Imaging, Hemeodynamics Flashcards

1
Q

List the major imaging modalities in cardiovascular imaging

A
Chest X-Ray
Echocardiogram- Transthoracic (TTE)
Echocardiogram-Transesophageal (TEE)
Nuclear Perfusion:  
Cardiac Computer Tomography (CT)
Magnetic Resonance Imaging (MRI)
Coronary Angiography
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2
Q

Chest X-Ray

A
•	Advantages
o	Commonly available
o	Fast, inexpensive
o	Portable
o	Low radiation

• Limitations
o Poor resolution of structures
o Non-dynamic
o Small radiation risk

•	Uses
o	Heart size
o	Pulmonary edema
o	Pericardial Ca2+
o	Pulmonary pathology
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3
Q

Echocardiogram- Transthoracic (TTE)

A
•	Advantages
o	Widely available
o	Portable to hospital bedside (critical care)
o	Common standard for LV function, valves
o	Hemodynamic estimates
o	Long history and good knowledge base
o	Can image stress tests
o	No radiation exposure

• Limitations
o Bone, fat, and lung block sound waves

• Uses

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4
Q

Echocardiogram-Transesophageal (TEE)

A

• Advantages
Located next to heart = good positioning
o Widely available
o Portable to hospital bedside (critical care)
o Common standard for LV function, valves
o Hemodynamic estimates
o Long history and good knowledge base
o Can image stress tests
o No radiation exposure

• Limitations
o Invasive with sedation

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5
Q

Nuclear Perfusion

A
•	Definition
o	Inject radioactive particle that sticks in mitochondria to show active, alive cells
o	Follows blood flow
o	Signal increases in proportion to flow
o	Image can stay fixed for hours
•	Advantages
o	Commonly available stress test imaging
o	Images blood flow dynamics (a functional study)
o	Long history → good prognostic data
o	LV function
•	Limitations
o	Stress test medication reactions
o	Moderate radiation exposure
•	Uses
o	Functional coronary artery testing
o	LV size and function, viability
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6
Q

Cardiac Computer Tomography (CT)

A

• Definition
o Inject iodine contrast

• Advantages
o Non-invasive precise coronary anatomy
o Some plaque characterization
o High sensitivity and negative predictive value
o Create 3D structure views for EP intervention

• Limitations
o IV contrast so problem if patient has kidney disease
o Limited availability
o Moderate radiation exposure

• Uses
o Coronary angiography, chamber size and function
o 3D reconstructions of atria, etc.

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7
Q

Magnetic Resonance Imaging (MRI)

A

• Advantages
o Gold standard for LV function and damage
o Indirect hemodynamic measurements possible
o No radiation
o Combines with stress testing for coronary evaluation

• Limitations
o Non-compatible with ferrous metal
o Limited availability
o Claustrophobia

• Uses
o Ventricular function, viability, infarct

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8
Q

Coronary Angiography

A
•	Advantages
o	Gold standard for coronary anatomy
o	Direct hemodynamic measurement 
o	LV function
o	Concomitant intervention 

• Limitations
o Invasive, expensive, medium availability
o Modest contrast
o Moderate radiation

• Uses
o Coronary angiography and intervention
o Hemodynamics, pulmonary pressures

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9
Q

List approximate normal ranges for pressures in the cardiac chambers

A
o	IVC: 2-8 mm Hg
o	RA: 2-8 mm Hg
o	RV: 15-35/ 2-8 mm Hg
o	Pulmonary Artery: 15-35/ -14 mm Hg
o	Pulmonary Capillary Wedge: 4-14 mm Hg
o	LA: 4-14 mm Hg
o	LV: 100-140/ 4-14 mm Hg
o	Aorta: 100-140/ 60-90 mm Hg
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10
Q

List approximate normal ranges for oxygen saturations in the cardiac chambers.

A
o	IVC: 75-80%
o	SVC: 70-75%
o	Coronary Sinus: 25% 
o	Pulmonary arteries: 75%
o	Pulmonary Veins: 92-100%
o	Aorta: 92-100%
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11
Q

Explain the general formula linking pressure, flow and resistance.

