Understanding EKGs Mona Mansoori RN, BSN, CCRN Sara Edington, RN, BSN, CCRN
Properties of Cardiac Muscle Cells! • Automaticity • Excitability • Contractility • Conductivity • (Rhythmicity)
Contraction Electrical • Regulates heart rate • Stimulates cardiac cells to contract via impulses Mechanical • Actual pumping of heart in response to electrical stimuli
Conduction System Review J point J point: marks end of the QRS complex, the J point also indicates the beginning of the ST segment .
ECG Electrode Placement • (V1) 4th intercostal space, right of sternum • (V2) 4th intercostal space, left of sternum • (V3) midway between V2 and V4 • (V4) 5th intercostal space, midclavicular line • (V5) same level as V4, at anterior axillary line (between V4 and V6) • (V6) in 5th intercostal space, midaxillary line
12 Lead Placement
Analyzing the Strip You should assess/measure: You should assess/measure: Step 1: Heart Rate Step 1: Heart Rate Step 2: Rhythm Step 2: Rhythm Step 3: P-Wave Step 3: P-Wave Step 4: Break it down! Step 4: Break it down! A) PR Interval A) PR Interval B) QRS Complex B) QRS Complex C) QT interval C) QT interval D) ST Segment D) ST Segment
Heart Rate 3 methods for assessing rate: Count number of QRS complex in 6 second strip and multiply by 10 Divide 300 by number of big boxes between R – R interval (only for regular rhythms) Count off the number of large squares between R waves with the following rates: 300, 150, 100, 75, 60, 50 Note: Assess both atrial rate and ventricular rate
What is the rate??
Rhythm Can be either REGULAR or IRREGULAR Assess both atrial and ventricular rhythms • Distance between R to R waves and P to P waves should march out across your strip
Regular or Irregular??
The P-Wave SA node is the inherent pacemaker of the heart During P wave: SA node fires an electrical impulse which stimulates both atria to depolarize (contract)
The P-Wave • Assess : • Are P-waves present? • Are P-Waves occurring regularly? – Are they marching out? • Is there a 1:1 conduction of P to QRS? – Is there a P wave for every QRS complex? – Every time the SA node fired, was it CONDUCTED down into the ventricles?
The PR Interval Represents the time it takes for the AV node to “capture” the electrical impulse from the SA node This brief hold allows the atria to contract and then “top off” the ventricles. This is known as Atrial Kick Atrial Kick contributes 15 to 30% of cardiac output
The PR Interval • Measure your PR Interval – What is a normal PR interval? 0.12-0.2 sec • Is the PR interval consistent across the strip? – You MUST measure several PR intervals
The QRS Complex Depolarization of the ventricles, causing them to contract Measure the complex • Normal: 0.08-0.12 seconds • Wide QRS: may originate from ventricle, ectopic beat, BBB • Do all the QRS complexes look the same across the strip?
ST Segment • Represents end systole to beginning repolarization of ventricles • MUST be part of your strip assessment • Should be isoelectric • Important in the diagnosis of ischemia – Can become either elevated (infarct) or depressed (ischemia)
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- Fall '17
- Cardiac electrophysiology, QRS complex