Differences in symptoms and pre – hospital delay among AMI patients by ECG ST – elevation

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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
Rui Fu, Chen-Xi Song, Ke-Fei Dou, Jin-Gang Yang, Hai-Yan Xu, Xiao-Jin Gao, Qian-Qian Liu, Han Xu, Yue-Jin Yang
Department of Cardiology, Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, China.

Chest pain is often called the “classic” sign of a heart attack, but nearly 30% of people with acute myocardial infarction (AMI) don’t experience this symptom. For those with non-ST segment elevation myocardial infarction (NSTEMI)—a type of AMI where the electrocardiogram (ECG) shows no ST-segment elevation—the signs can be even more ambiguous. This ambiguity leads to dangerous delays in care: studies show atypical symptoms increase in-hospital mortality risk by up to 50%. Yet most research focuses on STEMI (ST-segment elevation MI), leaving NSTEMI—especially in Asian populations—understudied.

A 2019 study from researchers at Fuwai Hospital (Chinese Academy of Medical Sciences and Peking Union Medical College) sought to fill this gap. By analyzing data from the China Acute Myocardial Infarction (CAMI) Registry—one of Asia’s largest AMI databases—the team compared symptoms, pre-hospital delays, and patient characteristics between STEMI and NSTEMI patients. Their findings, published in the Chinese Medical Journal, offer critical insights into how NSTEMI presents differently—and why rapid recognition is life-saving.

What the Study Did

The researchers analyzed data from 21,994 AMI patients enrolled in the CAMI Registry between January 2013 and September 2014. Eligible patients met the Third Universal Definition of Myocardial Infarction, a global standard for diagnosing AMI. Participants were split into two groups:

  • STEMI: 16,315 patients (74.2% of the cohort) with ST-segment elevation on ECG (a sign of complete coronary artery blockage).
  • NSTEMI: 5,679 patients (25.8%) without ST-segment elevation.

The team compared baseline characteristics (age, sex, comorbidities), symptoms at admission, and time from symptom onset to hospital arrival (pre-hospital delay) between the two groups.

Key Findings: NSTEMI vs. STEMI

The study uncovered three critical differences that change how we think about NSTEMI:

1. NSTEMI Patients Are Older, Female, and Have More Comorbidities

Compared to STEMI patients, NSTEMI patients:

  • Were 3.6 years older on average (65.6 vs. 62.0 years).
  • Were 35% more likely to be female (31.8% vs. 23.6%).
  • Had higher rates of chronic conditions: diabetes (24.7% vs. 18.7%), hypertension (59.5% vs. 48.7%), prior heart attack (11.9% vs. 5.9%), and heart failure (5.9% vs. 1.5%).

These comorbidities aren’t just “extra” health issues—they can mask NSTEMI symptoms. For example, a patient with diabetes might dismiss chest pressure as “indigestion” or shortness of breath as “asthma,” delaying care.

2. NSTEMI Symptoms Are Atypical—Not Just Chest Pain

The biggest surprise? NSTEMI patients were 50% less likely to have “classic” heart attack symptoms:

  • Persistent chest pain (≥20 minutes): 54.3% of NSTEMI patients vs. 71.4% of STEMI patients.
  • Diaphoresis (heavy sweating): 48.6% vs. 70.0%.
  • Radiating pain (to arms, neck, or jaw): 26.4% vs. 33.8%.

Instead, NSTEMI patients reported more subtle, easy-to-miss symptoms:

  • Chest distress (pressure/tightness): 42.4% vs. 38.3% of STEMI patients.
  • Shortness of breath: 24.5% vs. 21.2%.
  • Recurrent angina (on-and-off chest pain): 5.9% vs. 2.6%.
  • Palpitations: 14.5% vs. 13.0%.

Even more concerning: 2% of NSTEMI patients had no symptoms at all when admitted—double the rate of STEMI patients (1.2%).

3. NSTEMI Patients Delay Care Longer

Time is muscle in heart attacks: every minute without treatment increases permanent heart damage. Yet NSTEMI patients took far longer to reach the hospital:

  • Only 14.5% of NSTEMI patients arrived within 3 hours of symptom onset vs. 23.5% of STEMI patients.
  • 41.5% of NSTEMI patients waited 1–7 days to seek care vs. 23.8% of STEMI patients.
  • 13.9% waited 12–24 hours vs. 10.3% of STEMI patients.

Why the delay? The researchers cite two factors:

  • Familiarity with symptoms: NSTEMI patients were more likely to have prior angina, so they may dismiss new symptoms as “routine.”
  • Masked symptoms: Comorbidities like diabetes or heart failure can make it hard to distinguish NSTEMI from chronic issues.

Why This Matters for You

For patients, the takeaway is simple:

  • Don’t ignore “atypical” symptoms: Chest pressure, shortness of breath, or recurrent pain—even if it’s not “classic” chest pain—could be NSTEMI.
  • Act fast: Every hour of delay increases your risk of permanent heart damage. Call emergency services (e.g., 120 in China) immediately.

For doctors, it means:

  • Be vigilant with high-risk groups: Older patients, women, and those with comorbidities are more likely to have atypical NSTEMI symptoms.
  • Use objective tests early: Don’t rely solely on symptoms—use ECG and troponin (a blood test for heart damage) to diagnose NSTEMI.

Limitations to Consider

The study has three key limitations:

  1. Population bias: All participants were from China, so results may not apply to other ethnic groups.
  2. No long-term follow-up: The study didn’t track survival rates or quality of life after discharge.
  3. Observational design: It can’t prove that NSTEMI causes longer delays—only that the two are linked.

The Bottom Line

This study is a critical step forward in understanding NSTEMI. It confirms what many doctors suspected: NSTEMI symptoms are far more varied than the “textbook” description, and delays in recognition are a major barrier to saving lives. For patients, the message is clear: if something feels “off” with your heart—even if it’s not chest pain—seek care immediately. For doctors, it’s a reminder to look beyond symptoms and use objective tests to diagnose NSTEMI early.

As NSTEMI rates rise globally—including in China—this research could help millions get the care they need before it’s too late.

Published in Chinese Medical Journal 2019;132(5):519–524.
doi:10.1097/CM9.0000000000000122
Trial Registration: ClinicalTrials.gov (NCT01874691)

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