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Depolarization. Repolarization. SA node. R. R. T. P. T. P. Q. S. 1. Atrial depolarization, initiated by the SA node, causes the P wave. Q. S. 4. Ventricular depolarization is complete. R. AV node. R. T. P. T. P. Q. S. Q. 2. - PowerPoint PPT Presentation
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Figure 18.17
Atrial depolarization, initiatedby the SA node, causes theP wave.
P
R
T
QS
SA node
AV node
With atrial depolarizationcomplete, the impulse isdelayed at the AV node.
Ventricular depolarizationbegins at apex, causing theQRS complex. Atrialrepolarization occurs.
P
R
T
QS
P
R
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QS
Ventricular depolarizationis complete.
Ventricular repolarizationbegins at apex, causing theT wave.
Ventricular repolarizationis complete.
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QS
P
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P
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QS
Depolarization Repolarization
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Figure 18.18
(a) Normal sinus rhythm.
(c) Second-degree heart block. Some P waves are not conducted through the AV node; hence more P than QRS waves are seen. In this tracing, the ratio of P waves to QRS waves is mostly 2:1.
(d) Ventricular fibrillation. These chaotic, grossly irregular ECG deflections are seen in acute heart attack and electrical shock.
(b) Junctional rhythm. The SA node is nonfunctional, P waves are absent, and heart is paced by the AV node at 40 - 60 beats/min.
In catheter ablation, catheters are threaded through the blood vessels to the inner heart, and electrodes at the catheter tips
transmit energy to destroy a small spot of heart tissue.
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1. A flutter2. PVC3. 1st degree block4. Inverted T wave5. A fib6. A fib with PVC7. Tachycardia8. normal
9. A flutter10. 1st degree block11. A fib12. 1st degree block13. A fib14. PVC15. A flutter with inverted16.2nd degree