ACS Risk Factors and ECG Interpretation

ACS Risk Factors

  • Important to recognize risk factors for ACS (Acute Coronary Syndrome).

  • Age:

    • Women over 55.

    • Men over 45.

  • High blood pressure or high cholesterol.

  • Diabetes: increases risk of vascular disease due to vessel narrowing.

  • Unhealthy lifestyle.

  • Family history of ACS.

ACS Presentation

  • Classic symptoms:

    • Chest pain.

    • Jaw pain.

  • Atypical symptoms:

    • No chest pain can also be a symptom.

    • Nausea.

    • Weakness.

  • Silent MI: symptoms that aren't chest pain related.

  • Levine's sign: clutching chest.

Pertinent Negatives for ACS

  • Shortness of breath.

  • Nausea.

Angina

  • Chest pain or discomfort when the heart doesn't get enough oxygen.

  • Symptom, not a disease.

  • Usually caused by CHD (Coronary Heart Disease) or CAD (Coronary Artery Disease).

  • Types:

    • Stable Angina:

      • Chest pain upon exertion that resolves with rest.

      • Predictable.

      • Usually indicates 70-85% blockage in coronary artery.

    • Unstable Angina:

      • Does not resolve with rest or nitroglycerin.

      • Considered ACS.

      • Chest pain at rest indicates about 90% blockage.

      • Chest pain after nitroglycerin usually indicates nearly 100% blockage.

    • Prinzmetal/Variable Angina:

      • Blood vessel spasms, causing narrowing.

      • Can occur at rest.

      • May resolve with nitro or on its own.

Vitals with ACS

  • Vitals can vary widely.

    • Tachycardia or bradycardia.

    • Hypertension or hypotension.

    • Do not rule out ACS based solely on vitals.

ECG and ACS

  • An EKG never rules out ACS. It only rules it in.

  • EKGs are only about 50% sensitive.

  • Non-MI conditions can mimic MIs on an ECG.

  • EKGs are highly specific (if it shows STEMI, it's likely there).

  • EKGs can identify MIs quickly, unlike labs like troponin.

  • EKGs can reveal other complications or blockages.

ST Segment Elevation

  • Identify J point (end of QRS complex).

  • Measure one small box over from the J point to assess ST segment elevation.

Measurements that matter:

  • 1 mm elevation is significant in all leads except V1, V2, and V3.

  • In V1, V2, V3, at least 2 mm of elevation is needed.

  • Elevation must be present in two or more related leads (anatomically).

STEMI

  • If elevation is only present in lead two need additional confirmation in lead AVF.

Related Leads

  • v1, v2 is the Septum.

  • v3, v4 is the anterior.

ECG Limitations and Benefits

  • Limitations:

    • Only about 50% sensitive (may miss some MIs).

    • Non-MI conditions can mimic MIs.

  • Benefits:

    • Highly specific (if STEMI is present, it's likely accurate).

    • Quick identification compared to lab tests.

    • Can identify other complications.

I See All Leads

  • Inferior (II, III, aVF).

  • Septal (V1, V2).

  • Anterior (V3, V4).

  • Lateral (I, aVL, V5, V6).

Reciprocal Changes

  • ST depression in some leads when ST elevation is present in others.

  • Not present in septal or anterior MIs.

  • Lateral STEMI often has inferior reciprocal changes.

  • Inferior STEMI often has lateral reciprocal changes.

  • Posterior involvement:

    • May see T-wave inversion in V1-V3.

    • Consider with inferior STEMI.

Checking for Right Ventricular Involvement

  • Move V4 lead to the right side of the chest (V4R).

  • Elevation in V4R indicates right ventricular infarction.

  • Hold nitroglycerin if right ventricular involvement is present.

Posterior Involvement

  • Move V5 and V6 leads to beneath the scapula (V8 and V9).

  • Elevation there suggests posterior involvement.

15-Lead ECG

  • Combine standard 12-lead with V4R, V8, and V9.

Fluid Administration

  • In general, avoid fluid boluses in STEMI patients unless hypotensive.

Inferior MI Considerations

  • About 50% of MIs are inferior.

  • Posterior and/or right ventricular involvement is common.

  • Hold nitro if right ventricular involvement is present.

Pathological Q Waves

  • Downward deflection at the start of the QRS complex.

  • Indicates past infarction (dead tissue).

  • Pathological if more than one small box wide or more than one-third the height of the R wave.

  • ST segment elevation with pathological Q waves indicates ongoing injury and death.

  • Location of Q waves indicates the area of tissue death.