Heart Rhythm Refresher Course 2014Heart Rhythm Refresher Course 2014Sudden Cardiac Death, Ventricular Arrhythmias

and ICD Therapy

ICD Implantation:

Techniques and Trouble-shooting

Dr Chan Kwok KeungDepartment of Medicine

PYNEH, Hong Kong6 Apr 2014

ICD Implantation:ICD Implantation:Techniques and Trouble-shootingTechniques and Trouble-shooting

1. ICD implantation procedure (briefly on the standard procedure)

2. Special situations, trouble-shooting and management

Venous access and lead placement What is Current of Injury (COI)? Defibrillation threshold (DFT) testing

ICD: Conception 1966ICD: Conception 1966Dr Mirowski

ICD: Conception 1966ICD: Conception 1966Over-the-counter electronic components

ICD: First Human Implant 1980ICD: First Human Implant 1980Dr Winkle, Dr Mirowski, the first ICD patient, Dr Heilman

ICD: First Human Implant 1980ICD: First Human Implant 1980A transvenous lead in SVC and a ventricular patch lead

Evolution of ICD TherapyEvolution of ICD Therapy

Benefits of ICD therapy:Benefits of ICD therapy:

1. Identify the target population

2. Implant the ICD successfully

3. Optimize the ICD programming

ICD Implant Procedure (briefly)ICD Implant Procedure (briefly)

1. Preparation for implantConsent. Model selection. Financial arrangement.

Blood tests. Antibiotics prophylaxis. Defibrillation pads. The team and the necessary equipment.

2. Venous access, pocket and lead placementCephalic cut-down or subclavian/axillary puncture.Single or dual chamber ICD.Active or passive fixation.

3. Lead testingDF-4 connector vs IS-1/DF-1 connectorAssess P-wave/R-wave, pacing/defibrillation impedance, pacing threshold

ICD Implant Procedure (briefly)ICD Implant Procedure (briefly)

4. Defibrillation threshold (DFT) testingSedation.VF induction by shock-on-T, burst stimulation,

direct current shock.Rescue shock by external defibrillator standby.Intracardiac electrogram analysis.

5. Pocket closure. Postoperative care. Device programming. CXR. Drug adjustment.

Subclavian ApproachSubclavian Approach

Cephalic ApproachCephalic Approach

ICD PocketICD Pocket

DF-4

DF-1

DF-4 leadone connection between the lead and the device, with a single distal set screw to the tip electrode.more convenient and reduce header size.the use of spring contacts (IS-1/DF-1 connector use set screws to ensure high and constant contact pressure). High-and low-voltage applications in the same cavity (in IS-1/DF-1 devices, low- and high-energy contacts in separate cavities, embedded in non-conducting material).

ICD implantICD implant

ICD Implant Procedure: ICD Implant Procedure: ComplicationsComplications

1. General: cardiac, pulmonary, neurological,etc.2. Related to the ICD lead and pulse generator pocket hematoma (subclavian puncture) pneumothorax,

hemothorax, subclavian artery puncture, air embolism, subclavian A-V fistula

ICD system infection lead dislodgement, lead perforation, lead wire

fracture/insulation break Venous thrombosis etc

SPECIAL SITUATIONS, SPECIAL SITUATIONS, TROUBLE-SHOOTING AND TROUBLE-SHOOTING AND MANAGEMENTMANAGEMENTVenous access and lead placementVenous access and lead placement

Special situations, trouble-shooting Special situations, trouble-shooting and managementand management

Venous access and lead placement (1): Persistent left superior vena cavaICD lead with long usable lengthactive fixation mechanismOff SVC coil in DFT testing (SVC coil in posterior position)Alternative approach: Right-side implant after venogram

Special situations, trouble-shooting Special situations, trouble-shooting and managementand management

Venous access and lead placement (2): Multiple ICD leadsvenogram to confirm vein patencyactive fixation mechanism desirablesome separation in venous puncture site if feasiblesome separation between different ICD coils in multiple fluoroscopic views

Special situations, trouble-shooting Special situations, trouble-shooting and managementand management

Venous access and lead placement (3): Right-side ICD implant

Options available:Right-side implant after venogramVenoplastyEpicardial leadsSubcutaneous ICD (S-ICD)

Subcutaneous ICD (S-ICD)Subcutaneous ICD (S-ICD)

