In an adult scheduled for elective surgery, which uncommon electrocardiogram abnormalities should prompt concern and what pre‑operative evaluation and management steps are recommended?

Uncommon ECG Abnormalities of Concern During Preoperative Evaluation

For adults undergoing elective surgery, specific uncommon ECG abnormalities warrant immediate concern and further evaluation before proceeding: ST-segment elevation or depression, new T-wave inversions, Mobitz type II or higher-degree AV block, new bundle branch block, significant QT prolongation, pathologic Q-waves suggesting prior MI, and new atrial fibrillation. 1

Which ECG Abnormalities Should Prompt Concern

The 2024 ACC/AHA guidelines explicitly identify ECG abnormalities that require further cardiovascular evaluation before noncardiac surgery: 1

• ST-segment elevation or depression – indicates active or recent myocardial ischemia 1
• New T-wave inversions – particularly in lateral leads, suggests ischemia and predicts adverse perioperative outcomes 2
• Mobitz type II or higher-degree AV block – represents significant conduction disease requiring evaluation 1
• New bundle branch block – may indicate underlying coronary artery disease, though should not automatically trigger revascularization in asymptomatic patients 1
• Significant QT prolongation – critical for anesthetic selection, as it informs choice of anesthetics, antiemetics, and antibiotics to avoid torsades de pointes 1
• Pathologic Q-waves – suggest prior myocardial infarction and warrant risk stratification 1
• New atrial fibrillation – requires rate control and anticoagulation consideration 1
• Left ventricular hypertrophy with strain pattern – indicates significant structural heart disease 1

Risk-Stratified Approach to Preoperative ECG Evaluation

When to Obtain a Preoperative ECG

For patients with known cardiovascular disease (coronary heart disease, significant arrhythmia, peripheral arterial disease, cerebrovascular disease, structural heart disease) or active cardiovascular symptoms (chest pain, dyspnea, palpitations, syncope) undergoing elevated-risk surgery, a preoperative 12-lead ECG is reasonable to establish baseline and guide management (Class IIa recommendation). 1

For asymptomatic patients without known CVD undergoing elevated-risk surgery, a preoperative ECG may be considered to establish baseline (Class IIb recommendation). 1

For asymptomatic patients undergoing low-risk procedures, routine preoperative ECG is not recommended and does not improve outcomes (Class III recommendation). 1

Surgical Risk Categories

• High-risk surgery (>5% cardiac event rate): vascular surgery, major emergency procedures 2
• Intermediate-risk surgery (1-5% cardiac event rate): intraperitoneal, intrathoracic, orthopedic, prostate surgery 2
• Low-risk surgery (<1% cardiac event rate): cataract surgery, minor dermatologic procedures, cosmetic procedures 2

Evaluation Steps When Abnormalities Are Found

Step 1: Determine if Active Cardiac Conditions Exist

Active cardiac conditions that mandate postponing elective surgery: 2

• Unstable angina or recent myocardial infarction
• Decompensated heart failure (volume overload, dyspnea at rest)
• Significant arrhythmias (symptomatic ventricular arrhythmias, supraventricular arrhythmias with uncontrolled rate, new high-grade AV block)
• Severe valvular disease (severe aortic stenosis, symptomatic mitral stenosis)

If any active cardiac condition is present, postpone elective surgery and treat the condition first. 2

Step 2: Assess Functional Capacity

Excellent functional capacity (≥10 METs): Can climb ≥2 flights of stairs or walk uphill without symptoms. These patients can proceed to surgery despite ECG abnormalities without further testing. 2

Moderate functional capacity (4-10 METs): Can walk on level ground at 4 mph or perform light housework. Further evaluation depends on number of clinical risk factors. 2

Poor functional capacity (<4 METs): Cannot perform activities of daily living independently. These patients warrant further risk stratification. 2

Step 3: Count Clinical Risk Factors (Revised Cardiac Risk Index)

• High-risk surgery (vascular or major emergency)
• History of ischemic heart disease
• History of congestive heart failure
• History of cerebrovascular disease
• Insulin-dependent diabetes mellitus
• Renal insufficiency (creatinine >2 mg/dL) 2

Algorithm for further testing: 2

• 0 risk factors: Proceed to surgery without further testing
• 1-2 risk factors + poor functional capacity: Consider noninvasive stress testing only if results would change management
• ≥3 risk factors + poor functional capacity + vascular surgery: Noninvasive stress testing reasonable if results would change management

Step 4: Specific Management Based on ECG Finding

For QT prolongation: Document QTc interval, review all medications for QT-prolonging agents, communicate with anesthesia team to avoid QT-prolonging anesthetics (sevoflurane, droperidol), antiemetics (ondansetron), and antibiotics (fluoroquinolones, macrolides). 1

For Q-waves or bundle branch block in asymptomatic patients: These findings may indicate coronary artery disease but should not lead to automatic coronary revascularization before noncardiac surgery. Establish baseline and proceed with enhanced perioperative monitoring. 1

For ST-segment or T-wave changes suggesting ischemia: These patients require cardiology consultation, possible stress testing or coronary angiography depending on clinical context, and optimization of medical therapy before proceeding. 2

For new atrial fibrillation: Assess rate control, consider anticoagulation based on CHA₂DS₂-VASc score, and optimize rate control before surgery. 1

For high-degree AV block (Mobitz II or complete heart block): Cardiology consultation for possible temporary or permanent pacemaker placement before surgery. 1

Perioperative Medical Optimization

When proceeding with surgery despite ECG abnormalities: 2

• Continue beta-blockers in patients already taking them; consider starting in patients with ≥1 clinical risk factor, but avoid high-dose initiation immediately preoperatively
• Start or continue statins ideally 30 days before surgery in all patients with atherosclerotic cardiovascular disease, especially for vascular surgery
• Optimize hypertension control: Stage 3 hypertension (≥180/110 mmHg) requires control before elective surgery; continue all antihypertensive medications perioperatively
• Continue aspirin in patients with coronary stents or recent acute coronary syndrome; hold aspirin for procedures with high bleeding risk only after discussion with surgical team
• Establish postoperative surveillance plan: Check troponin and ECG at 24 and 48 hours after surgery in intermediate- and high-risk patients undergoing high-risk noncardiac surgery 2

Common Pitfalls to Avoid

Do not order routine ECGs for asymptomatic patients undergoing low-risk surgery – this increases costs without improving outcomes and may lead to unnecessary downstream testing. 1

Do not automatically cancel surgery for incidental ECG findings (old Q-waves, bundle branch block) in asymptomatic patients with good functional capacity – these findings warrant documentation and enhanced monitoring but not necessarily surgery postponement. 1

Do not fail to compare with previous ECGs – chronic findings misinterpreted as acute changes lead to unnecessary delays and testing. 2

Do not pursue coronary revascularization solely to "clear" a patient for noncardiac surgery – revascularization before noncardiac surgery does not improve outcomes unless it would be indicated independent of the planned surgery. 1

Do not ignore QT prolongation – failure to recognize and communicate this finding can lead to perioperative torsades de pointes when QT-prolonging medications are administered. 1

Avoid the phrase "cleared for surgery" – instead document that "the patient may proceed with planned surgery with guideline-directed medical therapy and enhanced perioperative cardiac surveillance." 2