An ECG from an 8-year-old male with neurosensory deafness and a family history of sudden cardiac arrest demonstrates QT-interval prolongation. Which of the following is this patient most at risk of developing?
AHypertrophic cardiac myopathy
BCardiac tamponade
CEssential hypertension
DTorsades de pointes
EFirst degree atrioventricular block
A 21-year-old man presents to a physician with repeated episodes of syncope and dizziness over the last month. On physical examination, his pulse is 64/min while all other vital signs are normal. His 24-hour ECG monitoring suggests a diagnosis of sinus node dysfunction. His detailed genetic evaluation shows that he carries a copy of a mutated gene “X” that codes for an ion channel, which is the most important ion channel underlying the automaticity of the sinoatrial node. This is the first ion channel to be activated immediately after hyperpolarization. Which of the following ion channels does the gene “X” code for?
AFast delayed rectifier (IKr) voltage-dependent K+ channels
BStretch-activated cationic channels
CL-type voltage-dependent calcium channels
DT-type voltage-dependent calcium channels
EHCN-channels
Cardiac muscle serves many necessary functions, leading to a specific structure that serves these functions. The structure highlighted is an important histology component of cardiac muscle. What would be the outcome if this structure diffusely failed to function?
AFailure of potassium channels to appropriately open to repolarize the cell
BFailure of propagation of the action potential from the conduction system
CIneffective excitation-contraction coupling due to insufficient calcium ions
DInappropriate formation of cardiac valve leaflets
EOutflow tract obstruction
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