A nurse is caring for a patient with heart failure who is receiving a combination of medications, including an ACE inhibitor and a diuretic.
The nurse should monitor for which of the following potential complications?

Choice A rationale

Sinus tachycardia is defined by a heart rate exceeding 100 beats per minute, originating from the sinoatrial node. The rhythm remains regular because the electrical impulses follow the normal conduction pathway through the atria and ventricles. Each QRS complex is preceded by a visible P wave, and the PR interval remains within the normal range of 0.12 to 0.20 seconds. This rhythm is often a physiological response to stress, fever, exercise, or pain.

Choice B rationale

A heart rate between 60 and 100 beats per minute with a regular rhythm defines normal sinus rhythm. In this state, the sinoatrial node fires at a standard physiological pace, and the electrical conduction through the heart is unimpeded. Because sinus tachycardia specifically refers to a rate that is faster than this normal range, this choice does not accurately describe the wave pattern in question. It represents a healthy cardiac electrical state rather than a tachycardic one.

Choice C rationale

An irregular rhythm with changing P wave morphology is characteristic of rhythms like wandering atrial pacemaker or multifocal atrial tachycardia. These conditions involve multiple ectopic foci within the atria competing for dominance, rather than a single impulse from the sinoatrial node. In true sinus tachycardia, the P waves should look identical to one another because they are all generated from the same location. Therefore, this description is inconsistent with the diagnostic criteria for sinus tachycardia.

Choice D rationale

A rapid rate without visible P waves and narrow QRS complexes is typical of supraventricular tachycardia or atrial fibrillation, depending on the regularity of the rhythm. In sinus tachycardia, the P wave must be present and clearly associated with the QRS complex because the rhythm originates from the sinus node. The absence of P waves suggests that the rhythm is originating from a different part of the atrium or the atrioventricular junction, which is incorrect.

Choice A rationale

Administering nitroglycerin is a standard treatment for chest pain because it induces vasodilation of the coronary arteries. However, prioritizing it over oxygen in a patient with an oxygen saturation of 89 percent is incorrect. Nitroglycerin can significantly lower blood pressure, and it should only be administered after assessing hemodynamic stability. In this clinical scenario, addressing the documented hypoxemia takes precedence to ensure myocardial tissue receives adequate oxygenation to prevent further ischemic damage.

Choice B rationale

Supplemental oxygen is the priority because the patient is hypoxemic, with a saturation below the normal range of 95 to 100 percent. Oxygen therapy increases the partial pressure of oxygen in the blood, enhancing delivery to the myocardium. Correcting hypoxemia reduces the workload on the heart and limits the size of the infarction. Current guidelines emphasize maintaining oxygen saturation at or above 94 percent to optimize cellular respiration and prevent systemic metabolic acidosis.

Choice C rationale

The supine position is not ideal for a patient experiencing chest pain and respiratory distress because it increases venous return and cardiac preload, potentially worsening pulmonary congestion. Positioning the patient in semi-Fowler or high-Fowler position is usually preferred to facilitate lung expansion. While morphine is used for pain that is unresponsive to nitrates, it is not the first priority. Oxygenation must be addressed immediately to mitigate the underlying cause of the myocardial hypoxia.

Choice D rationale

Thrombolytic therapy is a critical intervention for ST-segment elevation myocardial infarction when percutaneous intervention is unavailable, but it is never initiated before establishing vascular access and confirming the diagnosis via a 12-lead ECG. Furthermore, safety screening for contraindications like recent surgery or bleeding disorders is mandatory. Starting this treatment without basic stabilization, such as oxygen administration for a desaturating patient, violates the primary assessment sequence of airway, breathing, and circulation.