Introduction
The Pitt — Episode 3, debrief after Mr. Milton's death:
"What was his discharge diagnosis?" — Resident
"Unstable angina. Coronary artery disease." — Dr. Robby
"But he had a HEART score of three. 1% chance of an adverse event." — Resident
"And he was in the 1%." — Dr. Robby
Mr. Milton came into the emergency department with abdominal pain that looked like gallstones. He was discharged as low-risk. And he died from unstable angina before reaching outpatient follow-up.
This case — fictional but clinically precise — illustrates what makes unstable angina so dangerous: it can present atypically, with normal tests and low risk scores, and still be fatal. Understanding what it is, how it differs from other coronary syndromes, and why it is considered a potential emergency even when it does not appear to be is fundamental for both physicians and patients.
What is Unstable Angina?
Unstable angina is an acute coronary syndrome caused by a critical reduction in blood flow in a coronary artery, generally from rupture of an atherosclerotic plaque with formation of a partially obstructive thrombus — without reaching the complete occlusion that defines infarction.
It sits on the spectrum between stable angina and acute myocardial infarction:
- Stable angina: predictable ischemic pain with exertion, relieved by rest or nitroglycerin. Caused by fixed coronary stenosis without plaque rupture.
- Unstable angina: ischemic pain at rest, of recent onset, progressive, or more intense than usual. Caused by plaque rupture with partial thrombus.
- NSTEMI: unstable angina with troponin elevation — confirmed myocardial necrosis by biomarker, even without ST elevation.
- STEMI: complete occlusion with ST elevation and evolving transmural necrosis.
The distinction between unstable angina and NSTEMI depends exclusively on troponin: if elevated, it is NSTEMI; if normal, it is unstable angina. Clinically, both conditions are treated similarly — both are non-ST-elevation acute coronary syndromes (NSTE-ACS).
In Mr. Milton's case, troponin was normal and the ECG showed no changes — defining unstable angina, not NSTEMI. The underlying real risk — unstable plaque with non-occlusive thrombus — was present but biologically silent on available tests.
Causes and Clinical Context
The pathophysiology of unstable angina is the same as myocardial infarction: rupture of a vulnerable atherosclerotic plaque with exposure of lipid contents to blood, platelet activation, and thrombus formation. The difference is that the thrombus is non-occlusive — it critically reduces flow but does not completely interrupt it.
Main precipitating factors include:
- Sudden increase in myocardial demand from exertion, emotional stress, or infection
- Coronary vasospasm over an unstable plaque
- Spontaneous plaque rupture with fragment embolization to the distal microcirculation
Risk factors are the same as STEMI: hypertension, hyperlipidemia, smoking, diabetes, obesity, and family history. In Mr. Milton's case, the presentation with abdominal pain — rather than typical chest pain — is a classic example of an ischemic equivalent: myocardial ischemia expressing atypical symptoms that mimic non-cardiac conditions.
Signs and Symptoms
Unstable angina can present in three main clinical forms:
- Rest angina: episodes of chest pain or discomfort occurring without physical exertion — generally more prolonged than stable angina and less responsive to nitroglycerin
- New-onset angina (de novo): angina appearing in the past 4 to 8 weeks in a previously asymptomatic patient, with a low exertion threshold
- Progressive angina: prior stable angina that has become more frequent, more intense, or triggered by lesser exertion
Atypical presentations — common in the elderly, diabetics, and women:
- Epigastric or upper abdominal pain — as in Mr. Milton's case
- Isolated dyspnea without chest pain
- Unexplained fatigue or generalized weakness
- Jaw, neck, arm, or back pain without retrosternal pain
- Nausea and vomiting without apparent cause
Diagnosis
Diagnosis of unstable angina requires active exclusion of NSTEMI and STEMI:
12-lead ECG: may be normal — as with Mr. Milton — or show ST depression, T wave inversion, or transient changes during symptoms. Absence of changes does not exclude the diagnosis.
Serial troponin: collected on arrival and after 3 to 6 hours. Normal in both collections = unstable angina (no necrosis). Elevated = NSTEMI.
HEART score: risk stratification tool combining history, ECG, age, risk factors, and troponin. Score 0 to 3 = low risk (<2% event at 30 days). In Mr. Milton's case, score 3 with atypical abdominal pain that underestimated the real underlying risk.
