Transient bradycardia during

objectiveLutetium (¹⁷⁷Lu) oxodotreotide (¹⁷⁷Lu-DOTATATE, Lutathera®) is widely used for neuroendocrine tumors. Although cardiovascular adverse events are not well recognized, we frequently observe bradycardia during infusion under monitoring. We aimed to characterize heart-rate changes during ¹⁷⁷Lu-DOTATATE administration and explore risk factors for bradycardia.

methodsWe retrospectively reviewed 130 administrations in 37 patients (April 2022–April 2025). Heart rate was recorded at four time points: (i) upon entering the room, (ii) the start of ¹⁷⁷Lu-DOTATATE administration (during L-lysine/L-arginine amino acid infusion), (iii) dose-rate adjustment at 10 min, and (iv) the end of infusion at 30 min. Repeated-measures ANOVA was used to evaluate changes in vital signs. Demographics, comorbidities, and laboratory values (electrolytes, hemoglobin, albumin, total protein) were collected. Cardiomegaly on imaging was determined visually using recent CT or MRI. Multivariable analyses were performed to examine predictors of heart rate change. Patient characteristics were also compared between those with and without bradycardia (≤ 50 bpm) using the chi-squared test.

resultsMean heart rate decreased over time: upon entering the room (72.3 bpm), at the start of ¹⁷⁷Lu-DOTATATE administration (64.5 bpm), and during dose rate adjustment (59.5 bpm). (all p < 0.001). Furthermore, at the end of infusion (66.2 bpm), it returned to a level similar to that at the start of ¹⁷⁷Lu-DOTATATE administration; patterns were similar across treatment cycles. Mean blood pressure decreased upon initiation of ¹⁷⁷Lu-DOTATATE (119.3/73.6 mmHg) compared to upon entering the room (127.8/78.3 mmHg), with no differences observed at other time points. Twenty-two administrations reached ≤ 50 bpm; chest discomfort occurred in five instances and resolved with observation. Multivariable models showed no significant predictors for the magnitude of heart-rate change. However, cardiac enlargement was associated with bradycardia during rate adjustment (p = 0.045). No significant associations were seen with age, sex, history of arrhythmia, or laboratory parameters.

conclusionsTransient heart-rate decline, occasionally meeting bradycardia, commonly occurs during ¹⁷⁷Lu-DOTATATE infusion but typically resolves by completion and rarely requires intervention. Recognizing its benign, self-limiting nature—and the higher susceptibility among patients with preexisting cardiac enlargement—may reduce unnecessary treatment interruptions and improve procedural safety.