Higher mortality among MI patients with atypical symptoms
Impact of myocardial infarction symptom presentation on emergency response and survival
Introduction and methods
Acute MI can present with varying symptoms. Fast referral of suspected MI is important as time to hospital submission has an impact on chance of survival [1-3]. There is not much known about how the type of initial symptom presentation of MI affects the referral and survival rates in people that call the emergency number or non-emergency medical helpline. This study investigated the association between initial symptoms in patients later diagnosed with MI, and the likelihood of admission to the emergency department and 30-day mortality.
This study was conducted in Copenhagen, Denmark. People with health issues can call a 24-h non-emergency medical helpline and an emergency number. Both services are tax-funded and are free of charge. All calls to the non-emergency medical helpline and the emergency number by people aged ≥30 between 1st January 2014 and 31st December 2018 were analyzed. Out of a total of 1 184 359 calls, 8336 calls for 7778 patients with an MI diagnosis at the hospital or MI as cause of death ≤72h after the call were included in this analysis. At both medical services, the primary symptom reported in the call was registered. Registered symptoms used in this analysis included chest pain, atypical symptoms and unconsciousness. The two main outcomes of this study were: The emergency response (i.e. immediate action following calls), and 30-day mortality. The emergency response was divided into 4 categories: 1) No referral for treatment (including watchful waiting or referral to a general practitioner); 2) self-transport to hospital, non-emergency patient transport, and home visits; 3) Non-urgent dispatch of non-emergency ambulances; and 4) Emergency dispatch of emergency ambulances with lights and sirens. In addition, in-hospital procedures (including coronary angiography (CAG), percutaneous coronary intervention (PCI), and coronary artery bypass grafting (CABG)) up to 7 days after the call, time between hospital arrival and registration at cardiology ward, differential diagnosis of MI (STEMI, NSTEMI, and unknown), and troponin values measured up to 72h were analyzed.
- A total of 7222 calls had information about the reported symptom. 72% (5219/7222) Of patients presented with chest pain and 24% (1713/7222) with atypical symptoms. Breathing problems was the most common atypical symptom (8%, 556/7222).
- Among MI patients with chest pain, 95% (3337/3508) received an emergency dispatch at the emergency number and 76% (1306/1711) at the non-emergency medical helpline. Among MI patients with atypical symptoms, 62% (544/900) received an emergency dispatch at the emergency number and 17% (137/813) at the non-emergency medical helpline. Among unconscious MI patients, 99% (283/289) and 100% (≤15/≤15) received emergency dispatch at the emergency number and non-emergency medical helpline, respectively.
- 30-day mortality for patients with chest pain was 5% (163/3508) among patients that called the emergency number and 3% (49/1711) at the non-emergency medical helpline. Among MI patients with atypical symptoms, 30-day mortality was 23% (206/900) among patients that called the emergency number and 15% (125/813) at the non-emergency medical helpline. 30-day mortality among unconscious patients was 71% (204/286) and 75% (≤15/≤15) at the emergency number and non-emergency medical helpline, respectively.
- The standardized 30-day mortality was 4.3% (95%CI 4.2–4.3%) for MI patients with chest pain and 15.6% (95%CI 15.4–15.9%) for MI patients with atypical symptoms.
- Time from call to first troponin was longer in MI patients with atypical symptoms (median 1.9h) compared to all other symptoms. 52% of patients with chest pain, 59% of unconscious patients and 32% of patients with atypical symptoms were directly refereed to a cardiology ward. 79% of MI patients with chest pain, 75% of unconscious MI patients and 58% MI patients with atypical symptoms received CAG within 7 days of the call.
Among MI patients calling for help at the emergency number or non-emergency medical helpline, 72% presented with chest pain and 24% presented with atypical symptoms. Breathing problems was the most common atypical symptom. MI patients with atypical symptoms had a lower chance of receiving an emergency dispatch, and higher 30-day mortality compared to MI patients with chest pain.