Background: Patients are at risk of myocardial injury after major non-cardiac surgery and during acute illness. Myocardial injury is associated with mortality, but often asymptomatic and currently detected through intermittent cardiac biomarker screening. This delays diagnosis, where vital signs deviations may serve as a proxy for early signs of myocardial injury. This study aimed to assess the association between continuous monitored vital sign deviations and subsequent myocardial injury following major abdominal cancer surgery and during acute exacerbation of chronic obstructive pulmonary disease. Methods: Patients undergoing major abdominal cancer surgery or admitted with acute exacerbation of chronic obstructive pulmonary disease had daily troponin measurements. Continuous wireless monitoring of several vital signs was performed for up to 96 h after admission or surgery. The primary exposure was cumulative duration of peripheral oxygen saturation (SpO₂) below 85% in the 24 h before the primary outcome of myocardial injury, defined as a new onset ischaemic troponin elevation assessed daily. If no myocardial injury occurred, the primary exposure was based on the first 24 h of measurement. Results: A total of 662 patients were continuously monitored and 113 (17%) had a myocardial injury. Cumulative duration of SpO₂ < 85% was significantly associated with myocardial injury (mean difference 14.2 min [95% confidence interval −4.7 to 33.1 min]; p =.005). Durations of hypoxaemia (SpO₂ < 88% and SpO₂ < 80%), tachycardia (HR > 110 bpm and HR > 130 bpm) and tachypnoea (RR > 24 min⁻¹ and RR > 30 min⁻¹) were also significantly associated with myocardial injury (p <.04, for all). Conclusion: Duration of severely low SpO₂ detected by continuous wireless monitoring is significantly associated with myocardial injury in high-risk patients admitted to hospital wards. The effect of early detection and interventions should be assessed next.