What is the appropriate management for a patient with a history of transient fever, cough, followed by leg cramps, inability to walk, leg pain, and tachycardia?

Acute Myocarditis Management

This patient requires immediate hospitalization with continuous cardiac monitoring and urgent cardiology consultation for suspected acute myocarditis presenting with ventricular arrhythmia (tachycardia at 140s) and neuromuscular complications.

Immediate Diagnostic Workup

The clinical presentation of transient fever followed by leg weakness/pain and persistent tachycardia strongly suggests acute myocarditis with potential arrhythmic complications. Essential first-line testing must include 1:

• 12-lead ECG to assess for conduction abnormalities, low-voltage QRS complexes, ST-T wave changes, or AV blocks 1, 2
• Cardiac biomarkers including troponins, which are typically significantly elevated in acute myocarditis 1, 2
• Inflammatory markers including erythrocyte sedimentation rate and C-reactive protein 1
• Transthoracic echocardiogram to evaluate ventricular function and wall motion abnormalities 1
• Chest radiograph to exclude pneumonia or pulmonary complications 1, 3

The leg cramps and inability to walk may represent either myositis (muscular inflammation accompanying myocarditis) or profound deconditioning from the acute illness 1, 4.

Acute Management Protocol

Hemodynamic Stabilization

Given the tachycardia at 140 bpm, immediate assessment of hemodynamic stability is critical 5, 6:

• If hemodynamically unstable (hypotension, shock, altered mental status): Immediate synchronized cardioversion is indicated without delay for diagnostic workup 5, 6
• If hemodynamically stable: Proceed with rhythm analysis and medical management 5

Hospital Admission Requirements

Mandatory admission to monitored bed for any patient with ventricular arrhythmias or heart block in the setting of suspected acute myocarditis 1. The patient requires:

• Continuous telemetry monitoring for detection of life-threatening arrhythmias 1
• Serial ECGs to monitor for progressive conduction abnormalities (widening QRS, AV blocks) 1
• Serial cardiac biomarkers to assess for ongoing myocardial injury 1

Arrhythmia Management

Patients with acute myocarditis have extremely high risk of sustained ventricular tachyarrhythmias, with odds ratio of 5.4 for cardiac arrest compared to those without arrhythmias 1. Management approach:

• Temporary pacemaker insertion is recommended if symptomatic heart block develops or if ventricular tachyarrhythmias are triggered by high-degree AV block 1
• Avoid prophylactic antiarrhythmic drugs unless sustained arrhythmias occur 1
• Progressive wall motion abnormalities, persistent troponin elevation, widening QRS, and frequent non-sustained ventricular arrhythmias may precede life-threatening sustained arrhythmias 1

Supportive Medical Therapy

Neurohormonal Blockade

For patients with suspected acute myocarditis and possible ventricular dysfunction 1:

• ACE inhibitors for neurohormonal blockade
• Beta-blockers for rate control and neurohormonal blockade
• Recommendation to avoid exercise during acute phase

Critical Pitfall to Avoid

Do not discharge this patient or manage as outpatient. The combination of recent febrile illness, persistent tachycardia, and neuromuscular symptoms (leg weakness/pain) represents a high-risk presentation requiring inpatient monitoring 1, 2. Fulminant myocarditis has only 58% short-term survival rate, and sustained arrhythmias dramatically increase mortality risk 1.

Device Considerations

Defer ICD implantation decisions until the acute phase resolves 1. Device selection should reflect:

• Presence and extent of left ventricular dysfunction
• Prognosis for progression versus regression of dysfunction
• Consider earlier device implantation if giant cell myocarditis or cardiac sarcoidosis is diagnosed 1

Follow-up Monitoring

If persistent AV blocks develop after the acute phase, permanent pacing is recommended 1. The patient requires:

• Serial echocardiography to assess for evolution to inflammatory cardiomyopathy
• Long-term follow-up for risk of sudden cardiac death similar to dilated cardiomyopathy 1
• Gradual return to activity only after complete resolution of acute inflammation and normalization of cardiac function 1