Apex Cardiac WB KEY Flashcards
How is cardiac muscle like skeletal muscle and neural tissue?
- have myosin and actin, can contract
- T-tubule system and SR maintain Ca2+ homeostasis for contraction and relaxation
How is cardiac muscle DIFFERENT from skeletal muscle and neural tissue?
They have tight Junctions and they contain more mitochondria and skeletal muscle cells.
Neural tissue is similar to cardiac in the sense that they can
propagate an action potential.
Ability to spontaneously generate an AP is known as
Automaticity
Conductance : open channels, closed channels
Increase conductance; decrease conductance.
What is the RMP? Which is more negative inside or outside?
The difference in electrical potential between the inside and the outside of the cell.
Inside is NEGATIVE relative to the outside
RMP is established by what 3 mechanisms?
- Chemical force
- Electrostatic counter force
- Na/K ATPase
What predicts an ion’s equilibrium potential?
NERNST Equation.
When is equilibrium established?
When there is no concentration gradient and NO net flow of ions. Charge inside balanced with charge outside.
How much K+ INSIDE the Myocyte?
135 mM
How much Na+ INSIDE the Myocyte?
10 mM
How much Cl- INSIDE the myocyte
4 mM
How much Ca2+ INSIDE the myocyte
10mM (-4)
How much K+ OUTSIDE the Myocyte, meaning in ECF?
4 mM
How much Na+ OUTSIDE the Myocyte, meaning in ECF?
145 mM
How much Cl- OUTSIDE the Myocyte, meaning in ECF?
114 mM
How much Ca2+ OUTSIDE the Myocyte, meaning in ECF?
2mM
When is the cell easier to depolarize
When RMP is closer to TP
When is the cell harder to depolarize
RMP is further from TP
When there is a decrease in polarity across a membrane / less charge difference between inside and outside of the cell is known as
Depolarization, and results in AP.
Restoration of RMP following a depolarization known as
Repolarization
Increase in polarity across a membrane , where there is a larger charge difference between inside and outside of the cell Is known as
Hyperpolarization
Why is the inside of the cells more negative than outside of the cell?
Because the myocyte is permeable to K+ but not other ions or proteins and CONTINUOUSLY LEAK K+ causing them to lose their POSITIVE CHARGE.
When serum K+ decreases, RMP become more ________and the myocyte becomes more ________
Negative , Hyperpolarized
When serum K+ increases, RMP become more ________and the myocyte becomes more ________
more positive, depolarize more easily
What is the primary determinant of RMP?
K+
When the cell is at rest, Na+ permeability is____compared to K+ permeability (high or low)
Low
When RMP approaches TP voltage gated Na+ Channels _______ and _______ conductance cell
Open and increase Na+ conductance –> cell depolarization
Sodium-Potassium ATPase: ions movement
3 Na+ out
2 K+ in
For the VENTRICULAR ACTION potential, The RMP is ______mV and the TP is ____mV
- 90 mV
- 70 mV
What happens during Phase O of the Ventricular action potential? how?
SODIUM rushes IN
How: The cells reaches the threshold potential of -70mV and Depolarizes
Fast voltage-gated Na+ channels is activated.
What happens during Phase 1 of the Ventricular action potential? how?
Initial repolarization
Na+ channels become inactivated so cell becomes less positive
K+ channels open and Cl- channels open
What is ion movement during phase 1 of the Ventricular action potential?
K+ out
Cl - in
What happens during Phase 2 of the Ventricular action potential? how?
Slow Ca2+ channels counters loss of K+ ions = Maintains depolarization
Delays repolarization
Na+ channels stay in the inactivated state
What is ion movement during phase 2 of the Ventricular action potential?
K+ Out
Ca2+ IN
Absolute refractory period and Phase II
Phase II prolongs the absolute Refractory period
In which phase is the fast Na+ Channel maintained in the inactivated state?
Phase II
What is ion movement during phase III of the Ventricular action potential?
Final Repolarization
K+ Out
Ca2+ IN (briefly)
What is ion movement during phase IV of the Ventricular action potential?
Resting phase
In what phase does the K+ leaves faster than the Ca2+ enters?
Plateau phase (II)
Resting phase ion movement is
Na+ out
Removes Na+ gained during repolarization
Replaces K+ lost during depolarization
What are the 3 tissues with no plateau phase?
SA nodal tissue
AV nodal tissue
Neural Tissues
Describe the anatomy of the conduction pathway –> What are the 2 types of cells?
P cells that functions as pacemakers
Transitional cells
What are the function of the transitional cells ?
Direct electrical impulses away from the SA node.
Conduction pathway –> Path
SA node –> Internodal tracts –> AV node –> Bundle of His –> Left and Right Bundle Branches –> Purkinje Fibers.
SA node firing rate? When can it be different?
70-80 bpm ; denervated heart
AV node firing rate?
40-60 bpm
Purkinje fibers rate?
15-40 bpm
What determines the heart rate?
Rate of Phase 4 Depolarization of SA node
Each cell is capable of _________ with different rate
Automaticity
Cells with ______rate determines heart depolarization
Fastest
Which artery supplies the SA node?
