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Congenital heart disease

This document discusses the classification and pathophysiology of congenital heart disease. It covers the different types of shunts including simple shunts with increased pulmonary blood flow, complex shunts with associated obstructive lesions, and the physiologic classification of acyanotic and cyanotic defects. Key aspects of anesthetic management are summarized, including preoperative evaluation and optimization of pulmonary and systemic vascular resistances to balance blood flow depending on the type of shunting present. Choice of induction agents, inhalational anesthetics, and postoperative care are also addressed.

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Dr Kiran Rajagopal DA DNB. Anaesthesiologist CONGENITAL HEART DISEASE
Classification Simple Shunts Obstructive lesions Complex shunts
Physiologic classification Acyanotic Cyanotic Increased pulmonary blood flow Normal pulmonary blood flow Increased pulmonary blood flow Decreased pulmonary blood flow
Classification
The Five Ts of Cyanotic Congenital Heart Disease Tetralogy of Fallot Transposition of the great arteries Truncus arteriosus Total Anomalous Pulmonary Venous Return Tricuspid Atresia First and last have decreased pulmonary blood flow
Shunt lesions Cardiac shunting is the process whereby venous return into one circulatory system is recirculated through the arterial outflow of the same circulatory system Flow of blood from the systemic venous (right) atrium (RA) to the aorta Flow of blood from the pulmonary venous (left) atrium (LA) to the pulmonary artery (PA) Pathophysiology of congenital heart disease
• Recirculation of blood produces a physiological shunt • In an anatomical shunt, blood moves from one circulatory system to the other via a communication at the level of the cardiac chambers or great vessels • Physiological shunts can exist in the absence of an anatomical shunt. Eg TGA
Plumbing principle • Laws which govern the flow across a shunt - Ohms law - Hagen Poiseuille • Combination & modification of both results in plumbing principle
Q α P x D4 R • Q = Blood flow • P = Pressure gradient • D = Diameter • R = Resistance to blood flow
P1 P2 QP1 > QP2 QD1 > QD2D2D1 R1 L1 R2 QR1 > QR2 QL1 > QL2L2 Plumbing principle More flow through VSD than ASD More flow through a non restrictive VSD than a restrictive VSD Flow depends on the vascular resistance of the bed distal to the shunt Flow is more through shorter than longer tubes (PDA, Artificial conduits)
Simple shunts • No associated obstructive lesions eg ASD • Outflow resistance = SVR & PVR
Shunt depends on balance between SVR and PVR Pulmonary vascular resistance Systemic vascular resistance Low High Pulmonary flow increases L  R shunt
Balance between SVR and PVR Pulmonary vascular resistance Systemic vascular resistance Low High Systemic flow increases R  L shunt
Complex shunts • Fixed outflow obstruction present @ valvular, subvalvular, supravalvular level or in major vessals eg TOF
Complete obstruction and shunt Complete obstruction to flow of blood Shunting proximal to obstruction occurs A downstream shunt provides flow to the obstructed side of circulation.depends on SVR & PVR Eg PS with ASD & PDA
Manipulation of PVR & SVR Ventilatory control PVR can be controlled independently of SVR by adjusting ventilation Anesthetics and PVR Ketamine & N2O increase PVR in adults Not in infants with normal or increased PVR Large doses of opiods attenuate stress response in pulmonary vasculature to noxious stimuli like intubation Adequate depth also decrese stress response in pulmonary vasculature Manipulation of SVR Iv vasopressors are shunted R – L directly into the systemic circulation  Increases SVR and decreases R – L shunt Proximal aortic pressure can be increased by partially occluding aorta with a clamp
Acyanotic with increased PBF: ASD, VSD, PDA: Simple L – R shunt Left sided pressures > right sided pressures L – R shunt Volume loading of cardiac chambers Increased LAP Congestive heart failure Pulmonary congestion Decreased cardiac output Systemic hypoperfusion Coronary ischemia Increased work of breathing and pulm edema
L – R shunt Pulmonary congestion and edema Systemic hypoperfusion Congestive heart failure Failure to thrive Poor weight gain Diaphoresis Hypotension Tachycardia Acidosis Dyspnea Lengthy feeding Frequent RTI
Cyanotic with decreased PBF Right to left shunting of blood due to obstruction to pulmonary blood flow Hypoxemia and Cyanosis Polycythemia Altered hemostasis Microvascular thrombosis Growth retardation Myocardial dysfunction Poor tissue perfusion Renal and cerebral thrombosis Acidosis
