NON INVASIVE EVALUATION OF ARRHYTHMIAS - III

Dr D SUNIL REDDY

IMPLANTABLE LOOP RECORDER

• The implantable loop recorder or insertable loop recorder (ILR) is a subcutaneous monitoring device for the detection of cardiac arrhythmias that stores events when the device is activated automatically according to programmed criteria

• This device can be useful in the evaluation of palpitations or syncope of undetermined etiology, particularly when symptoms are infrequent (eg, less than once per month).

• In such patients, conventional noninvasive testing is often negative or inconclusive.

• Among patients with neurocardiogenicsyncope, an ILR may more accurately establish a causative relationship between bradyarrhythmias and syncope than provocative tests (eg, upright tilt table testing or ATP infusion

• When an ILR is implanted in patients with syncope of uncertain cause, transient bradycardia is frequently found to be responsible .

• In one study @ of 206 patients receiving an ILR

– 69 percent had recurrent symptoms during six months of follow-up

– Recurrence was associated with a bradyarrhythmiain 17 percent

– a tachyarrhythmia in 6 percent

– Sinus rhythm in 42 percent

– Failed device activation in 4 percent.@ Krahn AD, Klein GJ, Fitzpatrick A, et al. Predicting the outcome of patients with unexplained syncope undergoing prolonged monitoring. Pacing Clin Electrophysiol2002; 25:37

PICTURE REGISTRY

• The Place of Reveal In the Care pathway and Treatment of patients with Unexplained Recurrent Syncope

• An ILR was implanted in 570 patients

• Patients were followed for at least one year or until their next syncopal episode (mean of 10 +/- 6 months).

• Recurrent syncope was noted in 218 patients (38 % )

• Data acquired by the ILR during the syncopal event directly contributed to a diagnosis in 78 % of patients.

• A cardiac etiology was found in 75 percent

• While recurrent symptoms, including syncope, occur within 6 to 12 months in 38 to 69 percent of patients, this leaves a large number of undiagnosed patients

• In one cohort of 157 patients with at least one episode of unexplained syncope who received an ILR, 70 (45 percent) were followed for greater than 18 months, some as long as four years .

• Twenty-six percent of all diagnoses made in this cohort occurred more than 18 months following ILR implantation, indicating the utility of continued ILR monitoring in patients without a definitive diagnosis for their unexplained syncope.

@ Furukawa T, Maggi R, Bertolone C, et al. Additional diagnostic value of very prolonged observation by implantable loop recorder in patients with unexplained syncope. J Cardiovasc Electrophysiol 2012; 23:67

RISK STRATIFICATION POST MI

• T here may be a role f or ILRs in the risk stratification of post -MI patient s.

• The CARISMA trial followed 1393 patients who received an ILR within 11±5 days of an acute MI , which resulted in a LVEF < 40%.

• [11]• A signif icant bradyarrhyt hmia or t achyarrhyt hmia

was document ed in 46% of pat ient s. T he development of

• int ermit t ent high-degree at riov ent ricular (AV) block was t he most pot ent predict or of mort alit y.

• VEST / PREDI CT S t rial (Vest prev ent ion of Early Sudden deat h T rial)/ (PREDict ion of I CD T herapies

• St udy) is seeking t o det ermine whet her a wearable def ibrillat or used f or t he 2 mont hs af t er inf arct ion can at t enuat e

• early mort alit y; addit ionally, it is hoped t hat met hods f or risk st rat if icat ion can be dev eloped

• Pat ient s w it h or at risk f or AF• I LRs can prov ide long-t erm ECG monit oring in pat ient s at risk f or or wit h document ed

AF.• [12]• I n t he CARI SMA t rial,• a 28% incidence of new-onset AF was observ ed.• [11]• I LRs may come t o play an import ant role in crypt ogenic• st roke pat ient s; t he CRYST AL-AF st udy is current ly prospect iv ely inv est igat ing whet her I

LRs improv e t he• diagnost ic yield ov er short -t erm ambulat ory ext ernal ECG recording t echniques in t his

pat ient populat ion.• Finally, mult iple t rials are current ly underway t o assess t he clinical ut ilit y of I LRs in pat

ient s who hav e undergone• ablat ion of AF. I t is hoped t hat t he I LR will be able t o prov ide inf ormat ion about AF

burden; t his t ype of inf ormat ion is current ly not possible t o obt ain in t he absence of an implant ed pacemaker or def ibrillat or.

UPRIGHT TILT TABLE TEST

• The upright tilt table test is commonly performed for the evaluation of syncope although the test has limited specificity, sensitivity, and reproducibility.

