NSTEMI Clinical Overview

I. The "On-Call" Snapshot

Clinical Significance in Malaysia: This is bread and butter for any medical department. You will see Non-ST-Elevation Acute Coronary Syndrome (NSTE-ACS) daily. It is a major cause of morbidity and mortality in our population due to the high prevalence of diabetes, hypertension, and dyslipidemia.

High-Yield Definition: NSTEMI is defined as myocardial necrosis (evidenced by a rise in cardiac troponins) in the absence of persistent ST-segment elevation on the electrocardiogram (ECG). It is a subtype of NSTE-ACS, which also includes Unstable Angina (where troponins are negative).

Clinical One-Liner: Basically, it's a heart attack where the artery is partially, but not completely, blocked. The ECG won't show the classic "tombstone" ST elevation, but the heart muscle is still being damaged, which is why the troponins go up.

II. Etiology & Risk Factors

Etiology: The primary cause is the rupture or erosion of an atherosclerotic plaque within a coronary artery. This triggers the formation of a platelet-rich, non-occlusive thrombus, leading to a reduction in downstream blood flow and myocardial ischemia.

Risk Factors:

• Non-Modifiable:

  • Age (Men >45 years, Women >55 years)

  • Male sex

  • Family history of premature coronary artery disease (CAD)

• Modifiable:

  • Hypertension (Very common in Malaysia)

  • Diabetes Mellitus (T2DM) (A major driver of atherosclerosis in our patients)

  • Dyslipidemia (High LDL, Low HDL)

  • Smoking

  • Obesity & Sedentary Lifestyle

  • Chronic Kidney Disease (CKD)

III. Quick Pathophysiology

An unstable atherosclerotic plaque ruptures, exposing its thrombogenic lipid core to the bloodstream. Platelets aggregate and the coagulation cascade is activated, forming a thrombus. In NSTEMI, this thrombus is substantial enough to cause downstream ischemia and myocyte necrosis, but not large enough to completely occlude the vessel. This subtotal occlusion is why you see ST depression or T-wave inversion (signs of subendocardial ischemia) rather than ST elevation (transmural ischemia). The resulting myocyte death releases cardiac troponins into the circulation, which we can detect in the blood.

IV. Clinical Assessment

Red Flags & Immediate Actions:

• Refractory/Ongoing Chest Pain: Alert senior, give nitrates, consider IV morphine, get repeat ECG.

• Hemodynamic Instability (SBP <90 mmHg): Alert senior immediately. This could be cardiogenic shock. Secure IV access, prepare for inotropes.

• Signs of Acute Heart Failure (e.g., bibasal crepitations, SpO2 <90%): Alert senior, sit patient up, give high-flow oxygen, prepare IV diuretics.

• Ventricular Arrhythmias or New High-Grade AV Block: Alert senior, get the defibrillator cart to the bedside, prepare for ACLS protocol.

History:

• Common (>50%): Retrosternal chest pain described as pressure, heaviness, or tightness, radiating to the left arm, neck, or jaw. Associated with diaphoresis, nausea, and dyspnea.

• Less Common (10-50%): Atypical presentations, especially in diabetics, elderly, and women. This includes epigastric pain, indigestion, or isolated shortness of breath.

• Pertinent Negatives: Actively ask to rule out differentials. Is the pain sharp and pleuritic (less likely ACS, more likely PE/pericarditis)? Does it radiate to the back (Aortic Dissection)? Is it associated with fever (Myocarditis)?

Physical Examination:

The physical exam can be unremarkable. Focus on finding signs of complications or high-risk features.

• General: Look for pallor, sweating, distress.

• Vitals: Tachycardia and hypertension are common due to sympathetic drive. Hypotension is a red flag.

• Cardiovascular: Listen for a new S3 gallop (LV dysfunction) or a new pansystolic murmur (acute mitral regurgitation from papillary muscle ischemia). Check for signs of heart failure (elevated JVP, pitting edema).

