CCP 216 Cardiovascular Emergencies ❤️ Flashcards
preload equation (Laplace’s law)
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Preload = (Ventricular pressure x Ventricular chamber radius) / 2x ventricular wall thickness (i.e. P⋅R/2h)
afterload definition
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- “load” that the heart must eject blood against
- a result of stress (or “tension”) that the cardiac wall (LV) experiences during systolic ejection
- the amount of pressure that the heart needs to exert to eject the blood out if it during the contraction
preload definition
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- Myocardial sarcomere length just prior to contraction, for which the best approximation is end-diastolic volume
- Tension on the myocardial sarcomeres just prior to contraction, for which the best approximation is end-diastolic pressure
cardiac preload is about the length-tension relationship. this is the core principle of the frank-starling mechanism
factors leading to increased cardiac afterload
- Afterload is increased when aortic pressure and systemic vascular resistance are increased.
- aortic valve stenosis and ventricular dilation will both increase afterload
cardiac afterload equation
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- [(LV Pressure x LV Radius) / LV wall thickness] or [(P x r)/h]
- LV Wall Tension = [(SVR - Pleural Pressure) x LV Radius] / LV wall thickness
Afterload reduction can be achieved through:
- Decreasing SVR (arterial dilation)
- Increasing pleural pressure (PPV/PEEP)
hydralazine MOA
direct acting arterial vasodilator
- stimulates the formation of nitric oxide by the vascular endothelium
- inhibits release of calcium from the smooth muscle sarcoplasmic reticulum
- causes smooth muscle hyper-polarization through the opening of K+ channels
mechanisms to reduce cardiac afterload
- Decreasing SVR (arterial dilation)
2. Increasing pleural pressure (PPV/PEEP)
primary determinants of cardiac preload
- Pressure filling the ventricle
2. Compliance of the ventricle
primary determinants of “pressure filling the ventricle” (cardiac preload)
- Intrathoracic pressure (pleural pressure aka esophageal pressure)
- Left atrial pressure
- Right atrial pressure
- Mean systemic filling pressure
- Cardiac output
primary determinants of “Compliance of the ventricle” (cardiac preload)
- Pericardial compliance
2. Ventricular wall compliance
primary determinants of “myocardial wall stress” (cardiac afterload)
- [(LV Pressure x LV Radius) / LV wall thickness] or [(P x r)/h]
- LV Wall Tension = [(SVR - Pleural Pressure) x LV Radius] / LV wall thickness
P: ventricular transmural pressure (difference between intrathoracic pressure and ventricular pressure)
r: radius of the ventricle (Increased LV diameter increases wall stress at any LV pressure)
h: thickness of ventricular wall (thicker wall decreases wall stress by distributing it among larger number of sarcomeres)
primary determinants of “input impedance” (cardiac afterload)
- Arterial compliance (Aortic compliance, Peripheral compliance)
- Inertia of the blood column
- Ventricular outflow tract resistance (HOCM, AS)
- Arterial resistance (Length of arterial tree, Blood viscosity, Vessel radius)
input impedance definition (cardiac afterload)
describes ventricular cavity pressure during systole
contractility definition
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“Contractility describes the factors other than heart rate, preload, and afterload that are responsible for changes in myocardial performance.”
- change in peak isometric force (isovolumic pressure) at a given initial fibre length (end diastolic volume)
- length-independent activation
Type 1 MI
- caused by acute atherothrombotic CAD
- usually precipitated by atherosclerotic plaque disruption (rupture or erosion)
“Vaso-occlusive”
Type 2 MI
MI caused by oxygen supply/demand mismatch
“Demand”
Type 3 MI
Patients with a typical presentation of myocardial ischemia/infarction with unexpected death before blood samples for biomarkers could be drawn
“Sudden cardiac death”
Type 4 MI
MI as a complication of PCI
Type 5 MI
MI as a complication of CABG
typical value for right atrial pressure (RAP) in an adult
RA 5 mmHg
“nickel”
typical value for right ventricular pressure (RVP) in an adult
RV 25/5 mmHg (systolic/diastolic)
“quarter”
typical value for left atrial pressure (LAP) in an adult
LA 10 mmHg
“dime”
typical value for left ventricular pressure (LVP) in an adult
LV 100/10 mmHg (systolic/diastolic)
“dollar”
tachyphylaxis definition
- very rapid development of tolerance or immunity to the effects of a drug
- sudden decrease in response to a drug after its administration
Virchow’s triangle (venous thrombosis)
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- Hyper coagulability
- Stasis
- Endothelial injury
Five causes of hypoxemia
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- Low partial pressure of inspired oxygen
- VQ mismatch
- Diffusion impairment
- Hypoventilation
- Shunt (venous admixture)
differentials for sinus bradycardia
“EPI-ID” (a reichertism)
- Electrolytes
- Parasympathetic response
- Infarction
- ICP elevation
- Drugs/Pharmacologic
Stanford type “A” aortic dissection
- Affects ascending aorta
- Accounts for 60% of aortic dissections
- Initially managed surgically
Stanford type “B” aortic dissection
- Affects descending aorta
- “B begins beyond brachiocephalic vessels”
- Accounts for 40% of aortic dissections
- Initially managed medically
primary risk factors for aortic dissection
- advancing age
- male sex
- systemic hypertension
- preexisting aortic aneurysm
- atherosclerosis
- connective tissue disorders
- sympathomimetic drug abuse
cardiac steal syndrome
- The heart’s vessels naturally auto regulate to facilitate even flow to all areas
- In the presence of a coronary lesion, the vessel will dilate to accommodate improved flow distal to the plaque
- If you have two vessels branching off a main vessel, and one branch vessel contains a plaque, the flow to each vessel will still be 50/50 via auto regulation
- If the person becomes vasodilated, the vessel containing the plaque is already maximally dilated d/t auto regulation. Now, the second branch vessel will dilate, causing what was previously 50/50 flow distribution to shift to a disproportional distribution, such as 80/20, which means the tissue distal to the site of the plaque will get reduced flow.