Posterior Descending Artery
3 ways to increase the HR?
- Increase the rate of spontaneous phase 4 depolarization
- Phase 4 remains constant, but TP becomes more negative (there is a shorter distance between the RMP and TP).
- Phase 4 remains constant, but RMP becomes less negative (Shorter distance between RMP and TP).
At rest, which tone dominates PNS or SNS?
PNS tone exceeds SNS tone
SNS stimulation of cardiac accelerators fibers (T1-T4) via NE increase HR how?
by increasing Na+ and Ca2+ conductance –> Increased rate of spontaneous phase 4 depolarization.
What nerve innervates the SA node?
Right Vagus Nerve
What nerve innervates the AV node?
Left Vagus nerve
SA node action potential 3 Phases
Phase 4
Phase 0
Phase 3
SA node action potential phase 4
Spontaneous depolarization
Na+ In through funny current channel (because it’s activated by HYPERPOLARIZATION not DEPOLARIZATION
At -50mV , transient Ca2+ channels (T-type open to furter DEPOLARIZE the CELL
SA node action potential phase 0
Depolarization
Ca2+ In (L-TYPE) . Ca2+ enters via L-type Ca2+ channels leading to depolarization
Na+ and T-type channels CLOSE
SA node action potential phase 3
Repolarization
K+ OUT
(K+ Channels open and K exits the cells, inside of cell becomes more negative –> depolarization and return to phase 4 occurs.
Repolarization in phase 3 means there is a
Decrease Ca2+ conduct by closing L-type Ca2+ Channels
Oxygen Delivery (DO2) determines what?
How much O2 is being delivered to the tissues
Oxygen Delivery (DO2) formula
CO x {(1.34 x Hgb x SaO2) + (PaO2 x 0.003) x 10
*10 converts g/dL to L/min of CO
DO2 Is approximately_______
1000 ml/min
CaO2 determines what?
How much O2 is carried in arterial blood
CaO2 is about how much?
20 mL/dL
What is EO2?
How much O2 is extracted by the tissues
EO2 is approximately what percentage?
25%
What is VO2 ?
How much O2 is consumed by the tissues
What is the VO2 ?
250 mL/min
What is CvO2?
How much O2 is carried in the venous blood
What is the CvO2?
15 mL/dL
What 3 determines the amount of O2 carried by Hgb?
Hgb, SaO2 and 1.34
What is the constant 1.34 tells us?
The maximum occupancy of boxcars.
What does Hgb tells us?
How many boxcars available to carry O2.
What does SaO2 tells us?
How full the boxcars are.
2 parts of the DO2 equation
Amount of O2 carried by Hgb (1.34 x Hgb x SaO2).
Amount of O2 dissolved in the blood (PaO2 x 0.003)
Amount of O2 dissolved in the blood determinants
PaO2 and 0.003
Ohm’s law formula
Current = Voltage difference / Resistance
Flow (Ohm’s law )
Pressure gradient/ Resistance or
Q = 🔺P / R
MAP formula (Ohm’s Law)
MAP = (CO x SVR) + CVP / 80
Flow Hemodynamic term is_____symbol ____
CO ; Q
Pressure Gradient Hemodynamic term is______symbol_____
MAP - CVP ; P1 -P2 or 🔺P
Resistance Hemodynamic term is______symbol_____
SVR ; R
Hyponatremia causes the extracellular fluid to become hypotonic. As this occurs,
water begins moving into the brain cells causing cerebral edema and intracranial hypertension.
The treatment of choice for patients with hyponatremia and an elevated total body sodium is
Water restriction
What is the most common cause of death in a patient with LVAD?
Sepsis
In the absence of a pulse, for LVAD device, what won’t work?
Pulse ox and NIBP ineffective
LVAD is highly dependent on what patient factors?
LV volume
What are the 3 most common complications of IABP from most frequent to least frequent?
Most common is VASCULAR injury
Followed by Infection at insertion site and thrombocytopenia.
Where is the tip of the ballon positioned for an IABP?
2 cm distal to the subclavian artery.
With IABP, inflation occurs during ________ and deflation occurs during_______
Inflation during diastole
Deflation during systole
2 Main advantages provided by IABP?
Decrease afterload –> Reduced LV work which decreases myocardial O2 demand.
What are the most difficult aneurysms to repair and why?
Crawford II and III because those aneurysms involve the thoracic and abdominal aorta.
Which crawford presents the most significant perioperative risk for paraplegia?
Crawford II
What is the perioperative risk of fixing a crawford II aneurysm repair? why? What should you?
The most significant perioperative risk including PARAPLEGIA and/or Renal failure because there is a mandatory period of stopping blood flow to the renal arteries, and some of the radicular arteries that perfuse the anterior spinal cord (Possibly including the artery of ADAMKIEWICZ).
Intervention to reduce the risk of ischemic injury
Is acute aortic dissection a medical or surgical emergency? What should you consider treating the patient as
Surgical emergency
Consider Aortic insufficiency in your anesthetic plan .
