Cardiac manifestations of myasthenia gravis: A systematic review

Cardiac implications in myasthenia gravis

This editorial aimed to consolidate the current evidence in literature on the association between myasthenia gravis (MG) and cardiac involvement, focusing on the impact of thymoma, antistriational antibodies, and late-onset MG. Additionally, the study aimed to explore the influence of genetic differences among populations on the association with cardiac disease. We conducted a review of existing literature in PubMed and Google Scholar to find relevant studies on cardiac involvement in MG. We created search criteria using a combination of free text words, including MG, antistriational antibodies, thymectomy, cardiomyopathy, myocarditis, arrhythmias, autonomic dysfunction. Relevant articles published in English language were analyzed and incorporated. The findings indicate a strong association between thymoma, myasthenic crisis, antistriational antibodies, and late-onset MG with cardiac involvement. The study also revealed that genetic differences among populations influence the risk of cardiac disease and electrocardiography (ECG) abnormalities in MG patients. Autonomic dysfunctions altered cardiac autonomic response and increased susceptibility to arrhythmias and sudden cardiac death in MG patients. The study supports the significance of thymoma, antistriational antibodies, and late-onset MG as key factors associated with cardiac involvement in MG patients. It emphasizes the importance of ECG as the initial test in managing MG patients, particularly in the perioperative period, to identify and genetic testing if needed to address their cardiac risk effectively.

Perioperative cardiac risks in myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disorder that affects the neuromuscular junction. The primary pathology in MG involves the presence of autoantibodies to acetylcholine receptors (AChRs), which results in qualitative and quantitative reductions in the availability of functional AChRs. Cardiac muscles are also affected, resulting in various perioperative cardiac complications. Antistriational antibodies are commonly reported in MG cases with cardiac involvement. In the presence of thymoma, the prevalence of cardiac manifestations in patients with MG increases to approximately 10%-15%. Cardiac involvement in MG may range from asymptomatic electrocardiogram changes to ventricular tachycardia, myocarditis, conduction disorders, heart failure, and sudden death. Increased incidence of atrial fibrillation, ventricular and supraventricular extra systoles, and prolonged QTc have also been reported in patients with MG. Clinicians should consider the evaluation of autonomic dysfunction and risk of cardiovascular disease in patients with MG.

Autoimmune and Non-Autoimmune Comorbidities in Myasthenic Patients of East-European Descent: A Case-Control Study

Background: As the life expectancy of patients with myasthenia gravis (MG) is improving, so the number of comorbidities continues to rise, with a potentially significant impact on the overall morbidity and mortality. The main aim of the study was to assess comorbidities of MG in a group of patients of East-European descent. Methods: We retrospectively compared 185 adult myasthenic patients with 895 sex- and age-matched controls, admitted from January 2013 to December 2021. Results: Of these patients, 60% had late-onset MG (LOMG), with a clear predominance of women in both the LOMG and early-onset (EOMG) types; and 23.8% of the patients had a radiological description consistent with thymoma. All myasthenic patients had at least one comorbidity; 20 (10.8%) of the patients associated at least one autoimmune comorbidity. Obesity (p < 0.01), type 2 diabetes (p < 0.0001), cerebrovascular diseases (p < 0.0001), essential hypertension (p < 0.01), and cardiac arrythmias (p < 0.0001) were more frequent in patients than in the control group. The granulocyte-to-lymphocyte ratio was higher in the myasthenic patients compared to the controls (p < 0.01 for LOMG). Discussion: We, thus, suggest a common chronic low-grade inflammatory background as a possible connection between MG subtypes and some of these apparently unconnected comorbidities. Conclusions: The East-European origin of the patients offered a different social and cultural angle of a disease studied mainly on populations of West-European and Asian descent.

