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This Australian study investigated the association between respiratory infection and MI. 578 patients with angiographically confirmed MI were interviewed within 4 days of hospitalisation to assess for history of respiratory infection. Using case-crossover methodology, exposure to respiratory infection shortly before the MI was compared with the usual frequency of exposure in the past year. Symptoms of respiratory infection were reported by 17% and 21% of patients within 7 and 35 days, respectively, prior to MI. The relative risk for MI occurring within 1–7 days after respiratory infection was 17.0, and declined with time. Subgroup analysis showed that the risk tended to be lower in groups taking regular cardiac medications. Milder upper respiratory tract infection symptoms were associated with a lower risk of MI within 1–7 days (relative risk, 13.5). This Australian study nicely demonstrates the little published data that acute respiratory infections may trigger ACS, particularly in the first week after the infection begins. Although not reported, these MIs presumably occurred in older patients with underlying coronary artery disease and chronic obstructive pulmonary disease, and if so it would be interesting to study whether using prophylactic low-dose antibiotics in this type of patient to reduce chest infections would reduce the incidence of MI. Rapid rule-out of acute myocardial infarction with a single high-sensitivity cardiac troponin T measurement below the limit of detection: This collaborative meta-analysis estimated the ability of a single high-sensitivity cardiac troponin T (hs-TnT) concentration below the limit of detection to rule out AMI in adults presenting to the ED with chest pain. A search of EMBASE and Medline identified 11 cohort studies involving 9241 adults who presented to the ED with possible ACS and underwent electrocardiogram (ECG) and hs-TnT measurements. 2825 (30.6%) patients were classified as low-risk (no new ischaemia on ECG and hs-TnT measurements below the limit of detection [<0.005 µg/L]). 14 (0.5%) of these low-risk patients had an AMI during hospitalisation. Sensitivity of the risk classification for AMI ranged from 87.5–100% in individual studies, and sensitivity for 30-day major adverse cardiac events ranged from 87.9–100%.