Particulate Matter 2.5 Pollution Impact on Comorbid Cancer and Cardiovascular Disease Mortality in the U.S.

Background: Evidence regarding the effect of long-term exposure to particulate matter (PM) 2.5 and comorbid cancer and cardiovascular disease (CVD) mortality is limited. Objectives: In this study, the author report the association between long-term exposure to PM 2.5 and CVD mortality, cancer mortality and comorbid cancer and CVD mortality in the U.S. population. Methods: The Centers for Disease Control and Prevention (CDC) WONDER (Wide-Ranging Online Data for Epidemiologic Research) multiple-cause-of-death database was used to obtain U.S. county-level mortality and population estimates from 2016 to 2020. Data on average daily density of PM 2.5 were abstracted from the 2018 CDC's National Environmental Public Health Tracking system. Counties were divided into quartiles with Q1 representing counties with least average daily density and Q4 representing counties with maximum average daily density of PM 2.5. Age-adjusted mortality rates were abstracted for each quartile, for the overall population and subgroups of population. Results: The age-adjusted mortality rates for CVD, cancer, and comorbid cancer and CVD mortality were 505.3 (range: 505.0-505.7), 210.7 (range: 210.5-210.9), and 62.0 (range: 61.8-62.1) per 100,000 person-years, respectively. CVD mortality had the highest percentage excess mortality in Q4 compared with Q1, followed by comorbid cancer and CVD. Cancer had the least percentage excess mortality. A disproportionate effect of PM 2.5 exposure was noted on vulnerable and minority groups, based on Social Vulnerability Index and race stratification, respectively. Conclusions: Higher levels of long-term PM 2.5 exposure reported increased CVD mortality, cancer mortality and comorbid cancer and CVD disease mortality, with a pronounced detrimental effect in vulnerable and minority population.

Pre-existing cardiovascular disease is associated with an increased risk of cardiovascular events during Bruton tyrosine kinase inhibitor therapy.

The association between pre-existing cardiovascular disease (CVD) and the development of cardiovascular adverse events (CVAE) during Bruton tyrosine kinase inhibitor (BTKi) therapy is not well established. We compared the rate of CVAE, such as new onset or worsening atrial fibrillation (AF), supraventricular tachycardia, ventricular tachycardia, hypertension, myocardial infarction, and sudden cardiac death, between individuals with and without pre-existing CVD, during BTKi treatment. Secondary objectives were to compare the outcomes of patients treated with first generation BTKi versus second generation BTKi and characterize management decisions. A single-center retrospective review was conducted on patients treated with BTKi from 2013 to 2022 at Beth Israel Deaconess Medical Center. Adjusted logistic regression analyses were performed to evaluate the association between pre-existing CVD and CVAE. In this cohort, 11 out of 54 patients (20.4%) with pre-existing CVD developed CVAE, compared to 11 out of 135 patients (8.1%) without pre-existing CVD [age- and sex-adjusted OR 2.79; 95% CI (1.09, 7.25), P = .03]. Patients with pre-existing CVD had higher odds of developing new or worsening AF [age- and sex-adjusted OR 3.36; 95% CI (1.09, 10.71), P = .03]. Results remained robust after further adjustment of comorbidities, type of BTKi, and baseline medications. These results highlight the need for standardized approaches to prevent and promptly detect CVAE during BTKi treatment, particularly in patients with pre-existing CVD.

Cytotoxic T cells drive doxorubicin-induced cardiac fibrosis and systolic dysfunction.

