What is cardiac output?
amount of blood ejected from the ventricles each minute
How is cardiac output calculated?
the product of stroke volume times heart rate
How is cardiac output measured?
electrocardiograph/gram (EKG or ECG)
What is a cardiac cycle?
the beginning of one ventricular contraction (systole) until the beginning of another
What are working cells of the heart?
cardiac muscle/myocardium of the atria and ventricles
What are the specialized cells of the heart?
- sinoatrial (SA) node
- atrioventricular (AV) node
- budle of HIS
- purkinjie fibers
What do the specialized cells of the heart do?
originate and transmit electrical impulses across the myocardium and regulate the rhythm of the cardiac cycle
What doe an SA node do? (sinoatrial)
initiates the electrical sequence of a cardiac cycle
What is an isoelectric line?
the baseline of an ECG which signifies the resting membrane potentials
Describe a P wave
- depolarization of atrial muscle cells
- SA node fires at start of the wave
- atrial contraction begins and the peak of the wave
Describe a QRS complex
represents the depolarization of the ventricular muscle cells
What is the ‘Q’ in a QRS complex?
-the downward deflection
What is the “R” in a QRS complex?
initial upward deflection where contraction commences
What is the “S” in a QRS complex?
the return to the baseline
Describe a T wave
when the ventricular muscles repolarize
Describe a U wave
represents the repolarization of the papillary muscle and purkinjie fibers
What is a PR interval?
-the beginning of the Pwave to the peak of R in a QRS complex
What does a prolonged PR interval show?
an AV block
What is the 1st step in an ECG analysis?
Check if the rhythms are regular or irregular
-regular=distance between QRS complexes
What is the 2nd step in an ECG analysis?
Are the QRS complexes similar? Narrrow?
-QRS should not exceed 3sm squares
What does a widened QRS complex demonstrate?
What doe a narrow QRS complex demonstrate?
rhythm being initiated by a pacemaker at the AV node
What is the 3rd step in an ECG analysis?
are all the Pwaves similar with normal PR intervals?
What is the 4th step in an ECG analysis?
is the rate normal?
-count the boxes between QRS complexes and divide by 300
What does bradycardia look like on a ECG?
wide spaces between QRS complexes rate below 60
What does tachycardia look like on an ECG?
spaces between QRS complexes are narrow and above 100
What does atrial fibrillation look like on an ECG?
irregular spaces between the QRS complexes
What does asystole look like on an ECG?
a near flat line
What is the 5th step in an ECG analysis?
do the waves and sequences proceed in normal sequence?
-each Pwave should be followed by a QRS complex, followed by a Twave
What is the most common cardiac arrhythmia?
What is atrial fibrillation?
quivering contraction of the cardiac muscle fibers