Physiology Flashcards
Cardiac output
Stroke volume x Heart rate
Cardiac output according to Fick’s principle
Rate of oxigen consumption / (arterial O2 content - venous O2 content)
Mean arterial pressure
CO x total peripheral resistance (TPR)
2/3 Dyastolic pressure x 1/3 systolic pressure
Pulse pressure
Systolic pressure - diastolic pressure
Pulse pressure is proportional to _______ and inversely proportional to ________
Stroke volume
Arterial compliance
End diastolic volume - end systolic volume
Stroke volume
CO is mantained by ____ and _____ during EARLY stages of exercise
Heart rate
Stroke volume
During LATE stages of exercise CO is mantained by
Heart rate only
Stroke volume plateaus
Preferentially shortened by high heart rate
Diastole
Isolated systolic hypertension in elderly
Aortic stiffening
Stroke volume depends on
- Contractility: directly
- Preload: directly
- Afterload: inversly
Contractility increases with
- Cathecolamine stimulation via B1 Rc
- Higher intracellular Ca
- Lower extracellular Na
- Digitalis (Blocks Na/K pump: more ic Na: less Na/Ca exchanger: more intracellular Ca)
Cathecolamine stimulation via B1 receptor effects
- Ca channels phosphorilated: more Ca entry: more Ca induced ca release and Ca storage in sarcoplasmic reticulum
- Phospholamban phosphorylation: active Ca ATPase: Ca storage in sarcoplasmic reticulum
Contractility decreases with
- Beta 1 blockade: less cAMP
- Heart failure with systolic dysfunction
- Acidosis
- Hypoxia/hypercapnia
- Non dihydropyridine Ca channel blockers
Myocardial oxygen demand increases with
- Contractility
- Afterload
- Heart rate
- Diameter of ventricle: more wall tension
Wall tension
Follows Laplace’s law:
Pressure x radius
Wall stress
Pressure x radius (tension) / 2 x wall thickness
Decreases preload
Venous vasodilators: nitroglycerin
Decreases afterload
Arterial vasodilators: hydralazine
Decrese preload and afterload
ACE inhibitors (IECA) ARB (ARA-II)
Chronic hypertension (increased MAP) produces
Left ventricle hypertrophy to overcompensate for high afterload in order to decrease wall tension
Ejection fraction
Stroke volume / End diastolic volume
Index of ventricular contractility
Ejection fraction
loss of contractility
- Loss of myocardium: myocardial infarct
- Beta blockers
- Non dihydropypiridine Ca
- Channel Blockers
- Dilated cardiomyopathy
Digoxine is a
Positive inotrope
_____ account for most of TPR
Arterioles
Highest cross-sectional area
Lowest flow velocity
Capillaries
Volumetric flow rate (Q)
Flow velocity x cross sectional area
Viscosity depends mostly on
Hematocrit
Viscosity increases in (examples)
Hyperproteinic states: multiple myeloma
Polycitemia
Viscosity decreases in
Anemia
Inotropic + effect
Cathecolamines
Digoxin
Inotropic - effect
Uncompensated HF
Narcotic overdose
Sympathetic inhibition
Increases venous return
Fluid infusion
Sympathetic activity
Decreases venous return
Accute hemorrage
Spinal anesthesia
Decreases total peripheral resistance
Exercise
AV shunt
Increase total peripheral resistance
Vasopressors
Period of the highest ventricular O2 consumption
Isovolumetric contraction
Isovolumetric contraction
Between mitral valve closing and aortic valve opening
Isovolumetric relaxation
Between aortic valve closing and mitral valve opening
Rapid filling
Period just after mitral valve opening
Reduced filling
Period just before mitral valve closing
Phases of left ventricle
- Isovolumetric contraction
- Systolic ejection
- Isovolumetric relaxatio
- Rapid filling
- Reduced filling
S1
Mitral and tricuspid valve closure
S2
Aortic and pulmonary valve closure
S3: when, meaning, pathological/normal
- Early diastole, during rapid ventricular filling
- High filling pressures: mitral regurgitation, HF
- Dilated ventricles, normal in children and young adults
S4: when, meaning, pathological/normal
- Late diastole, atrial kick
- High atrial pressure
- Ventricular noncompliance: hypertrophy: left atrium must push against stiff LV wall
- ABNORMAL, regardless of patient age
S4 is normal when
IT’s never normal, regardless of patient’s age
a wave (JVP)
atrial contraction
a wave is absent in
atrial fibrillation: a=atrial
c wave
RV contraction: c=contraction
Closed tricuspid valve bulging into atrium
x descent
Downard displacement of closed tricuspid valve during rapid ventricular ejection phase
v wave
high atrial pressure due to filling against closed tricuspid valve
y descent
RAtrium emptYing into RV
Prominent y descent
Constrictive pericarditis
Absent y descent
Cardiac tamponade
Normal splitting of S2 occours
During inspiration due to the higher venous return and higher RV filling because of the drop in intrathoracic pressure
Wide spitting of S2 occours in
Conditions that delay RV emptying:
- Pulmonic stenosis
- Right bundle branch block
