If an 80-year-old patient with stroke has a normal ECG, which test is most appropriate to detect paroxysmal atrial fibrillation?

• A. Echocardiography
• B. Carotid duplex ultrasound
• C. Brain MRI
• D. Holter monitor

Answer: (D)

Detecting paroxysmal atrial fibrillation requires prolonged rhythm observation because the episodes come and go and may be missed by a single ECG. A Holter monitor records continuous ECG activity for 24 to 48 hours (and occasionally longer), increasing the likelihood of catching intermittent AF that a one-time ECG could miss. In an 80-year-old with a prior stroke and a normal baseline ECG, uncovering occult AF is crucial because it shifts management toward anticoagulation to reduce the risk of recurrent stroke.

Echocardiography assesses heart structure and function but does not reveal rhythm abnormalities. Carotid duplex looks for carotid artery disease as a stroke source, not AF. Brain MRI shows brain tissue injury patterns and stroke dating, not rhythm episodes. If the Holter study is negative but suspicion remains, longer-term rhythm monitoring (such as extended Holter monitoring or implantable loop recorders) can be considered.