Mitochondrial Cardiomyopathy
Definition
Cardiomyopathy arising from pathogenic variants in mitochondrial genes encoded by either the nuclear genome or the mitochondrial DNA (mtDNA), causing impaired oxidative phosphorylation (OXPHOS). Primary mitochondrial cardiomyopathies typically manifest with atrioventricular conduction defects and abnormal heart muscle structure or function, and may present as hypertrophic, dilated, or restrictive forms.
Key Concepts
Epidemiology
Phenotypes
mtDNA Syndromes With Cardiac Manifestations
| Syndrome |
Variant(s) |
Key Cardiac Features |
| MELAS |
m.3243A>G (MT-TL1); heteroplasmy 50–80% |
HCM most common; DCM, RCM, hypertrabeculation, WPW, SCD |
| MIDD |
m.3243A>G (MT-TL1); heteroplasmy 10–40% |
HCM, DCM, WPW, AF, sinoatrial node dysfunction |
| MERRF |
m.8344A>G (MT-TK); 83–90% of MERRF |
DCM, HCM, WPW, SVT, RBBB |
| Kearns-Sayre |
Large sporadic mtDNA deletion |
Cardiac involvement up to 50%; SCD up to 20% from heart block; LBBB/RBBB, torsades de pointes |
| LHON |
m.11778G>A, m.3460G>A, m.14484T>C |
HCM, WPW, VT, SCD; mortality doubled |
| Leigh syndrome |
>100 genes (mtDNA and nuclear) |
HCM most common; DCM, WPW, heart block |
| Pearson syndrome |
Large mtDNA deletions (4.9–14 kb) |
LVH, LQT, depolarization abnormalities; most deaths by age 3 |
Nuclear-Encoded Mitochondrial Diseases With Cardiac Manifestations (Selected)
| Disease |
Gene |
Key Cardiac Features |
| Barth syndrome |
TAFAZZIN (X-linked) |
DCM, hypertrabeculation, LQT, WPW, VT, SCD; often presents in infancy, may stabilise by age 5–6; mean life expectancy 40 y |
| DCMA syndrome |
DNAJC19 (AR) |
DCM, LQT; most deaths by 15 months |
| mtDNA depletion |
TWNK/C10orf2 (AD) |
DCM, SCD, PVCs |
| mtDNA depletion |
MGME1 (AR) |
DCM |
| Friedreich ataxia |
FXN triplet repeat (AR) |
HCM, DCM, HF, SVT, AF; mean life expectancy 40 y |
| PPA2 |
PPA2 (AR) |
SCD/VF triggered by minimal alcohol at any age; extreme alcohol hypersensitivity |
| Complex I deficiency |
>30 nuclear genes (AR) |
HCM, DCM, Leigh syndrome |
| Complex III deficiency |
Nuclear-encoded (AR) |
DCM in the context of multisystem/Leigh-spectrum disease |
| Complex IV deficiency |
COX6B1, SURF1, SCO2 (AR) |
DCM, HCM, histiocytoid cardiomyopathy |
| mtDNA depletion (AGK/Sengers) |
AGK (AR) |
Hypertrophic obstructive cardiomyopathy, SCD |
| NDUFB11 deficiency |
NDUFB11 (X-linked) |
VF, VT, histiocytoid CMP, DCM, SCD |
Diagnosis
Cardiac Screening
Management
Contradictions / Open Questions
- The biochemical threshold VAF required for most pathogenic variants outside tRNA genes is unknown; tRNA variants typically require >60% VAF, but this varies with haplogroup, tissue, and age. sources/mitochondrial-cv-aha-2025 ★★★★★
- Whether histiocytoid cardiomyopathy is causally linked to mitochondrial disease remains unresolved due to extreme rarity. sources/mitochondrial-cv-aha-2025 ★★★★★
- Causal vs. secondary vs. bystander role of specific mtDNA deletions/variants in common CVD is unclear. sources/mitochondrial-cv-aha-2025 ★★★★★
- Whether mtDNA copy number or variant level variation within an individual's own tissues or across individuals is more prognostically relevant is understudied. sources/mitochondrial-cv-aha-2025 ★★★★★
Connections
Sources