Aortic stenosis

Arrhythmias

ECG changes are related to left ventricular hypertrophy

Subaortic stenosis

ECG may be normal

In severe cases “R” wave amplitude is increased (more than normal limits)

There is left axis deviation (MEA < 40°)

S-T segment may be depressed

“T” wave changes are also conspicuous

Pulmonic stenosis

Axis is deviated toward right (MEA > 104° on frontal plane)

ECG changes are related to right ventricular hypertrophy

(There is large S wave in leads I, II, III)

“S” wave is deep (in left precordial chest leads)

Mitral valve stenosis

“P” wave may be tall (>0.4 mV) and broad (>0.04 s)

Supraventricular premature complexes may be seen

Tachycardia may be conspicuous

Atrial fibrillation/flutter may occur

ECG changes related to right ventricular enlargement may be seen

Atrial septal defect

ECG may show right heart enlargement pattern

Ventricular septal defect

Biventricular enlargement pattern may be seen in ECG

Patent ductus arteriosus (left to right shunting)

ECG may show left ventricular enlargement pattern with a normal QRS axis on frontal plane

“R” wave voltage is increased in leads II, III, aVF, V2, and V4

Presence of broad “P” wave (>0.4 s) is suggestive of left atrial enlargement

Patent ductus arteriosus (with pulmonary hypertension)

ECG may show right ventricular enlargement pattern

There may be right axis deviation (MEA > 104°)

Deep “S” wave may be seen in leads I, II, and III

Chronic mitral insufficiency (CMI)

ECG may be normal or abnormal

“P” wave may be broad (>0.04 s), tall (>0.4 mV), and notched (lead II)

“R” wave amplitude is increased in lead II (more than 2.5 mV)

CV6LU (more than 3.0 mV), and CV5RL (more than 0.5 mV)

“Q” and “S” wave amplitudes are increased (more than 0.5 mV) in leads I, II, and III

“QRS” is broad

“T” wave depression may be evident

S-T segment abnormalities are common

Supraventricular premature beats may occur

Ventricular premature complexes may be seen

Atrial fibrillation may be evident

Paroxysmal supraventricular tachycardia may occur

Tricuspid insufficiency (TI)

Lead II may show broad “P” with/without increase in amplitude

P-R interval is increased (more than 0.14 s)

“Q” and “S” waves show increased depth in leads II, III, aVF, and CV6LU

“QRS” is broad (more than 0.06 s)

“R” wave amplitude is decreased in leads II, III, aVF, and CV6LU

“R” wave amplitude is increased in leads aVR and CV5RL

Arrhythmias are not very common

Aortic insufficiency (AI)

Changes similar to chronic mitral insufficiency (CMI)

Pulmonary valve insufficiency (PI)

Lead II may show broad “P” with/without change in amplitude

P-R interval is increased (more than 0.14 s)

“R” wave amplitude is decreased in leads II,III, aVF, and CV6LU

“S” wave is deep in leads II, III, aVF, and CV6LU

“QRS” is broad

Some dogs with congenital PI may show normal ECG

Arrhythmias are not very common

Bacterial endocarditis

ECG may be normal or abnormal

There may be sinus tachycardia

S-T segment abnormalities (elevation or depression) are common

“Q” wave in lead II is deep

ECG may show premature ventricular complexes/ventricular

Tachycardia or AV blocks

“R” wave amplitude is increased in leads II, avF, CV6LL, and CV6LU

“QRS” is broad

“P” wave duration is increased

Dilated cardiomyopathy (DCM)

Rhythm is sinus

“P” may be broad and tall

Arrhythmias (atrial fibrillation, ventricular premature complexes, ventricular tachycardia, “R”-alternans) may be present

“QRS” is broad

S-T segment may show slurring

Hypertrophic cardiomyopathy (HCM)

Atrioventricular blocks are seen

Bundle branch blocks may be present

Left atrium is enlarged (P > 0.04 s)

Left ventricle is hypertrophied

Secondary myocarditis

S-T may show slurring, depression, or elevation in leads II, III, aVF, V2 and V4

Atrioventricular (AV) block may be present

Bundle branch block may be present

Ventricular arrhythmias such as ventricular premature complexes or ventricular tachycardia may be present

Infective myocarditis

S-T segment abnormalities are common

Conduction disturbances are common

Pericardial effusions

“R” wave amplitude is decreased in all leads including chest leads (<1.0 mV)

Electrical alternans (varying amplitude of “R” wave) is commonly seen

Rhythm may be sinus or arrhythmic (tachycardia)

Constrictive pericarditis

Low-voltage complexes are common

“P” wave may be broad (more than 0.04 s)

Rhythm may be sinus or arrhythmic

Supraventricular arrhythmias may be seen

Restrictive cardio-myopathy

Atrial fibrillation may be seen

Ventricular arrhythmias may be seen