45cm lead with good strength and durability

8-cm shocking coil, 2 sensing electrodes

Electrode was positioned parallel to & 1-2cm to the left of sternal midline

Pulse generator over the 6th rib between the mid- & anterior- axillary line

80-J shocks, up to 5 shocks, reverse shock polarity

Bardy GH, et al.An entirelysubcutaneous ICD.NEJM 2010:363(1);36-44

Subcutaneous ICD (S-ICD)Subcutaneous ICD (S-ICD)

Limitations of S-ICD:

1.No conventional pacing capability

(Post-shock pacing 200mA, 50ppm, maximum 30 seconds, demand-based)

2.No anti-tachycardia pacing (ATP) function

3.Unable to upgrade to CRT-D

4.S-ICD contraindicated for use with unipolar pacemakers

Special situations, trouble-shooting Special situations, trouble-shooting and managementand management

Venous access and lead placement (4): Pacemaker RV lead perforationActive fixation RV lead for a MRI compatible modelEmergency operation with intra-operative findings: RV pacing wire perforated via RV apex, then via pericardium and pleura; defect over pericardium 0.5cm; 1L blood and clots inside left pleural cavity.

SPECIAL SITUATIONS, SPECIAL SITUATIONS, TROUBLE-SHOOTING AND TROUBLE-SHOOTING AND MANAGEMENTMANAGEMENTCurrent of InjuryCurrent of Injury

What is Current of Injury (COI)?What is Current of Injury (COI)?

During implant procedure, injury to myocardium during lead placement as shown on intracardiac electrogram.

More prominent in active lead than passive leadactive fixation – helical screw into myocardium

traumaticallypassive fixation – axial pressure on lead-myocardium

interface

Current of Injury (COI)Current of Injury (COI)

COI at implant (RV passive lead)

10 minutes later…

Current of Injury (COI)Current of Injury (COI)

Consider threshold values and COI COI subsides in 5-10 minutes usually

Saxonhouse et al. Current of injury predicts adequate active lead fixation in permanent pacemaker/defibrilaltion leads. JACC 2005; 45(3): 412-7.

V lead. COI ST elevation A lead. COI ST elevation

Active >5mV or >25% ST elevation >1mV or >25% ST elevation

Passive >2mV >0.2mV

Current of Injury (COI)Current of Injury (COI)

COI confirms lead stability Active leads have more prominent COI than

passive leads Lack of COI indicates increased risk of lead

dislodgement COI with high pacing threshold: consider to

recheck threshold 5-10 mins later before reposition.

SPECIAL SITUATIONS, SPECIAL SITUATIONS, TROUBLE-SHOOTING AND TROUBLE-SHOOTING AND MANAGEMENTMANAGEMENTDefibrillation threshold (DFT) testingDefibrillation threshold (DFT) testing

Defibrillation Threshold (DFT) Testing. Defibrillation Threshold (DFT) Testing. Is it necessary? Is it necessary?

64,227 initial ICD implant between April to Dec 2010 in the NCDR Registry (National Cardiovascular Data ICD Registry; ~90% of all ICDs implanted in US) analyzed retrospectively.

DFT testing not performed in 29% patients and more likely to have:- heart failure

- lower LVEF

- atrial arrhythmias (e.g. AF)- primary prevention indication

- CRT-D implant

Russo AM, et al. Patient, physician and procedural factors influencing the use of DFT testing during initial ICD insertion. Pacing Clin Electrophysiol.

2013;36(12):1522-1531.

DFT Testing. Is it necessary?DFT Testing. Is it necessary?

ICD implant manuals approved by FDA include DFT testing.

But . . .1.Better ICD devices nowadays and lead diagnostics without performing a shock.

2.Risks of DFT testing (0.016% mortality; 0.026% stroke/TIA)

3.Not guarantee clinically successful defibrillation (with heart failure, ischemia, electrolyte abnormalities).

4.Previous trial: No relationship between DFT testing and outcome in SCD-HeFT trial

1.Birnie D, et al. Complications associated with DFT testing: The Canadian experience. Heart Rhythm 2008;5:387-390.

2.Blatt JA, et al. No benefit from DFT testing in SCD-HeFT trial. J Cardiovasc Electrophysiol 2007; 4: S81.

DFT Testing. Is it necessary? DFT Testing. Is it necessary?

