Guidelines for Postoperative Care of Tetralogy of Fallot Hala Agha, MD Professor of Pediatrics & Pediatric Cardiology Children Hospital, Cairo University Tetralogy of Fallot TOF represents approximately 10% of cases of congenital heart disease. Tetralogy of Fallot 1. RV outflow tract obstruction, usually infundibular and/or valvular pulmonic stenosis 2. VSD, usually large, subaortic, perimembranous, and nonrestrictive 3. Right ventricular hypertrophy, usually concentric 4. Rightward deviation of the origin of the aorta, over-riding the VSD Natural history of TOF Natural history is determined mainly by the degree of RVOT obstruction. Surgical treatment of TOF  Palliative surgery Blalock-Taussig shunt to secure pulmonary blood flow  Total surgical correction The goals of total repair OF TOF – To close the ventricular septal defect – To open the RV outflow obstruction, and – To repair any pulmonary artery stenosis Conditions which may complicate the postoperative care of the child with TOF are the following:  Right ventricular dysfunction  Residual VSD  Residual RV outflow tract obstruction  Arrhythmias Right ventricular dysfunction This may occur by the cumulative effects of: 1-Right ventriculotomy 2-Inadequate myocardial protection 3-Residual RVOTO ( infundibular, valvular stenosis, hypoplasia or stenosis of distal pulmonary arteries) 4-Pulmonary regurge caused by placement of transannular patch. Sudden reperfusion of the lungs and the use of by pass may produce pulmonary edema on the basis of altered pulmonary capillary permeability. Other contributing factors to respiratory failure include residual VSD, presence of large collaterals ( manage with diuretics). 5-Residual VSD. Suspect RV dysfunction in TOF repair:  Hypotension  Raised CVP  Large liver  RV function is described as restrictive since the problem is predominantly poor RV compliance. Restrictive Physiology of RV  Restrictive physiology of RV after TOF repair is defined by the need to maintain CVP to maintain cardiac output.  CVP causes 3rd space accumulated in the pleural and peritoneal cavities as well as peripheral edema.  Because of low CO, 3rd space is not easily removed by diuretic and may interfere with mechanical ventilation and organ function.  Clinically is diagnosed by low CO, slower postoperative recovery & persistent pleural effusion. Restrictive Physiology of RV  Classic Echo finding shows forward flow of blood across pulmonary valve with atrial systole. Typically recovers in 3-5days.  Restrictive physiology of RV may predict a more favorable long term outcome specially in patients with significant pulmonary regurge. Clinical assessment of cardiac output PHYSICAL EXAMINATION Low cardiac output Adequate cardiac output PERIPHERAL PERFUSION Poor capillary refill Good capillary refill (<3 secs) CORE-PERHIPERAL TEMP.GRADIENT >3 C <3 C PULSES Impalpable or weak peripheral pulses Full peripheral pulses URINE OUTPUT < 1 ml/kg/hr >1 ml/kg/hr MENTAL STATUS Combative, disorientated Co-operative ARTERIAL PRESSUREWAVEFORM Dichrotic notch soon after peak Dichrotic notch occurs later BASE DEFICIT Base excess > -5 mmol/L Base excess < -5 mmol/L LACTATE >4 mmol/L <2mmol/L BLOOD PRESSURE Refer to age – related normal ranges Treatment of RV dysfunction  Manage with volume and optimize RV filling and RA pressures of-15mmHg to 18mmHg may be necessary to ensure left sided filling and adequate systemic output.  Inotropic support with dopamine, dobutamine or milrinone .  -Maintain AV synchrony. Increase heart rate either pharmacologic or with pacing wires are usually required to improve cardiac output .  Ventilator maneuvers to reduce pulmonary vascular resistance and may reduce the afterload on the RV . -Particularly in infants, opening an atrial communication may be beneficial Treatment recommendations for phosphodiesterase inhibitors (milrinone) in TOF:  It is recommended that milrinone be considered for any patient following TOF repair to prevent the occurrence of low cardiac output due to restrictive right ventricular physiology after TOF repair.  It is recommended that milrinone be started for any patient with a right atrial pressure >15 mm Hg or with signs or symptoms of low cardiac output.  The recommended loading dose of milrinone is 50 mcg/kg over 30 to 60 minutes followed by an infusion at 0.375 to 0.75 mcg/kg/min. Mode of action of Milrinone  Milrinone is classed as an INODILATOR (inotrope with vasodilator properties).  It appears to selectively inhibit Phosphodiesterase enzyme 3 (PDE 3), which results in an increase in intracellular c-AMP and alteration in intracellular and extracellular calcium transport and relax arterial and venous smooth muscle.  