The arrhythmia that results in cardiac arrest followed by death in the absence of treatment and therefore considered most serious is:
1. Tachycardia
2. Sinus bradycardia
3. Atrial flutter
4. Ventricular fibrillation

Assertion: Coronary arteries are especially vulnerable to obstruction by atherosclerotic plaques or thrombus.
Reason: Coronary arteries supply oxygenated blood to the muscles of the heart itself.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Severe dyspnea due to pulmonary edema will be caused most likely by:
1. cardiogenic shock
2. anaphylactic shock
3. right-sided congestive heart failure
4. left-sided congestive heart failure