Palpitation case 4

Palpitation case 4

A 55-year-old man with a 30-year history of alcohol abuse is brought into the emergency department with palpitations and chest discomfort. His temperature is 37.1 C (98.8 F), blood pressure is 98/56 mm Hg, pulse is 130/min, and respirations are 26/min. Cardiac examination reveals tachycardia with a regular rhythm. An electrocardiogram reveals wide, monomorphic QRS complexes and P waves occurring independently of the QRS complexes.

Q1

What general classification of arrhythmia does this patient have?
/ A. Atrial fibrillation
/ B. Atrial flutter
/ C. Ventricular arrhythmia
/ D. 1st degree atrioventricular block
/ E. 2nd degree atrioventricular block

Q2

Which of the following is the actual cardiac rhythm?
/ A. Multifocal atrial tachycardia
/ B. Normal sinus rhythm
/ C. Sinus tachycardia
/ D. Ventricular fibrillation
/ E. Ventricular tachycardia

Q3

After cardioversion, the patient is treated with esmoloI. Which of the following is the mechanism of action of esmoloI?
/ A. Calcium channel blockade
/ B. CIass 1B sodium channel blockade
/ C. Nonselective beta receptor blockade
/ D. Potassium channel blockade
/ E. Selective beta-1 receptor blockade

Q4

The physician also starts the patient on bumetanide. Which of the following is bumetanide's mechanism of action?
/ A. Angiotensin converting enzyme inhibitor
/ B. Carbonic anhydrase inhibitor
/ C. Loop diuretic
/ D. Potassium sparing diuretic
/ E. Thiazide diuretic

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Palpitation case 4 answers

A1
The correct answer is C. Ventricular arrhythmias occur when the electrical impulse is generated in the ventricles. The presence of dissociative P waves also indicates that the impulse is originating 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.
Atrial fibrillation (choice A) is characterized by irregularly irregular QRS complexes. Furthermore, there is an irregular undulation of the baseline and an absence of P waves, which would indicate that the atria are not contracting in an organized manner.
Atrial flutter (choice B) is characterized by a rapid atrial rate between 240 to 400 beats per minute. It is often seen as a sawtooth 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.
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 1st degree atrioventricular block (choice D), all electrical impulses are conducted with a delay. In 2nd degree atrioventricular block (choice E), only some of the impulses are conducted, and if they are conducted, they can be conducted with a delay.


A2

The correct answer is E. Ventricular tachycardia is usually a result of a reentrant pathway in the cardiac conduction system. It is defined as at least 3 consecutive QRS complexes originating from the ventricles and occurring at a rapid rate (over 100 beats per minute).
Multifocal atrial tachycardia (choice A) is an atrial arrhythmia characterized by different P wave shapes with varying PR intervals. It is associated with severe underlying lung disease.
Normal sinus rhythm (choice B) 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. In ventricular tachycardia, the P waves are dissociated from the QRS complex.
Sinus tachycardia (choice C) 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.
Ventricular fibrillation (choice D) occurs when the ventricles contract in an unorganized manner. There are no clearly formed QRS complexes or T waves. The patient is in cardiac arrest and does not have a pulse.


A3

The correct answer is E. Esmolol selectively antagonizes beta-1 receptors. Other selective beta-1 receptor blockers include metoprolol and atenolol. Nonselective beta receptor blockers (choice C) include propanolol, timolol, labetalol, and nadolol. Nonselective beta receptor blockers block beta-1 and beta-2 receptors relatively equally.
Calcium channel blockers (choice A) 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 B) 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.
Potassium channel blockers (choice D) act to prolong the action potential in phase 3. They include amiodarone, bretylium, and sotalol.


A4

The correct answer is C. Bumetanide is a loop diuretic. It inhibits the sodium, potassium, chloride cotransporter in the thick ascending limb of the loop of Henle.
Angiotensin converting enzyme inhibitors (choice A) include benazepril, captopril, fosinopril, and lisinopril. They interfere with the conversion of angiotensin I to angiotensin II.
Carbonic anhydrase inhibitors (choice B), such as acetazolamide, act in the proximal convoluted tubule. They cause a self-limited sodium bicarbonate diuresis. They are used to alkalinize the urine, and for the treatment of metabolic alkalosis and glaucoma.
Potassium-sparing diuretics (choice D) such as spironolactone, triamterene, and amiloride inhibit the action of aldosterone. They are used in the treatment of hyperaldosteronism and potassium depletion.
Thiazide diuretics (choice E), such as hydrochlorothiazide, inhibit sodium chloride reabsorption in the early distal tubule. They are used in the treatment of hypertension, congestive heart failure, and to inhibit renal calcium stone formation.