CC3: Normal pressures Flashcards
What are the 2 types of blood pressure?
-Systemic
-Pulmonary
How do we obtain invasive blood pressure?
-Catheter connected at its proximal end to a pressure monitoring transducer
-Transducer converts mechanical waveforms from circulatory system into electrical waveform
-Waveforms are recorded individually as catheter passes through heart and vessels
How do you access right and left heart?
Right heart: Vein (e.g. femoral)
Left heart: Artery (e.g. radial)
Journey of catheter to left heart?
-Femoral artery
-Descending aorta
-Ascending aorta
-Aortic valve
-Left ventricle
What type of pressure trace is this?
-Arterial trace
-Systolic > 100 = systemic, not pulmonary
What is the difference between left side and right side arterial pressure traces?
-Same shape
-But right side has lower values
-E.g. Pulmonary artery <30 systolic
Describe arterial pressure trace
-Starts when aortic valve opens
-Sharp upstroke which reflects ejection of blood from left ventricle
-Normal systolic = 100-140
-Normal diastolic = 60-90
What does diastolic pressure relate to and what can increase it?
-Relates to the amount of recoil in the arterial system
-Fast heart rate, shorter diastolic time, less time for run off into distal branches, higher diastolic pressure
Why does the diastolic value in arterial pressure trace never drop to zero?
-Aorta is a strong, thick-walled vessel
-Pressure is maintained so that even at peripheries, all cells are supplied with oxygen
What is the anachrotic notch?
-During first phase of ventricular systole, (isovolumetric contraction), a presystolic rise may be seen
-This occurs before the opening of the aortic valve
What is the dichrotic notch?
-Aorta has greater pressure than left ventricle
-Blood flow attempts to equalise by flowing backwards
-Causes closure of aortic valve
-Marks end of systole and beginning of diastole
What is the pulse pressure?
-Difference between systolic and diastolic pressure
What factors affect pulse pressure?
-Changes in stroke volume
-Aortic regurgitation
-Changes in vascular compliance
Aortic compliance
What is the mean arterial pressure (MAP) and how do we calculate it?
-an approximation of a time-weighted average of blood pressure values in large system arteries during the cardiac cycle
What type of pressure trace is this?
-Left Ventricular
-Falls close to zero
What features make up the left ventricle?
-Thickest wall
-Left common bundle (left anterior/posterior fascicle)
-Aortic valve (3 cusps)
What is the normal area of aortic valve?
2.5-3.5cm^2
What happens during ventricular systole?
Isovolumetric contraction
-all 4 valves closed
-after closure of mitral, before opening of aortic
-rapid rise in pressure until it exceeds aortic pressure and aortic valve opens
Ejection phase
-blood flows into aorta until aortic valve closes
What happens during ventricular diastole?
-Relaxation of the ventricle allows ventricular filling
(aortic valve closes and mitral valve opens)
Diastasis
-later, slower period of filling when left ventricle is nearly full
-pressure in LV = pressure in LA
What is the EDV?
-End Diastolic Volume
-Amount of blood in the ventricles before heart contracts
What 2 positions can EDP be measured at?
-Pre-A (beginning of R wave)
-Post-A (peak of R wave)
Journey of catheter to right heart?
-SVC/IVC
-RA
-Tricuspid valve
-RV
-Pulmonary artery
-Pulmonary capillary wedge (LA)
How much does does atrial kick contribute to ventricular filling
-Active filling due to atrial contraction contributes 30% of Ventricular filling
Which 3 vessels drain into right atrium?
-SVC
-IVC
-Coronary sinus
What is the area of the tricuspid valve and how many leaflets?
5-10cm^2
3 leaflets
Which pressure trace is this?
-Atrial/venous
What do A wave and V wave represent?
A wave
-Generated when atrium contracts
-Causes pressure increase in atrium
-Occurs after P wave
V wave
-Increase in pressure during ventricular systole
-Occurs after T wave
What do C, X and Y waves represent?
X descent
-Fall in pressure following a wave (represents atrial relaxation)
Y descent
-Fall in pressure following v wave
(represents opening of AV valve)
C wave
-May occur as interruption of X descent and represents movement of AV valve towards atrium during closure
What are the normal pressure values for right ventricle?
-Systole <30
-Diastole <5
Causes of increased pressure in right ventricle
-Hypervolemia
-Pulmonary embolism
-COPD
-Pulmonary stenosis
-RV infarct/failure
-Pericarditis/tamponade
-Oytflow obstruction
-Primary and secondary pulmonary hypertension
-LV failure
What pressure trace is this?
-Right side because low values
-Arterial shape
-So pulmonary artery
What are the 3 pressure waveform traces?
-Arterial - Pulmonary artery/Aorta
-Ventricular - LV and RV
-Atrial/Venous
Causes of increased and decreased pressure in pulmonary artery?
Decreased:
-Hypovolemia
Increased:
-PHTN
-COPD
-ARDS
-PE
-Mitral stenosis
Mitral valve area and how many leaflets?
4-6cm^2
2 leaflets
Left atrial vs Right atrial pressure
-Similar waveform
-A wave and V wave larger in left atrium due to lower compliance
What is Pulmonary Capillary Wedge (PCW)?
-Used to assess LA pressure
-Based on assumption that pressure in pulmonary capillaries = LA
-Catheter is wedged into pulmonary capillaries, giving
indirect LA pressure measurement
-Estimates LVEDP so is an indicator or LVEDV
How would you obtain direct LA pressure measurement?
-Patent Foramen Ovale
-Trans-septal technique using puncture (Brockenborough) technique
Normal PCW pressure
6-12mmHg
-PCW > 18mmHg suggests left heart failure
-Used to quantify degree of mitral stenosis/pulmonary hypertension
What causes increase/decrease of PCW?
Decrease:
-Hypovolemia
Increase:
-Mitral stenosis/regurgitation
-Aortic stenosis/regurgitation
-LV ischaemia/infarct
-LV failure
Summary of right heart pressure
Normal values
LV-AO pullback
-Measures pressure gradient between left ventricle and aorta
-Aortic stenosis?
Mean pressure difference
-2 pressure traces
-Compares difference in mean pressure between left ventricle and aorta
LV and PCW
-Measures pressure difference between LA and LV
A wave > V wave = MS
V wave > A wave = MR
What is this?
-No pulmonary valve defect because no pressure gradient
-But pulmonary hypertension due to systolic pressure of 57mmHg
Which pullback are these?
-LV -> Aorta
-PA -> RV
Systolic BP values by age
How to work out which pressure waveform?
