580 CHAPTER 11 Invasive electrophysiology Mechanism of ventricular tachycardia The improved survival from MI and widespread use of IC Ds has led to a much greater need for invasive management of VT, i.e. ablation. In structur al heart disease, VT almost always has a re-entry mechanism. Normal heart VT may be focal o r re-entry. Structural heart disease (see Fig. 11.13 ) Scarred ventricular myocardium (due to infarctio n, cardiomyopathy etc.) provides the substrate for re-entry as described previously (see b p. 524). Scar acts as a barrier to conduction ( \201 xed block); however, damaged but viab le myocardium will provide areas of slow conduction, which are critical to allow re-entry c ircuits to form. This acts as a source of wavefronts that repeatedly depolarize the rest of the ventricle \200\224 hence monomrphic VT. LV scarring is much more common than RV other than in ARVC. A stable re-entry circuit can break down into chaotic activa- tion, i.e. VF, hence the link between VT and sudden death. Bundle branch VT occurs in severely impaired v entricles, with damage to the conducting system and usually pre-existing bundle branch bloc k. It is due to a re-entry circuit involving the right and left bundles. Normal heart VT RV (and LV) out \202 ow tract VT has a focal mechanism with cells exhibiti ng enhanced automaticity. Fasicular VT is probably a re-entry circuit within either the pos terior (usually) or anterior (rare) hemifascicles of the left bundle. MECHANISM OF VENTRICULAR TACHYCARDIA 581 D A 2 0 1 0 Fig. 11.13 Mechanism of VT in structural heart disease, e.g. post-MI. An area of scar in th e LV myocardium (black) provides \201 xed conduction block. Electrical wavefronts (arrows ) rotate around and slowly through the scar to form a re-entry circuit. This acts as a sour ce of wavefronts to the rest of the ventricle. The area of slow conduc- tion (zig-zag arrow s) is termed the diastolic pathway as it activates during ventricular diastole. During VT, intracardiac electrograms recorded here time with the midpoint between successive QRS compl exes. This is the target for ablation of VT. 582 CHAPTER 11 Invasive electrophysiology Ablation of ventricular tachycardia Clinical indications \200 Recurrent symptomatic parox ysms of VT \200 To reduce the number of therapies delivered by an automated ICD (AICD) \200 Incessant VT Activation mapping VT (see Fig. 11.14) To successfully map the re-entry circuit, the patient must be in VT and therefore it needs to be haemodynamically well toler ated. Remote de \201 - brillation paddles are attached to the patient so that if VF or hyp otensive VT occurs, it can be immediately cardioverted. If feasible, the LV is accessed both retrogradely via the femoral artery and aortic valve a nd anterogradely via the femoral vein and a trans-septal puncture. Using a 3D mapping syste m, the ablation catheter is moved around the LV, recording ICegrams at different sites and timing them to a stable \201 xed reference. The aim is to identify the critical diastolic pathway at which the circuit is most susceptible to destruction. Entrainment of VT This can only be performed on tachycardias with a re-entry mechanism. The ablation catheter is moved around the ventricle to sites where the circuit is expected (i. e. adjacent to areas of scar). By pacing with this cath- eter at a rate just faster than th e tachycardia cycle length, a VT is entrained if it is following the same circuit but at a faster rate. If the ECG during pacing is a 12/12-lead match to the clinical VT, then this i s concealed entrainment. This implies the pacing catheter is within the critical diastolic portion of the circuit. To con \201 rm this when pacing is stopped, the return cycle lengt h (the time from the \201 nal paced beat to the next activation at the catheter) should b e almost identical to the tachycardia cycle length. Ablation technique The standard steps of a VT ablation are: \200 induce VT (Wellen \200 \231s); ensure it is similar to clinical VT and well tolerated \200 map VT to identify th e critical diastolic pathway: very early local ICegram occurring mid-diastole (50 \200\223150 ms ahead of ECG) concealed entrainment during pacing \200 return cycle length (=post pacing interval) < ta chycardia cycle length + 30 ms. deliver RF energy via an irrigated catheter (for deeper lesion) at the site meeting the criteria above if VT is terminated, attempt to reinduce. Substrate ablation of VT If VT is not haemodynami cally tolerated or cannot be induced, then acti- vation and entrainment mapping cannot be p erformed. An alternative is to use a 3D mapping system to create a map of the LV during sin us rhythm. The map displays the voltages of the ICegrams, and hence areas of scar are ident i \201 ed. The re-entry circuit of the clinical VT can be estimated from the 12-lead ECG a nd by pacing at sites on the edge of scar, which, if they are the