Coronary Artery Disease — Obsidian Note

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Overview (1 paragraph)
This lecture frames coronary artery disease as a spectrum centered on chest pain, moving from asymptomatic CAD → stable angina → unstable angina → NSTEMI → STEMI. It then walks through how to spot ACS using history/risk factors/symptoms/physical exam, how to work up chest pain (rule out STEMI first with 12-lead EKG, then NSTEMI with troponins, then consider stress testing), what makes a stress test “positive” (especially via echo/nuclear looking for reversible abnormalities), how cath results drive next steps (CABG vs stent), and finishes with initial ACS medical therapy (MONA BASH C) plus what patients typically go home on.

Key takeaways (5–10)

• CAD spectrum: asymptomatic → stable angina → unstable angina → NSTEMI → STEMI.
• Differentiate categories by: what brings pain on, what relieves it, biomarkers, ST-segment changes, and % occlusion (roughly).
• STEMI = supply ischemia / total occlusion → urgent cath emergently.
• Stable/unstable angina + NSTEMI = demand ischemia (not total occlusion) → can improve if reduce demand.
• Spot ACS using: HPI + risk factors + associated symptoms + physical exam.
• Diamond classification (3 features) → labels: typical (3/3), atypical (2/3), non-anginal (0–1/3).
• Chest pain workup: EKG → troponins (troponin best generally; CKMB for reinfarction) → stress test if ruled out.
• Stress testing: pick stress modality (exercise vs pharmacologic) + evaluation modality (EKG vs echo vs nuclear).
• Cath outcome guides: ≥3 vessels or big proximal disease → CABG; otherwise often stent/angioplasty (with caveats).
• Initial treatment mnemonic: MONA BASH C; discharge “core 4”: beta-blocker + ACE inhibitor + aspirin + statin (per transcript).

Common traps / misunderstandings

• “Atypical chest pain” ≠ “doesn’t sound cardiac”; it means 2/3 of the diamond criteria.
• Unstable angina isn’t simply “pain at rest”; it can be worsening stable angina (less exertion triggers / more pain with same exertion).
• Troponins are not useful for reinfarction if already elevated; use CKMB.
• Don’t jump straight to “unstable angina” after negative EKG/troponin; ask: is this ischemia at all? → stress test.
• No nitrates in right-sided MI (transcript: “preload dependent”).

00:00 — What CAD “is about”: the spectrum of chest pain

Core idea
CAD is taught as a spectrum; organize it by what triggers/relieves pain, biomarkers, ST changes, and roughly % occlusion.

Mechanism / reasoning chain

1. CAD ranges from no symptoms to angina to infarction.
2. As you move rightward on the spectrum, occlusion increases, and risk/acuity increases.
3. Key differentiators:
   • Bring-on (exertion vs rest)
   • Relief (rest/nitro vs nothing)
   • Biomarkers (elevated vs not)
   • ST changes (present vs not)

Clinical implications

• Use the spectrum to quickly classify chest pain presentations.
• Don’t “treat the label”; treat what it implies about damage and urgency.

Table: CAD Spectrum Organizer ([diagram described])

02:56 — Supply vs demand ischemia (how the spectrum “works”)

Core idea

• STEMI = supply ischemia: “no matter how low the demand, there is no supply.”
• NSTEMI/unstable/stable = demand ischemia: not totally occluded; lowering demand can reverse/avoid worsening.

Mechanism / reasoning chain

1. STEMI: total occlusion → no supply → myocardium “will die one way or another” unless reopened.
2. NSTEMI/unstable/stable: partial occlusion → some supply persists.
3. If you reduce workload, oxygen demand falls and “what little perfusion they have is sufficient” to reverse damage/avoid progression.
4. These become symptomatic with exertion because workload increases; unstable/NSTEMI can occur at rest because occlusion is larger and “approaching STEMI.”

Clinical implications

• STEMI logic pushes you toward immediate revascularization.
• Demand ischemia logic frames why reducing demand helps.

04:30 — Spotting ACS: what elements to use

Core idea
To spot ACS, use: HPI, risk factors, associated symptoms, physical exam.

Mechanism / reasoning chain

1. Start with the presenting illness (chest pain characterization).
2. Layer in risk factors (modifiable + nonmodifiable).
3. Add associated symptoms to raise pre-test probability.
4. Use exam clues to support ischemic vs non-ischemic pain patterns.

Clinical implications

• The transcript frames this explicitly as building pre-test probability.

05:02 — Diamond classification for angina

Core idea
Three features; count them and label correctly.

