Pathophysiologic Consideration In Patients With Congenital Heart Disease SAMIA SHARAF .MD Professor Of Anaesthesia .. Ain Shams University
Classification Of Congenital Heart Lesions • Obstructive lesions eg. Aortic stenosis – coarctation of aorta • Increased pulmonary blood flow eg. ASD – VSD – PDA • Decreased pulmonary blood flow lesions eg. Tetralogy of fallot – tricuspid atresia – pulmonary atresia
Clinical Presentation Of Children With CHD • Cyanosis ( due to hypoxia ) • Respiratory system abnormalities • Cardiac failure • Arrhythmias
Cyanosis Pathophysiologic Effects of Hypoxia (1) Growth (2) Heart • Exercise intolerance : myocardial dysfunction ventricular compliance and contractility • Irreversible myocardial damage . • Increased sympathetic tone down regulation of beta receptors cardiomyopathy
(3) Hematology • A major adaptive response to chronic hypoxia Red cell mass Polycythemia Secondary Spherocytosis • Blood viscosity • Risk of thromboembolic events
Hemostasis : Polycythemia Coagulation abnormalities Primary fibrinolysis DIC
Mechanism of coagulation abnormalities Increased blood viscosity DIC Hypercoag. blood & tendency to bleed Increase intravascular strains Thrombocytopenia & Low Fibrinogen & Other Factor Level Fibrin deposition & platletaggreg. Consumpution of platlets , fibrinogen , factor V , VIII
(4) CNS • Chronic hypoxia causes impairment of neurologic development and increase risk of neurologic damage . • Brain abscess : Rt. – Lt. shunt • Cerebrovascular thrombosis and hemorrhage .
Respiratiry System Abnormalities • Anatomical abnormalities of airway • Pulmonary abnormalities associated with or pulmonary blood flow .
Anatomical Abnormalities Of Airway • Short trachea eg. interrupted aortic arch • large airway obstruction : ( trachea & bronchi ) • Compression by enlarged aorta or pulmonary artery . • Upwards displacement and increase angle of bifurcation of trachea by enlarged LA .
Small airway obstruction : • Compression of lung parenchyma by enlarged heart and vessels . • Pulmonary hypertension .
Pulmonary Changes Associated With Pulmonary Blood Flow Patients with chronic hypoxia • Slight of alveolar ventilation • pulmonary venous PO2 is high • V/Q mismatch alveolar – pulmonary venous O2 gradient • Physiological dead space end tidal CO2 is lower than arterial PaCO2
Pulmonary Changes Associated With Pulmonary Blood Flow • Obstruction of small airway • Pulmonary congestion pulmonary compliance , lung water & Impaired gas exchange • Progressive of pulmonary vascular resistance due to hypertrophy in muscular layer of pulmonary arteries reverse of left to right shunt
Cardiac Failure Causes of limited cardiac reserve : (1) Increased cardiac workload Pressure overload : ventricular outflow tract obstruction SVR blood viscosity Volume overload : * Valvular insufficiency * Single ventricle * Left – right shunt
(2) Myocardial contractility: • Prolonged workload of myocardium • Vascular supply to ventricles • Blood hyperviscosity • Chronic hypoxia
Compansatory Mechanism • Ventricular hypertrophy • Adrenergic system changes Activation of B receptors • Renal system compansation *Salt & water retention *Renin secretion
Arrhythmias Types : * Congenital * Acquired Etiology : • Intrinsic electrophysiology abnormalities • Damage from chronic hypoxia – hemodynamic stress • Surgical injury eg. F4 , Fontan operation , atrial correction of TGA
Congenital Conduction System Abnormalities • Congenital complete atrioventricular block • Wolf – Parkinson white syndrome • Supraventricular tachycardia • Arrhythmias associated with Ebstien anomaly
Acquired Conduction System Abnormalities • Non surgical : rare • Surgical by : * cardioplegia * mechanical retraction * ischemia * metabolic abnormalities
Anaesthetic Risk factors affecting anaesthetic risk in congenital heart disease Pulmonary disease Cyanotic heart disease Myocardial dysfunction Cardiovascular impairment Arrhythmias Magnitude of surgery Anaesthetic risk
Role Of Surgeon • Case discussion : • Pts. with CHD may not tolerate : • Abdominal laparoscopic procedures • ( eg. stenotic valvular lesions , single ventricle ) • Absorption of CO2 ( C.O.P dependant low PVR) . • One lung ventilation • Prone position ( Fontan pt. )
Role Of Pediatric Cardiologist Preoperative consultation sometimes add a little benefit to anesthiologist !!!!!
Base line O2 saturation Vital data Murmurs Gallops Pulse in extremities Planned followup as needed 2-3 months interval New echo Unstable pt. Major operation History data exact anatomy Previous cardiac operation Myocardial function status Pediatric cardiologist consultation
History Taking • Growth • Exercise Intolerance • Recurrent Chest Infection • Syncopal Attacks • Squatting
ECG , Echo & Cardiac Cath. Systolic & Diastolic Dysfunction Systolic Dysfunction Reduced Fractional Shortening
Diastolic Dysfunction Ventricular Hypertrophy Concentric Eccentric Obstructive Volume Before Repair e.g valvular & outflow obst. After Repair e.g Homograft conduit Before Repair e.g Lt . to Rt. shunt • After Repair • e.g • Pulmonary valve regurge • ( F4 ) • MV repair
Anaesthetic considerations : Consider determinants of coronary perfusion & myocardial oxygen balance • Heart rate changes • Hypotension • Myocardial contractility
Anaesthetic considerations CONCENTRIC Ventricular Hypertrophy Eccentric Ventricular Hypertrophy Cardiomyopathy increase wall thickness Maintain heart rate to decrease regurgitant fraction Syst. Dysfunction In Dialted type anaesthetic myocardial depression Decrease driving filling pressure of coronary arteries Coronary ischemia Diast. Dysfunction In Hypertrophic & restrictive type coronary perfusion depends on bl. p. & hr RV LV coronary filling becomes diastolic
Residual Shunts : • Occasionally present after repair of ASD , VSD & F4 • Small patch leaks are hemodynamically benign
Dysrhythmias : Atrial & ventricular types increase mortality and morbidity Arrhythmias Associated With Specific Surgical Procedures Ostium secondum ASD : • P-R interval is prolonged in 20-30% of patients • AF , atrial flutter with advancing age
VSD : • RBBB • Atrial ectopic , junctional beats , premature ventricular beat • Late onset of complete heart block or ventricular arrhythmias are rare Repair of F4 : • RBBB & complete heart block Mustard or Senning operation : • Sinus nodal dysfunction • Bradycardia • A-V block , AF
Pulmonary hypertension Severity of hypertension of base line PAH correlated with the incidence of major complications ( pulmonary hypertensive crisis or cardiac arrest )
Cardiovascular risk of PAH • Major perioperative hemodynamic deterioration mainly pulmonary hypertensive crisis and acute right ventricular failure and cardiac arrest . • Data to look for : • Mean pulmonary artery pressure > 25 mmHg • Severity of base line PH : • Subsystemic PAP < 70% of syst. bl. pressure • Systemic PAP = 70 – 100 of syst. bl. pressure • Suprasystemic PAP > 70 of syst. bl. pressure • ( based on mean pressures )