|
|
| Normal Atria |
- Atrial depolarization begins at the SA node and travels
through the right atrium, across the intra-atrial septum to the left
atrium.
- The electrocardiographic representation of atrial
depolarization is the P wave.
- Right atrial depolarization forms the initial portion of the
P wave. The left atrial depolarization forms the terminal portion of the P
wave.
- The normal P wave axis is falls between +45o and +60o.
|
| Atrial
Enlargement |
Left Atrial Enlargement |
Diagnostic
Criteria
- The terminal portion of the P wave in lead V1 must be one
small box wide by one small box deep or larger to qualify as left atrial
enlargement.
- This force can be calculated by multiplying the time in
seconds by the depth in millimeters. If this product is more negative than
-0.04 LAE is present.
- A notched P wave in leads I & II with a duration of 0.12
msecs or more. "P mitrale"
- LAE can shift the P wave axis to +15o or less.
Differential Diagnosis
- Valvular disease
- Mitral stenosis
- Mitral regurgitation
- Decreased Left Ventricular Compliance
- Longstanding hypertension
- Obstructive cardiomyopathy
- Aortic stenosis
- Aortic regurgitation
- Infiltrative heart disease
- All of these conditions increase either pressure or volume
loading on the atria leading to enlargement and/or hypertrophy.
|
|
Right Atrial Enlargement |
Diagnostic Criteria
- The P wave in leads II, II and aVF is peaked with a height
greater than 2.5mm. "P pulmonale"
- The P wave axis is +75o or greater.
- The positive aspect of the P wave in lead V1 or V2 is
>1.5mm in height.
Differential Diagnosis
- Valvular Disease
-
Tricuspid stenosis
-
Tricuspid regurgitation
- Pulmonary Hypertension
-
COPD
-
Pulmonary emboli
-
Interstitial lung disease
-
Sleep apnea
-
Mitral valve disease
-
Left ventricular systolic dysfunction
- Congenital Heart Disease
|
| Biatrial
Enlargement |
Diagnostic Criteria
Because the P wave is composed of distinct right and left
atrial components, the diagnosis of biatrial enlargement is simply made by
looking for the criteria for both right and left atrial enlargement.
- A large biphasic P wave in lead V1 with the initial component greater than
1.5mm in height and
the terminal component at least 1mm in depth and 0.04 sec in duration.
- A P wave amplitude of >2.5mm and duration of >0.12 seconds in the limb
leads. II.
|
|
|
| Normal Ventricles |
- Depolarization of the ventricles is represented by the QRS
waveform on the surface ECG.
- The normal axis of ventricular depolarization is between -30o and
+105o.
|
|
Ventricular Hypertrophy |
Conditions that increase the load, pressure or volume, on
either the left or right ventricle, cause a compensatory increase in the
ventricular muscle mass. This increase in muscle mass is seen on the surface
electrocardiogram as an increase in QRS voltage. |
| |
Left Ventricular Hypertrophy |
Diagnostic
Criteria (>40 years of age)
- Limb Leads (Low sensitivity, high specificity)
- R wave lead I + S wave lead III > 25 mm
- R wave aVL > 11mm
- R wave aVF > 20mm
- S wave in aVR > 14mm
- Precordial Leads (High sensitivity, low specificity)
- R wave V5 or V6 > 26mm
- R wave V5 or V6 + S wave in V1 > 35mm
- Largest R wave + largest S wave in precordial leads > 45mm
Differential
Diagnosis
- Aortic stenosis
- Aortic regurgitation
- Mitral regurgitation
- Systemic hypertension
- Hypertrophic cardiomyopathy
Other criteria
- Sokolow + Lyon (Am Heart J, 1949;37:161)
- Cornell criteria (Circulation, 1987;3: 565-72)
- SV3 + R avl > 28 mm in men
- SV3 + R avl > 20 mm in women
- Framingham criteria (Circulation,1990; 81:815-820)
- R avl > 11mm, R V4-6 > 25mm
- S V1-3 > 25 mm, S V1 or V2 +
- R V5 or V6 > 35 mm, R I + S III > 25 mm
- Romhilt + Estes (Am Heart J, 1986:75:752-58)
|
|
Right Ventricular
Hypertrophy |
Diagnostic
Criteria
- Right axis deviation of +110o or more
- R/S ratio > 1 in lead V1
- R wave lead V1 <7mm
- S wave lead V1 < 2mm
- qR in V1
- rSR' V1 with R' >10mm
Differential
Diagnosis
- Pulmonary stenosis
- Mitral stenosis
- Ventricular septal defect
- Atrial septal defect
- Pulmonary hypertension
- COPD
- Pulmonary emboli
- Sleep apnoea
- Interstitial lung disease
Other causes of a large R wave in lead V1 are posterior
infarct, muscular dystrophy, type A Wolff-Parkinson-White syndrome and right
bundle branch block. |
|
Biventricular Hypertrophy |
Diagnostic
Criteria
- One or more criteria for both left and right ventricular hypertrophy
- LVH in the precordial leads with an axis > +90o
|
| Ventricular Strain Patterns |
ST-T wave changes associated with abnormal repolarisation
secondary to increased ventricular tension have classically referred to as
"strain" pattern. |
|
Left
Ventricular Strain |
Left ventricular hypertrophy is often associated with ST
depression and deep T wave inversion. These changes occur in the left
precordial leads, V5 and V6. In the limb leads the ST-T changes occur opposite
the main QRS forces. Therefore, if the axis is vertical, the ST-T changes are
seen in II, III and aVF. If the axis is horizontal the ST-T changes are seen
in I and aVL. |
| Right Ventricular Strain |
Right ventricular hypertrophy can be associated with ST
depression and T wave inversion in the right precordial leads, V1 - V3. Leads
II, II and aVF may also show similar ST - T wave changes. |
| Low Voltage |
Diagnostic Criteria
- Voltage of entire QRS complex in all limb leads
<5mm.
- Voltage of entire QRS complex in all precordial leads
< 10mm.
- Either criteria may be met to qualify as "low
voltage".
Differential
Diagnosis
An increase in the distance between the heart and the ECG
leads, infiltration of the heart muscle itself and metabolic abnormalities are
all associated with low voltage.
- Increased Distance
-
Pericardial effusion
-
Obesity
-
COPD with hyperinflation
-
Pleural effusion
-
Constrictive pericarditis
- Infiltrative Heart Disease
- Amyloidosis
-
Scleroderma
-
Hemachromatosis
- Metabolic Abnormality
|
