EKC Smith Flashcards
What provides a record of net cardiac electrical activity measured between two points on the body surface?
Electrocardiography
What allows the cel to cell propagation of cardiac AP?
Gap Junctions
What is EKG the primary clinical tool for?
Cardiac arrhythmias
Myocardial injury
Disturbances in the HR
In an EKG where do you hear the first heart sound (Lub)?
The S wave
In an EKG where do you hear the second heart sound (Dub)?
Just after the T section
In an EKG when is ventricular filling?
P-Q interval
When does the heart refill with blood?
Ventricular Diastole
In an EKG when does ventricular systole occur?
Q-T interval
In an EKG when does the quiescent phase occur?
End of T wave to beginning of next P wave
What phase in the EKG is this, isovolumetric relaxation in early ventricular diastole until atrial contraction?
Quiescent phase
What are the two types of heart cells?
Specialized pacemaker cells
Working myocardial cells
What type of heart cells are responsible for the initiation and conduction of electrical signals (AP) through the heart?
Specialized Pacemaker cells
What type of cells are responsible for contraction and relaxation and make up the majority of the mass of the heart muscle?
Working myocardial cells
What is the normal activation sequence in the heart?
SA node Atria AV node Bundle of His Bundle Branches Purkinje fibers Ventricles
What normally controls the heart rate?
The electrical activity of the SA node
What cells are specialized for rapid conduction and ensure that all ventricular cells contract at nearly the same instant?
Purkinje fivers
What cells are slower conduction to create a slight delay between atrial and ventricular contraction?
AV node
What is Phase 0?
Upstroke, Rapid depolarization
What is Phase 1?
Rapid repolarization
What is phase 2?
Depolarized Plateau
What is phase 3?
Rapid repolarization after plateau
What is phase 4?
Period between maxiumum Negativity and upstroke (Phase 0)
What are the slow response cells?
Specialized pacemaker cells
What are the fast response cells?
Most cardiac cells
Which type of cells slowly depolarize during phase 4?
Specialized pacemaker cells
What cells do not depolarize in Phase 4?
Working myocardial cells
What is it called if specialized cardiac cells fire APs spontaneously?
Automaticity
What causes phase 0 in working myocardial cells?
Na going in
What causes phase 0 in specialized pacemaker cells?
Ca going in
What causes phase 3 in both types of cells?
K going out
What causes phase 2?
Sustained reduction in K permeability
Sustained increase in Ca permeability
T/F in pacemakers there is no fast inward Na current but rather a slower Ca inward current?
True
What is the strength of a cardiac muscle contraction directly proportional to?
Intracellular Ca Concentration
What does the AP in the heart open?
L-type slow Ca channels
What is cardiac output?
Volume of blood being pumped by the heart per unit time
What is the formula for cardiac output
CO = Stroke Volume x Heart Rate
What is Stroke volume?
End diastolic volume - End systolic volume
What is Total peripheral resistance?
Sum of the resistance of all peripheral vasculature
What is the formula for Blood pressure?
BP = Cardiac Output x TPR
How can you maintain blood pressure?
Alter the CO or the TPR
What is the baroreceptor reflex?
corrects a change in arterial pressure by increasing/decreasing HR
What is the bainbridge reflex?
Responds to changes in blood volume
What is a normal HR?
60-100 bpm
What is tachycardia?
Greater than 100 bpm
What is bradycardia
Less than 60 bpm
What is the normal sinus rhythm drive by?
SA node
In an EKG which wave is atrial depolarization in response to SA node firing found?
P wave
In an EKG which wave is responsible for the time for electrical wavefront to move from the atria to ventricles?
PR interval
In an EKG what wave is ventricular depolarization and trigger main pumping contractions found?
QRS
In an EKG what is the approximate index of ventricular AP plateau (ventricle contracts)?
ST segment
What is the T wave?
Ventricular repolariztion
What is the only electrical link between the atria and the ventricles?
AV node
What would happen if all ventricular cells depolarized at once?
There would be no QRS wave
What interval reflects the time required for AP conduction from atria to ventricles?
PR interval
What interval reflects the average AP duration in ventricles?
QT interval
The elevation or depression of which segment is an indicator of a myocardial infarction?
ST segment
What segment is the rime for the AP to propagate through ventricles?
QRS wave
Which interval is between ventricular beats?
R-R interval
What does a T wave inversion indicate?
Ischemia
What does ST elevation indicate?
Acute infarction
What does an exaggerated Q wave indicate?
A developing infarction
What does ST depression indicate?
Ischemia
What does an exaggerated PR interval indicate?
Something wrong with the AV node
What does the R wave normally represent?
The simultaneous depolarization of the left and right ventricle
What does a split R wave indicate?
A damaged bundle branch
On ventricle depolarizing before the other
What does the QRS wave normally represent?
the rapid depolarization of the ventricles
What might and exaggerated QRS duration indicate?
Purkinje fibers may be damaged
Heart attack
On an EKG what does the large box represent?
.5 MV
.2 seconds
On and EKG what does the small box represent?
.1 mV
.04 seconds
How do you determine your HR from an EKG?
60 divided by the R-R interval
What is einthovens Law?
Lead I + Lead III = Lead II
From and EKG how do you know if it is a sinus rhythm?
Only one P wave followed by QRS complex
If you have an irregular heart rhythm, No clear P wave absence of an isoelectric baseline, irregular R wave, and the ARS complexes may or may not be prolonged, what do you have?
Atrial fibrillation
If you have a P and R wave both present a regular pattern, but the PR interval is greater than .2 seconds what might you have?
First degree av block
If your HR is irregular, P waves present but not regular, R waves present but not regular, and the QRS complexes drops what might you have?
Second degree AV block (Type I)
If your HR is irregular, P waves are present and regular, R waves present but not regular, and QRS complexes drop what might you have?
Second degree AV block Type II
If your HR is irregular, P waves are present and regular, R waves present but not regular, Dropped ARS PR interval irregular what might you have?
Third degree Complete AV block
