Recurrent unexplained resting sinus tachycardia as a marker of adverse cardiovascular outcomes in cancer patients

Recurrent unexplained resting sinus tachycardia is common in cancer patients and is frequently attributed to reversible physiologic stressors. Whether unexplained resting sinus tachycardia is associated with adverse cardiovascular outcomes (ACVO) and mortality in oncology populations remains poorly defined.

This retrospective cohort study enrolled 198 adults with confirmed cancer and ≥ 3 electrocardiogram (ECG) studies during 3 separate hospital encounters at a tertiary center (January 2019-January 2026). Patients with ≥3 ECG-confirmed episodes of unexplained resting sinus tachycardia (n = 38) were compared to patients with normal sinus rhythm (NSR) (n = 160). The primary outcome was ACVO; secondary outcomes included major adverse cardiovascular events (MACE) and all-cause mortality. Logistic regression and Cox proportional hazards models were used for multivariable analysis. A landmark sensitivity analysis was additionally performed to address potential immortal-time bias.

Patients with recurrent resting sinus tachycardia had significantly lower hemoglobin (9.8 ± 1.4 vs. 11.1 ± 2.3 g/dL; p < 0.001) at baseline. Blood pressure at the index ECG was modestly lower but within the normal range in the exposed group (systolic 123.9 ± 10.9 vs. 129.5 ± 11.3 mmHg, p = 0.006; diastolic 64.6 ± 7.5 vs. 70.5 ± 9.9 mmHg, p < 0.001). The median interval between the first and third qualifying ECG was 2.5 months (IQR 1.4-5.5). ACVO occurred in 71.1% vs. 13.8% (adjusted OR 12.27, 95% CI 5.14-29.27; p < 0.001); MACE in 31.6% vs. 8.8% (adjusted OR 3.80, 95% CI 1.49-9.72; p = 0.005) of exposed vs. unexposed patients. Over a median follow-up of 3.97 years (IQR 1.59-7.93), Kaplan-Meier analysis showed lower survival in the exposed group (log-rank χ² = 7.72; p = 0.006); however, after covariate adjustment, the mortality association was attenuated and no longer significant (adjusted HR 1.51, 95% CI 0.86-2.64; p = 0.15). Lower hemoglobin was the only independent predictor of mortality (adjusted HR 0.81 per 1 g/dL; 95% CI 0.69-0.95; p = 0.008).

Recurrent unexplained resting sinus tachycardia identifies patients with cancer at increased risk of both MACE and ACVO, although residual confounding may have inflated the observed associations. Sinus tachycardia was not independently associated with mortality after adjustment for illness burden. Recurrent sinus tachycardia may serve as an accessible marker of cardiovascular vulnerability that warrants prospective investigation in cardio-oncology.