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PubMed This is a summary of 18 peer-reviewed journal articles Updated
Cardiology

Heart Rhythms and the Role of an ICD

At a Glance

In LVNC, a spongy-looking heart does not by itself mean an ICD is needed. Doctors weigh prior dangerous rhythms, ejection fraction after optimized medication, MRI scar, rhythm-monitor findings, fainting, family history, symptoms, and the risks of implantation.

While the “spongy” appearance of Left Ventricular Noncompaction (LVNC) is its most famous feature, the way the heart beats is often more important than how it looks. For some people with LVNC, underlying genetic factors, scarring, or ventricular remodeling can create an unstable environment in the heart’s electrical system [1][2]. This can lead to dangerous heart rhythms like Ventricular Tachycardia (VT) or Ventricular Fibrillation (VF), which can cause the heart to stop pumping effectively—a condition known as sudden cardiac arrest [3][4].

To protect against these events, doctors may recommend an Implantable Cardioverter-Defibrillator (ICD). An ICD is a small, battery-powered device placed under the skin that monitors your heart rhythm 24/7 and can deliver a life-saving electrical shock if it detects a dangerous rhythm [5].

Who Needs an ICD?

Deciding who needs an ICD is a careful, individualized process. It is generally based on two categories of prevention:

  • Secondary Prevention: This is for people who have already survived a life-threatening heart rhythm event or a cardiac arrest [4]. In these cases, an ICD is strongly considered because the risk of a second event is high, though decisions always factor in overall health, reversible causes, and patient goals [6].
  • Primary Prevention: This is for people who have never had a dangerous rhythm but are considered at “high risk” for one in the future [5].

The Standard Criteria: Function Over Form

One of the most critical facts for patients to understand is that the amount of “sponginess” or trabeculation in your heart is not an automatic reason to get an ICD [7][1]. A heart can look very spongy but still be electrically stable [8].

Instead, doctors follow standard guidelines used for many types of heart failure. A primary prevention ICD is generally considered when:

  1. Low Ejection Fraction: Your Ejection Fraction (EF) is 35% or lower [5][9].
  2. Optimized Medication: You have been taking tolerated, Guideline-Directed Medical Therapy (the “four pillars” of heart failure medication) for at least three to six months, and your EF remains low [9][10]. Sometimes, these medications improve the heart’s function enough that an ICD is no longer necessary [11].
  3. Symptoms & Survival: You have relevant symptoms (like shortness of breath during daily activities, known as NYHA Class II or III) and an expected meaningful survival of more than one year [5][12].

Risk Modifiers: Looking Beyond the Pumping Function

While the standard guidelines heavily rely on Ejection Fraction, specialists (like Electrophysiologists) look for “risk modifiers” to refine their recommendation, especially if your EF is above 35% [13]:

  • Late Gadolinium Enhancement (LGE): LGE on an MRI represents scarring in the heart muscle [7]. Patients with significant scarring are at a higher risk for arrhythmias [14][15].
  • Non-Sustained Ventricular Tachycardia (NSVT): These are short “bursts” of fast heartbeats that stop on their own. They can be a warning sign that the heart’s electrical system is unstable [3][16].
  • Unexplained Fainting (Syncope): Fainting without a clear cause can sometimes be a sign that the heart briefly went into a dangerous rhythm [13].
  • Family History: A history of sudden cardiac death in close family members is a significant red flag [13].

Note: These risk modifiers are discussion points that help guide shared decision-making; they do not automatically mandate an ICD on their own.

Living with an ICD: Risks and Trade-offs

An ICD is a powerful safety net, but it comes with meaningful trade-offs. Complication rates vary by population, device type, and follow-up duration, but some studies show around 10% of patients experience issues [17]. These can include:

  • Lead Issues: The wires (leads) connecting the device to the heart can sometimes move or break, requiring a revision procedure [17].
  • Inappropriate Shocks: The device may misinterpret a non-dangerous rapid heart rate and deliver an unneeded, painful shock [17].
  • Lifestyle Restrictions: You will have temporary lifting restrictions after the surgery and may face driving restrictions depending on local laws and your rhythm history.

Your Electrophysiologist will help you weigh these risks against the expected benefits to make the best decision for your unique situation [18].

Urgent Action: If you receive a shock from your ICD, experience severe or rapidly worsening breathlessness, unexplained fainting, or sustained rapid palpitations, you must seek emergency medical help.