Doxorubicin, the most prescribed chemotherapeutic drug, causes dose-dependent cardiotoxicity and heart failure. However, our understanding of the immune response elicited by doxorubicin is limited. Here we show that an aberrant CD8+ T cell immune response following doxorubicin-induced cardiac injury drives adverse remodeling and cardiomyopathy. Doxorubicin treatment in non-tumor-bearing mice increased circulating and cardiac IFNγ+CD8+ T cells and activated effector CD8+ T cells in lymphoid tissues. Moreover, doxorubicin promoted cardiac CD8+ T cell infiltration and depletion of CD8+ T cells in doxorubicin-treated mice decreased cardiac fibrosis and improved systolic function. Doxorubicin treatment induced ICAM-1 expression by cardiac fibroblasts resulting in enhanced CD8+ T cell adhesion and transformation, contact-dependent CD8+ degranulation and release of granzyme B. Canine lymphoma patients and human patients with hematopoietic malignancies showed increased circulating CD8+ T cells after doxorubicin treatment. In human cancer patients, T cells expressed IFNγ and CXCR3, and plasma levels of the CXCR3 ligands CXCL9 and CXCL10 correlated with decreased systolic function.

Predictors and Risk Score for Immune Checkpoint-Inhibitor-Associated Myocarditis Severity.

Background: Immune-checkpoint inhibitors (ICI) are associated with life-threatening myocarditis but milder presentations are increasingly recognized. The same autoimmune process that causes ICI-myocarditis can manifest concurrent generalized myositis, myasthenia-like syndrome, and respiratory muscle failure. Prognostic factors for this "cardiomyotoxicity" are lacking. Methods: A multicenter registry collected data retrospectively from 17 countries between 2014-2023. A multivariable cox regression model (hazard-ratio(HR), [95%confidence-interval]) was used to determine risk factors for the primary composite outcome: severe arrhythmia, heart failure, respiratory muscle failure, and/or cardiomyotoxicity-related death. Covariates included demographics, comorbidities, cardio-muscular symptoms, diagnostics, and treatments. Time-dependent covariates were used and missing data were imputed. A point-based prognostic risk score was derived and externally validated. Results: In 748 patients (67% male, age 23-94), 30-days incidence of the primary composite outcome, cardiomyotoxic death, and overall death were 33%, 13%, and 17% respectively. By multivariable analysis, the primary composite outcome was associated with active thymoma (HR=3.60[1.93-6.72]), presence of cardio-muscular symptoms (HR=2.60 [1.58-4.28]), low QRS-voltage on presenting electrocardiogram (HR for ≤0.5mV versus >1mV=2.08[1.31-3.30]), left ventricular ejection fraction (LVEF) <50% (HR=1.78[1.22-2.60]), and incremental troponin elevation (HR=1.86 [1.44-2.39], 2.99[1.91-4.65], 4.80[2.54-9.08], for 20, 200 and 2000-fold above upper reference limit, respectively). A prognostic risk score developed using these parameters showed good performance; 30-days primary outcome incidence increased gradually from 3.9%(risk-score=0) to 81.3%(risk-score≥4). This risk-score was externally validated in two independent French and US cohorts. This risk score was used prospectively in the external French cohort to identify low risk patients who were managed with no immunosuppression resulting in no cardio-myotoxic events. Conclusions: ICI-myocarditis can manifest with high morbidity and mortality. Myocarditis severity is associated with magnitude of troponin, thymoma, low-QRS voltage, depressed LVEF, and cardio-muscular symptoms. A risk-score incorporating these features performed well. Trial registration number: NCT04294771 and NCT05454527.

Renal Biomarkers in Heart Failure: Systematic Review and Meta-Analysis.

