Microvascular Cardiomyopathy: A Distinct Driver Of RV Dysfunction In CTD-PAH

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Author Block: Danielle Howell¹, David Kim¹, Mohil Garg¹, Ayan Purkayastha¹, Ningxin Wan², Jennifer McLeod², Reema Bhatt². ¹NewYork Presbyterian Queens Hospital, Flushing, NY; ²NewYork Presbyterian- Weill Cornell Medical Center, New York, NY
Disclosure Block: D. Howell: None. D. Kim: None. M. Garg: None.

Background: Right ventricular (RV) failure in connective tissue disease-associated pulmonary arterial hypertension (CTD-PAH) is typically attributed to increased afterload. However, immune-mediated cardiac and microvascular injury may amplify RV dysfunction, creating a diagnostic and therapeutic dilemma.
Case: A 32-year-old woman with no prior medical history presented with chest pain, dyspnea, arthralgia, and syncope. ECG showed sinus tachycardia with diffuse low-voltage QRS complexes. Labs revealed high inflammatory markers, mild troponin elevation, and markedly elevated pro-BNP. Imaging demonstrated diffuse lymphadenopathy, pulmonary edema, and pericardial effusion. Autoimmune workup confirmed systemic lupus erythematosus (SLE) with mixed connective tissue disease (MCTD) overlap. Lymph node biopsy excluded malignancy, and high-dose corticosteroids and hydroxychloroquine were initiated. Echocardiography showed severe RV dilation and dysfunction with septal flattening. RHC confirmed precapillary pulmonary hypertension (RA 5mmHg, mPAP 32 mmHg, PCWP 10 mmHg, PVR 8.27 WU, CI 1.71 L/min/m²), without vasoreactivity, requiring ICU care with inotropic support. Cardiac MRI showed elevated extracellular volume without late gadolinium enhancement. Endomyocardial biopsy showed no myocarditis but revealed complement-mediated microvascular injury. Given multifactorial etiology of her RV failure, complement-mediated vasculitis was suspected to be a key driver of disease severity, therefore management prioritized aggressive immunosuppression. She was initiated on high-dose corticosteroids with subsequent pulse-dose methylprednisolone for ongoing inflammatory activity, followed by mycophenolate mofetil and rituximab for disease control. In parallel, PH therapy was carefully titrated rather than aggressively escalated. She was initially treated with phosphodiesterase-5 inhibition (sildenafil, later transitioned to tadalafil) and endothelin receptor antagonist therapy (ambrisentan), later discontinued due to volume overload. With improved cardiac output, dobutamine was weaned and selexipag initiated. Worsening digital ischemia prompted transition to IV treprostinil for microvascular disease, later de-escalated with resumption of selexipag. With control of the autoimmune flare, her RV function normalized and the patient recovered to NYHA Class I.
Discussion: This case highlights the complex interplay between inflammatory myocardial injury, microvascular dysfunction, and pulmonary vascular disease in SLE/MCTD. Discordance between modest pulmonary pressures and severe RV dysfunction, together with biopsy-proven complement-mediated microvascular injury, supported prioritization of immunosuppression with careful escalation of PAH therapy.
Conclusion: In SLE/MCTD, severe RV failure may reflect complement-mediated microvascular cardiomyopathy rather than fixed pulmonary vascular disease. Prioritizing early immunosuppression, alongside carefully tailored pulmonary vasodilator therapy, can lead to significant clinical and hemodynamic improvement.