Palpitation case 2

Palpitation case 2

A 54-year-old man presents to the emergency department with palpitations and shortness of breath. His temperature is 37 C (98.6 F), blood pressure is 102/68 mm Hg, pulse is 130/min, and respirations are 26/min. His jugular venous pressure is elevated. Cardiac examination reveals an irregular rate and rhythm, with a low-pitched diastolic murmur, preceded by an opening snap, heard best over the apex. Lung examination reveals bibasilar crackles. There is also 2+ bilateral lower extremity edema. An electrocardiogram reveals an irregular undulation of the baseline, an absence of P waves, and narrow QRS complexes that are irregularly irregular.

Q1

Which of the following is the most likely preliminary diagnosis?
/ A. Atrial arrhythmia
/ B. First degree atrioventricular block
/ C. Normal sinus rhythm
/ D. Third degree atrioventricular block
/ E. Ventricular arrhythmia

Q2

Which of the following best describes the patient's cardiac rhythm?
/ A. Atrial fibrillation
/ B. Atrial flutter
/ C. Multifocal atrial tachycardia
/ D. Sinus bradycardia
/ E. Sinus tachycardia


Q3

Which of the following is the underlying cause of this patient's abnormal rhythm?
/ A. Aortic stenosis
/ B. Hyperthyroidism
/ C. Hypothyroidism
/ D. Mitral stenosis
/ E. Sepsis


Q4

The patient is treated with amiodarone to control his cardiac rhythm. Which of the following is the mechanism of action of this medication?
/ A. Beta adrenergic receptor blocker
/ B. Calcium channel blocker
/ C. CIass 1B sodium channel blocker
/ D. CIass 1C sodium channel blocker
/ E. Potassium channel blocker


Q 5

Which of the following is a known adverse reaction associated with amiodarone?
/ A. Diabetes mellitus
/ B. Gastrointestinal bleeding
/ C. Hallucinations
/ D. Pulmonary disease
/ E. Renal failure


Q6

Because the patient is at risk for thrombosis, he is anticoagulated with warfarin. Which of the following is the mechanism of action of warfarin?
/ A. Activation of antithrombin lll
/ B. Fibrinolysis
/ C. Inhibition of antithrombin lll
/ D. Inhibition of synthesis of clotting factors lI, VII, IX, and X
/ E. Inhibition of synthesis of clotting factors XI and XII

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Palpitation case 2 answers

A1
The correct answer is A. The presence of narrow QRS complexes indicates the rhythm is from a supraventricular source and conducted to the ventricles through the atrioventricular conduction system. In this case, it is from the atria, and therefore an atrial arrhythmia.
Atrioventricular block refers to an abnormality in the electrical conduction between the atria and the ventricles. The degree of the block refers to the severity of the conduction. In first degree atrioventricular block (choice B), all electrical impulses are conducted with a delay. In third degree atrioventricular block (choice D), there is no conduction of the electrical impulse and complete heart block.
Normal sinus rhythm (choice C) is a normal rhythm. It is produced by electrical impulses formed in the sinoatrial node. In the electrocardiogram, these impulses are seen as P waves followed by narrow QRS complexes.
Ventricular arrhythmias (choice E) occur when the electrical impulse is generated in the ventricles. Because the conduction of the impulse polarizes the ventricles at different times, the QRS complex is seen as widened on the electrocardiogram


A2
The correct answer is A. The irregular undulation of the baseline and the absence of P waves indicate that the atria are not contracting in an organized manner. This is known as atrial fibrillation. Atrial fibrillation is also characterized by irregularly irregular QRS complexes.
Atrial flutter (choice B) is characterized by a rapid atrial rate between 240 to 400 beats per minute. It is often seen as a saw tooth pattern of F waves on the electrocardiogram. Because of the refractoriness of the atrioventricular node, the flutter waves are not generally all transmitted through to the ventricles. The conduction of these waves can vary from 2:1 conduction or higher.
Multifocal atrial tachycardia (choice C) is an atrial arrhythmia characterized by different P wave shapes with varying PR intervals. It is associated with severe underlying lung disease.
Sinus bradycardia (choice D) is a slow sinus rhythm of less than 60 beats per minute. It is characterized by QRS complexes that follow each P wave.
Sinus tachycardia (choice E) is a rapid sinus rate of greater than 100 beats per minute. A QRS complex also follows each P wave. It is generally a cardiac response to pain, fever, infection, vigorous exercise, shock, dehydration, anxiety, heart failure, or anemia.


