Syncope

You are paged by orthopedic surgery about an elderly woman who was admitted to their service after an episode of unexplained syncope. The patient sustained an ulnar fracture during the fall, but the surgeon has decided that the fracture is nonoperative. The surgeon requests a consult about whether the patient’s syncopal episode requires inpatient workup.

In the absence of other nonsyncopal conditions requiring hospital management, which patients with syncope can be safely discharged and which require hospital observation and workup?

Many patients with vasovagal, orthostatic, or medication-related syncope have outcomes similar to those without syncope and can therefore be safely discharged home. Patients with presentations concerning for cardiogenic syncope should be considered for admission.

A prospective cohort study¹ of 7814 participants in the Framingham Heart Study and the Framingham Offspring Study compared all-cause mortality among the 822 patients who experienced a syncopal episode during the study period, and 1644 age- and sex-matched control participants without a syncopal event. Mean age at enrollment was 51 and median follow-up was 17 years. For the 822 patients with a syncopal
episode, the cause was determined by physician panel consensus and categorized as vasovagal, orthostatic, medication-related, cardiogenic, neurologic, or unknown etiology. Outcomes assessed included all-cause mortality, myocardial infarction (MI) or death from coronary disease, and fatal or nonfatal stroke.

In multivariable analysis, patients with syncope from any cause had increased all-cause mortality (HR 1.31, 95% CI 1.14-1.51; P < .001) compared to those without syncope. However, when analyzed by etiologic subgroups, poor outcomes were primarily noted in patients with cardiogenic, and to a lesser extent, neurologic syncope. Compared to no syncope, cardiogenic syncope was associated with an increased risk of mortality (HR 2.01, 95% CI 1.48-2.73; P < .001), MI or death from coronary heart disease (HR 2.66, 95% CI 1.69-4.19; P < .001), and fatal or nonfatal stroke (HR 2.01, 95% CI 1.06-3.80; P < .05). Neurologic syncope was associated with increased mortality (HR 1.54, 95% CI 1.12-2.12; P < .01) as well as fatal and nonfatal stroke (HR 2.96, 95% CI 1.69-5.98; P < .001). On the other hand, the combined category of vasovagal, orthostatic, or medication-related syncope was not significantly associated with these outcomes.

A limitation of the study is that its outcomes are long-term, whereas the decision to admit a patient may be based primarily on preventing short- to medium-term harms. Other caveats include the observational design and racially homogeneous study population. The 2018 European Society of Cardiology syncope guidelines² make class I recommendations both against hospital-based evaluation for patients with reflex-mediated syncope in the absence of dangerous medical conditions, and for observation and potential admission for those with features suggestive of cardiogenic etiologies.

What aspects of the patient-reported clinical history are most helpful for determining whether syncope is cardiogenic?

Syncope during effort, structural heart disease, and age ≥60 years can be very useful for differentiating between cardiogenic and noncardiogenic causes of syncope.

To derive a model of the most useful features of the history to predict cardiac syncope, a meta-analysis³ used a derivation sample of seven studies representing a total of 2388 North American and European patients. Studies were included if they reported ≥2 historical features and their relationship to a final diagnosis of cardiac or noncardiac syncope. The strongest predictors of cardiac syncope were syncope during effort (LR 6.92; P < .0001), supine syncope (LR 4.23; P < .0001), structural heart disease (LR 3.00; P < .0001), and age ≥60 years (LR not reported; P < .0001). A caveat to these data is that component studies used variable definitions for syncope type and historical features. ACC/AHA/HRS guidelines⁴ list exertional or supine syncope, structural heart disease, and age >60 years among the criteria predicting cardiac etiology.

You confirm that the patient is 78 years old. She tells you that she lost consciousness in a parking lot while walking from her car to the drug store. She is uncertain of the details of her medical history, and you will be unable to obtain her outpatient records over the weekend. However, she can tell you she was on her way to pick up refills of warfarin, which she takes for “irregular heartbeat,” and also furosemide, which she takes “to keep fluid out of my legs.”

Her age and syncope during effort make you concerned for a cardiac etiology, even prior to obtaining any formal workup. Most concerning is her presumed history of heart failure and atrial fibrillation, which may suggest underlying structural heart disease. You look at her ECG to see if it will further clarify her baseline cardiac pathology.

What ECG features are useful for stratifying syncope patients by mortality risk?

ECG findings shown to predict 1-year mortality in syncope patients include ventricular pacing, atrial fibrillation, left ventricular hypertrophy, and intraventricular conduction disturbances.

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