Focal atrial tachycardia (AT) is the second postoperative tachycardia with automatic mechanism. This tachycardia is described as a narrow QRS tachycardia, ventricular rate of 150–250 bpm, warm up/cool down behavior, and variable atrial rate because of autonomic fluctuation (Walsh et al. 1992) (Fig. 34.2). Injury to atrial myocardium is one of the main pathologic factors. Vena caval cannulation during cardiac surgery and CV line insertion are other predisposing factors. Sinus node dysfunction is also a risk factor for AT. Automatic AT should be treated similar to JET.

Atrial flutter (AFL) and intra-atrial reentrant tachycardia (IART) are atrial arrhythmias with reentrant mechanism. These arrhythmias are recognized on an ECG by the presence of narrow QRS tachycardias and characteristic “sawtooth” wave in AFL or “isoelectric line” in IART at a regular rate of 240–440 bpm (Fig. 34.3). Ventricular rate depends on status of AV node (Fig. 34.4). Many factors predispose patients to AFL/IART. The most important factor is the degree of injury to atrial myocardium and region of scars and fibrotic tissue after atriotomy, incision, and suture lines. Other causes including the presence of atrial enlargement due to preexisting valvular disease and hemodynamic instability. Treatment should be focused on elimination of predisposing factors, rectification of residual defect as much as possible, and improvement of hemodynamic status. If the AFL/IAART are associated with acute hemodynamic instability, synchronized electrical cardioversion 0.5–1 J/kg should be done immediately. Success rate of cardioversion is reported up to 87 % (Texter et al. 2006). Anti-arrhythmic drug therapy is indicated if the arrhythmia persists. Class IC anti-arrhythmic drugs such as flecainide or propafenone are recommended for rhythm control in setting of preserved left ventricular function; however, amiodarone is the first choice drug in patients with reduced left ventricular function. Because of high incidence of amiodarone-related complications, careful patient follow-up is necessary. These assessments included ECG, chest X-ray, spirometry, and appropriate laboratory test including thyroid and liver function tests. If the rate control is planned, beta-blocker is the first line of therapy. Propranolol is usually well tolerated in children. In emergency setting, esmolol infusion with blood pressure monitoring is necessary. Most experts recommended the combination of class IC drugs with beta-blocker for prevention of 1:1 AV conduction after atrial rate reduction by class IC drugs.

AV reciprocating tachycardia (AVRT) and AV nodal reentrant tachycardia with reentrant mechanism are less common arrhythmia after cardiac operation. These arrhythmias are regular narrow QRS tachycardias with a heart rate of 150–250 bpm, paroxysmal initiation and termination, and P-wave deflection at the end of QRS or in the ST segment (Fig. 34.5). These arrhythmias may be controlled with vagal maneuvers but usually easily respond to intravenous adenosine. Treatment of underlying causes such as premature beats as a trigger, myocardial stress, and electrolyte disturbance has a critical role (Huang and Wood 2006).

Ventricular arrhythmia has been reported in 1–5 % of pediatric patients who have had palliative surgery for congenital heart disease; however, in Hoffman et al. study, incidence of non-sustained VT was 15.2 % (Delaney et al. 2006). VT refers to wide QRS tachycardia with a heart rate ≥100 bpm, VA dissociation, and sometimes 1:1 VA conduction (Fig. 34.6). The SVT with aberrancy and antidromic AVRT also stay on the list of differential diagnosis of wide complex tachycardia. However, postoperative wide QRS tachycardia should be considered VT until proven otherwise.

Perioperative ischemic-reperfusion events after cardiopulmonary bypass with damage to myocardium are main predisposing factors. Measurement of myocardial biomarkers such as troponin I may be useful (Delaney et al. 2006; Pfammatter et al. 2002). Hypercathecolaminergic state, inotropes, and electrolyte and metabolic abnormalities may also predispose the pediatric patients to ventricular arrhythmias in early postoperative period (Peretto et al. 2014). Scar-related ventricular arrhythmia usually presents as monomorphic VT. This kind of arrhythmia has been observed both early and late after pediatric cardiac surgery. Some types of CHD like tetralogy of Fallot are more susceptible to this arrhythmia (Huehnergarth et al. 2008). The incidence of scar-related arrhythmia gradually increased with time, and the degree of damage to myocardium and extent of scar determine arrhythmia character and frequency (Zeppenfeld et al. 2007; Papagiannis 2005). Basically, all postoperative events that terminated to low cardiac output and decreased ventricular function could cause ventricular arrhythmia that itself could deteriorate the cardiac output that worsen the patient hemodynamic condition.

In most patients, postoperative premature ventricular complexes resolved spontaneously without serious complication. If the patient developed hemodynamically unstable VTs, immediate electrical cardioversion of 1–2 J/kg is indicated (Kleinman et al. 2010). In patients with stable sustained VT, intravenous amiodarone is the first-line therapy.