location of the re-entry circuit driving VT, will give a similar ABLATION OF VENTRICULAR TACHYCARDIA 583 12-lead ECG appearance to the clinical VT. Ablation is delivered between two areas of \201 xed conduction block (scar, mitral annulus) to interrupt theoretical re-entry circuits . Failed ablation If conventional ablation fails, alternative approaches are: \200 ablate t he epicardial surface of the heart by delivering the catheter via the pericardium (as for a pericardial aspiration) alcohol ablation via a small terminal coronary branch subtending the scarred area supporting re-entry. Hence, give the patient a controlled, small MI that destr oys the critical portion of the re-entry circuit cardiac surgical ablation. + 160 Arterial 0 HRA HBEp HBEd RVA I aVF Fig. 11.14 An induced VT at a cycle length of 320 ms (187/min). From top to bottom, a traci ng of arterial pressure, high right atrial ICegram, proximal then distal His bundle ICegram , RV ICegram, then two suface ECG leads. There is no V to A conduction at this rate and the atrium is dissociated form the ventricle. Despite the rapid rate, the systolic BP is maint ained at 100 mmHg, enabling the VT to be mapped if necessary. 584 CHAPTER 11 Invasive electrophysiology Automatic implantable cardioverter de \201 brillators Mirowski implanted the \201 rst au tomatic implantable cardioverter de \201 bril- lator (AICD) in 1980 to manage SCD. Since t hen there has been dramatic improvement in technology, and randomized controlled trial evid ence to support their use in primary and secondary prevention. Initial devices were large a nd placed surgically in abdominal pockets attached to epicar- dial leads. AICDs are now imp lanted in the same way as pacemakers and are often part of a biventricular pacing system. Components The bulk of an AICD box is the battery and capacitors that generate and store th e energy to deliver a de \201 brillation shock. The box is attached to a ventricular \200 \230shock \200\231 lead and often an atrial \200\230pace-sense \200\231 lead. The V lead c ontains one or two shocking coils and a bipolar set of pacing electrodes at its tip. This b oth senses electrograms and can deliver low-voltage pulses to pace the heart if it is too s low (bradycardia pacing), or overdrive if it is too fast, e.g. a ventricular tachycardia (a ntitachycardia pacing, ATP). Microprocessors contain the algorithms that interpret the sens ed elec- trograms to: (1) detect tachycardias; (2) discriminate VT/VF from non- life-threat ening arrhythmia (e.g. AF); (3) deliver therapy. These algorithms contain features that are both programmable and non-programmable. Implantation AICDs are implanted in the identical way to pacemakers and the same complicati ons occur (see b p. 530). A range of leads are available: active/passive, single coil/dual coil. Extra vigilance is needed over selecting a V lead position with good electrogram sens ing (ideally R wave > 10 mV). A de \201 brillation test should be performed once the devic e is implanted, as ventricular electrograms in VF will be of much lower amplitude than duri ng SR. The patient is sedated and, with the AICD switched on, VF is induced. The device is then observed to ensure it successfully detects and terminates VF. If the device fails, an external biphasic 360 J shock is delivered and the lead is repositioned. During testing, th e AICD is pro- grammed to its least sensitive detection and delivers an energy that is at l east 10 J below its maximum output. After the procedure, the AICD is programmed to its most sensitive detection and delivers shocks at maximum energy. In this way, there is a safety margin that reduces the chance of the device failing. AUTOMATIC IMPLANTABLE CARDIOVERTER DEFIBRILLATORS 585 Indications for AICD Class I \200 Survivors of cardiac arrest secondary to VT or VF when all reversible factors have been excluded (secondary prevention) Sustained VT and signi \201 cant structural heart disease (secondary prevention) Syncope of undetermined origin, structural heart disease, and sustained haemodynamically unstable VT or VF induced at EP study Previous MI ( > 40days) + LVEF \211 35 % with New York Heart Association (NYHA) class II \200\223III or LVEF<30 % with NYHA class I or LVEF<40 % and pos itive VT stimulation study. Note: all are for primary prevention Non-ischaemic cardiomyopathy (LVEF \211 35 % ) and NYHA class II \200\223III. Class IIa \200 Sustained VT and reasonable LV function \200 Hypertrophic cardiomyopathy (HCM) or ARVC and one or more risk factors for SCD VT or syncope in the presence of long QT syndrome, Brugada syndrome, or catecholaminergic polymorphic VT. Class III (AICD de \201 nitely not indicated) \200 Patients who are not expected to surv ive > 1 year \200 Signi \201 cant psychiatriac co-morbidity that may be worsened by implant or cause problems with follow-up VT/VF with a completely reversible cause (e.g. severe systemic sepsis with normal heart), o r normal heart VT that is amenable to curative ablation. Adapted from ACC/AHA/HRS 2008 guidelines. J Am Coll Cardiol 51: 2085 \200\223105. 