A 65-year-old man presents with sudden-onset palpitations and dizziness. His pulse is 180/min and regular. ECG shows a regular narrow-complex tachycardia at 180/min with no clearly visible P waves. Vagal maneuvers fail. He is hemodynamically stable. What is the most appropriate next treatment?

A 42-year-old woman develops sudden dyspnea and pleuritic chest pain 5 days after knee replacement surgery. Pulse is 118/min, respiratory rate 28/min and oxygen saturation is 91%. Chest examination is relatively normal. Which ECG finding may be seen in this patient?

A 25-year-old woman presents with jaundice, confusion and bleeding from the gums. She has markedly elevated AST/ALT and an INR of 3.2. She had no previous history of liver disease. Which finding best defines acute liver failure?

A 32-year-old woman presents with weight loss, tremor, heat intolerance and palpitations. Examination reveals diffuse thyroid enlargement and bilateral eye prominence. Laboratory investigations show suppressed TSH and markedly elevated free T4. Which antibody is most specific for the underlying condition?

A 45-year-old man develops fever, severe headache, periorbital swelling and ophthalmoplegia following an untreated facial infection. Examination shows involvement of cranial nerves III, IV, V1, V2 and VI. Which venous sinus is most likely involved?

The image shows multiple well-demarcated erythematous plaques covered by thick, silvery-white scales, predominantly over the extensor surfaces of the elbows and knees. Small pinpoint bleeding occurs when the scale is gently removed. Which is the most likely diagnosis?

A 30-year-old man is brought to the emergency department after a road traffic accident. He is pale, cold and clammy. BP is 80/50 mmHg, pulse 130/min and JVP is not elevated. FAST examination shows free fluid in the abdomen. What is the most likely type of shock?

A 28-year-old woman with 7 weeks of amenorrhea presents with lower abdominal pain and vaginal spotting. β-hCG is positive. Transvaginal ultrasound shows no intrauterine gestational sac, while a left adnexal mass is seen. She suddenly develops severe abdominal pain, hypotension and tachycardia. What is the most appropriate management?

A 2-year-old child develops sudden severe cyanosis and rapid breathing while crying. The child instinctively squats after the episode and gradually improves. Which mechanism best explains the improvement?