• It may be helpful particularly in young, otherwise healthy patients in whom the diagnosis of vasovagal (neurocardiogenic) syncope is suspected but not certain

• It is also useful in older persons in whom the cause of syncope remains unclear, but vasovagal syncope is suspected

METHODOLOGYSupine pre-tilt phase of at least 5 min, when no venous cannulation, and of at least 20 min, when cannulation is undertaken

IC

Tilt angle between 60 and 70° is recommended IB

Passive phase of a minimum of 20 min and a maximum of 45 min is recommended

IB

For nitroglycerine, a fixed dose of 300 to 400 µg sublingually administered in the upright position is recommended

IB

For isoproterenol, an incremental infusion rate from 1 up to 3 µg/min in order to increase average heart rate by ~20 to 25 percent over baseline is recommended

IB

INDICATIONS• Tilt testing is indicated in the case of an

unexplained single syncopal episode in high risk settings (eg, occurrence of, or potential risk of physical injury or with occupational implications), or recurrent episodes in the absence of organic heart disease, or in the presence of organic heart disease, after cardiac causes of syncope have been excluded

• Tilt testing is indicated when it is of clinical value to demonstrate susceptibility to reflex syncope to the patient

• Tilt testing should be considered to discriminate between relfex and OH syncope

• Tilt testing may be considered for differentiating syncope with jerking movements from epilepsy

• Tilt testing may be indicated for evaluating patients with recurrent unexplained falls

• Tilt testing may be indicated for evaluating patients with frequent syncope and psychiatric disease

• Tilt testing is not recommended for assessment of treatment

• Isoproterenol tilt testing is contraindicated in patients with ischaemic heart disease

DIAGNOSTIC CRITERIA

• In pts without structural heart disease the induction of reflex hypotension/bradycardia with reproduction of syncope or progressive OH (with or without symptoms) are diagnostic of reflex syncope and OH, respectively ( CLASS - I / LOE – B )

• In pts without structural heart disease induction of reflex hypotension/bradycardia without reproduction of syncope may be diagnostic of reflex syncope (CLASS – II a / LOE – B )

• In pts with structural heart disease, arrhythmia, or other cardiovascular cause of syncope should be excluded prior to considering positive tilt test results as diagnostic ( CLASS - IIa / LOE – C )

• Induction of LOC in absence of hypotension and/or bradycardia should be considered diagnostic of psychogenic pseudosyncope (CLASS – II a / LOE – C )

Guidelines for the diagnosis and management of syncope : the Task Force for the Diagnosis and Management of Syncope of the European Society of

Cardiology (ESC). Eur Heart J 2009; 30:2631.

DYSAUTONOMIA

VASOVAGAL SYNCOPE

POTS

ISOPROTERENOL INFUSION

• If the patient has remained asymptomatic during upright tilting, a second tilt while infusing isoproterenol is commonly done

• The patient is then placed in the head-up tilt position for an additional 15 to 20 minutes.

• Although a controlled infusion is safe in ptswithout heart disease, it should not be performed in those with CAD since angina and serious arrhythmia can be provoked

NITRATES

• Nitrates cause venodilation with consequent reduction in venous return and stroke volume, without impeding the sympathetic responses of increased heart rate and arterial vasoconstriction

• The 2009 ESC guidelines recommend a fixed dose of 300 to 400 mcg of sublingual nitroglycerin administered in the upright position for NTG tilt testing

• The addition of nitroglycerin to tilt testing increases the frequency of hemodynamic changes and reproduction of symptoms and may shorten test duration but also increases the rate of false +ve tests

Nitroglycerin has been compared to isoproterenol as an adjunct to tilt table testing :

• One study compared sublingual nitroglycerin to isoproterenol administration during tilt in 71 patients with unexplained syncope and 30 controls .

• Rates of test positivity in patients (49 and 41% respectively) were similar; however, sublingual nitroglycerin was simpler to use, better tolerated, and safer than low-dose isoproterenol. (Raviele A et al; Am J Cardiol 2000)

• In a study of 96 pts with unexplained syncope, sublingual NTG with tilt led to a higher number of positive responses than isoproterenol with tilt (55 vs 42%), espamong pts with positive tilt without pharmacologic agents (94 vs 67%) (Delépine S et al; Am J Cardiol 2002)

TEST PERFORMANCE

• The sensitivity of tilt table testing is as high as 80 percent depending upon the protocol and patient selection, but this high sensitivity is at the expense of a lowered specificity (ie, more false positive tests).

