Tetralogy of Fallot & Pacing Saeed Oraii MD, Cardiologist - - PowerPoint PPT Presentation

Tetralogy of Fallot

& Pacing

Saeed Oraii MD, Cardiologist Interventional Electrophysiologist Tehran Arrhythmia Clinic April 2016

Tetralogy of Fallot

• Tetralogy of Fallot (TOF) is the most common

form of cyanotic congenital heart disease.

• The first cardiac repair
• f TOF was successfully

performed in 1955 in the United States.

Hoffman, J.I. and Kaplan, S. The incidence of congenital heart disease. J Am Coll Cardiol. 2002; 39: 1890–1900. Lillehei, CW CM, et al. Direct vision intracardiac surgical correction of the tetralogy of Fallot, pentalogy of Fallot, and pulmonary atresia defects: report of first ten cases. Ann Surg. 1955; 142:418–420.

Improving Survival

• Patients with congenital heart disease (CHD)

are living longer.

• Surgical repair of TOF is highly successful.
• In the United States, a 40% reduction in

annualized death rates for TOF was reported between 1979 and 2005.

Pillutla P, et al. Mortality associated with adult congenital heart disease: Trends in the US population from 1979 to 2005. Am Heart J 2009;158: 874–879.

Growing Population

• The population of adults with repaired TOF

and other CHD is growing rapidly.

Brickner, et al. Congenital heart disease in adults (First of two parts). N Engl J Med. 2000; 342: 256–263.

Arrhythmias, Leading Cause of Death

Conduction Abnormalities

• Right bundle branch block (RBBB) is almost

universal in patients after TOF repair

• Approximately 15% of

these patients, have also left anterior hemiblock.

• Many patients have slower atrioventricular

(AV) conduction as well.

Therrien J, Marx GR, Gatzoulis MA. Late problems in tetralogy of Fallot: recognition, management, and prevention. Cardiol Clin 2002;20:395– 404.

Conduction System Injury

• Tremendous advances in the surgical

management of CHD have been achieved over the past half century.

• Nevertheless, conduction system injury

continues to be a leading cause of long-term postoperative cardiac morbidity.

Incidence

• The incidence of postoperative AV conduction

block has declined significantly since it was first explored in detail in a landmark paper by Lillehei et al in 1963.

• Still, heart block continues to complicate

approximately 1% to 3% of operations performed at major CHD surgical centers.

Bonatti, et al. Early and late postoperative complete heart block in pediatric patients submitted to open-heart surgery for congenital heart disease. Pediatr Med Chir. 1998; 20: 181–186

Spontaneous Resolution

• Postoperative heart block is variably reported

to resolve spontaneously in 43% to 92% of cases.

• The large degree of variation among studies is

attributable to a variety of factors, such as the era, case identification and inclusion criteria, and follow-up duration.

Gross G, et al. Natural history of postoperative heart block in congenital heart disease: Implications for pacing intervention. Rhythm May 2006 Volume 3, Issue 5, Pages 601–604

Spontaneous Recovery

• Spontaneous recovery usually does take place

within 7 to 10 days.

Gross G, et al. Natural history of postoperative heart block in congenital heart disease: Implications for pacing intervention. Rhythm May 2006 Volume 3, Issue 5, Pages 601–604

Timing of Pacemaker Implant

• There is uncertainty regarding optimal timing of

permanent pacemaker (PPM) implantation

– Long-term risks associated with nonintervention, vs. the morbidity of lifelong pacemaker therapy

• The concept that transient, spontaneously

resolving heart block does not require permanent pacing is widely accepted, but its application is less clear considering the possibility of late recovery of heart block vs. late recurrence.

Late Recovery

• Late recovery is well recognized.
• Recovery of AV conduction was reported in

about 10% of cases of postoperative heart block persisting beyond 14 days.

• Recovery was noted at postoperative times

ranging up to 113 days (median 41 days).

