A 75-year-old man presents to the emergency department after an episode of syncope while walking outside with his wife. His wife states that he suddenly appeared pale and collapsed to the ground. She says he remained unconscious for 1 minute. He says he noticed a fluttering in his chest and excessive sweating before the episode. He has type 2 diabetes mellitus, essential hypertension, and chronic stable angina. He has not started any new medications in the past few months. Vital signs reveal: temperature 37.0°C (98.6°F), blood pressure 135/72 mm Hg, and pulse 72/min. Physical examination is unremarkable. ECG shows an old bifascicular block. Echocardiogram and 24-hour Holter monitoring are normal. Which of the following is the best next step in the evaluation of this patient's condition?
ACardiac enzymes
BContinuous loop recorder
CValsalva maneuver
DElectroencephalography (EEG)
ETilt-table test
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
A researcher measures action potential propagation velocity in various regions of the heart in a 42-year-old Caucasian female. Which of the following set of measurements corresponds to the velocities found in the atrial muscle, AV Node, Purkinje system, and ventricular muscle, respectively?
A0.05 m/s, 1.1 m/s, 2.2 m/s, 3.3 m/s
B2.2 m/s, 0.3 m/s, 0.05 m/s, 1.1 m/s
C0.3 m/s, 2.2 m/s, 0.05 m/s, 1.1 m/s
D0.5 m/s, 1.1 m/s, 2.2 m/s, 3 m/s
E1.1 m/s, 0.05 m/s, 2.2 m/s, 0.3 m/s
+ 7 more in the PDF
Browse all chapters