No consensus

In real-world clinical practice, paradoxically, those sicker patients not having DFT testing may be most likely to benefit from testing.

Ongoing Shockless Implant Evaluation (SIMPLE) trial (but not powered to evaluate mortality).

“To test or not to test” vs “ For which patients is testing important”

Defibrillation threshold (DFT)Defibrillation threshold (DFT)

The minimum amount of energy required to reliably defibrillate the heart.

Note: DFT is not a static value and may change over time, with drugs, and with disease progress.Successful defibrillation is probabilistic. So although the term threshold is used, there is no single energy level that is always successful clinically.

Defibrillation Threshold (DFT) TestingDefibrillation Threshold (DFT) Testing

Traditional practice: Perform 2 VF inductions with defibrillation energy 10J below the maximum device output (i.e. a 10-J safety margin; not actually the threshold).

Alternative approach: Upper limit of vulnerability (ULV) is the lowest energy shock that does not induce VF when delivered during the vulnerable phase of ventricular repolarization. A 5-J ULV safety margin is suggested.

High Defibrillation Threshold (DFT) High Defibrillation Threshold (DFT) ManagementManagement

1. Rule out pneumothorax, loose set-screw

2. Reposition RV lead (to a more apical-septal position). Reverse polarity. Programmable waveform tilt/pulse width (if available)

3. High output device

4. Add SQ away/additional coils

Add empiric sotalol/stop amiodarone

Question Time Question Time .. .. ..

A 50-year-old man with dilated cardiomyopathy had a single-chamber ICD implanted for primary prevention indication.

An active lead was placed at the RV septum due to poor sensing in RV apex.

One week later, he presented to A&E Department for multiple ICD shocks while at home, asymptomatic.

There is no change in medications and all blood tests were normal.

CXR showed the lead was dislodged to the level of tricuspid annulus.

ICD Trouble-shootingICD Trouble-shooting

ICD interrogation for one of the device shocksICD interrogation for one of the device shocks

A shock (Rx1 Defib) was given for the device diagnosis of “VF”.Oversensing of the atrial signal by the ICD lead causing double counting and inappropriate shocks.

DDx:

1.T wave oversense due to T wave amplitude/ morphology changes e.g. hyperkalaema

2.T wave oversense due to QT interval change e.g. antiarrhythmia drugs

3.Artefacts due to lead fracture

4.Electromagnetic interference

The patient was admitted to Medical General ward. Due to tight CCL schedule, the lead revision was scheduled 3 days later. The patient had a cardiac arrest the day before operation and resuscitated.

ICD interrogation for the last device shock

VP VP

Oversensing A signal (double counting) leads to inappropriate shock.

The last device shock is proarrhythmic and causes VF. VF is not sensed by the ICD due to the low

arrplitude of the ventricular electrogram. The ICD initiates ventricular pacing (VP) during VF.

What will be your management for this patient with a dislodged ICD lead if you see her in medical ward as a cardiac consult?

Deactivation of the ICD with intensive cardiac monitoring (e.g. CCU) until lead revision

Arrange early lead revision asap.

SummarySummary

Implant procedureSpecial situations: persistent Lt SVC,

multiple leads, occluded subclavian vein, RV lead perforation

Current of Injury during implantDFT testing and high DFT

management

ENDEND

1.1. Basic ICD programmable parametersBasic ICD programmable parameters

2.2. Evidence from recent clinical trialsEvidence from recent clinical trials

3.3. SummarySummary

How Should I Program an ICD?Evidence and Experience

Dr Chan Kwok KeungDepartment of Medicine

PYNEH, Hong Kong6 April 2014

Two goals for a therapy:Two goals for a therapy:Two goals for a therapy:Two goals for a therapy:

1. To help patients feel better

2. To help patients live longer

or both.