Background: Cystatin C, neutrophil gelatinase-associated lipocalin (NGAL), and kidney injury molecule (KIM)-1 are renal biomarkers increasingly appreciated for their role in the risk stratification and prognostication of heart failure (HF) patients. However, very few have been adopted clinically, owing to the lack of consistency. Objectives: The authors aimed to study the association between cystatin C, NGAL, and KIM-1 and outcomes, mortality, hospitalizations, and worsening renal function (WRF) in patients with acute and chronic HF. Methods: We included peer-reviewed English-language articles from PubMed and EMBASE published up to December 2021. We analyzed the above associations using random-effects meta-analysis. Publication bias was assessed using funnel plots. Results: Among 2,631 articles, 100 articles, including 45,428 patients, met the inclusion criteria. Top-tertile of serum cystatin C, when compared to the bottom-tertile, carried a higher pooled hazard ratio (pHR) for mortality (pHR: 1.59, 95% CI: 1.42-1.77) and for the composite outcome of mortality and HF hospitalizations (pHR: 1.49, 95% CI: 1.23-1.75). Top-tertile of serum NGAL had a higher hazard for mortality (pHR: 2.91, 95% CI: 1.49-5.67) and composite outcome (HR: 4.11, 95% CI: 2.69-6.30). Serum and urine NGAL were significantly associated with WRF, with pHRs of 2.40 (95% CI: 1.48-3.90) and 2.01 (95% CI: 1.21-3.35). Urine KIM-1 was significantly associated with WRF (pHR: 1.60, 95% CI: 1.24-2.07) but not with other outcomes. High heterogeneity was noted between studies without an obvious explanation based on meta-regression. Conclusions: Serum cystatin C and serum NGAL are independent predictors of adverse outcomes in HF. Serum and urine NGAL are important predictors of WRF in HF.

Inhibition of Cyp1a Protects Mice against Anthracycline Cardiomyopathy.

Background: Anthracyclines such as doxorubicin (Dox) are highly effective anti-tumor agents, but their use is limited by dose-dependent cardiomyopathy and heart failure. Our laboratory previously reported that induction of cytochrome P450 family 1 (Cyp1) enzymes contributes to acute Dox cardiotoxicity in zebrafish and in mice, and that potent Cyp1 inhibitors prevent cardiotoxicity. However, the role of Cyp1 enzymes in chronic Dox cardiomyopathy, as well as the mechanisms underlying cardioprotection associated with Cyp1 inhibition, have not been fully elucidated. Methods: The Cyp1 pathway was evaluated using a small molecule Cyp1 inhibitor in wild-type (WT) mice, or Cyp1-null mice ( Cyp1a1/1a2 -/- , Cyp1b1 -/- , and Cyp1a1/1a2/1b1 -/- ). Low-dose Dox was administered by serial intraperitoneal or intravenous injections, respectively. Expression of Cyp1 isoforms was measured by RT-qPCR, and myocardial tissue was isolated from the left ventricle for RNA sequencing. Cardiac function was evaluated by transthoracic echocardiography. Results: In WT mice, Dox treatment was associated with a decrease in Cyp1a2 and increase in Cyp1b1 expression in the heart and in the liver. Co-treatment of WT mice with Dox and the novel Cyp1 inhibitor YW-130 protected against cardiac dysfunction compared to Dox treatment alone. Cyp1a1/1a2 -/- and Cyp1a1/1a2/1b1 -/- mice were protected from Dox cardiomyopathy compared to WT mice. Male, but not female, Cyp1b1 -/- mice had increased cardiac dysfunction following Dox treatment compared to WT mice. RNA sequencing of myocardial tissue showed upregulation of Fundc1 and downregulation of Ccl21c in Cyp1a1/1a2 -/- mice treated with Dox, implicating changes in mitophagy and chemokine-mediated inflammation as possible mechanisms of Cyp1a-mediated cardioprotection. Conclusions: Taken together, this study highlights the potential therapeutic value of Cyp1a inhibition in mitigating anthracycline cardiomyopathy.

Sex Differences in the Development of Anthracycline-Associated Heart Failure.

