cardio quick fire Flashcards
What do A waves represent?
A waves represent atrial contraction
A waves are part of the pressure changes observed in the atrial pressure waveform.
What do C waves correspond to?
C waves correspond to the tricuspid valve bulging into the atrium during right ventricle contraction
C waves occur due to the transient increase in atrial pressure.
What do V waves represent?
blood returning from the systemic veins filling the right atrium.
Normally, this ‘v’ wave is small because the tricuspid valve prevents excessive backflow into the atrium.
When the tricuspid valve is incompetent (tricuspid regurgitation) or there is excessive right atrial volume, the ‘v’ wave becomes prominent or giant due to the increased pressure.
V waves occur during the atrial filling phase.
When does X descent occur?
X descent occurs following the C wave and before the V wave
X descent reflects atrial relaxation and is part of the pressure curve.
What condition is indicated by large A waves?
Large A waves occur with tricuspid stenosis, right ventricular hypertrophy and complete heart block
Large A waves indicate increased atrial pressure during contraction.
What causes giant V waves?
Tricuspid regurgitation
The ‘v’ wave in the jugular venous pulse (JVP) represents right atrial filling during ventricular systole when the tricuspid valve is closed. Large or prominent ‘v’ waves occur when there is increased right atrial pressure due to tricuspid regurgitation or increased right atrial volume.
Giant V waves indicate significant backflow of blood into the atrium.
what does dp/dt represent?
contractility
LVEDP
1.what does LVEDV represent?
2. effect of aortic regurg on LVEDP
3. relationship between LVEDP and myocaridal o2 consumption
1.LVEDP gives an index of preload
LVEDV represents preload. The best measure of preload in LVEDV, however this will correlate with LVEDP - the exact numerical relationship being dependent on left ventricular compliance.
- LVEDP is increased in aortic regurg because regurgitant blood re-enters the ventricle increasing volume and pressure
3.raised LVEDP increase myocardial work and therefore oxygen requirement.
what is the effect of increased SVR on CO
increased SVR increases afterload, resulting in decreased CO
what is the effect of hyperkalaemia on inotropy
hyperkalaemia has a negative inotropic effect
when is aortic blood flow lowest?
early diastole
when is aortic pressure highest?
mid systole
what percentage of ventricular filling is atrial contraction responsible for
a.) at rest
b.) with tachycardia
a.) 20% at rest
b.) 40% with tachycardia
relative to the cardiac cycle, when does QRS complex occur
QRS complex occurs immediately before isovolumetric contraction
when does the aortic valve open during the cardiac cycle
the first part of ventricular contraction is isovolumetric with the aortic valve closed.
The aortic valve opens once LV pressure exceeds aortic pressure.
what physiological changes occur during acute haemorrhage:
-increased ADH
-initially sympathetic nerve activity increases, when blood volume is critically depleted, peripheral sympathetic drive falls steeply. (terminal bradycardia- peri-arrest-> urgent massive transfusion required)
-baroreceptors increase efferent output
-increased glucagon release- increases glucose (gluconeogenesis, glycogenolysis), +ve inotrope
-fluid enters capillaries from interstitium as a result f reduced hydrostatic capillary pressure
- Early Response: Baroreceptor Activation (Compensation Phase)
🔹 Initial Effect of Haemorrhage
↓ Blood volume → ↓ Venous return → ↓ Stroke volume → ↓ Cardiac output (CO) → ↓ Blood pressure (BP)
The decreased arterial pressure reduces stretch on the baroreceptors, leading to decreased baroreceptor firing to the medullary cardiovascular center.
🔹 Compensatory Sympathetic Activation
⬇ Decreased baroreceptor firing → Sympathetic activation & Parasympathetic inhibition
fetal circ at bith:
1.what happens to fetal Pulmonary vascular resistance with the first breath
2. SVR
3. LA pressure
4. ductus arteriosus
5. foramen ovale
6. blood flow in IVC
7. effect of hypoxia
8. what pressure is generate with first breath
1.with the first gasp, PVR falls by >80%
2. SVR rises largely due to intense vasoconstriction of umbilical vessels
3. LA pressure rises due to increase pulmonary blood flow.
4. ductus arteriosus should close within 48hours largely due to high PaO2 and reduced prostaglandins (high prostaglandins can keep it open/patent!)
5. foramen ovale closes as left atrial pressure rises preventing the right to left shunt that occurs prior to birth (bypassing lungs). It does not being to fuse until 48hours
6. IVC blood flow falls
7. hypoxia favours a right to left shunt. any stimulus increasing pulmonary vascular resistance, favours a right to left shunt and hence a persistent fetal circulation. These stimuli include hypoxia, hypercarbia, acidosis and hypothermia.
8. The first breath generates a negative pressure of about 50 cmH2O
regarding the a-wave in the jugular venous phase:
1. what does the a wave represent
2. what increases the a wave
3. what happens to the a wave in AF
4.what does v wave represent
5. what are cannon waves
- a wave represents atrial contraction
- a wave is elevated in tricuspid stenosis (higher atrial pressure needed)
- a wave is absent in AF
- V wave= atrial filling during ventricular systole. this is elevated in tricuspid regurg (tricuspid should be closed but leaks back into atria increasing the filling.
