Cardiac Intensive Care
Anthony C. Chang
Sheri S. Crow
Sylvia Del Castillo
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1. Two hours after returning from a bidirectional Glenn procedure, a 10-month-old male with a history of pulmonary atresia with intact ventricular septum (PA/IVS) is intubated with SaO2s (oxygen saturations) persistently 66% to 68%.
Which of the following is most likely responsible for the hypoxemia?
A. Venovenous collateral vessel
B. Systemic hypertension
C. PaCO2 of 38 mm Hg
D. PA pressure 14 mm Hg
E. Moderate atrioventricular valve regurgitation
1. (A) Hypoxemia is the most common short- and long-term complication following the bidirectional Glenn connection. Etiologies include decreased cerebral blood flow from hypocapnia or hypotension, decreased pulmonary blood flow from elevated PVR, venovenous collateral vessels, stenosis of cavopulmonary junction, and ventilation/perfusion mismatch (pleural effusion/pneumothorax). The PA pressure listed is normal.
2. An 11-month-old male with a history of tetralogy of Fallot (TOF) on propranolol at home is now immediately status post a valve-sparing complete TOF repair. Vital signs: core temperature 38.7°C, HR 178 bpm, CVP 11 mm Hg, BP 72/46 mm Hg, SaO2 97% on FiO2 0.35 on minimal ventilatory support. Regular and atrial ECG is shown in Figure 10.1.
The most likely diagnosis is:
A. Sinus tachycardia
B. Ectopic atrial tachycardia
C. Junctional ectopic tachycardia
D. Supraventricular tachycardia (AVNRT)
E. Complete AV block
2. (C) Junctional ectopic tachycardia is believed to be a result of direct trauma to the AV node and bundle of His, most commonly seen after TOF repair. Diagnosis is based on ECG evidence of narrow complex tachycardia with heart rates ranging from 170 to 260 bpm and a regular rhythm with AV dissociation. The QRS is usually narrow but can be wide with RBBB. P waves can be hidden, dissociated, or retrograde, as demonstrated by the two ECGs shown.
3. A 4-year-old male with a history of HLHS is now immediately status post an 18-mm nonfenestrated extracardiac Fontan procedure. He is intubated and on inotropes. Which of the following vital signs would NOT support a diagnosis of postoperative low cardiac output state?
A. Sinus tachycardia with HR 172 bpm
B. Core temperature 38.8 °C
C. Pulmonary artery pressure 18 mm Hg
D. SaO2 99% on FiO2 0.6
E. Arterial line BP 68/43 mm Hg
3. (D) After the Fontan operation, cardiac output is determined by pulmonary blood flow (PBF). Any reduction of PBF will reduce systemic oxygen delivery and cardiac output. All of the vital signs listed are seen in a low cardiac output state in a nonfenestrated extracardiac Fontan except for hypoxemia.
4. A 1-week-old male with d-TGA/ASD/VSD is now 4 hours after an arterial switch operation with ASD and VSD closure, PDA ligation, and a LeCompte maneuver. He is intubated, with a closed sternum, on the following inotropes: epinephrine 0.05 mcg/kg/min, milrinone 0.25 mcg/kg/min.
Vital signs are as follows: core temperature 37.4 °C, HR 173 bpm, BP 46/19 (28) mm Hg, LA pressure 14 mm Hg, CVP 13 mm Hg, SaO2 98% on FiO2 0.4.
Which of the following would likely NOT be a cause of the above vital signs?
A. Moderate mitral valve regurgitation
C. Coronary artery ischemia
D. Left ventricular systolic dysfunction
E. Pericardial tamponade
4. (B) All of the listed options are examples of low cardiac output state following arterial switch operation. Elevated CVP is not consistent with a hypovolemic state.
5. A 16-year-old previously healthy male is admitted to the CVICU after presenting to the emergency department with a 2-week history of intermittent fever, rhinorrhea, cough, SOB, and orthopnea. Vital signs: temperature 37.4 °C, HR 135 bpm with S3 gallop heard, respiratory rate 30 breaths per minute, cuff BP 111/62 mm Hg, and SaO2 95% on room air. Rales heard on lung examination and hepatomegaly palpated.
The CXR in Figure 10.2 is obtained.
Which of the following therapies is the BEST initial therapy?
A. Furosemide IV
C. Digoxin PO
5. (A) The presence of cardiomegaly, hepatomegaly, tachypnea, and a gallop rhythm are all consistent with volume overload from congestive heart failure (CHF) and loop diuretics are essential first-line therapy, particularly with stable pressures. The use of inotropes may be necessary to improve contractility, but diuresis is an important hallmark of initial therapy for CHF.