BACKGROUND: Female sex is frequently cited as a risk factor for anthracycline cardiotoxicity based on pediatric data, but the role of sex in the development of cardiotoxicity has not been clearly established in adults. OBJECTIVES: To assess the effect of female sex on the development of incident heart failure (HF) in adult patients treated with anthracyclines. METHODS: This was a retrospective cohort study of 1525 adult patients with no prior history of HF or cardiomyopathy who were treated with anthracyclines between 1992 and 2019. The primary outcome was new HF within 5 years of the first dose of anthracyclines. The effect of sex was assessed using Cox proportional hazards and competing risk models. RESULTS: Over a median (IQR) follow-up of 1.02 (0.30-3.01) years, 4.78% of patients developed HF (44 men and 29 women). Female sex was not associated with the primary outcome in a multivariable Cox proportional hazards model (HR 0.87; 95% CI 0.53-1.43; P = 0.58). Similar results were observed in a multivariable model accounting for the competing risk of death (HR 0.94; 95% CI 0.39-2.25; P = 0.88). Age, coronary artery disease and hematopoietic stem cell transplant were associated with the primary outcome in a multivariable Cox proportional hazards model. Age and body mass index were associated with the primary outcome in a multivariable competing risk model. CONCLUSIONS: In this large, single-center, retrospective cohort study, female sex was not associated with incident HF in adult patients treated with anthracyclines. CONDENSED ABSTRACT: Female sex is frequently cited as a risk factor for anthracycline cardiotoxicity based on pediatric data, but the role of sex in the development of cardiotoxicity has not been clearly established in adults. In this retrospective cohort study, we assessed the effect of female sex on the development of incident heart failure in adult patients treated with anthracyclines. Using Cox proportional hazards and competing risk regression models, we found that there was no association between female sex and heart failure after treatment with anthracyclines.

Atorvastatin for Anthracycline-Associated Cardiac Dysfunction: The STOP-CA Randomized Clinical Trial.

Importance: Anthracyclines treat a broad range of cancers. Basic and retrospective clinical data have suggested that use of atorvastatin may be associated with a reduction in cardiac dysfunction due to anthracycline use. Objective: To test whether atorvastatin is associated with a reduction in the proportion of patients with lymphoma receiving anthracyclines who develop cardiac dysfunction. Design, Setting, and Participants: Double-blind randomized clinical trial conducted at 9 academic medical centers in the US and Canada among 300 patients with lymphoma who were scheduled to receive anthracycline-based chemotherapy. Enrollment occurred between January 25, 2017, and September 10, 2021, with final follow-up on October 10, 2022. Interventions: Participants were randomized to receive atorvastatin, 40 mg/d (n = 150), or placebo (n = 150) for 12 months. Main Outcomes and Measures: The primary outcome was the proportion of participants with an absolute decline in left ventricular ejection fraction (LVEF) of ≥10% from prior to chemotherapy to a final value of <55% over 12 months. A secondary outcome was the proportion of participants with an absolute decline in LVEF of ≥5% from prior to chemotherapy to a final value of <55% over 12 months. Results: Of the 300 participants randomized (mean age, 50 [SD, 17] years; 142 women [47%]), 286 (95%) completed the trial. Among the entire cohort, the baseline mean LVEF was 63% (SD, 4.6%) and the follow-up LVEF was 58% (SD, 5.7%). Study drug adherence was noted in 91% of participants. At 12-month follow-up, 46 (15%) had a decline in LVEF of 10% or greater from prior to chemotherapy to a final value of less than 55%. The incidence of the primary end point was 9% (13/150) in the atorvastatin group and 22% (33/150) in the placebo group (P = .002). The odds of a 10% or greater decline in LVEF to a final value of less than 55% after anthracycline treatment was almost 3 times greater for participants randomized to placebo compared with those randomized to atorvastatin (odds ratio, 2.9; 95% CI, 1.4-6.4). Compared with placebo, atorvastatin also reduced the incidence of the secondary end point (13% vs 29%; P = .001). There were 13 adjudicated heart failure events (4%) over 24 months of follow-up. There was no difference in the rates of incident heart failure between study groups (3% with atorvastatin, 6% with placebo; P = .26). The number of serious related adverse events was low and similar between groups. Conclusions and Relevance: Among patients with lymphoma treated with anthracycline-based chemotherapy, atorvastatin reduced the incidence of cardiac dysfunction. This finding may support the use of atorvastatin in patients with lymphoma at high risk of cardiac dysfunction due to anthracycline use. Trial Registration: ClinicalTrials.gov Identifier: NCT02943590.

