Cancer Radiation Therapy May Be Associated With Atrial Fibrillation

Arrhythmia Challenges in Cardio-Oncology: High-Risk Therapies, Management, and Anticoagulation

Cardiovascular disease and cancer are the leading cause of mortality in the United States. In 2021, there were 695,547 and 605,213 deaths due to heart disease and cancer, respectively. With novel oncologic and cardiac therapies, survival has improved leading to increased life-expectancy albeit with chronic illness burden. Arrhythmia management in patients with cancer, whether active or in remission, can be quite challenging. In this review, we will discuss high-risk oncological therapies, prevention, and management of Atrial fibrillation, Ventricular Arrhythmias, and Bradyarrhythmias.

Atrial fibrillation in cancer, anticancer therapies, and underlying mechanisms

Atrial fibrillation (AF) is a common arrhythmic complication in cancer patients and can be exacerbated by traditional cytotoxic and targeted anticancer therapies. Increased incidence of AF in cancer patients is independent of confounding factors, including preexisting myocardial arrhythmogenic substrates, type of cancer, or cancer stage. Mechanistically, AF is characterized by fast unsynchronized atrial contractions with rapid ventricular response, which impairs ventricular filling and results in various symptoms such as fatigue, chest pain, and shortness of breath. Due to increased blood stasis, a consequence of both cancer and AF, concern for stroke increases in this patient population. To compound matters, cardiotoxic anticancer therapies themselves promote AF; thereby exacerbating AF morbidity and mortality in cancer patients. In this review, we examine the relationship between AF, cancer, and cardiotoxic anticancer therapies with a focus on the shared molecular and electrophysiological mechanisms linking these disease processes. We also explore the potential role of sodium-glucose co-transporter 2 inhibitors (SGLT2i) in the management of anticancer-therapy-induced AF.

Radon Exposure and Incident Stroke Risk in the Women's Health Initiative

BACKGROUND AND OBJECTIVES

Little is known about the role of radon in the epidemiology of stroke among women. We therefore examined the association between home radon exposure and risk of stroke among middle-aged and older women in the United States.

METHODS

We conducted a prospective cohort study of postmenopausal women aged 50-79 years at baseline (1993-1998) in the Women's Health Initiative. We measured exposures as 2-day, indoor, lowest living-level average radon concentrations in picocuries per liter (pCi/L) as estimated in 1993 by the US Geological Survey and reviewed by the Association of American State Geologists under the Indoor Radon Abatement Act. We used Cox proportional hazards models to estimate risk of incident, neurologist-adjudicated stroke during follow-up through 2020 as a hazard ratio and 95% CI, adjusting for study design and participant demographic, social, behavioral, and clinical characteristics.

RESULTS

Among 158,910 women without stroke at baseline (mean age 63.2 years; 83% white), 6,979 incident strokes were identified over follow-up (mean 13.4 years). Incidence rates were 333, 343, and 349 strokes per 100,000 woman-years at radon concentrations of <2, 2-4, and >4 pCi/L, respectively. Compared with women living at concentrations <2 pCi/L, those at 2-4 and >4 pCi/L had higher covariate-adjusted risks of incident stroke: hazard ratio (95% CI) 1.06 (0.99-1.13) and 1.14 (1.05-1.22). Using nonlinear spline functions to model radon, stroke risk was significantly elevated at concentrations ranging from 2 to 4 pCi/L (p = 0.0004), that is, below the United States Environmental Protection Agency Radon Action Level for mitigation (4 pCi/L). Associations were slightly stronger for ischemic (especially cardioembolic, small vessel occlusive, and large artery atherosclerotic) than hemorrhagic stroke, but otherwise robust in sensitivity analyses.

DISCUSSION

Radon exposure is associated with moderately increased stroke risk among middle-aged and older women in the United States, suggesting that promulgation of a lower Radon Action Level may help reduce the domestic impact of cerebrovascular disease on public health.

