QRS Complex Changes

Q-wave

Condition	EKG changes
Normal	Small septal Q waves may be seen in I, AVL, V5, V6. Deep Q waves may be seen in III and aVR
Pathological Q waves may be seen in MI, cardiomyopathies, lead placement errors, etc.	Pathological Q-waves: Leads V2 to V3: Any Q wave ≥20 milliseconds or a QS complex. Other Leads (I, II, aVL, aVF, V4 to V6): Q wave ≥30 milliseconds and ≥0.1 mV deep in two contiguous leads or a QS complex.
LBBB	no Q-waves in LBBB

Condition	EKG Changes
Anteroseptal MI LVH/ RVH Cardiomyopathy lead misplacement	Poor R wave Progression
Posterior MI RBBB RVH/ Right heart strain Cardiomyopathy Dextrocardia Lead misplacement	R>S in V1
Tricyclic Antidepressant poisoning; other Na channel blocking drugs	R in aVR > 3 mm
Dextrocardia Ventricular tachycardia LA/ RA lead reversal	Dominant R-wave in aVR

Condition	EKG changes
Normal Supraventricular origin without ventricular conduction defect	QRS < 100 ms
Ventricular origin of QRS including ventricular pacing Hyperkalemia Hypothermia Bundle Branch Block Sodium Channel Blockers WPW	QRS > 100 ms
WPW	Delta Wave
Pericardial effusion Infiltrative cardiomyopathies (amyloidosis, sarcoidosis, etc.) Lung diseases (COPD) Hypothyroidism Obesity	Amplitude < 5mm in all limb leads or Amplitude < 10 mm in all precordial leads (Low voltage)
Pericardial effusion/ tamponade PE CHF Severe tachycardia Ventricular tachycardia COPD Altering conduction pathways (intermittent change in velocity/ blockage)	Changing morphology of QRS complexes (Electrical Alternans)
LVH Biventricular Hypertrophy	high amplitude QRS
Arrhythmogenic right ventricular dysplasia	Epsilon wave