Cardiac phys Flashcards
When is the left ventricle perfused?
During diastole
When is the right ventricle perfused?
During systole and diastole
What percentage of oxygen does the heart extract?
60-70%
What are the endogenous regulators of coronary blood flow?
Adenosine
Nitric oxide
Adrenergic stimulation
When does CBF become exhaused?
when 90% of flow is blocked by stenosis of the coronary artery
What is resistance directly proportional to?
The viscosity of blood and length of the vessel
What is resistance inversely proportional to?
R4
Where is the site of greatest resistances?
arterioles
Where is the largest pressure drop in the systemic circulation?
In the arterioles because they are the area of high resistance
When is systolic BP measured?
After the heart contracts
When is diastolic BP measured?
when the heart is relaxed and blood is returning to the heart
What is pulse pressure?
The difference between systolic and diastolic pressure
What is atrial pressure measured with?
Swan ganz catheter. = PCWP
What is phase 1 of the cardiac cycle?
Atrial systole seen as the P wave and a wave
Contributes 25% of ventricular filling
What is phase 2 of the cardiac cycle?
Isovolumetric ventricular contraction:
begins after the onset of the QRS wave
When do the AV valves close?
When pressure in the ventricle exceeds that in the atria
What is phase 3 of the cardiac cycle?
Rapid ventricular ejection
When does the aortic valve open?
Phase 3 when ventricular pressure exceeds aortic
What is happening with the S1 heart sound?
The mitral and tricuspid valve close
What is happening with the S2 sounds?
The aortic and pulmonic valve close
What wave on the EKG marks the end of phase 3?
T wave
What is phase 4 of the cardiac cycle?
Reduced ventricular ejection: pressure in the ventricles and aorta decrease as blood flows into the arterioles
What is phase 5 of the cardiac cycle?
Isovolumetric ventricular relaxation: end of the T wave
Aortic and pulmonic valves close (S2)
Dicrotic notch is seen after closure of the aortic valve
Ventricular pressure decreases
ALL VALVES ARE CLOSED
How is action potential created in cardiac muscle?
Due to the option of fast sodium channels and calcium channels
When does the mitral valve open?
When ventricular pressure becomes less than atrial pressure
What is phase 6 of the cardiac cycle?
Rapid ventricular filling (S3)
What is phase 7 of the cardiac cycle?
Reduced ventricular filling:
dependent on HR
longest phase of the cardiac cycle
What is a dromotropic effect?
Effects on AV conduction
What is a ionotropic effect?
Effects on contractility
What is a lusitropic effect?
effects on diastole
What is the main NT of the SNS?
NE - is chronotropic, inotropic and lusitropic
What is the main NT of the PNS?
Ach
What governs the main resting tone of the heart?
PNS
What do the baroreceptors in the aortic arch respond to?
An increase in BP, but not a decrease
What happens in the carotid sinus when there is decreased BP?
Decreased stretch, decreased firing of CN IX so decrease PNS by vasomotor center in brain and increase SNS —> Inc. HR, contractility
What happens when there is a decrease in renal perfusion?
JG cells of afferent arteriole release renin
What does renin do?
Converts angiotensiogen to angiotensin
What converts angiotensin 1 to angiotensin 2?
ACE
What does angiotensin 2 do?
Increase thirst
Vasoconstriction (inc. MAP and TPR
Stimulates aldosterone synthesis and release in adrenal cortex
What causes the release of ADH in volume depletion?
Atrial receptors sense the decreased volume and cause release of ADH from posterior pituitary
What does ADH do?
vasoconstriction
water reabsorption in distal tubules and collecting ducts
What does ANP do?
Causes arteriole dilation
Natriuresis
Inhibits renin secretion
What is the carotid sinus reflex?
Massage carotid senses stretch –> increased firing of CN IX so sends signal to vasomotor center which decreases SNS and increases PNS tone to slow HR/contractility. Used for SVT
What is the Bainbridge reflex?
Atrial stretch causes an increase in HR, leading to increased CO
What is the abdominal reflex?
Decreased HR with stretch of abdominal viscera
What is the Cushing reflex?
Increased ICP causes cerebral ischemia and an increase in MAP through SNS (due to peripheral constriction to try to preserve blood flow to the brain) with a decrease in HR
What is the oculocardiac reflex?
A decrease in HR with IOP or stretching of ocular muscles
Which inhalation anesthetic increases PVR?
Nitric oxide
Which inhalation anesthetics have the greatest effect on HR?
Isoflurane/Des
Which induction agent preserves CO and contractility?
etomidate and midazolam
What induction agent causes an increase in HR, MAP and CO?
Ketamine
What is the MOA of Ketamine?
Stimulates SNS
Inhibits uptake of NE
What happens in cor pulmonale?
RV dilation
Decreases stroke volume due to ventricular interdependence (ballooning of right heart into the left heart)
What is the equation for MAP?
MAP = SVR X CO/80 + CVP
What is the equation for coronary perfusion pressure?
MAP- LVEDP