1. Financial cost

2. Morbidity of ICD therapy complication of implant procedure device alert/recall, lead failure(not discussed) inappropriate therapy

(appropriate but) unnecessary therapy affected by ICD programming and antiarrhythmic drugs.(this lecture will focus on ICD programming)

ICD improves survival, but at what cost?ICD improves survival, but at what cost?

atrial arrhythmias (AF, atrial flutter, SVT) oversensing due to lead fracture noise or overcounting

(T-wave oversensing, EMI, myopotentials)

Causes for inappropriate therapy (Shock or ATP)

Too aggressive treatment of VT than absolutely requiredshock or ATP for premature detection of non-sustained VT; premature ATP may accelerate NSVTShock for sustained pace-terminable VT

Causes for unnecessary therapy (Shock or ATP)

Implantable Cardioverter Defibrillator (ICD)Implantable Cardioverter Defibrillator (ICD)

Sensing Detection Therapy

ICD treats ventricular tachyarrhythmias

Sensing in ICD: A major challenge…Sensing in ICD: A major challenge…

A A wide variationwide variation in the size of signals in the size of signals

stable and large normal ventricular signalsstable and large normal ventricular signals

low amplitude VF signalslow amplitude VF signals

Sensing in ICDSensing in ICD

Beat-to-beat auto-adjusting sensitivityBeat-to-beat auto-adjusting sensitivity

Sensing in ICD

DetectionDetection

Ventricular Fibrillation (VF)Ventricular Fibrillation (VF) Rate cut-off (VF zone)Rate cut-off (VF zone) Number of intervals for detectionNumber of intervals for detection

(usually consecutive intervals not required; (usually consecutive intervals not required; high sensitivity)high sensitivity)

Ventricular Tachycardia (VT)Ventricular Tachycardia (VT) Rate cut-off [VT zone(s)]Rate cut-off [VT zone(s)] Number of intervals for detectionNumber of intervals for detection Detection Enhancement/ SVT Discriminator Detection Enhancement/ SVT Discriminator

Detection EnhancementDetection Enhancement

Current electrogram signal compared with Current electrogram signal compared with stored normal templatestored normal template

Match percentage = 1 - (area of difference)Match percentage = 1 - (area of difference)

Electrogram MorphologyElectrogram Morphology

Detection EnhancementDetection EnhancementStabilityStability To reduce inappropriate detection of atrial arrhythmias To reduce inappropriate detection of atrial arrhythmias

eg atrial fibrillation (rhythm not “stable” i.e. variable eg atrial fibrillation (rhythm not “stable” i.e. variable cycle length)cycle length)

Each interval compared to previous intervalsEach interval compared to previous intervals Count as VT if the difference Count as VT if the difference the programmed the programmed

stability interval i.e. stability interval i.e. VT is “stable”VT is “stable”

VT detection interval: 500msStability 30ms

Detection Detection EnhancementEnhancement

OnsetOnset To reduce inappropriate detection of sinus To reduce inappropriate detection of sinus

tachycardiatachycardia

Average of current 4 intervals is compared to Average of current 4 intervals is compared to average of previous 4 intervalsaverage of previous 4 intervals

Current average programmedCurrent average programmedPreviousPrevious average onset percentageaverage onset percentage

i.e. i.e. onset is “sudden” in VTonset is “sudden” in VT

Detection Enhancement: OnsetDetection Enhancement: OnsetOnset percentage: 81%

Dual-chamber ICD: SVT discriminatorDual-chamber ICD: SVT discriminator

Dual-chamber ICD: SVT Dual-chamber ICD: SVT discriminatordiscriminator

PR Logic – Pattern and Rate Analysis

Discrimination of Lead NoiseDiscrimination of Lead Noise

Caused by pace-sense conductor fracture, loose set Caused by pace-sense conductor fracture, loose set screw, lead insulation breach.screw, lead insulation breach.

Therapy avoided by comparing near-field channel (RV Therapy avoided by comparing near-field channel (RV tip to RV ring) to far-field channel (RV tip to Can/RV coil tip to RV ring) to far-field channel (RV tip to Can/RV coil to Can).to Can).

ICD TherapyICD Therapy

1. Defibrillation (in VF zone)1. Defibrillation (in VF zone) Biphasic waveform high energy shockBiphasic waveform high energy shock

2. Cardioversion (in VT zone)2. Cardioversion (in VT zone) Synchronized biphasic waveform shock Synchronized biphasic waveform shock

ranges from < 1J to high energyranges from < 1J to high energy

3. Antitachycardia pacing (in VT zone)3. Antitachycardia pacing (in VT zone) Attempt to terminate VT with rapid pacingAttempt to terminate VT with rapid pacing Patient more comfortable and therapy Patient more comfortable and therapy

energy-savingenergy-saving

4. Bradycardia pacing4. Bradycardia pacing

High-energy DefibrillationHigh-energy Defibrillation

Biphasic waveforms are more effective than monophasic Biphasic waveforms are more effective than monophasic waveformswaveforms

CapacitorsCapacitors act as high-voltage storage tanks. The act as high-voltage storage tanks. The battery can ‘pump’ energy into the capacitor which holds battery can ‘pump’ energy into the capacitor which holds up the energy. So a 3.2V battery can fill a capacitor to up the energy. So a 3.2V battery can fill a capacitor to ~30-36J (700-800V) to defibrillate the heart.~30-36J (700-800V) to defibrillate the heart.

