Is an Implantable Cardioverter-Defibrillator (ICD) indicated for a patient with dilated cardiomyopathy and a left ventricular ejection fraction (EF) of 35-40%?

ICD Implantation for Dilated Cardiomyopathy with EF 35-40%

ICD therapy is generally not indicated for primary prevention in patients with dilated cardiomyopathy and an ejection fraction between 35-40% according to current guidelines, unless there are additional high-risk features present. 1

Decision Algorithm for ICD Implantation in DCM with EF 35-40%

Primary Prevention Criteria

• EF threshold: Current guidelines from ACC/AHA recommend ICD for primary prevention when:
  • LVEF ≤35% for nonischemic dilated cardiomyopathy 1
  • LVEF ≤30% for ischemic cardiomyopathy with NYHA class I symptoms 1
  • Patient has completed at least 3 months of optimal guideline-directed medical therapy 2

Special Considerations for EF 35-40%

• ICD may be considered in this "borderline" EF range if:
  1. Genetic arrhythmogenic cardiomyopathy with high-risk features (ICD reasonable when EF ≤45%) 1
  2. Inducible sustained ventricular tachycardia on electrophysiology study 1
  3. History of sustained VT/VF (secondary prevention) 1

Important Clinical Factors to Consider

Medical Therapy Optimization

• Ensure patient has received at least 3 months of optimal guideline-directed medical therapy before making final decision 2
• Quadruple therapy (ACE inhibitors/ARBs, beta-blockers, mineralocorticoid receptor antagonists, and SGLT2 inhibitors) should be optimized 3
• Reassess LVEF after medical therapy optimization, as improvement may occur 4, 5

Risk Assessment Beyond EF

• NYHA functional class (higher class = higher risk)
• QRS duration and morphology (LBBB with QRS ≥150 ms may benefit from CRT-D instead) 1
• Presence of nonsustained ventricular tachycardia
• Patient's age and comorbidities
• Expected survival with good functional status >1 year 1

Important Caveats and Pitfalls

1. EF measurement variability: Do not rely on a single EF measurement; confirm with repeat imaging 2

2. Potential for EF improvement: A significant number of DCM patients show marked improvement in left ventricular function during follow-up, potentially averting the need for ICD therapy 4, 5

3. Complications: ICD therapy is associated with a considerable complication rate, including inappropriate shocks and lead-related problems during long-term follow-up 4

4. Borderline cases: For patients with EF 35-40%, electrophysiology-guided risk stratification may identify those who would benefit from ICD despite having relatively preserved EF 6

5. Limited evidence: The evidence supporting ICD use in the 35-40% EF range is limited, with some studies showing benefit while others do not 3

Conclusion for Clinical Practice

For a patient with dilated cardiomyopathy and EF 35-40%, the standard approach is to:

1. Optimize medical therapy for at least 3 months
2. Reassess EF after optimization
3. If EF remains >35%, ICD is generally not indicated unless additional high-risk features are present
4. Consider electrophysiology consultation for risk stratification in borderline cases

This approach aligns with current guidelines while acknowledging the limitations of using EF as the sole criterion for sudden cardiac death risk.