Unit 3 - CV Flashcards
1
Q
What properties do myocardial cells share with neural and skeletal tissues?
A
They initiate and propagate action potentials that trigger coordinated myocardial contraction.
2
Q
What are intercalated discs in cardiac myocytes?
A
Specialized junction complexes that transfer mechanical forces and contain gap junctions for action potential spread.
3
Q
How many mL of O2 do cardiac myocytes consume at rest?
A
8-10 mL O2/100g/min.
4
Q
Define automaticity in cardiac cells.
A
The ability to generate an action potential spontaneously.
5
Q
What does excitability refer to in cardiac cells?
A
The ability to respond to an electrical stimulus by depolarizing and firing an action potential.
6
Q
What is conductance in the context of cardiac cells?
A
The ability to transmit electrical current through ion channels.
7
Q
What determines the resting membrane potential (RMP)?
A
Serum K+ is the primary determinant of RMP.
8
Q
What happens to RMP when serum K+ decreases?
A
RMP becomes more negative, making myocytes more resistant to depolarization.
9
Q
What is threshold potential (TP)?
A
The voltage change required to initiate depolarization.
10
Q
How does increased serum Ca++ affect threshold potential?
A
TP becomes more positive, and cells become more resistant to depolarization.
11
Q
What is depolarization in cardiac cells?
A
The movement of a cell’s membrane potential to a more positive value.
12
Q
What is the refractory period?
A
The time when a cell is resistant to subsequent depolarization.
13
Q
What is hyperpolarization?
A
The movement of a cell’s membrane potential to a more negative value beyond the baseline RMP.
14
Q
What is the primary function of the Na+/K+ ATPase in excitable tissue?
A
To restore ionic balance towards RMP.
15
Q
What is the effect of digoxin on Na+/K+ ATPase?
A
It inhibits the Na+/K+ ATPase.
16
Q
What are the phases of the cardiac action potential (AP) in myocytes?
A
Phase 0, Phase 1, Phase 2, Phase 3, Phase 4.
17
Q
What occurs during Phase 2 of the cardiac action potential?
A
Plateau phase where Ca++ enters and K+ exits.
18
Q
What is the intrinsic firing rate of the SA node?
A
70-80 BPM.
19
Q
How does the sympathetic nervous system affect heart rate?
A
Increases HR by increasing Na+ and Ca++ conductance.
20
Q
What is the equation for oxygen content (CaO2) in arterial blood?
A
CaO2 = (Hgb • SaO2 • 1.34) + (PaO2 • 0.003).
21
Q
What does the O2 extraction ratio (EO2) indicate?
A
How much O2 is extracted by the tissues.
22
Q
What is Poiseuille’s Law used to understand?
A
The relationship between blood flow, vessel diameter, viscosity, and tube length.
23
Q
What is the normal value for cardiac output (CO)?
A
5-6 L/min.
24
Q
What does the Frank-Starling mechanism describe?
A
The relationship between end-diastolic volume (preload) and stroke volume (SV).
25
What is the effect of decreased preload on stroke volume?
It leads to a lower stroke volume.
26
What is contractility (inotropy)?
The ability of myocardial sarcomeres to perform work independently of preload and afterload.
27
What factors increase contractility?
* SNS stimulation
* Catecholamines
* Ca++
* Digitalis
* PDEi
28
What is afterload?
The force that the ventricle must overcome to eject its stroke volume.
29
What is the normal range for systemic vascular resistance (SVR)?
800-1,500 dynes•sec•cm-5.
30
How does wall stress relate to myocardial oxygen consumption?
Increased wall stress also increases myocardial O2 consumption.
31
What happens during the cardiac cycle?
It involves the sequence of events in the heart during one complete heartbeat.
32
What is stress in the context of cardiac function?
Force that holds the heart together
33
How is wall stress reduced?
