Non-cardiac causes of abnormal ECGs
Because HEART is not alone.
electrolytes • Potassium 1/8
The major contributor of repolarization phase.
90F consulted for bradycardia post colonoscopy.
K= 1.2. Noted with generalized ST depression, prolonged QTc, and presence of U wave.
Severe kypokalemia can induce polymorphic VT and sudden cardiac arrest.
The potassium gradient across the cellular membrane is the most important factor in establishing this membrane potential.

During hyperkalemia, the gradient is reduced resulted in the reduction of phase 0 of action potential and slowing of the impulse conduction.
Narrow-based and symmetical peaked T wave in early phase of hyperkalemia.
Sinus arrest and intraventricular conduction delay.
Sine wave: QRS complex continues to widen and blend with T wave.
ECG changes in hypo & hyper K+.
electrolytes • Calcium
is the ion of the phase 2.
Imbalance of Calcium affects ST segment.
Hypocalcemia: prolonged ST segment.
68F with metastic CA with serum Calcium of 14 mEq/l.
Osborn wave (positive deflection at J point), short QTc, and ST elevation.
metabolic & toxicity
During therapeutic hypothermia.
ECG changes during hypothermia
bradycardia, prominent J waves or Osborn waves , prolonged PR/QRS/QTc, sinus arrest, and VT/VF.
J waves syndromes
Prominent J-wave has been observed in both inherited and acquired conditions propmting their designation as J wave syndromes. The proposed mechanism includes the outward shift of repolarization current during early phase of action potential. (Antzelevich, C. J Electrocardiol 2013.)
Causes of J waves syndromesLeads displaying J-wave
Early repolarization syndrome (ERS) type I Lateral leads (I, V4-V6)
ERS type II Inferior leads (II, III, aVF)
ERS type III or Global ER Global
Brugada Syndrome RV leads (V1-V3)
Hypothermia or hypercalcemia mediated Global
78F was found unresponsive in a car with running engine.
Carbon Monoxide Poisoning
Cardiovascular sequelae of CO poisoning are frequent, with myocardial injury assessed by biomarkers or ECG in up to 1/3 of patients.
24F with seizure
TCA Intoxication
ECG Features of TCA Toxicity
  • Sinus Tachycardia is the most common.
  • QRS duration in limb leads is related to prognosis.
    QRS≥100 is an indication for Sodium Bicarbonate.
  • R/S ratio in aVR is related to development of seizure and dysrhythmias.
  • Other ECG findings: prolonged PR/QRS/QT, right axis deviation, and Brugada pattern.
  • Brugada pattern was found to be associated with higher mortality.
Tsai, et al. Emergency Medicine 2017.
65F with AF & HFpEF with recent diaarrhea. Current medications include amiodarone, atenolol, furosemide, ciprofloxacin, and motilium.
Examples of Drugs that prolong QT and associated with a known risk of Torsades de Pointes.
for a full list, please go to or click here for pdf download.
Drug ClassGeneric Name
Antidepressants & Antipsychotics Citalopram, Escitalopram, Haloperidol
Antibiotics Azithromycin, Clarithromycin, Erythromycin, Ciprofloxacin, Levofloxacin
Antiemetics Domperidone, Ondansetron
Incidence of Torsades de Pointes by individual drug in an individual patient is small.

Patients who developed ventricular arrhythmias are among those with clinical scenarios that further reduced their repolarization reserve and cause excessive QT prolongation.
34F got up from a very long-distance train ride and passed out.
Right axis deviation, RV conduction delay, and RV ischemia.
Pulmonary Embolism
ECG is neither sensitive nor specific enough to diagnose or exclude pulmonary embolism.
Chronic Thromboembolic Pulmonary Hypertension (CTEPH)
RV overload: RA and RV enlargement, RV strain, and RBBB.
75M with change in mental status.
3 most common ECG changes in intracranial hemorrhage are
  • Widening and inverted T waves in precordial leads.
  • Prolonged QTc
  • Bradycardia
Ref: Marriott’s practical electrocardiography. 2014.
Causes of Negative or Flattened T waves apart from Ischemic Heart Disease
  • Normal variants: children, black people, & etc.
  • Pericarditis
  • Cor Pulmonale & Pulmonary Embolism
  • Myocarditis & Cardiomyopathy.
  • Mitral Valve Prolapse
  • Alcoholism
  • Stroke
  • Myxedema: usually flat T wave or only slightly negative
  • Athlete, HCM esp. apical type.
  • Drugs: Amiodarone, Amphetamine, etc.
  • Hypokalemia
  • Post tachycardia
  • Secondary to LVH or LBBB
  • Electrical Memory
Electrolytes Imbalance can disrupt the electrical properties of cardiac myocytes, causing abnormalities in QRS duration, QT interval, and T wave morphology.
Pathology in other organs may cause stress to the heart, resulting in strain pattern or ischemic pattern in the ECG.
Many of ECG abnormalites from non-cardiac causes are non-specific. Clinical correlation remains invaluable in diagnosis and treatment.