Anesthetic management Type of surgical procedure Nature of the defect Cardiac & respiratory reserve Uncorrected Palliated Corrected Hypoxemia Pulm infection Cardiac failure Arrhythmias
Indices of critical impairment in congenital heart disease • Chronic hypoxemia (arterial saturation < 75%) • Pulmonary to systemic blood flow ratio > 2:1 • Left or right ventricular outflow tract gradient > 50 mm Hg • Elevated pulmonary vascular resistance • Polycythemia (hematocrit > 60%)
The 4 potential complications of CHD in children Arrhythmias Cardiac failure Cyanosis Pulmonary hypertension
Arrhythmias Supraventricular Ventricular • Atrial arrhythmias after repair of ASDs • Damage to AV node and bundle of His after a ventriculotomy or with RV to PA conduit Heart block  After TOF repair
Pre anaesthetic evaluation Ask for -Feeding difficulties -Vomiting -Lethargy -Increased perspiration -Rapid respiration -Hypoactivity -F.T.T -Fever -Cyanotic spells -puffiness of eyes In older child -Dysnea on exertion. -Shortness of breathing. -Orthopnea. -Lower limbs swelling -Palpitation. -Convulsion. -Cyanosis -frequent infections Medications,allergies Past hospitalisation and surgeries
Physical examination • Congestive heart failure will inhibit age- appropriate gains in weight, height and head circumference • Cyanosis • Clubbing • Tachypnea
CVS • organic murmurs CNS • Convulsions • Signs of raised intracranial tension • An unsettling fever – cerebral abscess Respiratory Increased PBF • Crepitations • Wheeze • Bronchial breathing signifies consolidated lungs
Airway examination • Airway abnormalities common – Pierre Robin, Treacher Collins, Down’s • Tracheal stenosis – Previous prolonged intubation after cardiac surgery – Vascular rings – Compression by enlarged CVS structures as well as artificial conduits
Establish room air saturation in all cyanotics
Laboratory data • Hb • Blood routine • Coagulation profile • Electrolytes • Arterial blood gases • X ray chest • ECG • ECHO • Cardiac cath
Continue cardiac drugs • Unrepaired cyanotic CHD, including palliative shunts and conduits • Completely repaired congenital heart defect with prosthetic material or device, whether placed by surgery or by catheter intervention, during the first 6 months after the procedure • Repaired CHD with residual defects at the site or adjacent to the site of a prosthetic patch or prosthetic device (which inhibit endothelialization) Avoid air embolus.Use air trapsInfective endocarditis prophylaxis •Prosthetic cardiac valve •Previous IE •Cardiac transplantation recepients who develop valvulopathy
NPO Guidelines • 2hrs for clear liquids • 4 hours for breast milk • 6hrs for formula • 8hrs for solid food • IV hydration during NPO • Minimum NPO time Dehydration • deleterious effects on haemodynamics • Increase blood viscosity in polycythemic patient (cyanosis with Hct>60%)
Premedication • Balance between agitation and respiratory depression • Oral midazolam 0.5-1 mg/kg • + oral ketamine 5-7 mg/kg • Im ketamine 4-5 mg/kg +glyco 10- 20ug/kg+midaz 0.1mg/kg
Induction intravenous For patients with • severely limited haemodynamic reserve, ventricular failure or pulmonary HTN • Start an inotrope if severe haemodynamic instability anticipated inhalational • Suitable if stable ventricular function and haemodynamic reserve • In R – L shunt length of induction is prolonged  airway is only partially controlled  short intervals of obstruction or hypoventilation  hypoxemia
CHD FOR NON CARDIAC SURGERY INTRAVENOUS INDUCTION TIME C O N C E N T R A T I O N
• Fentanyl 15-25 ug/kg + pancuronium 0.2 mg/kg Good haemodynamic stability Prompt airway control Attenuates inc PVR due to intubation • Vecuronium or cisatracurium may also be used • Ketamine 1-3 mg/kg is an alternative • Atropine or glycopyrrolate given
Maintenance • Fentanyl + inhalational agent ( sevo 1-2%) • Avoid nitrous - risk of airbubbles -Pulmonary HTN • Use air to reduce FIO2
L – R shunt Avoid decrease in PVR Avoid increase in SVR • High FIO2 • Hypocapnia • Respiratory alkalosis • Low hematocrit • Vasodilators • Light planes of anesthesia • Vasoconstrictors
R – L shunt Avoid increase in PVR Avoid decrease in SVR • Hypoxia • Hypercapnia • Acidosis • High airway pressures • PEEP • High hematocrit • Inadequate anesthesia • Hypothermia • Anesthetic agents which cause hypotension • Hypovolemia Avoid increase in systemic oxygen demand
Choice of anaesthetic agents Inhaled agents Immature cardiovascular system Decreased reserves • Halothane ( 1& 1.5 MAC) depresses heart more than sevo/iso/fentanyl+midazolam • Sevoflurane – less depression & low risk of arrythmias
Nitrous oxide • Controversial -enlarges air embolus -increase PVR • However, increases in pulmonary artery pressure or PVR in infants given 50% nitrous oxide do not occur, regardless of pre - existing PVR.
