Imaging, Hemeodynamics Flashcards
List the major imaging modalities in cardiovascular imaging
Chest X-Ray Echocardiogram- Transthoracic (TTE) Echocardiogram-Transesophageal (TEE) Nuclear Perfusion: Cardiac Computer Tomography (CT) Magnetic Resonance Imaging (MRI) Coronary Angiography
Chest X-Ray
• 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
Echocardiogram- Transthoracic (TTE)
• 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
Echocardiogram-Transesophageal (TEE)
• 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
Nuclear Perfusion
• 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
Cardiac Computer Tomography (CT)
• 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.
Magnetic Resonance Imaging (MRI)
• 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
Coronary Angiography
• 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
List approximate normal ranges for pressures in the cardiac chambers
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
List approximate normal ranges for oxygen saturations in the cardiac chambers.
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%
Explain the general formula linking pressure, flow and resistance.
ΔP = QR
o ΔP: pressure gradient
o Q: blood flow; represents CO when applied to entire CVS
o R: vascular resistance
Explain the formula linking pressure, flow and resistance in the cardiac system
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
Explain the formula linking pressure, flow and resistance in the pulmonary system, including the significance of Fick Cardiac Output
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
List the normal values for cardiac output, pulmonary and systemic vascular resistance.
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
Define and list the types of shock
Hemodynamic state resulting from inadequate systemic tissue oxygenation:
- hypovolemic
- cardiogenic
- distributive
Explain Hypovolemic shock
- 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
Explain Cardiogenic Shock
- 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
Explain Distributive Shock
- Anaphylaxis or sepsis
- Decreased vascular tone (SVR) → compensatory CO increase
- PCWP low (high flow state)
Describe the typical changes to flow, pressure and resistance that occur during aortic valve stenosis
- cardiogenic shock
- progressive narrowing of aortic valve area
- PCWP: H
- SVR: H
- CO: L
Describe the typical changes to flow, pressure and resistance that occur during cardiomyopathy
- Cardiogenic shock
- Decreased CO: low stroke volume or HR (systolic HF) and/or high filling pressures (diastolic HF)
- PCWP: H
- SVR: H
- CO: L
Describe the typical changes to flow, pressure and resistance that occur during sepsis
- Distributive shock
- infections, anaphylaxis leading to peripheral vasodilation
- PCWP: L
- SVR: L
- CO: H
Describe the typical changes to flow, pressure and resistance that occur during sepsis late stage
- Distributive and cardiogenic
- later in course; inflammatory mediators have direct depressive effect on myocardial contractility
- PCWP: L, normal
- SVR: L
- CO: Normal or low
Describe the typical changes to flow, pressure and resistance that occur during pulmonary embolism
- Hypovolemic (from LV perspective)
- clot travels to lung bed, blocking flow
- PCWP: L
- SVR: H
- CO: L
Describe the typical changes to flow, pressure and resistance that occur during acute hemorrhage
- Hypovolemic
- loss of O2 carrying capacity per unit blood volume
- PCWP: L
- SVR: H
- CO: L