Batra A.S., et al. Late recovery of atrioventricular conduction after pacemaker implantation for complete heart block associated with surgery for congenital heart disease. J Thorac Cardiovasc Surg. 2003;125: 1291–1293

Very Late Recovery

• Even very late recovery of AV conduction has

been reported up to 20 years (median 5.5 years) after onset of heart block in 14 (32%) of 44 patients who had undergone PPM implantation.

Bruckheimer E., et al. Late recovery of surgically-induced atrioventricular block in patients with congenital heart disease. J Interv Card Electrophysiol. 2002; 6:191–195

Against Delay in Implant

• Despite the possibility of a late return of AV

conduction, two contemporary considerations weigh against protracted delay in the decision to proceed with PPM implantation.

– The ongoing improvement in longevity and miniaturization of pacing systems available for infants and children, reducing concerns over pacing-related morbidity – The cost-driven pressure for reductions in hospital length-of-stay

Recurrence of AV Block

• Although the decision to proceed with PPM

implant is largely made by the immediate time course of recovery from postop AV block, the risk of late recurrence of heart block is a more

• minous and poorly defined problem with

potentially life-threatening implications.

• The very concept of “recurrence” is challenged

by the observation that heart block can appear, presumably de novo, long after CHD surgery.

Early vs. Late Onset

• In a report, 114 CHD patients undergoing PPM

implantation for postoperative AV block were divided into “early”- and “late”-onset groups

– Those whose heart block was initially detected either less than 30 days or at least 30 days after surgery.

• Fully 36% of the patients fell into the “late”

group, with heart block identified at a mean of 4.7 years after CHD surgery in that group.

Goldman B.S., et al. Permanent cardiac pacing after open heart surgery(congenital heart disease) . Pacing Clin

• Electrophysiol. 1985; 8: 732–739

Association with Sudden Death

• The incidence of late sudden death is correlated

strongly with transient postop heart block.

• Among 20 patients with postop heart block

lasting more than 3 days, 8 (40%) subsequently died suddenly.

• The sudden death rate among 55 patients with

heart block of shorter duration was 7.3%, similar to the 6.1% noted in the 196 patients who had no documented heart block.

Hokanson J.S. et al. Significance of early transient complete heart block as a predictor of sudden death late after operative correction of tetralogy of Fallot. Am J Cardiol. 2001; 87: 1271–1277

Site of Block

• Several investigators have attempted to identify

additional prognostic predictors in the early postop heart block.

• Attention has focused on the anatomic site of

conduction system disruption (above or below His bundle).

• The location and degree of conduction system

injury likely do carry prognostic significance in patients with transient heart block.

Krongrad E. Prognosis for patients with congenital heart disease and postoperative intraventricular conduction

• defects. Circulation. 1978; 57: 867–870

Residual Fascicular Block

• The risk increases dramatically when transient

heart block recovered with residual bifascicular block.

• Late-onset complete heart block occurs in

almost 33% of such patients.

• At another report, 16 (29%) of these patients

experienced either late-onset complete heart block or sudden cardiac death.

Krongrad E. et al. Prognosis for patients with congenital heart disease and post-operative intraventricular conduction

• defects. Circulation 1978;57:867–870. 354.

Wolff GS, et al. Surgically induced right bundle-branch block with left anterior hemiblock. An ominous sign in postoperative tetralogy of Fallot. Circulation 1972;46:587–594.

Transient AV Block

• A pacemaker should, therefore, be considered

in patients with postoperative transient AV block and residual bifascicular block (IIb indication).

• However, there is currently no evidence to

support routine pacemaker implantation for bifascicular block in asymptomatic adults with CHD who did not have transient complete AV block.

Congenital Heart Disease: Adult Arrhythmias. HRS Consensus 2014

Atrial Arrhythmias

• Despite congenital or postop AV block, atrial

fibrillation and intra-atrial reentrant tachycardia remain an ongoing concern in patients with CHD and can complicate effective utilization

• f dual-chamber pacing.
• Dual-chamber pacing is preferred over VVI

pacing in adults with CHD and intrinsic or postop heart block.

