Differences in Symptoms and Pre-Hospital Delay Among Acute Myocardial Infarction Patients According to ST-Segment Elevation on Electrocardiogram: An Analysis of China Acute Myocardial Infarction (CAMI) Registry
Acute myocardial infarction (AMI) is a critical cardiovascular event that remains a leading cause of morbidity and mortality worldwide. The classification of AMI into ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation myocardial infarction (NSTEMI) is based on the presence or absence of ST-segment elevation on an electrocardiogram (ECG). While STEMI is often associated with classic symptoms such as persistent chest pain, NSTEMI patients frequently present with atypical symptoms, which can lead to delays in seeking medical care and worse outcomes. This study, utilizing data from the China Acute Myocardial Infarction (CAMI) registry, aims to provide a comprehensive comparison of symptoms and pre-hospital delays between STEMI and NSTEMI patients, shedding light on the clinical characteristics and management challenges associated with these two types of AMI.
Background and Significance
Chest pain is the hallmark symptom of AMI, yet approximately one-third of patients present without this classic symptom. Atypical presentations, such as chest distress, shortness of breath, or nausea, are more common in NSTEMI patients and are associated with higher in-hospital mortality. Despite the growing prevalence of NSTEMI, particularly in Western countries, there is a lack of detailed studies on the symptomatology of NSTEMI, especially among Asian populations. This study addresses this gap by analyzing a large cohort of AMI patients in China, providing valuable insights into the differences in symptoms and pre-hospital delays between STEMI and NSTEMI patients.
Methods
The study enrolled 21,994 patients diagnosed with AMI from the CAMI registry between January 2013 and September 2014. Patients were classified into two groups based on the presence or absence of ST-segment elevation on ECG: STEMI (N=16,315) and NSTEMI (N=5,679). Data on patient demographics, medical history, symptoms at admission, and time to hospital were extracted and compared between the two groups. Symptoms assessed included persistent chest pain, diaphoresis, chest distress, radiation pain, nausea or vomiting, shortness of breath, and others. Multivariable logistic regression analysis was performed to identify independent predictors of atypical symptoms.
Results
Baseline Characteristics
The study found significant differences in baseline characteristics between STEMI and NSTEMI patients. NSTEMI patients were older (mean age: 65.6 vs. 62.0 years), more likely to be female (31.8% vs. 23.6%), and had a higher prevalence of comorbidities such as diabetes (24.7% vs. 18.7%), prior myocardial infarction (11.9% vs. 5.9%), and hypertension (59.5% vs. 48.7%). Additionally, NSTEMI patients were more likely to be non-smokers (51.9% vs. 43.1%).
Clinical Symptoms
NSTEMI patients were less likely to present with persistent chest pain (54.3% vs. 71.4%), diaphoresis (48.6% vs. 70.0%), and radiation pain (26.4% vs. 33.8%) compared to STEMI patients. Conversely, NSTEMI patients were more likely to experience chest distress (42.4% vs. 38.3%), shortness of breath (24.5% vs. 21.2%), and recurrent angina (5.9% vs. 2.6%). Notably, 2% of NSTEMI patients and 1.2% of STEMI patients presented without any symptoms.
Time to Hospital
NSTEMI patients exhibited longer pre-hospital delays compared to STEMI patients. A higher proportion of NSTEMI patients presented to the hospital 1 to 7 days after symptom onset (41.5% vs. 23.8%) or between 12 to 24 hours (13.9% vs. 10.3%). In contrast, fewer NSTEMI patients sought medical care within 3 hours of symptom onset (14.5% vs. 23.5%).
Independent Predictors of Atypical Symptoms
Multivariable analysis identified several independent predictors of atypical symptoms, including older age, diabetes, higher Killip classification level, and the presence of predromal symptoms. Importantly, NSTEMI was a significant independent predictor of atypical symptom presentation (odds ratio: 1.974, 95% confidence interval: 1.849–2.107).
Discussion
The findings of this study highlight the distinct clinical profiles of STEMI and NSTEMI patients, particularly in terms of symptomatology and pre-hospital delays. NSTEMI patients are more likely to present with atypical symptoms such as chest distress and are less likely to experience classic symptoms like persistent chest pain and diaphoresis. These differences may contribute to the longer pre-hospital delays observed in NSTEMI patients, as atypical symptoms may be less readily recognized as indicative of a heart attack.
The study’s results are consistent with previous research indicating that NSTEMI patients tend to be older and have more comorbidities, which can complicate the recognition of AMI symptoms. Additionally, the smaller infarct size and less extensive myocardial involvement in NSTEMI may result in less intense symptoms, further contributing to delays in seeking medical care.
The implications of these findings are significant for both clinicians and patients. Increased awareness of the atypical symptoms associated with NSTEMI is crucial for prompt recognition and treatment, which can improve outcomes. Educational initiatives aimed at the public and healthcare providers should emphasize the diverse presentation of AMI symptoms, particularly in high-risk populations such as older adults and those with comorbidities.
Limitations
While this study provides valuable insights, it has several limitations. The data are derived from a Chinese population, and the findings may not be generalizable to other ethnic groups. Additionally, the study did not include follow-up data, limiting the ability to assess the long-term impact of symptom presentation on patient outcomes. Finally, as an observational study, it is subject to potential biases inherent in registry-based research.
Conclusion
In conclusion, this study underscores the importance of recognizing the differences in symptoms and pre-hospital delays between STEMI and NSTEMI patients. NSTEMI patients are more likely to present with atypical symptoms and experience longer delays in seeking medical care, which can have significant implications for their management and outcomes. Enhanced awareness and education regarding the diverse presentation of AMI symptoms are essential for improving the timely recognition and treatment of this life-threatening condition.
doi.org/10.1097/CM9.0000000000000122
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