Correlation between Cardiovascular Autonomic and Pulmonary Ventilation Functions in Myasthenia Gravis Patients

This study aimed to investigate the relationship between pulmonary function and cardiac autonomic function parameters in clinically stable myasthenia gravis (MG) patients. A total of 22 MG patients and 22 healthy controls (HCs) were evaluated. Pulmonary function test parameters, heart rate variability (HRV), baroreflex sensitivity (BRS), and cardiovascular autonomic function test parameters (the Valsalva ratio, expiration/inspiration (E/I) ratio) were assessed. Compared with the HCs, the patients demonstrated a similar diffusion capacity for carbon monoxide (DLCO); a lower forced vital capacity (FVC%pred); a lower forced expiratory volume in 1 s (FEV1%pred); lower BRS and HRV, including high-frequency and total power spectral density; and a higher percentage of abnormal cardiovagal function test results (p < 0.05). A lower BRS in the patient group was associated with worse clinical disease outcomes and reduced pulmonary function (DLCO%pred, R = 0.59; TLC%pred, R = 0.48). Age, forced vital capacity, and total lung capacity predicted the E/I ratio (R2 values ranging from 0.48 to 0.49). Our study demonstrated a significant relationship between a reduced pulmonary ventilation function and respiratory mechanics with cardiovascular autonomic parameters, including the E/I ratio, BRS, and HRV measures at rest, as shown in the MG group. Future studies should focus on the interplay between respiratory and autonomic function testing, as well as pulmonary rehabilitation, to mitigate cardiovascular risk in these patients.

Alterations in short-term blood pressure variability related to disease severity and autonomic symptoms in myasthenia gravis patients

OBJECTIVES

We aimed to evaluate beat-to-beat blood pressure variability (BPV) during head-up tilt test (HUTT) in patients with mild and moderate myasthenia gravis (MG) compared to healthy controls (HCs), and its association with the severity of autonomic symptoms.

METHODS

A total of 50 MG patients and 30 HCs were evaluated. Patients were stratified into 2 groups regarding Myasthenia Gravis Foundation of America (MGFA) classification: mild (I,II MGFA), moderate form (III MGFA). Autonomic symptoms were assessed by COMPASS-31 questionnaire. Cardiovascular parameters, indices of very short-term systolic (SBPV), and diastolic blood pressure (BP) variability (DBPV) were assessed at rest, and during HUTT.

RESULTS

Moderate MG patients were characterized by an overall shift of sympathovagal balance toward sympathetic predominance, either at rest and during HUTT, as well as lower values of high frequency (HFnu) of DBPV during HUTT, compared to HCs and mild MG. Similarly, moderate MG showed higher resting low frequency (LFnu) of DBPV (p=0.035), higher COMPASS-31 score (p=0.031), and orthostatic intolerance sub-score (p=0.019) than mild MG patients. Compared to HCs, mild MG patients showed lower Δmean BP (p=0.029), Δdiastolic BP (p=0.016). Autonomic symptoms were associated with lower BP values, at rest and during HUTT, and lower LF BPV parameters during HUTT.

CONCLUSION

MG patients present significant alterations in BPV, both at rest and in response to orthostatic stress, which are related to autonomic symptoms and disease severity. This study confirms the importance of monitoring BPV when evaluating cardiovascular autonomic function and its evolution over the course of MG disease.

Eyes and the heart: what a clinician should know

The eye is prone to various forms of afflictions, either as a manifestation of primary ocular disease or part of systemic disease, including the cardiovascular system. A thorough cardiovascular examination should include a brief ocular assessment. Hypertension and diabetes, for example, would present with retinopathy and dyslipidaemia would present with corneal arcus. Multisystem autoimmune diseases, such as Graves' disease, rheumatoid arthritis and sarcoidosis, would present with proptosis, episcleritis and scleritis, respectively. Myasthenia gravis, while primarily a neuromuscular disease, presents with fatigable ptosis and is associated with Takotsubo cardiomyopathy and giant cell myocarditis. Connective tissue diseases such as Marfan syndrome, which commonly presents with aortic root dilatation, would be associated with ectopia lentis and myopia. Wilson's disease, which is associated with arrhythmias and cardiomyopathies, would present usually with the characteristic Kayser-Fleischer rings. Rarer diseases, such as Fabry disease, would be accompanied by ocular signs such as cornea verticillata and such cardiac manifestations include cardiac hypertrophy as well as arrhythmias. This review examines the interplay between the eye and the cardiovascular system and emphasises the use of conventional and emerging tools to improve diagnosis, management and prognostication of patients.

