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Common causes of abnormalities in rhythmicity

abnormal pacemaker, shift of pacemaker to different spot, blocks at different points of impulse spread, abnormal pathways of impulse, spontaneous generation of spurious impulses in any part of heart.



Fast heart beat.( more than 100/ min.), Sympathetic stimulation causes it


how many beats does heart rate rise per degree fahrenheit with a fever?

10 beats per degree



slow heart rate ( less than 60 beats/min.) Common in athletes, Vagus nerve slows heart down.


what is carotid sinus syndrome?

pressure receptors in carotid sinus are excessively sensative. Causes bradychardia


sinus arrhythmia

Results from conditions that alter strengths of the sympathetic and parasympathetic nerve signals. ( not a constistant beat, its all over the place)


sinoatrial block

impulse from sinus node is blocked before entering the atrial muscle. ( ECG shows sudden cessation of p waves with standstill of atria)


Atrioventricular block

problem with the transition from the a-V node to the ventricles


name some causes of the atrioventricular block problems

ischemia of AV node or AV budle fibers, compression of AV bundle by scar tissue or calcified spots on heart, inflammation of AV node or AV bundle, extreme stimulation of heart by vagus nerve


first degree AV block

when P-R interval increases to greater than .2 second. Its a delay of conduction from the atria to the ventricles but not actual blockage. ( acute rheumatic heart disease causes this)


second degree

P-R interval increases to .25-.45 second. Action potential sometimes is not strong enough to get passed to ventricles. So you see P waves but no QRS-T complex. This develops a 2:1, 3:2, 3:1 rhythm


Third degree

( complete block)- impulse is not passed to ventricles. Ventricles create its own new pacemaker. P waves are now dissociated with QRS-T complex


Stokes adams syndrome

When AV conduction ceases and ventricles stop beating for 5-30 seconds. Eventually they start ( ventricular escape) but sometimes brain damage occurs.


incomplete intraventricular block

partial intraventricular block every other heart beat


premature contractions

also called extrasystole, premature beat, or ectopic beat


what causes premature contractions?

ischemia, calcified plaques at different points of heart, toxic irritation of AV node/ purkinje fibers by caffeine or other drugs


pulse deficit

heart contracts before ventricles fill up all the way. This results in a low stroke volume


ECG of A-V bundle premature contractions

P wave is missing. It is superimposed onto the QRS-T complex


ECG of premature ventricular contractions

QRS complex is usually considerably prolonged. This is cause the implulse is conducted through slowly conducted muscle rather than purkinje fibers. QRS also has a high voltage because it passes through both ventricles simultaneously. The T wave also has an electrical potential polarity exactly opposite to that of QRS


what causes disorders of cardiac repolarization?

inherited- mutations of sodium or potassium channel gates.
acquired- associated with plasma electrolyte disturbances like hypomagnesemia, hypokalemia, or hypocalcemia


parazymal tachycardia

Heart rate becomes rapid in paraxysms( lasting small period of time). It can be stopped by a vagal reflex( pressing on neck) or by quinidine or lidocaine.


atrial paraxysmal tachycardia



AV nodal paraxysmal tachycardia



Ventricular paraxysmal tachycardia

is serious for 2 reasons. First, it only occurs if there is damage in the ventricles. Second, this condition usually initiates ventricular fibrilation


ventricular fibrilation

very serious. Ventricular chamber neither enlarges nor contracts.


Atrial fibrilation

Atria become useless as primers but blood still flows passively into the ventricles. The ventricle efficiency is decreased by 20-30 % ECG shows no P-wave


Atrial flutter

rapid contractions of atria between 200-350 beats/ minute. Signals reach the AV node at the same time and not all of them are allowed to move on .This results in 2 or 3 beats of the atria for every 1 of the ventricles