By:
* ↓ Intraventricular pressure
* ↓ Radius
* ↑ Wall thickness
34
What is the relationship between wall stress and myocardial O2 consumption?
Anything that increases wall stress also increases myocardial O2 consumption
35
What therapies can reduce afterload?
Arterial vasodilators (Propofol, Clevidipine) & sympathectomy (Regional anesthesia)
36
What is the cardiac cycle?
A sequence of electrical & mechanical events from the beginning of one heartbeat to the next, divided into systole and diastole
37
What precedes mechanical events in the cardiac cycle?
Electrical events
38
What does the pressure-volume (PV) loop assess?
Systolic and diastolic function as well as the integrity of the cardiac valves
39
What does the height of the PV loop represent?
Ventricular pressure
40
What does the width of the PV loop represent?
Ventricular volume
41
What does the area of the PV loop indicate?
Myocardial workload
42
What are the four phases of the ventricular-volume loop?
1. Period of ventricular filling
2. Isovolumetric contraction
3. Ventricular ejection
4. Isovolumetric relaxation
43
What is external work in cardiac function?
The amount of work the ventricle must do to eject its stroke volume (SV)
44
How is external work estimated?
By multiplying SV (Width) by the mean aortic pressure (Height)
45
What affects the morphology of the PV loop?
Changes in preload, contractility, and afterload
46
How does an increase in preload affect the PV loop?
The PV loop gets wider but returns to the original end-systolic volume
47
How does a decrease in preload affect the PV loop?
The PV loop gets narrower but returns to the original end-systolic volume
48
How does an increase in contractility affect the PV loop?
The PV loop gets wider, taller, & shifts to the left
49
How does a decrease in contractility affect the PV loop?
The PV loop gets narrower, shorter, & shifts to the right
50
How does an increase in afterload affect the PV loop?
The PV loop gets narrower, taller, & shifts the end-systolic volume to the right
51
How does a decrease in afterload affect the PV loop?
The PV loop gets wider, shorter, & shifts the end-systolic volume to the left
52
Where do the left and right coronary arteries arise from?
The aortic root (from the sinus Valsalva)
53
What does the left anterior descending artery perfuse?
Anterolateral & apical walls of the left ventricle and anterior two-thirds of the interventricular septum
54
What does the circumflex artery supply?
Left atrium and lateral & posterior walls of the left ventricle
55
What does the right coronary artery perfuse?
Right atrium, right ventricle, interatrial septum, and posterior third of the interventricular septum
56
What defines coronary dominance?
The origin of the posterior descending artery (PDA), which can arise from RCA, circumflex, or both
57
What is the role of the coronary sinus?
Returns cardiac venous blood to the right atrium
58
What is coronary reserve?
The difference between coronary blood flow at rest and maximal dilation
59
What are the determinants of O2 delivery?
Coronary blood flow, CaO2, & O2 extraction
60
What are the determinants of O2 demand?
Preload, afterload, contractility, & wall stress
61
What happens during ischemia?
Anaerobic metabolism leads to lactic acid production, impairing myocardial performance
62
What are the classic symptoms of aortic stenosis?
Syncope, angina, and dyspnea (SAD)
63
What is the normal size of the aortic valve orifice?
2.5 – 3.5 cm2
64
What is a diagnostic indicator for severe aortic stenosis?
Mean transvalvular pressure gradient >40 mmHg
65
What compensatory mechanisms occur in aortic stenosis?
Increased thickness of the LV wall, decreased compliance, & smaller chamber radius
66
What is the effect of tachycardia on myocardial O2 supply and demand?
↓ Supply & ↑ demand
67
What is the effect of increased afterload on myocardial O2 demand?
Increases myocardial O2 demand
68
What is the role of adenosine in coronary circulation?
It is a potent coronary vasodilator released as MVO2 increases
69
What causes coronary artery constriction?
α (Epicardial), Histamine 1
70
What causes coronary artery dilation?