Anti-titin antibodies are associated with myocarditis in patients with myasthenia gravis

BACKGROUND

Myasthenia gravis (MG) can affect cardiac muscles with variable presentations. Myocarditis is a rare but potentially serious cardiac manifestation of MG. Although thymomas and anti-titin antibodies have been suggested as risk factors for myocarditis in patients with MG, their independent influence on myocarditis has rarely been assessed.

METHODS

A retrospective chart review was conducted on 247 patients diagnosed with MG who were tested for anti-titin antibodies. Myocarditis was diagnosed on the basis of the European Society of Cardiology 2013 Task Force criteria for clinically suspected myocarditis. Patients were classified into myocarditis-positive and myocarditis-negative groups. Multivariate analysis was performed to analyze the risk factors for myocarditis.

RESULTS

Of the 247 patients, 25 (10.1%) were myocarditis-positive and 222 (89.9%) were myocarditis-negative. Anti-titin antibody positivity was higher in the myocarditis-positive group than in the myocarditis-negative group (68.0% vs. 28.4%, p < 0.001). A history of MG crisis was more frequent in the myocarditis-positive group than in the myocarditis-negative group (64.0% vs. 10.4%, p < 0.001). The presence of anti-titin antibodies (odds ratio [OR] 7.906; confidence interval [CI] 2.460-25.401) and MG crisis (OR 24.807; CI 7.476-82.311) was significantly associated with myocarditis. The Cox regression model showed that the anti-titin antibody levels (hazard ratio [HR] 3.639; 95% CI 1.557-8.505) and MG crisis (HR 6.137; 95% CI 2.639-14.272) were significant risk factors for the development of myocarditis.

CONCLUSION

The presence of anti-titin antibody was associated with myocarditis in patients with MG, whereas thymoma was not. Although rare, early suspicion of myocarditis could be required, especially in patients with MG having anti-titin antibodies.

Cardiac Toxicity Associated with Immune Checkpoint Inhibitors: A Systematic Review

Immune checkpoint inhibitors (ICIs) are an important advancement in the field of cancer treatment, significantly improving the survival of patients with a series of advanced malignancies, like melanoma, non-small cell lung cancer (NSCLC), hepatocellular carcinoma (HCC), renal cell carcinoma (RCC), and Hodgkin lymphoma. ICIs act upon T lymphocytes and antigen-presenting cells, targeting programmed cell death protein 1 (PD1), programmed cell death protein ligand 1 (PD-L1), and cytotoxic T-lymphocyte antigen 4 (CTLA-4), breaking the immune tolerance of the T cells against malignant cells and enhancing the body's own immune response. A variety of cardiac-adverse effects are associated with ICI-based treatment, including pericarditis, arrhythmias, cardiomyopathy, and acute coronary syndrome, with myocarditis being the most studied due to its often-unexpected onset and severity. Overall, Myocarditis is rare but presents an immune-related adverse event (irAE) that has a high fatality rate. Considering the rising number of oncological patients treated with ICIs and the severity of their potential adverse effects, a good understanding and continuous investigation of cardiac irAEs is of the utmost importance. This systematic review aimed to revise recent publications (between 2016-2022) on ICI-induced cardiac toxicities and highlight the therapeutical approach and evolution in the selected cases.

Association of Cardiac Autonomic Responses with Clinical Outcomes of Myasthenia Gravis: Short-Term Analysis of the Heart-Rate and Blood Pressure Variability

