	Life-Threatening^∗	Not Life-Threatening
Arrhythmia	AF with bypass tract Atrial flutter Mustard Frontan CHB with hypotension or CHF and/or ventricular escape Ventricular tachyarrhythmias with symptoms	AF without bypass tract CHB: normal hemodynamics and nodal escape Isolated PVCs Asymptomatic, nonsustained VT
Ischemia	Ongoing chest pain with ischemic ECG changes	Chronic nonischemic chest pain
Ventricular failure	New murmur + fever Compromising pleural effusion or ascites
Cyanosis	Loss of continuous murmur in patient with BT or central shunt Acute pulmonary infection	Chronic cyanosis
Noncardiac	Hemoptysis Transient ischemic attacks or seizures (new onset)	Gout Biliary colic

Abbreviations: AF, atrial fibrillation; BT, Blalock-Taussig shunt; CHB, complete heart block; VT, ventricular tachyarrhythmias.

∗ Warrants admission to CICU.

There are emergencies that are unique to the patient with congenital heart disease: For example, the occurrence of pregnancy in the patient with Eisenmenger syndrome. The drop in systemic vascular resistance in these patients increases the right-to-left shunt and results in arterial desaturation. However, most emergent complications seen in congenital heart disease are similar to the emergency situations seen in cardiovascular problems of other more common etiologies. The diagnosis of ventricular tachycardia in a patient with repaired tetralogy of Fallot is treated in a manner similar to the patient with coronary disease and ventricular tachycardia and, unfortunately, with the same uncertain efficacy. It is important to remember that a patient with repaired tetralogy of Fallot is at risk of developing ventricular tachycardia and to recognize the importance of investigating palpitation and presyncope and syncope. Substantial analogies to the care of general cardiac patients exist, but this needs to be combined with knowledge of what complications to expect with what lesion and management needs to be tailored to a congenital patient’s unique anatomy (Table 34-2).

Table 34–2 Complications of Congenital Heart Disease

Lesion	Special Considerations
Tetralogy of Fallot	Ventricular tachycardia Atrial fibrillation Right ventricular dysfunction Pulmonary regurgitation (late complication usually associated with moderate to severe regurgitation)
Fontan	Ventricular dysfunction Sinus node dysfunction Atrial flutter/intra-atrial re-entrant tachycardia (IART) Fontan obstruction or leak Pulmonary embolus
D-transposition of great arteries	Atrial flutter/IART Systemic right ventricular dysfunction AV block (uncommon late) Baffle systemic AV valve regurgitation Sinus node dysfunction with junctional rhythm (usually asymptomatic)
L-transposition of great arteries	Systemic ventricular failure AV block Systemic AV valve regurgitation WPW (2%-4%)
Coarctation	Dissection Bicuspid valve with endocarditis, regurgitation, or stenosis Early coronary artery disease or heart failure Cerebral aneurysm
Left-to-right shunt	Pulmonary hypertension (Eisenmenger syndrome) Atrial fibrillation Endocarditis (VSD or PDA, rare with ASD)
Right-to-left shunt (cyanotic)	Paradoxical embolus Worsening cyanosis Brain abscess Bleeding diasthesis Hyperviscosity syndrome with erythrocytosis Protein-losing enteropathy
Marfan	Dissection Aortic valve regurgitation Mitral valve prolapse

In the patient with a cardiac emergency, congenital heart disease can predispose the patient to certain complications that may be responsible for the cardiac emergency. For example, in a patient with L-transposition of the great vessels and shortness of breath, the right ventricle is acting as the systemic ventricle and is prone to failure. The diagnosis of heart failure is not difficult, and treatment of congestive heart failure in these patients is similar to the treatment of congestive heart failure in those with other conditions.

Anatomic and Pathophysiologic Classification of Congenital Heart Disease

During the formation of the heart and cardiovascular system, there are many opportunities for the development of the lesions of congenital heart disease. The large variety of lesions forming the body of congenital heart disease can be confusing. It is helpful for the cardiologist seeing adult patients to think of these lesions in an organized manner. The following classification is helpful in that all congenital heart patients fit into one or more of these categories.

1. Predominant left-to-right shunt. Blood that has gone through the lungs, recirculates to the right side of the heart, and as a result the pulmonary blood flow is greater than the systemic blood flow. The shunt can occur at any level (e.g., at the venous level, anomalous pulmonary vein to the superior vena cava; at the atrial level, ASD; at the ventricular level, VSD; at the arterial level, PDA).

2. Predominant right-to-left shunt, or “cyanotic disease.” The blood is shunted from the right heart to the systemic circulation, bypassing the lungs. The arterial blood is therefore desaturated. If the amount of desaturated hemoglobin is 5 g/dL or greater, cyanosis can be observed. The systemic blood flow is greater than the pulmonary blood flow. This shunt also can occur at any level of the cardiovascular system (e.g., at the venous level, superior vena cava draining into the left atrium; at the atrial level, tricuspid atresia with an ASD; at the ventricular level, tetralogy of Fallot; at the arterial level, truncus arteriosus).

3. Stenotic or atretic valves and hypoplastic or atretic ventricles. The valves can also be incompetent. Either ventricle may be hypoplastic or atretic.

4. Great vessel abnormalities. Transposition of the great vessels, coarctation of the aorta, PDA, vascular rings, and truncus arteriosus.

5. Abnormalities of position. Transposition of the great vessels, L-transposition, dextroposition, and dextrocardia.

Arrhythmias

Arrhythmias are some of the more common emergencies seen in patients with congenital heart disease. There are two types of arrhythmias: bradyarrhythmias (e.g., sick sinus syndrome, sinus arrest, varying degrees of heart block including complete heart block) and tachyarrhythmias (e.g., atrial fibrillation, atrial flutter, ventricular tachycardia, and fibrillation).