β2 (Endocardial), Histamine 2, Muscarinic
71
What is aortic insufficiency?
Aortic insufficiency leads to volume overload & eccentric hypertrophy. A portion of the previous ejected SV re-enters the left ventricle during diastole.
72
What causes aortic insufficiency?
Causes include incomplete valve or dilation of the aortic root or its supporting structures, endocarditis, and aortic root dissection.
73
What are the chronic causes of aortic insufficiency?
* Valvular calcification
* Marfan syndrome
* Ehler-Danlos syndrome
* Ankylosing spondylitis
74
What must be done before initiating cardiopulmonary bypass in a patient with aortic regurgitation?
Cardioplegia must be injected retrograde or directly into each coronary ostia.
75
What happens if the mitral valve is incompetent in a patient with aortic insufficiency?
An elevated LVEDP will reflect to the pulmonary circulation, causing congestion.
76
What are the anesthesia goals for aortic insufficiency?
* Heart rate: Elevate
* Heart rhythm: NSR
* Preload: Maintain or increase
* Afterload: Decrease
* Contractility: Maintain
* Pulmonary vascular resistance: Maintain
* SVR: Prevent increased SVR
77
What characterizes the arterial waveform in aortic insufficiency?
Increased pulse pressure, sharp upstroke, low diastolic pressure, and bisferiens pulse.
78
What is the normal mitral valve area?
Normal = 4 – 6 cm2; Severe = <1 cm2.
79
What is the most common cause of mitral stenosis in the US?
Endocarditis and mitral calcification.
80
What can increased left atrial pressure lead to in mitral stenosis?
Pulmonary hypertension and a-fib.
81
What are the anesthetic goals for mitral stenosis?
* Heart rate: Low side of normal w NSR
* Preload: Maintain
* Afterload: Maintain
* Contractility: Maintain
* SVR: Maintain
* Pulmonary vascular resistance: Avoid increase
82
What are common causes of mitral insufficiency?
* Mitral valve prolapse
* Myxomatous degeneration
* Ischemic heart disease
* Rheumatic fever
* Rheumatoid arthritis
* Endocarditis
* Lupus
83
What does mitral insufficiency cause in terms of volume changes?
Volume overload & eccentric hypertrophy.
84
What should be avoided in patients with mitral insufficiency?
* Slower HR
* Increased pressure gradient between LV & LA
* Increased SVR
* Increases size of valve orifice
85
What are the anesthetic goals for mitral insufficiency?
* HR: Elevated
* Heart rhythm: NSR
* Preload: Maintain or increase
* Afterload: Decrease
* Contractility: Maintain
* SVR: Decrease
* PVR: Avoid increase
86
What is the risk after mitral valve repair?
Risk of systolic anterior motion (SAM) of the anterior leaflet, leading to outflow obstruction.
87
What are the locations to listen for pathologic murmurs?
* Aortic Stenosis: Right sternal border
* Aortic Regurgitation: Right sternal border
* Mitral Stenosis: Apex & left axilla
* Mitral Regurgitation: Apex & left axilla
88
What is TAVR?
TAVR is a minimally invasive method of replacing the aortic valve in patients with aortic stenosis.
89
What are the approaches for TAVR?
* Transfemoral
* Transaortic
* Transapical
90
What complications can occur with TAVR?
* Stroke
* Perivalvular leak
* Dysrhythmias
* Acute hemodynamic instability
* Tamponade
* Coronary occlusion
* Hemorrhage due to vascular injury
91
What are the patient-related conditions that increase cardiac risk?
* History of ischemic heart disease
* CHF
* Cerebrovascular disease
* DM
* Serum creatinine >2 mg/dL
* High risk surgeries
92
What is myocardial oxygen imbalance?
Myocardial O2 balance is determined by the ratio of O2 supply relative to demand.
93
What factors can lead to decreased O2 delivery?