Introduction: The aim of the study was to assess cardiac and autonomic function in patients with myasthenia gravis (MG) and to explore its relationship with disease outcomes. Methods: Thirty-eight patients with an MG were enrolled (median age 40.5 years; median disease duration 5.5 years). Cardiovascular parameters, baroreflex sensitivity (BRS), spectral indices of short-term heart rate (HRV), and systolic blood pressure variability (SBPV) were compared with age- and gender-matched controls (n = 30). Cardiac autonomic function was assessed during the response to standing (tilt) and deep breathing tests (expiration/inspiration ratio-E/I). Results: HR and BP responses to the tilt test were similar in both groups. MG patients, as compared to controls, were characterized by altered SBPV at rest, significantly reduced HR response to the deep breathing test (p < 0.001), increased sympathovagal balance after tilt (delta LF/HF-RRI, p = 0.037), and lower values of BRS (p = 0.007) and hemodynamic parameters, i.e., cardiac index, index contractility, left ventricular work index, at rest and during tilt. There was no association between disease duration and autonomic parameters. Disease severity, as determined by MGFA (Myasthenia Gravis Foundation of America) corrected for age and sex, was an independent predictor of diminished vagal tone (E/I ratio) and increased sympathetic response to tilt (delta LF/HF-RRI) as measured with HRV. Lower BRS was associated with greater disease severity and older age. Hemodynamic parameters were predominantly predicted by age and sex. Conclusion: Our results confirm cardiac autonomic dysfunction among MG patients with predominant parasympathetic impairment. Clinicians should consider evaluation of autonomic balance in MG patients with, or at risk for, cardiovascular disease.

Complete atrioventricular block under epidural ropivacaine infusion in a patient with first-degree atrioventricular block and myasthenia gravis: a case report

Background

First-degree atrioventricular block (AVB) may lead to complete AVB. Herein, we present a case of a complete AVB under thoracic epidural catheter infusion of ropivacaine with fentanyl in a patient with first-degree AVB and myasthenia gravis.

Case presentation

A 74-year-old woman with first-degree AVB underwent thymectomy for myasthenia gravis. Continuous thoracic epidural catheter infusion of 0.2% ropivacaine with fentanyl was initiated at 15 min before the end of the surgery. At 9 h postoperatively, the electrocardiogram showed a 10-s-long pause due to complete AVB. Thus, a temporary pacemaker was implanted, and at 19 h postoperatively on postoperative day 1, cardiac pacing was initiated and lasted approximately 30 s. After catheter removal, she had no further episodes of complete AVB.

Conclusion

First-degree AVB may lead to complete AVB under the influence of thoracic epidural infusion of ropivacaine in patients with myasthenia gravis.

Does Cardiovascular Autonomic Dysfunction Contribute to Fatigue in Myasthenia Gravis?

Myasthenia gravis (MG) is an autoimmune disease characterized by fatigable muscle weakness. Despite full spontaneous or pharmacological remission some MG patients still complain of physical and mental fatigue. Fatigue has been related to autonomic dysregulation. The aim of this study was to assess autonomic responses in a group of MG patients in complete remission but complaining of persistent fatigue. Seventeen well-regulated but persistently fatigued MG patients and 17 individually matched controls underwent echocardiography assessing systolic and diastolic heart function. Beat to beat cardiovascular responses at rest and to 30o head-up tilt, tilt-back, and 2-min static handgrip contraction were recorded. Fatigued MG patients had a statistically significant higher resting HR than their matched controls (p=0.03). The difference in resting heart rate between MG patients not using acetylcholine esterase inhibitors (AChEi) and their matched controls was even more pronounced (p=0.007). The autonomic cardiovascular adjustments to head-up tilt, tilt-back and handgrip contraction were not statistically significant different between patients and controls. We found a higher resting heart rate in all well-regulated but fatigued MG patients compared with controls. The difference was more pronounced between patients not taking AChEi compared to their matched controls. This finding may reflect a disturbed resting sympathovagal balance and this might be a contributing factor to the fatigue symptoms.

[Morphological and immunogistochemical characteristics of myocardial damage in miastenia]

The article presents a rare clinical case of a 45-year-old patient with generalized myasthenia with damages to the muscular apparatus of the extremities and the heart. A special feature of the case was myocardial damage evident as alterative-productive interstitial myocarditis with a peculiar immune phenotype of cell infiltrate, Cd3+, Cd4+, Cd8-, Cd68+. Furthermore, Cd68-expressing cells were presented by large macrophages with cytoplasmic granulation, which surrounded damaged cardiomyocytes. Around sites of cardiomyocyte alteration there were manifestations of neoangiogenesis with signs of Cd34 protein expression in thin-wall, capillary type blood vessels. These morphological and immunohistochemical changes in the myocardium supplement the concept of myasthenia morphogenesis.