Connelly MS, et al. Congenitally corrected transposition of the greatarteries in the adult: functional status and

• complications. J Am Coll Cardiol 1996;27:1238–1243.

Optimal Lead Implant Site

• It is now well recognized that right ventricular

pacing, especially the free wall, can have deleterious effects on ventricular function.

• Although ventricular septal

pacing has been advocated as preferential to the apex, surgical patch materials can prevent septal implant.

Janousek J, et al. Permanent cardiac pacing in children: choosing the optimal pacing site: a multicenter study. Circulation 2013;127:613–623.

AV Valve Flow Pattern

• Standard RV pacing without careful manipulation
• f the AV interval may be insufficient to shorten

the QRS duration in patients with TOF and RBBB.

• Concomitant echocardiographic evaluation of AV

valve inflow patterns with pacemaker programming of AV intervals may allow for identification of the longest possible diastolic filling time for maximal cardiac output.

Stephenson EA, et al. Relation of right ventricular pacing in tetralogy of Fallot to electrical resynchronization. Am J CardioI 2004;93:1449-1452, A1412.

Late Postoperative Problems

• Despite high surgical success rates, long-term

mechanical problems after surgical repair include pulmonary regurgitation, right ventricular (RV) dilation due to residual RV

• utflow tract obstruction and/or pulmonary

regurgitation, tricuspid valve regurgitation, residual ventricular septal defect, and left ventricular (LV) dysfunction.

Murphy, J.G., et al. Long-term outcome in patients undergoing surgical repair of tetralogy of Fallot. N Engl J

• Med. 1993; 329: 593–599.

Delhaas T, Prinzen F W. Right ventricular or biventricular pacing in repaired tetralogy of Fallot? Heart Rhythm, Vol 7, No 3, March 2010. 351-2.

Redo Surgeries

• Although the timing of primary repair has also

changed toward repair at presentation or symptom appearance, most adult patients with repaired TOF currently have undergone trans- annular patching.

RV Dysfunction

• Right heart failure is due to the combined

effects of pressure and volume overloads and

• f the myocardial lesions inflicted during and

after the operation.

• The resulting RV dysfunction may lead to

fibrosis, which, in itself, begets RV dysfunction and is accompanied by delay in electrical activation of myocardial tissue.

RV Dysfunction

• RV dysfunction and right heart failure in patients

with TOF often are multifactorial in origin:

– Chronic pressure overload, – Volume overload, – Myocardial injury associated with cardiopulmonary bypass during surgical repair, – RBBB and electrical dyssynchrony, or – A combination of these factors.

Dubin A., Rosenthal D. Right ventricular resynchronization: Moving beyond proof of concept. Rhythm June 2009Volume 6, Issue 6, Pages 857–859.

RBBB

• RBBB almost invariably develops after surgical

repair of TOF.

• Besides the direct interruption of conduction

pathways and various hemorrhagic, edematous,

• r ischemic complications, the duration of
• peration, the performance of a ventriculotomy,

and the repair of an interventricular septal defect

• r of the muscular outflow tract are all

contributing factors.

Hazan, E., et al. Is right bundle branch block avoidable in surgical correction of tetralogy of Fallot? Circulation. 1980; 62: 852–854.

RBBB & Hemodynamics

• The hemodynamic consequences of RBBB

might play a predominant role in the long-term clinical outcomes of these patients.

• A relationship probably exists between

electrical and mechanical dysfunction, as well as links between myocardial remodeling, rhythm disturbances, and electromechanical dyssynchrony.

Gatzoulis, M.A., et al. Risk factors for arrhythmia and sudden cardiac death late after repair of tetralogy of Fallot: a multicentre study. Lancet. 2000;356: 975–981.

RBBB & Prognosis

• Depressed contractility and remodeling may be

promoted by mechanical dyssynchrony, which, therefore, may be a desirable therapeutic target.