586 CHAPTER 11 Invasive electrophysiology AICD programming Detection of tachycardias The AICD simply measures the intervals (cycle le ngth) between successive sensed ventricular electrograms, and hence measures ventricular ra te. If the rate enters a programmed zone (e.g. > 190 bpm), then tachycardia is detected. Mo st devices allow up to three detection zones, e.g. VT (170 \200\223200), fast VT (200 \200 \223230), and VF ( > 230). Each zone can be programmed with different ther- apies. If no th erapies are programmed, it is a monitor zone. Discrimination of SVT from VT/VF Not all tachycardias at a rate > 170 bpm are VT. SVTs such as sinus tachy- cardia, AVNRT, AVRT, atrial tachycardia, and AF can all reach a V rate > 1 70 bpm. Discrimination algorithms attempt to distinguish these non- life-threatening arrhyt hmias from VT/VF and prevent delivery of inappro- priate and painful therapy. Very fast V r ates, e.g. > 220 bpm are almost always VT/VF, and discrimination is not applied. Discrimination of SVT from VT/VF Discrimination algorithms in AICDs use a combination of the following parameters: \200 AV association V > A: always VT/VF \200 V=A: SVT or VT \200 V<A: likely AF or ATach; VT possible (eg A F and VT) Electrogram morphology in tachycardia Same as SR: SVT \200 Different from SR: VT or SVT + bundle branch block (BBB) Onset of tachycardia Sudden: SVT or VT \200 Gradual: sinus tachycardia Stability of VV intervals during tachycardia Not stable: AF or VF \200 Stable: SVT or VT. Therapies Once the device detects tachycardia and decides it is de \201 nitely VT or VF, i t will deliver one of two forms of treatment depending on how the zone has been programmed. Therapies are disabled in a magnetic \201 eld. Antitachycardia pacing (ATP) This is a burst of pacing that attempts to overdrive and termi nate VT, but is not effective for VF. The device delivers a set number of pulses (6 \200 \22312) at a \201 xed cycle length that is a percentage of the measured tachycardia cycle length (usually 81 % ). The sequences may be repeated with shorter cycle lengths (i.e. pac e faster). Within the burst of pacing, the cycle length can be shortened (=ramp pacing). If ATP fails to terminate VT, a shock is usually delivered. AICD PROGRAMMING 587 De \201 brillation AICDs deliver a maximum energy up to 41 J as a biphasic waveform from t he shocking coil on the RV lead to the pulse generator, which is an \200\230active can \200\231. The shocking vector travels superiorly from the RV, including most of the IV sept um and LV. If a dual-coil lead or separate SVC coil is implanted, the device can shock eith er between both coils or between the can and either coil. All programmed shocks should be a t the device \200\231s maximum output. 588 CHAPTER 11 Invasive electrophysiology AICD troubleshooting Follow-up The patient \200\231s AICD is interrogated every 6 \200\2231 2 months either in the clinic or remotely via wireless receivers installed in the patient \200\231s home. Checks are made on the lead parameters and battery life (to determine wheth er a box change is necessary). The arrhythmia log is reviewed to determine if there have be en any ventricular or atrial arrhythmias and any therapy delivery. Remote follow-up allows automatic downloads of important events (red alerts), e.g. episodes of VF, impending batter y failure, damage to the lead, etc. These are communicated directly to the AICD clinic by u rgent email or phone call. VT/VF storm This is de \201 ned by \211 3 appropriate shocks for VT/VF in <24 hours. Com mon causes are ischaemia, worsening heart failure, electrolye imbalance, change in medicati on, or intercurrent illness. Sometimes no obvious cause can be found, Patients should be ma naged in specialist EP centers for optimization of antiarrhythmic drugs, device programming , and VT ablation if necessary. Inappropriate shocks These are the most important morbidity associated with AICD and occur in 10 \200\22320 % of patients. A shock delivered in a conscious unsuspecting patient is ex tremely painful and frightening. Inappropriate shocks can lead to major psychiatric problem s of anxiety and depression. They are due to poor programming (human error), VT without hae modynamic compro- mise, AF with fast ventricular rates, other SVT, lead damage, or external interference (e.g. diathermy). In an emergency, a magnetic placed over the device will dis able therapies so the cause can be determined. Drug interactions Antiarrhythmic drugs may increase de \201 brillation thresholds (e.g. \202 ecainide, propafenone, amiodarone). They may also slow the rate of VT such that it no longer falls in the programmed detection zone. Care should be taken to ensure AICDs are sti ll effective after major drug alterations. End-of-life issues Patients with advanced heart disease may eventually reach a palliative p hase (NYHA class IV) or develop another terminal illness (e.g. cancer). After careful couns eling with the patient, family, and palliative care team, it may be appropriate to turn the rapies off or not to replace a box that has reached the end of its battery life. These are dif \201 cult decisions, and a multidisciplinary approach is necessary. It is important to be aware that devices will need to be turned off when patients have died, and explanted be fore cremation. 