ST-Segment Elevation Myocardial Infarction in a Patient With Myasthenia Gravis After Intravenous Immunoglobulin Infusion

Abstract

Background

Acute coronary syndrome is rare in patients with myasthenia gravis, with only limited literature available. We report an atypical case of ST-segment elevation myocardial infarction (STEMI) that occurred after intravenous immunoglobulin (IVIg) infusion in a patient with myasthenia gravis.

Case Summary

A 36-year-old woman with a longstanding history of myasthenia gravis developed acute chest pain and ST-segment elevation on electrocardiogram after IVIg administration. Emergent coronary angiography revealed total thrombotic occlusion of the left anterior descending artery. Percutaneous coronary intervention with thrombectomy was successfully performed, and stenting was not required. The patient was discharged in stable condition after hospitalization for an additional 17 days.

Discussion

This report highlights an atypical case of STEMI in a young patient without conventional atherosclerotic risk factors, presumably triggered by an IVIg infusion.

Take-Home Message

Clinicians should be aware of the potential risk of thrombotic cardiac events associated with IVIg administration during the treatment of myasthenia gravis.

Visual Summary

History of Presentation

A 36-year-old woman was admitted to the neurology department via the emergency room for bilateral lower limb weakness, attributed to myasthenia gravis. On hospital day 7, she experienced an acute deterioration in her neurological symptoms, including worsening dysphagia, dyspnea with oxygen desaturation (SpO₂: 90%), and inability to ambulate. Consequently, intravenous immunoglobulin (IVIg) was initiated at 0.4 g/kg/d and administered for 4 consecutive days using IV-Globulin SN (GC Pharma); the infusion rate followed the manufacturer's recommendations. The patient's neurological symptoms gradually improved after the treatment; however, on the morning of the planned fifth dose of IVIg, the patient suddenly developed dizziness and chest discomfort.

Take-Home Messages

• •IVIg infusion may induce coronary thrombotic events even in young patients without conventional cardiovascular risk factors.
• •Careful monitoring of patients receiving IVIg is recommended, and further studies are needed to establish optimal preventive measures.

Past Medical History

The patient had a 9-year history of myasthenia gravis, epilepsy, depressive disorder, and iron-deficiency anemia. She denied any history of chest pain, prior coronary angiography, smoking, hyperlipidemia, diabetes mellitus, or a family history of cardiovascular disease. Previous electrocardiograms (ECGs) were unremarkable. Her chronic medications included prednisolone 5 mg/once daily, pyridostigmine 360 mg/3 times a day, tacrolimus 3 mg/once daily for myasthenia gravis; zonisamide 200 mg/twice daily for epilepsy; and esitalopram 5 mg/once daily and alprazolam 0.375 mg/once daily for depressive disorder. Additionally, she had previously received IVIg infusion on 2 occasions: once for COVID-19 and once during a prior hospitalization for myasthenia gravis exacerbation.

Investigations

Initial evaluation by the neurology team revealed hypotension, with a blood pressure of 90/50 mm Hg, and ECG showed ST-segment elevation in leads V₂ and V₃ with reciprocal changes in leads II, III, and aVF (Figure 1). Emergent cardiology consultation was arranged, and the patient was diagnosed with ST-segment elevation myocardial infarction (STEMI) complicated by cardiogenic shock. Two hours later, emergent coronary angiography revealed complete thrombotic occlusion of the proximal left anterior descending artery (LAD) (Figure 2A). No significant stenoses were observed in the left main, left circumflex, or right coronary arteries.

Figure 1.

Electrocardiogram at the Onset of Chest Pain

Figure 2.

Coronary Angiography During Percutaneous Coronary Intervention

(A) Total occlusion of the LAD before PCI. (B) Successful reperfusion of the LAD was achieved after PCI. LAD = left anterior descending artery; PCI = percutaneous coronary intervention.

