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. (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. (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. (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) 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. (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. (D) All of the lesions listed are commonly associated with postop JET except for ASDs. The mechanism of JET is not proven but thought to be related to a combination of traction or trauma to the AV node and His bundle or ischemia during surgery.

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.

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. (D) Of all the factors listed, L-NMMA is known to decrease the synthesis of EDNO.

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) All of the therapies listed are known to aid acute Tet spells except the initiation of milrinone.

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. (B) The most common dysrhythmias seen after repair of complete atrioventricular canal (CAVC) defect include junctional ectopic tachycardia and complete or transient AV block due to repair around the AV node. The other dysrhythmias are not commonly seen after CAVC repair.

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) 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. (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. (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.