Cardiac Phys/Patho Flashcards
What causes the first (S1) and second (S2) heart sounds?
The first heart sound is caused by closure of the mitral and tricuspid valves at the beginning of systole. The second heart sound is caused by closure of the aortic and pulmonic valves (semilunar) at the beginning of diastole.
An S3 heart sound is an indicator of what condition?
Gallop rhythm during mid-diastole is most often heard in systolic heart failure in adults.
What is the postulated mechanism that produces the S3 heart sound?
Oscillation of blood back and forth between the walls of the ventricles initiated by inrushing of blood from the atria
Describe the murmur heard and stethoscope location in mitral stenosis
Opening snap heart in diastole, rumbling diastolic murmur. Best heard over cardiac apex
Describe the murmur heard and stethoscope location in mitral regurgitation
Holosystolic murmur heard throughout systole. Best heard over cardiac apex
Describe the murmur heard and stethoscope location in atrial stenosis
Systolic murmur best heard in the second right intercostal space (over the aortic arch)
Describe the murmur heard and stethoscope location in aortic regurgitation
Diastolic murmur best heard along the right sternal border
How is aortic regurgitation graded?
Assessed qualitatively: less than 20% of SV is mild, 20-39% is moderate, 40-60% is moderately sever, greater than 60% is severe
What portion of ventricular filling is atrial contraction responsible for?
Atrial kick accounts for 20-25% of ventricular filling, passive ventricular filling is responsible for the initial 75%
What is the normal range of stroke volume in the 70 kg adult
Normal range is 60-90 mL
What is the EF and normal range?
EF = end-diastolic volume - end systolic volume. Normal range is 60-80%
What are the two determinants of cardiac output
Stroke volume x heart rate
What is the cardiac index?
CO/BSA. Normal range is 2.5-4 L/min/m^2
When the ventricle fills more during diastole, more blood is ejected during systole, what law is this?
Frank-Starling’s law. Ventricular filling during diastole is directly related to the amount of blood ejected during systole.
Describe the process that describes ventricular myocyte relaxation (lusitropy).
Myocyte contraction requires increased intracellular Ca2+, therefore relaxation requires Ca2+ levels to return to resting levels which is accomplished by the SERCA2 pump located in the sarcoplasmic reticulum (an energy dependent process)
List the organs in the vessel rich group and the amount of CO they receive
Brain (15%), lungs (100%), heart (4-5%), liver (25%), kidney (20%), digestive tract, and endocrine tissues
What percent of the LV’s CO traverses the bronchial circulation? Vessels arise from what arteris?
1-2%, bronchial circulation arises form thoracic aorta and the intercostal arteries
What is the range of the normal pressures in each chamber of the heart?
RA 1-8
RV 15-30/0-8
LA 2-12
LV 100-140/0-12
What is the normal value for mPAP
mPAP = 16, 25/8
What is the normal range for PAOP
5-15
What causes a change in blood pressure when changing the patient’s position?
Altered preload (venous return) is most responsible for a change in blood pressure when the patient is re-position
What are two determinants of arterial blood pressure?
SVR and CO - application of Ohm’s law
What most determines SVR?
Vascular tone, especially that of the arterioles
What is the normal range for SVR?
1200-1500 dynes.sec.cm^-5
How do you calculate SVR?
(MAP-CVP)/CO x 80
In what segment of systemic circulation is resistance greatest? The greatest decrease in blood pressure in the arterial tree occurs where/
Resistance to blood flow is greatest in the arterioles, accounting for about half the resistance in the entire systemic circulation, this is where the greatest decrease in blood pressure occurs
What maintains systemic arterial blood pressure?
Elastic recoil of arterial blood vessels during diastole keeps systemic arterial blood pressure from falling
What are the two determinants of pulse pressure/
Ratio of stroke volume to arterial compliance. Pulse pressure increases when either CO increases or arterial compliance decreases
Where are the arterial baroreceptors located? What do they respond to?
Located in the aortic arch and carotid sinus, respond to stretching caused by MAP greater than 90
When baroreceptors are stimulated what happens?
Baroreceptor firing reflexly inhibits the SNS outflow decreasing myocardial contractility, decreased HR, decreased venous tone, and decrease in SVR and blood pressure
Where are venous baroreceptors located?
Venous baroreceptors are located in the right atrium and great veins. Produce an increase in HR when they are stretched (Bainbridge reflex) to prevent back-up of blood in the veins, right heart, and pulmonary circulation.
What happens to the HR during inspiration and expiration in a spontaneously breathing individual?
HR increases with inspiration and decreases with expiration. During inspiration negative intrathroacic pressure increases venous return causing activation of the Bainbridge reflex increasing HR, the opposite occurs during expiration
What nerves carry the afferent and efferent signals of the Bainbridge reflex?
