What percentage of myocardial infarctions (MIs) are fatal?

Percentage of Heart Attacks That Are Fatal

Approximately 30-50% of heart attacks are fatal within the first month, with about half of these deaths occurring within the first 2 hours after symptom onset. 1

Community vs. Hospital Mortality

The mortality rate of heart attacks varies significantly depending on whether we're looking at community-based data or hospital-based data:

Community Setting:

• Overall fatality rate in the first month: 30-50% 1
• About half of these deaths occur within the first 2 hours 1
• This high initial mortality has remained relatively unchanged over the past 30 years 1

Hospital Setting:

• In-hospital mortality has decreased dramatically over time:
  • 25-30% before coronary care units (pre-1960s) 1
  • 18% in the mid-1980s (pre-thrombolytic era) 1
  • 6-7% with modern treatments (fibrinolysis, aspirin, coronary interventions) 1
  • 8.4% at 1 month in the European Heart Survey for ST-segment elevation acute coronary syndromes 1

Factors Affecting Heart Attack Mortality

Several factors influence the likelihood of survival following a heart attack:

1. Age: Older patients have higher mortality rates 1
2. Medical history: Previous infarction, diabetes, or stroke increase mortality risk 1
3. Infarct size and location: Anterior infarctions carry worse prognosis than inferior ones 1
4. Initial blood pressure: Low blood pressure at presentation indicates poorer outcomes 1
5. Killip class: Higher class indicates worse heart failure and higher mortality 1
6. ECG changes: Extent of ST-segment elevation/depression correlates with mortality 1
7. Time to treatment: Delayed presentation significantly increases mortality risk 2

Changes in Mortality Over Time

The WHO-MONICA investigators demonstrated that the introduction of new treatments in coronary care has been strongly linked with declining coronary event rates and 28-day case fatality 1. This improvement is primarily due to:

• Development of coronary care units
• Widespread use of fibrinolytic drugs
• Routine use of aspirin and other antithrombotics
• Increased availability of coronary interventions

Mechanical Complications and Mortality

Mechanical complications from ST-elevation myocardial infarction significantly increase mortality risk. During the COVID-19 pandemic, there was an observed increase in mechanical complications (14.3% vs 3.6% pre-pandemic) due to delayed presentations, though overall in-hospital mortality remained similar (6.4% vs 6.2%) 2.

Important Considerations

1. Early recognition is critical: About 750,000 heart attacks occur annually in the US, and early intervention is crucial for preventing mortality 3

2. Pre-hospital deaths: A substantial portion of heart attack deaths occur before patients reach the hospital, highlighting the importance of public education about symptoms and rapid emergency response 1

3. Regional variations: Significant regional differences exist in 30-day acute MI hospital mortality and readmission rates 1

4. Physical activity: Higher levels of physical activity are associated with lower case fatality in first-time heart attacks 4

Heart attack mortality has improved significantly in the hospital setting due to advances in treatment, but the overall community mortality remains high due to the substantial number of deaths occurring before medical contact. This underscores the importance of public education about heart attack symptoms and the need for immediate medical attention when symptoms occur.