Atrial Enlargement and Ventricular Hypertrophy 18 Atrial Enlargement and Ventricular Hypertrophy Fast & Easy ECGs, 2nd E – A Self-Paced Learning Program

Hypertrophy Condition in which muscular wall of the ventricle(s) becomes thicker than normal

Dilation or Enlargement Occurs as result of volume overload where chamber dilates to accommodate increased blood volume

Enlargement or Hypertrophy Enlargement associated with atria P wave changes used to identify atrial enlargement Hypertrophy associated with ventricles QRS complex changes used to identify ventricular hypertrophy Instructional point: The atria dilate more than they hypertrophy. Indicators of enlargement or hypertrophy include an increase in the duration of the waveform, an increase in the amplitude of the waveform and axis deviation. I

Normal P Wave Duration 0.06 – 0.10 seconds Amplitude 0.5 – 2.5 mm First portion represents right atrial depolarization Terminal portion represents left atrial depolarization

Atrial Enlargement Caused by various conditions Chronic pulmonary disease may cause right atria enlargement in response to the need for greater filling pressures in the right ventricle Mitral valve prolapse may result in blood being forced backwards into the left atria causing it to enlarge

Atrial Enlargement Leads II and V1 used to assess atrial enlargement Instructional point: While P wave changes are given specific names such as P Pulmonale for right atrial enlargement and P Mitrale for left atrial enlargement their presence or absence on the ECG is not diagnostic of any underlying medical condition and should be confirmed by more specific testing such as echocardiography. I

Right Atrial Enlargement Increase in amplitude of the first part of the P wave

Left Atrial Enlargement Increased amplitude in the terminal portion of the P wave in V1 Increased duration or width of the P wave Instructional point: Because the duration of time to depolarize the left atria is longer than normal the P wave duration will exceed 0.04 seconds. The P wave may be notched if so the terminal or second portion of the P wave will have a higher amplitude than the initial portion. The P wave may also be biphasic with the terminal portion dipping below the isolectric line. I

Ventricular Hypertrophy Commonly caused by chronic, poorly treated hypertension Because there is more muscle to depolarize there is more electrical activity occurring in the hypertrophied muscle Reflected by changes in the amplitude of portions of the QRS complex Instructional point: In patients with thin chests and in particular the young healthy patient the precordial complexes may meet the criteria for hypertrophy with hypertrophy does not exist. This is occurs because of the lower resistance of the thin chest between the heart and the electrode. In this case you may also use the limb leads to further confirm you suspicion. I

Normal QRS Complex V1 electrode is positive Wave of depolarization traveling through the septum moves toward electrode producing a small R wave Then as the wave of depolarization moves through the left ventricle it moves away from electrode producing a deep S wave

Right Ventricular Hypertrophy In precordial leads R waves are more positive in leads which lie closer to lead V1 and the S waves are deeper in leads that lie closer to V6

Right Ventricular Hypertrophy Most common characteristic in limb leads is right axis deviation Instructional point: Rare conditions such as pulmonary hypertension and pulmonary valve stenosis can result in right ventricle hypertophy. When this occurs the primary ECG evidence is right axis deviation as the enlarged right ventricle overshadows the electrical activity of the left ventricle. I

Characteristics of Right Ventricular Hypertrophy

Left Ventricular Hypertrophy Increased R wave amplitude in precordial leads over the left ventricle S waves that are taller in leads over the right ventricle Instructional points: Because of the greater mass of the hypertrophied left ventricle the amplitude of the QRS complexes across the precordial leads is most affected because they predominantly overlie the left ventricle. The electrical axis remains normal since the energy of the QRS complex remains downward and to the left. The duration of the QRS may be slightly prolonged in both right and left ventricular hypertrophy. However, it is rarely greater than 0.1 seconds more than normal. I

Left Ventricular Hypertrophy The most useful criteria for identifying left ventricular hypertrophy in the precordial leads are the following: Amplitude of S waves in V1, V2 + the amplitude of R waves in leads V5, V6 exceed 35 mm R wave amplitude in lead V5 or V6 exceeds 27 mm R wave amplitude in lead V6 exceeds the R wave amplitude in lead V5

Left Ventricular Hypertrophy The limb-lead criteria for left ventricular hypertrophy include the R wave amplitude in Lead aVL exceeds 11 mm Lead aVF exceeds 21 mm Lead I exceeds 14 mm Lead I plus the S wave amplitude in lead III exceeds 25 mm

Age Considerations The criteria listed are of little value in persons younger than 35 years of age because they frequently have increased voltage due to a relatively thin chest wall

Right and Left Ventricular Hypertrophy It is possible for both the right and left ventricles to be hypertrophied Produces a combination of features such as left ventricular hypertrophy in the precordial leads and right axis deviation in the limb leads However, most often the indicators of left ventricular hypertrophy hide those of right ventricular hypertrophy

ST Segment and T Wave Changes In severe hypertrophy, changes in the ST segment and T waves may also be seen. This is called secondary repolarization abnormalities and includes the following: Down-sloping ST segment depression T wave inversion (which takes an opposite direction to the R wave) Depressed ST segment and the inverted T wave appear to blend together, forming a single asymmetric wave. The downward slope is gradual whereas the upslope is abrupt.

ST Segment and T Wave Changes Repolarization abnormalities are easier to see in those leads with tall R waves because the electrical forces of the hypertrophied ventricle are greater Right ventricular repolarization abnormalities are seen in leads V1 and V2 Left ventricular repolarization abnormalities are seen in leads I, aVL, V5, and V6

Practice Makes Perfect Interpret this ECG tracing Atrial fibrillation with rapid ventricular response, left ventricular hypertrophy with repolarization abnormality

Practice Makes Perfect Interpret this ECG tracing Sinus bradycardia, left ventricular hypertrophy, ST & T wave abnormality, consider inferior ischemia and anterolateral ischemia

Practice Makes Perfect Interpret this ECG tracing Normal sinus rhythm, biatrial enlargement, left ventricular hypertrophy, cannot rule out Septal infarct – age underdetermined

Practice Makes Perfect Interpret this ECG tracing Sinus bradycardia with 1st degree AV block, left atrial enlargement, Septal infarct – age undetermined

Summary In hypertrophy the muscular wall of the ventricle(s) becomes thicker than normal Dilation or enlargement of a chamber occurs because of volume overload where the chamber dilates to accommodate the increased blood volume Enlargement is associated with the atria while hypertrophy is associated with the ventricles

Summary The P wave is used to assess for atrial enlargement The QRS complex is examined to identify ventricular hypertrophy Indicators of enlargement or hypertrophy include an increase in the duration of the waveform, an increase in the amplitude of the waveform and axis deviation Leads II and V1 provide the necessary information to assess atrial enlargement

Summary Diagnosis of right atrial enlargement is made when there is an increase in the amplitude of the first part of the P wave Two indicators of left atrial enlargement are (1) increased amplitude in the terminal portion of the P in V1 (2) increased duration or width of the P wave In limb leads, right axis deviation is most common characteristic seen with right ventricular hypertrophy

Summary In precordial leads, right ventricular hypertrophy causes the R waves to be more positive in leads which lie closer to lead V1 Left ventricular hypertrophy is identified by increased R wave amplitude in precordial leads overlying the left ventricle (lead V5,6) and S waves that are deeper in the leads (lead V1,2) overlying the right ventricle