6. A 1-week-old female with HLHS just returned from the OR following a Norwood procedure with a 3.5-mm Blalock-Taussig (BT) shunt. She is intubated with an open sternum, on inotropic support, bleeding, and requiring volume resuscitation with several blood products. During resuscitation, she has an acute drop in her SaO2 from the low 80%s to the low 60%s with significant drop in ETCO2 followed by hypotension. The most likely cause of this is:
A. Accidental extubation
B. Acute tension pneumothorax
C. Right mainstem endotracheal tube displacement
D. Acute pulmonary hypertensive crisis
E. Acute occlusion of the systemic to pulmonary artery shunt
6. (E) Acute hypoxemia in a patient with a modified BT shunt must be evaluated promptly and suspicion for occlusion of the shunt must be high, especially in a patient who is bleeding postoperatively and actively being resuscitated with blood products. All of the other options could possibly explain an acute episode of hypoxemia, however, are less likely given the scenario of postoperative bleeding with blood product administration.
7. (C) The ratio of pulmonary to systemic blood flow can be easily calculated in single ventricle physiology patients by using the Fick method, which states Cardiac output = Oxygen consumption divided by arteriovenous oxygen difference. There are assumptions that allow the Fick equation to be derived to incorporate systemic and pulmonary saturations to calculate Qp:Qs. First, there is no significant pulmonary venous desaturation so that the pulmonary venous saturation is 95% to 100%. Second, the aortic and pulmonary artery saturations are equal as measured by pulse oximetry. The equation Qp:Qs is [SaO2 – SvO2]/[pulmonary venous saturation – pulmonary artery saturation]. In this case, the equation is [92% – 70%]/[99% – 92%] or about 4:1.
8. Which of the following congenital heart lesions is NOT associated with postoperative junctional ectopic tachycardia (JET)?
B. Tetralogy of Fallot
C. Total anomalous pulmonary venous return
E. d-TGA status post arterial switch operation
9. A 15-year-old previously healthy male with no significant past medical history is admitted with a diagnosis of acute viral myocarditis with an LV ejection fraction of 25% on a transthoracic echocardiogram. He is peripherally cannulated emergently to venoarterial extracorporeal membrane oxygenation (ECMO) support. Shortly after cannulation, copious pink frothy secretions are noted from his endotracheal tube. The best therapy to address this event is:
A. Furosemide 20 mg IV × 1
B. STAT cardiac catheterization for balloon atrial septostomy
C. Increase PEEP on the ventilator from 10 mm Hg to 15 mm Hg
D. Increase ECMO flows from 100 cc/kg/min to 130 cc/kg/min
E. Start an epinephrine infusion to aid with myocardial contractility
9. (B) Pulmonary edema following ECMO cannulation is a clear indicator of severe left ventricular (LV) dysfunction. The best therapy to ultimately address the inability of the LV to decompress until it can regain function is a balloon atrial septostomy thus creating an LV/LA vent to further prevent myocardial ischemia. The other therapies are useful adjunctive therapies to address the pulmonary edema but will not resolve the underlying issue of poor LV function.
A. Epinephrine infusion
B. Milrinone infusion
C. Supplemental oxygen therapy
D. PRN lorazepam
10. (A) The goal of preoperative management of patients with severe CHF is focused on optimizing myocardial oxygen supply and reducing myocardial oxygen demand. Of all of the therapies listed, epinephrine would be the most likely to increase myocardial oxygen demand based on the chronotropic effect, while all other therapies would either increase oxygen supply or reduce demand.
11. Factors that increase endothelial-derived nitric oxide (EDNO) production include all of the following EXCEPT:
D. NG-monomethyl-L-arginine (L-NMMA)
11. (D) Of all the factors listed, L-NMMA is known to decrease the synthesis of EDNO.
12. The Law of Laplace, as it relates to wall stress of the left ventricle states:
A. Wall stress is directly proportional to the thickness of the ventricle
B. Wall stress is indirectly proportional to the transmural pressure of the ventricle
C. Wall stress is directly proportional to the change in radius of the ventricle
D. Wall stress is increased with positive pressure ventilation
E. Wall stress is decreased with upper airway obstruction
12. (C) Laplace law states the circumferential wall stress (T) is equal to the pressure (P) times the radius (r) divided by twice the wall thickness (t): T = (P × r)/2t. Positive pressure ventilation decreases LV wall stress by decreasing LV transmural pressure. Upper airway obstruction increases LV wall stress by causing huge increases in transmural pressure.
13. A 5-month-old male with a history of tetralogy of Fallot and pulmonary stenosis who is on propranolol at home is admitted to the cardiac ICU for severe hypoxemia. His VS: temperature 37.5 °C, HR 155 bpm, BP 70/46 mm Hg, RR 32, SaO2 66% on 4 LPM nasal cannula. All of the following therapies are indicated EXCEPT:
A. Initiation of milrinone infusion
B. Consider intubation if hypoxemia persists
C. Initiation of an esmolol infusion
D. Sedation with morphine 0.1 mg/kg IV
E. Initiation of phenylephrine infusion
13. (A) All of the therapies listed are known to aid acute Tet spells except the initiation of milrinone.
