Cardio Exam 1 Flashcards
Talk through Wigger’s diagram
Do it
What does CVP (central venous pressure) measure?
Ability of heart to pump blood out of RA - determined by tricuspid valve function, RV function, pulmonary arterial function etc.
Common causes of increased CVP
- Heart failure 2. Tricuspid valve disorders 3. Pulmonary arterial HTN
Cause of decreased CVP
Low blood volume
Discuss JVP wafeforms
A: Atrial systole X: fall in RA pressure after a wave peak C: ventricular contraction, tricuspid valve Closure X’: descent of cardia base after atrial relaXation V: venous filling of RA Y: rapid ventricular filling - right atrium is emptYing H: continued filling of right atrium during diastole that is inte4r
Which jugular vein is more directly related to changes in RA pressure/heart?
RIJ REJ is more superficial
What does high A wave from jugular pressure waveform indicate?
- Stenosis of tricuspid - Closure of tricuspid valve - Right ventricular failure
What does distension of jugular vein indicate?
severe congestion
What does S1 reflect?
mitral and tricuspid closure
What does S2 reflect?
aortic and pulmonic valve closure
Between S1 and S2 heart sounds, which sound varies with respiration?
S2
What cardiac event occurs between S1 and S2? Between S2 and the next S1?
Systole between S1 and S2 Diastole between S2 and the next S1
Describe physiologic splitting of S2
With inspiration, there is increase venous return to RV = increased RV EDV = increased time to expel blood from RV = pulmonic valve stays open longer
Common causes of widened S2 splitting? Not the physiologic splitting.
- RBBB (delay in RV contraction = delay in closure) - Pulmonic stenosis (more time to open, delay in closing) - Also COPD: increased back pressure into RV
Most common cause of fixed splitting of S2?
ASD Pulmonary side of heart has low resistance, so volume overload in right heart results in delayed closure of pulmonic valve. These individuals don’t have physiologic splitting with respiration. It is just fixed.
Common causes of paradoxical splitting?
This just means that pulmonic closes before aortic and this occurs during expiration, not inspiration. LBBB (delay in LV contraction = delay in aortic valve closure) Aortic stenosis (more time open, delay in closure)
What sound is heard during mitral stenosis? When does sound occur?
Opening snap Why? Calcification and stiffening valve. Note: sound is fixed and occurs at the start of diastole (before S1). No change with respiration.
Is S3 pathologic? Why and when does it occur?
Produced by tension of chordae tendinae during rapid filling of diastole. Can be seen in young with thin chest wall and supple ventricle - also in athletes. No pathology here. Can be seen in pathology - volume overload or advanced regurg.
What is 4th heart sound? Why and when does it occur?
Occurs in late diastole and coincides with atrial contraction. It is a pre-systolic sound produced when trying to fill a stiff ventricle. Heard in cases of low ventricular compliance, hypertrophy and acute MI.
Murmurs heard in aortic area
Ejection type murmurs such as: Aortic stenosis Flow murmur?
Murmurs heard in pulmonic area
Ejection type murmurs such as: Pulmonic stenosis Flow murmur?
Murmurs heard in tricuspid area
Pansystolic murmurs such as: Tricuspid regurg VSD Also mid-to-late diastolic murmurs such as Tricuspid stenosis ASD
Murmurs heard in mitral area
Pansystolic murmurs such as Mitral regurg Also mid-to-late diastolic murmurs such as Mitral stenosis
Types of systolic murmurs
- Ejection type: aortic stenosis, pulmonic stenosis. Sound here = crescendo, decrescendo 2. Pansystolic (holosystolic): mitral regurg, tricuspid regurg, VSD Sound here = non-crescendo/decrescendo sound 3. Late systolic: MVP Sound here = mid-systolic click with non-crescendo/decrescendo sound
Murmurs heard at left-sternal border (Erb’s point)
Early diastolic murmurs: Aortic regurg Pulmonic regurg
CO calculation. What is normal value in resting adult?
CO = SV.HR Normal ~5L/min in resting adult
Define cardiac index
Volume of blood ejected from heart per unit time per unit of body surface area eg. 3L/min/m^2 This is more realistic parameter of cardiac function as it takes into account the size of the human
How much of the SV is attributed to rapid filling phase? How about atrial kick/contraction?