589 Chapter 12 Congenital heart disease Introduction 590 Assessment of patients with CHD (1) 592 Assessment of patients with CHD (2 ) 594 Speci \201 c signs in patients with CHD 596 Surgical operations for CHD (1) 598 Surg ical operations for CHD (2) 600 Percutaneous transcatheter interventions for CHD 604 Speci \201 c management issues 606 Pregnancy 608 Speci \201 c conditions (1) 610 Speci \201 c conditions (2) 612 Extra-cardiac complications 614 590 CHAPTER 12 Congenital heart disease Introduction Congenital heart disease (CHD) is one of the commonest congenital defects, occ urring in approximately 0.6 \200\2230.8 % of newborns. i.e. there are about 5000 newborns w ith CHD each year in the UK. Advances in therapy have led to a dramatic improvement in outc ome, such that over 85 % of infants, even with complex CHD, are expected to reach adolescen ce and early adulthood. As a result of the success of pediatric cardiology and surgery, the re are now more adults than children with CHD . In addition, there are patients with struct ural or valvular CHD who may present late during adulthood. It is estimated that there are approximately 1600 new patients per annum with moderate to complex CHD, of whom 800 might b ene \201 t from specialist follow-up in the UK. Most of these patients have had palliative or reparative rather than corrective surgery, and further cardiac operations will be neces sary for many. Role of specialist CHD centers \200 Initial assessment of adults with known or suspected CHD \200 Surgical and non-surgical interventions, e.g. transcatheter closure of atrial septal defect (ASD)/percutaneous valve implantation \200 Continuing care of patien ts with moderate and complex CHD \200 Advice and ongoing support for non-cardiac surgery and pregnancy \200 Training new specialists and providing evidence-based clinical decisio n making Providing feedback of late results to re \201 ne early treatment Transition from pediatric to adult care A smooth transition from the pediatric to the adult CHD specialist is essent ial. This should be tailored to the individual patient, with inbuilt \202 ex- ibility. Id eally, a speicialist transition clinic should be set up, with input from both the adult and pediatric services. Transfer to the adult unit should occur at around 18 years of age. Pat ient education about the diagnosis and speci \201 c health behavior, including contracepti on/pregnancy planning, should be included. Patient passports that include detailed diagrams of the individual cardiac defect and relevant information on topics such as exercise and n eed for antibiotic prophylaxis should be prepared for each patient . No patient with CHD should reach adulthood without a clear management plan. Treat adult CHD with respect. Many problems or errors arise from arrogance or ignorance. Th e patients may often know more about their condition and its management than the \200\230e mergency \200\231 medical team they consult; therefore be patient and listen. Patients are often accompanied by a parent/s even well into late teens/second or third decade. They can prove a great source of information and help; keep them on your side. Increasingly in the U K, adult congenital heart physicians are available for advice, either via email or by telep hone. None will refuse a call for help. Get to know your local specialist center! INTRODUCTION 591 Disease complexity and hierarchy of care for the adult with congenital heart disease Level 1 Exclusive care by specialist unit, e.g. Eisenmenger syndrome, Fontan repairs, trans position of the great arteries, any condition with atresia in the name, Marfan Level 2 Shared care with \200\230interested \200\231 adult cardiologist, e.g. coarctation of the aorta, ASD, tetralogy of Fallot Level 3 Ongoing management in a general adult cardiology unit, e.g. mild pulmonary valve st enosis, postoperative atrial/ventricular septal defect Information sources on adult congenital heart disease 1 . Management of grown up congenital heart disease. European Society of Cardiology Task Force Report. Eur Heart J 2003: 24 ; 10 35 \200\2231084. 2 . British Cardiac Society Report 3 . Canadian Taskforce Report. Congenital heart disease in adults Acyanotic lesions \200 Atrial septal defect b p. 610 \200 Ventricular septal defect b p . 