What is trigeminy?

Trigeminy: Definition and Clinical Significance

Trigeminy is a cardiac arrhythmia pattern characterized by every third heartbeat being a premature ventricular contraction (PVC), creating a repetitive sequence of two normal beats followed by one premature beat. 1

Characteristics of Trigeminy

• Pattern: Two normal sinus beats followed by one premature ventricular contraction
• Electrocardiogram: Shows a regular pattern of two normal QRS complexes followed by one abnormal, wide QRS complex (the PVC)
• Clinical presentation: Patients may present with:
  • Effective bradycardia
  • Apical-radial pulse deficit (pulse feels slower than actual heart rate)
  • Relative hypertension with wide pulse pressure 1

Clinical Significance

Trigeminy can have several important clinical implications:

• Heart rate estimation: Can result in inaccurate estimation of heart rate, as PVCs may not generate effective cardiac output 1
• Hemodynamic effects: May cause symptoms due to reduced cardiac output when frequent PVCs occur
• Diagnostic challenges: May be misinterpreted by automated monitoring systems, including implantable cardioverter-defibrillators (ICDs) 2
• Underlying conditions: Often indicates the need to search for underlying heart disease 1

Associated Conditions

Trigeminy may be associated with:

1. Structural heart disease:

   • Ischemic heart disease
   • Cardiomyopathies (hypertrophic, dilated, arrhythmogenic right ventricular)
   • Valvular heart disease 1

2. Heart failure: Patients with trigeminy should be evaluated for signs of heart failure

3. Medication effects: Various medications can induce or exacerbate ventricular arrhythmias 1

Evaluation

When trigeminy is detected, evaluation should include:

1. 12-lead ECG: Should be obtained in sinus rhythm to look for evidence of heart disease 1

2. Physical examination: Focus on finding evidence of structural heart disease:

   • Jugular venous distention
   • Rales, gallops
   • Cardiac murmurs
   • Peripheral edema 1

3. Exercise testing: Useful in patients with symptoms associated with exertion or suspected ischemic heart disease 1

Management Considerations

Management depends on:

• Presence of symptoms
• Underlying cardiac conditions
• Frequency and complexity of arrhythmia

In asymptomatic patients without structural heart disease, treatment may not be necessary. In symptomatic patients or those with underlying heart disease, treatment of the underlying condition is paramount.

Potential Complications

• Misdiagnosis by automated monitoring systems (as seen in a case where an ICD incorrectly diagnosed ventricular trigeminy as ventricular fibrillation, leading to inappropriate shock) 2
• Hemodynamic compromise in patients with pre-existing cardiac dysfunction
• Progression to more complex arrhythmias in some cases

Key Takeaways

• Trigeminy is a specific pattern of cardiac arrhythmia with every third beat being a PVC
• It can cause effective bradycardia and pulse deficits
• The presence of trigeminy should prompt evaluation for underlying heart disease
• Management focuses on treating underlying conditions and addressing symptoms if present