- The good vessel is “stealing” flow from the occluded vessel d/t vasodilation beyond what the shitty vessel is capable of
primary determinants of cardiac contractility
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- Preload
- Afterload (the Anrep effect)
- Heart rate (the Bowditch effect)
- Myocyte intracellular calcium concentration
- Temperature
Biochemical and cellular factors which affect cardiac contractility
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- Catecholamines and the autonomic nervous system (Calcium concentration)
- ATP availability (eg. ischaemia)
- Extracellular calcium (Calcium concentration)
- Temperature
this shit is super important and you gotta know how it impacts the heart in a range of disease. everything from your bread and butter HFrEF all the way to your septic-induced cardiomyopathy and your post-cardiac-arrest myocardial stunning
Key clinical findings for diagnosing cardiac tamponade
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- Beck’s Triad (JVD, muffled heart sounds, hypotension)
- Compressed RA (ultrasound)
- Non-collapsible IVC (ultrasound)
- pulsus paradoxus (arterial waveform)
remember kids, tamponade is a clinical diagnosis. just because the guy has a big old pericardial effusion on ultrasound it does NOT mean he is in tamponade.
tamponade is a clinical SYNDROME characterized by shock which can be interpreted through your clinical exam as seen in the above points
define pulsus paradoxus
- During normal spontaneous breathing, negative pleural pressure against the heart during inspiration produces a slight increase in transmural pressure and cardiac afterload
- During normal spontaneous breathing, inspiration causes blood to fill the RA from the vena cava, and causes increased RV filling with a slight bulge of ventricular septum into the LV
- This causes a small decrease in LV ejection with systole (increased afterload, decreased LVEDV). In normal breathing, SBP can normally fall on inspiration by 10 mmHg
- Pulsus paradoxus is an exaggeration of this normal blood pressure variation with breathing. It is defined as a fall in systolic pressure by more than 15 mmHg during spontaneous inspiration
- In a mechanically ventilated patient, a reversal of this pressure variation occurs. PPV displaces the LV wall inward during systole to assist in LV emptying. This causes a slight rise in the systolic pressure during mechanical inspiration.
- Reversed Pulsus Paradoxus (PPV) is defined as an exaggeration of the rise in systolic BP during mechanical inspiration. A rise in peak systolic pressure on mechanical inspiration by more than 15 mmHg is considered significant.
you can measure this with Korotkoff sounds but really the best/easiest way to see it is in A-line Δ pulse pressure variation
delta (Δ) pulse pressure variation definition
the difference between the maximal and minimal pulse pressure during one breathing cycle, divided by their mean
you can measure this with korotkoff sounds but really the easiest way is to watch the ΔPP variation on A line. there will be a drop in BP during negative pressure spontaneous breathing, and a rise in BP during positive pressure MV
systolic blood pressure definition
the maximum pressure experienced in the aorta when the heart contracts and ejects blood into the aorta from the left ventricle
this can be seen on the cardiac cycle PV loop at the point where the AV closes
diastolic blood pressure definition
the minimum pressure experienced in the aorta when the heart is relaxing before ejecting blood into the aorta from the left ventricle
this can be seen on the cardiac PV loop as the point where the AV opens at the end of systolic iso-volumetric contraction
this is because the valve is just opening but the aorta hasn’t actually “seen” any of the pressure yet, so it is actually at the lowest pressure state it will be in in the pressure-volume cycle
mechanism behind naturally occurring hypertension as people age
this slide is legit don’t just write it off cause you think old people are boring
- With aging, there is a decrease in the compliance of the large elastic arteries.