Diamond criteria (as stated)

1. Substernal or left-sided chest pain
2. Worsened with exertion and relieved with rest
3. Relieved by nitroglycerin

Classification

• 3/3 → Typical angina
• 2/3 → Atypical angina
• 0–1/3 → Non-anginal

05:57 — Risk factors + associated symptoms + exam clues

Core idea
Risk factors are “those that go with any vascular disease,” plus nonmodifiable factors.

Risk factors (modifiable)

• Diabetes
• Smoking
• Hypertension
• Dyslipidemia
• Obesity

Risk factors (nonmodifiable)

• Family history (early CAD / early death from MI)
• Age: >45 (man), >55 (woman)

Associated symptoms that raise pre-test probability (as stated)

• Presyncope
• Nausea/vomiting

Physical exam pain pattern for ischemia (as stated)

• Non-pleuritic (deep breath doesn’t worsen)
• Non-positional (leaning forward/back doesn’t change)
• Non-tender / not reproducible with palpation

07:24 — Chest pain workup: rule out the worst first

Core idea
Approach is an acuity ladder: rule out STEMI, then NSTEMI, then assess ischemia at all.

Algorithm ([diagram described])

Chest pain →
  1) 12-lead EKG →
      If ST elevations → Cath (emergent; tight time window)
      Else →
  2) Troponins →
      If elevated → Cath (urgent; this admission, not necessarily immediate)
      Else →
  3) Ask: "Is this coronary ischemia at all?" →
      Stress test →
        If positive → Cath (elective; may go home + follow-up)

Troponin vs CKMB (as stated)

• Troponin: “peaks first” and “lasts” → good for new ER presentation.
• Reinfarction: troponins “go up and stay up” → use CKMB if troponins already elevated.

09:06 — Unstable angina nuance (the “I lied a little bit” part)

Core idea
Unstable angina is more complex than just “pain at rest.”

Definition cues (as stated)

• “Same chest pain that occurs with less exertion” OR
• “More pain with the same amount of exertion”
• “Any worsening of stable angina makes it unstable.”

Implication (as stated)

• Even with no ST elevation and no troponin rise, unstable angina patients “need to go to the cath lab.”

10:31 — Stress testing: two knobs (stress modality + evaluation modality)

Core idea
A stress test is chosen by:

1. How you stress (raise heart rate / demand)
2. How you evaluate (what you measure/see)

Stress modality (as stated)

• Exercise (preferred if patient can walk/treadmill)
• Pharmacologic (“farm”): adenosine or dobutamine (examples given)

When to use pharmacologic (as stated): if unable to exercise due to e.g. arthritis, diabetic foot ulcer, amputation, feet hurt, doesn’t want to, etc.

Evaluation modality (as stated)

• EKG
• Echo (“EECO”)
• Nuclear

Selection rules (as stated)

• Use EKG when baseline EKG is normal
• If baseline EKG is not normal, use Echo
• If previous CABG or heart failure, use Nuclear

12:17 — How echo/nuclear stress tests detect risk: “dead things don’t move”

Core idea
Echo/nuclear evaluation relies on motion/viability logic: normal vs at-risk vs dead (scar), assessed at rest and stress.

Mechanism / reasoning chain

1. Tissue categories (as stated):
   • Normal tissue
   • Tissue at risk
   • Dead tissue (scar)
2. “Dead things don’t move.”
3. Under stress, at-risk tissue experiences “myocardial stunning” and temporarily doesn’t move → looks dead under stress.
4. Reversibility (moves at rest, doesn’t move under stress) = “positive stress test.”

Table: Motion pattern under rest vs stress ([diagram described])

Key terminology note (as stated)

• “No akinesia, no dyskinesia, they mean the same thing.” speaker claims equivalence; keep as stated

Clinical implication (as stated)

• Reversibility suggests if you intervene on the coronary vessel, you can “push it back to normal”; otherwise may “progress towards full infarct.”

14:11 — Why cath matters: deciding CABG vs stent

Core idea
Cath “tells you what you do next,” mainly based on number of vessels + how big/proximal.

Decision rules (simplified as stated)

1. 3 or more vessels involved → CABG
2. 1–2 vessels → stent with angioplasty
3. Caveats (as stated):
   • Single-vessel disease can still get bypass if big proximal arteries (left main, LAD, left circumflex) are involved.
   • Multi-vessel disease far “off in the distance” might still get many stents.
4. Key lesson: “3+ vessels or really big/proximal → surgery; otherwise stent.”

