What is the best course of action for a patient with palpitations, occasional headaches, hypotension (blood pressure 90/60 mmHg), and a normal Thyroid-Stimulating Hormone (TSH) level of 1.163 ulU/ml, and should Free Triiodothyronine (FT3) and Free Thyroxine (FT4) tests be added, or propranolol (a beta-blocker) be started?

Evaluation and Management of Palpitations with Normal TSH and Hypotension

Do not start propranolol in this patient with hypotension (BP 90/60 mmHg)—beta-blockers are contraindicated in the setting of symptomatic hypotension and can precipitate cardiovascular collapse. 1, 2

Immediate Assessment Required

Confirm the blood pressure measurement with orthostatic vital signs (supine and standing) to identify postural hypotension—a drop of 20 mmHg systolic and/or 10 mmHg diastolic within 3 minutes of standing suggests orthostatic hypotension as the cause of symptoms. 1

Key Clinical Features to Evaluate

• Palpitation characteristics: Assess for rapid/irregular heartbeat, duration, frequency, and associated symptoms (dizziness, near-syncope, syncope, chest pain, dyspnea) which indicate potentially serious arrhythmias requiring urgent evaluation 3, 4
• Headache pattern: Determine if headaches are episodic with palpitations and sweating (suggesting pheochromocytoma with 90% specificity for this triad), or chronic/tension-type 1
• Volume status: Look for dehydration from diarrhea, fever, excessive diuretic use, or inadequate fluid intake 1
• Medication review: Identify non-essential hypotensive medications (calcium channel blockers, centrally acting antihypertensives, alpha-blockers) that should be discontinued 1

Thyroid Function Testing Strategy

Yes, order FT3 and FT4 in addition to TSH because a normal TSH does not exclude all thyroid dysfunction—specifically, central hypothyroidism (low FT4 with low/normal TSH) can present with palpitations and requires different management. 1

Specific Thyroid Scenarios to Consider

• Central hypothyroidism: Low FT4 with inappropriately normal/low TSH suggests pituitary/hypothalamic dysfunction; requires morning cortisol and ACTH to rule out concurrent adrenal insufficiency before thyroid hormone replacement 1
• Subclinical hyperthyroidism: Normal TSH with elevated FT3/FT4 can occur in early thyrotoxicosis and cause palpitations 1
• Recent iodine exposure: Consider seaweed consumption, iodinated contrast, topical iodine, or amiodarone which can alter thyroid function despite normal TSH 1, 5

Diagnostic Workup for Palpitations

Essential Initial Tests

• 12-lead ECG: Identify atrial fibrillation, atrial flutter, premature ventricular contractions, ventricular tachycardia, or pre-excitation syndromes 1, 3, 4
• Basic metabolic panel: Check potassium (hypokalemia causes arrhythmias), glucose (hypoglycemia causes palpitations), and creatinine 1
• Complete blood count: Rule out anemia as cause of compensatory tachycardia 3
• FT3, FT4, TSH: As discussed above 1

Ambulatory Monitoring Strategy

• If palpitations occur daily: 24-48 hour Holter monitor 4
• If palpitations are unpredictable or less than daily: Two-week continuous event recorder (more cost-effective than Holter for intermittent symptoms) 4

Differential Diagnosis Framework

Cardiac Causes (Most Important to Rule Out)

• Arrhythmias: Atrial fibrillation, atrial flutter, supraventricular tachycardia, ventricular tachycardia, premature ventricular contractions 1, 3, 4
• Structural heart disease: Mitral valve prolapse, pericarditis, heart failure 4

Endocrine Causes

• Pheochromocytoma: Screen with plasma free metanephrines (99% sensitivity, 89% specificity) if patient has episodic headaches, palpitations, and sweating 1
• Hyperthyroidism: Despite normal TSH, check FT3/FT4 as discussed 1
• Hypoglycemia: Check fasting glucose, especially if patient takes insulin or sulfonylureas 2

Autonomic Dysfunction

• Postural orthostatic tachycardia syndrome (POTS): Consider if orthostatic vital signs show heart rate increase ≥30 bpm without significant BP drop 1

Management Algorithm

Step 1: Address Hypotension First

• Discontinue or reduce non-essential hypotensive medications 1
• Increase salt intake to 5-10 grams daily and fluid intake to 3 liters daily (if no contraindications like heart failure) 1
• Avoid dehydrating factors: Alcohol, caffeine, large meals, excessive heat 1

Step 2: Rate Control Strategy (Only After BP Normalizes)

If blood pressure normalizes to >100/60 mmHg AND palpitations persist:

• First-line for most patients: Low-dose beta-blocker (bisoprolol, metoprolol, nebivolol) starting at the lowest dose and titrating gradually 1
• If beta-blocker contraindicated or not tolerated: Non-dihydropyridine calcium channel blocker (diltiazem or verapamil) 1
• Target heart rate: 60-80 bpm at rest, 90-115 bpm with moderate exercise 1

Step 3: Specific Scenarios

If hyperthyroidism is confirmed (elevated FT3/FT4):

• Beta-blockers are first-line for rate control AND reduce peripheral T4 to T3 conversion 1, 6
• Start antithyroid medication (methimazole or propylthiouracil) 1
• Critical warning: In patients with severe thyrotoxicosis and low cardiac output/heart failure, beta-blockers can cause cardiovascular collapse—use ultra-short-acting esmolol with extreme caution or avoid entirely 7, 8

If central hypothyroidism is confirmed (low FT4, low/normal TSH):

• Must check morning cortisol and ACTH first—never start thyroid hormone replacement before ruling out adrenal insufficiency, as this can precipitate adrenal crisis 1
• If cortisol is low, start hydrocortisone before levothyroxine 1

Critical Contraindications to Propranolol in This Patient

Propranolol is absolutely contraindicated with BP 90/60 mmHg because: 2

• Beta-blockade inhibits compensatory sympathetic response to hypotension
• Can precipitate severe bradycardia and further hemodynamic compromise
• Risk of cardiovascular collapse, especially if unrecognized heart failure or severe thyrotoxicosis exists 7, 8
• FDA labeling warns against use in patients with hypotension 2

Additional Propranolol Warnings

• Can mask hypoglycemia symptoms (tachycardia, tremor) 2
• Can mask hyperthyroidism signs; abrupt withdrawal may precipitate thyroid storm 2
• Contraindicated in bronchospastic disease, heart failure, and severe bradycardia 2

When to Hospitalize

Admit for inpatient evaluation if: 1, 3

• Palpitations associated with syncope, near-syncope, or severe dizziness
• Hemodynamic instability (persistent hypotension, signs of shock)
• ECG shows ventricular tachycardia, high-grade AV block, or pre-excitation with rapid ventricular response
• Suspected thyroid storm (fever, altered mental status, severe tachycardia)