Kidney Function in Patients With Neuromuscular Disease: Creatinine Versus Cystatin C

Background: Accurate measurement of kidney function in patients with neuromuscular disorders is challenging. Cystatin C, a marker not influenced by skeletal muscle degradation, might be of clinical value in these patients.

Methods: We consecutively enrolled 39 patients with neuromuscular disorders. We investigated the association of the eGFR, based on plasma creatinine and Cystatin C, with clinical and biochemical variables associated with kidney function, namely age and galectin-3.

Results: Creatinine-based eGFR was 242 (±80) and Cystatin C-based eGFR was 110 (±23) mL/min/1.73 m². Cystatin C-based eGFR was associated with age (β −0.63 p < 0.0001) and galectin-3 levels (β −0.43 p < 0.01), while creatinine-based eGFR was not (β −0.22 p = 0.20; β −0.28 p = 0.10). Sensitivity analyses in Duchenne and Becker patients revealed the same results: Cystatin C-based eGFR was associated with age (β −0.61 p < 0.01) and galectin-3 levels (β −0.43 p = 0.05), while creatinine-based eGFR was not (β −0.32 p = 0.13; β −0.34 p = 0.14).

Conclusions: These data indicate that estimation of renal function in patients with neuromuscular disorders cannot reliably be achieved with creatinine, while Cystatin C appears a reasonable alternative. Since a large proportion of patients with neuromuscular disorders develops heart failure, and requires heart failure medication, adequate monitoring of renal function is warranted.

Cardiac Autonomic Dysfunction in Myasthenia Gravis and Relapsing-Remitting Multiple Sclerosis-A Pilot Study

This study assessed cardiac autonomic response to head-up tilt test (HUTT) in 23 myasthenia gravis (MG) and 23 relapsing-remitting multiple sclerosis (RRMS) patients compared to 30 healthy controls (HC). Task Force® Monitor was used to evaluate cardiac inotropy parameters, baroreflex sensitivity (BRS), heart rate (HRV), and blood pressure variability (BPV) during HUTT. MG patients were characterized by reduced BRS (p < 0.05), post-HUTT decrease in high-frequency component (p < 0.05) and increase in sympathovagal ratio of HRV (p < 0.05) when compared to controls indicating parasympathetic deficiency with a shift of sympathovagal balance toward sympathetic predominance. Compared to HC, MG patients also showed lower cardiac inotropy parameters, specifically, left ventricular work index (LVWI) during supine rest (p < 0.05) as well as LVWI and cardiac index values in response to orthostatic stress (p < 0.01 and p < 0.05, respectively). Compared to controls, RRMS patients were characterized by lower HRV delta power spectral density (p < 0.05) and delta low-frequency HRV (p < 0.05) in response to HUTT suggesting combined sympathetic and parasympathetic dysfunction. There were no differences in cardiac autonomic parameters between MG and MS patients (p > 0.05). Our study highlights the possibility of cardiac and autonomic dysfunction in patients with MG and RRMS which should be considered in the pharmacological and rehabilitation approach to managing these conditions.

Guideline No. 416: Labour, Delivery, and Postpartum Care for People with Physical Disabilities

OBJECTIVE

To describe evidence-based practice for managing the labour, delivery, and postpartum care of people with physical disabilities in Canada.

TARGET POPULATION

This guideline addresses the needs of people with physical disabilities, with a focus on conditions that affect strength and mobility, as well as those that affect neurological or musculoskeletal function or structure. Although aspects of this guideline may apply to people with solely intellectual, developmental, or sensory disabilities (e.g., hearing and vision loss), the needs of this population are beyond the scope of this guideline.

OUTCOMES

Safe and compassionate care for people with physical disabilities who are giving birth.

BENEFITS, HARMS, AND COSTS

Implementation of this guideline will improve health care provider awareness of specific complications people with physical disabilities may experience during labour, delivery, and the postpartum period and therefore increase the likelihood of a safe birth.

EVIDENCE

A literature review was conducted using MEDLINE (474), Embase (36), and the Cochrane Central Register of Controlled Trials (CENTRAL; 28) databases. The results have been filtered for English language, publication date of 2013 to present, observational studies, systematic reviews, meta-analyses, and guidelines and references in these publications were also reviewed.