Monophasic Biphasic

Defibrillation threshold (DFT)Defibrillation threshold (DFT)

The minimum amount of energy required The minimum amount of energy required to reliably defibrillate the heart.to reliably defibrillate the heart.

Note: DFT is not a static value and may change over time, with drugs, and with disease progress.Successful defibrillation is probabilistic. So although the term threshold is used, there is no single energy level that is always successful clinically.

Probability of Successful Defibrillation Probability of Successful Defibrillation and Shock Strengthand Shock Strength

0

25

50

75

100

125

0 5 10 15 20

Energy (Joules)

% S

ucce

ss

Low Energy CardioversionLow Energy Cardioversion

For termination of ventricular For termination of ventricular tachycardiatachycardia

Shocks delivered at 0.1J up to several Shocks delivered at 0.1J up to several Joules, synchronized to R waveJoules, synchronized to R wave

Shocks under 2J are much comfortable Shocks under 2J are much comfortable for patientsfor patients

Antitachycardia Pacing (ATP)Antitachycardia Pacing (ATP)

Antitachycardia Pacing (ATP)Antitachycardia Pacing (ATP)

ATP is not painfulATP is not painful

ATP consumes minimal amount of batteryATP consumes minimal amount of battery

May be effective in some VTs, but may also May be effective in some VTs, but may also be proarrhythmicbe proarrhythmic

PainFREE Rx 2 study: ATP terminated 73% PainFREE Rx 2 study: ATP terminated 73% of fast VT (18 of 24 intervals, 188-250bpm).of fast VT (18 of 24 intervals, 188-250bpm).Wathen MS, et al. PainFREE Rx 2. Circulation 2004;110:2591-96.Wathen MS, et al. PainFREE Rx 2. Circulation 2004;110:2591-96.

Evidence from recent Evidence from recent trialstrials

Quick detection: the longer the arrhythmia, the more likely a patient to have symptoms e.g. syncope

Lower cut-off rate: if a higher cut-off rate is used, a haemodynamically significant VT will be missed, leading to syncope or VF.

But primary prevention indications were uncommon in the past.

Traditional Concept in the past

Is the ICD programming appropriate to Is the ICD programming appropriate to the patient needs?the patient needs?

atrial arrhythmias (AF, atrial flutter, SVT) oversensing due to lead fracture noise or overcounting

(T-wave oversensing, EMI, myopotentials)

Causes for inappropriate therapy (Shock or ATP)

Too aggressive treatment of VT than absolutely requiredshock or ATP for premature detection of non-sustained VT; premature ATP may accelerate NSVTShock for sustained pace-terminable VT

Causes for unnecessary therapy (Shock or ATP)

A randomized, single-blind, multicenter clinical study

1500 patients with either ischaemic or nonischaemic disease with an indication for a primary-prevention dual-chamber ICD or CRTD. Patients with atrial fibrillation or device replacement excluded.

Patients were assigned to one of three ICD programming groups with the primary objective of finding their rate of a first occurrence of inappropriate ATP or shocks.

Reduction in Inappropriate Therapy and mortality through ICD Programming

(MADIT-RIT trial)

Moss A., etal. NEJM 2012; 367: 2275-83

MADIT-RIT: Three Treatment ArmsArm A(Conventional)

Arm B(High-rate)

Arm C(Duration-delay)

Zone 1:170 bpm, 2.5s delayOnset/Stability Detection Enhancements ONATP + Shock

Zone 1:170 bpmMonitor only

Zone 1:170 bpm, 60s delayRhythm ID Detection Enhancements ONATP + Shock

Zone 2:200 bpm, 1s delayQuick Convert ATP Shock

Zone 2:200 bpm, 2.5s delayQuick Convert ATP Shock

Zone 2:200 bpm, 12s delayRhythm ID Detection Enhancements ONATP + Shock

Zone 3:250 bpm, 2.5s delayQuick Convert ATP + Shock

The ICD was not a new type of ICD.