• Furthermore, a wide QRS is prognostically

important, and QRS duration and risk of developing ventricular arrhythmias are closely correlated.

Scherptong, R.W., et al. Follow-up after pulmonary valve replacement in adults with tetralogy of Fallot: association between QRS duration and outcome. J Am Coll Cardiol. 2010; 56: 1486–1492.

The Level of Block

• Postoperative RBBB is classified as proximal

when near the His bundle, distal when at the level of the moderator band, and terminal when due to injury to the Purkinje network.

• No electrocardiographic criterion is capable of

precisely locating the level of block.

Thambo J, Haissaguerre M, et al. Electrical dyssynchrony and resynchronization in tetralogy of Fallot. Heart Rhythm June 2011Volume 8, Issue 6, Pages 909–914.

Level of Block

• It could be important to know the level of

block for several reasons.

• The risk of complete AV block is considerably

higher when the block is proximal than when it is distal, since conduction depends only on the left bundle branch.

Thambo J, Haissaguerre M, et al. Electrical dyssynchrony and resynchronization in tetralogy of Fallot. Heart Rhythm June 2011Volume 8, Issue 6, Pages 909–914.

Level of Block & CRT

• From the perspective of Cardiac

Resynchronization Therapy (CRT), which tries to correct the dispersion of segmental electromechanical activation, it might be critical to pinpoint the site of block.

• The characteristic activation sequence of

proximal RBBB, which is most likely to complicate the repair of an interventricular septal defect, is markedly different from terminal block.

Proximal vs. Terminal Block

• In Proximal block the entire ventricular mass

is activated via the left bundle, and the RV is activated by continuity, with important delays among the septal, apical, outflow, and free wall segments.

• In contrast, in the presence of terminal block,

usually caused by ventriculotomy or myocardial resection, the activation delay is confined to the anterior outflow tract.

Distal RBBB

• Distal block, intermediate between proximal

and terminal and usually caused by the direct section of the moderator band, is characterized by:

– Preserved activation of the anteroseptal and apical RV via right bundle fibers, which penetrate the RV myocardial tissue ahead of the moderator band – Delayed activation of the RV posterior wall.

Mapping the Level of Block

• In contrast to the weak contributions of the

surface electrocardiogram, invasive or noninvasive mapping may facilitate the localization of the level of block.

• A normal activation of the RV apex excludes

the presence of proximal block.

Ventricular Activation Pattern

• Marked differences observed in the ventricular

electrical mapping of two patients whose surface electrocardiogram showed the same RBBB pattern after surgical repair of TOF.

Thambo, J, et al. Electrical dyssynchrony and resynchronization in tetralogy of Fallot. Heart Rhythm Volume 8, 909-914.

Proximal block Distal block

Level of Block & Dyssynchrony

• Remodeling leading to RV dilatation and

dysfunction varies as a function of the level of block.

• A relationship between electrical

dyssynchrony and mechanical dysfunction is distinctly more likely in the presence of proximal than terminal block, since the hemodynamic consequences of delayed

• utflow tract (OT) activation are small.

A Wide QRS

• RV dysfunction and dilatation of chambers

promote the development of myocardial fibrosis, which is electrophysiologically manifested by fragmented and low-amplitude endocardial electrograms.

• The presence of a >180-ms QRS duration is

not simply due to the section of a conduction pathway and is invariably the expression of a widespread disorder of intramyocardial conduction.

Wide QRS & Dyssynchrony

• In all echocardiographic studies conducted in

this patient population, electrical dyssynchrony has invariably been associated with mechanical dyssynchrony.

• Differences were observed, however, in the

sites of ventricular activation delays and types

• f dyssynchrony.

Uebing A., et al. Right ventricular mechanics and QRS duration in patients with repaired tetralogy of Fallot: implications of infundibular disease. Circulation. 2007; 116: 1532–1539.

Practical Implications

• In the case of major activation delays in the

RV chamber, the implantation of an RV lead may be appropriate.