VALIDATION METHODS

The authors rated the quality of evidence and strength of recommendations using the Grading of Recommendations Assessment, Development and Evaluation approach. See online Appendix A (Tables A1 for definitions and A2 for interpretations of strong and weak recommendations).

INTENDED AUDIENCE

Maternal-fetal medicine specialists, obstetricians, family physicians, nurses, midwives, neurologists, physiatrists, and those who care for people with physical disabilities.

RECOMMENDATIONS

Acetylcholinesterase Inhibitors in Myasthenic Crisis: A Systematic Review of Observational Studies

Current myasthenia gravis guidelines recommend intravenous immunoglobulin or plasmapheresis and discontinuation of pyridostigmine during myasthenic crisis. However, intravenous immunoglobulin or plasmapheresis is expensive and frequently not available in developing countries. This study aims to summarize the evidence of giving an acetylcholinesterase inhibitor in myasthenic crisis. Medline, Embase, and Cochrane databases and references were searched for observational studies that determined the use of acetylcholinesterase inhibitor in myasthenic crisis. The eligibility criteria were as follows: population, patients with myasthenic crisis, intervention (acetylcholinesterase inhibitor administration), and outcome (clinical improvement and complications). In total, 106 studies were identified, 92 through database searching (after removing duplicates) and 14 through other sources. Only eight were analyzed in the present systematic review. In five, acetylcholinesterase inhibitor was given at the start of the crisis, whereas in the other three, acetylcholinesterase inhibitor was discontinued initially and then restarted prior to extubation. Two observational analytic studies and three case reports showed improvement in different outcome measures. In the other three, improvement of outcome measures was also observed. Overall, a small proportion of patients developed cardiac arrhythmia and pneumonia after administration of acetylcholinesterase inhibitor alone, although this was not statistically different compared with those subjected to plasmapheresis. In summary, continuous intravenous infusion of pyridostigmine or neostigmine can be a substitute for intravenous immunoglobulin or plasmapheresis if these are not available during crisis; however, caution should be observed because of the aforementioned possible complications.

Concomitant development of neurologic and cardiac immune-related adverse effects in patients treated with immune checkpoint inhibitors for melanoma

Immune checkpoint inhibitors (ICI) have altered the prognosis of patients with melanoma over the past few years, with immune-related adverse effects (irAEs) being the only factor limiting their use. Neurologic and cardiac irAEs are rare, but usually severe. We reviewed the files of patients with melanoma treated with ICIs in one center to retrieve data from patients with neurologic irAEs. Patients with a combination of neurologic and cardiac manifestations were further analyzed. We also reviewed the literature for similar syndromes. Five out of 482 (1.01%) patients developed a neurologic syndrome and we present three patients with a constellation of neurologic and cardiac irAEs. A 66-year-old woman and a 68-year-old man presented with a constellation of findings after being treated with ipilimumab and nivolumab, respectively, for melanoma in the adjuvant setting and were eventually diagnosed with myasthenia gravis with cardiac involvement. An 80-year-old woman developed diffuse asymmetric muscle weakness, bilateral ptosis and asymptomatic high serum troponin levels after adjuvant treatment with nivolumab and ipilimumab for a stage IIIB melanoma. After excluding ischemic heart disease, she was diagnosed with axonal polyradiculoneuropathy and myocarditis. Neurologic or cardiac irAEs in patients treated with ICIs are uncommon (<1%), but usually severe, with high rates of morbidity and fatality. The co-development of neurologic and cardiac irAEs is even more rare and can arise soon after exposure to ICIs and escalate rapidly. Since more and more patients are now treated with ICIs in the adjuvant setting, prompt identification and management are essential to avoid serious complications or death.

Pyridostigmine induced heart block requiring ICU admission

Myasthenia gravis is an autoimmune disorder that effects an estimated 20 people per 100,000 in the USA per year. Pyridostigmine is a common drug used in the symptomatic treatment of myasthenia gravis. While generally safe and effective, a rare set of patients treated with pyridostigmine encounter cardiac conduction disorders. Here, we report a rare presentation of an adverse drug reaction due to pyridostigmine, which is important for its implications in the acute care setting.