IV agents • Provides a larger margin of safety R – L shunts • Very high transient ,arterial,cardiac,brain concentrations occur when normal doses are given as rapid infusion -pulmonary circulation is bypassed • Normal doses of lignocaine,barbiturates,beta blockers may become toxic
Ketamine • 2 mg/kg IV in premedicated infants and young children does not increase pulmonary artery pressure or PVR, even when the baseline PVR is elevated. • Ensure that the airway and ventilation are carefully maintained hypoventilation or apnea PVR increases due to change in PaO2 & PaCO2
Opioids • High - dose opioid anesthesia excellent cardiovascular stability in children with CHD No significant changes in pulmonary and systemic hemodynamics • Fentanyl (25 – 75 μ g/kg) and sufentanil (5 – 15 μ g/kg) • Pancuronium - muscle relaxant of choice with high dose opiods
Propofol • Reduces SVR with no effect on PVR • Deleterious in R – L shunt Etomidate • Does not alter hemodynamics or either R – L or L – R shunt • Minimal cardiovascular and respiratory depression • Alternative to the synthetic opioids for induction of patients with limited myocardial reserve
Post operative care • Adequate pain relief – Pain increases SVR and PVR – Pain worsens infundibular spasm of TOF • Avoid respiratory depression • Use regional analgesia wherever applicable – Caution in cyanotics (coagulopathy) – Can decrease SpO2 in R – L shunts – Hazardous in left sided obstructive lesions
Ventricular septal defect • An opening in the ventricular septum that permit communication between RV and LV • Membranous or perimembranous type most common (80%) • Subpulmonary or supracristal type • Muscular defects
• Ventricular septation 5- 7 weeks • The primordial interventricular septum arises from a median muscular ridge between the right and left ventricular masses. • Increased growth and dilation of the ventricles, combined with fusion of the medial ventricular wall, result in enlargement of the muscular ventricular septum • The membranous portion of the septum is derived from tissue ingrowth from the right side of the endocardial cushion to the muscular region of the interventricular septum.
Haemodynamics
CVS  holosystolic or pansystolic murmur  ESM at pulmonary area due to ↑ pulmonary flow  Diastolic rumble at the apex  left ventricular heave  laterally displaced apical impulse  S1 accentuated  S2 wide & variable split varies with respiration
ECG • LVH • RVH • All children are born with RVH • RVH regresses more slowely in VSD • Develops LVH • With the onset of PAH RVH also seen
CXR • Pulmonary plethora • Cardiomegaly • In Eisenmenger syndrome loss of pulmonary vascularity and pruning of the vasculature.
Course & complications • CCF in infancy • Spontaneous closure in 70% cases • Spontaneous closure occurs by 3 yrs, or as late as 20 yrs • Pulmonic Stenosis– due to hypertrophy of Rt ventricular infundibulum • PAH
Cardiac grid Lesion Preload PVR SVR HR Contractility ASD Normal Normal VSD Normal Normal PDA Normal Normal Coarct Normal Normal Normal TOF
ATRIAL SEPTAL DEFECT • Communication between the atria due to the deficiency of tissue in the septum Anatomic types • Defect at the fossa ovalis( ostium secondum • Partial AV canal defects( ostium primum) • Sinus venosus defects • Coronary sinus defects . Anatomic types s
Haemodynamics • L R shunt • RAE • Large volume of blood through normal TV DDM • RVH • Large volume of blood through normal PV ESM • Pulmonary artery and its branches enlarge • PAP remains normal and PVOD occur in 4 th or 5 th decades
Physical examination  A wide and fixed split of S2  A loud P2 indicates pulmonary hypertension  A systolic ejection murmur, of soft intensity is best heard at the upper LSB  A diastolic rumble heard at the lower left sternal border.  A pansystolic murmur of “mitral” regurgitation is present in primum ASD.