Milrinone may have synergistic activity with catecholamines. Guidelines on the use of Milrinone Indications for use:  Congestive Heart Failure  Low cardiac output states following cardiac surgery  Patient’s refractory to escalating doses of catecholamines.  Prophylaxis in patients at high risk of developing low cardiac output syndrome (LCOS) following cardiac surgery e.g. Arterial switch, TOF Milrinone Parameters to monitor  Blood Pressure  Heart Rate  Platelet counts  Renal function  Peripheral perfusion Side effects Increased heart rate, risk of arrhythymias, thrombocytopenia, Hypotension, insomnia, nausea and vomiting, diarrhoea. Residual VSD  In the operating room, if the post-repair pulmonary artery saturation is normal and TEE is performed, the likelihood of undetected residual ventricular septal defect (VSD) is very low.  The sutures securing the VSD patch may tear and an unimportant left-to-right shunt may not be tolerated well in a patient with poorly compliant ventricles and/or pulmonary regurgitation. Residual VSD  A hemodynamically significant leak will result in elevated heart rate, left atrial equal to or exceeding RA pressure, and PA saturation (>80%). Findings such as these warrant investigation with echocardiography and early reoperation is required. RV outflow tract (RVOT) obstruction  Post-repair right ventricular pressure may be satisfactory when measured in the operating room, but RVOT obstruction may become more apparent later.  Moderate amounts of residual RVOTO are often well tolerated in the early postoperative period but it is associated with development of ventricular dysrhythmias later.  A patient who has suboptimal postoperative recovery, with high RV/LV pressure ratio, may need to return to the operating room. If a transannular patch was not performed initially, it should be considered. Arrhythmias  Complete heart block  Right bundle branch block  Junctional ectopic tachycardia (JET)  Ventricular Arrhythmias A-Complete heart block  It is often transient.  3-5% patients.  A permanent pacemaker system may be required if CHB persists more than 2weeks. B- Right bundle branch block  RBBB can be expected on the postoperative ECG in all patients who have undergone a right ventriculotomy.  Peripheral conduction across the infundibulum is slowed. Rarely does this represent injury to the His-Purkinje system.  The presence of left anterior hemiblock may lead to complete heart block. AV pacing should be used in these patients . C - Junctional ectopic tachycardia (JET)  JET is a potentially serious rhythm which usually occurs in the early postoperative period.  ECG reveals AV dissociation with a rate as high as 200-230/min.  The very rapid ventricular rate and lack of atrial contribution to filling can produce hemodynamic compromise and cardiac output may be seriously affected . JET Management  Hypovolemia, anaemia and metabolic abnormality (hypokalemia, hypocalcemia, hypomagnesemia) should be corrected.  Induction of hypothermia or at least correction of fever, suppresses automaticity and may slow JET. This entails use of cooling blankets, ice bags, cold gastric lavage, sedation with fentanyl, and muscle relaxation with vecuronium. A decrease in core temperature to 34 degree will reduce HR to 150-160/min (provided there is no metabolic acidosis.  Reduction in catecholamines ,  Atrial pacing to restore AV synchrony; such as overdrive atrial pacing to induce 2:1 or paired ventricular pacing may be effective. JET Management  Medications : 1-Digitalization may lower the rate. 2-Amiodarone: (oral or IV) to lower the ventricular response and convert JET to normal sinus rhythm. 3-Procainamide: type IA antiarrhythmic agents 4-- Others agents: propafenone (IV), propanolol and verapamil. They may slow the rate or induce 2nd degree A-V block which slows the ventricular response.  In extreme cases when JET is refractory, emergent cryoablation for the His bundle. D- Ventricular Arrhythmias  Ventricular arrhythmias may lead to late sudden death.  This is usually the result of reentrant ventricular tachycardia arising from the site of ventriculotomy scar.  Patients with ventricular ectopy and residual RVOTO are at the greatest risk for VT. Sum-up  Don’t extubate the patient with heomdynamic instability and low CO.  Do echocardiography within the 1rst day of postop to assess RV compliance and restrictive physiology pattern, residual shunt, RVOTO.  Volume augmentation and maintain high CVP in patient with poor RV function.  Early decision to add milrinone once sign of low CO was evident. Thank You