Angiographic Characteristics and In-Hospital Mortality Among Patients with ST-Segment Elevation Myocardial Infarction Presenting Without Typical Chest Pain
Patients with ST-segment elevation myocardial infarction (STEMI) who present without typical chest pain represent a clinically significant subgroup with distinct characteristics and outcomes. This study, utilizing data from the China Acute Myocardial Infarction (CAMI) registry, aimed to explore the angiographic features, management patterns, and mortality risks in this population. The findings highlight critical differences in baseline demographics, lesion characteristics, and clinical outcomes between STEMI patients with and without typical chest pain, offering insights into the factors contributing to their poorer prognosis.
Study Design and Population
The CAMI registry is a prospective, multicenter study encompassing 107 hospitals across China. Between January 2013 and September 2014, it enrolled 26,591 patients diagnosed with acute myocardial infarction (AMI) based on the third universal definition of myocardial infarction. For this analysis, 12,145 patients with STEMI who underwent primary or selective percutaneous coronary intervention (PCI) were included. Patients were categorized into two groups: those presenting without typical chest pain (2,922 patients, 24.1%) and those with typical chest pain (9,223 patients, 75.9%). Typical chest pain was defined as precordial or retrosternal discomfort lasting >20 minutes, while atypical symptoms included sweating, abdominal pain, dyspnea, syncope, nausea, or vomiting.
Baseline Clinical Characteristics
Patients without chest pain exhibited distinct demographic and clinical profiles. They were older (mean age 61.0 vs. 59.7 years, P<0.01) and had a higher prevalence of diabetes (20.0% vs. 17.8%, P<0.01). Additionally, they experienced longer delays in seeking hospital care (P<0.01) and presented with higher Killip classification scores (P<0.01), indicating more severe hemodynamic compromise. Notably, 3.6% of atypical-presentation patients were in Killip class IV (cardiogenic shock) compared to 2.7% in the chest pain group.
Smoking patterns also differed: 48.0% of atypical-symptom patients were current smokers versus 52.7% in the typical-symptom group (P<0.01). Furthermore, atypical-presentation patients had lower systolic and diastolic blood pressures on admission (125.6/77.5 mmHg vs. 127.8/79.2 mmHg, P<0.01), suggesting compromised cardiovascular status.
Angiographic Findings
Coronary angiography revealed significant differences in lesion characteristics. Patients without chest pain had a higher proportion of infarct-related artery (IRA) involvement in the right coronary artery (RCA) (42.9% vs. 36.9%, P<0.01) and lower involvement of the left anterior descending artery (LAD) (44.6% vs. 51.2%, P<0.01). The mean thrombolysis in myocardial infarction (TIMI) flow grade was higher in the atypical-symptom group (1.00 vs. 0.94, P=0.02), indicating better initial coronary blood flow. Additionally, thrombus presence was less common in these patients (53.0% vs. 56.7%, P=0.01).
No significant differences were observed in the number of diseased vessels or left main coronary artery involvement. However, atypical-symptom patients had a slightly higher rate of graft lesions (0.2% vs. 0.03%, P=0.02), though this finding was based on very small numbers.
Management Patterns
Atypical-presentation patients received less aggressive evidence-based therapy during hospitalization. Rates of primary PCI were significantly lower (64.9% vs. 73.9%, P<0.01), as was the use of guideline-recommended medications:
- Aspirin: 97.4% vs. 98.0% (P=0.01)
- Thienopyridines: 97.9% vs. 98.5% (P<0.01)
- Statins: 97.5% vs. 98.0% (P<0.01)
- Heparin: 90.0% vs. 93.3% (P<0.01)
- Beta-blockers: 70.6% vs. 73.2% (P<0.01)
Conversely, atypical-symptom patients more frequently underwent elective PCI (45.7% vs. 37.3%, P<0.01) and received angiotensin-converting enzyme inhibitors/angiotensin receptor blockers (60.9% vs. 58.8%, P=0.01). These disparities suggest hesitancy in administering urgent reperfusion therapies to patients without classic symptoms, despite their higher-risk profile.
Clinical Outcomes
The in-hospital mortality rate was significantly higher in the atypical-symptom group (3.3% vs. 2.2%, P<0.01), as was 30-day mortality (4.1% vs. 2.8%, P<0.01). Complications such as cardiogenic shock (4.3% vs. 3.3%, P=0.01) and cardiac arrest (2.0% vs. 1.2%, P<0.01) were also more prevalent. After adjusting for confounders—including age, diabetes, Killip class, and treatment delays—atypical presentation remained an independent predictor of in-hospital mortality (adjusted odds ratio: 1.36, 95% confidence interval: 1.02–1.83).
Mechanistic Insights
The higher mortality risk in atypical-presentation patients cannot be attributed to “high-risk” angiographic features. Paradoxically, these patients had better initial coronary flow (higher TIMI grades) and less thrombus burden. Instead, the poor prognosis likely stems from:
- Baseline Vulnerabilities: Older age, higher diabetes prevalence, and delayed hospital presentation.
- Treatment Disparities: Lower rates of primary PCI and guideline-directed medical therapy.
- Atypical Symptom Recognition: Delayed diagnosis leading to advanced hemodynamic compromise upon arrival.
The predominance of RCA-related infarcts in atypical-presentation patients aligns with the known vagal activation patterns of inferior wall ischemia, which may manifest as nausea or abdominal pain rather than chest discomfort. Conversely, LAD lesions—associated with sympathetic activation—more frequently elicit classic anginal symptoms.
Clinical Implications
This study underscores the need for heightened vigilance in identifying STEMI patients without chest pain, particularly older adults and those with diabetes. Key recommendations include:
- Implementing rapid assessment protocols for patients with nonspecific symptoms (e.g., dyspnea, syncope).
- Standardizing ECG screening in high-risk populations regardless of symptom typicity.
- Addressing systemic biases in administering reperfusion therapies to atypical-presentation patients.
Limitations
The analysis focused solely on STEMI patients undergoing PCI, potentially excluding higher-risk individuals managed medically. Data on door-to-balloon times and detailed diabetic complications (e.g., neuropathy) were unavailable. Additionally, the observational design precludes causal inferences.
Conclusion
Nearly one-fourth of STEMI patients in China present without typical chest pain, facing a 50% higher risk of in-hospital death compared to symptomatic counterparts. Their adverse outcomes are driven by age, comorbidities, and therapeutic delays rather than angiographic severity. These findings call for paradigm shifts in prehospital triage, diagnostic protocols, and equitable access to life-saving interventions for atypical-presentation STEMI.
doi.org/10.1097/CM9.0000000000000432
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