278 \200 Atrioventricular septal defect b p. 610 \200 Pulmonary stenosis b p. 610 \200 Left ventricular out \202 ow tract (LVOT) Cyanotic lesions \200 Transposition of the great arteries b p. 612 Tetralogy of Fallot b p. 612 \200 Fontan patients b p. 613 \200 Congenitally corrected transposition of the great arteries b p. 613 obstruction b p. 611 Coarctation of the aorta b p. 611 \200 Anomalous pulmonary venous drainage Severe Ebstein \200\231s anomaly of the tricuspid valve b p. 613 b p. 611 Ebstein \200\231s anomaly of the tricuspid valve b p. 613 592 CHAPTER 12 Congenital heart disease Assessment of patients with CHD (1) History \200 Family history of CHD \200 Exposure to teratogens/toxins during pregnancy \200 CHD suspected during pregnancy or at birth (ask the mother!!) \200 History of prolonged childhood illnesses \200 Prior interventions: any previous hospitalizations for catheter- or surgical-based interventions names of previous pediatric cardiologists and surgeons as well as the unit in which surgery, if any, was performed Dental hygiene \200 Smoking/drug and alcohol intake Current symptoms \200 Shortness of breath on exertion? \200 Ability to climb stairs, hills, walk on the \202 at, and dista nce covered? \200 Breathless on lying down? \200 Chest pain? Precipitating/relieving factors? \200 Any associated symptoms? Syncopal episodes? \200 Palpitations? Onset, duration \200 Associated pre-syncope/chest pain? \200 Ask patient to tap out rat e and rhythm of palpitations Assess ability index General inspection \200 Chart the patient \200\231s height, weight, and blood pressure (a lways in the arm opposite thoracotomy scar!) and oxygen saturations Does the patient have an obvious syndrome? Down \200\231s syndrome (1/3 associated with CHD, especially atrioventricular septal defect)? William \200\231s syndrome (supravalvar aortic and pulmonary stenosis)? \200 Noonan \200 \231s syndrome (dysplastic pulmonary valvular stenosis, hypertrophic cardiomyopathy)? Turner \200\231s syndrome (coarctation of the aorta/aortic valve stenosis)? Is the patient anemic or jaundiced? \200 Are there any features to suggest infective endo carditis? \200 Is there evidence of poor oral hygiene with dental caries or infected gums? Any tattoos or body piercing? ASSESSMENT OF PATIENTS WITH CHD (1) 593 Systematic approach to auscultation of a CHD patient 1. Listen to the heart sounds First heart sound \200 The \201 rst heart sound is usually heard as a single sound but since mitral closure is loudest, it is best heard at the apex A loud \201 rst heart sound may be heard in mitral stenosis or sometimes with an ASD Soft \201 rst heart sounds are a feature of poor myocardial contractility or a long PR interval Second heart sound \200 Fixed splitting in the presence of a signi \201 cant ASD, and is best appreciated in the high or mid left sternal border Accentuated in the presence of pulmonary hypertension \200 Widely split following repair of tetralogy of Fallot, the second heart sound is re \202 ecting the right bundle branch b lock (RBBB), characteristic of the post-operative electrocardiogram (ECG) 2. Check for systolic/diastolic murmurs. (Draw an imaginary line between the nipples) Murmurs that are loudest above the nipple line \200 Ejection systolic in type \200 Aris e from the right or left ventricular out \202 ow tract (LVOT) \200 If associated with a carotid or suprasternal thrill, usually from the left ventricular out \202 ow tract. If an ejection click is heard, the murmur is valvar in origin. \200 Ejection click of aor tic valve stenosis is best heard at the apex. \200 Ejection systolic murmur, best heard i n the interscapular region and associated with a left thoracotomy, may indicate turbulence across a prior coarctation repair Murmurs that are loudest below the nipple line \200 Pansystolic and arise from mitral/tri cuspid regurgitation or from a ventricular septal defect (VSD) A \200\230to and fro \200\231 murmur best heard at the upper left sternal edge following c ardiac surgery usually results from combined right ventricular out \202 ow tract (RVOT) ob struction and pulmonary regurgitation The mid-systolic click and systolic murmur of mitral valve prolapse is best heard with the patient standing up A continuous murmur arises from an arterial duct, systemic to pulmonary shunt, or arteriovenous \201 stulas Measure height, weight, blood pressure, and oxygen saturation in all patients. 12-lead ECG is essential at every visit. 