Day 2: Chamber Abnormalities and Intraventricular Conduction Defects

Day 2: Chamber Abnormalities and Intraventricular Conduction Defects

1. General statements

   1. Echocardiography and other newer imaging techniques, not the electrocardiogram (ECG), are the gold standards for assessing chamber size and wall thickness.

   2. In general, the sensitivities of the following criteria are moderate (in the range of 50%), and the specificities are very high (> 90%).

2. Right atrial abnormality (Day 2-1)

   1. The P wave is pointed in II, III, or aVF, and the amplitude is >2.5 mm (historically referred to as P pulmonale).

   2. P wave axis is frequently >70°.

3. Left atrial (LA) abnormality

   1. In most forms of acquired LA abnormality, the commonest manifestation is a wide (>40 msec) and deep (>1 mm) terminal portion of the P wave in V1. (Day 2-2)

   2. An appearance typical in mitral valvular disease is a "double-humped" P wave, at least 130 msec in duration, in II, III, or aVF (so-called P mitrale). (Day 2-3)

4. Biatrial abnormality—suggested by a combination of tall P waves in II, III, or aVF, and the terminal negativity in V₁. (Day 2-4)

    

   DAY 2-01

   

    

   DAY 2-02

   

    

   DAY 2-03

   

    

   DAY 2-04

   

    

5. Right ventricular hypertrophy (RVH) (Day 2-5)

   1. RVH is suggested by all the following:

      1. Right axis deviation

      2. A tall R wave in V₁ (≥7 mm)

      3. R wave in V₁ + S wave in V₆ ≥10 mm

      4. R/S ratio in V₁ ≥ 1

      5. Incomplete RBBB pattern

      6. Right atrial abnormality

      7. S > R in V₆

   2. The diagnosis of RVH requires exclusion of the other causes of a tall R wave in V₁ (see Day 9).

   3. RVH in patients with acquired pulmonary disease tends to present in a different form: (Day 2-6)

      1. Deep S waves are present across the precordium.

      2. The R wave transition across the precordium is delayed.

      3. Right axis deviation and right atrial abnormality are frequently present.

      4. Low voltage may be present.

6. Left ventricular hypertrophy (LVH)

   1. Precordial leads (any of the following) (Day 2-7)

      1. S wave in V₁ + R wave in V₅ or V₆ > 35 mm in adults (> 30 years)

      2. R wave in V₅ or V₆ > 26 mm

   2. Limb leads (any of the following) (Day 2-8)

      1. R wave in I > 14 mm

      2. R wave in aVL > 11 mm

   3. LVH is frequently accompanied by ST segment and T wave abnormalities, sometimes referred to as a "strain" pattern, but more appropriately as "repolarization" abnormalities.

7. Low voltage (Day 2-9)

   1. Definition

      1. No QRS complex with an absolute value ≥ 0.1 mv (10 mm)

      2. Or, no limb lead QRS ≥ 0.05 mv (5 mm) (so-called low voltage in the limb leads)

    

   DAY 2-05

   

    

   DAY 2-06

   

    

   DAY 2-07

   

    

   DAY 2-08

   

    

   DAY 2-09

   

    

   2. Causes

      1. Decreased voltage production by the myocardium

         1. Restrictive cardiomyopathies (amyloidosis, sarcoidosis, etc.)

         2. Hypothyroidism

      2. Increased impedance between the voltage producing source (the myocardium) and the ECG leads

         ...