CCRN Practice Questions - Cardiovascular

A patient is in cardiac and respirato￾ry arrest. The selection of medications to reestablish cardiac function would stimulate the sympathetic nervous sys￾tem beta1 receptors. This stimulation would result in increased automaticity and which of the following? a. Increased myocardial contractility b. Decreased left ventricular stroke work c. Decreased myocardial oxygen con- sumption d. Increased left ventricular afterload Correct answer: a Rationale:The sympathetic nervous sys￾tem contains alpha, beta, and dopamin- ergic receptors that produce various re- sponses when stimulated. Stimulation of beta1 receptors increases heart rate, conductivity, and myocardial contractility. Stimulation of beta2 receptors produces vasodilation and bronchodilation. Alpha receptors, when stimulated, produce vasoconstriction. Stimulation of dopaminergic receptors produces a va- sodilating effect on renal, mesenteric, coronary, and cerebral vessels. Test-Taking Strategy: Note the helpful clue in the stem: stimulate the sympa￾thetic system and recall that this results in a fight-or-flight response—the body is responding to survive. Stroke volume would increase, so eliminate option b. Af￾terload would increase, but this is due to alpha stimulation, not beta1 stimulation, so eliminate option d. Because the heart is working faster and harder, the myocar- dial oxygen consumption does increase, so eliminate option c. Remember that the primary effects of beta1 receptors are to increase heart rate, contractility, and rate of conduction. Choose option a. A mem- ory aid that also may help is this: beta 1 beta 2, 1 heart 2 lungs: beta1 affects the heart, and beta2 affects the lungs. Correct answer: d Rationale:ST segment elevation in leads V3 and V4 indicates injury to the ante￾rior wall, which would occur with occlu- sion of the left anterior descending (LAD) artery. In most persons, the SA node, CCRN Practice Questions - Cardiovascular 2 / 28 A patient arrived in the emergency de- partment with complaints of chest pain. The 12-lead electrocardiogram shows ST segment elevation in leads V3 and V4. Occlusion of the affected coronary artery most likely would affect perfusion to which portion of the conduction system? a. Sinoatrial (SA) node b. Bachmann's bundle c. Atrioventricular (AV) node d. Bundle of His Oxygen delivery (DO2) is the product of which of the following? a. PaO2, hemoglobin, mean arterial pressure b. SaO2, hemoglobin, cardiac output c. SvO2, cardiac index, SaO2 d. PaO2, mean arterial pressure, SvO2 Bachmann's bundle, and AV node are supplied by the right coronary artery.The bundle of His is supplied by the left ante￾rior descending artery. This is why an anterior myocardial infarction may cause type II second-degree AV block or third-degree AV heart block at the level of the bundle of His. Test-Taking Strategy: Note that options a, b, and c are part of the supraventricu￾lar conduction system. They usually are supplied by the right coronary artery.The LAD artery supplies most of the interven￾tricular conduction system, including the bundle of His and the bundle branches. Correct answer: b Rationale: Ninety-seven percent of oxy- gen is attached to the hemoglobin mol- ecule, so the SaO2 (arterial oxygen sat- uration) is a more accurate reflection of the amount of oxygen in blood. The PaO2 represents only the 3% that is dis- solved in the plasma.The lungs must put the oxygen in the blood, the hemoglobin must carry the oxygen, and the cardiac output is a reflection of how well the heart is moving the blood with its hemoglobin with attached oxygen. SvO2 (venous oxygen satura￾tion) is a reflection of the oxygen reserve. SvO2 is what is left over after the tis- sues have extracted what they need.The mean arterial pressure is a reflection of organ tissue perfusion pressure but does not indicate anything about the amount of oxygen in that blood. Test-Taking Strategy: Oxygen is deliv- ered from the arterial end, so choose an CCRN Practice Questions - Cardiovascular 3 / 28 Which of the following types of block are most likely after an anterior wall myocar- dial infarction (MI)? a. Sinus block b. Second-degree atrioventricular (AV) block, type I c. Second-degree AV block, type II d. Third-degree AV block with junctional escape rhythm option that has SaO2 instead of SvO2. Also remember that most oxygen is car￾ried on hemoglobin. Look for SaO2 (not PaO2) and hemoglobin. The only option with both of these is option b. Correct answer: c Rationale: Anterior MI is caused by a left anterior descending (LAD) artery lesion. The LAD artery supplies the bundle of His and bundle branches, so anterior MIs may cause blocks of the bundle of His or bundle branches. Second-degree AV block type II is a block at the level of the bundle of His. If this patient does develop a third-degree AV block, it would be at the level of the bundle of His, and the only escape rhythm available below the bun- dle of His is a ventricular escape rhythm. Test-Taking Strategy: The sinus node is supplied by right coronary artery (in 55% of people) or left coronary artery (in 45% of people), so eliminate option a. Type I AV block, also called Wenckebach, is a block at the AV node, and the AV node is supplied by right coronary artery (in 90% of people) or left coronary artery (10%), so eliminate option b. The LAD artery supplies the bundle of His, and blocks in this area would elimi- nate the possibility of junctional escape rhythms, so eliminate option d. Choose option c. CCRN Practice Questions - Cardiovascular 4 / 28 A patient develops atrial fibrillation after abdominal surgery. Her blood pressure falls from 110/70 mm Hg to 92/68 mm Hg. The hypotension is related to which of the following? a. Decrease in ventricular contractility b. Hypovolemia c. Mural thrombi d. Decrease in ventricular filling A shift in the point of maximal impulse (PMI) to the fifth left intercostal space at the anterior axillary line could be caused by any of these conditions except: a. left ventricular hypertrophy. b. right tension pneumothorax. c. pericardial effusion. d. right pleural effusion. Correct answer: d Rationale: The contribution that atrial contraction makes to ventricular filling volume is approximately 15% to 30%. Atrial fibrillation results in quivering but not contracting atria. The loss of 15% to 30% of diastolic filling volume reduces cardiac output and can have significant hemodynamic consequences. Although mural thrombi also are a problem, they result in an embolic phenomenon rather than a direct decrease in cardiac out- put. The relatio