A

ΔP = QR

o ΔP: pressure gradient
o Q: blood flow; represents CO when applied to entire CVS
o R: vascular resistance

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12
Q

Explain the formula linking pressure, flow and resistance in the cardiac system

A

CO = (MAP-RAP)/SVR

Like CO = ΔP/R
ΔP = mean arterial pressure (MAP) – systemic venous pressure/pressure returning to right atrium (RAP)
• RAP = RV filling; estimated from jugular venous pressure
o R = total systemic vascular resistance (SVR); calculated once have pressures and CO; estimate clinically from warmth of legs

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13
Q

Explain the formula linking pressure, flow and resistance in the pulmonary system, including the significance of Fick Cardiac Output

A

CO = (mPAP - Wedge)/PVR

o mPAP: mean pulmonary artery pressure
o Wedge: LA pressure equivalent (filling pressure for LV); correlates with crackles on exam
o PVR: Pulmonary vascular resistance
o CO: marker for LV function (moving blood through systemic system)
• Fick Cardiac Output = (O2 consumption [ml O2/min]) / ((Art-Ven) O2 content difference [ml O2/L])
• O2 content= (1.36 ml O2/g Hgb)(Hgb g/dl)(%O2 saturation)
• Low CO: large (A-V) difference
• PA O2 saturation can be surrogate for CO if O2 consumption, Hgb and arterial O2 saturation are constant

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14
Q

List the normal values for cardiac output, pulmonary and systemic vascular resistance.

A

o CO: 3-7 L/min
o PVR: 1.325-2.5 Wood units or 100-200 Dyn-sec/cm5
o SVR: 11-17 Wood units or 900-1400 Dyn-sec/cm5
• Wood units = (mean PA – Wedge)/CO

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15
Q

Define and list the types of shock

A

Hemodynamic state resulting from inadequate systemic tissue oxygenation:

  • hypovolemic
  • cardiogenic
  • distributive
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16
Q

Explain Hypovolemic shock

A
  • Trauma, dehydration
  • Low blood volume
  • Decreased Pulmonary Capillary Wedge Pressure (PCWP) from low venous return
  • LV filling pressure decreases → decreased CO
  • Compensatory SVR increase → blood flow to brain
17
Q

Explain Cardiogenic Shock

A
  • Ischemic, myocardial, valvular causes
  • Decreased CO
  • Release of endogenous vasoconstrictors
  • Norepinephrine, angiotensin II, vasopressin, endothelin
  • Increase in SVR → blood redistributed to vital organs
  • Ineffective LV unloading → increase in pulmonary venous pressure → pulmonary congestion
  • When right ventricle also injured: decreases flow across pulmonary capillary bed → decreased PCWP
18
Q

Explain Distributive Shock

A
  • Anaphylaxis or sepsis
  • Decreased vascular tone (SVR) → compensatory CO increase
  • PCWP low (high flow state)
19
Q

Describe the typical changes to flow, pressure and resistance that occur during aortic valve stenosis

A
  • cardiogenic shock
  • progressive narrowing of aortic valve area
  • PCWP: H
  • SVR: H
  • CO: L
20
Q

Describe the typical changes to flow, pressure and resistance that occur during cardiomyopathy

A
  • Cardiogenic shock
  • Decreased CO: low stroke volume or HR (systolic HF) and/or high filling pressures (diastolic HF)
  • PCWP: H
  • SVR: H
  • CO: L
21
Q

Describe the typical changes to flow, pressure and resistance that occur during sepsis

A
  • Distributive shock
  • infections, anaphylaxis leading to peripheral vasodilation
  • PCWP: L
  • SVR: L
  • CO: H
22
Q

Describe the typical changes to flow, pressure and resistance that occur during sepsis late stage

A
  • Distributive and cardiogenic
  • later in course; inflammatory mediators have direct depressive effect on myocardial contractility
  • PCWP: L, normal
  • SVR: L
  • CO: Normal or low
23
Q

Describe the typical changes to flow, pressure and resistance that occur during pulmonary embolism

A
  • Hypovolemic (from LV perspective)
  • clot travels to lung bed, blocking flow
  • PCWP: L
  • SVR: H
  • CO: L
24
Q

Describe the typical changes to flow, pressure and resistance that occur during acute hemorrhage

A
  • Hypovolemic
  • loss of O2 carrying capacity per unit blood volume
  • PCWP: L
  • SVR: H
  • CO: L