Medicine Marrow Pg No 427-436 (ECG)

Proximal Left Coronary Artery (LCA) Occlusion

• Proximal LCA occlusion leads to ST elevation in the AVR lead and ST depression in all other leads.
• Without treatment, mortality is 100%.
• Treatment involves immediate percutaneous coronary intervention (PCI).

Acute Coronary Syndrome (ACS) - Coronary Circulation

• The provided image likely shows an ECG tracing.
• The ECG pattern indicates proximal LCA occlusion.

Complications of Acute Wide Myocardial Infarction (AWMI)

• Left ventricular (LV) involvement can cause ventricular tachycardia (V-tach), ventricular fibrillation (V-fib), and sudden cardiac death.
• Mechanical complications include external cardiac rupture and septal rupture.
• Infra-hisian blocks can occur.

Chest Pain Characteristics

• Radiation of chest pain to the right arm or shoulder has a positive likelihood ratio of 4.7.
• Radiation to both arms or shoulders has a positive likelihood ratio of 4.1.
• Chest pain associated with exertion has a positive likelihood ratio of 2.4.
• Radiation to the left arm has a positive likelihood ratio of 2.3.
• Chest pain associated with diaphoresis has a positive likelihood ratio of 2.0.
• Chest pain associated with nausea or vomiting has a positive likelihood ratio of 1.9.
• Chest pain worse than previous angina or similar to a previous myocardial infarction (MI) has a positive likelihood ratio of 1.8.
• Chest pain described as pressure has a positive likelihood ratio of 1.3.

Angina Equivalents

• Dyspnea, fatigue, diaphoresis, and atypical site pain can be equivalents of angina.

Management of Chest Pain

• Pre-Coronary Care Unit (CCU): Morphine for sedation. 1-month mortality rate: 30%.
• CCU: Beta-blockers, defibrillator. 1-month mortality rate: 15%.
• Reperfusion (Since 1975): Thrombolysis, percutaneous intervention. 1-month mortality rate: 5%.

ST Elevation Myocardial Infarction (STEMI)/ST-Elevation Acute Coronary Syndrome (STE-ACS)

Salient Features

• The provided image shows diagrams illustrating the progression of myocardial infarction at different time points.
• The diagrams highlight the affected arteries: Left anterior descending artery (LAD), Right coronary artery (RCA), and Left circumflex artery (LCX).

Progression of Myocardial Damage

• The first 6 hours are considered the "golden hours".
• After 6 hours of chest pain onset, only 1/6th of the myocardium remains viable.

Mortality Reduction

• A graph showing the rapid decline in survival rate after time zero highlights the critical importance of timely treatment.

Potential Outcomes

• Outcomes are categorized into benefit (A-C, B-C) and harm (E-D).

Extent of Salvage

• A graphic demonstrates the importance of rapid artery opening through PCI or lysis.
• The x-axis represents time in hours, and the y-axis represents the extent of salvage.

Reperfusion (PCI)

• Myocardium can be salvaged before 6 hours of coronary artery occlusion.
• After 6 hours, PCI can reduce pain, prevent electrical complications, and prevent mechanical complications.

Diagnosis: ECG Changes

• ST Elevation: Leads II, III, AVF
• Reciprocal Change: Leads V1, V2, V3
• RCA: ST elevation in lead III > lead II, ST depression in AVL > AVR
• Proximal: ST depression in V1 discordant to V2, V3
• Wrap around phenomenon: RCA supplies all regions

Note: LCX Occlusion

• Left ventricle wall motion abnormalities (LWM1) + Posterior wall motion abnormalities (PWM1)
• ST elevation in lead II > lead III
• In left-dominant circulation, if LCX supplies the lateral wall, LWM1 may be present.

Papillary Muscle Rupture → 2° MR

• Occurs post-LWM1 PCI with congestive heart failure (CCF).
• Presents with LV S3, absence of murmur.
• Ejection fraction (EF): Good.
• Normal or near-normal ECG.

Left Coronary Circulation

Left Coronary Artery (LCA)

Left Circumflex Artery (LCX)

• Branches: D (high lateral wall), S (septal wall), Da (anterior wall), D3 (lateral wall), D (diagonal), S (septal)

Left Anterior Descending Artery (LAD)

• Site: Left anterior interventricular sulcus
• ECG Leads:
  • Anterior: V1, V2, V3 (LAD)
  • Lateral: V5, V6 (LAD/LCX)
  • High Lateral: I, AVL (LAD/LCX)
  • Septal: V1 >> V2 (LAD)
  • Apical: V4

ECG Interpretation

• Antero-septal high lateral MI: V2, V3, V4 ST elevation (LAD), I, AVL ST elevation (before D1), wrap around phenomenon (V2, V3, V4 ST elevation above Da, V1 no elevation below S2, V5, V6 ST elevation wrap around)
• Anteroseptal MI: V1, V2 ST elevation (above S2), I, AVL ST depression (between D1 and S2)
• Anterolateral MI: Anatomical S2 before D1, Occlusion between S2 and D1

Diagnosis: ECG Changes

• Diagnosis: Reinfarction (within 28 days)
• Reinfarction: Two troponin values immediately and 3-6 hours later that are greater than a 20% increase.

