A 78-YEAR-OLD MAN WITH KNOWN HYPERTENSION AND DIABETES PRESENTS WITH A HISTORY OF FIVE ATTACKS OF PALPITATIONS OCCURRING OVER THE PAST 6 MONTHS; THE PALPITATIONS OCCUR RANDOMLY, START SUDDENLY AND LAST 2–10 HOURS. DURING THE ATTACK HE FEELS FAST, IRREGULAR PALPITATIONS BUT NO OTHER SYMPTOMS. THE ATTACKS TERMINATE SUDDENLY. WHICH OF THE FOLLOWING STATEMENTS IS TRUE

• A. The likely diagnosis is atrial fibrillation ✓
• B. Supraventricular tachycardia is the most likely diagnosis.
• C. A 24-hour ECG will establish the diagnosis
• D. A cardiac ultrasound is unnecessary
• E. You can reassure the patient that he will not need warfarin

The likely diagnosis in this case is Atrial Fibrillation (AF). Atrial fibrillation is a common type of irregular heartbeat (arrhythmia) that can lead to serious complications if left untreated. In this scenario, the patient’s history of sudden-onset palpitations that are fast and irregular, lasting for a few hours, is characteristic of atrial fibrillation.

Reasoning:

1. Symptoms: The patient’s presentation with sudden-onset palpitations that are fast and irregular without any other associated symptoms is typical of atrial fibrillation. Atrial fibrillation often presents with palpitations as the primary symptom.
2. Duration of Episodes: The duration of the palpitation episodes lasting 2-10 hours is consistent with paroxysmal atrial fibrillation, where the irregular heart rhythm starts suddenly and stops spontaneously.
3. Age and Comorbidities: The patient’s age of 78 years and known history of hypertension and diabetes are common risk factors for atrial fibrillation. These comorbidities increase the likelihood of AF as the underlying cause of palpitations.
4. Termination of Episodes: The sudden termination of the palpitation episodes is also a characteristic feature of atrial fibrillation, where the heart rhythm can return to normal spontaneously.
5. Diagnosis: While a 24-hour ECG (Holter monitor) can be useful in capturing intermittent arrhythmias like atrial fibrillation, in this case, given the patient’s history and presentation, the clinical suspicion for AF is high based on symptoms alone.
6. Treatment Considerations: Atrial fibrillation increases the risk of stroke due to blood clots forming in the heart’s chambers. Therefore, anticoagulation therapy with medications like warfarin or newer oral anticoagulants may be necessary to reduce this risk, especially in older patients with additional risk factors like hypertension and diabetes.

In conclusion, based on the patient’s age, symptoms, duration of episodes, comorbidities, and clinical presentation, atrial fibrillation is the most likely diagnosis in this case.