Myasthenia gravis electrocardiogram
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1], Associate Editor(s)-in-Chief: Keanu Ngo[2]
Electrocardiogram
Relevance in MG
Electrocardiography has a clinically relevant but not disease-defining role in myasthenia gravis (MG). Cardiac involvement is uncommon as a primary manifestation but may include myocarditis, cardiomyopathy, conduction disease, arrhythmias, and sudden cardiac death.[1] Myocarditis has been reported in approximately 10% of MG patients, and nearly two-thirds of these patients experience a myasthenic crisis during the disease course; dyspnea is frequently the leading manifestation and may be misattributed to respiratory or bulbar weakness.[1]
ECG abnormalities have been reported in approximately 16–88% of MG cohorts, with substantial variation attributable to differences in patient selection and definitions.[1][2]
ECG abnormalities and cardiac involvement
Reported abnormalities include:
- Atrial arrhythmias, including persistent atrial fibrillation
- Atrioventricular conduction abnormalities
- Nonspecific ST-segment depression and T-wave inversion
- QTc prolongation
- Early repolarization
- Left ventricular hypertrophy.[1][2]
In a cohort of MG patients without pre-existing cardiovascular disease, 56.8% had an abnormal ECG, including persistent atrial fibrillation in 10.3%, atrioventricular block in 6.8%, nonspecific ST-segment depression in 29.3%, and T-wave inversion in 29.3%.[2]
Arrhythmia is the most common unexplained cardiac manifestation reported in MG, occurring in approximately 8% of patients in contemporary reviews.[1] Anti-Kv1.4 antibodies may contribute to QTc prolongation through reduction of the transient outward potassium current (Ito), potentially predisposing to torsades de pointes and ventricular tachycardia.[3]
The spectrum of reported cardiac disease includes Takotsubo cardiomyopathy, dilated cardiomyopathy, sick sinus syndrome, sinus bradycardia, and other rhythm or conduction disorders.[1]
ECG as a screen for cardiac involvement
In a cohort of MG patients without pre-existing cardiovascular disease, an abnormal ECG had a sensitivity of 0.70 (95% CI, 0.53–0.84) and specificity of 0.71 (95% CI, 0.62–0.78) for echocardiographic cardiac damage, defined as ejection fraction <55% or E/e′ >8. The negative predictive value was 0.82.[2] These estimates derive from a single small retrospective cohort (n = 58) with acknowledged selection bias and require prospective validation.
An abnormal ECG should prompt further evaluation for cardiac involvement, typically with Echocardiography and cardiac biomarkers when clinically indicated. When an abnormal ECG or unexplained fatigue is present, further evaluation may include serum troponin and BNP/NT-proBNP, targeted examination for an S3 gallop, holosystolic murmur, ankle edema, or pulmonary rales, and echocardiography; a 6-minute walk test may aid functional assessment.[2] A normal ECG does not exclude subclinical cardiac dysfunction, particularly diastolic dysfunction.[2]
MG–myocarditis overlap
Cardiac involvement, particularly myocarditis, is most strongly associated with thymoma-associated MG and with anti-striational antibodies. Anti-titin antibodies show the closest and most specific association with myocarditis, being positive in approximately 89–93% of MG patients with myocarditis, followed by anti-Kv1.4; anti-ryanodine receptor (RyR) antibodies are less specific and may also occur in other myopathies and healthy controls.[4][5]
In a series of 650 MG patients, 70 (10.8%) were anti-Kv1.4-positive. Sixty percent of anti-Kv1.4-positive patients had abnormal ECGs, with frequent T-wave abnormalities and QT prolongation. Clinically suspected myocarditis occurred exclusively in the anti-Kv1.4-positive group and could be associated with ventricular tachycardia, sick sinus syndrome, complete atrioventricular block, and severe heart failure.[6]
New or unexplained dyspnea in MG should therefore not automatically be attributed to respiratory or bulbar weakness. ECG, cardiac biomarkers, and echocardiography should be considered when myocarditis or cardiomyopathy is suspected.[1]
Clinical use and limitations
- A baseline 12-lead ECG may be obtained in patients with MG, particularly when thymoma-associated disease or cardiac-associated autoantibodies are present.[1][6]
- An abnormal ECG in an MG patient without known cardiac disease warrants evaluation for structural or inflammatory cardiac involvement.[2]
- ECG monitoring may be considered during myasthenic crisis, severe exacerbation, and the perioperative period when clinically warranted because arrhythmias and hemodynamic complications may occur.[1]
- Several MG therapies may independently affect cardiac status: corticosteroids may cause hypertension and fluid retention; azathioprine and cyclosporine have potential cardiotoxic effects; and intravenous immunoglobulin or plasma exchange may cause transient hemodynamic instability.[1]
No dedicated major society guideline establishes a standardized routine ECG surveillance protocol specific to MG. The American Heart Association scientific statement on cardiac involvement in neuromuscular disease recommends baseline cardiology evaluation, including examination, ECG, echocardiography, and ambulatory monitoring, at diagnosis and periodic reassessment for several neuromuscular disorders (Class I–IIa, Level of Evidence C), but does not specifically address MG; current MG-specific recommendations derive primarily from cohort studies and expert reviews.[7]
Reported ECG-abnormality prevalence varies substantially between studies, and the prognostic significance of individual ECG abnormalities is not well established.[2][1] Regression of ECG abnormalities following treatment of MG has not been robustly established in contemporary evidence and should not be used alone to attribute an ECG abnormality to MG.[1]
References
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 Messina C (2025). "The overlooked side of myasthenia gravis: the non-motor manifestations—a comprehensive review". Journal of Neurology. 272 (12): 764. doi:10.1007/s00415-025-13504-3.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Kato T, Hirose S, Kumagai S; et al. (2016). "Electrocardiography as the First Step for the Further Examination of Cardiac Involvement in Myasthenia Gravis". BioMed Research International. 2016: 8058946. doi:10.1155/2016/8058946.
- ↑ Lazzerini PE, Capecchi PL, Laghi-Pasini F, Boutjdir M (2017). "Autoimmune channelopathies as a novel mechanism in cardiac arrhythmias". Nature Reviews Cardiology. 14 (9): 521–535. doi:10.1038/nrcardio.2017.61.
- ↑ Kim S, Kim KH, Chung HY; et al. (2023). "Anti-titin antibodies are associated with myocarditis in patients with myasthenia gravis". Journal of Neurology. 270 (3): 1457–1465. doi:10.1007/s00415-022-11485-1.
- ↑ Kufukihara K, Watanabe Y, Inagaki T; et al. (2019). "Cytometric cell-based assays for anti-striational antibodies in myasthenia gravis with myositis and/or myocarditis". Scientific Reports. 9 (1): 5284. doi:10.1038/s41598-019-41730-z.
- ↑ 6.0 6.1 Suzuki S, Baba A, Kaida K; et al. (2014). "Cardiac Involvements in Myasthenia Gravis Associated With Anti-Kv1.4 Antibodies". European Journal of Neurology. 21 (2): 223–230. doi:10.1111/ene.12234. PMID 23829303.
- ↑ Feingold B, Mahle WT, Auerbach S; et al. (2017). "Management of Cardiac Involvement Associated With Neuromuscular Diseases: A Scientific Statement From the American Heart Association". Circulation. 136 (13): e200–e231. doi:10.1161/CIR.0000000000000526.