Underlying Pathologies of Culprit Coronary Lesion

• Plaque Rupture: 60-70% (most common), men, associated with elevated cholesterol
• Plaque Erosion: 30-40%, female, young, associated with smoking

Characteristics of Vulnerable Plaques

• Thin cap, necrotic lipid core (greater than 40%), increased macrophage infiltration, decreased smooth muscle cell content, spotty calcification

Hibernating and Stunned Myocardium

• Hibernating Myocardium: Chronic setting, viable tissue (MRI should be done for evaluation), decreased function due to low perfusion.
• Stunned Myocardium: Acute setting, seen post-ischemia, viable tissue, restore perfusion for few hours.

Diagnosis

• ECG: Used to diagnose reinfarction.

ACS - Evaluation & Management

Definition

• Universal definition of MI (2018): Obsolete terms: fixed plaque, rupture, fibrin-rich thrombus, platelet-rich thrombus. Critical occlusion, incomplete occlusion.
• STEMI/STE-ACS --> NSTE-ACS
• Normal enzyme: Unstable angina
• Raised enzyme: NSTEMI

a. Myocardial Injury

• Cardiac Troponin T/I: ≥ 1 value above 99th percentile with acute rise and fall.
• Other causes of ↑ troponin level:
  • Cardiac: Myocarditis, Takotsubo cardiomyopathy, defibrillator shocks, increased oxygen demand (tachyarrhythmia), decreased oxygen supply (spasm, embolism, dissection).
  • Non-Cardiac: Sepsis, subarachnoid hemorrhage, chronic kidney disease, critically ill patients, pulmonary embolism.

Current Universal Definition - ACS/Acute MI:

Myocardial injury + ½ clinical evidence of myocardial ischemia.

Types and Clinical Features

• Type 1: Athero-thrombotic occlusion (most common)
• Type 2: Demand/supply mismatch (ICU patients, Severe anemia)
• Type 3: Sudden cardiac death
• Type 4: Post percutaneous coronary intervention
• Type 5: Post coronary artery bypass graft

Ultrasensitive Troponin Assays

• Can detect enzyme elevation levels as low as 0.0ng/mL.

TYPE I MI

• Possible triggers: Atherosclerosis + thrombosis, plaque rupture, plaque erosion.

TYPE 2 MI

• Possible causes: Oxygen supply and Demand imbalance, severe hypertension, sustained tachyarrhythmia.

TYPE 3 MI

• Possible causes: Oxygen supply and demand imbalance, acute heart failure, myocarditis.

Chronic MI

• Possible causes: Structural heart disease, chronic kidney disease.

Determinants of Salvageable Myocardium

• Collaterals, myocardial oxygen demand, ischemic preconditioning.

Target Time in STEMI (European Society of Cardiology)

• Chest pain → First medical contact (FMC) (should be < 10 min)
• Diagnosis → Availability of 24-hour PCI center
• YES (Diagnosis to Wire Crossing Time < 60 min): Wire crossing done within 90 min (+ 30 min for patient transfer)
• NO (Diagnosis to Wire Crossing Time >= 60 min): Thrombolysis within 10 min (Tenecteplase or Reteplase), transfer patient to PCI center, check for ST resolution after 60-90 min (successful > 70% resolve, unsuccessful < 70% resolve (Rescue PCI / Emergency PCI))
• Pharmacoinvasive approach: Successful thrombolysis within 2-24 hours, prevents recurrence of thrombus formation.
• First medical contact personnel: Medical/Paramedic staff, take & interpret ECG, can use defibrillator.

b. Clinical evidence of myocardial ischemia.

• Symptoms
• New ECG changes.
• Development of pathological Q waves.
• Imaging evidence (New RWMA).
• Angiography evidence (Coronary thrombus).

Localization

• Before D1, between D1 and S2, below S2.

Course

• Enters the Posterior interventricular sulcus.
• Terminates at anastomosis with PDA.
• Wrap around phenomenon: Inferior wall.

ECG

• Deterinants of salvageable myocardium: Collaterals, Myocardial oxygen demand, Ischemic preconditioning.
• Note: Reopening the artery is more important than the mode of reperfusion.

ECG Wave Form Descriptions

• ECG traces, labeled with different leads (e.g., I, II, III, aVR, aVL, aVF, V1-V6), showing ST depression, appear as waves and deflections on a grid.

NSTEMI (Non-ST-Elevation Myocardial Infarction)

• Features: Rest angina lasting more than 20 minutes, new onset severe angina, crescendo pattern of angina, ST depression and T wave inversion, elevated cardiac troponins.
• Clinical presentation: Age group 40-50 years (50-60 years in other regions), predominance of females over males in patients from locations outside India, vague symptoms in females are a common presentation, absence of typical chest pain in patients with diabetes.
• TIMI score: Used to determine mortality risk in NSTEMI cases.

This quiz tests your knowledge on proximal left coronary artery occlusion, its complications, and the characteristics of associated chest pain. Understand the implications of acute coronary syndrome and the importance of timely intervention.