What is the survival rate of a patient with shark fin sign on ECG (electrocardiogram) indicative of severe hyperkalemia?

Survival Rate of Patients with Shark Fin Sign on ECG Due to Severe Hyperkalemia

The survival rate for patients with a shark fin sign on ECG due to severe hyperkalemia is extremely poor, with hyperkalemia being directly responsible for sudden cardiac arrest and a mortality rate of approximately 30.7% if not treated immediately.

Understanding the Shark Fin ECG Pattern in Hyperkalemia

The shark fin pattern (also known as sine-wave pattern) represents the most severe ECG manifestation of hyperkalemia, occurring when:

• Serum potassium exceeds 6.5 mmol/L (severe hyperkalemia)
• QRS complexes widen significantly
• P waves disappear
• S and T waves merge, creating a triangular or "shark fin" appearance

This pattern represents the final ECG stage before deterioration to ventricular fibrillation or asystole, making it a true medical emergency 1.

Mortality Risk and Prognostic Factors

Several factors influence the mortality risk in patients with shark fin ECG due to hyperkalemia:

1. Overall mortality rate: Approximately 30.7% in-hospital mortality for severe hyperkalemia requiring hospitalization 2

2. Factors associated with higher mortality:

   • Presence of cardiac arrest at time of diagnosis (20.3% of severe hyperkalemia cases present with cardiac arrest)
   • Multi-organ failure (24.5% of cases)
   • Emergent admission (68.6% of cases)
   • Need for ICU treatment
   • Malignancy, infection, or bleeding as underlying conditions
   • Acute kidney injury in patients with previously normal renal function 2

3. Timing of intervention: Without immediate treatment, progression to ventricular fibrillation or asystole is likely, which significantly reduces survival chances 1, 3

Clinical Presentation and Diagnosis

The shark fin ECG pattern represents end-stage hyperkalemia with:

• Sine-wave appearance (fusion of QRS, ST, and T waves)
• Absent P waves
• Extremely widened QRS complexes
• Potential for misdiagnosis as wide complex tachycardia 4

Other ECG changes that may precede the shark fin pattern include:

• Peaked T waves (tenting)
• Flattened or absent P waves
• Prolonged PR interval
• Widened QRS complex
• Deepened S waves 1

Emergency Management Protocol

Immediate intervention is critical for survival. Treatment should follow this sequence:

1. Cardiac membrane stabilization (within minutes):

   • Calcium chloride (10%): 5-10 mL (500-1000 mg) IV over 2-5 minutes, OR
   • Calcium gluconate (10%): 15-30 mL IV over 2-5 minutes 1, 5

2. Shift potassium into cells (within 15-30 minutes):

   • Insulin with glucose: 10 units regular insulin IV with 25g glucose (50 mL of D50) over 15-30 minutes
   • Sodium bicarbonate: 50 mEq IV over 5 minutes (especially if metabolic acidosis present)
   • Nebulized albuterol: 10-20 mg over 15 minutes 1, 5

3. Promote potassium excretion:

   • Diuresis: furosemide 40-80 mg IV
   • Potassium binders (patiromer or sodium zirconium cyclosilicate preferred over older resins)
   • Hemodialysis (especially for refractory cases or severe renal dysfunction) 1, 5

Important Considerations

• ECG response to calcium: While calcium is standard treatment, research shows it may be more effective for rhythm disorders than non-rhythm ECG changes of hyperkalemia 6

• Underlying conditions: Chronic kidney disease is the most common underlying condition, with metabolic acidosis being the most common precipitating factor 2

• Medication review: ACE inhibitors, ARBs, potassium-sparing diuretics, NSAIDs, beta-blockers, and certain other medications can contribute to hyperkalemia 5

• Monitoring: Close cardiac monitoring is essential during treatment, with repeat ECG and potassium measurements to assess response 5

Prevention of Recurrence

For patients who survive the initial event:

• Regular monitoring of serum potassium (within 1 week of medication changes and regularly thereafter)
• Consider potassium binders for chronic management in high-risk patients
• Careful medication review and adjustment
• Dietary potassium restriction as needed 1, 5

The shark fin ECG pattern represents an ominous sign with high mortality risk. Immediate recognition and aggressive treatment following the protocol above offer the best chance for survival.