- This change is due to structural molecular changes in the arterial wall, including decreased elastin content, increased collagen I deposition, and calcification, which increases the stiffness of the wall
- This process is often described as “hardening of the arteries.”
- As the LV contracts against stiffer, less compliant arteries, SBP and DBP increase
- In response, the LV tends to hypertrophy
this is legit to know cause it factors into our cardiac afterload equation nicely. factors that increase cardiac afterload include intra cardiac factors or extra cardiac factors. extra cardiac factors are things the impede LV outflow of blood. part of this is the “compliance” of the arterial system. meaning, as people age and get shitty calcified vessels they will have significantly elevated cardiac afterload d/t worsening arterial compliance
Differentials for a narrowed pulse pressure in shock
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- heart failure (decreased pumping)
- hypovolemia (decreased blood volume)
- aortic stenosis (reduced stroke volume)
- cardiac tamponade (decreased filling time)
Normal amount of pericardial fluid
10–50 mL
TnK vs alteplase in the fibrinolysis of AMI
TnK is associated with a lower rate of non-cerebral bleeding complications (ASSENT-2 trial)
summarize the benefits of beta blockers in AMI
1) Decreased MvO2
2) Decreased risk of VF/dysrhythmias
3) Decreased automaticity
4) Prolonged diastole & increased coronary perfusion
5) Reduction in cardiac remodelling
6) Slows progression of atherosclerosis
7) Inhibits platelet aggregation and thromboxane synthesis
8) Reduction in reperfusion injury
At what phase in the cardiac cycle does the majority of ventricular filling occur?
- early diastole
2. a large initial pressure gradient leads to rapid ventricular filling
How can a paralytic drug affect hemodynamics?
Loss of skeletal muscle tone leads to a relative vasodilation, reducing venous return to RA
A 0.6mg/hr (600mcg per hr) transdermal NTG patch has the equi-pharmaceutical potency of what IV NTG infusion rate?
10mcg/min
Describe the approach to staged dosing for labetalol
Labetalol is designed to be given in bolus-dose pushes q10min
- 5mg (wait 10)
- 10mg (wait 10)
- 20mg (wait 10)
- 40mg (wait 10)
- 80mg (wait 10)
Stop at total of 300mg and consider another vasodilator like hydralazine, phentalomine, nitroprusside or nifedipine
cardiac index definition
- a measure of cardiac function that can be normalized for the patient’s body habitus
- a haemodynamic parameter that relates the cardiac output (CO) from left ventricle in one minute to body surface area (BSA)
- Calculated as CI (L/min/m2) = CO (L/min) / TBSA (m2)
Clinical findings associated with pericarditis
- Positional “pleuritic” chest pain (improved with sitting up and leaning forward)
- Pericardial “Friction rub” on auscultation of left lower sternal border
- Diffuse, concave ST-E on ECG with P-R depression
- low-grade fever
What patient cohort requires “emergent rescue PCI” in the setting of STEMI (post thrombolysis)
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1) Persistent ST-E that hasn’t decreased by at least 50% following thrombolysis
2) Persistent ischemic C/P post thrombolysis
What is the target time-frame for achieving rescue PCI in the setting of STEMI failed thrombolysis
- Ideal time frame is within 2 hours
2. Necessary within 24 hours
What is the preferred P2Y-12 inhibitor agent for patients who will be receiving primary PCI?
- Ticagrelor (Brilinta) 180mg is the preferred P2Y-12 inhibitor agent for patients who will be receiving primary PCI
- If using clopidogrel (Plavix) for PCI, double the usual age-based dose that would be administered in the setting of fibrinolysis
What is the preferred P2Y12 inhibitor agent for patients who will be receiving primary fibrinolysis?
- Clopidogrel (Plavix) is the preferred P2Y12 inhibitor agent for patients who will be receiving primary fibrinolysis
- Age ≤75 Clopidogrel 300 mg
- > 75 Clopidogrel 75 mg
P2Y12 inhibitors MOA (platelet activation)
- Inhibition of platelet aggregation impairs formation and progression of thrombotic processes
- A core part in the platelet activation process is the interaction of adenosine diphosphate (ADP) with the platelet P2Y12 receptor
- P2Y12 inhibitors provide irreversible blockade of the P2Y12 component of the ADP receptor on platelet surface
- Results in reduced platelet adhesion, activation and aggregation
aspirin MOA (platelet aggregation)
- Inhibition of platelet aggregation impairs formation and progression of thrombotic processes
- A core part in the platelet activation process is the activation of thromboxane A2 (an important lipid responsible for platelet aggregation)
- aspirin use irreversibly blocks the formation of thromboxane A2 in platelets, producing an inhibitory effect on platelet aggregation
Transfer to PCI-capable centre is preferable compared to primary fibrinolysis if PCI can be achieved within ___ minutes of first medical contact
120 minutes
The gold standard timeline for PCI in STEMI is within ___ minutes of first medical contact
90 minutes
indications for emergent PCI in NSTEMI
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- Hemodynamic instability
- Electrical instability
- Persistent C/P
Time-target for fibrinolysis (TnK) administration once a diagnosis of STEMI has been made, and the decision has been made to thrombolyze
30 minutes
Contraindications for PCI
1) Risk of bleeding during procedure.