Common questions in this guide

Does having a spongy-looking heart in LVNC mean I need an ICD?
No. The amount of trabeculation, or spongy appearance, does not by itself determine whether an ICD is needed. Doctors consider prior dangerous rhythms, ejection fraction, medication response, MRI scarring, rhythm-monitor results, symptoms, family history, and personal goals.
When is an ICD considered for primary prevention in LVNC?
A primary-prevention ICD may be considered when a person has not had a cardiac arrest or life-threatening rhythm but is at high future risk. Common criteria include an ejection fraction of 35% or lower after three to six months of tolerated guideline-directed heart-failure medication, relevant symptoms, and expected meaningful survival longer than one year. The decision is individualized.
What findings can raise the risk of dangerous rhythms in LVNC?
Risk may be higher with late gadolinium enhancement, which can indicate heart-muscle scarring; short runs of nonsustained ventricular tachycardia; unexplained fainting; or a close family history of sudden cardiac death. These findings help specialists discuss risk but do not automatically require an ICD.
What is the difference between primary and secondary prevention with an ICD?
Secondary prevention refers to considering an ICD after someone survives a cardiac arrest or life-threatening ventricular rhythm. Primary prevention refers to using an ICD before such an event in someone judged to be at high risk. Overall health, reversible causes, and the person’s goals are also considered.
What are the risks of living with an ICD?
Potential problems include lead movement or breakage, which may require another procedure, and inappropriate shocks when the device mistakes a non-dangerous fast rhythm for an emergency. There may also be temporary lifting limits after implantation and driving restrictions based on local rules and rhythm history.
When should I seek emergency help after an ICD shock?
Seek emergency medical help if you receive a shock, have severe or rapidly worsening breathlessness, unexplained fainting, or sustained rapid palpitations. These symptoms can signal a serious rhythm problem or another urgent condition and should not be assessed at home.

Questions For You

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Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What is my current ejection fraction (EF), and has it been measured after I have been on optimized medications for at least three months?
  2. 2.Does my cardiac MRI show any signs of Late Gadolinium Enhancement (LGE) or scarring?
  3. 3.Have my heart rhythm monitors (like Holter or Zio patches) shown any non-sustained ventricular tachycardia (NSVT) or frequent extra beats?
  4. 4.Given my family history and current heart function, do you consider me at high risk for sudden cardiac arrest?
  5. 5.What are the risks and benefits of an ICD for me specifically, including the risk of 'inappropriate shocks'?

References

References (18)
  1. 1

    Prognostic Significance of Left Ventricular Noncompaction: Systematic Review and Meta-Analysis of Observational Studies.

    Aung N, Doimo S, Ricci F, et al.

    Circulation. Cardiovascular imaging 2020; (13(1)):e009712 doi:10.1161/CIRCIMAGING.119.009712.

    PMID: 31959004
  2. 2

    Predictors of fatal arrhythmic events in patients with non-compaction cardiomyopathy: a systematic review.

    Bazoukis G, Tyrovolas K, Letsas KP, et al.

    Heart failure reviews 2022; (27(6)):2067-2076 doi:10.1007/s10741-022-10257-3.

    PMID: 35776368
  3. 3

    Left Ventricular Hypertrabeculation and Ventricular Arrhythmias.

    Alfieri M, Principi S, Barbarossa A, et al.

    Journal of clinical medicine 2026; (15(9)) doi:10.3390/jcm15093464.

    PMID: 42123201
  4. 4

    Sudden cardiac arrest as the initial presentation for left ventricular noncompaction cardiomyopathy.

    Jakkoju A, Jakkoju R, Kuchana V, et al.

    Proceedings (Baylor University. Medical Center) 2019; (32(4)):564-566 doi:10.1080/08998280.2019.1627781.

    PMID: 31656421
  5. 5

    The Relevance of Preventive Implantable Cardioverter-Defibrillators (ICDs) in Non-Ischemic Cardiomyopathy in the Presence of Effective Quadruple Therapy for Heart Failure: A Review of Contemporary Medical Literature.

    Obi MF, Namireddy V, Reinberg Palmar MA, et al.

    Cureus 2023; (15(4)):e38268 doi:10.7759/cureus.38268.

    PMID: 37255904
  6. 6

    Isolated Left Ventricular Noncompaction Presenting With Heart Failure With Reduced Ejection Fraction and Intrahospital Cardiac Arrest: A Case Report and Literature Review.

    Gonçalves FMF, Batista M, Campos AL, et al.

    Cureus 2022; (14(10)):e30559 doi:10.7759/cureus.30559.