594 CHAPTER 12 Congenital heart disease Assessment of patients with CHD (2) Electrocardiogram \200 Rate and rhythm : consider atr ial \202 utter with variable block if there is a constant rate of 100 or 150/minute \200\224 easily confused with \200\230sinus rhyth m \200\231. Atrial tachycardias are especially common after all forms of atrial surgery e.g . intra-atrial repair for transposition of the great arteries. Look for signs of chamber enlargement \200\224 atrial or ventricular hypertrophy. Assess the presence/absence of bundle branch block. \200 Measure the duration of QRS in a ll post-operative tetralogy of Fallot patients: QRS duration > 180 ms is associated with hi gher risk of arrhythmias, right heart dilatation, and late sudden death. If tachycardia is suspected, record 12-lead ECG during administration of IV adenosine. Role of exercise testing \200 Assess heart rate and blood pressure (BP) response to exerc ise (blunted response in important aortic valve stenosis). Compare upper and lower limb BP following coarctation repair. \200 Monitor oxygen saturat ion by pulse oximetry to improve risk strati \201 cation in cyanosed patients. Also, improves counseling and planning for pregnancy (most frequently used to assess potential impact of pregnancy). Formal cardiopulmonary exercise testing is reserved for decision making and retiming of sur gical or catheter-based intervention. \200 Can help to distinguish limitation due to lack of aerobic \201 tness, and assess maximal effort. Chest X-ray \200 Chest X-ray (CXR) is a cheap and invaluable investigation in CHD. \200 Identify right \200\223left orientation to assess cardiac and visceral positions. \200 A ssessment of the bronchial branching permits diagnosis of isomeric cardiac defects, e.g. symmetric morphologic right bronchi characteristic of right atrial is omerism (usually associated with complex CHD \200\224 common right atria, a common atriove ntricular (AV) ori \201 ce, a great artery arising from one ventricular chamber and total anomalous pulmonary venous connection). Identify situs inversus (mirror image anatomy with liver on the left and stomach bubble on the right with cardiac apex in right chest). Consider Kartagener syndrome. Discordance betw een the position of the apex and visceral situs is usually associated with CHD. Record the cardiothoracic ratio in the notes. Look for rib notching related to collateral b lood supply in severe coarctation of the aorta. Assess pulmonary vasculature (see box on ne xt page). ASSESSMENT OF PATIENTS WITH CHD (2) 595 CXR assessment of pulmonary vasculature in CHD patients Increased vascularity \200 Left t o right shunt (ASD, VSD) \200 Pulmonary oedema \200 Obstructed pulmonary venous drainag e Decreased vascularity \200 Right ventricular out \202 ow obstruction, e.g. isolated se vere pulmonary stenosis, following tetralogy repair Pulmonary hypertension Unilateral increased pulmonary vascular markings \200 Consider ips ilateral systemic to pulmonary arterial shunt \200 Overperfused major arterial pulmonary collateral artery \200 Obstructed pulmonary venous drainage, e.g. following Mustard/ Senn ing intra-atrial repair for transposition of the great arteries Imaging modalities in CHD Echocardiography \200 This is the most useful investigation in CHD but only when directed by detailed history taking and clinical examination. It should be performed by an experienced examiner with detailed knowledge of all aspects of CHD. There is no substitute for sequential data, and a protocol for regular, standardized analysis is required. Imaging in adults may be limited by poor echogenic windows. Magnetic resonance imaging (MRI ) \200 Ideal for the assessment of extra-cardiac pulmonary arterial and venous trees. Accurate quanti \201 cation of valvar regurgitation, e.g. assessment of pulmonary regurgit ation and right ventricular function following repair of tetralogy of Fallot. Its utility is limited by a scarcity of expert radiologists in the \201 eld of CHD. It is rapidly becoming established as providing the most detailed and useful information for dec ision making in complex CHD. Cardiac catheterization \200 This still has its place in quantifying shunts and obtaining accurate haemodynamic data. Increasingly, this is carried out to facilitate percutaneous transcatheter procedures such as occlusion of ASDs. With an aging population, many patients with CHD need to undergo coronary angiography, as c ombined surgical procedures may be required. 596 CHAPTER 12 Congenital heart disease Speci \201 c signs in patients with CHD Inspection Cyanosis or clubbing? Oxygen saturation should always be measured by pulse oximetry. Central cyanosis is an indication of arterial desaturation and is noted when more than 5 g/dL of reduced hemoglobin is circulating. Thus , it is dependent in part on the total hemoglobin concentration and may be missing in a pat ient with signi \201 cant desaturation but who is anemic. Differential cya- nosis implies \202 ow of deoxygenated blood from the pulmonary trunk into the aorta distal to the left subclavian artery, e.g. non-restrictive patent arterial duct with pulmonary vascular diseas e and right-to-left shunt. Previous operation scars? Lift the patient \200\231s arms and look for evidence of thoracot omy scars. Is the apex beat displaced