Abstract
Carfilzomib is a second-generation irreversible proteasome inhibitors commonly used in the treatment of relapsed or refractory multiple myeloma. However, cardiac toxicity (heart failure, hypertension, coronary heart disease, etc.) has become the main factor leading to its reduction or withdrawal. We report a case of a 55-year-old female patient with multiple myeloma who developed sinus bradycardia following the administration of carfilzomib, along with a review of the relevant literature. The correlation between carfilzomib and cardiotoxicity was assessed by reviewing the medical history, applying the adverse drug reaction correlation evaluation, and using the Naranjo assessment scale. The clinical manifestations included chest tightness, shortness of breath, and abnormal electrocardiogram monitoring. The condition was effectively managed following treatment with a combination of trimetazidine and salbutamol. We conducted a literature review of 27 published cases of proteasome inhibitor-induced cardiac toxicity. In the 27 published cases, 12 cases were caused by carfilzomib (44.4%). To our knowledge, this is the first reported case of carfilzomib-associated sinus bradycardia, expanding the spectrum of proteasome inhibitors-related cardiotoxicity. This provides inspiration for suspected patients to stop using carfilzomib early and symptomatic treatment can effectively reduce mortality and improve prognosis.
Keywords
Introduction
Multiple myeloma (MM) is a malignant plasma cell disease characterized by abnormal proliferation of bone marrow plasma cells with excessive production of monoclonal immunoglobulin or light chain M protein, which seriously affect the quality of life of patients. 1 In the current study, the application of proteasome inhibitors (PIs) and immunomodulators can effectively improve the survival outcome of MM patients.2,3 Carfilzomib, a new type of PI, is composed of a tetrapeptide epoxy ketone structure. 4 In 2012, it was approved by the U.S. Food and Drug Administration for patients with relapsed or refractory MM, and then a variety of carfilzomib combination regimens were successively approved.5,6 In 2021, carfilzomib was approved for sale in China, providing a new treatment for MM patients in China. 7 Common causes of dose adjustment or treatment interruption of carfilzomib include neutropenia, hypertension, coronary heart disease, and renal insufficiency.8–10 We reported the clinical diagnosis and treatment process of a case of bradycardia caused by carfilzomib in a patient with MM, and summarized the relevant literature, aiming to attract the attention of clinicians to strengthen the monitoring of relevant indicators.
Case presentation
This was a case of a 55-year-old female with MM (158 cm, 59.5 kg, body surface area: 1.63 m2). In August 2024, the patient presented with intermittent pain in the right upper arm, which had aggravated for more than half a month, and resulted in a limitation of mobility. The examination conducted at the local hospital showed a lesion in the right humerus. To obtain further diagnosis and treatment, the patient came to our hospital on September 13. The patient self-reported no history of hypertension, heart disease, or familial genetic disorders. Given the limited efficacy of conservative treatment, surgical intervention was considered (high-sensitivity troponin: 0.003 μg/L; B-type natriuretic peptide precursor (proBNP): 48.2 ng/L). On September 18, a partial osteotomy of the right humerus was performed. Intraoperative frozen section diagnosis showed malignant round cell tumors Postoperative pathological and blood bone marrow cell morphological examination results were consistent with plasma cell myeloma (IgA type; Durie-Salmon, stage ⅢA; International Staging System, stage Ⅱ). The patient was subsequently admitted for chemotherapy. The timeline of this case was summarized in Figure 1.

Treatment and outcome timeline of this case report.
The patient was treated with VLD regimen (bortezomib (2 mg i.h. d1, d4), doxorubicin liposome (20 mg i.v. d2, d3) and dexamethasone (20 mg i.v. d1)) since September 20. After the end of the second cycle, the patient developed significant enlargement of the local mass along with tenderness (normal electrocardiogram (ECG); proBNP: 67 ng/L). Subsequently, the chemotherapy regimen was changed to KT-DECP (carfilzomib 30 mg i.v. d1, d2, 43 mg i.v. d8, d9, d15, d16; thalidomide 100 mg p.o. qn; dexamethasone, 20 mg i.v. d1, d2, d3, d4; etoposide, 60 mg i.v. d3, d4, d5, d6; cyclophosphamide, 600 mg i.v. d3, d4, d5, d6; cisplatin, 16 mg i.v. d3, d4, d5, d6). Subsequently, the patient was discharged after the symptoms of the right upper arm swelling and tenderness were relieved. On January 10, 2025, the patient was admitted to further treatment, and the admission examination showed a slow heart rate. As no additional adverse reactions were observed, KT-DECP treatment was continued. On January 14, the patient developed palpitation, breathlessness and chest tightness after chemotherapy (heart rate: 38–45 bpm; high-sensitivity troponin: 0.003 μg/L; proBNP: 762 ng/L, RR interval: 1.91 s). The RR interval refers to the time interval between two consecutive R waves on ECG, which reflects the duration of one cardiac cycle corresponding to ventricular electrical depolarization and repolarization. Both the ECG report and the long RR interval suggested that the patient suffered sinus bradycardia with arrhythmia (Figure 2). The 24H dynamic ECG results revealed that the lowest heart rate was 33 bpm, while the highest was 112 bpm, both of which were consistent with sinus rhythm. Occasional atrial premature beats and ventricular premature beats were observed. Additionally, a downward displacement of the ST segment was noted, but no conduction abnormalities were detected. Fortunately, the results of echocardiography were normal, and the biplane ejection fraction was more than 50%, indicating that the cardiac structure was unaffected.