A Case Report of Recurrent Takotsubo Cardiomyopathy in a Patient during Myasthenia Crisis

Introduction

Patients with myasthenia crisis can develop Takotsubo stress cardiomyopathy (SC) due to emotional or physical stress and high level of circulating catecholamines. We report a patient who developed recurrent Takotsubo cardiomyopathy during myasthenia crisis. Coexisting autoimmune disorders known to precipitate stress cardiomyopathy like Grave's disease need to be evaluated.

Case Report

A 69-year-old female with seropositive myasthenia gravis (MG), Grave's disease, and coronary artery disease on monthly infusion of intravenous immunoglobulin (IVIG), prednisone, pyridostigmine, and methimazole presented with shortness of breath and chest pain. Electrocardiogram (ECG) showed ST elevation in anterolateral leads with troponemia. Coronary angiogram was unremarkable for occlusive coronary disease with left ventriculogram showing reduced wall motion with apical and mid left ventricle (LV) hypokinesis suggestive of Takotsubo stress cardiomyopathy. Her symptoms were attributed to MG crisis. Her symptoms, ECG, and echocardiographic findings resolved after five cycles of plasma exchange (PLEX). She had another similar episode one year later during myasthenia crisis with subsequent resolution in 10 days after PLEX.

Conclusion

Takotsubo cardiomyopathy can be one of the manifestations of myasthenia crisis with or without coexisting Grave's disease. These patients might benefit from meticulous fluid status and cardiac monitoring while administering rescue treatments like IVIG and PLEX.

Population pharmacokinetic analysis of tacrolimus in Chinese myasthenia gravis patients

The importance of tacrolimus in the treatment of myasthenia gravis (MG) as a substitute for corticosteroid-dependent immunosuppressive therapy is increasing. Thus far, however, no population pharmacokinetic (PopPK) analysis of tacrolimus in treating MG patients has been published. This article aimed to construct a PopPK model of tacrolimus for Chinese MG patients with the goal of improving its performance in MG treatment. A total of 253 trough concentration records were obtained from 83 Chinese MG patients. The effects of demographics, lifestyle and health status, biochemical test data, disease progression and treatment-related information (including co-administered medications) as covariates on the various parameters were investigated. The covariate selection was based on biological plausibility, clinical significance, statistical significance and reduction in inter-individual variability (IIV). Bootstrap and normalized prediction distribution error (NPDE) analysis were performed to validate the final model. A one-compartment PopPK model with first-order elimination and a fixed absorption phase was constructed. The estimated apparent oral clearance (CL/F) and apparent oral volume of distribution (V/F) were 3.6 L/h and 1700 L, respectively, in the MG patients. Hematocrit and blood urea nitrogen were identified as two covariates that significantly influenced the CL/F. Immunoglobulin treatment (PRO) also had the potential to influence V/F, which was consistent with the clinical observations and the high protein-binding property of tacrolimus. Other covariates including age, weight, gender and co-administered medications had no obvious influence on CL/F or V/F. The first PopPK model of tacrolimus in MG patients was established. The identified covariates were of biological plausibility and clinical importance to help individualize the dosing schedule in MG patients.

Pyridostigmine Induced Prolonged Asystole in a Patient with Myasthenia Gravis Successfully Treated with Hyoscyamine

Reversible acetylcholinesterase inhibitors are used as first-line treatment for myasthenia gravis. They improve symptoms by increasing concentration of acetylcholine at the neuromuscular junction and stimulating nicotinic receptors. Serious bradyarrhythmias can occur from muscarinic stimulation in heart, which in rare cases may progress to asystole. These patients can initially be managed with hyoscyamine, a muscarinic antagonist. Persistence of bradyarrhythmias even after hyoscyamine treatment may warrant pacemaker placement. We present a case of 65-year-old female patient who presented with diplopia, dysphagia, and muscle weakness who was diagnosed with myasthenia gravis. She developed significant sinoatrial node block with prolonged asystole after starting treatment with pyridostigmine which was successfully treated with hyoscyamine, thus avoiding pacemaker placement.