Syncope in an Older Adult with a Paced Rhythm
A 78-year-old woman is brought in after a witnessed syncope while standing to answer the door. She has no prodrome, no chest pain, and no palpitations; she recovered within 30 seconds. She has hypertension, type 2 diabetes, and a dual-chamber pacemaker implanted 4 years ago for sick sinus syndrome. Medications: metoprolol 50 mg twice daily, amlodipine 10 mg daily, metformin. Vitals supine: BP 132/78 mmHg, HR 70/min; on standing: BP 108/66 mmHg, HR 72/min (paced). Physical exam: no murmur, no carotid bruit, no focal neurologic deficit. ECG shows atrial pacing with ventricular pacing at 70/min; no acute ischemic changes. Fingerstick glucose 104 mg/dL.
1. What is your differential diagnosis and which features of the history most influence your workup?
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Differential includes: (1) neurally mediated/orthostatic syncope - note the 24/12 mmHg drop on standing and lack of prodrome; (2) arrhythmic syncope, including pacemaker malfunction (lead fracture, undersensing, loss of capture, pacemaker-mediated tachycardia) or ventricular arrhythmia; (3) structural heart disease (aortic stenosis, though no murmur; ischemia); (4) neurologic causes (less likely without focal findings); (5) medication effect (metoprolol, amlodipine).
Key history features: absence of prodrome and sudden onset without warning raise concern for arrhythmia; occurrence on standing supports orthostasis; older age and cardiac disease increase arrhythmic risk. The paced rhythm means the ECG cannot be interpreted as a native rhythm, so device interrogation is essential. Orthostatic vitals should be repeated and symptoms correlated.
2. Which tests would you order, and how do you decide between inpatient monitoring and outpatient evaluation?
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Order: 12-lead ECG (done), pacemaker interrogation (essential - check battery, lead impedance, sensing, capture, stored arrhythmias), orthostatic vitals, basic labs including electrolytes, glucose, renal function, CBC, TSH, and a transthoracic echocardiogram to assess structural disease. Consider carotid sinus massage and tilt-table testing only if the initial evaluation is unrevealing and the diagnosis remains unclear.
Disposition: this patient is high risk by age, cardiac disease, and sudden syncope without prodrome - she warrants inpatient telemetry and device interrogation rather than outpatient Holter. If interrogation shows normal device function and no arrhythmia, and orthostatic vitals reproduce symptoms, she may be managed with medication adjustment and education, but only after monitored evaluation. Escalate to EP if device malfunction or inducible arrhythmia is found.