Stress testing or functional imaging: indicated in low and intermediate risk patients before discharge, to identify inducible ischemia that guides the need for elective catheterization.
Emergency Treatment
Unstable angina emergency treatment is directed at stabilizing the plaque, inhibiting platelet aggregation, and relieving ischemia:
- Chewable aspirin 162–325 mg: immediate antiplatelet therapy — reduces risk of progression to infarction
- P2Y12 inhibitor: ticagrelor or clopidogrel — dual antiplatelet therapy
- Anticoagulation: unfractionated heparin or subcutaneous enoxaparin
- Nitrates: sublingual or IV nitroglycerin for ischemic pain relief
- Beta-blockers: reduce heart rate and myocardial oxygen demand
- High-intensity statins: plaque stabilization and residual risk reduction
High-risk patients (HEART score 7–10, rising troponin, hemodynamic instability, or recurrent ischemia) should be referred for urgent catheterization within the first 2 to 24 hours.
Low-risk patients — like Mr. Milton — may be discharged with early outpatient follow-up, stress testing or coronary CT angiography, and instructions for immediate return if symptoms worsen.
Prognosis and Complications
Unstable angina carries variable risk depending on stratification:
- Low risk (HEART 0–3): less than 2% adverse event at 30 days — but not zero, as demonstrated by Mr. Milton's case
- Intermediate risk (HEART 4–6): 12 to 16% adverse event risk
- High risk (HEART 7–10): above 50% — urgent catheterization indicated
Main complications of untreated unstable angina include:
- Progression to NSTEMI or STEMI from complete thrombus occlusion
- Ventricular fibrillation and sudden cardiac death from electrical ischemia
- Acute heart failure from ischemic ventricular dysfunction
- Death — as occurred with Mr. Milton, within the statistical 1% low-risk window
Frequently Asked Questions
Are unstable angina and heart attack the same thing?
No, but they are on the same spectrum. A heart attack implies confirmed myocardial necrosis — dead cardiac cells, marked by troponin elevation. Unstable angina is critical ischemia without necrosis — the cardiac muscle is in distress but not yet dying. This distinction is biologically important, but clinically, both are emergencies requiring immediate evaluation and antiplatelet therapy.
Why can unstable angina pain be abdominal?
Cardiac innervation shares pathways with the nerves that innervate the upper abdomen. When the heart becomes ischemic, the pain stimulus can be interpreted by the brain as originating in the abdomen — especially the epigastrium or right upper quadrant, mimicking biliary colic or gastritis. This phenomenon — called referred pain — is why every abdominal pain in a patient with cardiovascular risk factors should include an ECG in the initial evaluation.
How do I know if chest pain is unstable angina or something else?
Evaluation requires a 12-lead ECG, serial troponin, and detailed clinical history. Features that increase suspicion of ischemic origin include: retrosternal pressure or tightness, radiation to the left arm or jaw, duration above 20 minutes, association with diaphoresis or dyspnea, and presence of cardiovascular risk factors. The HEART score integrates all these elements to guide clinical decision-making.
Can unstable angina be treated with medication only, without catheterization?
In low-risk patients, yes — medical treatment with antiplatelet therapy, anticoagulation, and beta-blocker is sufficient as initial management, with subsequent stratification by stress testing or imaging. In high-risk patients or those with recurrent ischemia, catheterization is necessary to identify and treat the culprit lesion. The decision is individualized based on risk stratification and clinical evolution.
Conclusion
Unstable angina is the diagnosis Episode 3 of The Pitt uses to remind us that medicine is probability — not certainty. Mr. Milton was within the 2% the protocol considers safe for discharge. But protocols are built for populations, not individuals. Recognizing atypical presentations, questioning the score when clinical intuition signals something different, and ensuring close follow-up are what separate a protocol followed from a patient saved.
Explore more in our Medical Terms category. Also read about the HEART score, STEMI, chewable aspirin in cardiac emergency, and the cardiac monitor.
Disclaimer: This content is for educational purposes only and does not substitute professional medical evaluation, diagnosis, or treatment. In case of emergency, call 911 immediately.