Patterns of Anticoagulation Use and All-Cause of Mortality in Cancer Patients with Atrial Fibrillation

BACKGROUND

There is uncertainty regarding the clinical benefit of anticoagulant (AC) treatment in patients with cancer with atrial fibrillation (AF). We aimed to evaluate the distribution and patterns of AC use and its impact on all-cause mortality in cancer patients with AF.

METHODS

A total of 1,653 patients with cancer diagnosed with AF were included in this retrospective cohort analysis. Multivariable logistic regression was applied to identify the clinical predictors of anticoagulant prescription. Kaplan-Meier curve with a log-rank test was used to compare the probability of survival between the AC and non-AC groups. Multivariate Cox proportional hazard regression models were implemented to evaluate the influences of various variables on all-cause death.

RESULTS

Of 1,653 patients with cancer with AF, 971 (58.7%) did not receive a prescription for AC. Among patients with CHA2DS2-VASC ≥2 in men or ≥3 in women and HAS-BLED <3, 56.5% were not prescribed AC. Rivaroxaban and warfarin are more frequently used than dabigatran, mainly in patients with lung and breast cancer. Over a median follow-up of 36 months, 776 deaths were identified. The Kaplan-Meier curve suggested that patients with AC prescriptions had better clinical outcomes. On multivariate Cox proportional risk regression analysis, AC prescription was significantly associated with a lower risk of all-cause mortality (hazard ratio, 0.78; 95% confidence interval, 0.66-0.91; P = 0.002).

CONCLUSIONS

The prescription of anticoagulants in patients with cancer with AF was suboptimal. AC prescription at discharge was associated with a decreased risk of all-cause mortality.

IMPACT

This study highlights the importance of AC prescriptions in patients with cancer with AF.

A Meta-Analysis and Review of Radiation Dose Escalation in Definitive Radiation Therapy between Squamous Cell Carcinoma and Adenocarcinoma of Esophageal Cancer

Esophageal cancer, ranked as the eighth most prevalent cancer globally, is characterized by a low survival rate and poor prognosis. Concurrent chemoradiation therapy (CCRT) is the standard therapy in the non-surgical treatment of localized carcinoma of the esophagus. Nevertheless, the radiation doses employed in CCRT remain notably lower compared to the curative definite chemoradiation therapy utilized in the management of other carcinomas. In order to increase the local control rates and enhance the treatment outcomes, several clinical trials have used high-dose radiation to analyze the effect of dose escalation. Despite the integration of technically advanced RT schemes such as intensity-modulated radiation therapy (IMRT), the results of these trials have failed to demonstrate a significant improvement in overall survival or local progression-free survival. In this review, we investigated previous clinical trials to determine the ineffectiveness of radiation dose escalation in the context of CCRT for esophageal cancer. We aim to clarify the factors contributing to the limited efficacy of escalated radiation doses in improving patient outcomes. Furthermore, we delve into recent research endeavors, exploring prospective radiation dose modifications being altered based on the histological characteristics of the carcinoma. The exploration of these recent studies not only sheds light on potential refinements to the existing treatment protocols but also seeks to identify novel approaches that may pave the way for more efficacious and personalized therapeutic strategies for esophageal cancer management.

Radon Exposure, Clonal Hematopoiesis, and Stroke Susceptibility in the Women's Health Initiative

BACKGROUND AND OBJECTIVES

Studies suggest that clonal hematopoiesis of indeterminate potential (CHIP) may increase risk of hematologic malignancy and cardiovascular disease, including stroke. However, few studies have investigated plausible environmental risk factors for CHIP such as radon, despite the climate-related increases in and documented infrequency of testing for this common indoor air pollutant.The purpose of this study was to estimate the risk of CHIP related to radon, an established environmental mutagen.

