Summary

The 2017 ACC/AHA/HRS syncope guideline provides comprehensive recommendations for the evaluation and management of adult and pediatric patients with syncope, defined as abrupt transient loss of consciousness from cerebral hypoperfusion with rapid spontaneous recovery. Initial evaluation centers on detailed history, physical exam, and 12-lead ECG, with risk stratification directing disposition. The guideline addresses cardiac (arrhythmic, structural, inheritable channelopathies), reflex (vasovagal, carotid sinus, situational), and orthostatic causes, and gives population-specific guidance for pediatric, geriatric, athletic, ACHD patients, and drivers.

Key Recommendations

Obtain detailed history, physical examination, and resting 12-lead ECG in all patients presenting with syncope.
Use clinical judgment supplemented by risk-stratification tools to decide ED disposition; admit patients with serious medical conditions (e.g., sustained/symptomatic VT, Mobitz II or third-degree AV block, severe aortic stenosis, PE, acute HF, MI) and discharge low-risk reflex syncope patients.
Do not perform routine, indiscriminate laboratory testing; targeted blood tests (e.g., troponin, BNP, hemoglobin) only when clinically indicated.
Obtain transthoracic echocardiogram only when structural heart disease is suspected; avoid routine echocardiography in patients with normal exam and ECG.
Avoid routine neuroimaging (CT, MRI, carotid ultrasound) and EEG in patients without focal neurological findings — low yield, high cost.
Select cardiac rhythm monitoring duration to match symptom frequency: Holter for daily symptoms, external loop/patch for weeks, implantable cardiac monitor for infrequent recurrent unexplained syncope.
First-line treatment of vasovagal syncope is patient education, reassurance, salt/fluid liberalization, and physical counterpressure maneuvers; midodrine, fludrocortisone, or beta-blockers (in patients ≥42 y) are reasonable if recurrent despite conservative measures.
Reserve dual-chamber permanent pacing for VVS only in selected patients ≥40 years with recurrent syncope and documented spontaneous prolonged asystolic pauses.
Treat neurogenic orthostatic hypotension with non-pharmacologic measures (water bolus, counter-maneuvers, compression garments), then midodrine, droxidopa, fludrocortisone, or pyridostigmine; reduce offending medications.
In syncope with ischemic/nonischemic cardiomyopathy and LVEF ≤35%, ICD is indicated per HF guidelines; EPS is no longer required before ICD in this population.
In Brugada, LQTS, CPVT, ARVC patients with syncope of suspected arrhythmic origin, ICD implantation is reasonable; beta-blockers are first-line for LQTS, and beta-blockers ± flecainide plus exercise restriction for CPVT.
Pediatric VVS: first-line therapy is increased salt and fluid intake plus physical counter-maneuvers; routine echocardiography is not indicated when history, exam, and ECG are normal.
Apply condition-specific symptom-free waiting periods before resuming private driving (e.g., 1 month for unexplained syncope or OH; 3 months for ICD after arrhythmic syncope; 1 week after pacemaker for bradycardia).

Thresholds & Doses

Orthostatic hypotension: drop in SBP ≥20 mm Hg or DBP ≥10 mm Hg on standing (≥30 mm Hg SBP in supine hypertension).
Classic OH: sustained SBP fall ≥20 / DBP ≥10 mm Hg within 3 minutes of standing; delayed OH: same fall developing >3 minutes after standing; initial OH: transient fall within 15 seconds.
Postural tachycardia syndrome (POTS): HR increase ≥30 bpm (≥40 bpm if 12–19 y) within 10 min of standing without OH; standing HR often >120 bpm.
Carotid sinus hypersensitivity: pause ≥3 seconds and/or SBP drop ≥50 mm Hg during carotid sinus massage (5 seconds each side, supine and upright).
Brugada type 1 ECG: ST elevation ≥2 mm with type 1 morphology in ≥1 right precordial lead (V1–V2).
Long-QT syndrome diagnostic thresholds: QTc ≥500 ms, or QTc 480–499 ms with syncope, or LQTS risk score ≥3.5.
Short-QT syndrome: QTc ≤340 ms.
ICD indication threshold for primary prevention in ischemic/nonischemic cardiomyopathy: LVEF ≤35%.
Older adult definition for this guideline: age >75 years.
Driving — VVS with 1–6 episodes/year: 1-month symptom-free interval; >6 episodes/year: not fit to drive until resolved.
Driving — syncope with LVEF <35% and presumed arrhythmic etiology with ICD: 3-month symptom-free interval.
Driving — syncope after pacemaker for bradycardia or carotid sinus syncope: 1 week.
US ED syncope burden: ~6.7 million ED episodes; ~0.77% of all ED visits; 58% admission rate in patients >80 years.
US annual hospital cost of syncope: ~$4.1 billion (2014 dollars), mean $9,400/admission.

Citations

Section 2.1, Table 3 — definitions of syncope, OH, POTS, VVS, carotid sinus syndrome.
Section 2.3 and Figure 1 — initial evaluation: history, physical exam, ECG.
Section 2.3.3, Tables 5–6 — short- and long-term risk factors and risk scores (OESIL, SFSR, Boston, ROSE, STePS).
Section 2.3.4, Table 7 and Figure 2 — disposition and serious medical conditions warranting admission.
Section 3.2.3, Table 8 — cardiac rhythm monitor selection by symptom frequency.
Section 4.3 (4.3.1–4.3.5) — inheritable arrhythmic conditions: Brugada, short-QT, LQTS, CPVT, early repolarization.
Section 5.1 and Figure 4 — vasovagal syncope management algorithm.
Section 6.1 and Figure 5 — neurogenic orthostatic hypotension management.
Section 10.4, Table 10 — driving restrictions and symptom-free waiting times.
Section 11.2 — healthcare costs of syncope (US Healthcare Utilization Project).