Baroreceptors send afferent signals to the medulla via the vagus nerve, the medulla transmits efferent signals via the sympathetic nerves to increase HR by as much as 75%
What happens to arterial BP during inspiration and expiration in the spontaneously breathing patient?
BP normally decreases during inspiration because pulmonary venous capacitance increases thereby decreasing venous return to the left ventricle. Although HR typically increases d/t Bainbridge, SV, CO, and arterial BP all decrease
How does the dorsalis pedis arterial waveform differ from the waveform found in the aorta in the supine or prone patient?
Pulse pressure undergoes natural amplification during transit through the arterial tree. Compared with the aorta, systolic pressure is greater and diastolic pressure is less in the dorsalis pedis artery. Pulse pressure increases the further away from the heart you go
Which is a more potent vasoconstrictor, Angiotensin II or Vasopressin?
Vasopressin
The arterial system contains what percent of total blood volume? Capillaries? Venous?
Arteries 13
Capillaries 7
Venous 64
What physics law applies to the movement of O2 and nutrients across the capillary membrane?
Fick’s law of diffusion
Changes in any of what 4 factors may promote peripheral edema?
- decreased plasma colloid osmotic pressure 2. increased capillary hydrostatic pressure (usually d/t increased central venous pressure) 3. increased interstitial protein (lymph obstruction) 4. increased capillary wall permeability
What is the osmotic pressure of albumin? How much does albumin contribute to the total colloid osmotic pressure of plasma?
Albumin is 22 mmHG, and is responsible for 80% of the total colloid osmotic pressure
What percentage of CO is delivered to the VRG?
~75% of resting CO is delivered to the VRG which comprises 10% of total body mass
What determines blood flow through an organ or tissue?
Pressure gradient and resistance. Blood flow is directly related to the pressure gradient and indirectly related to the resistance
In general, blood flow to a tissue is most directly related to what?
Generally related to tissue metabolism, metabolites dilate the vasculature and increase blood flow
What are the two most important determinants of O2 delivery to the tissues?
CO and O2 content of arterial blood. O2 content is determined by Hgb concentration and SpO2
Describe the effects of hypercapnia on the cerebral vasculature and systemic vasculature.
Hypercapnia causes dilation of both cerebral and systemic vasculature. Increase in arterial CO2 perfusing the brain causes vessel relaxation and an increase in BF.
How does hypercarbia affect pulmonary vascular resistance?
Pulmonary vascular resistance increases in response to hypercarbia, the response is opposite that of cerebral and systemic vasculature
With hypercarbia, is there HTN or hypotension?
Both HTN and hypotension occur with hypercarbia. Hypercapnia may cause increased myocardial O2 demand (tachy, early hypotension) and decreased myocardial O2 supply (tachy, late hypotension)
How does severe acidosis alter PVR and SVR?
Acidosis increases PVR and decreases SVR
When during the cardiac cycle is BF through the cardiac arteries the greatest?
Greatest during diastole. The left ventricle is only perfused during diastole, but all other chambers are perfused throughout the cardiac cycle.
What is the resting coronary blood flow in ml/min, % of CO?
225-250 mL/min, 4-5%
What is the O2 extraction of coronary arterial blood?
70%
What is the normal range of coronary perfusion pressure?
Coronary autoregulation takes place between 60-160 mmHg, therefore 60-160 mmHg is assumed to be the the normal range of CorPP
How is CorPP calculated?
AoDP - LVEDP (usually PAOP/PCWP is used as a surrogate)
Most important determinant of coronary blood flow?
Myocardial metabolism, especially the presence of adensosine
What 4 factors determine myocardial O2 demand?
- HR 2. diastolic wall tension (preload) 3. systolic wall tension (afterload) 4. contractility (determined by chemical environment, especially Ca2+)
Arrange afterload, preload, and HR in order of biggest influence on myocardial O2 consumption
HR>afterload>preload
What 5 factors determine myocardial O2 supply?
- AoDP 2. LVEDP 3. HR (tachycardia limits diastolic time) 4. arterial O2 content 5. O2 extraction
Describe the distribution of Alpha-1 and Beta-2 receptors in the myocardium
Alpha-1 receptors primarily located in epicardial blood vessels. Beta-2 primarily located in intramuscular and subendocardium.
What layer of the left ventricle is most vulnerable to ischemia?
Subendocardium because it has the highest metabolic demand and undergoes the most compression force during systole compared to the subepicardium
Describe myocardial preconditioning
Short0term rapid adaptation to brief ischemia such that during a subsequent, more sever ischemic insult myocardial necrosis is delayed. Can be triggered by volatile agents
State the rank and conduction velocities of cardiac tissues
Purkinje fibers>ventricular myocytes=arterial myocytes=bundle of His>SA and AV nodes. Dromotropy describes the cardiac conduction velocity
What are the intrinsic firing rates of the SA, AV, and Purkinje fibers?