Twelve-lead electrocardiogram before (a) and after (b) chemotherapy with carfilzomib; 12-lead electrocardiogram after discontinuation of carfilzomib and symptomatic treatment (c).
After evaluation by clinical pharmacists and doctors, sinus bradycardia caused by carfilzomib was considered. Other causes such as hypothyroidism, electrolyte imbalance, and conduction system disease were considered but ruled out based on the results of the examination. Consequently, carfilzomib was discontinued, and trimetazidine hydrochloride tablets (20 mg p.o. tid) and salbutamol sulfate sustained-release capsules (8 mg p.o. bid) were given for symptomatic treatment. And then the indicators returned to normal levels (normal ECG; proBNP: <20 ng/L) and the patient was discharged. On February 10, the patient was re-admitted to the hospital, and the regimen was changed to DaraV (Daratumumab, bortezomib)-DECP. There was no cardiac discomfort that occurred again. Therefore, the diagnosis of sinus bradycardia induced by carfilzomib was established. Up to October 2025, ECG results of the patient demonstrated normal findings. Follow up at 1- and 3-months post-discontinuation showed sustained normal heart rate and no recurrence of bradycardia.
Discussion and review of literature
In this article, we introduce a case of sinus bradycardia that occurred in a patient during carfilzomib therapy for MM. Cardiac toxicity is a common adverse reaction in the treatment of carfilzomib, and among the PIs used in clinical practice, carfilzomib has the strongest correlation with cardiac toxicity. In a 55-year-old female patient, several potential causes of sinus bradycardia were considered. First, the patient had no history of cardiovascular disease, and echocardiography revealed no abnormalities, suggesting that the bradycardia was not secondary to cardiac insufficiency. Second, thyroid function was assessed after the patient presented with symptoms such as chest tightness. The measured thyroid-stimulating hormone level was 0.64 mIU/L, which excluded hypothyroidism as a cause of the sinus bradycardia. Third, hyperkalemia was also considered as a potential etiology. Repeated serum potassium measurements during treatment consistently showed values below 5.5 mmol/L, ruling out hyperkalemia as a contributing factor.
Additionally, the potential relationship between the carfilzomib and adverse reactions was evaluated using multiple assessment methods. According to the evaluation method for the association of adverse drug reactions by the National Adverse Drug Reaction Monitoring Center: (1) The patient in this case had no history of bradycardia or other related symptoms but developed sinus bradycardia with arrhythmia following the application of carfilzomib. Therefore, there is a reasonable time relationship between the use of carfilzomib and the occurrence of cardiac toxicity (+); (2) According to the clinical application guidelines for the treatment of MM with carfilzomib, 11 cardiac toxicity meets the known adverse reaction types of carfilzomib (+); (3) After discontinuing the carfilzomib, the results of ECG returned to normal (+); (4) After the first use of carfilzomib, ECG monitoring prompts heart rate to slow down. The patient experienced palpitations and chest tightness when administered again. The ECG report showed sinus bradycardia with arrhythmia, meeting the same adverse reaction event occurred (+); (5) Thalidomide, discontinued at the same time, may also cause cardiac toxicity. Although there are few reports on this, it cannot be entirely ruled out (±). However, the temporal relationship with carfilzomib administration and resolution upon its discontinuation strongly supports carfilzomib as the primary cause. The clinical pharmacist evaluated the association between carfilzomib and sinus bradycardia as “highly probable.” In addition, we also evaluated the relationship between carfilzomib and sinus bradycardia by the Naranjo adverse drug reaction probability scale. The results showed that the relationship between carfilzomib and bradycardia was “most likely” (score of 7). 12 The details were shown in Table 1.
The Naranjo score results for carfilzomib-induced bradycardia.
