The heart block that causes dropped beats and that is often the result of increased parasympa-thetic ...

(Answer to Q. 1)  ANS: B
Dropped beats are characteristic of second-degree atrioventricular blocks, which consist of Mo-bitz type I and Mobitz type II blocks. These dropped beats are a result of the atrioventricular node's inability to conduct impulses from the sinoatrial node. Sinoatrial blocks are indicated by a sudden loss of P waves. First-degree atrioventricular blocks are indicated by a prolongation of the PR interval. Left bundle branch blocks are indicated by the absence of Q waves in the left limb leads.

(Answer to Q. 2)  ANS: D
When cardiac tissue fed by the left anterior descending and circumflex branches of the left cor-onary artery infarct, Q waves become abnormal most noticeably on the left precordial leads. As a result, the Q waves deflect downward instead of upward because of a lack of counterbalancing electrical forces on the affected side.

(Answer to Q. 3)  ANS: B
Isolating 3 seconds out of the strip shows that there are 4 cardiac cycles in the 3-second period. Multiply 4 by 20. The heart rate is 80 beats/min.

(Answer to Q. 4)  ANS: C
Thyrotoxicosis, which refers to the hypermetabolic clinical syndrome that results from serum ele-vations in thyroid hormone, can cause sinus tachycardia. Vomiting, hypothermia, and mediastinal tumors can cause sinus bradycardia.

(Answer to Q. 5)  ANS: D
Ingestion of large quantities of coffee, which contains caffeine, can cause a healthy person to have premature ventricular beats.

(Answer to Q. 6)  ANS: C
-Adrenergic blocking agents block stimulation by the sympathetic nervous system, causing the heart to slow down its rate. This can lead to sinus bradycardia.

(Answer to Q. 7)  ANS: A
Atrial fibrillation is characterized by gross irregularities in both atrial and ventricular depolariza-tion. The P waves have been replaced by fibrillatory waves, which have caused an undulation of the baseline. Not every atrial depolarization has been transmitted by the atrioventricular node.

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