Efficacy and safety of catheter ablation for atrial fibrillation in patients with history of cancer.

BACKGROUND: Though the incidence of atrial fibrillation (AF) is increased in patients with cancer, the effectiveness of catheter ablation (CA) for AF in patients with cancer is not well studied. METHODS: We conducted a retrospective cohort study of patients who underwent CA for AF. Patients with a history of cancer within 5-years prior to, or those with an exposure to anthracyclines and/or thoracic radiation at any time prior to the index ablation were compared to patients without a history of cancer who underwent AF ablation. The primary outcome was freedom from AF [with or without anti-arrhythmic drugs (AADs), or need for repeat CA at 12-months post-ablation]. Secondary endpoints included freedom from AF at 12 months post-ablation with AADs and without AADs. Safety endpoints included bleeding, pulmonary vein stenosis, stroke, and cardiac tamponade. Multivariable regression analysis was performed to identify independent risk predictors of the primary outcome. RESULTS: Among 502 patients included in the study, 251 (50%) had a history of cancer. Freedom from AF at 12 months did not differ between patients with and without cancer (83.3% vs 72.5%, p 0.28). The need for repeat ablation was also similar between groups (20.7% vs 27.5%, p 0.29). Multivariable regression analysis did not identify a history of cancer or cancer-related therapy as independent predictors of recurrent AF after ablation. There was no difference in safety endpoints between groups. CONCLUSION: CA is a safe and effective treatment for AF in patients with a history of cancer and those with exposure to potentially cardiotoxic therapy.

The Spatial Ventricular Gradient Is an Independent Predictor of Anthracycline-Associated Cardiotoxicity.

Background: Anthracyclines are effective chemotherapies that are limited by cardiotoxicity. The spatial ventricular gradient (SVG) is a marker of electrical heterogeneity linked to adverse cardiovascular outcomes, including sudden cardiac death and heart failure (HF). Objectives: The purpose of this study was to assess if SVG values before chemotherapy are associated with the risk of anthracycline-associated HF or cardiomyopathy (CM). Methods: We analyzed 12-lead electrocardiograms obtained within 6 months before initiation of anthracyclines in a retrospective cohort treated for cancer between 1992 and 2019 at a single academic medical center. Incident HF and CM were defined by ICD-9/10 codes and confirmed by chart review. Vectorcardiograms were constructed from baseline electrocardiograms, and the SVG was calculated. The cumulative incidence of anthracycline-associated HF or CM was regressed on SVG vector orientation and magnitude with death as a competing risk. Results: In 889 patients (47% male; mean age 58 ± 16 years; 71% hematologic malignancies), larger SVG magnitude prechemotherapy was associated with decreased risk of HF or CM after multivariable adjustment, with a subhazard ratio of 0.76 per 1 SD increase (95% CI: 0.59-0.96; P = 0.024). SVG vector orientation, specifically a more leftward oriented VGx, was associated with decreased risk of HF or CM with a subhazard ratio of 0.77 per 1 SD increase (95% CI: 0.61-0.96; P = 0.023). Conclusions: Larger SVG magnitude and more leftward SVG orientation were associated with a decreased risk of anthracycline cardiotoxicity in a large retrospective cohort. Improved cardiac risk stratification algorithms incorporating the SVG could personalize both cancer and cardioprotective therapy.

Priorities in Cardio-Oncology Basic and Translational Science: GCOS 2023 Symposium Proceedings: JACC: CardioOncology State-of-the-Art Review.

