Staffs Paramedic PPCS2 Flashcards
(43 cards)
How long does each of the smallest squares on ECG Paper represent?
0.04 seconds
How many small squares are there in each of the larger squares on a strip of ECG Paper?
5 x 5 = 25
How long does each of the larger squares on a strip of ECG paper represent?
0.2 seconds
How many larger squares on a strip of ECG paper represent 1 second of time?
5
What does the P wave on an ECG represent?
The P wave represents the depolarisation of the Atria as the depolarisation impulse generated by the SA node passes through myocardial cells to the AV node.
What is the PR segment
The PR segment is the small bit of iso electric line following the P wave until the start of the Q wave.
What does the PR segment represent?
The PR segment represents the depolarisation impulse being held temporarily by the AV node to allow blood to pass from the Atria to the ventricles through the AV valves.
What is the period between the start of the P wave and the start of the Q wave called?
The PR Interval
How long should the PR interval be on the ECG of a healthy Heart?
No longer than 0.2 seconds (5 small boxes)
Why do we not see a wave that represents the re polarisation of the atrium on the ECG of a healthy heart?
Because it happens during ventricular contraction and is hidden behind the QRS complex.
What is a biphasic P wave and what does it show?
A biphasic P wave is a double P wave that is almost m shaped.
A biphasic P wave shows an interruption in the conduction of the depolarising impulse as it crossed the cardiac septum between the two Atria.
What is the intrinsic SA node rate in a healthy heart.
60-100 BPM
What is the normal pathway of depolarisation impulse in a healthy heart?
Generated by cardiac myocytes at the SA node on the posterior wall of the right atrium.
Passes cell to cell through the myocardium of the right atria, across the cardiac septum and continues across the left atrium. Causing the atria to contract.
Held momentarily at the AV node.
Continues down nerve fibres in the Bundle of His
Continues through the right and left bundle branches and anterior and septal fascicles.
Continues in the Purkinje fibres
Spreads out into the myocardial cells of the ventricles causing them to contract.
Explain how the valsalva manoeuvre and modified valsalva manoeuvre work to slow the heart rate of a Pt in SVT.
The valsalva manoeuvre involves over inflating the lungs which causes the intrathorasic pressure to increase. This stimulates the vagus nerve (CN X). The vagus nerve is part of the parasympathetic autonomic nervous system and serves the SA and AV nodes of the heart. Stimulation of the nerve causes signals to be sent to the heart to slow the rate.
The modified Valsalva Manoeuvre requires the Pt to laid back quickly with their legs raised above the heart. This causes a rush of blood to the head and causes a sudden increase in the blood pressure in the carotid arteries and Aorta. Within the walls of these vessels are “Barro receptors” that monitor blood pressure. The sudden increase of pressure is detected. A signal is sent to the cardiac centre in the brain and sympathetic signals to the heart, which cause rate to increase, are inhibited causing a reduction in HR.
Describe the presentation of a 1st Degree AV Block on an ECG
Normal P waves will be seen before the QRS complex and T wave however the PR interval (from the start of the P wave to the start of the Q wave) will be more than 5 small boxes (>0.2sec).
The P-R interval is prolonged by the SAME length every time.
What are the alternative names for 2nd Degree AV Block Type 1
Mobitz type 1
Wenckebach
When Auscultating the heart what are the landmarks that we should be listening to?
2nd intercostal space right sternal border - (Aortic valve)
2nd intercostal space left sternal border- (Pulmonary valve)
4th intercostal space left sternal boarder - (Tricuspid valve)
5th intercostal space mid clavicular - (Mitral Valve)
What do the presence of Bruits when Auscultating the vessels in the neck indicate?
Atherosclerosis
Bruits are the result of turbulent blood flow in the vessels as it passes plaques of fatty material on the inner walls.
Explain how Clopidogrel prevents clots from forming (or getting worse when given as an anti platelet medication in ACS)
Platelets have P2Y12 receptor sites on their outer surface that ADP binds to. When an ADP binds to these receptors the Platelet activates changing shape from smooth and not sticky to spiked and sticky. Clopidogrel binds to the P2Y12 receptors inhibiting ADP and preventing this change in shape.
What is the maximum width of a healthy QRS complex?
Up to 0.12sec (3 small squares)
How many attempts at the Modified Valsalva manoeuvre should be attempted to rectify SVT
Two.
Make sure the Pt is placed in a semi recumbent position for a minute following the first attempt and monitored to give the procedure time to take effect.
How does Atropine sulphate work to rectify absolute bradycardia in 2nd and 3rd Degree AV Block patients?
Atropine sulphate can increase the conductivity of the AV node enabling impulses the pass through where they were previously impeded.
How does Atropine Sulphate work to reverse Absolute bradycardia in Sinus Bradycardia patients?
Atropine sulphate inhibits the post synaptic neurotransmitter receptor sites in the Vagus nerve which has a parasympathetic action on the SA node. By impeding the Vagus nerve the SA node should be allowed to return to producing an impulse at its usual rate (60-100bpm)
What Sinus rate is SVT?
> 150bpm
