1/17/2018 1 ELECTROCARDIOGRAM Rhythm Strip Analysis Saleema Allana, Assistant Professor, AKUSONAM
Conduction System of Heart • Electrical impulses initiated within the heart are transferred along a network of specialized cells called the conduction system. 2 1/17/2018
1/17/2018 3 ELECTROCARDIOGRAM (ECG)
ECG Waveforms The baseline is also known as the isoelectric line. The heart’s electrical activity produces several waveforms The waveforms are: • P wave • QRS complex • T wave 6 1/17/2018
Characteristics of P waves P Waves • It represents atrial depolarization . • Normal P wave precedes a QRS complex. • To evaluate P waves, look for three characteristics: Location and number (one P wave before a QRS complex), Configuration (Rounded and monophasic), & Deflection (upward) • If all of the P waves do not look alike, then the impulse may be coming from elsewhere in the atria and not from the SA node 7 1/17/2018
QRS Complexes • QRS complex represents ventricular depolarization ( ventricular systole). • Normal duration of QRS complex is 0.04 to 0.12 seconds. • A broad QRS complex indicates delayed conduction of impulses from AV node to bundle of HIS to purkinjee fibres • Normal duration is from beginning of the Q wave to the end of the S wave (where the S wave returns to the isoelectric line or baseline) • Q wave = Negative deflection • R wave = Positive deflection • S wave = Negative deflection, after the R wave 8 1/17/2018
T Waves • T wave represents ventricular repolarization ( ventricular diastole) • The end of the T wave is the point where it returns to the baseline. 10 1/17/2018
P & Q of Electrocardiography 1/17/2018 11 Atrial Depolarization Ventricular Depolarization Ventricular Repolarization
Analysis of an ECG Rhythm Strip • Rate • Rhythm/Regularity • Interval • PR interval • QRS interval • QT interval 12 1/17/2018
Evaluate Heart Rate The 6-Second Method Can be used If rhythm is regular or irregular. • Identify a 6-second strip • Locate 3-second markers or 30 large boxes. • Count number of complete QRS complexes in a 6- second strip and multiply by 10. • This gives you an approximate number of beats per minutes. • Atrial and ventricular HR can be calculated separately by multiplying number of P waves and QRS complexes by 10, respectively. 13 1/17/2018
The Sequence Method • It is used when the rhythm is regular • Locate an R wave on a heavy, black line of a large box (0.20 second) • Label the consecutive heavy, black lines as follows: 300, 150, 100, 75, 60, and 50.
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- Fall '19
- Cardiac electrophysiology