Clinical picture  Commonly asymptomatic  Mild effort intolerance and chest infection may be the presenting complaint  Heart failure is rare in childhood
CVS  Left parasternal impulse  Mild to mod cardiomegaly  S1 – normal or mild accentuation  S2 – fixed and wide split without respiratory variation  ESM gd 3 or less at Left 2nd ICS  Low – medium pitched early diastolic murmur at the left lower sternal border
ECG  Secundum ASD—RT axis deviation & RVH  rsR’ in V1 – characteristic ( indicates RV conduction delay)  primum ASD – left axis deviation  First degree heart block in primum ASD  RVH
CXR can be normal in early stages +/- when the ASD is small  signs of increased pulmonary flow (shunt vascularity) enlarged pulmonary vessels upper zone vascular prominence vessels visible to the periphery of the film eventual signs of PAH chamber enlargement right atrium right ventricle
Cardiac grid Lesion Preload PVR SVR HR Contractility ASD Normal Normal VSD Normal Normal PDA Normal Normal Coarct Normal Normal Normal TOF
PDA • Most common extracardiac shunt • Connects the main pulmonary trunk near the origin of the left PA with the proximal descending aorta just distal to the origin of the left subclavian artery • Left RLN lies in close relation
Haemodynamics • L  R shunt • Flow during systole & diastole pressure gradient present throughout cardiac cycle • Continuous murmur – starts after S1 peaks at S2 & diminishes in intensity during diastole
Systolic & diastolic overloading of PA Blood passes through Lungs to LA LA enlarges Blood passes through normal mitral valve into LV Loud S1 DDM Diastolic overoad of LV LV enlarges LV systole prolonged Delayed aortic valve closure Late A2 Large volume into aorta aortic ejection click ESM
Clinical features • History of maternal rubella in 1st trimester • Common in premature infants with h/o of birth asphyxia, respiratory distress • Symptomatic early in life • Heartfailure at 6 - 10 weeks • Older children – effort intolerance,palpitation ,chest infection
CVS • wide pulse pressure • Hyperkinetic cardiac apex • Thrill at 2nd left ICS • S1 attenuated • S2 narrow split, paradoxical split with large shunts • Continuous murmur L 2nd ICS or below clavicle • S3 & delayed diastolic murmurs with large shunts
CXR • • Cardiac enlargement • LA, LV enlargement • Cardiac size depends on shunt
ECG • LVH • Deep Q with increased R wave voltage in left precordial leads - LV volume overload • RVH in pulmonary HTN
Complications • Heart failure • Pulmonary HTN • Pulm HTN  R – L shunt  differential cyanosis • Infective endocarditis Surgical complications • Bleeding during surgery ,if control of PDA lost during ligation • Post ligation- systemic HTN Mx – infusion of vasodilators • Injuries to left RLN, left phrenic , thoracic duct
Tetrology of fallot • Most common cyanotic cardiac lesion • The four constituents are • VSD • RVH and RVOT Obstruction • Overriding aorta • Pulmonary stenosis and pulmonary hypoplasia
Haemodynamics • Pulmonic stenosis  conc RVH  increase in RV pressure. • R  L shunt occurs as RV pressure equals LV pressure • R  L shunt is silent becase the flow occurs at insignificant pressure difference • Flow into pulmonary stenosis  ESM • More severe the pulmonic stenosis  shorter the murmur more R L  more cyanosis • soft & inaudible P2
Pathophysiology RVOT Obstruction + VSD R to L shunt Arterial Desaturation (Decreased pulmonary blood flow) Chronic Cyanosis Polycythemia Embolic Stroke Brain Abscess / Endocarditis
Cyanotic spells • Episodes of paroxysmal dypsnea with marked cyanosis. • These spells are usually self limiting but can lead to brain damage or even death. • It results from drastic reduction in pulmonary blood flow, with increase in Rt  Lt shunt and decrese in Po2
Cyanotic spells- mechanism • Exact mechanism is not known but the following postulates are given: • Increase in infundibular contractility • Peripheral vasodilatation • Hyperventilation