METHODS

We linked geocoded addresses of 10,799 Women's Health Initiative Trans-Omics for Precision Medicine (WHI TOPMed) participants to US Environmental Protection Agency-predicted, county-level, indoor average screening radon concentrations, categorized as follows: Zone 1 (>4 pCi/L), Zone 2 (2-4 pCi/L), and Zone 3 (<2 pCi/L). We defined CHIP as the presence of one or more leukemogenic driver mutations with variant allele frequency >0.02. We identified prevalent and incident ischemic and hemorrhagic strokes; subtyped ischemic stroke using Trial of ORG 10172 in Acute Stroke Treatment (TOAST) criteria; and then estimated radon-related risk of CHIP as an odds ratio (OR) and 95% CI using multivariable-adjusted, design-weighted logistic regression stratified by age, race/ethnicity, smoking status, and stroke type/subtype.

RESULTS

The percentages of participants with CHIP in Zones 1, 2, and 3 were 9.0%, 8.4%, and 7.7%, respectively (ptrend = 0.06). Among participants with ischemic stroke, Zones 2 and 1 were associated with higher estimated risks of CHIP relative to Zone 3: 1.39 (1.15-1.68) and 1.46 (1.15-1.87), but not among participants with hemorrhagic stroke: 0.98 (0.68-1.40) and 1.03 (0.70-1.52), or without stroke: 1.04 (0.74-1.46) and 0.95 (0.63-1.42), respectively (pinteraction = 0.03). Corresponding estimates were particularly high among TOAST-subtyped cardioembolism: 1.78 (1.30-2.47) and 1.88 (1.31-2.72), or other ischemic etiologies: 1.37 (1.06-1.78) and 1.50 (1.11-2.04), but not small vessel occlusion: 1.05 (0.74-1.49) and 1.00 (0.68-1.47), respectively (pinteraction = 0.10). Observed patterns of association among strata were insensitive to attrition weighting, ancestry adjustment, prevalent stroke exclusion, separate analysis of DNMT3A driver mutations, and substitution with 3 alternative estimates of radon exposure.

DISCUSSION

The robust elevation of radon-related risk of CHIP among postmenopausal women who develop incident cardioembolic stroke is consistent with a potential role of somatic genomic mutation in this societally burdensome form of cerebrovascular disease, although the mechanism has yet to be confirmed.

Safety and efficacy of catheter ablation for atrial fibrillation in cancer survivors: a systematic review and meta-analysis

BACKGROUND

Cancer survivors are at increased risk for atrial fibrillation (AF). However, data on the efficacy and safety of catheter ablation (CA) in this population remain limited. Therefore, we aimed to perform a systematic review and meta-analysis comparing outcomes after CA for AF in patients with versus without prior or active cancer.

METHODS

We systematically searched PubMed, Cochrane Library, and Embase from inception to April 2023 for studies comparing the safety and efficacy of CA for AF in cancer survivors. Outcomes of interest were bleeding events, late AF recurrence, and need for repeat ablation. Statistical analyses were performed using Review Manager 5.4.1. We pooled odds ratios (OR) with 95% confidence intervals (CI) for binary endpoints.

RESULTS

We included 5 retrospective cohort studies comprising 998 patients, of whom 41.4% had a history of cancer. Cancer survivors were at significantly higher risk of clinically relevant bleeding (OR 2.17; 95% CI 1.17-4.0; p=0.01) as compared with those without cancer. The efficacy of CA for AF was similar between groups. Late AF recurrence at 12 months was not significantly different between patients with vs. without a history of cancer (OR 1.29; 95% CI 0.78-2.13; p=0.32). Similar findings were observed in the outcome of repeat ablations (OR 0.71; 95% CI 0.37-1.37; p=0.31).

CONCLUSIONS

These findings suggest that cancer survivors have an increased risk of bleeding after CA for AF relative to patients without cancer, with no significant difference in the efficacy of CA for maintenance of sinus rhythm between groups.

STUDY REGISTRATION

This systematic review is registered in the International Prospective Register of Systematic Reviews (PROSPERO) under registration number CRD42023394538.