Clinical Pearl: An initial normal ECG and negative troponin do not rule out an evolving NSTEMI. The diagnosis often relies on the trend of serial ECGs and troponins. Always compare with an old ECG if available.

V. Diagnostic Workflow

Differential Diagnosis:

• STEMI:

  • Points For: Similar chest pain presentation.

  • Points Against: Absence of persistent ST-segment elevation.

  • How to Differentiate: The 12-lead ECG is the key. Repeat it if pain persists.

• Pulmonary Embolism (PE):

  • Points For: Acute dyspnea, chest pain.

  • Points Against: Pain is usually pleuritic. Risk factors for VTE (e.g., recent surgery, immobility).

  • How to Differentiate: CT Pulmonary Angiogram (CTPA) is the gold standard.

• Aortic Dissection:

  • Points For: Severe, sudden-onset chest pain.

  • Points Against: Pain is typically tearing and radiates to the back. Look for unequal blood pressure in both arms or a widened mediastinum on CXR.

  • How to Differentiate: CT Aortogram.

• Acute Pericarditis:

  • Points For: Retrosternal chest pain.

  • Points Against: Pain is sharp, pleuritic, and relieved by sitting forward. Widespread concave ST elevation on ECG.

  • How to Differentiate: Classic history and ECG findings.

Investigations Plan:

• Bedside / Initial (First 15 Mins):

  • 12-Lead ECG: Look for ST depression, T-wave inversions, or transient changes.

  • Cardiac Monitoring: To detect arrhythmias.

  • Vitals & SpO2.

• First-Line Labs & Imaging:

  • Cardiac Troponin I or T (hs-cTn): Send at 0 hours and repeat at 1-3 hours depending on the assay. A significant rise and/or fall pattern confirms myocardial necrosis.

  • Full Blood Count (FBC): To rule out anemia as a precipitating cause of ischemia.

  • Renal Profile (RP): Crucial baseline before starting ACE inhibitors and for contrast use during angiography.

  • Chest X-Ray (CXR): To look for cardiomegaly, pulmonary edema, or alternative diagnoses like a widened mediastinum.

• Confirmatory / Gold Standard:

  • The diagnosis is made clinically based on the combination of ischemic symptoms, ECG changes, and a characteristic rise and fall of cardiac troponins.

  • Coronary Angiography is the gold standard investigation to define coronary anatomy and plan for revascularization.

VI. Staging & Severity Assessment

We risk stratify NSTEMI patients to guide the timing of intervention. The GRACE Risk Score is the standard. You can use an online calculator.

• Key Components: Age, Heart Rate, Systolic BP, Creatinine, Killip Class, ST deviation, Elevated Troponins, Cardiac Arrest on admission.

• Impact on Management:

  • Low Risk (GRACE <109): Consider a conservative strategy or delayed invasive approach.

  • Intermediate Risk (GRACE 109-140): An early invasive strategy (angiogram within 24-72 hours) is indicated.

  • High Risk (GRACE >140): An early invasive strategy (angiogram within 24 hours) is strongly recommended.

  • Very High Risk (e.g., hemodynamic instability, refractory angina): Immediate invasive strategy (<2 hours).

VII. Management Plan

Immediate Stabilisation (The ABCDE Plan):

• Aspirin: 300mg stat (chewed and swallowed).

• P2Y12 Inhibitor (Dual Antiplatelet Therapy - DAPT):

  • Ticagrelor: 180mg stat loading dose, is preferred.

  • Clopidogrel: 300-600mg stat loading dose, if Ticagrelor is contraindicated or unavailable.

• Anticoagulation:

  • Fondaparinux: 2.5mg SC OD is the recommended agent as per ESC guidelines, especially if not proceeding to immediate PCI.

  • Unfractionated Heparin (UFH): IV bolus and infusion, used if an immediate invasive strategy (<2 hours) is planned.

• Anti-anginal Therapy:

  • Nitrates: Sublingual GTN spray or tablet. If pain persists, start an IV GTN infusion. Contraindicated if SBP <90 mmHg or recent sildenafil use.

