Anesthesiology APPLIED Exam › Cardiovascular and cardiac anesthesia

Perioperative myocardial ischemia and infarction

Cardiovascular and cardiac anesthesia·~5 min read· Physician-reviewed✓ Sourced · 6

Stem

A 68-year-old man, 84 kg, with hypertension and a drug-eluting stent placed four years ago, is having an open sigmoid colectomy under general anesthesia. He has an arterial line. During mobilization of the colon, with an estimated blood loss of 900 mL, his pressure falls to 84/50 and his heart rate rises to 112. Lead V5 shows new 2 mm horizontal ST depression.

Question

What is happening, and how will you manage it?

Ideal answer

HeadlineNew 2 mm ST depression in V5: ischemia from supply-demand mismatch, with hypotension, tachycardia and blood loss. I restore the oxygen balance by correcting the cause, pressure first.

Phenylephrine and volume for the pressure, because coronary perfusion depends on diastolic pressure.
Then the rate: deeper anesthesia, analgesia, then esmolol, once the pressure is back, because tachycardia raises demand and shortens diastolic filling.
100% oxygen, a hemoglobin, blood below 8 g/dL, because oxygen delivery is the problem.
Tell the surgeon, ask about bleeding, 12-lead ECG; nitroglycerin only once the pressure is adequate.
If changes persist, essentials only, cardiology, troponin: I ask the surgeon to finish the essential part.

Watch for: new ST elevation or hemodynamic collapse, which means occlusion rather than demand mismatch and changes the whole plan.

Breaking down the answer

Which leads I monitor — V5 catches about 75% of ischemic events and II adds the inferior wall and the rhythm; together roughly 80–90%. ST analysis goes in diagnostic filter mode, because monitor mode filters out the ST segment I need.
Type 2, not type 1 — most intraoperative ischemia is demand-driven (tachycardia, hypotension, anemia, hypoxemia), not plaque rupture;¹ fixing the number without the cause invites the next episode. Changes if: ST elevation at stable rate and pressure, meaning plaque rupture or spasm, so cardiology.
Esmolol — heart rate dominates oxygen demand and is the only variable that also shortens diastolic filling time. I titrate 10–20 mg boluses to a rate in the 60s and stop if the pressure falls below baseline minus 20%.
Nitroglycerin's cost — it reduces preload and wall tension and dilates epicardial vessels, but drops the diastolic pressure that perfuses the subendocardium. I start at 0.5 mcg/kg/min only with a systolic above 100 mmHg.
8 while bleeding, about 10 in a true MI — earlier than the 7 g/dL I use for everyone else; liberal transfusion adds volume and transfusion morbidity, so about 10 waits for secure hemostasis, which 2025 ACC/AHA calls reasonable in ACS with anemia.²
Whether to continue — surgical stage against ischemic burden: a colectomy can be closed; an open aneurysm cannot be abandoned. I state the plan to the surgeon rather than ask permission, the judgment the examiner scores.
TEE if I have it — a new regional wall-motion abnormality appears before the ECG changes, and it separates hypovolemia from pump failure.

Follow-up question

In the PACU he reports chest pressure, his pressure is 85/50, and the ECG shows 3 mm ST elevation in II, III and aVF. His neck veins are distended and his lungs are clear.

What do you do?

Follow-up answer

HeadlineInferior ST-elevation infarction, an occlusion, with right ventricular involvement. I call cardiology and tell the surgeon.

Hypotension, distended neck veins and clear lungs point to right ventricular infarction,¹ so beta-blockers and nitroglycerin are the wrong drugs. Oxygen, aspirin 162–325 mg chewed,¹ a careful fluid bolus for the right ventricle, norepinephrine for the pressure. Primary percutaneous intervention, preferred for STEMI when timely,¹ because major surgery within 3 weeks contraindicates fibrinolysis, effectively absolute here.³ Heparin and a P2Y12 inhibitor are decided with surgeon and cardiologist together. Troponin, arterial line kept, a monitored bed with pads on, because inferior infarcts cause bradycardia and block.

Pitfalls that cost points

Treating a 1 mm ST change as noise because the surgeon is busy; ≥1 mm in a monitored lead is ischemia until proven otherwise.
Saying "I would give a beta-blocker" without a drug, a dose and an endpoint.

Rapid-fire

Q: Why is the subendocardium the first to become ischemic? A: It is perfused only in diastole and sits under the highest wall tension, so tachycardia and high end-diastolic pressure hit it first.

Q: Why does ST depression suggest demand ischemia and ST elevation suggest occlusion? A: Depression reflects subendocardial ischemia from supply-demand mismatch; elevation reflects transmural ischemia from an occluded vessel.

Q: Why not just transfuse to a hemoglobin of 10 g/dL? A: MINT, liberal (<10) vs restrictive (7–8): 30-day death or MI 14.5% vs 16.9%, not significant, favoring liberal.⁴ Bleeding: above 8; after hemostasis in a true MI, about 10.²

Q: What is myocardial injury after non-cardiac surgery, and why does it matter? A: An ischemic troponin rise above the 99th percentile, usually silent, with higher 30-day mortality;⁵ troponins reasonable in high-risk patients,⁶ then outpatient cardiology follow-up.⁵ VISION: roughly one in ten died within 30 days.

Numbers to know

Item	Value
Diagnostic ST change	≥1 mm depression or elevation, 60–80 ms after the J point
Lead V5 alone / V5 plus II	~75% / ~80–90% sensitivity
Esmolol	10–20 mg IV boluses, 50–200 mcg/kg/min infusion
Nitroglycerin infusion	Start 0.5 mcg/kg/min; needs systolic >100 mmHg
Transfusion threshold with ischemia	Hemoglobin 8 g/dL while bleeding; about 10 g/dL after hemostasis in MI²
Aspirin for suspected infarction	162–325 mg chewed¹
Fibrinolysis after surgery	Relative contraindication within 3 weeks of major surgery³

Sources

1.Acute Myocardial Infarction (MI) · Merck Manual Professional Edition · merckmanuals.com
2.New ACC/AHA Guidelines Include Transfusion Strategies for ACS Management · AABB, 2025 · aabb.orgSummarizes the 2025 ACC/AHA ACS guideline class 2b recommendation that it may be reasonable to transfuse to a hemoglobin of at least 10 g/dL in ACS with anemia when not actively bleeding; the guideline itself was not fetched.
3.Overview of Revascularization for Acute Coronary Syndromes · Merck Manual Professional Edition · merckmanuals.comTable of contraindications to fibrinolytic therapy for STEMI.
4.Restrictive or Liberal Transfusion Strategy in Myocardial Infarction and Anemia (MINT) · N Engl J Med (Carson et al.), 2023 · europepmc.orgAbstract read via Europe PMC: 3504 patients; 30-day death or MI 16.9% restrictive (7-8 g/dL) vs 14.5% liberal (<10 g/dL), RR 1.15, 95% CI 0.99-1.34, P = 0.07.
5.2024 AHA/ACC Perioperative CV Management Guideline: Key Points · American College of Cardiology, 2024 · acc.org
6.2024 ACC/AHA guideline on perioperative cardiovascular management before noncardiac surgery: What's new? · Cleveland Clinic Journal of Medicine, 2025 · ccjm.orgCohn SL, CCJM 92(4), April 2025; primary guideline text was not reachable from the fetcher.

Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.