Fixed splitting
Atrial septal defect: left to right shunt: higher Righ atrial and right ventricle volume
Paradoxical splitting
Delayed aortic valve closure:
-Aortic stenosis
-Left bundle branch block
On inspiration P2 moves closer to A2, thereby paradoxically eliminating the split
Increases intensity of right heart sounds
Inspiration
Increases intensity of hypertrophic cardiomyopathy murmur
Valsalva (phase II) Standing up (decreases preload)
Decreases intensity of hypertrophic cardiomyopathy
Handgrip
Squating
Hand grip…
Increases afterload:
- Less intensity of HCM
- More intensity of MR, AR, VSD murmurs
Decreases intensity of most murmurs
Valsalva phase II
Standing up
Earlier onset of MVP click/murmur
Valsalva
Standing up
Aortic stenosis murmur
Crescendo-decrescendo systolic ejection murmur
Click may be present
Aortic stenosis symptoms
SAD:
Syncope
Angina
Dyspnea
Most common cause of aortic stenosis
Age related calcification in older patients: >60 years old
Early onset calcification of bicuspid aortic valve
Mitral/tricuspid regurgitation: murmur characteristics
Holosystolic
High pitched: blowing murmur
MR is often due to
Ischemic heart disease: post-MI
Mitral valve prolapse
Left Ventricle dilatation
TR is often due to
Right ventricle dilatation
Most frequent valvular lesion
Mitral valve prolapse
Mitral valve prolapse: murmur characteristics
Late systolic crescendo murmur with midsystolic click
Midsistolic click in mitral valve prolapse is due to
Chordae tendinae sudden tensing
Mitral valve prolpase can be caused by
Myxomatous degeneration: Marfan, Ehler-Danlos
Rheumatic fever
Chordae tendinae rupture
Ventricular septal defect murmur
Holosystolic
Harsh-sounding
Loudest at tricuspid
Can predispose to infective endocarditis
Mitral valve prolapse
Pulsus parvus et tardus
Aortic stenosis: pulses are weak with a delayed peak
Aortic regurgitation murmur
High pitch
Early diastolic
Decrescendo
Watson’s water hammer pulse or corrigan pulse or magnus and celer pulse
Aortic regurgitation
Severe aortic regurgitation can produce _____ when severe and chronic
head bobbing
Aortic regurgitation is due to
Aortic root dilation
Bicuspid aortic valve
Endocarditis
Rheumatic fever
Interval between S2-OS and severity of mitral stenosis
Shorter interval=higher severity
Mitral stenosis murmur
Opening snap: abrupt halt in leaflet motion in diastole, after rapid opening due to fusion at leaflet tips
Mid to late diastolic murmur
Late and highly specific sequela of rheumatic fever
Mitral stenosis
Chronic Mitral Stenosis can result in
LA dilatation
Continuous murmur
Patent ductus arteriosus: continuous machine like murmur loudest at S2
Due to congenital rubella or prematurity
Phases of myocardial action potential
0: rapid upstroke and depolarisation
1: initial repolarisation
2: plateau
3: rapid repolarization
4: resting potential
Phase 0 of myocardial action potential
Rapid upstroke and depolarisation
Voltage gated Na channels open
Phase 1 of myocardial action potential
Initial repolarisation: inactivation of voltage gated Na channels
Voltage gated K channels begin to open
Phase 2 of myocardial action potential
Ca influx through voltage gated Ca channels balances K efflux
Ca influx from ECF triggers Ca release from sarcoplasmic reticulum and myocyte contraction
Phase 3 of myocardial action potential
Massive K efflux due to opening of voltage gated slow K channels and closure of voltage gated Ca channels
Phase 4 of myocardial action potential
Resting potential
High K permeability through K channels
3 differences cardiac muscle vs skeletal muscle
- Cardiac muscle action potential has a plateau, due to Ca influx and K efflux
- Cardiac muscle contraction requires Ca influx from ECF to induce Ca release from sarcoplasmic reticulum
- Cardiac myocytes are electrically coupled to each other by gap junctions
Refractory periods in cardiac cycle
- Absolute refractory period: no stimulus can cause depolarisation
- Effective refractory period: may allow for non propagated depolarization
- Relative refractory period: allows a normal than stronger stimuli to cause a full depolarization
- Supranormal period: hyperexcitable period, even a weak stimulus can trigger an action potential
Pacemaker action potentials occour in
SA and AV nodes
Phase 0 of pacemaker action potential
Upstroke: opening of voltage gated Ca channels
Phase 1 of pacemaker action potential
Doesn’t exist
Phase 2 of pacemaker action potential
Doesn’t exist
Phase 3 of pacemaker action potential
Inactivation of Ca channels and activation of K channels: K efflux
Determines HR
Slope of phase 4 in the Sa node
Adenosine effect on phase 4 of pacemaker action potential
Like ACh decreases the rate of diastolic depolarization and decreases HR
Phase 4 of pacemaker action potential