The programming choices were not new.

Aim to ignore the slower

tachyarrhythmias in High-rate and those

of shorter duration in Duration-delay.

NOTE:

During an average follow-up of 1.4 years, high-rate therapy and delayed ICD therapy, as compared with conventional device programming, associated with- reduction in a first occurrence of inappropriate therapy- reduction in all-cause mortality- no significant difference in adverse events

e.g. syncope There was significant reduction by more than 70% of

inappropriate therapy in both high-rate and delayed therapy groups

Mortality was reduced by 55% in high-rate group (p=0.01) and by 44% in the delayed-therapy group (p=0.06).

MADIT-RIT Results

Lession: Treat sustained tachyarrhythmias only

It does not favor quick detection and therapy.

MADIT-RIT

Note that in MADIT-RIT:

•primary prevention indication only

•dual-chamber ICD and CRT-D only

•exclude AF patients.

A randomized, single-blind study to determine whether using 30 of 40 intervals to detect VT (long detection) reduces ATP and Shock compared with 18 of 24 intervals (standard detection).

Patients with primary or secondary prevention, single- or dual-chamber ICD or CRT-D, sinus or AF.

Effects of Long-detection Interval vs Standard-detection Interval for ICDs on

Antitachycardia Pacing and Shock Delivery

(ADVANCE III trial)

Gasparini M, et al. JAMA 2013; 309:1903-11

After a median follow-up of 1 year, the long-detection group had significantly less ICD therapies (ATP and shocks) and inappropriate shocks.

There was significant reduction in all-cause hospitalizations.

No difference in arrhythmia syncope and mortality.

Lession: Broaden the long detection applicability to include secondary prevention, single-

chamber ICD and AF patients.

ADVANCE III trial Results:

A non-randomized trial with primary endpoint of the rate of inappropriate shocks at one year post implant.

Single chamber ICD, primary or secondary prevention, initial implant or replacement, sinus or AF.

A special detection algorithm includes wavelet morphology analysis, discriminating T wave, assessment of lead integrity or noise and improved recognition of nonsustained episodes.

Inappropriate shock rates in patients with single chamber ICDs using a novel suite of

detection algorithms(PainFree SST study)

Meijer A, et al. Europace June 2013

757 patients with single-chamber ICD

97.6% of patients free of inappropriate shocks during the first year post implant.

Lession: reducing inappropriate shock rate below 3% at 1 year is possible

PainFree SST study Results

A randomized study of primary prevention ICD (single or dual chamber or CRTD) in 1670 patients.

A combination of programmed parameters (higher detection rates, longer detection intervals, empiric ATP, SVT discriminators) vs conventional parameters.

Result: reduced ICD therapies without increasing arrhythmic syncope and reduced all-cause mortality.

Programming ICDs in patients with primary prevention indication to prolong

time to first shock(PROVIDE study)

Saeed M, et al. J Cardiovasc Electrophysiol 2014; 25(1): 52-59

A non-randomized retrospective analysis of 300 ICD patients of various manufacturers.

Strategic ICD programming to reduce shocks.

64% risk reduction in primary endpoint (composite of death and appropriate shocks) and 70% reduction in inappropriate shocks.

Safety and efficacy of strategic ICD programming to reduce shock delivery burden in a primary prevention patient population

Buber J, et al. Europace 2014; 16(2): 227-234

4896 patients from MADIT-RIT, ADVANCE 3, PROVIDE, RELEVANT.

Reduced mortality by 23%

Reduced inappropriate shocks and both appropriate and inappropriate ATP significantly.

The impact of prolonged arrhythmia detection times on outcomes: a meta-analysis

Scott PA, et al. Heart Rhythm 2014; D01: 10.1016. Abstract.

1. ICD therapy has morbidity. The benefits of an ICD are greatly affected by its programming

2. Avoid inappropriate therapy and unnecessary therapy

(less pain, less hospitalization, better QOL, improved survival).

3. To be certain that there is a sustained tachyarrhythmia before treating the rhythm

prolonged duration of arrhythmia detection faster rate of arrhythmia detection use of ATP algorithms for discrimination of SVT

SummarySummary

ENDEND