  • IV Morphine: 2.5-5mg slow bolus for severe, refractory pain.

• Oxygen: Only if patient is hypoxic (SpO2 < 90%).

Definitive Treatment (The Ward Round Plan):

• Continue DAPT: Aspirin 100mg OD + Ticagrelor 90mg BD (or Clopidogrel 75mg OD) for up to 12 months.

• Beta-blocker: Start orally once hemodynamically stable (e.g., Bisoprolol 2.5mg OD or Metoprolol 25mg BD).

• High-Intensity Statin: Atorvastatin 80mg ON, start as early as possible.

• ACE Inhibitor/ARB: Start within 24 hours, especially if there is LV systolic dysfunction (LVEF <40%), heart failure, hypertension, or diabetes.

• Plan for Coronary Angiography and potential Percutaneous Coronary Intervention (PCI) based on the GRACE score.

Long-Term & Discharge Plan:

• Lifelong Aspirin and Statin.

• DAPT for up to 12 months post-PCI.

• Continue Beta-blocker and ACEi/ARB.

• Referral to Cardiac Rehabilitation.

• Aggressive risk factor management: smoking cessation, dietary advice, diabetic control (HbA1c <7.0%).

VIII. Complications

• Immediate (first 24-48 hours):

  • Arrhythmias (VT/VF): Management: Immediate defibrillation as per ACLS protocol.

  • Acute Left Ventricular Failure: Management: IV diuretics, nitrates.

  • Cardiogenic Shock: Management: Urgent revascularization, inotropic support.

• Short-Term (days to weeks):

  • Recurrent MI: Management: Re-evaluate for urgent angiography.

  • Acute Mitral Regurgitation: Management: Requires urgent surgical review.

  • Pericarditis (Dressler's Syndrome): Management: High-dose aspirin or colchicine.

• Long-Term (months to years):

  • Chronic Heart Failure: Management: Guideline-directed medical therapy.

  • Left Ventricular Aneurysm: Management: Anticoagulation if thrombus is present.

IX. Prognosis

Prognosis is highly variable and directly related to the GRACE score, baseline Left Ventricular Ejection Fraction (LVEF), the extent of coronary artery disease, and the success of revascularization.

• Top 3 Poor Prognostic Factors:

  1. Advanced Age

  2. Low LVEF

  3. Presence of Diabetes Mellitus and/or CKD

X. How to Present to Your Senior

Use the SBAR format. Be concise and direct.

"Dr., for review please. This is Mr. Lim in Bed 10, a 65-year-old man with a background of T2DM, who presented with 2 hours of central chest pain.

His ECG shows 2mm ST depression in the lateral leads. The first troponin has come back elevated at 500. He remains in pain despite GTN.

My main differential is a high-risk NSTEMI. His GRACE score is 155.

I have given him stat Aspirin 300mg and Ticagrelor 180mg, and started SC Fondaparinux. I would like to ask about starting an IV GTN infusion and referring him to the on-call cardiologist for an early invasive strategy."

XI. Summary & Further Reading

Top 3 Takeaways:

1. NSTEMI = Ischemic symptoms + Positive Troponin trend, without persistent ST elevation.

2. Immediate management is DAPT (Aspirin + Ticagrelor/Clopidogrel) + Anticoagulation (Fondaparinux/Heparin).

3. Risk stratify with the GRACE score. This dictates the urgency of referring for a coronary angiogram.

Key Resources:

• Malaysian CPG: Management of Non-ST Elevation Acute Coronary Syndrome (NSTE-ACS) 2021 (Link)

• International Guideline: 2023 ESC Guidelines for the management of acute coronary syndromes (Link)

• Clinical Tool: GRACE Score Calculator (MDCalc)

• Point-of-Care Reference: UpToDate - "Acute coronary syndrome: Terminology and classification" and "Initial evaluation and management of suspected acute coronary syndrome".