* Decreased coronary flow
* Tachycardia
* Decreased aortic pressure
* Decreased vessel diameter
* Decreased CaO2
* Hypoxemia
* Anemia
* Decreased O2 extraction
94
What are the compensatory mechanisms for heart failure?
* Chronic SNS activation
* Down-regulation of Beta R
* Excessive vasoconstriction
* Fluid retention
* Cardiac remodeling
95
What is the role of BNP in heart failure?
BNP is a biomarker for assessing risk in patients with heart failure, promoting natriuresis, diuresis, and vasodilation.
96
What is secondary hypertension?
Secondary HTN is an elevated BP that has a definitive cause.
97
What are the causes of secondary hypertension?
Causes include conditions such as renal disease, endocrine disorders, and sleep apnea.
98
What is the impact of chronic hypertension on the body?
* LVH
* CAD
* CHF
* Stroke
* Arterial aneurysm
* Renal disease
99
What should be done for patients on ACEi/ARB therapy who experience hypotension?
Treat with vasopressin, terlipressin, or methylene blue.
100
What is the preferred treatment for hypertensive crisis?
Antihypertensive agents that target the SNS or myocardium and vascular smooth muscle.
101
What is the benefit of using mixed alpha 1/Beta 1 & Beta 2 antagonists?
Systemic vasodilation due to the alpha-1 component
102
What can happen if a non-selective beta blocker is given to a patient in hypertensive crisis?
It can precipitate heart failure
103
What types of drugs target the myocardium and vascular smooth muscle?
CCB and vasodilators
104
How do vasodilators promote vasodilation?
By increasing nitric oxide
105
What is the effect of hydralazine on afterload?
Reduces afterload
106
What is the effect of nitroglycerin on preload?
Reduces preload
107
What is the effect of sodium nitroprusside on preload and afterload?
Reduces both preload and afterload
108
What do ACE inhibitors and ARBs inhibit?
Angiotensin-2-mediated vasoconstriction and aldosterone release
109
How do diuretics decrease blood pressure?
By reducing intravascular volume
110
What do aldosterone antagonists block?
Aldosterone at mineralocorticoid receptors
111
What is the mechanism of action of calcium channel blockers (CCBs)?
Increase vasodilation and decrease inotropy, chronotropy, and dromotropy
112
Which CCBs are effective in reducing heart rate in patients with tachycardia or atrial fibrillation?
Verapamil and diltiazem
113
Rank CCBs in order of their impairment of contractility from highest to lowest.
Verapamil > Nifedipine > Diltiazem > Nicardipine
114
In a patient with decreased contractility, which CCB is a better choice?
Diltiazem
115
Which CCB is proven to reduce morbidity and mortality from cerebral vasospasm?
Nimodipine
116
What do all CCBs bind to?
The alpha-1-subunit of the L-type calcium channel
117
What is the mechanism of action of Clevidipine?
Arterial vasodilation reduces systemic vascular resistance without affecting preload
118
What are the contraindications for Clevidipine?
Allergy to eggs, impaired lipid metabolism, severe aortic stenosis
119
What is the role of the pericardium?
Surrounds the heart and provides a minimal friction environment
120
What is acute pericarditis usually caused by?
Inflammation
121
What does constrictive pericarditis lead to?
Reduced diastolic filling due to thickening of the pericardium
122
What is the treatment for constrictive pericarditis?
Pericardiotomy
123
What are the anesthetic considerations for constrictive pericarditis?
* Avoid bradycardia * Preserve contractility * Maintain afterload
124
What is pericardial effusion?
Accumulation of fluid inside the pericardial sac without increased pericardial pressures
125
What is cardiac tamponade?
Fluid accumulation inside the pericardium that compresses the myocardium
126
What is Beck's triad?
* Muffled heart tones * Jugular venous distention * Hypotension
127
What is pulsus paradoxus?
Decreased SBP by >10 mmHg during inspiration
128
What does Kussmaul’s sign indicate?
