Examkin

Soru

Zorluk: OrtaMedical History Evaluation

A 34-year-old woman is evaluated in the emergency department after experiencing palpitations and a near-syncopal episode while resting at home. An electrocardiogram performed upon arrival demonstrates sinus rhythm with a markedly prolonged QTc interval of 530 ms. A previous electrocardiogram from one year ago showed a normal QTc interval of 410 ms. The patient has no known structural heart disease. During the clinical interview, a detailed medical history must be obtained to identify the acquired etiology of her electrocardiographic abnormality. Which of the following historical elements would directly explain her presentation and must be specifically targeted during the interview? (Select all that apply)

  1. A 4-day history of severe nausea, vomiting, and inability to tolerate oral intake.Cevap
  2. Initiation of a 7-day course of oral moxifloxacin for acute rhinosinusitis.Cevap
  3. C
    Recent addition of an over-the-counter cytochrome P450 3A4 (CYP3A4) inducer, such as St. John's wort.
  4. D
    A family history of sudden cardiac death in a paternal grandfather at age 82.
  5. E
    A recent basic metabolic panel showing a high-normal serum calcium level of 10.4 mg/dL.

Cevap

The correct historical elements to identify are a recent history of severe gastrointestinal fluid losses (which leads to hypokalemia and hypomagnesemia) and the recent initiation of moxifloxacin (a known QT-prolonging medication).
Acquired prolongation of the QTc interval is most commonly precipitated by electrolyte derangements or specific pharmacologic agents. A recent history of severe vomiting leads to significant potassium and magnesium depletion; hypokalemia and hypomagnesemia profoundly delay ventricular repolarization, manifesting as a prolonged QTc. Additionally, fluoroquinolones such as moxifloxacin block myocardial potassium channels (specifically the rapidly activating delayed rectifier potassium current via the hERG channel), leading to direct, dose-dependent QTc prolongation.

Adım Adım Çözüm

1
Analyze the electrocardiographic findings and compare them to the patient's baseline.
The patient has new-onset, acquired QTc prolongation (530 ms) compared to a prior normal baseline (410 ms).
Establishing that the QTc prolongation is acquired rather than congenital dictates the direction of the medical history.
2
Identify common physiologic and pharmacologic triggers for acquired QTc prolongation.
Major triggers include electrolyte abnormalities (hypokalemia, hypomagnesemia, hypocalcemia) and QT-prolonging drugs (e.g., fluoroquinolones, macrolides, antipsychotics, antiemetics).
Understanding the pathophysiologic mechanisms of repolarization delay provides a framework for targeted questioning.
3
Evaluate the provided historical options against the known triggers for acquired QTc prolongation.
Severe vomiting causes potassium and magnesium loss. Moxifloxacin directly prolongs the QTc interval. The other options involve incorrect interactions, inappropriate timeline contexts, or opposite physiologic effects.
To select the historical elements that directly explain the patient's presentation and rule out distractors.

Anahtar Kavram

Evaluation of acquired QTc prolongation requires a targeted medical history focusing on recent fluid losses (causing hypokalemia and hypomagnesemia) and a meticulous review of newly initiated QT-prolonging medications (such as fluoroquinolones).
Bu soruyu puanla

Konular

Medical History Evaluation

Bu konudan daha fazla soru