cardio Flashcards
fick principle?
CO = (rate of O2 consumption) / (arterial O2 - venous O2 content)
formulae for MAP?
MAP = CO x TPR
MAP = 1/3 SysBP + 2/3 DiaBP
what is pulse pressure proportional to?
proportional to SV
inversely proportional to arterial compliance
how is CO maintained in exercise?
early stages: increase in HR and SV
late stages: increase in HR only (SV plateaus)
when HR increases, what phase of cycle is shortened?
diastole leads to less filling time –> decreased CO
causes of increased pulse pressure?
hyperthyroidism
aortic regurg
being old (aortic stiffening)
OSA (increased sympathetic tone)
exercise
causes of decreased pulse pressure?
aortic stenosis
cardiogenic shock
tamponade
advanced HF
factors that affect stroke volume?
contractility
afterload
preload
factors that increase contractility?
catecholamines
increased intracellular Ca
decreased extracellular Na
digitalis
mechanism of catecholamines –> increased contractility?
increased activity of Ca pump in SR
factors that decrease contractility?
B-blockade
HF with systolic dysfn
acidosis
hypoxia/hypercapnia
non-DHP CCBs
narcotic overdose
mechanism of BBs decreasing contractility?
decreased cAMP
Laplace’s law?
wall tension = ( P x radius) / (2 * wall thickness)
which mx decrease both preload and afterload?
ACEs and ARBs
formula for resistance (based on viscosity length and radius)?
resistance = driving P / flow
= (8 * viscosity * length) / (pi * radius^4)
resistance of vessels in series vs in parallel?
series: TR = R1 + R2 + …
parallel: 1/TR = 1/R1 + 1/R2 + …
how does organ removal affect TPR and CO?
increases TPR
decreases CO
which vessels account for majority of TPR?
arterioles
how does spinal anesthesia affect venous return?
decreases it
identify marked components of jvp tracing?
a wave = atrial contraction
c wave = RV contraction
x descent = atrial relaxation during ventricular contraction
v wave = atrial filling
y descent = RA emptying into RV
factors that contribute to normal splitting?
inspiration –> decreased thoracic pressure
decreased pulmonary impedance –> increased pulmonary capacitance
** both cause delayed closure of pulmonic valve –> delayed P2
what causes wide splitting?
conditions that delay RV emptying
** pulmonic stenosis, RBBB
what causes fixed splitting?
ASD –> increased RA and RV volumes –> increased pulmonic flow
what causes paradoxical splitting?
conditions that delay aortic valve closure
** aortic stenosis, LBBB
sustained hand grip affects murmurs in what way?
increases afterload –>
increases MR, AR, VSD murmurs
decreases HOCM murmurs
later onset of MVP click
valsalva affects murmurs in what way?
decreases preload –>
decreases intensity of most murmurs
** increases HOCM and MVP (earlier click/murmur)
squatting affects murmurs in what way?
increases preload –>
decreases HOCM and MVP
** increases intensity of AS murmur
causes of MR?
ischemic heart disease (post MI)
MVP
LV dilation
rheum fever/endocarditis
what causes systolic click in MVP?
tensing of chordae tendineae
which channels contribute fo phase 0 of myocardial AP?
voltage-gated Na channels
what channels in phase 1 of myocardial AP?
inactivation of Na channels
opening of K channels
what channels in phase 2 of myocardial AP?
= plateau
Ca influx balances K efflux
** Ca influx triggers Ca release from SR –> contraction
what channels in phase 3 of myocardial AP?
Ca channels closed
voltage gated slow K channels open –> massive K efflux
what channels in phase 4 of myocardial AP?
= resting potential
high K permeability through K channels
myocardial vs skeletal mm contraction?
1) cardiac AP has plateau
2) cardiac contraction due to Ca-induced Ca release
3) myocytes coupled by gap jcts
4) nodal cells spontaneously depolarize
myocardial vs pacemaker AP?
1) phase 0 in nodal: mediated by Ca channels (Na channels permanently inactivated bc resting voltage less negative)
2) phase 1 and 2 absent
3) phase 4: If - Na conductance –> slow spontaneous diastolic depol
what do ACh and adenosine do to the rate of nodal depol?
decrease it
–> decrease HR
what do catecholamines do to the rate of nodal depol?
increase it –> increase HR
how does sympathetic stimulation affect nodal cells?
increases chance that If channels are open –> increases HR
speed of conduction of heart tissues?
Purkinje > atria > ventricles > AV node
conduction pathway in heart?
SA –> atria –> AV –> common bundle –> bundle branches –> fascicles –> Purkinje –> ventricles
where is the AV node?
in posteroinferior interatrial septum
** blood supply from RCA
** 100 msec delay –> time for ventricular filling
drugs that cause long QT?
ABCDE:
anti-arrhythmics (IA, III)
anti-biotics (macrolides)
anti-Cychotics
anti-depressants
anti-emetics (ondansetron)
congenital long QT, AD, purely cardiac?
Romano Ward
congenital long QT, AR, deaf?
Jervell and Lange-Nielsel
Asian, AD, pseudo-RBBB and V1-V3 ST elevations?
Brugada
** increased risk of VT and SCD
** give ICD
what’s the bundle of Kent?
accessory pathway in WPW
causes of Afib?
HTN
CAD
rheumatic heart dz
binge drinking
HF
valvular dz
hyperthyroidism
MOA of ANP/BNP?
increase cGMP
–> vasodilation and decreased Na reabs in collecting tubule
–> vasodilation of afferent arteriole
–> vasoconstriction of efferent arteriole
** aldosterone escape
how does aortic arch transmit info to brain?
vagus –> solitary nucleus of medulla
how does carotid sinus transmit info to brain?
glossopharyngeal –> solitary nucleus of medulla
does hypoT cause increase or decrease in baroreceptor firing?
causes DECREASE in firing (b/c of DECREASED stretch)
how does decreased baroreceptor firing affect the heart?
vasocontriction
increased HR, contractility, BP
how does increased baroreceptor firing affect the heart?
increased AV refractory period
what stimuli do the carotid and aortic bodies respond to?
PO2 decrease (once below 60 mmHg)
increased PCO2
decreased pH
what stimuli do central chemoreceptors respond to?
ONLY changes in pH and PCO2 of interstitial fluid of brain
** no direct response to PO2
what factors affect autoreg of blood flow to heart?
adenosine
NO
CO2
decreased O2
** all vasodilatory
what factors affect autoreg of blood flow to brain?
CO2, pH - vasodilatory
what factors affect autoreg of blood flow to kidneys?
myogenic and tubuloglomerular feedback
what factors affect autoregulation of blood flow to lungs?
hypoxia –> VASOCONSTRICTION
** opposite of other vasculature - prevents perfusion of poorly ventilated area
what factors affect autoregulation of blood flow to skeletal mm?
local metabolites during exercise: lactate, adenosine, K, H, CO2 –> vasodilation
at rest: sympathetic tone
what factors affect autoregulation of blood flow to skin?
sympathetic stimulation –> temperature control