or even in the right chest? Assess co-morbidity, e.g. scoliosis and respiratory dysfunction related to prior lateral thoracotomy. Jugular venous pulse (JVP) This can give information about conduction effects and arrhythmi as, wave- form, and pressure. Increased resistance to atrial \201 lling results in an exa g- gerated \200\230a \200\231 wave, which may occur in isolated severe pulmonary stenosis or in tricuspid atresia. Episodic \200\230cannon \200\231 waves occur in cases of heart bl ock when the atrium contracts against a closed tricuspid valve. A prominent \200\230v \200 \231 wave is characteristic of tricuspid regurgitation. Palpation \200 Feel all the pulses, including the femorals. Coarctation of the aorta is a clinical diagnosis. Check the blood pressure in the upper and lower limbs, palpating the posterior tibial artery with the cuff in \202 ated around the calf. Bounding pulses are characteristic of severe aortic regurgitation, patent arterial duct, or the presence of a surgical systemic to pulmonary arterial shunt (Blalock \200\223Taussig). An increase in the right brachial pulse may re \202 ect the Coanda effect of supravalvar s tenosis in patients with Williams \200\231 syndrome. Thrills may be felt in the femoral ves sels, re \202 ecting AV malformation following prior cardiac catheterization. Check the position of the apex beat. Also, check that the liver and stomach are in the correct position. Situs inversus with the apex in the right chest is the mirror image of normal; 95 % of patients with mirror image dextrocardia have no co-existin g congenital cardiac disease. Situs solitus with the apex in the right chest is invariably associated with CHD, and is often complex and unpredictable. A parasternal heave represents right ventricular overactivity, most marked when there is bo th pressure and volume overload of the chamber, such as following repair of tetralogy of Fa llot. A palpable second sound in the upper left intercostals space is detected when pulmonary hypertension is present. This page intentionally left blank 598 CHAPTER 12 Congenital heart disease Surgical operations for CHD (1) Congenital heart surgery in adolescents and adults should o nly be under- taken in specialist centers. There are three categories: \200 patients who have not undergone prior operations \200 patients who have undergone previous palliative operations \200 patients who have undergone previous reparative procedures. Re-do sternot omy, preservation of myocardial performance, and atten- tion to pulmonary bed vascular abno rmalities and aorto-pulmonary col- laterals require careful prior planning and close co-ope ration between the surgeon, cardiac anesthetist, cardiologist, and intensive care team. Blalock \200\223Taussig shunt This is a procedure for systemic to pulmonary arterial shunt, using a sub- clavian arterial \202 ap (classical) or Gore-Tex tube (modi \201 ed) to increase pulmonary blood \202 ow and improve oxygenation in cyanotic congenital heart di sease. This is a palliative procedure which has superseded earlier operations such as Water ston shunt (ascending aorta to right pulmonary artery) or Pott \200\231s shunt (descending aorta to left pulmonary artery). Coarctation of the aorta This is relieved by either a subclavian \202 ap approach or dire ct end-to-end anastomosis. Occasionally, a bypass graft is required in adult patients, from the ascending to descending aorta. Glenn shunt The superior vena cava (SVC) is anastomosed to the ipsilateral pulmonary artery as a means of improving oxygenation in infants or young children. This is usually con \201 ned to patients with \200\230single \200\231 ventricles and univen- tricular circulat ions. In its classical form, the right pulmonary artery was detached from the main pulmonar y artery. The bidirectional Glenn shunt was fashioned such that blood from the SVC entered both pulmonary arteries. This page intentionally left blank 600 CHAPTER 12 Congenital heart disease Surgical operations for CHD (2) Tetralogy of Fallot (see Fig. 12.1) This is treated by clos ure of the ventricular septal defect with a patch of pericardium or Gore-Tex and relief of the RVOT obstruction by trans- annular patching, valvectomy, or placing a homograft/cond uit between the right ventricle and pulmonary artery. Rastelli operation (see Fig. 12.2) This is usually undertaken in patients with complex CHD, e.g. transposi- tion of the great arteries with large VSD. The VSD is closed by a large pa tch in such a way as to connect the left ventricle to the aorta, and a conduit or homograft connects the right ventricle to the pulmonary artery (PA). Ross operation This is an alternative to aortic valve replacement, which may be attrac- tiv e to younger patients, especially females. The diseased aortic valve is removed with the co ronary arteries detached. The patient \200\231s own pulmo- nary valve is resected and