• Among individuals who undergo a tilt table test with isoproterenol, a positive response is seen in as many as 45 percent or more of those who do not have a history of syncope (in normal volunteers).

• The reported false negative rate is as high as 14 to 30 percent, but can be higher depending upon the protocol and patient age

• One report evaluated the role of this test in 145 patients with a history of presyncope or syncope. The following findings were noted :

– Patients with recurrent syncope were significantly more likely to have a positive test compared to those with a single episode or with recurrent presyncope (41 versus 17 percent).

– Patients with structural heart disease or with a noncardiovascular cause for syncope were significantly less likely to have a positive test (16 versus 42 percent)

Fitzpatrick AP, Lee RJ, Epstein LM, et al. Effect of patient characteristics on the yield of prolonged baseline head-up tilt testing and the additional yield of drug provocation. Heart 1996; 76:406

• In a study patients with vasovagal syncope compared to normal volunteers had

1. A shorter time to syncope (9.5 versus 17 minutes)

2. An immediate and persistent drop in mean BP

• Suggesting an impaired vascular resistance response; more rapid peripheral pooling of blood, as determined by LVEDD on echocardiography; and higher peak serum epinephrine levels, which probably induced increased cardiac contractility and may have contributed to impaired vasoconstriction.

Moya A, Brignole M, Menozzi C, et al. Mechanism of syncope in patients with isolated syncope and in patients with tilt-positive syncope. Circulation 2001; 104:1261

• Younger subjects are more likely to have a bradycardic response, whereas older subjects tend are more likely to have a hypotensive response

• The response to tilt testing can be highly variable such that a patient displays a cardioinhibitoryresponse on one day and a vasodepressor response on another day.

Kurbaan AS, Bowker TJ, Wijesekera N, et al. Age and hemodynamic responses to tilt testing in those with syncope of unknown origin. J Am Coll Cardiol 2003; 41:1004

COMPARISON TO ILR• Among patients with recurrent vasovagal syncope, an

implantable loop recorder can more accurately establish a causative relationship between bradyarrhythmias and syncope than upright tilt table testing

• Use of an implantable loop recorder can also help exclude an arrhythmic cause

• Tilt table and ATP test results correlate poorly with the mechanism of spontaneous reflex syncope @

@Brignole M, Sutton R, Menozzi C, et al. Lack of correlation between the responses to tilt testing and adenosine triphosphate test and the mechanism of spontaneous neurally mediated syncope. Eur Heart J 2006; 27:2232

• Based on comparison to implantable loop recordings during episodes of vasovagal syncope, tilt table testing is more likely associated with relative bradycardia and hypotension whereas spontaneous episodes are more often associated with asystole @

• Therefore an implantable loop recorder may be indicated in lieu of conventional provocative tests such as tilt table testing and ATP infusion

@ Moya A, Brignole M, Menozzi C, et al. Mechanism of syncope in

patients with isolated syncope and in patients with tilt-positive syncope. Circulation 2001; 104:1261

THE SIGNAL-AVERAGED ELECTROCARDIOGRAM (SAECG)

• It is a noninvasive technique that enables detection of the substrate for reentrant arrhythmias, particularly ventricular tachycardia.

• The SAECG is derived by computing the arithmetic mean of multiple ECG complexes. This process increases the signal-to-noise ratio of cardiac potentials and enables the detection of much smaller (ie, microvolt-level) signals than would otherwise be discernible from the surface ECG

• Signals from the His bundle as well as subtle abnormalities of atrial or ventricular complexes, anomalies not visualized on a surface ECG, are detectable using the SAECG

• The SAECG has most often been used to identify low-amplitude signals at the end of the QRS complex, referred to as "ventricular late potentials".

• These late potentials represent delayed ventricular activation, which may reflect the presence of myocardial scar tissue and identify patients at increased risk for reentrant ventricular tachyarrhythmias .

• The SAECG can be acquired by one of three methods

1. Temporal signal averaging method

2. Spatial signal averaging method

3. Spectral analysis method

1. Temporal signal averaging, the most common method for obtaining the SAECG, averages a number of QRS complexes over time.

2. Spatial signal averaging analyzes electrical potentials simultaneously recorded from multiple pairs of closely spaced electrodes.

3. Spectral analysis considers the QRS complex (or P-wave) to be composed of multiple simple waveforms, typically sinusoids.

– Spectral analysis thus decomposes the QRS complex (or P-wave) into these constituent signals for analysis.

