ITE Chiefs Review Flashcards
What does P wave represent?
electrical activation of atria; precedes atrial contraction
Atrial systole contributes to __% of filling of ventricle
25%
What does QRS represent?
electrical activation of ventricles
What does T wave represent?
ventricular repolarization; marks end of ventricular contraction/rapid ejection
What action begins after QRS wave?
isovolumetric contraction
What is normal LVEDV?
120 mL
What is the average stroke volume?
80 mL
What are the three parts of systole?
- isovolumic contraction
- rapid ejection (2/3 LVEDV)
- slower ejection
What are the four parts of diastole?
- isovolumic relaxation
- early filling (70-75%)
- diastasis (<5%)
- atrial systole (15-20%)
____ = amt of blood per minute
cardiac output
What four things affect cardiac output?
- preload (LVEDV)
- afterload (aortic pressure/BP)
- myocardial contractility (inotropy)
- HR (chronotropy)
The primary determinant of myocardial O2 consumption is ___.
HR
Formula for CO
CO = HR x SV
Formula for Ohm’s law
Q (output) = pressure/resistance
An increase in ___ is most likely to result in increased myocardial wall tension
ventricular cavity size
What causes LVH?
chronic HTN (increased pressure load on LV) causes hypertrophy => decreased wall tension
Formula for LaPlace’s law
T = Pr/2h
- T(ension)
- P(ressure)
- r(adius) of chamber
- h = wall thickness
Why do you diurese/venodilate CHF?
reduces preload => decreased radius, decreased wall tension, less myocardial O2 consumption
What happens to heart with decompensated HFrEF?
increased r and thin myocardium (decreased h) => increased wall tension
How is parasympathetic innervation of heart accomplished?
craniosacral: long preganglionic fibers with short postganglionic fibers in heart
Function of parasympathetic innervation of heart?
- slows HR
- reduces conduction velocity
What is the primary neurotransmitter for parasympathetics?
ACh
What neurotransmitters are involved in sympathetic innervation of heart?
- ACh (stellate gang synapse)
2. NE (postganglionic)
How is heart innervated sympathetically?
thoracolumbar; synapse in stellate ganglion
Through what receptors in the heart does sympathetic innervation work?
beta-1: increases rate and conduction cells
What is the Bezold Jarisch reflex?
incr ventricular volume => vagal => decreased HR and MAP
Effects of sympathetic stimulation in heart?
- chronotropic
- dromotropic incr conduction velocity)
- inotropic
- lusitropic (incr rate of myofibrillar relaxation)
____ = systemic HTN in response to increased ICP
Cushing reflex
attempt to maintain cerebral perfusion/O2 delivery
What is the occulocardiac reflex?
pressure on ocular globe => brady, hypoT
What are the two types of sensitive receptors involved in heart innervation?
- baroRs (arterial; depends on arterial BP)
2. chemoRs (periph; senses incr PaCO2, decr in pH)
During off pump CABG, a clamp is placed on a coronary artery. New onset junctional rhythm is seen on the EKG monitor and new inferior wall motion abnormalities are seen on TEE. What coro is affected?
RCA
What makes up the L main?
L main = LAD + L circumflex
What part of heart does the right main cover?
- ant/post RV wall
- RA
- SA node
- upper half of atrial septum
- post 1/3 interventricular septum
- inferior LV wall
- AV node
- post base LV
What circulation supplies the SA node and the AV node?
R main
What does the LAD supply?
- anterior LV wall
- anterior 2/3 of interventricular septum
What does the L circumflex supply?
- lateral LV wall
- part of LV posterior wall
Wall abnormality associated with RCA
RCA = inferior wall
Wall abnormality associated with LAD
LAD = anterior wall
Wall abnormality associated with circumflex
circumflex = lateral wall
Formula for coronary perfusion
coronary perfusion = aortic pressure (DBP) - LVEDP
What is resting coronary blood flow, and how much of cardiac output does it make up?
250 mL/min
5% of CO
What layer of heart tissue is most at risk for ischemia?
subendocardium
What does the Frank-Starling curve describe?
contractile state of myocardium
What three things are inotropic?
- catecholamines
- digitalis
- sympathetic stimulation
What two things are negative inotropes?
- pharm depressants
2. loss of myocardium
In what 4 cases is PAOP > LVEDP?
PAOP > LVEDP:
- mitral stenosis
- L atrial myxoma
- pulm venous obstruction
- elevated alveolar pressure
In what 3 cases is PAOP < LVEDP?
PAOP < LVEDP:
- aortic regurg
- stiff LV
- LVEDP > 25 mmHg
25 yo man with known rheumatic heart disease is being evaluated in the ICU. Despite decreasing C.O., mixed venous blood from a PAC shows an increase in SvO2. Why?
wedging of catheter
The acute onset of hypotension without a decrease in mixed venous oxygen saturation in most likely associated with the onset of ____.
sepsis
In a patient with hypovolemic shock, what factor is the best measure of the overall balance between oxygen supply and demand?
mixed venous O2 sat
Formula for SvO2
SvO2 = SaO2 - (vO2/1.3 x CO x Hg)
What is a normal mixed venous O2 sat?
70%; 40 mmHg
With what tool must you measure mixed venous O2 sat?
PAC
With what tool must you measure mixed venous O2 sat?
PAC
What are the two broad reasons for decreased SvO2?
- incr O2 consumption
2. decr O2 delivery
What are the four things that decrease SvO2 by increasing O2 consumption?