Increased CVP and jugular venous distention during inspiration
129
What are the surgical management options for cardiac tamponade?
* Pericardiocentesis * Pericardiostomy
130
What are complications of pericardiocentesis and pericardiostomy?
* Pneumothorax * Re-accumulation of pericardial fluid * Puncture of coronary vessels
131
What is the preferred anesthetic management for cardiac tamponade?
Local anesthesia over general anesthesia for better hemodynamic stability
132
What is the #1 goal in anesthetic management of cardiac tamponade?
Preserve myocardial function
133
What type of ventilation is preferred in cardiac tamponade cases?
Spontaneous ventilation over positive pressure ventilation
134
What is infective pericarditis (IE)?
Typically a bacterial infection of the heart valves & endocardium caused by bacteremia
135
When is antibiotic prophylaxis recommended for infective endocarditis?
Only if the patient is at higher risk for developing IE
136
List patient-related factors that increase the risk of infective endocarditis.
* History of IE
* Prosthetic heart valve
* Heart transplant with valvopathy
* Certain congenital heart defects
137
What are surgery-related factors that necessitate antibiotic prophylaxis against endocarditis?
* 'Dirty' procedures
* Dental procedures with gingival manipulation
* Certain respiratory procedures
* Biopsies of infected lesions
138
True or False: Antibiotic prophylaxis is required for mitral valve prolapse.
False
139
What IV antibiotics are used for IE prophylaxis?
* Ampicillin
* Cefazolin
* Ceftriaxone
* Clindamycin
140
What is hypertrophic cardiomyopathy?
The most common autosomal dominant cardiovascular disease and cause of sudden cardiac death in young athletes
141
What causes LV outflow tract (LVOT) obstruction in hypertrophic cardiomyopathy?
* Congenital hypertrophy of the intraventricular septum
* Systolic anterior motion (SAM) of the anterior leaflet of the mitral valve
142
What are the surgical options to correct LVOT obstruction?
* Septal myomectomy
* Alcohol injection into septal perforator arteries
* Mitral valve replacement
143
What is required for a patient receiving a coronary stent?
Dual antiplatelet therapy (DAPT) to prevent stent thrombosis
144
What are the components of dual antiplatelet therapy?
* Aspirin (irreversible cyclooxygenase inhibitor)
* Thienopyridine (usually clopidogrel or ticlopidine)
145
When can elective surgery be performed after stent placement?
Varies with type of stent: Angioplasty w/o stent = 2-4 weeks, Bare metal stent = 30 days, Drug eluting stent = 6-12 months depending on the situation
146
What is the function of cardiopulmonary bypass (CPB)?
Allows the surgeon to operate on an immobile heart by circulating blood through a bypass circuit
147
What type of pump is preferred in CPB and why?
Centrifuge pump due to lower risk of high pressure and reduced risk of line rupture
148
What is the primary advantage of a membrane oxygenator over a bubble oxygenator?
Safer, as it carries a lower risk of cerebral air embolism
149
What is the primary purpose of cardioplegia during CPB?
Arrests the heart in diastole to reduce myocardial oxygen consumption
150
When is the most common time of awareness during CPB?
During sternotomy or rewarming
151
What are the indications for an intra-aortic balloon pump (IABP)?
* Cardiogenic shock
* Myocardial infarction
* Intractable angina
152
What are the contraindications for an intra-aortic balloon pump?
* Severe aortic insufficiency
* Descending aortic disease
* Severe peripheral vascular disease
* Sepsis
153
What is the purpose of the intra-aortic balloon pump inflating during diastole?
Augments coronary perfusion
154
What is the primary function of a Left Ventricular Assist Device (LVAD)?
Unloads the failing heart by pumping blood from the LV to the aorta
155
What is the most common cause of death in patients with LVAD?
Sepsis
156
What is the mechanism for the development of abdominal aortic aneurysm (AAA)?
