Cardiac Arrhythmia

- Cardiac Arrhythmia
Objectives:
1-List the types of arrhythmias.
2-Identify on ECG: ectopic beats, atrial & ventricular fibrillation, and heart block
The causes of the cardiac arrhythmias are usually one or a combination of the following abnormalities in the rhythmicity-conduction system of the heart:
1- Abnormal rhythmicity of the pacemaker.
2- Shift of the pacemaker from the sinus node to other parts of the heart.
3- Blocks at different points in the transmission of the impulse through the heart.
4- Abnormal pathways of impulse transmission through the heart.
5- Spontaneous generation of abnormal impulses in al¬most any part of the heart.
Types of arrhythmias
1- Abnormal sinus rhythms.
2- Conduction heart block.
3- Premature Contractions.
4- Paroxysmal tachycardia.
In some patients with A-V block, suddenly no impulses are conducted from the atria into ventricles for a period of time. The ventricles usually stop for 5 to 30 seconds. Because brain can not remain active for more than 4 to 5 seconds without blood supply, most patients faint a few seconds after complete block occurs. This period of fainting is known as the Stokes-Adams syndrome.
3-Premature Contractions:
A premature contraction is a contraction of the heart be¬fore the time that normal contraction would have been ex¬pected. This condition is also called extrasystole, premature beat, or ectopic beat. Most premature contractions result from ectopic foci in the heart, The possible causes:
• Local areas of ischemia.
• Small calcified plaques at different points in the heart.
• Toxic irritation of the A-V node, Purkinje system, or myocardium caused by drugs, nicotine, or caffeine. Mechanical initiation during cardiac catheterization.
Premature Atrial Contractions
The P-wave of this beat occurs too soon in the heart cycle, and the P-R interval is shortened, Also, the interval between the premature contraction and the next succeeding contraction is slightly prolonged, which is called a compensa¬tory pause. Premature atrial contractions occur:
• In healthy people.