Provided is an ECG image of sinus bradycardia.
Identify the wave pattern and describe its characteristics.
The wave pattern shows a normal sinus rhythm with a heart rate of less than 60 beats per minute.
The wave pattern shows an absence of P waves and a heart rate of 40 beats per minute.
The wave pattern shows a prolonged PR interval greater than 0.20 seconds with a slow rate.
The wave pattern shows a regular rhythm with a heart rate between 60 and 100 beats per minute.
The Correct Answer is A
Choice A rationale
Sinus bradycardia is defined by a heart rate of less than 60 beats per minute originating from the sinoatrial node. On an ECG, this rhythm must demonstrate all the hallmarks of a normal sinus rhythm, including a P wave preceding every QRS complex, a constant PR interval between 0.12 and 0.20 seconds, and a regular R to R interval. The only abnormality is the slow rate. It can be physiological in athletes or a result of vagal stimulation.
Choice B rationale
An absence of P waves combined with a slow heart rate of 40 beats per minute typically indicates a junctional escape rhythm. In this scenario, the sinoatrial node fails to fire, and the atrioventricular node takes over as the primary pacemaker. Because the atria are not depolarized from the top down, P waves are either absent, inverted, or hidden within the QRS complex. This is distinct from sinus bradycardia, where the sinoatrial node is still functioning as the pacemaker.
Choice C rationale
A prolonged PR interval greater than 0.20 seconds is the defining characteristic of a first-degree atrioventricular block. While this condition can occur alongside sinus bradycardia, the prolongation of the PR interval indicates a delay in conduction through the atrioventricular node rather than a slow discharge rate from the sinoatrial node itself. Simple sinus bradycardia maintains a normal PR interval. Lab values for cardiac output may be monitored if the rate becomes too slow to maintain tissue perfusion.
Choice D rationale
A regular rhythm with a heart rate between 60 and 100 beats per minute is the definition of normal sinus rhythm. In this range, the sinoatrial node is firing at an appropriate physiological frequency for a resting adult. All ECG components, including P waves, QRS complexes, and T waves, are present and occur at regular intervals. Sinus bradycardia specifically requires the rate to drop below the 60 beats per minute threshold while maintaining the other characteristics of sinus rhythm.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Choice A rationale
Reducing oxygenation would be detrimental to a client with heart failure. The physiological goal is actually to optimize oxygen delivery to the tissues to compensate for the heart's inability to pump effectively. Lowering oxygen levels would exacerbate tissue hypoxia, increase respiratory distress, and worsen the overall clinical status. Management strategies usually involve supplemental oxygen and medications to improve gas exchange rather than reducing the availability of oxygen to the body's vital organs.
Choice B rationale
The primary goal in heart failure management is to reduce the cardiac workload to improve the heart's efficiency. By reducing preload through diuretics and reducing afterload through vasodilators like ACE inhibitors, the heart does not have to work as hard to eject blood. Lifestyle changes and rest also decrease systemic metabolic demands. Reducing the strain on the failing myocardium helps prevent further remodeling, relieves symptoms like dyspnea, and improves the overall quality of life.
Choice C rationale
Reducing cardiac output is the opposite of what is desired in heart failure management. Heart failure is defined by a cardiac output that is insufficient to meet the metabolic needs of the body. Treatment aims to optimize and maintain an adequate cardiac output through various pharmacological and non-pharmacological means. Lowering the output further would lead to organ failure, profound hypotension, and death. Every intervention is designed to make the output more effective and sustainable.
Choice D rationale
Pulmonary efficacy refers to the ability of the lungs to oxygenate blood and remove carbon dioxide. In heart failure, pulmonary efficacy is often compromised by fluid congestion. The goal of medical management is to improve pulmonary efficacy, not reduce it. By clearing fluid from the alveoli using diuretics and improving forward flow, the nurse and physician aim to enhance gas exchange. Reducing pulmonary efficiency would lead to respiratory failure and severe acid-base imbalances.
Correct Answer is A
Explanation
Choice A rationale
Ventricular fibrillation represents the most disorganized and lethal cardiac rhythm because it involves multiple re-entrant circuits in the ventricles. There is no coordinated depolarization of myocardial tissue, which results in the absence of mechanical contraction and cardiac output. Since there is no organized atrial or ventricular depolarization, the ECG lacks P waves, QRS complexes, and T waves. The tracing appears as a wavy, undulating line with varying amplitude and frequency known as coarse or fine fibrillation.
Choice B rationale
A regular rhythm with a rate exceeding 150 beats per minute and widened QRS complexes greater than 0.12 seconds typically describes ventricular tachycardia. This rhythm originates from an ectopic focus in the ventricles and can lead to hemodynamic instability, but it maintains a degree of organization that ventricular fibrillation lacks. While it is serious, the electrical signals are still forming distinct complexes, unlike the chaotic oscillations seen in fibrillation where the muscle fibers simply quiver without pumping blood.
Choice C rationale
A saw-tooth appearance on an ECG is the hallmark of atrial flutter. This pattern is caused by a macro-re-entrant circuit in the atria, usually around the tricuspid valve, occurring at a rate of 250 to 350 beats per minute. This results in regular "F" waves. The ventricular response depends on the conduction ratio through the atrioventricular node. This is a supraventricular tachycardia and is distinct from the chaotic ventricular activity that defines the life-threatening state of ventricular fibrillation.
Choice D rationale
Normal sinus rhythm with occasional premature ventricular contractions describes a baseline rhythm originating from the sinoatrial node with a rate of 60 to 100 beats per minute. The occasional premature ventricular contractions are early QRS complexes that are wide and bizarre in shape because they originate from the ventricles rather than the normal conduction system. This is a common finding and does not represent the total loss of organized electrical activity and cardiac output seen in fibrillation.
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