Chapter21

Detailed Answers to Assess Your Understanding

  1. c: Inflammation of the pericardium is called pericarditis.It can produce sharp, substernal chest pain. The pain has an abrupt onset that worsens on inspiration or by movement, particularly when the individual is lying down. The pain lessens when sitting up and leaning forward. The most common causes of pericarditis are viral and bacterial infections. Other causes include uremia, renal failure, rheumatic fever, connective tissue disease, and cancer. Sometimes pericarditis can accompany an MI. When pericarditis occurs in conjunction with MI, it develops several days after the infarction.
  2. b: ECG changes seen with pericarditis include an elevated ST segment that is usually flat or concave.
  3. a: In comparison to myocardial infarction the ECG changes seen with pericarditis include diffuse ST segment and T wave changes.
  4. b: Electrical alternans is a condition in which the electrical axis of the heart varies with each beat. It occurs due to pericardial effusion which is a buildup of an abnormal amount of fluid and/or a change in the character of the fluid in the pericardial space. If the effusion is large enough, the heart may rotate freely within the fluid-filled sac resulting in the electrical axis of the heart varying with each beat. This is most easily recognized on the ECG by the presence of QRS complexes that change in height with each successive beat. This condition can also affect the P and T waves.
  5. d: A pulmonary embolism is an acute blockage of one of the pulmonary arteries by a blood clot or other foreign matter. This leads to obstruction of blood flow to the lung segment supplied by the artery. The larger the artery occluded, the more massive the pulmonary embolus and therefore the larger the effect the embolus has on the lungs and heart. Due to the increased pressure in the pulmonary artery caused by the embolus, the right atrium and ventricle become distended and unable to function properly, leading to right heart failure. This condition is referred to as acute cor pulmonale. Massive pulmonary embolism impairs oxygenation of the blood, and death may result. The most common source of the clot is in one of the large pelvic or leg veins. The pain that accompanies a pulmonary embolus is pleuritic, and shortness of breath is often present.
  6. d: The characteristic ECG changes seen with massive pulmonary embolus include a large S wave in lead I, a deep Q wave in lead III, and an inverted T wave in lead III (this is called the S1 Q3 T3 pattern),right bundle branch block and tall, symmetrically peaked P waves in leads II, III, and aVF .
  7. ECG changes with type of cardiac condition with which they are seen: b. Hyperkalemia: Peaked T waves, widened QRS complexes, and sine-waves; c. Hypokalemia: Appearance of U waves, prolongation of the QT-interval; a. Hypocalcemia: Slightly prolonged QT interval.
  8. a: (True) Increases or decreases in the potassium and calcium serum levels can have a profound effect on the ECG.
  9. d: Prolonged QT intervals are associated with torsades de pointes.
  10. c: ECG changes associated with digoxin use include a gradual downward curve of the ST segment.
  11. b: The most common dysrhythmia seen with digoxin toxicity is paroxysmal atrial tachycardia (PAT) with 2nd-degree AV heart block.
  12. Use figure in answer 12 shown on page 633 of Fast & Easy ECGs 2nd Ed
  13. c: Renal failure results in abnormal retention of potassium. This elevated potassium level is called hyperkalemia.
  14. a: The hyperkalemic T wave is shaped like a tent with a sharp peak and concave sides that are of equal duration.
  15. a: As the potassium level increases the conduction is slowed throughout the P-QRS-T complex. The PR interval is prolonged and the QRS complex widens eventually merging into the T wave.