After reviewing literatures and guidelines, clinical pharmacists further confirmed that the adverse reaction is closely related to carfilzomib. The reasons are as follows: the 2022 ESC (European Society of Cardiology) Oncology Cardiology Guidelines 13 states that when patients apply PIs, the risk of serious cardiovascular adverse events increases. Therefore, strict cardiovascular risk assessment, early prevention, and proper monitoring and management are necessary before using carfilzomib treatment. We recommend continuous ECG monitoring during the first few cycles of carfilzomib therapy, especially in patients with pre-existing cardiac risk factors. In addition, the global phase III clinical trial ENDEAVOUR study also reported efficacy and safety data of carfilzomib. 14 The results showed that compared with the bortezomib + dexamethasone regimen, the incidence of heart failure was significantly increased with the carfilzomib + dexamethasone regimen (4.8% vs 1.1%).
PIs, including bortezomib, carfilzomib, and ixazomib, are the main therapeutic drugs for MM. In recent years, a variety of cardiac adverse reactions during treatment induced by PIs have been of concern. We investigated previously reported cases of cardiotoxicity associated with PIs, with a total of 23 publications compassing 26 cases (Table 2).15–37 The patients we studied are predominantly over 50 years old, with a significant proportion having a history of cardiovascular diseases such as hypertension. We hypothesize that elderly individuals with underlying diseases have weakened cardiac function, thereby increasing the likelihood of experiencing adverse cardiac reactions following the administration of PIs. And in 26 patients, there were 15 cases of heart failure, 4 cases of ventricular dysfunction, and one case each of myocarditis, pericardial effusion, angina, myocardial scar, hypertension, myocardial infarction, and Brugada syndrome. The majority of patients developed symptoms after four to five cycles of treatment. The time to symptom onset ranged from as early as 1 day to as long as nine cycles among the enrolled patients. At present, there is no case of sinus bradycardia with arrhythmia caused by carfilzomib similar to that reported in this paper. Studies have shown that carfilzomib cardiotoxicity may involve direct myocardial injury, autonomic dysfunction, or ischemic effects. The mechanism of bradycardia remains unclear but may relate to impaired conduction or autonomic modulation. 38 In addition, only four patients chose to continue the original PIs treatment after symptom relief. It is also worth noting that three patients died because of the rapid progression of the cancer after drug withdrawal. In the early detection of abnormal heart rate, electrocardiography, echocardiography, cardiac magnetic resonance imaging, and monitoring of certain biochemical markers (such as troponin, myocardial enzymes, and proBNP) remain the primary tools utilized by most researchers. These methods hold significant value for guiding the management of subsequent clinicians. Long-term follow-up and monitoring are necessary, since abnormal ECG caused by chemotherapy drugs can increase the risk of cardiovascular disease in patients. 39 These cases remind us to strengthen the monitoring of PIs administration, which is critical for ensuring patient medication safety and should be highly prioritized by clinical physicians.
Summary of previous studies reporting cardiotoxicity caused by PIs.
PIs: proteasome inhibitor; ECG: electrocardiogram; ST: plateau phase of the ventricular myocyte action potential; aVR: augmented Vector Right; aVF: augmented Vector Foot; QTc: corrected QT interval.
Conclusion
This article focuses on the pharmacovigilance of cardiac toxicity in patients with MM who are treated with carfilzomib. Clinical pharmacists play an essential role in evaluating heart rate and ECG findings, enabling timely discontinuation of carfilzomib to prevent severe consequences such as heart failure. Pharmacists are deeply involved in both treatment and monitoring, summarizing effective strategies for patient care, including: (1) Comprehensive assessments of the cardiac health status of the patient, particularly left ventricular function and electrophysiological parameters, should be conducted prior to initiating treatment to facilitate personalized treatment planning. (2) Closely monitoring cardiac function indicators (ECG, echocardiography, blood pressure, heart rate, troponin I, high-sensitivity troponin I, B-type natriuretic peptide, proBNP) during treatment to detect early changes in cardiac function, adjust medication regimens promptly, and minimize harm caused by cardiotoxic reactions. (3) Managing severe respiratory distress, hypertension, or heart failure appropriately, reducing or discontinuing medication as required, and continuing cardiovascular risk assessment for 12 months post-treatment with carfilzomib.
Footnotes
Acknowledgements
The authors thank the staff of the Hematology Department of Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine for their collaboration.
Consent for publication
Written informed consent was obtained from the patient for their anonymized information to be published in this article.
Author contributions
XCZ conceived and designed this study. XCZ and DMS did the literature review and drafted the manuscript. RX, SDZ, and YQ assisted in data collection and patient follow-up. GC and CKC made substantial contributions to general supervision of the research group. JPZ and CKC reviewed and revised the manuscript critically for important intellectual content, and approved the final version. All authors read and approved the manuscript.
Funding
The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by Shanghai Sixth People’s Hospital Institutional-Level Research Project on Hospital Management (No. Lygl202407) and Shanghai Municipal Health Commission (No. 2020YJZX0205).
Declaration of conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Data availability statement
Data sharing is not applicable to this article as no data sets were generated or analyzed during this study.
