Editing Medical-Surgical Nursing (section)

=== Coronary Artery Disease and Acute Coronary Syndrome ===

Atherosclerotic plaque narrows the coronary arteries. Stable angina occurs with predictable exertion and is relieved by rest and nitroglycerin. Unstable angina occurs at rest, is new, or is worsening in frequency and severity, and it signals impending infarction. Myocardial infarction occurs when a plaque ruptures and a thrombus occludes the vessel, causing myocardial necrosis.

Classic findings include crushing substernal chest pain that may radiate to the jaw, neck, left arm, or back, along with diaphoresis, nausea, dyspnea, and a sense of impending doom. Women, older adults, and people with diabetes often present atypically with fatigue, epigastric discomfort, shortness of breath alone, or new confusion. Silent infarction is common in diabetes because of autonomic neuropathy.

Diagnostics: a twelve-lead electrocardiogram should be obtained within ten minutes of presentation. ST elevation indicates an ST elevation myocardial infarction requiring emergent reperfusion. Troponin I and T are the most specific cardiac markers; they begin to rise about three to four hours after injury, peak within about twelve to twenty-four hours, and remain elevated for up to ten to fourteen days.

Nursing interventions: keep the patient on bed rest with the head of the bed elevated, apply oxygen if the oxygen saturation is below ninety percent or the patient is dyspneic, obtain intravenous access, and give aspirin to chew, nitroglycerin, and analgesia as ordered while monitoring the cardiac rhythm continuously. Nitroglycerin is withheld if the systolic blood pressure is below ninety mm Hg or has fallen substantially from baseline, and it is absolutely contraindicated within twenty-four to forty-eight hours of a phosphodiesterase type 5 inhibitor such as sildenafil or tadalafil because of the risk of profound hypotension.

Nursing application: the most common cause of death in the first hours after infarction is a lethal dysrhythmia, most often ventricular fibrillation. Continuous rhythm monitoring and immediate availability of a defibrillator are not optional. New premature ventricular contractions, ventricular tachycardia, or a new bundle branch block are reported at once.