Incident Atrial Fibrillation and Survival Outcomes in Esophageal Cancer following Radiotherapy

PURPOSE

Radiation therapy (RT) associates with long-term cardiotoxicity. In preclinical models, RT exposure induces early cardiotoxic arrhythmias including atrial fibrillation (AF). Yet, whether this occurs in patients is unknown.

METHODS AND MATERIALS

Leveraging a large cohort of consecutive patients with esophageal cancer treated with thoracic RT from 2007 to 2019, we assessed incidence and outcomes of incident AF. Secondary outcomes included major adverse cardiovascular events (MACE), defined as AF, heart failure, ventricular arrhythmias, and sudden death, by cardiac RT dose. We also assessed the relationship between AF development and progression-free and overall survival. Observed incident AF rates were compared with Framingham predicted rates, and absolute excess risks were estimated. Multivariate regression was used to define the relationship between clinical and RT measures, and outcomes. Differences in outcomes, by AF status, were also evaluated via 30-day landmark analysis. Furthermore, we assessed the effect of cardiac substructure RT dose (eg, left atrium, LA) on the risk of post RT-related outcomes.

RESULTS

Overall, from 238 RT treated patients with esophageal cancer, 21.4% developed incident AF, and 33% developed MACE with the majority (84%) of events occurring ≤2 years of RT initiation (median time to AF, 4.1 months). Cumulative incidence of AF and MACE at 1 year was 19.5%, and 25.7%, respectively; translating into an observed incident AF rate of 824 per 10,000 person-years, compared with the Framingham predicted rate of 92 (relative risk, 8.96; P < .001, absolute excess risk 732). Increasing LA dose strongly associated with incident AF (P = .001); and those with AF saw worse disease progression (hazard ratio, 1.54; P = .03). In multivariate models, outside of traditional cancer-related factors, increasing RT dose to the LA remained associated with worse overall survival.

CONCLUSIONS

Among patients with esophageal cancer, radiation therapy increases AF risk, and associates with worse long-term outcomes.

Outcome of cancer patients after atrial fibrillation ablation: Insights from the China-AF registry

BACKGROUND

Cancer has become significant comorbidity in patients with atrial fibrillation (AF). However, little is known about the efficacy and safety of AF ablation, the first-line rhythm control strategy, in patients with cancer. This study aims to evaluate the incidence and risk of AF recurrence and safety endpoints in patients with cancer compared to the non-cancer group after ablation.

METHODS

From August 2011 to December 2020, we consecutively enrolled cancer patients in the China-AF cohort. We used propensity score matching (1:3) to select the control group and assessed the risk of AF recurrence and adverse events after ablation in cancer patients using a multivariable Fine and Gray competing risk model.

RESULTS

A total of 203 patients with cancer were enrolled and 21 of them were active cancer, with a median follow-up of 12.3 months. The cumulative incidence of AF recurrence was comparable between patients with and without cancer (43.8% vs. 51.1%; p = .88). No difference in the risk of AF recurrence, thromboembolism, major bleeding, and mortality was observed after adjusting confounders. Active cancer was not associated with an increased risk of AF recurrence compared to the stable disease (SHR = 1.32; 95% CI 0.72-2.43; p = .46). Cancer was associated with a low risk of cardiovascular hospitalization (SHR, 0.54; 95% CI, 0.36-0.81; p = .01). Subgroup analysis found that hematological malignancy was associated with a high risk of AF recurrence (SHR, 5.68; 95% CI, 3.00-10.8; p < .001).

CONCLUSIONS

This study suggests that catheter ablation could be feasible for rhythm control of AF patients with concomitant cancer.

Safety of catheter ablation for atrial fibrillation in patients with cancer: a nationwide cohort study

BACKGROUND

Atrial fibrillation (AF) is the most common arrhythmia in patients with cancer, especially breast, gastrointestinal, respiratory, urinary tract, and hematological malignancies. Catheter ablation (CA) is a well-established, safe treatment option in healthy patients; however, literature regarding safety of CA for AF in patients with cancer is limited and confined to single centers.

