Cardiology MCQ_PART 09

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A 45-year-old man with a strong family history of ischaemic heart disease presents with atypical chest pains. What pharmacologic agent is likely to be used to produce cardiovascular stress during stress echocardiography in this patient?
 

a) dipyridamole
b) Dobutamine
c) adenosine
d) arbutamine
e) Atropine 

Familial hypertrophic cardiomyopathy is most likely to be secondary to a mutation in:
a) myosin regulatory proteins
b) myosin binding protein-C
c) Myosin light chains
d) Troponin I
e) Troponin T

A 56 year old male has a history of aortic stenosis. Which of the following is associated with aortic stenosis?
a) atrial fibrillation
b) systolic ejection murmur
c) increased pulse pressure
d) diastolic murmur
e) right heart failure

EXPLANATIONS



MCQ 01 ANSWER

The correct answer is A
Stress echocardiography has been developed in recent years as an effective noninvasive test for the detection and assessment of coronary artery disease. This method combines exercise with 2-dimensional echocardiography, which can assess regional and global left ventricular function during stress. Dobutamine infusion, a pharmacologic means of producing cardiovascular stress, appears to be an excellent alternative to exercise in echocardiographic studies. Currently, it is reserved for patients who cannot exercise at a meaningful level because of advanced age, physical deconditioning, or other factors.


Dobutamine infusion is the method used most often for pharmacologic stress echocardiography. Graded dobutamine infusion--10 to 40 micrograms/kg per minute in 3-minute stages--increases myocardial oxygen demand in a fashion similar to that of staged exercise. During the dobutamine infusion, it is apparent that heart rate, contractility, and blood pressure are increased. Dobutamine has the advantage of rapid onset of action, and its effects can be reversed by giving an intravenous beta-blocker. A synthetic catecholamine that has a relatively short half-life (about 2 minutes) , dobutamine has strong agonist activity at the beta1 receptor and mild agonist activity at the beta2 and alpha1 receptors.


Atropine can be used to increase heart rate, if necessary, and is usually administered at the peak dobutamine dose. It is usually given as a 0.5-mg bolus and in 0.25-mg increments every 60 seconds (maximum dose, 1-1.5 mg) until the desired heart rate is achieved.


Dobutamine infusion is stopped after images are acquired at peak heart rate--or sooner if the patient has tachyarrhythmias.

MCQ 02 ANSWER

The correct answer is B


Molecular genetic research has demonstrated that familial hypertrophic cardiomyopathy
is caused by a mutation in one of nine genes that encode sarcomere proteins. Sarcomeres are the contractile units within the cardiac cells; these are composed of many proteins that are organized into thin and thick filaments. These filaments slide with respect to each other during cardiac contraction.
Hypertrophic Cardiomyopathy
Mutations in thick filament proteins called cardiac B myosin heavy chain or cardiac myosin binding protein-C appear to account for approximately 82% of hypertrophic cardiomyopathy. Mutations in thin filament proteins cardiac troponin T and a tropomyosin account for about 13% of hypertrophic cardiomyopathy. Mutations in two other sarcomere proteins, the myosin regulatory and essential light chains are quite rare and contribute less than 5% to hypertrophic cardiomyopathy. Although these percentages are only estimates, they indicate that more disease-causing genes will be identified.


A tenth gene has been identified that is a non-sarcomere protein (a subunit of protein kinase A) is associated with individuals who have both hypertrophic cardiomyopathy and Wolf-Parkinson-White syndrome.

MCQ 03 ANSWER

With aortic stenosis there is a systolic ejection murmur that is heard loudest at the second right intercostal space. Atrial fibrillation is common in mitral stenosis. It is also seen in mitral regurgitation, however, less commonly than with mitral stenosis.
Aortic stenosis typically is not associated with atrial fibrillation.The pulse pressure is the difference between systolic and diastolic pressure. An increased pulse pressure is seen with aortic regurgitation.It manifests itself with various signs: Quincke's sign, Duroziez's sign and a 'water hammer pulse'. diastolic murmur is heard with several different valvular conditions, including aortic regurgitation.


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Comments

1 comments to "Cardiology MCQ_PART 09"

Anonymous said...
September 23, 2010 at 2:07 AM

1-I'll go with dobutamine....it can be adenosine or dipyridimole

2-b

3-b

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