The arrhythmic patient may have palpitations, presyncope, or syncope. With atrial tachyarrhythmias, the patient usually complains of palpitations, which sometimes are severe enough to frighten the patient. Presyncope or syncope occurs with extremely rapid ventricular response, raising pulse rates to 200 beats/min or more. If the left ventricle is noncompliant with an atrial tachyarrhythmia, especially atrial fibrillation—in which there is no atrial contraction—stroke volume can fall dramatically, and the patient may develop syncope. The diagnosis of this type of arrhythmia can be made by electrocardiogram (ECG) if the arrhythmia is persistent. However, even if the patient having syncope or presyncope is in sinus rhythm at the time of the examination, it is most important to consider the patient with congenital heart disease, with or without repair, as having a potentially fatal arrhythmia.

The atrial bradyarrhythmias and tachyarrhythmias encountered in patients with congenital heart disease may result from hemodynamic alterations of the atrium or involve areas of slowed conduction in the areas of scar associated with prior surgery. These may include surgery for ASD repair,³ both ostium secundum and ostium primum defects, Fontan procedures for tricuspid atresia or single ventricle,^4,⁵ and the Mustard or Senning procedure for transposition of the great arteries.^6,⁷

Lesions affecting the conduction system and causing AV block have become less common since surgeons have learned to avoid the conduction system during surgery. However, with any VSD repair, immediate injury or later injury as a result of fibrosis is a possible cause of progressive heart block. With advances in surgical technique and knowledge of the path of the conduction system, heart block after repair of VSD is increasingly rare with persistent heart block seen in less than 1% of patients.⁸

L-transposition, or corrected transposition of the great vessels, is a lesion in which ventricular inversion has occurred without inversion of the atria or great arteries. In this condition, the anatomic right ventricle is the systemic ventricle and the anatomic left ventricle is the pulmonic ventricle, but the physiologic passage of blood is normal (i.e., the systemic venous return is pumped to the lungs, and the pulmonary venous return is ejected into the aorta). The conduction system is also inverted and the AV node is abnormally located and often dual with elongation of the bundle of His.⁹ As a result, these patients have a high rate of AV block, which can occur at all levels of severity—from first to third degree—and which increases in incidence with age at a rate of about 1% to 2% per year.

Atrial Tachyarrhythmias

The diagnosis and treatment of bradyarrhythmias and tachyarrhythmias are the same in patients with congenital heart disease as for those with other lesions. When symptomatic bradycardia and hemodynamic instability, such as hypotension or syncope, are present, a pacemaker is indicated.

Atrial fibrillation, tachycardia, and flutter, when they occur in patients with congenital heart disease, are usually relatively not life-threatening.^10,¹¹ These arrhythmias occur in about 20% of patients with ASDs and can recur even after the ASD is repaired, especially when the repair is performed late in life (after the age of 40).³ In some defects, atrial fibrillation or atrial flutter can be very serious and even life-threatening. The treatment is similar to that of atrial fibrillation or atrial flutter due to other causes; with rapid atrial tachycardia in patients with hemodynamic instability, immediate cardioversion is indicated. In patients who are hemodynamically stable with noncontracting atria, which may be seen in conditions such as atrial fibrillation and atrial standstill, anticoagulation therapy for 3 weeks before cardioverting is indicated. In such cases, the patient should receive anticoagulation for 3 weeks after cardioversion until mechanical atrial contraction is well established. If the patient is hemodynamically stable, the ventricular response can be slowed with amiodarone, β-blockers, verapamil, or diltiazem. If it is necessary to cardiovert before achieving stability, a period of anticoagulation can be provided. Transesophageal echocardiography (TEE) to rule out evidence of atrial thrombus is desired and allows safe cardioversion. With atrial tachycardia, 6 mg adenosine given intravenously usually converts the patient to sinus rhythm. If this treatment is unsuccessful, another 6 to 12 mg of adenosine can be given.

Atrial flutter or intra-atrial re-entrant tachycardia occurs frequently in patients who have undergone a Fontan procedure, with the prevalence estimated as high as 50% in adult patients. The presentation is usually subacute but occasionally hemodynamic instability and even sudden death especially in the setting of 1:1 conduction.¹² The patient should be converted to normal sinus rhythm either pharmacologically or by cardioversion with the caution that antiarrhythmics may exacerbate sinus node dysfunction, AV conduction, or promote 1:1 conduction of an atrial arrhythmia. If atrial flutter recurs, the patient should be referred to an electrophysiologist to map the pathways of flutter, if possible. If this can be done, catheter ablation of the pathway is possible. If atrial flutter or atrial tachycardia recurs incessantly and ablation attempts fail, then ablation of the AV node with placement of a dual-chamber (DDD) pacemaker should be considered. If the patient does not remain in sinus rhythm, then a physiologically responsive (VVIR) pacemaker is the treatment of choice.

Another atrial arrhythmia that can be fatal is atrial tachycardia and subsequent atrial fibrillation in a patient with an antegrade conducting bypass tract. In this condition, the impulse conducts from the atrium to the ventricle over the bypass tract. Especially with sympathetic stimulation or increased conductivity induced by digitalis, the ventricular response can approach 250 to 300 beats/min, and the patient may develop ventricular fibrillation. In patients with a possible AV bypass tract, digoxin should always be avoided. Patients with Ebstein anomaly have 25% incidence of bypass tracts in the posteroseptal location and a bypass tract may be present in 2% to 4% of patients with L-TGA.

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