ECG Findings

Stress Cardiomyopathy (Takotsubo)

• ST elevation (STE) in precordial leads with T-wave inversions (TWI) in multiple leads

• Often precipitated by severe emotional or physical stress

• Can clinically and electrocardiographically mimic acute anterior myocardial infarction

• Coronary arteries are typically normal on angiography

• Echocardiography reveals apical ballooning or regional wall motion abnormalities not limited to a single coronary territory

Pathological Q Waves (Current or Previous Myocardial Infarction)

• Q waves are considered pathological if ≥1 mm (40 ms) wide or ≥2 mm deep, or if depth >25% of the subsequent R wave

• Normal small septal Q waves in leads V1–3 can be a normal variant

• Presence of new pathological Q waves often indicates established infarction and necrosis

• Q waves in leads II, III, and aVF suggest inferior MI, while Q waves in leads V1–V4 suggest anterior MI

Prolonged QTc Intervals

• Best measured in lead II or V5–V6, though multiple leads should be reviewed if there is a borderline reading

• QTc thresholds

  • Men >440 ms

  • Women >460 ms

• QTc ≥500 ms increases the risk of torsades de pointes

• Useful clinical rule: The QT interval should be less than half the preceding RR interval

• Common causes of prolonged QT include electrolyte imbalances (low potassium, magnesium, calcium), certain medications (antiarrhythmics, some antibiotics, antipsychotics), and congenital long QT syndromes

• Bazett’s formula (QTc = QT / √RR) is commonly used for correction

Notes:

• Always correlate ECG findings with clinical presentation, as Takotsubo syndrome and acute MI may be difficult to distinguish clinically

• When assessing for pathological Q waves, compare with old ECGs to identify whether the changes are new or longstanding

• In suspected prolonged QT, check electrolytes and medication history to rule out reversible causes

• In Takotsubo, ST elevation can be more global, extending beyond a single coronary artery distribution, and can evolve to deep T-wave inversions over days to weeks

• Monitor patients with markedly prolonged QTc for ventricular arrhythmias and consider cardiology referral for preventive therapy (beta blockers) or correction of underlying cause