15:27 — Immediate ACS treatment when they “hit the door”: MONA BASH C

Core idea
Before the definitive pathway completes, you start medical therapy using mnemonic MONA BASH C.

Mnemonic (as stated)

• Morphine
• Oxygen
• Nitrates
• Aspirin
• Beta-blocker
• ACE inhibitor
• Statin
• Heparin (therapeutic)
• Clopidogrel (or other antiplatelet: prasugrel/ticagrelor mentioned)

What else to decide (per transcript)

• Nitrates: for someone who “continually has angina” / still chest pain.
• Clopidogrel: if they get a stent.
  • Drug-eluting stent: 1 year
  • Bare metal stent: 1 month
  • No stent, just angioplasty: no clopidogrel
• Acute setting decisions:
  • Therapeutic “lovenox/heparin” + clopidogrel load if NSTEMI or high pretest probability.
  • If just a rule-out / low probability, may not need that escalation.

Morphine + oxygen nuance (as stated)

• If you “have to use morphine” to control pain, “mortality increases” (doesn’t mean never give; indicates worse outcomes).
• Oxygen: speaker coaches “everyone gets a little bit” initially (nasal cannula), avoid excessive oxygen toxicity; can remove if sats 100% without it.

18:25 — Thrombolysis (TPA) vs PCI: timing thresholds

Core idea
TPA is framed as useful when PCI access is limited (rural/transport).

Timing rules (as stated)

• Door-to-balloon time: 90 minutes (cath lab balloon inflated within 90 min)
• If giving TPA: 60 minutes
• If transport time to a PCI-capable center > 60 minutes, give TPA.

19:33 — Practical “when do you give what and why?”

Core idea
Simple door-level actions and rationale.

Speaker’s “straight up” rules

• If someone has chest pain → give aspirin.
• If already has CAD and already on aspirin → try nitrate to see if it helps (pain relief supports coronary ischemia), then decide stable vs unstable.

Which home meds to prioritize early (as stated)

• Choose beta-blocker (after aspirin) because:
  • Patients die of ventricular arrhythmias in first 24 hours.
  • Beta-blockers reduce ventricular arrhythmia and reduce workload (demand).

Other rationale notes (as stated)

• Statins: plaque/cholesterol “cause of disease.”
• ACE inhibitors: reduce BP and prevent remodeling.

Critical caveat (as stated)

• Right-sided MI (2–3 aVF with ST elevations) → no nitrates; RV is “preload dependent.”

Memory Hooks

• MONA BASH C (explicit mnemonic in transcript)
• No other explicit mnemonics stated.

Exam / UWorld triggers (phrases framed as “if you see X → think Y”)

• “Spectrum from asymptomatic CAD → stable angina → unstable angina → NSTEMI → STEMI.”
• “ST elevation on EKG → go to cath emergently.”
• “No ST elevation → check troponins.”
• “Reinfarction → don’t recheck troponins, check CKMB.”
• “After ruling out STEMI/NSTEMI → ask is it ischemia at all? → stress test.”
• “Echo/nuclear: dead things don’t move; reversibility = positive stress test.”
• “3+ vessels or big proximal disease → CABG; otherwise stent.”
• “Right-sided MI (2–3 aVF ST elevation) → no nitrates.”

End-of-note recap

Ultra-short summary (≤8 lines)
CAD is organized as a chest-pain spectrum with increasing occlusion and acuity. Differentiate entities by trigger/relief, biomarkers, and ST changes. In chest pain workup: rule out STEMI with EKG (ST elevation → emergent cath), then NSTEMI with troponins (CKMB for reinfarction), then ask if ischemia at all (stress test). Stress tests pair stress modality (exercise vs pharmacologic) with evaluation modality (EKG/echo/nuclear), and echo/nuclear look for reversible abnormalities (“dead things don’t move”). Cath findings guide CABG vs stent. Start ACS meds using MONA BASH C and ensure core discharge meds (BB/ACEi/ASA/statin) per transcript.

Checklist (what to remember)

• CAD spectrum + rough occlusion % + ST/biomarker patterns
• Supply ischemia (STEMI) vs demand ischemia (others)
• Diamond classification: 3 criteria + typical/atypical/non-anginal labels
• Chest pain workup ladder: EKG → troponin/CKMB → stress test → cath timing (emergent/urgent/elective)
• Stress test selection rules (baseline EKG; prior CABG/HF)
• Reversibility concept for echo/nuclear stress tests
• Cath: 3+ vessels or proximal big arteries → CABG; otherwise stent
• MONA BASH C + who gets nitrates/clopidogrel + right-sided MI nitrate caveat