Arrhythmias

Arrhythmias Prof.Lammers Cardiovascular module/ weeks

Definition and causes Arrhythmia is abnormal rhythm of the heart. The possible causes of arrhythmias are: 1. 2. 3. 4. 5.

Abnormal rhythmicity of the pacemaker Shift of the pacemaker to another place in the heart Block of different parts of the conducting system Abnormal pathway of impulses transmission Spontaneous generation of spurious impulses in all parts of the heart.

Types of arrhythmias 1. Abnormal sinus rhythm 2. Impulse conduction Block 3. Premature beats 4. Paroxysmal tachycardia 5. Fibrillation

1.Abnormal sinus rhythm Abnormal sinus rhythm is an example of abnormal rhythmicity of the pace maker. It could result from alteration in the strength of the sympathetic and parasympathetic system. Abnormal sinus rhythm are: Tachycardia: HR>100. the possible causes are (Increase body temprature, Increase sympathetic activity) Bradycardia: HR<50. this is normal is athletes to allow the heart to fill enough blood before pumping it. It could result also from excess vagus stimulation

2.Impulse conduction block Sinoatrial Block: the impulses are blocked in the SA node before reaching the atrial muscles. This will eliminate the P wave. Atrioventricular Block: is caused when there is ischemia, compression or inflammation of the AV node or AV bundle. Interventricular Block( RBBB or LBBB): in which impulses fail to reach part of the heart during heart cycle.

SA block ( absent P wave)

Right bundle Branch block (RBBB): S wave is lead I, V6 & a prominent R wave in V1 R wave

S wave

S wave

Left Bundle branch block: S wave in V1 and prominent R wave in lead I and V6

S wave

Types of AV blocks 1st degree Block:characterized by a delay in the conduction from the atrium to the ventricles this is presented with Prolonged P-R interval.

P QRS T

Prolonged P-R interval

P QRS T P QRS T

Types of AV blocks 2nd Degree Block: characterized by slow impulses conduction. Sometime the impulses are strong enough and sometimes they are not. This is known as “ Dropped beats” ( no QRS). This type has 2 subclasses: Mobitz I: Progressive elongation of PR interval is associated with drop beat.drop beat occur after progressive elongation of PR interval Mobitz II: elongation of PR interval is not associated with drop beat.drop beat can occur anytime.

Mobitz I

Mobitz II

Progressive elongation of P-R

Dropped beat

Dropped beat

Types of AV block 3rd degree heart block: also known as complete heart block. Where there is poor impulse conduction in the AV node. It is presented in the ECG by p wave is disassociated from QRS complex. In this case the artial beats could be 100/min while the ventricular beats are 40/min P

QRS T

P

P

QRS

P

3.Premature beats It is also known as Extra-systole , Ectopic beats. In this condition, the heart beats before the time of normal contraction. The causes of premature beat is Ectopic Foci, that could be due to Ischemia, calcification plaque, toxic irradiation of AV node or purkinji fibers. The clinical manifestation of Premature beat is pulse deficit.As the ventricles will not be able to fill Cardiac output decreasesperipheral pulse is not felt.

Types of Premature beats Premature Atrial Contraction (APC): when the atrium contracts very fast.P waves occur too soon and PR interval is very short. The possible reason is that the beat originates in the atrium some where distance from the SA node.

Types of Premature beats Premature Junctional beat: The beat originate from the AV node junction and it is characterized by absent P wave

No P wave

Premature Junctional beat

Types of premature beats Premature ventricular contraction (PVC): abnormal QRS complex prolonged( wide QRS) high voltage (tall QRS)

T wave opposite the polarity of the QRS = Prolonged/ high voltage QRS Inverted

Premature Ventricular contraction

Inverted T wave

4.Paroxysmal tachycardia Paroxysmal tachycardia is a rapid rhythmical discharge of impulses that spread throughout the heart. It is caused by re-entrant circus movement. Types of paroxysmal tachycardia: Paroxysmal supraventricular tachycardia Paroxysmal ventricular tachycardia

Types of paroxysmal tachycardia Paroxysmal Supraventricular tachycardia: during the rapid heart beat, the P wave is either inverted or within the QRS complex. The QRS complex should be narrow, indicating that the impulses are generated in the atrium.

Supraventricular Tachycardia (HR=170), no P wave and a narrow QRS complex

Types of paroxysmal tachycardia Paroxysmal ventricular tachycardia: the impulses are generated from the ventricles which will lead to abnormal QRS and T waves (QRS is usually wide: indicating that impulses are generated in the ventricles) and absent P wave. This is a serious problem because: it does not occur unless there is a considerable ischemic damage, and it could initiate Ventricular fibrillation Ventricular tachycardia: abnormal QRS and absent T wave

5.Fibrillation Fibrillation result from cardiac impulses that have gone berserk within the musclethis will stimulate a portion of muscles to contract & other are relaxing  the impulse will feed-back on the same portion of muscle to re-excite them over and over As a result there will be abnormal coordination in the contraction of the muscles.

Phenomenon of re-entry circus movement Fibrillation result Phenomenon of re-entry circus movement. In which there will be re-excitation of the cardiac muscles over & over. For re-excitation to occur, impulses should reach the muscle after the end refractory period : 1. 2. 3.

The pathway around the circus is enlarged (ex.dilated heart) Velocity of conduction is decreased (ex.Block of purkinji fibers) Refractory period is shorten ( ex. by using some drugs)

Types of fibrillation Ventricular fibrillation: the most serious arrhythmia which if not stopped in 2-3 minutes by cardioversion >> fatal. The ventricles are not contracting, as a result no blood is pumped out of the ventricles & The patient loses consciousness immediately. The ECG pattern is showing a “saw tooth” shape in which there is erratic, chaotic pattern of QRS complexes Saw tooth pattern

Types of fibrillation Atrial fibrillation: The atrium is not contraction & therefore losses its effect as a primer pump to eject the extra 25% of blood to the ventricles. The ECG is AF is irregularly irregular and there is no P wave

Atrial flutter Is another condition which is caused by circus movement in the atria. But it is different from atrial fibrillation because the electrical impulses travel as a single signal always in ONE direction. In atrial flutter, when impulses reach the AV node they delay there. Therefore, every 2-3 beats of the atrium is for 1 beat of the ventricles. In the ECG we can see the flutter waves. Flutter waves, with a very high atrial rate and low ventricular rate. 2 P waves for 1 QRS

P P

QRS

P

P

QRS

P P

QRS