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Zorluk: ZorCardiovascular System

A 6565-year-old man is brought to the emergency department by ambulance due to severe, heavy chest pressure, diaphoresis, and worsening shortness of breath that began 9090 minutes ago. His medical history is significant for chronic obstructive pulmonary disease (COPD), hyperlipidemia, and hypothyroidism. His home medications include a statin, an inhaled fluticasone-salmeterol diskus, and oral levothyroxine.

Upon arrival, his temperature is 37.0∘C37.0^\circ\text{C} (98.6∘F98.6^\circ\text{F}), blood pressure is 86/52 mm Hg86/52\text{ mm Hg}, pulse is 108/min108/\text{min}, and respirations are 24/min24/\text{min}. Pulse oximetry is 92%92\% on room air.

Physical examination reveals prominent jugular venous distention while the patient is sitting at a 45∘45^\circ angle. Lung auscultation shows prolonged expiration with mild, scattered wheezes bilaterally, but the lungs are clear of crackles. Cardiac examination reveals tachycardia with a regular rhythm; no murmurs or gallops are appreciated. The liver edge is palpable 4 cm4\text{ cm} below the right costal margin.

Laboratory testing shows:
- Troponin I: 2.4 ng/mL2.4\text{ ng/mL} (Normal <0.04 ng/mL<0.04\text{ ng/mL})
- TSH: 5.5 \muU/mL5.5\text{ \mu U/mL} (Normal 0.4−4.0 \muU/mL0.4 - 4.0\text{ \mu U/mL})
- Free T4: 1.1 ng/dL1.1\text{ ng/dL} (Normal 0.8−1.8 ng/dL0.8 - 1.8\text{ ng/dL})

Arterial blood gas on room air reveals a pH of 7.367.36, pCO2\text{pCO}_2 of 48 mm Hg48\text{ mm Hg}, and pO2\text{pO}_2 of 65 mm Hg65\text{ mm Hg}.

A 1212-lead electrocardiogram demonstrates 3-mm3\text{-mm} ST-segment elevations in leads II, III, and aVF, with reciprocal ST-segment depressions in leads I and aVL.

The patient is given chewable aspirin and an intravenous fluid bolus. Which of the following interventions is most strongly contraindicated in the immediate management of this patient's condition?

  1. Administration of sublingual nitroglycerinCevap
  2. B
    Administration of inhaled albuterol and systemic corticosteroids
  3. C
    Administration of empiric ceftriaxone and azithromycin
  4. D
    Administration of intravenous sodium bicarbonate
  5. E
    Increasing the daily dose of levothyroxine

Cevap

Administration of sublingual nitroglycerin is strongly contraindicated.
The correct answer is the administration of sublingual nitroglycerin. This patient's presentation of an inferior ST-elevation myocardial infarction (ST elevations in leads II, III, and aVF) accompanied by hypotension, elevated jugular venous pressure, and clear lungs is the classic triad for a right ventricular myocardial infarction (RVMI). The right ventricle is typically supplied by the proximal right coronary artery. When ischemic, the right ventricle loses its contractile function and becomes highly dependent on elevated preload to drive blood into the pulmonary circulation and maintain left ventricular filling. Nitroglycerin is a potent venodilator that decreases venous return (preload). Administering nitroglycerin to a patient with RVMI will cause a drastic drop in cardiac output and can precipitate profound, life-threatening cardiovascular collapse. Therefore, nitrates, as well as diuretics, are strictly contraindicated. The initial treatment for hypotension in RVMI is intravenous fluid resuscitation to optimize right ventricular preload.

Adım Adım Çözüm

1
Analyze the electrocardiogram and cardiac biomarkers.
The ST-segment elevations in the inferior leads (II, III, aVF) coupled with an elevated troponin I confirm an acute inferior ST-elevation myocardial infarction (STEMI).
Identifying the territory of infarction is the first step in determining specific complications and contraindications.
2
Correlate the ECG findings with the patient's physical examination and hemodynamics.
The classic triad of hypotension, clear lungs, and elevated jugular venous pressure in the setting of an inferior STEMI strongly indicates right ventricular myocardial infarction (RVMI).
The right ventricle is supplied by the right coronary artery, which is also the culprit vessel in the majority of inferior STEMIs. Recognizing RV involvement drastically alters hemodynamic management.
3
Determine the physiological impact of proposed interventions on the infarcted right ventricle.
Medications that decrease right ventricular preload, such as nitroglycerin (a venodilator), are strictly contraindicated.
An ischemic right ventricle loses contractility and relies entirely on elevated preload (venous return) to maintain forward stroke volume. Dropping preload leads to severe, precipitous cardiovascular collapse.

Anahtar Kavram

Right ventricular myocardial infarction (RVMI) typically presents with the triad of hypotension, elevated jugular venous pressure, and clear lungs. Because the ischemic right ventricle is highly preload-dependent, venodilators (like nitroglycerin) and diuretics are strictly contraindicated.
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