OBJECTIVE

We aimed to assess the outcomes and peri-procedural safety of CA for AF in patients with certain types of cancer.

METHODS

The NIS database was queried between 2016 and 2019 to identify primary hospitalizations with AF and CA. Hospitalizations with secondary diagnosis of atrial flutter and other arrhythmias were excluded. Propensity score matching was used to balance the covariates between cancer and non-cancer groups. Logistic regression was used to analyze the association.

RESULTS

During this period, 47,765 CA procedures were identified, out of which 750 (1.6%) hospitalizations had a diagnosis of cancer. After propensity matching, hospitalizations with cancer diagnosis had higher in-hospital mortality (OR 3.0, 95% CI 1.5-6.2, p = 0.001), lower home discharge rates (OR 0.7, 95% CI 0.6-0.9, p < 0.001) as well as other complications such as major bleeding (OR 1.8, 95% CI 1.3-2.7, p = 0.001) and pulmonary embolism (OR 6.1, 95% CI 2.1-17.8, p < 0.001) but not associated with any major cardiac complications (OR 1.2, 95% CI 0.7-1.8, p = 0.53).

CONCLUSION

Patients with cancer who underwent CA for AF had significantly higher odds of in-hospital mortality, major bleeding, and pulmonary embolism. Further larger prospective observational studies are needed to validate these findings.

Accelerated Atherosclerosis and Cardiovascular Toxicity Induced by Radiotherapy in Breast Cancer

The number of patients diagnosed with breast cancer and cardiovascular disease is continuously rising. Treatment options for breast cancer have greatly evolved, but radiotherapy (RT) still has a key role in it. Despite many advances in RT techniques, cardiotoxicity is one of the most important side effects. The new cardio-oncology guidelines recommend a baseline evaluation, risk stratification and follow-up of these patients. Cardiotoxicity induced by RT can be represented by almost all forms of cardiovascular disease, with atherosclerosis being the most frequent. An interdisciplinary team should manage these patients, in order to have maximum therapeutic effect and minimum cardiovascular toxicity. This review will summarize the current incidence, risk factors, mechanisms and follow-up of RT-induced cardiovascular toxicity.

IA PULMONARY VEIN ATLAS FOR RADIOTHERAPY PLANNING

BACKGROUND AND PURPOSE

Cardiac arrhythmia is a recognised potential complication of thoracic radiotherapy, but the responsible cardiac substructures for arrhythmogenesis have not been identified. Arrhythmogenic tissue is commonly located in the pulmonary veins (PVs) of cardiology patients with arrhythmia, however these structures are not currently considered organs-at-risk during radiotherapy planning. A standardised approach to their delineation was developed and evaluated.

MATERIALS AND METHODS

The gross and radiological anatomy relevant to atrial fibrillation was derived from cardiology and radiology literature by a multidisciplinary team. A region of interest and contouring instructions for radiotherapy computed tomography scans were iteratively developed and subsequently evaluated. Radiation oncologists (n=5) and radiation technologists (n=2) contoured the PVs on the four-dimensional planning datasets of five patients with locally advanced lung cancer treated with 1.8-2.75 Gy fractions. Contours were compared to reference contours agreed by the researchers using geometric and dosimetric parameters.

RESULTS

The mean dose to the PVs was 35% prescription dose. Geometric and dosimetric similarity of the observer contours with reference contours was fair, with an overall mean Dice of 0.80 ± 0.02. The right superior PV (mean DSC 0.83 ± 0.02) had better overlap than the left (mean DSC 0.80 ± 0.03), but the inferior PVs were equivalent (mean DSC of 0.78). The mean difference in mean dose was 0.79 Gy ± 0.71 (1.46% ± 1.25).

CONCLUSION

A PV atlas with multidisciplinary approval led to reproducible delineation for radiotherapy planning, supporting the utility of the atlas in future clinical radiotherapy cardiotoxicity research encompassing arrhythmia endpoints.