SUCCESS OF ABLATION

• The SAECG may help guide post ablative clinical management since the absence of late potentials correlates well with the inability to induce VT after surgical resection.

• Approximately 90 percent of patients with a normal post-surgical SAECG do not have inducible VT.

• Conversely, late potentials are present in 85 to 100 percent of patients in whom VT remains inducible.

Marcus NH, Falcone RA, Harken AH, et al. Body surface late potentials: effects of endocardial resection in patients with ventricular tachycardia. Circulation 1994; 70:632

• In a study catheter ablation at regions of intra-ventricular late potentials reduced the incidence of ICD therapy on long-term follow-up @

• In a study of 18 patients with arrhythmogenic right ventricular cardiomyopathy, elimination of late ventricular potentials by radiofrequency ablation predicted arrhythmia-free survival after a mean of 5 years follow-up #

@ Reddy VY, Reynolds MR, Neuzil P, et al. Prophylactic catheter ablation for the prevention of defibrillator therapy. N Engl J Med 2007; 357:2657.

# Oginosawa Y, Nogami A, Soejima K, et al. Effect of cardiac resynchronization therapy in isolated ventricular noncompaction in adults: follow-up of four cases. J Cardiovasc Electrophysiol 2008; 19:935.

P-WAVE SAECG AND AF

• Reentrant arrhythmias in the atrium, analogous to those in the ventricle, also likely require heterogeneities in slow conduction and repolarization.

• This provides a theoretical basis for prediction of the propensity for atrial fibrillation (AF) by SAECG by examining slow conduction in the atrium, analogous to the detection of ventricular late potentials.

• The P-wave SAECG recorded during sinus rhythm has therefore been developed to identify:

– Patients with paroxysmal AF

– The frequency and duration of recurrent episodes of AF

– Patients at risk for developing AF.

• Patients with paroxysmal AF may be identified by P-wave prolongation on the SAECG during sinus rhythm

• In a study vector P-wave duration of 155 mspredicted AF with a sensitivity, specificity, and positive predictive accuracy of 80, 93, and 92 percent, respectively

Guidera SA, Steinberg JS. The signal-averaged P wave duration: a rapid and noninvasive marker of risk of atrial fibrillation. J Am Coll Cardiol 1993; 21:1645

TRANSITION TO CHRONIC AF

• It remains unproven whether the risk for recurrent or sustained episodes of AF can be predicted from the P-wave SAECG.

• In one series, 122 patients with paroxysmal AF were followed for 26 months

• An SAECG P-wave duration greater than 145 ms and terminal 30 ms P-wave voltage less than 3.0 mV indicated a significantly greater risk of progression to chronic AF

Abe Y, Fukunami M, Yamada T, et al. Prediction of transition to chronic atrial fibrillation in patients with paroxysmal atrial fibrillation by signal-averaged electrocardiography: a prospective study. Circulation 1997; 96:2612

DEVELOPMENT OF AF• Preliminary data suggest that the development of AF

can be predicted using analyses of the P-wave from the SAECG in certain patient populations

• For example, in pts undergoing elective cardiac surgery, P-wave duration greater than 155 msprovided a sensitivity, specificity, PPV and NPV accuracy for the development of AF of 69, 79, 69, and 82 percent, respectively

• Some studies suggest that analysis of the P-wave SAECG predicts the propensity to AF more accurately than left atrial dimensions

Stafford PJ, Kolvekar S, Cooper J, et al. Signal averaged P wave compared with standard electrocardiography or echocardiography for prediction of atrial fibrillation after coronary bypass grafting. Heart 2000; 77:417

• Among patients with HCM, the combination of a P wave duration of 140 ms and LAE (>40 mm) has been a/w a specificity and PPV for AF of 93 and 78 percent, respectively

• A sub-study analysis of MADIT II found that abnormalities of P wave shape in X, Y and Z axis ECGs predicted AF onset and sudden cardiac arrest in 802 patients with ischemic cardiomyopathy and LVEF ≤30 percent

• P wave morphology changed over time in patients from the MADIT II study who later developed AF, but remained unchanged in those who did not

Holmqvist F, Platonov PG, McNitt S, et al. Abnormal P-wave morphology is a predictor of atrial fibrillation development and cardiac death in MADIT II patients. Ann Noninvasive Electrocardiol 2010; 15:63

INCIDENCE OF AFib AFTER CABG

THANK YOU

definition of late potentials :

• Filtered QRS duration >114 msec

• Terminal (last 40 msec) QRS root mean square voltage <20 mcV

• Low amplitude (<40mcV) late potential duration >38 msec