~ 80% by rapid filling - passive ~ 20% by atrial contraction
Define preload Define afterload
Preload: Tension exerted on the cardiac ventricular muscle when it begins to contract Afterload: pressure that ventricle has to win to produce a stroke volume
What happens to SV as preload increases if all other factors are equal? How can this principle be used in patient with heart failure? What must you be careful of?
SV increase within certain limits. Pt with heart failure can have decreased CO. If you want to increase it, you can IV bolus them especially if dehydrated. As you do, BP should go up. Too much can cause patient to go into pulmonary edema.
Describe Frank-Starling relationship and mechanism
Relationship: force of ventricular contraction is function of ventricular end diastolic length. If you increase pre-load, contractility and ultimately SV increases. Mechanism: length of sarcomere determines sensitivity to Ca. There is optimum. Within limits.
What happens to SV with increasing afterload if all else is equal?
Increase afterload results in decrease in SV.
What is the ANREP relationship and mechanism? Why do I care?
Relationship: increase in aortic pressure abruptly = positive inotropic (FOC) effect. Mechanism: increase LV wall tension = increase cytosolic Na level, increase myocardial cytosolic Ca level = increase myocardial contraction. Why do I care? If I want to hear a particularly soft murmur, I can apply a torniquet or have someone make fist to increase work of heart and therefore sound of murmur.
What happens to SV when ventricular contractility goes up with all other factors being equal?
Increased contractility = increased SV
Review SV vs preload, afterload, contractility graphs
do it
Review contractile status, ventricular performance graph
do it
What is Bowditch effect/phenomenon?
Increased HR progressively enhances FOC. If too rapid, force decreases. CO is rate-dependent. Makes sense if you remember CO = SV.HR
Clinical method of measuring CO
Pulmonary artery catheterization (PAC): thermodilution with bolus injection of cold fluid.
The cardiac AP contour looks the same as skeletal muscle AP contour?
Falsch
Describe the cardiac myocyte AP curve. Include the phases, ions/channels responsible for the changes
Depolarization = phase 0 - Opening of fast Na = rapid depolarizing Early repolarization = phase 1 - Na channels close, some K channels open, incomplete repolarization Plateau = phase 2 - Membrane potential ~ 0 mV (ECG!!). Slow Ca channels open = Ca in, balanced by opening of K channels allowing K out Rapid repolarization = phase 3 - Ca channels close, opening or more K channels = K out RMP = phase 4 - Only K channels and maintenance Na/K ATPases open allowing for maintenance of RMP until next stimulus
Describe cardiac nodal tissue AP
* note: only phases 0, 3 and 4; no 1, 2 Phase 0: Threshold met = opening of Ca channels slowly Phase 3: After depolarization occurs, K channels open, K out Phase 4: HCN/funny current channels slowly depolarizes cell - progressive reduction in K efflux and progressive increase in calcium influx
What is the difference between channels responsible for depolarization in cardiac myocytes and cardiac nodal tissue?
Cardiac myocytes: Fast Na channels Cardiac nodal tissue: Ca channels
Describe sequence of depolarization in heart. Note the order of depolarization within the ventricles.
SA node Atria AV node Bundle of His Bundle branches Purkinje fibers Ventricles: Septum, apex and ventricular free walls
Approximate rates of conducting tissue in heart
SA node: 60-100 AV: 40-55 Bundle of His, Bundle branches, Purkinje: 25-40 Note: atrial and ventricular myocardium don’t have pacemaker rates
Which lead on ECG shows greatest net depolarization of heart?
Lead II - greatest deflection 60 degrees
The refractory period of the AP in cardiac myocytes is related to which of the following ion channels: a. Sodium channels b. calcium channels c. potassium channels d. chloride channels
- Answer = A. Fast Na channels
What are the two refractory periods seen in cardio myocyte AP cycle? What is happening to cause these periods? Can additional stimulus elicit AP during each of these periods?