• In contrast, in the case of disturbances

confined to the OT, the hemodynamic effects

• f implanting a lead in the RV chamber or in

the OT are uncertain, because of the marked electrical and mechanical abnormalities encountered in that region.

TOF & LV Dyssynchrony

• A 50%–90% prevalence of LV dyssynchrony

has been observed in echocardiographic studies of TOF.

• The mechanical interaction between a dilated

and pressure-overloaded RV and an a priori functionally and structurally normal LV stresses the septal surface and causes LV activation delays.

Abd El Rahman M.Y., et al. Detection of left ventricular asynchrony in patients with right bundle branch block after repair of tetralogy of Fallot using tissue-Doppler imaging-derived strain. J Am Coll Cardiol. 2005; 45: 915–921. Uebing A., et al. Right ventricular mechanics and QRS duration in patients with repaired tetralogy of Fallot: implications of infundibular disease. Circulation. 2007; 116: 1532–1539.

• Furthermore, perioperative ischemia and

variable operative techniques may contribute to LV dyssynchrony.

• The presence of contractile dysfunction

associated with a left-sided conduction disturbance is a major determinant of the mode

• f stimulation recommended for these patients.

TOF & LV Dyssynchrony

A Vicious Circle

• Pulmonic insufficiency causes a progressive

increase in RV volumes, which, in turn, increases the activation time and causes segmental dyssynchrony of activation.

• The conduction disorder may then promote

remodeling and further chamber dilatation.

• Deleterious effect and adverse outcome persist

even after pulmonary valve replacement.

Scherptong R.W., et al. Follow-up after pulmonary valve replacement in adults with tetralogy of Fallot: association between QRS duration and outcome. J Am Coll Cardiol. 2010; 56: 1486–1492

Current Therapies

• Current therapies for chronic RV failure are

largely empiric, and their effectiveness is not known.

• All treatment approaches for RV failure

considered together have been studied in fewer than 500 subjects.

• This contrasts markedly with left ventricular

failure, for which multiple therapeutic strategies have been evaluated, often in mega-trials of thousands of subjects.

CRT & LV Failure

• Cardiac Resynchronization Therapy has been

shown to be effective in addressing the fundamental problems of left heart failure, improving quality of life and exercise capacity and prolonging survival in patients with electrical dyssynchrony and cardiomyopathy.

CRT in Children

• Unlike LV failure, RV failure is poorly

understood and its management remains largely empirical.

• In contrast to the vast

experience with CRT in adults with LV dysfunction and LBBB, studies of the CRT in patients with CHD and RV dysfunction are limited to case reports and retrospective analyses of heterogeneous populations.

Application to RV Failure

• Some application of CRT to the problem of

RV failure has already been made, but we are

• nly in the very early stages of this process.
• Among the important obstacles to be addressed

are the inadequacies of current assessments of RV function, the heterogeneity of diseases that lead to RV failure, and the difficulty of identifying appropriate clinical endpoints for assessing efficacy of treatment.

CRT in Children

• The heterogeneous patient population, technical

limitations from patient size, vascular access issues, and unique forms of ventricular dyssynchrony make it difficult to determine risks and benefits of this procedure in children.

Greene EA, Berul CI. Pacing treatment for dilated cardiomyopathy: optimization of resynchronization pacing in

• pediatrics. Curr Opin Cardiol 2010;25:95-101.

Khairy P, et al. Cardiac resynchronization therapy in congenital heart disease. Int J ardioI 2006;4:711-720.

Assessment of RV Function

• Echocardiography is much less accurate for global

RV function than it is for LV function.

• Echocardiography can also offer a limited

information about timing of RV regional contraction, a problem that results from the complex anatomy of the RV.

• Assessment of global RV function now can be

reliably performed using cardiac magnetic resonance imaging (MRI).

Indolent Nature

• Finally, the clinical picture of right heart

failure poses unique challenges to implementation of CRT.

• RV failure is an indolent disease, characterized

by long-term consequences of cirrhosis, cachexia, and effort intolerance but not associated with high rates of short-term mortality.

