How to manage a 59-year-old male with constipation, abdominal pain, atrial fibrillation (Afib), hypokalemia (low potassium), and hyperthyroidism (low thyroid-stimulating hormone (TSH))?

Management of 59-Year-Old Male with Constipation, Abdominal Pain, Atrial Fibrillation, Hypokalemia, and Hyperthyroidism

SUBJECTIVE

Chief Complaint: 3 days of gassy abdomen with pain radiating throughout abdomen, most prominent in right mid-to-lower quadrant 1

History of Present Illness:

• 3 days of progressive abdominal distension and pain 1
• Constipation for 3 days (no bowel movement) 1
• No fever, no vomiting 1
• Known hypertensive on Losartan and Amlodipine 1

Pertinent Positives:

• Newly detected atrial fibrillation on ECG 1
• Suppressed TSH (<0.1) indicating hyperthyroidism 1
• Hypokalemia (K 3.45) 1
• Mild hyponatremia (Na 131.9) 1

Pertinent Negatives:

• No hemodynamic instability 1
• No fever (rules out acute infection) 1
• Normal WBC count (8.59) 1

OBJECTIVE

Vital Signs: Not fully documented but patient appears stable (no mention of hypotension or tachycardia requiring urgent intervention) 1

Physical Examination Findings to Document:

• Irregular pulse consistent with atrial fibrillation 1
• Abdominal distension with diffuse tenderness, most prominent right mid-to-lower quadrant 1
• Bowel sounds (hypoactive expected with ileus) 1
• Signs of thyrotoxicosis: tremor, warm moist skin, lid lag, thyromegaly 1

Laboratory Results:

• Electrolytes: Na 131.9 (low), K 3.45 (low), Cl 96.8 1
• Thyroid: TSH <0.1 (suppressed, indicating hyperthyroidism) 1
• CBC: WBC 8.59, Hgb 14.4, Hct 0.44, Plt 173 (all normal) 1
• Differential: Neutrophils 0.58 (normal), Lymphocytes 0.18 (low), Monocytes high, Eosinophils 0.09 1

ECG: Atrial fibrillation with controlled ventricular response 1

Abdominal X-ray:

• Non-obstructive bowel gas pattern 1
• Findings consistent with constipation/fecal loading or ileus 1
• No mechanical obstruction, no perforation 1

Additional Testing Required:

• Free T4 and Free T3 to confirm hyperthyroidism 1
• Transthoracic echocardiogram to assess cardiac structure and function 1
• Renal function (creatinine) 1
• Hepatic function tests 1

ASSESSMENT

Primary Diagnoses:

1. Functional Ileus/Severe Constipation 1

• Likely multifactorial: hypokalemia, possible thyrotoxicosis effect on GI motility 1
• Non-obstructive pattern on imaging rules out mechanical obstruction 1

2. Newly Detected Atrial Fibrillation Secondary to Hyperthyroidism 1

• Hyperthyroidism causes AF in 10-25% of patients, more commonly in men and elderly 1
• This patient fits the high-risk profile (59-year-old male with suppressed TSH) 1, 2
• AF in hyperthyroidism occurs due to shortened atrial refractory period and increased supraventricular ectopic activity 3, 4

3. Hyperthyroidism (Thyrotoxicosis) 1

• TSH <0.1 is diagnostic of hyperthyroid state 1
• Requires confirmation with elevated Free T4/T3 1
• Treatment of AF in hyperthyroidism is primarily directed toward restoring euthyroid state, which usually results in spontaneous reversion to sinus rhythm 1

4. Hypokalemia 1

• K 3.45 (low-normal to mild hypokalemia) 1
• Contributing to ileus and potentially to cardiac arrhythmia 1
• May be exacerbated by hyperthyroidism 1

5. Mild Hyponatremia 1

• Na 131.9 (mild) 1
• Likely dilutional or related to underlying conditions 1

Stroke Risk Assessment:

