Chapter 11: Fundamentals Of Electrocardiography Flashcards
When does the repolarization begins in ventricular muscles?
0.25 to 0.35 seconds after the depolarization
When does the atrial repolarization?
0.15 to 0.20 seconds after the termination of P wave, which is the beginning of the QRS Complex
In ECG how many large or small boxes vertically represent 1 mV ?
10 small boxes or 2 large boxes?
What is the standard speed of ECG ?
25 Mm / second
Each small boxes of ECG = ?
0.04 seconds or 40 Ms.
Each large box in horizontal direction is equal to?
0.20 seconds or 200 Ms.
Normal duration of the PR interval?
0.16 seconds or 160 Ms or 4 small boxes.
QT interval duration?
QT interval represents the contraction of ventricles. It starts from the beginning of Q wave to the end of T wave.
It is 0.35 seconds long or 8.75 small boxes.
What is the normal RR interval?
0.83 seconds or 60/0.83
What is the polarity and trajectory of the current flow in the heart?
The current flow has an elliptical trajectory with the positive pole of the vector directed towards the apex of the heart and negative towards the base.
Einthoven’s Law?
Potential of lead 1+ potential of lead 3= potential of the lead 2
What is the voltage of the QRS Complex and P wave in limb leads ?
1.0 to 1.5 mV from top of the R wave to the bottom of the S wave.
P wave= 0.1 to 0.3 mV
T wave= 0.2 and 0.3 mV
What is the normal duration of the PR interval?
0.16 seconds
Lead 1 perspective?
The negative electrode is on the right arm and positive electrode on the left arm. Therefore, the lead 1 perspective of the heart from the right will be negative and the left will be positive.
Lead perspective of lead 2
The negative terminal is connected to the right arm and positive terminal to the left leg. Therefore the right arm is negative with respect to the left leg.
Lead perspective of the lead 3
Negative left arm and positive left leg. The ECG is positive when the vector axis is normal.
Why doesn’t it matter which bipolar limb lead recording is available when diagnosing cardiac arrhythmias ?
The recordings from the bipolar limb leads are all similar to one another and the diagnosis of cardiac arrhythmias depends on the time relationship between the different waves of the cardiac cycle.
Why does it matter to record all standard limb, augmented and precordial leads when diagnosing structural damage or contraction abnormalities of the heart ?
Because the changes in ECG vary based on the lead perspective. Some leads can be abnormal while others may show reciprocal changes or can be completely normal.
Why are the QRS in lead V1 and V2 predominantly negative?
The lead V1 and V2 are located at the level of the base of the heart. Which is the negative polarity direction of the cardiac depolarization vector.
Lead V4 to V6 are predominantly positive. Why ?
These leads are placed at the level of the apex of the heart which is the net electropositivity direction of the cardiac depolarization vector.
Physics of augmented limb leads?
In this type of ECG recording. Two limbs are connected to the Wilson’s central terminal through electrical resistance and the third limb is connected to the positive terminal.
For every 1 mmHg imbalance of starling equilibrium how much will the Net filtration rate increase for the entire body?
6.67 ML/min
What is the significance of Lymphatic system?
The main function of the lymphatic system is to return fluid and proteins in the interstitial space to the blood circulation. Without the returning of interstitial proteins to blood through the lymphatic system a human will die in 24 hrs.
What is the average total amount of fluid that returns to circulation/ day ?
2 to 3 litters
All fats in food are transported from the GI tract through which organ?
The lymphatic vessels
What is the quantity of Lymph flowing through the thoracic duct of a resting human?
100 mL/ hour
Why there is sealing of the lymphatic flow rate?
The lymphatic flow rate can only increase until the interstitial hydrostatic pressure reaches 1 to 2 mm Hg greater than the atmospheric pressure. Beyond that the lymphatic flow rate does not increase due to the fact that a further increase in intestinal hydrostatic pressure will compress and collapse the large lymphatic vessels entry portals.
a