Despite improvements in cancer survival, cancer therapy-related cardiovascular toxicity has risen to become a prominent clinical challenge. This has led to the growth of the burgeoning field of cardio-oncology, which aims to advance the cardiovascular health of cancer patients and survivors, through actionable and translatable science. In these Global Cardio-Oncology Symposium 2023 scientific symposium proceedings, we present a focused review on the mechanisms that contribute to common cardiovascular toxicities discussed at this meeting, the ongoing international collaborative efforts to improve patient outcomes, and the bidirectional challenges of translating basic research to clinical care. We acknowledge that there are many additional therapies that are of significance but were not topics of discussion at this symposium. We hope that through this symposium-based review we can highlight the knowledge gaps and clinical priorities to inform the design of future studies that aim to prevent and mitigate cardiovascular disease in cancer patients and survivors.

Circulating hemopexin modulates anthracycline cardiac toxicity in patients and in mice.

Anthracyclines such as doxorubicin (Dox) are effective chemotherapies, but their use is limited by cardiac toxicity. We hypothesized that plasma proteomics in women with breast cancer could identify new mechanisms of anthracycline cardiac toxicity. We measured changes in 1317 proteins in anthracycline-treated patients (n = 30) and replicated key findings in a second cohort (n = 31). An increase in the heme-binding protein hemopexin (Hpx) 3 months after anthracycline initiation was associated with cardiac toxicity by echocardiography. To assess the functional role of Hpx, we administered Hpx to wild-type (WT) mice treated with Dox and observed improved cardiac function. Conversely, Hpx-/- mice demonstrated increased Dox cardiac toxicity compared to WT mice. Initial mechanistic studies indicate that Hpx is likely transported to the heart by circulating monocytes/macrophages and that Hpx may mitigate Dox-induced ferroptosis to confer cardioprotection. Together, these observations suggest that Hpx induction represents a compensatory response during Dox treatment.

Impact of Social Vulnerability on Comorbid Cancer and Cardiovascular Disease Mortality in the United States.

Background: Racial and social disparities exist in outcomes related to cancer and cardiovascular disease (CVD). Objectives: The aim of this cross-sectional study was to study the impact of social vulnerability on mortality attributed to comorbid cancer and CVD. Methods: The Centers for Disease Control and Prevention Wide-Ranging Online Data for Epidemiologic Research database (2015-2019) was used to obtain county-level mortality data attributed to cancer, CVD, and comorbid cancer and CVD. County-level social vulnerability index (SVI) data (2014-2018) were obtained from the CDC's Agency for Toxic Substances and Disease Registry. SVI percentiles were generated for each county and aggregated to form SVI quartiles. Age-adjusted mortality rates (AAMRs) were estimated and compared across SVI quartiles to assess the impact of social vulnerability on mortality related to cancer, CVD, and comorbid cancer and CVD. Results: The AAMR for comorbid cancer and CVD was 47.75 (95% CI: 47.66-47.85) per 100,000 person-years, with higher mortality in counties with greater social vulnerability. AAMRs for cancer and CVD were also significantly greater in counties with the highest SVIs. However, the proportional increase in mortality between the highest and lowest SVI counties was greater for comorbid cancer and CVD than for either cancer or CVD alone. Adults <45 years of age, women, Asian and Pacific Islanders, and Hispanics had the highest relative increase in comorbid cancer and CVD mortality between the fourth and first SVI quartiles, without significant urban-rural differences. Conclusions: Comorbid cancer and CVD mortality increased in counties with higher social vulnerability. Improved education, resource allocation, and targeted public health interventions are needed to address inequities in cardio-oncology.

Understanding Myocardial Metabolism in the Context of Cardio-Oncology.