This patient requires anticoagulation 1

• Oral anticoagulation (INR 2.0-3.0) is recommended for AF associated with thyrotoxicosis to prevent thromboembolism 1
• Risk factors present: age >59, hypertension, male sex 1, 5
• Paroxysmal AF carries the same stroke risk as permanent AF 1, 5

PLAN

Immediate Management (First 24-48 Hours):

1. Atrial Fibrillation Rate Control 1

Administer beta-blocker as first-line therapy for rate control in AF complicating thyrotoxicosis 1:

• Metoprolol 25-50 mg PO every 6-8 hours OR Atenolol 25-50 mg PO daily 1
• Beta-blockers are Class I recommendation (Level of Evidence B) for hyperthyroid AF 1
• Aggressive beta-blocker dosing may be required in thyrotoxicosis; high doses are particularly important 1
• Target heart rate: <110 bpm at rest 1

Alternative if beta-blocker contraindicated 1:

• Diltiazem 30-60 mg PO every 6-8 hours OR Verapamil 80-120 mg PO every 8 hours 1
• These are Class I recommendations when beta-blockers cannot be used 1

Avoid digoxin as monotherapy 1:

• Digoxin is only effective for rate control at rest and should only be used as second-line agent 1
• Less effective in hyperthyroid states 1

2. Anticoagulation for Stroke Prevention 1, 5

Initiate oral anticoagulation immediately 1:

• Warfarin with target INR 2.0-3.0 (Class I recommendation, Level of Evidence C) 1
• Alternative: Direct oral anticoagulant (DOAC) if no contraindications 5
• Do NOT defer anticoagulation until after cardioversion or achievement of euthyroid state 1
• Anticoagulation is the only therapy proven to reduce AF-related deaths 5

Critical Pitfall to Avoid:

• Never discontinue anticoagulation even if sinus rhythm is restored, as stroke risk persists with risk factors present 5
• Once euthyroid state is restored, continue anticoagulation based on stroke risk factors (this patient has hypertension and age >59) 1

3. Hyperthyroidism Management 1, 6

Initiate antithyroid therapy immediately 1, 6:

• Methimazole 15-30 mg PO daily (preferred) OR Propylthiouracil 100-150 mg PO three times daily 1, 6
• Treatment is primarily directed toward restoring euthyroid state, which usually results in spontaneous reversion to sinus rhythm 1
• More than 56% of AF spontaneously reverts to sinus rhythm when thyroid hormone levels decline 6

Defer cardioversion 1, 6:

• Antiarrhythmic drugs and electrical cardioversion are generally unsuccessful while thyrotoxic condition persists 1
• Attempted cardioversion should be deferred until approximately the 4th month of maintaining euthyroid state 6

Additional thyroid workup:

• Free T4, Free T3 to confirm hyperthyroidism 1
• Thyroid ultrasound if etiology unclear 1
• Consider endocrinology consultation 1

4. Constipation/Ileus Management 1

Correct electrolyte abnormalities first 1:

• Potassium replacement: KCl 40-80 mEq PO divided doses to achieve K >4.0 1
• Monitor potassium closely (recheck in 4-6 hours after supplementation) 1
• Correct hyponatremia cautiously with isotonic fluids 1

Bowel regimen 1:

• NPO initially if concern for ileus 1
• Nasogastric tube decompression if significant distension or nausea develops 1
• Once electrolytes corrected and patient stable:
  • Polyethylene glycol 17 g PO daily 1
  • Docusate sodium 100 mg PO twice daily 1
  • Consider bisacodyl 10 mg PO/PR if no response 1
• Avoid stimulant laxatives until mechanical obstruction definitively ruled out 1

Serial abdominal exams 1:

• Monitor for peritoneal signs every 4-6 hours 1
• Repeat abdominal X-ray in 24 hours if no improvement 1

5. Hypertension Management 1

Continue home antihypertensives 1:

• Losartan and Amlodipine can be continued 1
• Beta-blocker for AF will also help with blood pressure control 1
• Monitor blood pressure closely as beta-blocker may cause additive effect 1