14. A 3-week-old male is 5 hours following complete repair of type I truncus arteriosus with ASD and VSD closure. He is intubated on volume control ventilatory support with a PEEP of 4, with low peak pressures on the ventilator, tidal volumes of 6 cc/kg, with SaO2 96% on FiO2 0.6. Arterial blood pressure is 72/40 mm Hg on milrinone 0.5 mcg/kg/min and epinephrine 0.03 mcg/kg/min. He has an acute increase in his CVP from 8 mm Hg to 15 mm Hg and a drop in his ETCO2 with hypoxemia to 76% followed by hypotension. All of the following are appropriate immediate therapies EXCEPT:
A. Bolus of fentanyl 1 mcg/kg IV
B. Initiation of iNO at 20 ppm
C. Increase FiO2 to 1.0
D. Increase milrinone infusion to 0.75 mcg/kg/min
E. Hyperventilate the patient
14. (D) All of the therapies listed would provide immediate benefit to a patient during an acute pulmonary hypertensive crisis except increasing the milrinone, as the effect would not be seen immediately.
15. Which of the following postoperative complications is most anticipated following repair of a patient with a complete atrioventricular septal defect?
A. Ventricular tachycardia
B. Junctional ectopic tachycardia
C. Aortic valve regurgitation
D. Atrial flutter
E. Ectopic atrial tachycardia
16. Expected complications following end-to-end anastomosis of a coarctation of the aorta (CoA) include:
A. Systemic hypotension
B. Pulmonary hypertension
C. Acute kidney injury
D. Phrenic nerve injury
E. Feeding intolerance
16. (D) Surgical morbidity after repair of CoA includes anastomotic bleeding, cardiac arrest, chylothorax, GI bleeding, phrenic nerve or recurrent laryngeal nerve injury, postcoarctectomy hypertension, seizures, and spinal cord injury. None of the other complications listed are expected after end-to-end repair of CoA.
17. A 2-week-old male with type I truncus arteriosus is immediately postop from repair with VSD closure and RV-PA conduit. Postop TEE showed moderate RVH, moderate truncal valve insufficiency, no residual ASD/VSD, and normal biventricular function. Vital signs: core temperature 38.6 °C, HR 178 bpm (junctional), BP 74/48 mm Hg, CVP 12 mm Hg, RR 30 with the ventilator, SaO2 97%, FiO2 0.4. Pressors include epinephrine 0.03 mcg/kg/min, milrinone 0.5 mcg/kg/min. Of the listed therapies, the least likely to benefit this patient would be:
A. Increase epinephrine to 0.05 mcg/kg/min
B. Cool patient to 36 °C
C. Amiodarone 5 mg/kg IV bolus
D. Maintain arterial pH >/= 7.40
E. Increase milrinone to 0.75 mcg/kg/min
17. (A) Common postoperative complications following repair of truncus arteriosus include arrhythmias such as JET, pulmonary hypertension, and truncal valve insufficiency. Based on the patient’s postoperative TEE showing moderate truncal insufficiency, and current JET, all the therapies listed are geared toward reducing pulmonary vascular resistance (arterial pH 7.40 and increasing milrinone) or treatment of JET (cooling patient and amiodarone bolus). Increasing epinephrine infusion would potentially increase SVR, worsening truncal valve insufficiency and cardiac output.
18. A 10-week-old male with a history of HLHS, status post a Norwood procedure with a 3.5-mm modified BT shunt as a neonate, is admitted to the cardiac ICU after presenting in the emergency department with a history of poor feeding, lethargy, diaphoresis, and poor weight gain over the last 5 days. On examination, he is tachypneic to the 50s, with 1+ pulses distally and a loud continuous shunt murmur heard at the right upper sternal border. Pulse oximetry reads 76% on room air. Which of the following is the most likely reason for his presenting symptoms?
A. Pulmonary vein stenosis
B. Distal aortic arch obstruction
C. Shunt stenosis
E. Pulmonary artery distortion
18. (B) In a patient following a Norwood procedure with arch reconstruction who presents with CHF symptoms, distal aortic arch obstruction should be high on the differential diagnosis as this is a common late complication. All the other choices would have presented with hypoxemia as the primary symptom.
19. Each of the following scenarios would be expected in a newborn male with a diagnosis of infracardiac total anomalous pulmonary venous return (TAPVR) immediately postop following repair EXCEPT:
A. Low left atrial filling pressures
B. Decreased pulmonary compliance
C. High pulmonary vascular resistance
D. Pulmonary edema
E. Junctional ectopic tachycardia
19. (A) Infracardiac TAPVR is the second most common type of TAPVR and is characterized by severe hypoxemia, acidosis, and hypotension. A low cardiac output state results from decreased left atrial and left ventricular (LV) compliance due to abnormal preoperative filling. Underfilling of the LV can be exacerbated by pulmonary hypertension (PHTN) and right ventricular (RV) dilation. Often, the removal of the pulmonary venous obstruction with a subsequent increase in blood return to the LA further increases LAP, causing the cycle of worsening pulmonary edema, PHTN, and subsequent RV and LV dysfunction.
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