electrocardiograms Flashcards
what is atrial fibrillation
an irregular often, rapid heartbeat and heart rate causing poor blood flow
what is ventricular fibrillation
a life threatening heart rhythm resulting in rapid, erratic electrical impulses in the ventricles
what is bradycardia
a slower than normal heart rate
what is tachycardia
a faster than normal heart rate
what is an ectopic beat
a premature of extra beat originating from outside the normal pacemaker regions
what is ischemia
a restriction in blood supply to tissues causing a shortage of oxygen and nutrients needed for cellular metabolism
what is ventricular hypertrophy
an enlargement and thickening of the walls of the hearts ventricles
what is an artificial pacemaker
devices implanted in people whose electrical conduction system is not working properly
what problems could occur in the electrical conduction system
the SAN may not fire and the blockage or disruption of impulses between the SAN and the AVN or in the Bundle of His
what do pacemakers do
they monitor the hearts electrical activity and stimulate the atria or ventricles to conduct when necessary. impulses are transmitted down electrodes implanted in the muscular walls
what is an implantable cardiverter defibrillator
it can act as a pacemaker and sends weak or strong electrical impulses when needed
what is an electrocardiogram
a record of the electrical activity of the heart
what is the process of an ECG
several electrodes are attached to specific plates on a persons chest or limbs. these detect changes in polarisation of the heart by measuring current at the skin surface. the signal from each of the electrodes is fed into the machine producing an ECG
what does an ECG do
helps diagnose heart problems and indicates if there is part of a heart muscle that is not healthy
how can we indicate an abnormality or a disease from an ECG trace
by looking at variations of the different components of the trace
when can an ECG be taken
while a person is relaxed or may be taken before, during and after exercise.
what is a stress test
involves the patient exercising on a treadmill whilst attached to an ECG machine
what does the P wave indicate
the wave of depolarisation that spreads from the SAN across the atria causing atrial systole
what moves across the membrane during depolarisation
sodium ions move into the cells
what is the PR interval
the time taken for the wave of depolarisation to be conducted from the SAN to the ventricles via the AVN measured from the start of the P wave to the start of the QRS complex
what is the QRS complex
wave of depolarisation that spreads across the ventricles causing ventricular systole
what is the ST segment
the interval between the end of ventricular depolarisation and the start of ventricular repolarisation. it is measured from the end of the QRS complex to the start of the T wave
what is the T wave
repolarisation of the ventricles during diastole
what moves across the membrane during repolarisation
potassium ions move out of the cells
what is a normal ECG composed of
a P wave, QRS complex, ST segment and a S wave
how to work out the frequency of the heartbeat
the distance between identical points on adjacent sections
what does an elevated ST segment indicate
an impending heart attack or an enlarged left ventricle possibly due to cardiovascular disease
what can a depressed ST segment indicate
a lack of oxygen to the heart (myocardial ischemia) and may cause a heart attack or angina
what can cause a depressed ST segment
the drug digoxin
what are arrhythmias
they occur when the heart beats too fast (tachycardia) or when the heart beats too slow (brachycardia) and may be regular or irregular. some are minor, others are life threatening
give one type of lifethreatening arrhythmia that can kill if defibrillation isnt provided quickly
ventricular fibrillation is the absence of coordinated contraction of the ventricles caused by chaotic electrical activity
bradycardia
when the heart rate slows down to below 60bpm. severe bradycardia may be serious and may require an artifical pacemaker to keep the heart beating steadily
why do fit people have bradycardia
training makes the heart beat more slowly and efficiently
tachycardia
when the heartbeat is very rapid over 100bpm. if it is abnormal it may be caused by problems in the electrical control of the heart and may need to be treated by medication or surgery
when is tachycardia normal
when you exercise, have a fever, are frightened or angry.
ectopic heartbeat
extra heartbeats that are out of the normal rhythm. most people have it at least once a day. they are usually normal but can be linked to serious conditions when they are very frequent
give another example of arrhythmia
atrial fibrillation.
this is when rapid electrical impulses are generated in the atria. they contract very fast up to 400 times a minute but not properly and so only some of the impulses are passed onto the ventricles which contract less often. therefore the heart doesnt pump blood effectively