Cyanotic spells- mechanism • Increase in infundibular contractility-results in decreased pulmonary blood flow due to increased nor adrenaline level • Peripheral vasodilatation →increase in right to left flow → decrease in pulmonary blood flow • Hyperventilation-- Cry→sudden rise of cardiac rate & output→venous return in presence of relative fixed pulmonary outflow obstruction→R→Lshunt→pO2/pH,pCO2→Respiratory centre response→ Hyperpnea→cardiac o/p still further
Treatment  Oxygen  Calm and comfort child  Knee-chest position  - - Compresses femoral arteries & inc SVR  Morphine(0.05–0.10 mg/kg)  --- May directly relax infundibulum,/action on CNS  Intravenous fluids (10-15 ml/kg)  Bicarbonate (1-2meq/kg)  Beta-blocker ( propranalol 0.1 mg/kg or esmalol 0.5 mg/kg followed by 50-300 mcg/kg/min infusion)  Vasoconstrictor (phenylephrine 5-10mcg/kg bolus or 2-5 mcg/kg/min infusion  External compression of abdominal aorta  General anesthesia with ETT  Hyperventilation with FiO2 1.0 to reduce PVR
Pink tet • A small subset of TOF patients have minimal obstruction to pulmonary blood flow at the right ventricular outflow and PA level and may have normal oxygen saturation. • Some of these patients have a L–R shunt with increased pulmonary blood flow and symptoms of CHF.
Clinical picture  History & Clinical examination  Tachycardia  Low height and weight for age  Clubbing of fingers and toes  Systolic thrill along left parasternal border  Parasternal lift  Systolic ejection murmur  Single S2  ESM at left upper strenal border
CXR • Small to normal heart size • Decreased pulmonary vascular markings • Heart apex upturned (“Boot- shaped”) • Concave left upper border • Large Aorta • Right-sided aortic arch in 1/5 of patients • Right ventricular hypertrophy causes the left ventricular apex to be uplifted and cause cardiomegaly. In addition, the pulmonary artery segment shadow, usually noted just above the left atrial appendage shadow is not present due to small pulmonary arteries. This give the characteristic "Boot shape" appearance of the cardiac silhouette.
ECG • Right axis deviation • RVH
Complications • Effort intolerance • Anemia aggrevates dyspnoea • Infective endocarditis • Anoxic infarction in CNS • Paradoxical embolism hemiplegia • Venous thrombosis due to polycytemia • Brain abscess
Surgical Management Shunts • Modified Blalock-Taussig ( subclavian to pulmonary) • Blalock-Taussig Full repair • Transanular patch • Valved conduit
Cardic grid
References  STOELTING CO EXISTING DISEASES  OP GHAI PAEDIATRICS  GREGORYS PAED ANAESTHESIA  DINARDO CARDIAC ANASTHESIA  THE HEART – HURSTS
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LA  LV  Aorta  Ductus arteriosus Foramen ovale RV SVC  upper body IVC 50% through 50% to ductus venosus Portal circulation Umbilical Vein Oxy.blood PLACENTA
Aorta Deoxygenated blood Descending aorta Abdominal aorta Common iliac artery Umbilical arteries PLACENTA Oxygenation Umbilical Vein
• COURSE OF FETAL CIRCULATION: • Most of SVC blood (less oxygenated blood) goes into RV. • Most of IVC blood (high O2 concentration) is directed by the Crista Dividens to the LA through Foramen ovale. • Rest of IVC blood enters RV & pulmonary artery. • Less oxygenated blood in Pulmonary artery flows through Ductus Arteriosus to descending aorta and then to placenta for oxygenation.
• COURSE OF FETAL CIRCULATION: • The Result is: • Brain and coronary circulation receive blood with higher concentration (PO2 = 28 mm Hg) than the lower part of the body (PO2 = 24 mm Hg)
• FETAL CIRCULATION: The pathway: Placenta  Oxygenated blood  Umbilical vein Hepatic circulation Bypasses liver & joins IVC via ductus venosus Partially mixes with poorly oxygenated IVC blood derived from lower part of fetal body
Congenital heart disease