* Destruction of elastin & collagen
* Inflammation
* Endothelial dysfunction
* Platelet activation
* Atherosclerosis
157
What is the classic triad of AAA rupture?
* Hypotension
* Back pain
* Pulsatile abdominal mass
158
At what size is surgical correction of AAA recommended?
When the aneurysm exceeds 5.5 cm or grows more than 0.6-0.8 cm per year
159
What does the Crawford classification classify?
Aortic aneurysms into 4 types based on involvement of the thoracic & abdominal aorta
160
What is anterior spinal artery syndrome?
Ischemia or infarction to the anterior spinal cord segments due to interruption of blood flow to the artery of Adamkiewicz
161
What are the symptoms of anterior spinal artery syndrome?
* Flaccid paralysis of the lower extremities
* Bowel & bladder dysfunction
* Loss of temperature & pain sensation
162
What is the significance of the artery of Adamkiewicz?
It perfuses the anterior two-thirds of the spinal cord in the thoracolumbar region
163
What is the preferred method for carotid endarterectomy (CEA)?
Awake status is best for assessing neurologic integrity
164
What glucose level should be treated to reduce stroke risk on the day of surgery?
Hyperglycemia (>200 mg/dL)
165
What is the physiological response to aortic cross-clamping?
Creates central hypervolemia by increasing venous return and shifts blood volume proximal to the clamp
166
What should be avoided to treat hyperglycemia?
Glucose-containing solutions
## Footnote
Hyperglycemia should be treated with insulin.
167
What blood pressure range should be maintained during cross-clamping?
Normal to slightly elevated BP
## Footnote
This is because the vessels in ischemic regions are maximally dilated and perfusion is pressure dependent.
168
What should the SBP be kept under after cross-clamping is revoked?
145 mmHg
## Footnote
This helps reduce the risk of bleeding at the graft site.
169
What reflex can be activated by surgical stimulation?
Baroreceptor reflex
## Footnote
This can lead to hypotension and bradycardia.
170
What can head rotation, flexion, or extension compress?
Carotid and/or vertebral arteries
## Footnote
This can reduce cerebral perfusion.
171
What should be maintained regarding carbon dioxide levels?
Normocapnia or mild hypocapnia
## Footnote
Hypercapnia can dilate cerebral vessels and create a 'steal' phenomenon.
172
What are some postoperative considerations?
Hematoma, RLN injury, labile BP, carotid denervation, stroke
## Footnote
Hypertension is the most common postoperative issue and can cause reperfusion injury.
173
What does Carotid Artery Angioplasty (CAS) use for access?
Percutaneous trans vascular access
## Footnote
This allows the stent to be passed into the carotid artery.
174
What anticoagulation is maintained during CAS?
Heparin (50-100 u/kg)
## Footnote
This is to maintain ACT > 250 seconds.
175
What is the most common complication of CAS?
Thromboembolic stroke
## Footnote
This occurs due to atherosclerotic debris that lodges in the cerebral vasculature.
176
What device is used to catch debris during CAS?
Distal protection filter
## Footnote
This is placed beyond the angioplasty balloon.
177
How is an embolic stroke treated?
TPA
## Footnote
TPA is a thrombolytic agent used in treating strokes.
178
What occurs during Subclavian Steal Syndrome?
Occlusion of the subclavian or innominate artery proximal to the vertebral artery
## Footnote
This usually occurs on the left side.
179
What is the effect of Subclavian Steal Syndrome on blood flow?
Reverse flow towards the ipsilateral subclavian artery
## Footnote
Arterial blood is 'stolen' from the posterior cerebral circulation.
180
What is the treatment of choice for Subclavian Steal Syndrome?
Subclavian endarterectomy
## Footnote
This procedure helps restore normal blood flow.
181
What symptom is associated with Subclavian Steal Syndrome?
Lower blood pressure in the ipsilateral arm
## Footnote
The pulse may also be diminished.