    PMID: 36415422
  7. 7

    Long-Term Prognostic Value of Cardiac Magnetic Resonance in Left Ventricle Noncompaction: A Prospective Multicenter Study.

    Andreini D, Pontone G, Bogaert J, et al.

    Journal of the American College of Cardiology 2016; (68(20)):2166-2181 doi:10.1016/j.jacc.2016.08.053.

    PMID: 27855806
  8. 8

    Prevalence and Prognostic Significance of Left Ventricular Noncompaction in Patients Referred for Cardiac Magnetic Resonance Imaging.

    Ivanov A, Dabiesingh DS, Bhumireddy GP, et al.

    Circulation. Cardiovascular imaging 2017; (10(9)) doi:10.1161/CIRCIMAGING.117.006174.

    PMID: 28899950
  9. 9

    Prevention of sudden death in heart failure with reduced ejection fraction: do we still need an implantable cardioverter-defibrillator for primary prevention?

    Abdelhamid M, Rosano G, Metra M, et al.

    European journal of heart failure 2022; (24(9)):1460-1466 doi:10.1002/ejhf.2594.

    PMID: 35753058
  10. 10

    The Optimal Timing of Primary Prevention Implantable Cardioverter-Defibrillator Referral in the Rapidly Changing Medical Landscape.

    Wong JA, Roberts JD, Healey JS

    The Canadian journal of cardiology 2021; (37(4)):644-654 doi:10.1016/j.cjca.2021.01.024.

    PMID: 33549824
  11. 11

    Emerging concepts in heart failure management and treatment: focus on current guideline-directed medical therapy for heart failure with reduced ejection fraction.

    Ospina González OE, Llanos Mejía DC, Kaplinsky E, et al.

    Drugs in context 2023; (12()) doi:10.7573/dic.2022-6-4.

    PMID: 36660017
  12. 12

    Distribution of Ventricular Fibrosis Associated With Life-Threatening Ventricular Tachyarrhythmias in Patients With Nonischemic Dilated Cardiomyopathy.

    Chimura M, Kiuchi K, Okajima K, et al.

    Journal of cardiovascular electrophysiology 2015; (26(11)):1239-1246 doi:10.1111/jce.12767.

    PMID: 26223827
  13. 13

    Left ventricular noncompaction cardiomyopathy: cardiac, neuromuscular, and genetic factors.

    Finsterer J, Stöllberger C, Towbin JA

    Nature reviews. Cardiology 2017; (14(4)):224-237 doi:10.1038/nrcardio.2016.207.

    PMID: 28079110
  14. 14

    Meta-Analysis of the Prognostic Role of Late Gadolinium Enhancement and Global Systolic Impairment in Left Ventricular Noncompaction.

    Grigoratos C, Barison A, Ivanov A, et al.

    JACC. Cardiovascular imaging 2019; (12(11 Pt 1)):2141-2151 doi:10.1016/j.jcmg.2018.12.029.

    PMID: 30878415
  15. 15

    Clinical Risk Prediction in Patients With Left Ventricular Myocardial Noncompaction.

    Casas G, Limeres J, Oristrell G, et al.

    Journal of the American College of Cardiology 2021; (78(7)):643-662 doi:10.1016/j.jacc.2021.06.016.

    PMID: 34384546
  16. 16

    Comparison of cardiovascular magnetic resonance characteristics and clinical prognosis in left ventricular noncompaction patients with and without arrhythmia.

    Zhou ZQ, He WC, Li X, et al.

    BMC cardiovascular disorders 2022; (22(1)):25 doi:10.1186/s12872-022-02470-7.

    PMID: 35109817
  17. 17

    Clinical outcomes of implantable cardioverter-defibrillator therapy in noncompaction cardiomyopathy: a systematic review and meta-analysis.

    Tukker M, Schinkel AFL, Dereci A, Caliskan K

    Heart failure reviews 2023; (28(1)):241-248 doi:10.1007/s10741-022-10250-w.

    PMID: 35689132
  18. 18

    Left Ventricular Noncompaction Syndrome: Genetic Insights and Therapeutic Perspectives.

    Finsterer J, Stöllberger C

    Current cardiology reports 2020; (22(9)):84 doi:10.1007/s11886-020-01339-5.

    PMID: 32648009

This page is for informational purposes only and does not constitute medical advice. It explains factors that may shape an ICD discussion in LVNC; your cardiologist or electrophysiologist should interpret your results and guide decisions.