Short-Term Management (48 Hours to 2 Weeks):

1. Monitor Response to Therapy 1, 6

Daily assessments 1:

• Heart rate and rhythm (continuous telemetry initially) 1
• Thyroid function (repeat TSH, Free T4 in 2 weeks) 1
• Electrolytes (daily until stable) 1
• INR (if on warfarin, check every 2-3 days until therapeutic) 1
• Bowel function (daily bowel movements, abdominal exam) 1

2. Echocardiography 1

Obtain transthoracic echocardiogram within 48-72 hours 1:

• Assess for valvular disease 1
• Left atrial size 1
• Left ventricular size and function 1
• Right ventricular pressure (pulmonary hypertension) 1
• Left ventricular hypertrophy 1
• Rule out structural heart disease 1

3. Adjust Medications Based on Response 1

Beta-blocker titration 1:

• Increase dose if heart rate remains >110 bpm at rest 1
• High doses may be required in thyrotoxicosis 1
• Monitor for bradycardia once euthyroid state approached 1

Antithyroid medication adjustment 1, 6:

• Follow thyroid function every 2-4 weeks 1
• Adjust dose to achieve euthyroid state 1

Long-Term Management (Beyond 2 Weeks):

1. Rhythm Assessment After Euthyroid State Achieved 1, 6

Reassess rhythm at 4 months of euthyroid state 1, 6:

• If AF persists after 4 months of euthyroid state, consider elective cardioversion 6
• Cardioversion is highly effective once euthyroid (56.7% maintain sinus rhythm at 10 years) 6
• Continue anticoagulation for 4 weeks before and after cardioversion 1

If spontaneous conversion to sinus rhythm occurs 1, 6:

• Continue anticoagulation based on stroke risk factors (this patient should continue due to hypertension and age) 1, 5
• Do not discontinue anticoagulation just because sinus rhythm is restored 5
• Continue beta-blocker at reduced dose 1

2. Rhythm Maintenance Therapy 1

Most patients should NOT be placed on rhythm maintenance therapy 1:

• Risks outweigh benefits in most patients 1
• Only consider in selected patients whose quality of life is significantly compromised 1
• If needed: amiodarone, disopyramide, propafenone, or sotalol 1

3. Definitive Thyroid Management 1

Endocrinology follow-up for definitive therapy 1:

• Radioactive iodine ablation 1
• Continued antithyroid medication 1
• Thyroidectomy if indicated 1

4. Ongoing Monitoring 1, 5

Regular follow-up every 3-6 months 1:

• ECG to document rhythm 1
• Thyroid function tests 1
• INR monitoring (if on warfarin) 1
• Echocardiogram annually if AF persists 1
• Assess for progression of AF (paroxysmal to persistent to permanent) 1, 5

5. Risk Factor Modification 5

Address cardiovascular comorbidities 5:

• Optimize blood pressure control (target <130/80) 5
• Screen for diabetes 1, 5
• Screen for sleep apnea if symptoms present 5
• Lifestyle modifications: weight loss, alcohol reduction, exercise 5

Critical Pitfalls to Avoid:

1. Never use digoxin, diltiazem, or verapamil if WPW syndrome suspected (wide QRS or delta waves on ECG) 1
2. Never attempt cardioversion while patient remains thyrotoxic - it will fail 1, 6
3. Never discontinue anticoagulation after cardioversion in patients with stroke risk factors 5
4. Never assume AF will resolve - only 56% spontaneously convert even after achieving euthyroid state 6
5. Never use digoxin as monotherapy for rate control - it only works at rest 1
6. Never delay anticoagulation - stroke risk is immediate and independent of rhythm 1, 5
7. Never overlook hypokalemia - correct before aggressive bowel regimen to prevent worsening ileus 1

Disposition:

Admit to telemetry unit for rate control optimization, anticoagulation initiation, electrolyte repletion, and monitoring of ileus 1