Disease Course

• Unlike LV failure, chronic RV failure does not

have high rates of mortality over a period that a clinical trial could reasonably study.

• Therefore, the clinical endpoints for a trial of

RV CRT are difficult to define.

RBBB & CRT

• More than 70% of CRT in the pediatric age

group has been in the setting of CHD, 30% to 40% involving the RV.

• In the setting of RBBB, Vogel et al

first demonstrated abnormal regional wall motion in the RV free wall and interventricular septum using tissue Doppler techniques,

• ffering an early suggestion of a substrate for

resynchronization.

Dubin A, et al. Resynchronization therapy in pediatric and congenital heart disease patients: an international multicenter

• study. J Am Coll Cardiol. 2005; 46: 2277–2283.

Vogel M., et al. Regional wall motion and abnormalities of electrical depolarization and repolarization in patients after surgical repair of tetralogy of Fallot. Circulation. 2001; 103: 1669–1673

Postoperative Trials

• The immediate postoperative effects of cardiac

resynchronization were initially studied in mixed populations of patients presenting with congenital heart disease, as well as in patients with TOF.

• Atrial synchronized RV stimulation with
• ptimized AV delays was performed using

temporary RV wires placed during the

• peration.

Short term Effects

• Although their endpoints were variable, all

studies reported hemodynamic improvements and alleviation of postoperative heart failure.

• Ventricular stimulation immediately increased

the systemic blood pressure, enabled a decrease in inotropic support and volume replacement, and stabilized hemodynamic function during the first postop 48 hours, after which stimulation could be uneventfully discontinued.

Roofthooft M.T., et al. Resynchronization therapy after congenital heart surgery to improve left ventricular function. Pacing Clin Electrophysiol.2003; 26: 2042–2044.

Long term Stimulation

• Studies of the clinical outcomes of patients

with TOF who underwent long-term cardiac stimulation for hemodynamic indications are few.

• A few case reports, or isolated patients

presenting with TOF, who were included in single- or multicenter studies of CRT in patients with CHD.

RV only Pacing

• In one study, RV pacing improved RV

function without affecting LV function.

• These findings paved

the way to the idea of RV resynchronization by RV pacing in patients with TOF.

Thambo J-B, et al. Biventricular stimulation improves right and left ventricular functions after tetralogy of Fallot repair: acute animal and clinical studies. Heart Rhythm 2010;7:344 –350.

Single RV Pacing

• Singe-sided RV pacing is generally regarded

as detrimental in the long term in patients with anti-bradycardia pacing and normal ventricular conduction.

• It may, however, be beneficial in patients with

TOF, heart failure and wide QRS complex due to RBBB.

• This beneficial effect could be attributed

entirely to resynchronization of the RV by RV pacing.

Single Sided RV Pacing

• Single sided RV pacing, as it resynchronizes

the RV with RBBB, may be considered analogous to LV pacing in LBBB.

• Ventricular pacing also can be helpful in

correcting prolonged AV conduction, thereby

• ptimizing filling.

Auricchio A, et al. Effect of pacing chamber and atrioventricular delay on acute systolic function of paced patients with congestive heart failure. The Pacing Therapies for Congestive Heart Failure Study Group. The Guidant Congestive Heart Failure Research Group. Circulation 1999;99:2993–3001.

Long Term Studies

• A prospective study evaluated RV

resynchronization therapy in outpatients with TOF and right heart failure who already had an ICD in place.

– A single-blinded crossover design – Improvement in RV ejection fraction – Improvement in self-reported quality of life. – No decrease in left ventricular ejection fraction

Dubin A.M., et al. A prospective pilot study of right ventricular resynchronization. Heart Rhythm. 2008; 5: S42

Long Term Studies

• In another study in adults with TOF they failed

to demonstrate improved cardiac index using RV CRT.

• At this time, RV CRT can be considered as

unproven, but its use should be considered in patients who have failed other options.

