EKG

Timing Intervals and Paper Speed

 - The horizontal axis timing intervals are key in EKG interpretation.
 - Every five big boxes represents one second.
 - Paper speed specifics:
   - Each big box is equivalent to 200 milliseconds (0.2 seconds).
   - Each small box is equivalent to 40 milliseconds (0.04 seconds).
   - Hence, the paper speed is 25 mm/s.

Intervals of Interest

 - Importance of knowing interval limits:
   - QRS Duration: Normal limit is between 120 ms and 200 ms.
   - PR Interval: Normal limit is up to 200 ms (abnormal if above).

Measuring QT Intervals

 - Two methods:
   1. Visual Observation: Check if QT goes more than halfway of RR interval.
   2. Actual Measurement: Count boxes from the start of QT to T wave end.
      - Example: Counted QT Interval = 11 boxes = 11 × 40 ms = 440 ms.
   - It's crucial for clinical confidence in QT prolongation measurement.

Interval Memorization Techniques

 - Key memorization points:
   - One second = 5 big boxes; each big box = 200 ms.
   - OR adhere to 25 mm/s to back-calculate.

ECG Axis Determination

 - Concept of axis in EKG interpretation: evaluate positive and negative leads to ascertain normal or abnormal axis.
 - Use lead II and lead aVL for determining QRS axis.
 - Normal Axis: Predominant QRS axis between +90 to -30 degrees.
 - Interpretation Process Example: If lead I is positive and lead II is negative, it indicates left axis deviation.

Clinical Scenarios and Rhythm Analysis

 - Identification of arrhythmias including:
   - Atrial fibrillation
   - Supraventricular tachycardia (SVT)
   - Atrial flutter
   - Ventricular tachycardia
 - Initial steps in analysis:
   - Determine heart rate:
     - Count boxes method (e.g., box count gives 54 or 55 bpm).
     - 300 method: Based on big boxes between QRS complexes.

Common Findings in EKGs

 - Premature Atrial Contractions (PACs): Observed as early beats with varying morphology and PR intervals.
 - Left Ventricular Hypertrophy (LVH) Criteria: R wave in aVL exceeds 11 mm.
 - R Wave Progression: Should grow taller between V3 and V4. Poor progression indicates potential anterior infarct.

EKG Reading Systems

 - Multi-step approach for effective rhythm analysis:
   1. Rate & Rhythm Analysis: Identify heart rate and classify rhythm (e.g., sinus bradycardia).
   2. QRS Axis Assessment: Using leads I and II, determine axis presence and deviations.
   3. Interval Measurement: Check PR, QRS, and QT intervals.
   4. Chamber Evaluation: Check for dilatation or hypertrophy.
   5. Ischemia Detection: Look for ST changes or abnormal Q waves.
   6. Other Findings: Acknowledge PACs, PVCs, and any additional abnormalities.

Specific Pattern Recognition

 - Regularly irregular rhythms can display identifiable patterns (e.g., grouped beating).
 - Distinguishing between conditions such as sinus arrhythmia versus atrial fibrillation requires careful P wave observation.

Treatments and Clinical Approach

 - Recognize and react to arrhythmias promptly, especially for those with pacemakers.
 - Utilize clinical judgment when interpreting EKG changes, leveraging both past and current EKGs for comparisons.