Atrial fibrillation and breast cancer—Vicious twins? A systematic review and meta-analysis

Background

Epidemiological studies suggest a bidirectional association between atrial fibrillation and breast cancer. This study aimed to conduct a meta-analysis to elucidate the prevalence of atrial fibrillation among breast cancer patients, and the bidirectional association between atrial fibrillation and breast cancer.

Methods

PubMed, the Cochrane Library, and Embase were searched to identify studies reporting the prevalence, incidence, and bidirectional association between atrial fibrillation and breast cancer. The study was registered with PROSPERO (CRD42022313251). Levels of evidence and recommendations were assessed by the Grading of Recommendations Assessment, Development and Evaluation (GRADE).

Results

Twenty-three studies (17 retrospective cohort studies, 5 case-control studies and 1 cross-sectional study) involving 8,537,551 participants were included. Among patients with breast cancer, the prevalence of atrial fibrillation was 3% (11 studies; 95% CI: 0.6 to 7.1%) and the incidence was 2.7% (6 studies; 95% CI: 1.1 to 4.9%). Breast cancer was associated with increased risk of atrial fibrillation (5 studies; hazard ratio [HR]: 1.43, 95% CI: 1.12 to 1.82, I2 = 98%). Atrial fibrillation was also significantly associated elevated risk of breast cancer (5 studies HR: 1.18, 95% CI: 1.14 to 1.22, I2 = 0%). Grade assessment shown low certainty of the evidence for the risk of atrial fibrillation and moderate certainty of the evidence for the risk of breast cancer.

Conclusion

Atrial fibrillation is not uncommon in patients with breast cancer and vice versa. There is a bidirectional association between atrial fibrillation (low certainty) and breast cancer (moderate certainty).

Atrial Fibrillation and Cancer Patients: Mechanisms and Management

PURPOSE OF REVIEW

Cancer-related mortality has significantly declined over the past several decades as a result of improved screening, diagnostics, and therapeutics. Although cancer patients and survivors are living longer, there is increased risk of both short-term and long-term cardiovascular complications, including arrhythmia. In this review, we highlight the current evidence detailing the connections between atrial fibrillation and cancer, provide insight into the mechanisms driving this relationship, and share practical considerations for the management of atrial fibrillation in cancer patients and cancer survivors.

RECENT FINDINGS

Atrial fibrillation is an increasingly recognized condition among cancer patients, with epidemiological data showing increased incidence and worse outcomes in patients with cancer. Studies also describe a bidirectional relationship between cancer and atrial fibrillation, attributable in part to shared risk factors but also potentially due to shared biology. Cancer treatment-associated arrhythmia is an active area of investigation, with ongoing research to identify the mechanisms and pathophysiology behind this phenomenon. Furthermore, management of atrial fibrillation in patients with cancer presents unique challenges, particularly in management of anti-coagulation. Cancer patients have increased risk of developing atrial fibrillation due to the shared risk factors and biology of the two conditions. Moreover, various cancer therapeutics are known to be arrhythmogenic; however, mechanisms remain unclear. Further research is needed to better understand the pathophysiology of atrial fibrillation in cancer patient in order to establish prevention and treatment strategies specific to this population.

Anti-cancer Drugs Associated Atrial Fibrillation—An Analysis of Real-World Pharmacovigilance Data

Background

Several anti-cancer drugs have been linked to new onset atrial fibrillation (AF) but the true association of these drugs with AF is unknown. The FDA Adverse Event Reporting System (FAERS), a publicly available pharmacovigilance mechanism provided by the FDA, collects adverse event reports from the United States and other countries, thus providing real-world data.

Objectives

To identify anti-cancer drugs associated with AF using the FAERS database.