Bordachar P., et al. Presence of ventricular dyssynchrony and haemodynamic impact of right ventricular pacing in adults with repaired tetralogy of Fallot and right bundle branch block. Europace. 2008; 10: 967–971

Biventricular Pacing

• One study in seven children with congenital

heart disease and a RBBB pattern found that resynchronization therapy by biventricular (BiV) pacing resulted in small, but statistically significant, acute improvements in cardiac

• utput and right ventricular dp/dt.

Dubin AM, et al. Electrical resynchronization: a novel therapy for the failing right ventricle. Circulation 2003;107:2287- 2289.

Biventricular Pacing

• A single-center experience with CRT in 60

consecutive children demonstrated benefit in the majority of patients, although there were significant challenges associated with implantation.

Cecchin F, et al. Cardiac resynchronization therapy (and multisite pacing) in pediatrics and congenital heart disease: five years experience in a single institution. J Cardiovasc Electrophysiol 2009;20:58-65.

Biventricular Pacing

• Bleasdale et al showed that in patients with

heart failure and elevated central venous pressure, LV preexcitation can improve LV function, even in the absence of resynchronization, by reducing external constraint of the LV.

Bleasdale RA, et al. Left ventricular pacing minimizes diastolic ventricular interaction, allowing improved preload- dependent systolic performance. Circulation 2004;110:2395–2400.

Heart Failure without RBBB

• The fact that not all failing RV can be improved

by RV pacing is actually demonstrated by the animal data, which showed that in failing RV in the absence of a proper RBBB, RV pacing was harmful to RV function.

• Resynchronization therapy should always be

focused on restoring or optimizing ventricular synchronous electrical activation with single- sided LV pacing, single-sided RV pacing, or BiV pacing.

CRT & Narrow QRS

• Failure of studies such as RethinQ (Cardiac-

Resynchronization Therapy in Heart Failure with Narrow QRS Complexes) indicate that CRT is useless in patients with narrow QRS complexes.

• After all, in hearts with normal impulse

conduction, even BiV pacing creates, rather than reduces, asynchrony and thus can worsen patients' condition.

Auricchio, A., et al. Effect of pacing chamber and atrioventricular delay on acute systolic function of paced patients with congestive heart failure(The Pacing Therapies for Congestive Heart Failure Study Group. The Guidant Congestive Heart Failure Research Group) . Circulation. 1999; 99: 2993–3001

RV vs. BiV Pacing

• Although long-term single-chamber RV pacing

for bradycardia in the presence of normal ventricular function is considered detrimental, it may be beneficial in patients presenting with heart failure and RBBB.

• On the other hand, BiV stimulation seems

preferable in the presence of concomitant LV dysfunction.

Thambo J.B., et al. Biventricular stimulation improves right and left ventricular function after tetralogy of Fallot repair: acute animal and clinical studies. Heart Rhythm. 2010; 7: 344–350.

For Whom, When, and How?

• The presence of a wide QRS in patients with

ventricular dysfunction indicates an increased risk of heart block and sudden death that may suggest, at a minimum, the implantation of a dual-chamber ICD.

• Once a decision has been made for ICD, one

must decide whether to add CRT to improve a hemodynamic status that is often the main presenting problem.

For Whom?

• The surface ECG might not be the most reliable

means of identifying candidates for CRT.

• Various echocardiographic studies and invasive
• r noninvasive mapping techniques, which

more accurately detect inter-individual variations, are more likely to identify the best candidates for CRT.

• This, however, has not been reproduced in

clinical trials by now.

When?

• Equally uncertain is the optimal timing of CRT

system implantation in these patients.

• From the studies published so far, it is unclear

when CRT should be prescribed?

– In combination with an ICD upon the development of arrhythmias or ventricular dysfunction or – Earlier, with a view to prevent the adverse effects of remodeling due to prolonged electrical dyssynchrony, which creates the substrate for ventricular tachyarrhythmias.

How?

