The client's ECG reveals tachycardia with a heart rate of 170 beats/min that was initiated after a premature atrial contraction. This rhythm resolved spontaneously without treatment.
What is the nurse's interpretation of this finding?
Paroxysmal supraventricular tachycardia (PSVT).
Ventricular fibrillation.
Rapid atrial flutter.
Ventricular tachycardia.
The Correct Answer is A
Choice A rationale
Paroxysmal supraventricular tachycardia (PSVT) is characterized by a sudden onset and termination of a rapid heart rate, often triggered by a premature atrial contraction (PAC). The heart rate typically ranges from 150 to 250 beats/min. Because the rhythm resolved spontaneously without medical intervention, it fits the definition of "paroxysmal.”. The mechanism involves a re-entry circuit in the conduction system, leading to a rapid, regular rhythm that originates above the ventricles, often seen in otherwise healthy individuals.
Choice B rationale
Ventricular fibrillation is a chaotic, lethal cardiac rhythm characterized by a lack of discernible P waves, QRS complexes, or T waves. The ventricles merely quiver, resulting in no effective cardiac output or pulse. It does not resolve spontaneously and requires immediate defibrillation and cardiopulmonary resuscitation to prevent death. A heart rate of 170 beats/min with a history of PACs and spontaneous resolution is inconsistent with the disorganized electrical activity seen in ventricular fibrillation.
Choice C rationale
Atrial flutter is characterized by a "sawtooth" pattern of F-waves on the ECG, usually with a regular atrial rate of 250 to 350 beats/min and a varying ventricular response. While it can cause a heart rate of 170 beats/min, it is less likely to be triggered by a single PAC and resolve spontaneously in a paroxysmal manner compared to PSVT. Atrial flutter typically requires pharmacological intervention or cardioversion to return the patient to a normal sinus rhythm.
Choice D rationale
Ventricular tachycardia (VT) originates in the ventricles and is characterized by wide, bizarre QRS complexes (usually >0.12 seconds) and a rate typically between 100 and 250 beats/min. While VT can be paroxysmal, it is usually triggered by premature ventricular contractions (PVCs) rather than premature atrial contractions (PACs). The clinical description of the rhythm being initiated by a PAC strongly points toward a supraventricular origin rather than a ventricular one, making VT less likely.
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Related Questions
Correct Answer is C
Explanation
Choice A rationale
Thrombolytic agents are typically administered intravenously in the early stages of a myocardial infarction to dissolve existing clots. While angiography identifies the location of an obstruction, the primary purpose of a percutaneous coronary intervention is mechanical revascularization rather than pharmacological lysis. Thrombolytics carry a high risk of systemic bleeding, whereas PCI focuses on physical restoration of blood flow through stenting or balloon angioplasty directly at the site of the identified lesion.
Choice B rationale
Structural defects in the heart chambers, such as septal holes or valvular dysfunction, are primarily evaluated using echocardiography or transesophageal ultrasound. These non-invasive imaging techniques provide detailed views of myocardial wall motion and chamber integrity. While angiography can show some chamber volume, its specific clinical indication is the assessment of the coronary arterial tree. PCI is not used to repair structural chamber defects, which usually require surgical intervention or specialized percutaneous closures.
Choice C rationale
Coronary angiography uses radiopaque contrast dye to visualize the internal lumen of the coronary arteries, identifying specific areas of narrowing or complete blockage. Once an obstruction is found, percutaneous coronary intervention involves the use of a balloon-tipped catheter to physically dilate the vessel. This process, often followed by stent placement, restores oxygenated blood flow to the myocardium. It is the gold standard for treating acute coronary syndromes and chronic stable angina involving significant stenosis.
Choice D rationale
The measurement of blood pumped with each contraction, known as the ejection fraction, is generally assessed via echocardiography or multigated acquisition scans. While a ventriculogram performed during cardiac catheterization can estimate this volume, it is not the primary purpose of a scheduled angiography and PCI. The goal of the procedure described is therapeutic intervention for arterial disease. Normal ejection fraction ranges from 55.
Correct Answer is A
Explanation
Choice A rationale
Adenosine is the first-line pharmacological treatment for stable, symptomatic supraventricular tachycardia (SVT). It works by briefly slowing or completely blocking conduction through the atrioventricular (AV) node. This action can interrupt re-entry circuits and restore a normal sinus rhythm. Due to its extremely short half-life of less than 10 seconds, it must be administered as a rapid intravenous bolus followed by a quick saline flush to ensure the medication reaches the heart effectively.
Choice B rationale
Cardizem, also known as diltiazem, is a calcium channel blocker used primarily for rate control in atrial fibrillation or atrial flutter. While it can be used for SVT if adenosine is ineffective, it is not typically the first drug of choice for the immediate conversion of an acute, sustained SVT. It works by inhibiting the influx of calcium ions during membrane depolarization of cardiac muscle, which slows the ventricular response but doesn't always terminate the arrhythmia.
Choice C rationale
Lidocaine is a Class IB antiarrhythmic primarily used to treat ventricular arrhythmias, such as ventricular tachycardia or frequent premature ventricular contractions. It acts by suppressing the automaticity of the ventricular conduction system and increasing the electrical stimulation threshold of the ventricle. It has virtually no effect on the atrial tissue or the AV node, making it an inappropriate and ineffective choice for treating supraventricular tachycardia, which originates above the ventricles.
Choice D rationale
Atropine is an anticholinergic medication used to treat symptomatic bradycardia by blocking the effects of the vagus nerve on the heart, thereby increasing the heart rate. Administering atropine to a patient who already has a sustained tachycardia would be extremely detrimental, as it would further accelerate the heart rate and increase myocardial oxygen demand. Its mechanism of action is the exact opposite of what is required to treat a fast, supraventricular rhythm.
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