place d in the aortic position with the coronaries reattached. A homograft is placed between the right ventricle and the pulmonary artery. Fontan operation This represents the de \201 nitive palliation for patients with effective ly uni- ventricular circulations such as mitral or tricuspid atresia. Blood from the superi or and inferior vena cava is directed to the pulmonary arteries without the bene \201 t of a subpulmonary ventricle. Oxygenated blood returns to the systemic ventricle and is then p umped to the aorta. Mustard/Senning operations (see Fig. 12.3) These are life-saving innovations for treatment of patients with transposi- tion of the great arteries, which involve intra-atrial redirect ion of oxygen- ated and de-oxygenated blood to the systemic and pulmonary systems respectiv ely. The right ventricle serves as the systemic subaortic ventricle. The procedures have be en largely abandoned because of late problems with arrhythmias, pathway obstruction, and ve ntricular failure. Arterial switch This has largely superseded the Mustard/Senning procedure. The aorta and pu lmonary artery are relocated to their original positions, with re-anastomosis of the corona ry arteries to the neo-aorta. SURGICAL OPERATIONS FOR CHD (2) 601 RA Ao LA RA LV RV Fig. 12.1 Tetralogy of Fallot. Ao = aorta; LA = left atrium; LV = left ventricle; RA = righ t atrium; RV = right ventricle. Rastelli repair Ao Ao PA PA LA LA Pulmonary stenosis VSD RA RA LV RV LV RV Patch across RV prevents blood passing from RV to aorta Conduit connects RV to PA Fig. 12.2 The Rastelli operation. PA = pulmonary artery. 602 CHAPTER 12 Congenital heart disease 1 Aorta Art. pulm. V cava V. pulm. 2 Aorta Art. pulm. V. cava V. pulm. 3 Aorta Art. pulm. LA V. cava V. pulm. Fig. 12.3 The Senning operation. Redrawn from Koustantinov, IE et al. (2004). Atrial switch operation: past, present, and future. Annals of Thoracic Surgery , 77 : 2250 \200\2238, wi th permission. This page intentionally left blank 604 CHAPTER 12 Congenital heart disease Percutaneous transcatheter interventions for CHD Balloon atrial septostomy This is a life-s aving intervention in neonates with transposition of the great arteries in which an atrial communication is created by tearing a hole in the atrial septum using a balloon catheter. I t can be performed at the bedside under echocardiographic control. Pulmonary valvuloplasty This is the procedure of choice for patients of all ages with pulmo nary valvar stenosis. It is less successful if the valve is dysplastic (Noonan \200\231s sy n- drome). The pulmonary valve annulus is measured by echocardiography or angiography, and a balloon (100 \200\223120 % diameter) is used. It is one of the most effective transcathet er interventions. Aortic valvuloplasty This is of limited use in adults. If the aortic valve is pliable but n ot calci \201 ed, balloon dilatation may defer the need for de \201 nitive surgery but us ually at the expense of aortic regurgitation. The balloon size should not exceed the size o f the aorta at the site of the valve attachment. An antegrade approach via a trans-septal p uncture is advised, to reduce the incidence of valve damage. Atrial septal defect Most secundum atrial septal defects are amenable to percutaneous closu re. The Amplatzer septal occluding device is made of nitinol (a nicke titanium alloy wit h inherent shape memory) and comprises two disks with a self-centering waist. The defect ma y be balloon sized under transoesopha- geal echocardiographic (TOE) guidance. Defects up to 40 mm in size can be closed providing there are suf \201 cient rims ( > 5 mm) to the pulm onary veins and the attachment of the mitral valve. As a rule of thumb, patients with pulmo nary arterial pressures <70 mmHg can proceed to ASD closure. This is not suitable for any a trial defects other than those of the secundum variety, i.e. sinus venosus defects or parti al atrioventricular septal defects. Procedural complications are rare in expert hands. Anti platelet agents are administered for three to six months until the device has completely en dothelialized. Transient headaches are common in the weeks fol- lowing closure but serious complications are rare. These include transient ischaemic episodes/stroke, atrial arrhythmi as, and embolization of the device. Remember that concomitant electrophysiological procedur es may need to be undertaken in patients with signi \201 cant atrial arrhythmias. Ventricular septal defects Indications for closing defects in adults are limited, and the p rocedure is most frequently employed in patients with ischaemic VSD. Occasionally, \200 \230small \200\231 defects can produce volume overload of the left ventricle over time and require closure. Such defects may be amenable to transcatheter occlu- sion using the Amplat zer peri-membranous or muscular occluding devices. PERCUTANEOUS TRANSCATHETER INTERVENTIONS FOR CHD 605