- cannon waves are enlarged a waves corresponding to atrial contraction against a closed tricuspid valve. seen in HBor junctional rhythms.
regarding cardiac ventricular muscle:
regarding cardiac ventricular muscle:
-cells are largely impermeable to negatively charged ions
-depolarisation is followed by a pleateu lasting 200ms
due to calcium influx via slow L-type calcium channels
-rapid depolarisation is due to sodium influx. Depolarisation of slow-response action potentials of pacemaker cells is due to calcium influx throught transient (T-type) calcium channels.
- prolonged refractory period prevents tetany
what percentage of CO is coronary blood flow at rest?
coronary blood flow at rest is 5% of CO (250ml/min)
what is the effect of hypoxia on coronary blood flow
hypoxia increases coronary blood flow 2-3 fold
tell me about coronary circulation A-V oxygen difference
The coronary circulation has the highest A-V oxygen difference of all the major organs
The myocardium extracts 70% of oxygen
what drives coronary blood flow
Coronary blood flow is regulated via the baroreceptor reflexes
Aortic pressure provides the main driving force for coronary blood flow and this pressure is controlled by baroreceptor reflexes. Flow is also affected by many local factors, including systolic compression and local metabolic factors.
how long is transmission through atrium
Transmission through the atrium and the AV node to the ventricular myocardium takes 0.2 s.
what is the route of excitatory transmission from right to left atrium
The preferential route of transmission from right to left atrium is via Bachmann’s bundle. Also known as the anterior interatrial band.
what are gap junctions?
Gap junctions are located at the intercalated disc and allow electrical impulses to propagate freely.
explain the valsalva manouvre
-At the onset of the Valslava manouvre arterial pressure rises due to the the effect of increased intrathoracic pressure on the aorta.
- After the initial rise, BP then falls due to the effect of raised intrathoracic pressure on venous return - this will be more pronounced in the hypovolaemic and can result in cardiovascular collapse.
- Pressure changes are detected by baroreceptors.
-Autonomic neuropathy results in an absence of heart rate changes, but this is seen in only 20-40% of long-standing diabetics
what is the effect of valsalva on murmurs
It increases the murmur of mitral regurgitation, but most other mumurs are decreased.
regarding cardiac cycle, when is aortic blood flow lowest?
early diastole
with jugular venous pulse a wave, is it elevated in tricuspid regurg or stenosis?
jugular venous pulse a wave is elevagted in tricuspid stenosis (larger pressure to overcome)
the v wave is elevated in tricuspid regurg
cannon waves are large wa laves corresponding to atrial contraction against a closed tricuspid valve. Seen in complete HB or junctional arrhythmias.
when does coronary perfusion occur
mainly during diastole
right side is mainly during diastole, but also occurs during diastole.
what can be used to measure left atrial pressure
left atrial pressure (wedge pressure) can be measured using a pulmonary artery flotation catheter
what happens to pressure if compliance of left ventricle incease
LVEDP will reduce is LV compliance increase.
pressure will be lower for a given volume if compliance is increased (Complaince = Vol/Pressure)
what occurs when there is an increase in right atrial presssure?
An increase in right atrial pressure results in:
-increased preload
-increased type A atrial stretch receptors discharge during atrial systole
(type B atrial stretch receptors discharge during atrial diastole)
- increase in urine volume due to stimulation of atrial stretch receptors causing the release of ANP, which has diuretic action
- can decrease the heart rate via the baroreceptor reflex, however increased Ra filling can also increase HR via the bainbridge reflex. Whether the HR increases of decreases after a sudden increase in intravascular volume is thought to be related to the initial heart rate (decreasing if it is high and increasing if it is low).
what is the RMP of
a.) pacemaker cells
b.) myocardial cells
a.) pacemaker cells RMP = -60mV
b.) myocardial cells = -90mV
what causes calcium release withing sarcoplasmic reticulum
calcium in SR is is released in response to rising intracellular calcium levels.
where does blood supply to SA and AV node come from ?
RCA supplies both SA and AV node
what happens to CO during exercise?
what happens to CVP during moderate exercise
intravascular volume?
-CO increases by upto 7x during exercise (despite this cerebral blood flow is maintained). This increased CO is mainly due to increased HR
- during moderate exercise CVP does not significantly change, as venous return matches increased CO
However, at maximal exertion CVP does rise.
-intravascular volume is usually reduced due to increased insensible losses (Sweat, increased RR etc) and increased capillary filtration (?dilation to cool down?) this can also cause a slight ris in haematocrit
what is the effect of hypokalaemia on automaticity?
what is the effect of hypokalaemia on QT
hypokalaemia makes cardiac muscle RMP more negative, resulting in it being LESS EXCITABLE, bubt with increased automacity.
hypokalaemia prolongs the QT interval
what is the effect of hypercalcaemia and hyperkalaemia on RMP
both hypercalcaemia and hyperkalaemia make the RMP less negative (bringing it closer to the threshold potential)
hypercalcaemia decreases conduction velocity and shortens the refractory period.
what is the effect of magnesium on the PR interval
magnesium prolongs the PR interval
name the different drugs in the vaughan-williams classification of anti-arrhythmic drugs