Cardiovascular events, ranging from arrhythmias to decompensated heart failure, are common during and after cancer therapy. Cardiovascular complications can be life-threatening, and from the oncologist's perspective, could limit the use of first-line cancer therapeutics. Moreover, an aging population increases the risk for comorbidities and medical complexity among patients who undergo cancer therapy. Many have established cardiovascular diagnoses or risk factors before starting these therapies. Therefore, it is essential to understand the molecular mechanisms that drive cardiovascular events in patients with cancer and to identify new therapeutic targets that may prevent and treat these 2 diseases. This review will discuss the metabolic interaction between cancer and the heart and will highlight current strategies of targeting metabolic pathways for cancer treatment. Finally, this review highlights opportunities and challenges in advancing our understanding of myocardial metabolism in the context of cancer and cancer treatment.

Genetics of Anthracycline-Associated Cardiotoxicity.

Anthracyclines are a major component of chemotherapies used in many pediatric and adult malignancies. Anthracycline-associated cardiotoxicity (ACT) is a dose-dependent adverse effect that has substantial impact on morbidity and mortality. Therefore, the identification of genetic variants associated with increased risk of ACT has the potential for significant clinical impact to improve patient care. The goal of this review is to summarize the current evidence supporting genetic variants associated with ACT, identify gaps and limitations in current knowledge, and propose future directions for incorporating genetics into clinical practice for patients treated with anthracyclines. We will discuss mechanisms of ACT that could be illuminated by genetics and discuss clinical applications for the cardiologist/cardio-oncologist.

Association of early electrical changes with cardiovascular outcomes in immune checkpoint inhibitor myocarditis.

BACKGROUND: Immune-checkpoint inhibitor-associated myocarditis (ICI-myocarditis) often presents with arrhythmias, but the prognostic value of early electrocardiogram findings is unclear. Although ICI-myocarditis and acute cellular rejection (ACR) following cardiac transplantation use similar treatment strategies, differences in arrhythmia burden are unknown. OBJECTIVE: To evaluate the association of electrocardiogram findings in ICI-myocarditis with myocarditis-related mortality and life-threatening arrhythmia. METHODS: A total of 125 cases of ICI-myocarditis were identified retrospectively across 49 hospitals worldwide; 50 cases of grade 2R or 3R ACR were included as comparators. Two cardiologists blinded to clinical data interpreted electrocardiograms. Associations between electrocardiogram features, myocarditis-related mortality and the composite of myocarditis-related mortality and life-threatening arrhythmias were examined. Adjusted hazard ratios (aHRs) were calculated. RESULTS: The cohort had 78 (62.4%) men; median (interquartile range) age was 67 (58-76) years. At 30 days, myocarditis-related mortality was 20/124 (16.1%), and 28/124 (22.6%) met the composite endpoint. Patients who developed complete heart block (aHR by subdistribution hazards model [aHR(sh)] 3.29, 95% confidence interval [CI] 1.24-8.68; P=0.02) or life-threatening cardiac arrhythmias (aHR(sh) 6.82, 95% CI: 2.87-16.21; P<0.001) had a higher risk of myocarditis-related mortality. Pathological Q waves (aHR(sh) 3.40, 95% CI: 1.38-8.33; P=0.008), low QRS voltage (aHR(sh) 6.05, 95% CI: 2.10-17.39; P<0.001) and Sokolow-Lyon index (aHR(sh)/mV 0.54, 95% CI: 0.30-0.97; P=0.04) on admission electrocardiogram were also associated with increased risk of myocarditis-related mortality. These associations were mirrored in the composite outcome analysis. Compared with ACR, ICI-myocarditis had a higher incidence of life-threatening cardiac arrhythmias (15/125 [12.0%] vs 1/50 [2%]; P=0.04) and third-degree heart block (19/125 [15.2%] vs 0/50 [0%]; P=0.004). CONCLUSIONS: Electrocardiograms in ICI-myocarditis with ventricular tachycardias, heart block, low-voltage and pathological Q waves were associated with myocarditis-related mortality and life-threating arrhythmia. Arrhythmia burden in ICI-myocarditis exceeds that of ACR after heart transplant.