Slow spontaneous diastolic depolarisation due to If: funny current
If channels are responsible for a slow mixed Na/K inward current
AV node blood supply
Right coronary artery
pacemaker rates vs speed of conduction
SA>AV>Bundle of His>Purkinje/ventricles
Speed of conduction: Purkinje>atria>ventricles>AV node
Bachmann bundle
Conducts from AV node to left atrium
AV node location
Posterioinferior part of interatrial septum
PR interval
Time from start of atrial depolarization to start of ventricular depolarization
Usually less than 200 msec= 0.2 seg= 5 squares
QT interval
Ventricular depolarization
Mechanical contraction of the ventricles
Ventricular repolarisation
T wave
Ventricular repolarization
T wave inversion may indicate ischemia or recent MI
J point
Junction between end of QRS complex and start of ST segment
ST segment
Isoelectric, ventricles depolarised
U wave
Prominent in:
- Hypokalemia
- Bradycardia
Torsades de pointes
Ventricular tachycardia
Can progress to ventricular fibrillation
_________ predisposes to torsades de pointes
Long QT interval
Drug induced long QT
ABCDE AntiArrhythmics: class IA, III AntiBiotics: macrolides Anticychotics: haloperidol AntiDepressants: TCA AntiEmetics: ondansetron
Treatment of torsades de pointes includes
magnesium sulfate
Congenital long QT syndrome
Inherited disorder of myocardical repolarisation typically due to ion channel defects
Increase risk of sudden cardiac death (SCD) due to Torsades de Pointes
Congenital QT syndrome includes
- Romano-Ward syndrome
- Jervell and Lange-Nielsen syndrome
Romano Ward syndrom
Congenital QT syndrome
Pure cardiac phenotype (no deafness)
Jervell and Lange Nielsen syndrome
Congenital QT syndrome
Autosomal recessive
Sensorineural deafness
Brugada syndrome
Autosomal dominant
Asian males
ECG pattern of pseudo-right bundle branch block + ST elevations in V1-V3
Risk of ventricular tachyarrhytmias and SCD
Prevent with implantable Cardioverter defibrillator (ICD)
Most common type of ventricular pre excitation syndome
Wolff-parkinson White
Wolff parkinson white syndrome
- Abnormal fast accessory conduction pathway from atria to ventricle (Bundle of Kent)
- Bypasses the rate slowing AV node
- Ventricles depolarize earlier: delta wave with widened QRS complex and shortened PR interval on ECG
- May result in reentry circuit: SV tachycardia
Atrial fibrillation
Chaotic and erratic baseline with no descrete P waves in between IRREGULARLY spaced QRS complexes
Atrial fibrillation tratment
- Anticoagulation
- Rate control
- Rhythm control
- Cardioversion
Atrial flutter
A rapid succession of IDENTICAL, back to back atrial depolarization wave: sawtooth pattern
Definitive treatment of flutter
Catheter ablation
No discernible rhythm
Ventricular fibrillation
AV block: First degree
PR >200 mseg
Benign and asymptomatic, no treatment required
Progressive lengthing of PR interval until a beat is dropped: P wave not followed by QRS
AV block: Second degree: Mobitz type I: Wenckebach
Mobitz type II
Dropped beats are not preceded by a change in the length of the PR interval
May progress to 3rd degree block
Treat with pacemaker
Third degree (complete block)
Atria and ventricles beat independently of each other.
P waves and QRS complexes not rhytmically associated
Atrial rate >Ventricular rate
Can be caused by Lyme disease
Third degree (complete) block
Third degree block treatment
pacemaker
Mobitz type II treament
pacemaker
Atrial natriuretic peptide is released from, when, effects
- atrial myocites
- increase in blood volume and atrial pressure
- increase cGMP, vasodilation and less Na absorption at renal collecting tubule. Dilates afferent renal arterioles and constricts efferent arterioles, promoting diuresis
- Contributes to aldosterone escape
Brain natriuretic peptide is released from, when, effects
- ventricular monocytes
- response to high tension
- Similar action to ANP, longer half life
- Dx of HF: High NPV
- Nesiritide for treating HF
Cushing reflex
Triad:
- hypertension
- bradycardia
- respiratory depression
Central chemoreceptors respond to
pH and Pco2 of brain
Doesn’t respond to PO2
Peripheral chemoreceptors respond to
Low PO2 (<60 mmHg)
High PCO2
Low pH blood
Aortic arch chemo and baroreceptors transmit via
Vagus nerve to solitary nucleus of medulla
Carotid sinus baroreceptor transmits via
Glossopharyngeal nerve to solitary nucleus
Good aproximation of left atrial pressure
Pulmonary capillary wedge pressure
PCWP in mitral stenosis
PCWP> LVED pressure
PCWP is measured with
Pulmonary artery catheter: Swan Ganz catheter
Causes vasodilation in brain
CO2: lower pH
Determine fluid movement through capillary membranes
Starling forces:
- capillary pressure
- intersticial fluid presure
- plasma oncotic presure
- intersticial oncotic pressure