Cinical Medicine Flashcards
What is an RVG or a MUGA?
Patients red cells labeled with Tc stannous pyrophosphate
Provides a movie of amount of blood in the heart chambers at stage of cardiac contractility and filling
Use to assess ventricular function
Advantage is body relatively transparent to photons emitted by Tc
What are the different views in imaging the heart?
Coronal Axial 2 chamber section 3 chamber section 4 chamber section Short axis
What conditions would possibly warrant the use of nuclear medicine to assess ventricular function due to difficulty obtaining a clear echo?
Lung disease
Obesity
Chest deformity
What are the advantages of using radionuclide ventriculography for evaluating ventricular function?
Lack of need for an acoustic window
Relatively wide availability
Ease of quantification
Reasonably low radiation dose and risk
How does perfusion scanning work?
Takes advantage of fact that radionuclides can be designed to distribute in heart on basis of myocardial blood flow
If radionuclide injected during stress, more will get to normal regions where flow has increased and less to areas where it hasn’t
What is coronary flow reserve?
Normal coronary system will allow blood flow to increase by a factor of 3-5 times resting flow under stress like exercise, etc.
What is a dobutamine stress study?
Dobutamine infused to increase heart rate and myocardial contractility
Atropine also given
Radionuclide injected at peak of exercise
Done when patients cannot exercise naturally - prior stroke, lower extremity weakness, or injury)
What test is used more in nuclear cardio than dobutamine stress studies and how does it work?
Infused adenosine or dipyridamole
Induces pharmacological vasodilation - flow increased in normally perfused regions but not stenosed
Not a true simulation of exercise
Contraindicated in patients with reversible airway disease or conduction abnormalities
Which radionuclides are used in nuclear imaging to look at perfusion?
Thallium (Tl) - potassium analog, depends on function Na-K pump in heart - images immediately after injection look at perfusion in setting of stress, images 2-24 hrs later look at potassium distribution and viability of cells = redistribution - of redistribution doesn’t happen injury is irreversible
Tc sestamibi - enters myocardial cells by diffusion and binds to intracellular membranes - better images of perfusion but doesn’t show redistribution
Need both - thallium used during rest, sestamibi during stress
What are resting EKG abnormalities that decrease the sensitivity and specificity of the standard exercise test?
LVH with strain
Conduction abnormalities, particularly LBBB
Digitalis
Want to add perfusion scanning
What is a limitation of perfusion scanning?
Cost - can be $2000
What are contraindications to MRI?
Cerebral aneurysm clip
History of metal fragment in eye
Cardiac pacemaker or implantable defibrillators (that’s not MRI conditional)
Severe claustrophobia
What are the two different types of imaging used in MRI?
Spin echo - fat is bright, muscle is gray, blood is dark - typically used to look at structure
Gradient echo - fat less bright, muscle is gray, blood is white - typically used to look at function
No contrast agent or dye needed to see contrast
What are four diagnoses that can be made by MRI?
Constrictive pericarditis
Aortic dissection or coarctation
Arrhythmogenic right ventricular dysplasia
What are the major coronary artery disease risk factors?
Major independent - elevated serum cholesterol, elevated BP, smoking, diabetes, advancing age, family history, obesity and physical inactivity
What is the effect of serum cholesterol level on the incidence of CAD?
Increased probability of adverse coronary and cardiovascular events is continuous and graded
1% increase in serum cholesterol corresponds to 2% increase in incidence of coronary heart disease
Ratio of total cholesterol:HDL is also important, <5 is normal
When does cholesterol reduction reduce coronary events?
When used as primary prevention in persons without Pre existing coronary heart disease or as secondary in persons with it
Middle aged and older men and women
How does smoking combine with other risk factors for coronary heart disease?
Use of tobacco in persons with other risk factors has synergistic effect on risk, interacts in multiplicative fashion
Passive exposure can increase risk 3 fold
Risk even higher if older, parent with MI, overweight, HT, diabetes or hypercholesterolemia
What are the vascular effects of smoking?
Increased inflammation Reduction in NO availability Increased fibrinogen Enhanced platelet reactivity Increased whole blood viscosity Reduced HDL Promotion of oxidation of LDL
What is the effect of smoking cessation in patients with known CAD?
Smoking cessation has accounted for 24% of decline of coronary heart disease
30 YO who stops improves life expectancy about 5 yrs
Double risk of death if revert to smoking after MI
What are the guidelines and efficacy of physician counseling on smoking cessation?
Ask about smoking at every clinical visit
Advise all smokers to stop
Assist patient by advising a quit date and providing self help materials
Arrange follow up to assess smoking status and encourage continued abstinence
What is the prevalence of hypertension and how does age affect this prevalence?
33% of adults in US
rises with age
Why is it important to treat mild hypertension?
Approximately 2/3 of all hypertension related coronary heart disease occurs within this range of BP
What is the prevalence of diabetes in the US?
7% of population
>90% of those are non insulin dependent
