Immune checkpoint inhibitor myocarditis with complete heart block: a case series
Authors: O'shea M , Arunachalam Karikalan S , Yusuf A , Nayak S , Masson R , Barry T , Shah S , El Masry H 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background/Introduction
Immune checkpoint inhibitor (ICI) myocarditis is a life-threatening condition characterized by lymphocytic myocardial infiltration[1]. Complete heart block (CHB) occurs in 15% of cases and is often fatal[2-4]. The nature and optimal management of this often-malignant condition is poorly understood[5].

Purpose
This case series assesses prognostic factors associated with survival at 90 days among people with ICI myocarditis and CHB.

Methods
The electronic patient record system was used to identify patients admitted with ICI myocarditis. A two-physician review was used to assess the presence of ICI-associated CHB. Wilcoxon rank sum and Spearman’s rank correlation were used for categorical and quantitative variables respectively. Data was analysed using STATA/IC 16.1. The primary outcome was person-day survival 90 days after presenting symptom onset.

Results
Six patients were included in the final analysis. Mean survival was 47 person days. All had metastatic disease and presented 15 to 32 days after the first ICI infusion. All had muscle weakness. Other common self-symptoms were shortness of breath (4), blurred vision (4), double vision (3), collapse (3), and leg swelling (1). Proximal myopathy (2), fatigable myopathy (1), ptosis (3), and peripheral oedema (1) were present on examination.
Raised troponin T and white blood cell count (WBC) were associated with 90-day survival (see Table 1). Nt-pro BNP, AST, and CK levels were raised in all patients. Two patients were tested for anti-striated muscle antibody titres, and both were strongly positive. Increase in QRS duration compared to baseline ECG was associated with lower survival at 90 days. Only one patient had CHB on admission.
Steroid dose, IVIG, and plasmapheresis weren’t associated with survival. One patient declined device therapy. One declined permanent pacemaker (PPM) after insertion of transvenous pacemaker (TVP). Both died within 2 weeks.
Three people underwent insertion of a transvenous pacemaker (TVP) followed by PPM insertion (table 2). All three eventually died within 100 days. One person received isoproterenol and immunosuppression as a bridge to PPM and survived. One patient was managed initially with TVP but subsequently declined PPM insertion. TVP removal resulted in CHB recurrence, and they died shortly after discharge. One person declined device therapy and died while receiving comfort care.
Lead malfunction was frequent. One patient experienced bradycardia arrest with failure of a TVP lead to capture, while another experienced lead dislodgement.

Conclusion
CHB secondary to ICI is often fatal. It should be considered in patients presenting with symptoms of myositis, raised troponin and increased QRS duration. Despite a small sample size, this study identifies several prognostic factors which can guide both patients and physicians with decision-making. Larger studies are needed to better understand the role of device therapy in this population.