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
