A mutation prevents pyruvate from entering mitochondria but does not directly affect glycolysis. Predict what happens to: a. Glycolysisb. Pyruvate concentrationc. Citric acid cycle activityd. Mitochondrial NADH/FADH₂ productione. Oxygen consumptionf. ATP production

A 14-year-old girl with a history of congenital complete heart block underwent permanent pacemaker placement at age 8. She presents to clinic after experiencing several episodes of dizziness and near-syncope during the past week. Her heart rate is 42 beats/min. An ECG demonstrates sinus rhythm with pacing spikes intermittently present but not followed by a QRS complex. The pacemaker battery was replaced 6 months ago. Which of the following best explains this patient’s symptoms?

A 7-year-old child undergoes diagnostic cardiac catheterization with femoral arterial access to evaluate pulmonary hypertension. Four hours after the procedure, the bedside nurse notes that the patient’s right foot is cool compared with the left. On examination, the right dorsalis pedis pulse is not palpable but can be detected by Doppler. Capillary refill of the right foot is 4 seconds. The catheterization site is soft without evidence of bleeding or hematoma. Which of the following is the most appropriate next step in management?

A 15-year-old male is brought to the emergency department after collapsing while helping his family spray insecticide on a farm. On arrival, he is confused and diaphoretic. Vital signs are: HR: 42 beats/min BP: 78/40 mmHg RR: 28 breaths/min SpO₂: 91% Physical examination reveals miosis, excessive salivation, diffuse wheezing, and increased lacrimation. An ECG demonstrates sinus bradycardia with first-degree AV block. After stabilization of the airway, which of the following best explains the patient’s cardiovascular findings and guides initial treatment?

A 15-year-old female presents to clinic after an episode of loss of consciousness during choir practice. She reports feeling warm, nauseated, and lightheaded while standing for a prolonged period before briefly losing consciousness. Witnesses report that she was unconscious for approximately 10 seconds and recovered quickly without confusion. Her physical examination and ECG are normal. Which of the following features in this patient’s history most strongly supports a diagnosis of vasovagal syncope rather than a cardiac cause of syncope?

A full-term newborn develops cyanosis shortly after birth. Oxygen saturation is 78% despite administration of supplemental oxygen. Physical examination reveals a single second heart sound and a grade II/VI holosystolic murmur at the left lower sternal border. Chest radiography shows decreased pulmonary vascular markings. Echocardiography demonstrates absence of the tricuspid valve, a hypoplastic right ventricle, a large atrial septal defect, and a small ventricular septal defect. Which of the following is the most appropriate immediate management?

A 14-year-old girl underwent orthotopic heart transplantation 8 months ago for dilated cardiomyopathy. She presents to clinic with 1 week of fatigue, decreased exercise tolerance, and mild shortness of breath. Her vital signs are notable for a heart rate of 105 beats/min and blood pressure of 92/58 mmHg. Physical examination reveals a new gallop rhythm and mild hepatomegaly. Echocardiography demonstrates a decrease in left ventricular systolic function compared with her study from 3 months ago. Which of the following is the most appropriate next step to establish the diagnosis?

A nurse is teaching a patient about antibiotic therapy. The patient asks why some antibiotics must be taken three times a day while others are prescribed twice a day. The nurse explains that the frequency of antibiotic dosing is primarily determined by which factor?

A post-Fontan patient’s ECG shows a regular atrial rate of approximately 300 bpm in the inferior leads and a ventricular rate of 150 bpm. What is the most likely diagnosis?

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