• Ventricular dysfunction in TOF is initially

limited to the right heart.

• The observations made thus far in this patient

population suggest that the implant of a standard dual-chamber pacemaker is promising.

• However, RV stimulation might adversely

impact LV activation. Thus, an ideal solution would favor a fusion with the spontaneous wavefront to preserve normal LV activation.

BiV vs. RV Stimulation

• BiV stimulation is unequivocally more challenging

technically, although it seems most appropriate in the presence of concomitant LV dysfunction.

Thambo J, et al. Electrical dyssynchrony and resynchronization in tetralogy of Fallot. Heart Rhythm Volume 8, Issue 6, Pages 909-914

Design of Trials

• The evaluation of hemodynamic effects

conferred by CRT warrant the organization of a multicenter study of the effects of long-term stimulation in patients with TOF.

• The contributions made by CRT must be

examined separately for each congenital disease, as the only link between patients with TOF, systemic RV, idiopathic dilated cardiomyopathy,

• r single ventricle is the physician who takes

care of them.

MRI-compatible Pacing Leads

• Looking to the future, the problems previously

preventing accurate evaluation of RV function will largely resolve to the emergence of MRI- compatible pacing leads, which allow accurate quantitative measurement of RV function in patients with implanted devices.

Tehran Arrhythmia Clinic

TOF & Tachyarrhythmias

• Tachyarrhythmias are common in adults with

repaired TOF.

• In a multicenter cohort followed up for 35

years after corrective surgery, sustained atrial and ventricular tachyarrhythmias occurred in 10% and 12% of patients, respectively.

Gatzoulis MA, et al. Risk factors for arrhythmia and sudden cardiac death late after repair of tetralogy of Fallot: a multicentre

• study. Lancet 2000;356:975–981.

Mechanism of Arrhythmias

• Macro-reentrant right atrial tachycardia is the

most common atrial arrhythmia.

• However, in a multicenter cohort of adults

with TOF, atrial fibrillation was the most prevalent one over the age of 55 years.

• The mechanism for monomorphic ventricular

tachycardia in the young adult with surgically repaired TOF is most often macro-reentry.

Khairy P, et al. Arrhythmia burden in adults with surgically repaired tetralogy of Fallot: a multi-institutional study. Circulation 2010;122:868–875.

Arrhythmia-induced cardiomyopathy

• When confronting a patient with heart failure

and any kind of tachyarrhythmias, whether atrial or ventricular, one should think about:

– Arrhythmia-induced Cardiomyopathy

• r

– Arrhythmia-aggravated Cardiomyopathy

• They should be corrected before

any decision about device implantation.

Khairy P, Stevenson W. Catheter ablation in tetralogy of Fallot. Heart Rhythm Volume 6, Issue 7, Pages 1069-1074.

Incisional Macro-reentrant VT

Focal Atrial Tachycardia

Khairy P, Stevenson W. Catheter ablation in tetralogy of Fallot. Heart Rhythm Volume 6, Issue 7, Pages 1069-1074.

36 yrs. old male TOF 3 Previous surgeries, ICD for syncopal VT Almost incessant VT Refractory to multiple anti-arrhythmic drugs Worsening functional class

Clinical VT 1

Clinical VT 2

Incessant VT

Large scars at RVOT and RV free walls

Ablation lines transecting scars ineffective

Entrainment with presystolic potential, RVOT free wall

Termination of VT during Burn at RVOT free wall

Final ECG

Incisional Right Atrial Tachycardia

Final Messages

• Conduction disturbances are common in patients

with repaired TOF and are a major source of morbidity and mortality.

• CRT is a viable option in patients with RV or

biventricular dysfunction.

• Ultimately, the best strategy is unequivocally

preventive.

• Every effort must be made intraoperatively to

preserve the integrity of the conduction system.

Keep in Mind

Think about Arrhythmia Induced Cardiomyopathy before any decision about CRT or ICD implantation.

Tehran Arrhythmia Center WWW.IranEP.org info@IranEP.org