Percutaneous coronary intervention (PCI) was performed targeting the LAD lesion. Laboratory tests performed immediately after PCI showed a hemoglobin level of 9.8 g/dL, white blood cell count of 10,460/μL, platelet count of 227,000/μL, serum creatinine 0.4 mg/dL, aspartate aminotransferase/alanine aminotransferase 411/31 IU/L, creatine kinase-MB 300 ng/mL, and troponin T >10 ng/mL. Lipid profile showed total cholesterol 160 mg/dL and low-density lipoprotein cholesterol 81 mg/dL.

Management

Regarding the PCI procedure, an initial thrombectomy achieved TIMI flow grade 1. Subsequent balloon angioplasty using a 2.5 × 20 mm noncompliant balloon was performed at the proximal LAD. Multiple subsequent thrombectomies extracted red thrombus material and ultimately restored TIMI flow grade 3, extending to the mid-to-distal LAD. Two additional thrombectomies were performed in the diagonal branch, although persistent distal occlusion was considered manageable with medical therapy. Given that the residual stenosis was <30%, stent placement was deferred (Figure 2B). The entire procedure was completed within 90 minutes.

Outcome and Follow-Up

After PCI, the patient received intravenous norepinephrine and heparin for that day. As the thrombotic event was not attributable to underlying atherosclerosis, anticoagulation with edoxaban 60 mg/once daily plus clopidogrel 75 mg/once daily was initiated. After 1 month of dual therapy, a plan was made to continue edoxaban 60 mg/once daily as lifelong monotherapy, considering the ongoing need for IVIg treatment in managing her myasthenia gravis.

While the patient was recovering from PCI, a pathologic Q-wave was observed on ECG in leads V₁ to V₃ (Figure 3). Transthoracic echocardiography additionally demonstrated moderate left ventricular systolic dysfunction (Videos 1 and 2). Medical therapy for ischemic cardiomyopathy was applied, including empagliflozin 10 mg/once daily and sacubitril/valsartan 50 mg/twice daily. Rosuvastatin 20 mg/once daily was also prescribed. However, sacubitril/valsartan was discontinued after 6 days owing to hypotension. A 24-hour Holter monitor was performed to evaluate for arrhythmias, including paroxysmal atrial fibrillation, but no abnormalities were detected.

Figure 3.

Electrocardiogram 7 Days After Percutaneous Coronary Intervention

The patient was hospitalized for an additional 17 days after PCI. Her chest pain gradually resolved, and coronary computed tomography angiography confirmed that residual stenosis or occlusion was absent (Figure 4). Eventually, the patient was discharged in stable cardiovascular conditions.

Figure 4.

Coronary Computed Tomography Angiography 15 Days After Percutaneous Coronary Intervention

Clockwise from top left: Three-dimensional reconstruction of the coronary artery tree, left anterior descending artery, right coronary artery, and left circumflex artery.

Discussion

We report a unique case of STEMI in a woman in her 30s with a longstanding history of myasthenia gravis. The pathophysiology in this case appears distinct from the classic plaque rupture–associated atherothrombotic events in coronary artery disease. The most plausible cause of STEMI in this case was thrombosis triggered by IVIg therapy.

To the best of our knowledge, this is the first reported case of STEMI after IVIg administration in a patient with myasthenia gravis. The previously reported etiologies of ischemic heart injury in myasthenia gravis include pyridostigmine-induced events, coronary artery vasospasm, and perioperative cardiac injury.1, 2, 3 In the present case, the patient received IVIg infusions over 4 consecutive days, and chest pain appeared 1 day after the last IVIg infusion. Notably, the patient's other chronic medications and supportive treatments remained unchanged. Comprehensive cardiac evaluation, including repeated echocardiography, revealed no evidence of intracardiac thrombosis or shunt (Videos 1 to 3). Thus, IVIg was the sole newly administered therapy.

IVIg therapy increases serum viscosity, which in turn increases vascular resistance and may lead to abnormal blood flow.⁴ Moreover, high-dose IVIg infusion may activate the vascular endothelium through immune complex interaction and may increase von Willebrand factor levels, thereby promoting a procoagulant state.⁵ Such changes in hemostatic balance may be particularly detrimental in vascular regions with turbulent flow, such as the proximal LAD, which was the site of occlusion in our patient. Although the patient previously received IVIg without thrombotic complications, this event suggests that past tolerance cannot fully exclude the risk of future thrombosis.