A3

The correct answer is D. The low-pitched diastolic murmur, which is preceded by an opening snap, is diagnostic of mitral stenosis. Mitral stenosis is most often due to rheumatic heart disease, and it often leads to atrial arrhythmias, especially atrial fibrillation.
Aortic stenosis (choice A) is characterized by a systolic crescendo-decrescendo murmur best heard over the second intercostal space along the right sternal border. It is generally not associated with atrial fibrillation.
Hyperthyroidism (choice B) can also be associated with atrial fibrillation, but in this case, the patient has no symptoms suggestive of hyperthyroidism. These symptoms include heat intolerance, hyperdefecation, tremulousness, hair loss, and excessive sweating.
Hypothyroidism (choice C) is not associated with atrial fibrillation. It is associated with sinus bradycardia.
Sepsis (choice E) can be associated with atrial fibrillation, but it occurs in the setting of a disseminated infection that causes vascular compromise.


A4
The correct answer is E. Amiodarone is an antiarrhythmic agent classified as a potassium channel blocker. It acts to prolong the action potential in phase 3.
Beta adrenergic receptor blockers (choice A) include propranolol, esmolol, timolol, and metoprolol. As antiarrhythmic agents, they decrease cAMP levels, decrease calcium currents, and suppress abnormal pacemakers.
Calcium channel blockers (choice B) include verapamil, diltiazem, and bepridil. They decrease conduction velocity and increase the PR interval. They are used in the prevention of nodal arrhythmias.
Class 1B sodium channel blockers (choice C) include lidocaine, mexiletine, and tocainide. They act to depress the action potential and stabilize the cell membrane. They are used in acute ventricular arrhythmias and digitalis-induced arrhythmias.
Class 1C sodium channel blockers (choice D) include flecainide, encainide, and propafenone. They depress the action potential at phase 0 and stabilize cell membranes. They are used as a last resort in refractory tachyarrhythmias due to their side effects.


A5

The correct answer is D. Amiodarone is associated with many adverse reactions, including pulmonary disease. Patients can develop an alveolitis or, in more serious cases, pulmonary fibrosis.
Diabetes mellitus (choice A) is not associated with amiodarone use. Amiodarone can cause endocrine abnormalities which affect the thyroid gland, resulting in hypo- or hyperthyroidism.
Gastrointestinal bleeding (choice B) is not associated with amiodarone use. Amiodarone can cause nausea, vomiting, or abdominal discomfort, but it is not associated with bleeding.
Hallucinations (choice C) are not associated with amiodarone use. Digoxin, which is also used to treat atrial fibrillation, is associated with hallucinations and delirium.
Renal failure (choice E) is not associated with amiodarone. Amiodarone is associated with elevations in liver enzymes, or in more severe cases, it can cause hepatotoxicity.


A6

The correct answer is D. Warfarin inhibits vitamin K-dependent coagulation factor synthesis. These include factors II, VII, IX, and X, as well as protein C and S. Warfarin acts to increase the prothrombin time. Factors XI and XII are not vitamin K-dependent factors. Therefore, warfarin does not inhibit their synthesis (choice E).
Activation of antithrombin III (choice A) is a mechanism of action used by heparin. It acts to prolong the partial thromboplastin time.
Fibrinolysis (choice B) is a mechanism of action used by thrombolytic agents such as streptokinase and urokinase. These agents convert plasminogen to plasmin, promoting fibrinolysis.
Inhibition of antithrombin III (choice C) would promote clot formation. The goal of anticoagulation is to prevent clot formation.