressures to maintain forward flow. This produces concentric LV hypertrophy, increased myocardial oxygen demand, and impaired coronary perfusion.
Over time, this can lead to the classic triad of angina, syncope, and heart failure.
Exertional syncope is thought to occur when the stenotic valve limits the ability to augment cardiac output during activity, resulting in inadequate cerebral perfusion. Arrhythmias and abnormal vasodilatory responses may also contribute.
History and Presentation
Patients can present anywhere along the spectrum from asymptomatic disease to acute decompensated heart failure and cardiogenic shock.
The classic symptoms of severe AS include:
Angina: Increased myocardial oxygen demand and impaired coronary perfusion.
Syncope: Often exertional, related to limited cardiac output augmentation.
Heart failure: Progressive LV dysfunction and elevated filling pressures.
The onset of symptoms in severe AS is a major prognostic turning point. Historically, untreated symptomatic severe AS has been associated with survival of only approximately 2–3 years, although prognosis varies by presenting symptom and severity. Symptomatic severe AS carries a 1-year mortality up to ~50% without valve replacement,
Physical examination pearl:
The classic murmur is a crescendo-decrescendo systolic ejection murmur, best heard at the right upper sternal border, often radiating to the carotids.
Importantly, murmur intensity does not reliably correlate with disease severity. In advanced, low-flow AS, the murmur may actually become softer as stroke volume decreases.
Laboratory Testing & Imaging
ECG: Obtain in all patients presenting with syncope. Findings may include LVH, conduction abnormalities, or evidence of ischemia, although a normal ECG does not exclude significant AS.
CBC/BMP: Evaluate for anemia, electrolyte abnormalities, renal dysfunction, and other contributing etiologies.
Troponin/BNP: May be elevated in advanced disease and are associated with worse outcomes, but should be ordered based on the clinical presentation.
CXR: Often nonspecific. May demonstrate cardiomegaly, pulmonary congestion, or post-stenotic dilation of the ascending aorta.
Bedside ultrasound: May identify a calcified, poorly opening aortic valve, LVH, or associated ventricular dysfunction. However, POCUS cannot reliably grade stenosis severity without Doppler assessment.
TTE is the diagnostic test of choice. It allows assessment of valve anatomy, stenosis severity, transvalvular gradients, LV function, and associated structural abnormalities.
Treatment
Some patients with AS will be critically ill on arrival, and our management may need to go well beyond simply consulting cardiology.
The central challenge is maintaining adequate coronary perfusion and forward cardiac output across a fixed outflow obstruction.
A few important management considerations:
Preload: Patients with severe AS are sensitive to changes in preload. In hypotensive patients with suspected volume depletion, cautious fluid boluses may improve cardiac output. However, aggressive fluid administration can precipitate or worsen pulmonary edema.
Afterload reduction: We have traditionally been taught to avoid nitrates and diuretics in severe AS because of concerns about reducing preload and causing hypotension. However, this is not an absolute contraindication. Selected patients with hypertensive acute heart failure may benefit from carefully titrated vasodilators, including nitroprusside or nitroglycerin, with close hemodynamic monitoring. Diuretics may also be appropriate when congestion is present.
Vasopressors: If hypotension persists, vasopressors may be necessary to maintain coronary perfusion. Phenylephrine and norepinephrine are commonly considered, depending on the clinical circumstances. The goal is to restore perfusion without excessive increases in afterload or myocardial oxygen demand.
Heart rate and rhythm: Maintaining sinus rhythm is particularly important because the hypertrophied, stiff LV depends on atrial contraction for adequate filling. Both significant tachycardia and bradycardia can compromise cardiac output. Treat unstable arrhythmias promptly.
Inotropes: In patients with severe LV systolic dysfunction and low-output shock, an inotrope such as dobutamine may be considered, although its vasodilatory and arrhythmogenic effects require careful monitoring.
Definitive treatment is aortic valve replacement, either surgical (SAVR) or transcatheter (TAVR).
For selected patients who are too unstable to undergo immediate valve replacement, balloon aortic valvuloplasty may be used as a temporizing bridge.
Disposition
Hemodynamically unstable patients: Require ICU-level care, urgent cardiology/structural heart consultation, and consideration of rescue interventions such as balloon valvuloplasty or mechanical circulatory support in selected cases.
Stable but symptomatic patients with suspected severe AS: Generally warrant admission for expedited echocardiography, monitoring, and cardiology evaluation, particularly with syncope, angina, or heart failure.
Take-Home Pearls
Evaluate for and document the presence or absence of a murmur in every patient with syncope.
Syncope in a patient with suspected severe aortic stenosis is a high-risk presentation, even when they look completely well in the ED.
The onset of symptoms can represent a major change in prognosis, and identifying severe AS changes both our acute management and disposition.
Don't let a reassuring set of vital signs or resolution of symptoms obscure a potentially dangerous structural cardiac cause of syncope.
References
Gottlieb M, Long B, Koyfman A. Evaluation and Management of Aortic Stenosis for the Emergency Clinician: An Evidence-Based Review of the Literature. J Emerg Med. 2018 Jul;55(1):34-41. doi: 10.1016/j.jemermed.2018.01.026. Epub 2018 Mar 7. [pubmed]
Miller PE, Senman BC, Gage A, Carnicelli AP, Jacobs M, Rali AS, Senussi MH, Bhatt AS, Hollenberg SM, Kini A, Menon V, Grubb KJ, Morrow DA; American College of Cardiology Critical Care Cardiology Section. Acute Decompensated Valvular Disease in the Intensive Care Unit. JACC Adv. 2024 Dec 26;3(12):101402. doi: 10.1016/j.jacadv.2024.101402. [pubmed]
Otto CM, Newby DE, Hillis GS. Calcific Aortic Stenosis: A Review. JAMA. 2024 Dec 17;332(23):2014-2026. doi: 10.1001/jama.2024.16477. [pubmed]
Shen WK, Sheldon RS, Benditt DG, Cohen MI, Forman DE, Goldberger ZD, Grubb BP, Hamdan MH, Krahn AD, Link MS, Olshansky B, Raj SR, Sandhu RK, Sorajja D, Sun BC, Yancy CW. 2017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. Circulation. 2017 Aug 1;136(5):e60-e122. doi: 10.1161/CIR.0000000000000499. Epub 2017 Mar 9. Erratum in: Circulation. 2017 Oct 17;136(16):e271-e272. doi: 10.1161/CIR.0000000000000537. [pubmed]