A variety of thromboembolic events associated with IVIg therapy—including ischemic stroke, myocardial infarction, deep vein thrombosis, and pulmonary embolism—have been documented in the literature.⁶ These events tend to occur more frequently in individuals with established risk factors such as aging, obesity, diabetes mellitus, dyslipidemia, or known hypercoagulable states. What makes this case particularly notable is that the patient was a young woman with no conventional risk factors of thrombosis. Still, hospitalization-related immobility and underlying iron-deficiency anemia may have contributed to a prothrombotic milieu. Furthermore, although myasthenia gravis itself does not inherently increase the thromboembolic risk, long-term use of corticosteroids and pyridostigmine may have indirectly contributed to a hypercoagulable state. Possible cardiac manifestations of myasthenia gravis, such as arrhythmia or myocarditis, may contribute to thrombosis formation owing to anticardiac antibodies.⁷ However, there were no observed findings that supported such involvement in this case.

Interestingly, our case was consistent with the location of the thrombotic lesion in a previously reported case of IVIg-induced STEMI, in which the patient exhibited >90% stenosis in the proximal LAD, along with 70% to 90% stenosis in the first marginal branch.⁸ The proximal LAD region tends to have complex blood flow patterns given its curvature and branching, and it is therefore susceptible to thrombosis or atheroma formation. Occlusion of the proximal LAD is associated with an unfavorable prognosis, as it supplies oxygen to a broad range of myocardial territories.

In our case, PCI was successfully performed within a relatively short period after the onset of chest pain. Successful reperfusion was achieved even without stent placement, and follow-up coronary computed tomography angiography confirmed good function in all 3 coronary arteries. These findings indicated that the coronary occlusion was due to an acute thrombotic event rather than classic atherosclerotic plaque rupture. Accordingly, only a limited number of established management strategies were available for this case.⁹

Treatment for our patient consisted of lifelong monotherapy with edoxaban, considering her anticipated need for ongoing IVIg therapy, and she has had no recurrences to date. Given the nonatherosclerotic mechanism of myocardial infarction and the high bleeding risk associated with prolonged dual antithrombotic therapy, anticoagulant monotherapy was considered a more appropriate long-term strategy in this case. However, the optimal period for anticoagulation therapy—whether lifelong or limited to periods of IVIg administration—remains unclear. Further studies are needed to establish evidence-based guidelines for similar cases. Additionally, preventive strategies for thrombotic complications during IVIg treatment should be further explored. The currently suggested methods to mitigate the risk of thrombotic events during IVIg infusion include maintaining hydration, infusing the IVIg regimen at a slower rate, and using a combination of antiplatelet and anticoagulation therapy before IVIg infusion.¹⁰ Considering the present case of IVIg-associated STEMI, additional precautions such as avoiding prolonged immobilization during hospitalization and monitoring for early changes in hematocrit or clinical indicators of hyperviscosity may also be warranted.

Conclusions

This case is especially significant given the patient's young age and lack of atherosclerotic lesions, which contrast with the usual IVIg-related thrombosis demographic. Because of the potentially fatal consequences of IVIg-associated thrombosis, it highlights the need for increased clinical awareness in patients undergoing high-dose therapy or with thrombotic risk factors. Close cardiovascular monitoring and development of preventive measures for myocardial infarction during and after IVIg therapy may be necessary in certain patients to enable early detection and prompt management of thrombotic events.

Funding Support and Author Disclosures

This study was supported by the Soonchunhyang University Research Fund. The authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Appendix

Video 1

Echocardiogram After Percutaneous Coronary Intervention (Apical 4-Chamber View)

Video 2

Echocardiogram After Percutaneous Coronary Intervention (Apical 4-Chamber View)

Video 3

Echocardiogram After Percutaneous Coronary Intervention (Subcostal View)