Absolute refractory period Relative refractory period These are a result of the gating kinetics of the fast Na channel found in cardiac myocytes that exist in 3 states: a. Resting: no Na entering cell as inner pore is closed, intracellular gate is open. b. Activated: stimulus lead to VG change and opening of VG sensitive inner pore. Na enters cell. c. Inactivated: intracellular gate closes and Na ceases to enter cell even though inner pore is open. ARP: cannot illicit another AP regardless of strength of stimulus as intracellular gate is closed, despite inner pore being open RRP: can illicit another AP is strength of stimulus is sufficient
Why is there a time delay between electrical events in cardiac myocytes and mechanical response in the tissue?
Takes some time for Ca channels to open. This causes the delay
Describe events of cardiac myocyte contraction and relaxation
Contraction: - Calcium entry through VOCC - Calcium release from SR (through ryanodine receptor) - Calcium interacts w/trop = contractile shortening Relaxation: - Calcium dissociates from trop - Ca taken back up into SR via SERCA (atpase) - Ca becomes bound to proteins within SR (calcisequestrin) - CA pumped out of cell at cell membrane via NCX (Na/Ca exchanger atpases)
Types of arrhythmogeneses
- Active a. Automaticity b. Triggered activity: Early afterdepolarizations, After depolarizations d. Re-entrant circuits 2. Passive a. Cardiac remodeling
Describe arrhythmias from automaticity
These are arrhythmias from cells with phase 4 depolarization. SA node can lead to sinus tachy (via SNS increases automaticity) and sinus brady (via PSNS decreasing automaticity). These are obviously physiologic arrhythmias. Subsidiary or latent pacemakers can be found in atria, AV junction, ventricles. This is abnormal.
Diastolic depolarization underlies a major difference in channel expression between nodal and non-nodal cells. What ion channels are not present in non-nodal tissue? a. Calcium ATP-ases b. Na-K ATPases c. Na-Ca exchanger d. Hyperpolarization-activated cyclic nucleotide-gated channels e. Beta-adrenergic receptors
Answer = D. HCN/funny current channel active during phase 4 depolarizations seen in cardiac nodal tissue.
Effect of Ach on phase 4
Increases K efflux = reducing slope of phase 4
Effect of NE on phase 4
Increase Ca and funny current = increase slope of phase 4
Effect of hypokalemic on phase 4
Decrease K current = increase in slope of phase 4
Effect if ischemia on phase 4
Decrease K current = increase in slope of phase 4
Effect of mild hyperkalemia on phase 4. Severe hyperkalemia?
Mild hyperkalemia = increase in max diastolic potential = increase in slope of phase 4 Severe hyperkalemia = significantly depolarized membrane potential, cells become inexcitable
Describe how triggered activity leads to development of arrhythmogenesis? What ions are responsible for DAD and EAD? Which is exacerbated by low HR? Which by high HR?
This refers to eliciting AP changes in cells without phase 4 depolarization, ie. myocytes. DAD: cytosol and / or SR becomes Ca overloaded resulting in change in membrane potential leading to AP. Exacerbated by high HR. Why? Interrupts ability to recycle Ca. EAD: any alterations in any ion flux during plateau phase (2) or phase 3 leading to prolonged AP duration and generation of AP. Specifically: reduced K current, increased Ca, increased Na/Ca exchange activity, increased late Na current. Exacerbated by low HR. Why? APs tend to be long at low HRs.
Types of re-entrant circuits. Which are harder to tx? Which have worse prognosis?
Anatomically: WPW syndrome, AVNRT, atrial flutter, PSVT. Tx with ablation. More easier to tx, better prognosis. Functionally: absence of defined pathway. Harder to tx. Worse prognosis.
Describe how cardiac remodeling leads to arrhythmogenesis
Changes in gap junctions Changes in cell structure: fibrosis, fat, nerve endings, cell hypertrophy Strength of impulse now acts on smaller amount of tissue = length of AP increased now.
Effect of PSNS on blood vessels, heart and coronary arteries
BV: no innervation by PSNS Heart: decrease HR and contractility Coronary arteries: constrict Cranial: 10, 9, 7, 3 Sacral: S2-4
Effect of SNS on blood vessels, heart and coronary arteries
BV: constriction (except skeletal) Heart: increase HR and contractility Coronary arteries: dilate Ganglia: T1-L2 Cervical ganglia Lumbar splanchnic
Result of flattened diaphragm on CO
Decreased CO