- fever
- shivering
- MH
- thyroid storm
What are the four things that decrease SvO2 by decreasing O2 delivery?
- hypoxia
- decreased CO
- decreased Hgb (hemorrhage)
- abnormal Hgb
Effect on SvO2:
fever
decreased SvO2
Effect on SvO2:
shivering
decreased SvO2
Effect on SvO2:
MH
decreased SvO2
Effect on SvO2:
thyroid storm
decreased SvO2
Effect on SvO2:
hypoxia
decreased SvO2
Effect on SvO2:
decreased CO
decreased SvO2
Effect on SvO2:
decreased Hgb
decreased SvO2
Effect on SvO2:
abnormal Hgb
decreased SvO2
Effect on SvO2:
L=>R shunting
increased SvO2
Effect on SvO2:
high CO
increased SvO2
Effect on SvO2:
cyanide
increased SvO2
Effect on SvO2:
hypothermia
increased SvO2
Effect on SvO2:
sepsis
increased SvO2
Effect on SvO2:
wedged PA
increased SvO2
What are some broad reasons for increased SvO2?
- L=>R shunt
- high CO
- impaired tissue uptake
- decr O2 consumption
- sepsis
- sampling error
Thermodilution is used to measure ___.
CO
What two issues invalidate thermodilution?
Why?
- tricuspid regurg
- cardiac shunts
only RV output is measured
How does thermodilution work?
- known amt of fluid injected in proximal port of PAC (into RA)
- temp measured at tip of PAC (in pulm a.)
- temp change is inversly proportional to CO
What three things cause falsely high CO by thermodilution?
- too little injectate
- TR
- cardiac shunts
Which of these are contraindicated in pulm HTN?
a) 15-methylprostaglandin F2alpha
b) sildenafil
c) nitric oxide
d) epoprostenol
15-methylprostaglandin F2alpha
MC sx associated with pulm HTN?
- incr SOB with activity
- CP at low exertion
- fatigue
- lethargy
- fainting
- leg swelling
What is the definition of pulm HTN?
mean PAP > 25 mmHg at rest
What are the 5 classifications of pulm HTN?
- PAH
- 2/2 L-sided heart dz
- 2/2 lung dz/hypoxia
- chronic thomboembolic pulm HTN
- unclear/multifactorial
What are some predictors of poor outcome with surg/anesth?
- poor exercise capacity (6-min walk)
- elevated RA pressure
- decreased RV fxn/failure
- low CI
- elevated BNP
- elevated CRP
Moderate/severe pulm HTN is a contraindication for ____.
liver transplant
What are some goals for anesthetizing people with pulm HTN?
- prevent hypoT
- tx hypoT with phenylephrine, vasopressin, NE
- maintain adequate preload/contractility
- prevent hypoxia, hypercapnia, acidosis
Three classes of tx for pulm HTN?
- prostacyclins (epoprostenol infusion, iloprost inhaled)
- PDE inhibitors (sildenafil, tadalafil, milrinone)
- consider inhaled NO
What is protamine?
only compound that reverses heparin
basic compound that binds acidic residues of heparin
What happens in a protamine reaction?
pulm HTN:
- heart pressure equalize = tamponade
- CO decr, PVR decr, SVR incr
What causes protamine reaction
increased plasma thromboxane
How do you treat a protamine reaction?
can do:
- epi
- heparin/bypass
What are the four components of the pathophysiology of protamine reaction?
- coagulopathy
- histamine release
- IgE-mediated (type II): d/t prev sensitization (NPH, fish allergy, vasectomy)
- anaphylactoid rxn (type III): complement/IgG; TXA2 release => severe pulm vasoconstriction, pulm HTN, possible R heart failure
A 77 yo woman with a biventricular implantable cardioverter-defibrilator (ICD) device is scheduled for an elective thyroidectomy. Interrogation of her device 2 days ago revealed 99.9% of beats were paced in DDD mode at 60 bpm. Per report, there is no underlying (intrinsic) cardiac rhythm. How do you prevent pacemaker inhibition by surgical electrocautery?
reprogramming pacer to asynchronous mode
Name four ways to inhibit/inactivate programmable DVI pacemaker.
- myopotentials from shivering
- succ-induced fasciculations
- ventricular R wave
- magnet over it
T or F: AICDs are not affected by ECT.
true
Name four things that affect AICDs.
- MRI
- radiation
- unipolar cautery
- radiofreq ablation
Given the complete general defibrillator code of VVE-DDDRV, what is true about this ICD?
provides ventricular chamber antitachycardia pacing
What are the five parts of pacer codes, and what are the options for these?
1st = chamber paced
-0 (none), A, V, D (dual)
2nd = chamber sensed
-0, A, V, D
3rd = response
-0, T (triggered), I (inhibited), D
4th = programmability/rate modulation
-0, P, M, C, R
5th = antitachy fxn
-0, P, S, D
What are the four parts of ICD codes, and what are the options for these?
1st = shock chambers
-0, A, V, D
2nd = antitachy pacing chambers
-0, A, V, D
3rd = tachy detection
-E (electrogram), H (hemodynamic)
4th = antibrady pacing chambers
-0, A, V, D
What are the parts of the CPB machine?
- reservoir = grav-dependent; accumulates deoxy blood from venous circ
- heat exchange (uses water countercurrents)
- oxygenator (membrane or bubble)
- filter system
then returned to ascending aorta