2) Inability to take dual anti-platelet therapy (DAPT) for 1yr
3) Severe renal failure
4) Triple vessel disease (ie. needs CABG)
5) Palliative status
Anticoagulant of choice for an NSTEMI patient who is to be catheterized within 24 hours
unfractionated heparin (UFH)
Anticoagulant of choice for an NSTEMI patient who is to be catheterized in a timeframe beyond 24 hours
LMWH or Fondaparinux
- Single dose LMWH or fondaparinux provides 24 hours of coverage
Amiodarone dosing for ventricular irritability/acute tachyarrhythmias (bolus and infusion)
- Initial bolus: 150mg over 10 minutes
- First 6 hours: 1mg/min
- Next 18 hours: 0.5mg/min
- total dose over 24 hours should not exceed 2.4 grams
What is the percentage of cardiac output used up during heavy diaphragmatic breathing/tachypnea
- Up to 30% of CO can be used up during periods of tachypnea/heavy breathing
- This is why sometimes it is necessary to intubate a patient in shock, as a mechanism for reducing their total oxygen demand, reducing myocardial workload, improving systemic oxygen delivery
What patients with AMI are candidates for beta blocker therapy?
trick question sonn
- all patients with acute myocardial infarction (MI) should be treated with beta blocker therapy, unless there are gross contraindications
common clinical findings for aortic dissection
- Thorax Pain (95.5% of individuals with AD report pain, with 84.8% of all individuals with AD describing an abrupt onset of pain; 90.6% of the individuals studied reported their pain as “severe or worst ever.”)
- Abnormal CXR (Widening of the mediastinum 61.6% of cases, Widening of the aortic knob or abnormal contour 49.6% of cases
- New aortic murmur (Approximately 40% of patients with a dissection demonstrate an aortic insufficiency/regurgitant murmur, reflecting unseating of the aortic valve by an ascending AD)
- New onset peripheral pulse deficit (30% of patients with a Stanford Type A dissection and 15% with a Type B dissection demonstrate a pulse deficit.)
What patients with AMI are candidates for statin therapy?
trick question buddy
- Intensive statin therapy should be initiated as early as possible in ALL patients with STEMI
Characteristic ECG finding for HOCM
- large dagger-like “septal Q waves” in the lateral — and sometimes inferior — leads
- due to the abnormally hypertrophied interventricular septum
Clinical approach to “sympathetic crashing acute pulmonary edema”
1) Nitrates (hydralazine is also an option, but it is less titratable and less predictable)
2) PEEP/NIPPV
3) Diuretics (IV Lasix)
4) Beta blocker (if HR > 150)
5) Transition to long-term antihypertensive (ie. labetalol and hydralazine)
Two common alpha 2 agonists used in the critical care/ICU environment
- Clonidine
2. dexmedetomidine
Clinical approach to “symptomatic bradycardia”
1) Atropine
2) Pacing (Transcutaneous or TVP)
3) Chronotropy (epinephrine, dopamine, isoproterenol)
4) Calcium (if secondary to hyper-kalemia)
5) Insulin (for beta blocker/CCB overdose)
differential diagnosis for narrow complex PEA arrest (Littman PEA algorithm)
Mechanical RV problem
- Tamponade
- tension PTX
- dynamic hyperinflation
- PE
- Acute MI with rupture
differential diagnosis for wide complex PEA arrest (Littman PEA algorithm)
Metabolic LV problem
- Hyperkalemia
- Sodium channel blockade
- Agonal (terminal) rhythm
- Acute MI with pump failure (severe myocardial dyskinesis)
ECG findings characteristic for hypercalcemia
QTc shortening
ECG findings characteristic for hypocalcemia
QTc lengthening
most common cause of right heart failure
Left-sided heart failure
Causes of Right Heart Failure due to RV Pressure overload
- Left-sided HF (most common cause)
- Pulmonary embolism (common)
- Other causes of PH
- RV outflow tract obstruction
Causes of Right Heart Failure due to RV volume overload
- Tricuspid regurgitation
- Pulmonary regurgitation
- Atrial septal defect
Causes of Right Heart Failure due to RV ischemia
- RV myocardial infarction
2. Ischemia may contribute to RV dysfunction in RV overload states (especially pressure overload)