Methods

The FAERS database was searched for all drugs reporting AF as an adverse event (AE). The top 30 anti-cancer drugs reporting AF cases were shortlisted and analyzed. Proportional reporting ratio (PRR) was used to measure disproportionality in reporting of adverse events for these drugs.

Results

When analyzed for AF as a percentage of all reported AE for a particular drug, Ibrutinib had the highest percentage (5.3%) followed distantly by venetoclax (1.6%), bortezomib (1.6%), carfilzomib (1.5%), and nilotinib (1.4%). The percentage of cardiac AE attributable to AF was also highest for ibrutinib (41.5%), followed by venetoclax (28.4%), pomalidomide (23.9%), bortezomib (18.2%), and lenalidomide (18.2%). Drugs with the highest PRR for AF included ibrutinib (5.96, 95% CI= 5.70–6.23), bortezomib (1.65, 95% CI = 1.52–1.79), venetoclax (1.65, 95% CI = 1.46–1.85), carfilzomib (1.53, 95% CI = 1.33–1.77), and nilotinib (1.46, 95% CI = 1.31–1.63).

Conclusions

While newer anti-cancer drugs have improved the prognosis in cancer patients, it is important to identify any arrhythmias they may cause early on to prevent increased morbidity and mortality. Prospective studies are needed to better understand the true incidence of new onset AF associated with anti-cancer drugs.

Redox interactions-induced cardiac toxicity in cancer therapy

Cancer patients undergoing radiotherapy, chemotherapy, or targeted cancer therapy are exposed to the risk of several side effects because of the heavy production of ROS by ionizing radiation or some chemotherapy drugs. Damages to DNA, mitochondria, membrane and other organelles within normal tissue cells such as cardiomyocytes and endothelial cells lead to the release of some toxins which are associated with triggering inflammatory cells to release several types of cytokines, chemokines, ROS, and RNS. The release of some molecules following radiotherapy or chemotherapy stimulates reduction/oxidation (redox) reactions. Redox reactions cause remarkable changes in the level of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Excessive production of ROS and RNS or suppression of antioxidant defense enzymes leads to damage to critical macromolecules, which may continue for long times. Increased levels of some cytokines and oxidative injury are hallmarks of heart injury following cancer therapy. Redox reactions may be involved in several heart disorders such as fibrosis, cardiomyopathy, and endothelium injury. In the current review, we explain the cellular and molecular mechanisms of redox interactions following radiotherapy, chemotherapy, and targeted cancer therapy. Afterward, we explain the evidence of the involvement of redox reactions in heart diseases.

Relationship Between Radiation Exposure and Incident Atrial Fibrillation Among Atomic Bomb Survivors

Background: Atrial fibrillation (AF) is a common arrhythmia. Although radiation exposure is associated with an elevated risk of cardiovascular disease, the effects of radiation on arrhythmia, especially AF, are unclear. We evaluated the relationship between radiation and AF in a cohort of atomic bomb survivors. Methods and Results: From a baseline enrollment period (1967-1969) to 2009, 7,379 Hiroshima and Nagasaki atomic bomb survivors (mean baseline age 50.6 years, 65.8% women, 72.9% from Hiroshima) without AF and who had been exposed to estimated radiation doses between 0 and 3.614 Gy were followed-up once every 2 years. AF was identified by 12-lead electrocardiograms and medical records. Treating age as the time scale, AF incidence was modeled with Cox proportional hazards models adjusting for demographics, AF risk factors, and radiation. We modeled radiation as both a continuous variable and categorized according to radiation dose (Control [<0.005 Gy] and 5 equal-sized groups based on radiation dose quintiles in the cohort). Over 4 decades of follow-up, we identified 276 AF cases in 176,687 person-years, for an incidence rate of 1.56 per 1,000 person-years. After adjusting for sex and city, neither categorized, linear, nor linear-quadratic models showed substantive evidence of radiation effects. Similar results were obtained after adjusting for AF risk factors. Conclusions: There were no clear positive associations between radiation dose and AF risk, rather null or non-significant inverse associations.