SA 60-100
AV 40-60
Purkinje 15-40
Compare the SNS and PNS innervation of the heart
SNS innervates both atria and ventricles, and the conduction system. PNS innervates the SA and AV nodes, and the atrial
Where does PNS innervation of the heart arise?
Dorsal motor nucleus of the vagus nerve in the medulla of the brain. Right vagus innervates the SA node, and left vagus innervates the AV node.
What cardiac electrical event is represented by the QT segment?
Plateau phase, duration of QT is determined by the duration of the plateau - ventricular contraction is occurring during this time
What cardiac electrical event is represented by the PR interval?
The AP passing through the AV node
What ion control the RMP and which ion controls the threshold potential?
K controls RMP, Ca2+ controls threshold
Effect of acute hypokalemia on RMP?
Decreases the RMP, hyperpolarization, decreases excitability
Effect of hyperkalemia on RMP?
Increases the RMP, depolarization, increases excitability
Effect of hypocalcemia on threshold?
Decreases threshold, increases excitability
Effect of hypercalcemia on threshold?
Increases threshold, decreases excitability
Administration of what other ion increases membrane stability? (decreased excitability?)
Magnesium
What are the characteristics of sick sinus syndrome?
Bradycardia, punctuated by episodes of supraventricular tachycardia most often observed in the elderly
What is the most common cardiac pre-excitation syndrome and its incidence?
Wolff-Parkinson-White is the most common pre-excitation syndrome, incidence of approx. 0.3% in the general population
Why is afib particularily dangerous in the patient with WPW?
Refractory period of an accessory pathway determines the ventricular rate, which may exceed 300 BPM in the patient with WPW. Syncope or congestive HF may result from the rapid ventricular rate.
What promotes concentric hypertrophy? Left and Right?
Concentric hypertrophy develops in response to chronically elevated afterload. Left - systemic HTN, aortic stenosis. Right - pulmonary HTN, pulmonic valve stenosis
What happens to the ventricular wall and chamber size with concentric hypertrophy?
The ventricular wall and septum thicken which permits the ventricle to develop more tension and eject blood more effectively against a higher afterload. Chamber size remains unchanged.
Does concentric hypertrophy decrease wall tension?
Yes, according to Laplace. Tension = pressureradius/2wall thickness
What promotes eccentric hypertrophy? What happens to the size of the left ventricular chamber?
Volume overload (chronically increased preload) stimulates the ventricular wall to dilate, the chamber enlarges to accommodate a larger volume of blood. Excessive intravascular volume, aortic regurgitation, and mitral regurgitation can cause it
What are the hemodynamic goals for aortic stenosis?
- Low HR, 50-70, to reduce myocardial O2 consumption 2. Maintain SR. 3. Maintain or increase preload 4. Maintain or increase afterload 5. Maintain contractility (slow, regular, full, tight, and not too strong)
What are the hemodynamic goals for mitral stenosis?
- Low HR, allows for complete ventricular filing 2. Maintain SR 3. Maintain preload 4. Maintain afterload 5. Maintain contractility (Slow, regular, not too full, not too tight, not too strong)
What are the hemodynamic goals for the patient with aortic regurgitation?
- Increase HR 2. Maintain SR 3. Increase preload 4. Decrease afterload 5. maintain contractility (Fast, regular, full, forward, and not too strong)
What are the hemodynamic goals for mitral regurgitation?
- Increase HR 2. maintain SR 3. maintain or increase preload 4. decrease afterload 5. maintain contractility 6. avoid increased pulmonary vascular resistance
Hemodynamic goals for obstructive hypertorphic cardiomyopathy?
- Normal range HR 2. maintain SR 3. increase preload 4. increase afterload 5. decrease contractility
What four conditions increase the LVOT (left ventricular outflow tract) obstruction?
- Increased HR
- Decreased preload
- Decreased afterload
- increased contractility
What is the first treatment for a patient with obstructive hypertrophic cardiomyopathy?
- Volume is the first line treatment 2. Then phenylephrine is the second line after adequate volume administration
What is the primary goal of anesthesia in a patient with CAD?
Maintain cardiovascular stability avoiding hypo- hypertension, and tachycardia
Of hypotension, hypertension, and tachycardia which is the most detrimental to a patient with CAD?
Tachycardia - increases myocardial metabolism and therefore O2 demand
What are the first signs of cardiac tamponade?
Decrease in arterial blood pressure with reflex tachycardia
