Pqrst Flashcards
P
QRS complex
T
Shows atrial depolarization while atrial repolarization is buried in qrs complex..
Qrs complex shows ventricular depolarisation
Ventricular repolarization
PR segment its cause and when it î and when !
Time between atrial depolarisation and ventricular depolarisation. Depends on av conduction.
if î—> î^v by sympathetic ns, if ! —> !v by parasympathetic ns
AV node conduction is very small therefore isoelectric line is shown
QT interval
ST segment
PR interval
Represents entire period of ventricular depolarisation n repolarisation
Period when ventricles are depolarised at this time isoelectric line is shown . This is time of plateau in action potential
PR interval shows atrial dep + AV node conduction
When valves open and when close
Valves(both av and semilunar) close when the pressure in next chamber(i-e ventricle n and arteries) rises
Valves (av n sl) open when pressure in next chamber(ventricles n arteries) falls than the previous
at which point of ecg ventricle pressure stars falling
At the onset of T wave
The contribution of Atrial contraction in ventricular filling in normal and when heart rate increases
15% at normal
Increases whenever heart rate increases and cardiac cycle decreases
Cause of P wave Q wave R wave S wave and T wave
Why Q and S waves are downward
Atrial depolarisation—> p
Septal depolarisation—>Q
Ventricles dep.—> R wave
ventricular Basal dep.—> S ( because +ve electrode gets -ve first and still -ve electrode is positive therefore first half of s wave occur)
Ventricular repolarization—> T wave (because ventricles are still depolarized mean -ve outside then +ve terminal gets repolarized first means +ve outside hence first half of T wave occur)
In ECG graph what duration big and small squares show and how much sqaure P ,PT segment,QRS,and QT interval occupy . And how much duration they take
1big square=0.2 sec
1small square=0.04sec****
P , PR segment and QRS complex occupy 21/2 squares means 0.1 second each
While RT interval occupies 10 squares i-e O.4 second
What is enthovens triangle and law
Equilateral triangle whose sides are made by bipolar limb leads placed in frontal plane
Enthovens law says that voltage of lead 2 will always be equal to sum of v of lead 1+3 if recorded simultaneously
During major ventricular depolarization which parts of body are -ve and which are +ve
During mvd whats the potential at right hand and left hand and left ankle
During MVD
Upper part and right part—> -ve
Lower part and left part—> +ve
-0.2 at right hand
+0.3 at left hand
+1.0 at left ankle
During major ventricular depolarisation whats the potential of lead 1 ,2 and 3
What are the angles of their axis from which they face major vector
How angles are arranged
Lead 1 potential difference—> 0.5
Lead 2 potential difference—> 1.2
Lead 3 potential difference—> 0.7
Lead 1–> 0°
Lead 2–>60°
Lead 3 —>120°
When vector is horizontally leftward angle is zero from this reference point angles are arranged clockwise
What will be the pattern of qrs if the major vector was horizontally leftward
Downward and rightward
It will be a bit positive (0.3)
It will be more postive(0.8) but less than the normal(1.2)
Angles of lead aVR,lead aVL and leqd aVF
Lead aVR—> +210
Lead aVL—> -30°
Lead aVF—> +90°
How to find the potential in any lead according to the potential of major vector of heart
How to find its polarity
Draw a perpendicular line from the tip of major vector to the axis of lead. The size of vector on axis shows the potential of lead
The directions pf vector on axis shows the dir of polarity
How and when a wave of ecg is positive and how it’s negative and why T wave is positive
At the onset of depolarisation the end near -ve terminal become negative and still positive end is positive because depolarisation hasn’t reached—> this causes initial half of positive wave other half is produced when +ve terminal also gets -ve.
That part of ventricle which is depolarized last will repolarize first hence +ve terminal gets +ve charges first and -ve terminal is -ve still. When negative terminal also gets +ve wave completes
Atrial T wave is either above the isoelectric line or below ?
and why
And whats it benefit
Atrial T wave is below the isoelectric line because atria depolarize slow as compared to ventricles because of absence of purkinji system
Therefore Sa node repolarize first
Slow conduction through Av node helps in ventricular filling time
Left ventricular hypertrophy cause and its qrs complex recorded from 3 axis
Lv hypertrophy can be due to hypertension when lv has to work more to push blood against MAP.
Lead 1 will be +ve lead 3 -ve and hence lead 2 bit +ve
Same occurs due to aortic valvular stenosis and aortic valvular regurgitation
When heart angulates leftward and when rightward
What causes left a ventricular hypertrophy
Heart angulates leftward when a person 1)deep expirates 2)lies down3) obese (because abdominal contents press)
Angulates rightward when a person 1)deep inspires 2) stands up 3) tall lanky
When bp î 2) aortic valvular stenosis 3)aortic valvular regurgitation
Axis deviation and ecg pattern of left ventricular bundle branch block
And right ventricular bundle branch block
Axis deviates about -50° upward and leftward
Prolonged qrs occurs(0.09-0.14 sec)
Axis deviation of about 105° downward and rightward
Prolonged qrs due to slow conduction(0.09-0.14sec)
Normal voltage of qrs and Abnormal voltage and its cause
Voltage from the top of q wave to the bottom of s wave is about 0.5-2.0mV
ÎV—> by hypertrophy
!V—> by ! In muscle mass due to 1) old MI 2)impulse conduction through pericardial fluid(they short circuit conduction)
3) pulmonary emphysema(because or more air or insulation by lungs)
Difference between ecg pattern of hypertrophy and bundle branch block
Prolonged qrs occurs along with axis deviation in bundle block branch
