Device therapy –Diagnostic and Therapeutic
Marilyn M. Cox M.D., F.A.C.C.
Overview of Device Therapy
Implantable loop recorders
Pacemakers
Implantable Cardioverter-Defibrillators- Single, Dual, Biventricular and Sub Q
Future devices
Extended EKG monitoring
Choice of monitoring should depend upon the frequency of the patient's symptoms
Daily symptoms-24 hour holter
Weekly symptoms-30 day event recorders
Monthly or less – Implantable loop recorders
External recording systems
Cardionet-30 day wireless, non-looping, looping and auto-trigger monitors, detects and automatically transmits asymptomatic and symptomatic events.
Lifewatch-sensor and electrodes are worn on chest , wireless transmission of heart beat to cellular phone monitor where it is analyzed. If arrhythmia is detected cell phone automatically sends it monitoring center
SEEQ- 30 day monitor, continuous wireless data collection and transmission, sensor patch adheres to skin, 7 day sensor
Preventice eCardio-detects, records and wirelessly transmits data to support remote monitoring. Sensor adheres to patient’s skin and is smaller than cell phone
Looping multi-event monitors
Looping refers to memory of the monitor, when activated monitor can save the previous 60 seconds of data and 30 seconds post activation
Patient activated
Program to record 1-6 events
Advantage of implantable loop recorders
Small
No external EKG patches or wires
No need to rely on patient to record
Reveal XT versus Reveal Linq
REVEAL LINQ Insertable Cardiac Monitoring System
Miniaturized cardiac monitoring for up to 3 years
Continuous , wireless data collection, trending and transmission
24/7 physician access to reports with automatic notification for clinically relevant events
Reveal Linq Implantable Cardiac Monitor
20% more data memory than previous models
Improved AF detection
Three year longevity
MRI conditional at 1.5 and 3.0 Tesla
Comes preloaded in insertion tool
Requires only local anesthesia
Implantable loop recorder kit
Insertional tool loaded with implantable loop recorder
Objectives of CRYSTAL AF
To assess whether a long term monitoring strategy with an insertable cardiac monitor (ICM) is superior to standard medical care for the detection of AF in patients with cryptogenic stroke at 6 months( primary endpoint) and 12 months( secondary endpoint)
Determine the proportion of patient with cryptogenic stroke that have underlying AF
Determine actions taken after patient is diagnosed with AF
Crystal AF trial
Crystal AF
Secondary Endpoint: Detection of AF at 12 monthsICM finds 7x more patients with AF
Rate of detection in ICM arm was 12.4% vs 2.0% in control arm
Crystal AF trial
Indications for pacing
Documented non-reversible symptomatic bradycardia due to sinus node dysfunction Documented non-reversible symptomatic bradycardia due to second degree and/or third degree heart block
Symptoms of bradycardia directly attributable to a heart rate less than 60 BPM
Syncope
Seizures
Congestive heart failure
Dizziness
Confusion
Pacing not indicated-according to CMS
Reversible causes of bradycardia such as electrolyte abnormalities, medication or drugs and hypothermia
Asymptomatic first degree AV block
Asymptomatic sinus bradycardia
Asymptomatic sino-atrial block or asymptomatic sinus arrest
Asymptomatic Mobitz type I AV block (Wenckebach) unless QRS complexes are prolonged or EPS shows block is at or below the His bundle
Syncope of undetermined cause
Bradycardia during sleep
Asymptomatic bradycardia
Pacing not indicated according to CMS
Asymptomatic bradycardia in post MI patients about to initiate long term beta blocker therapy
Right bundle branch block and left hemiblock without syncope or symptoms of intermittent AV block
Frequent or persistent SVT except where pacemaker is for control of tachycardia
A clinical condition in which pacing takes place only intermittently and briefly and which is not associated with reasonable likelihood that pacing will not become prolonged
What information does a pacemaker interrogation give us?
Battery life, serial numbers
Implant data, patient characteristics, indication
Lead characteristics( P and R wave amplitude, impedance, pacing threshold)
Heart rate histograms
Mode switch episodes ( number and percentage of total time)
Arrhythmia recordings- SVT, A fib, VT, VF
Intracardiac electrograms of the arrhythmias
Rate, number of episodes, date and time of episodes, duration of individual episode
MRI Conditional Pacemakers
Why is an MRI conditional pacemaker important?
MRI is predominantly used to diagnose back and joint pain, stroke symptoms and cancer
Also used to examine the abdomen, pelvis, breast , blood vessels and heart
49% of patients with a stroke or TIA undergo an MRI within 3 days of symptoms but patients with traditional pacemakers cannot
86% of pacemaker patients are older than 65 and prevalence of common morbidities increase over age 65
MRI is the standard or care for these multiple morbidities
Cardiology conditions for use of an MRI
No lead extenders, lead adaptors or abandoned leads
No broken leads or leads with intermittent electrical contact as confirmed by lead impedance history
System has been implanted for at least 6 weeks
System has been implanted in the right or left pectoral area
Pace polarity parameters set to Bipolar for programming MRI sure scan to on
Pacing capture thresholds of less than or equal to 2 V at 0.4 ms,
Lead impedance of >200 ohms and < 1500 ohms
No diaphragmatic stimulation at 5V and pulse width of 1ms in patients whose device will be programmed to an asynchronous mode
Source: Medtronic
Radiology conditions for use of an MRI
Full body MRI is now allowed, no restrictions
Horizontal cylindrical bore magnet, clinical MRI systems with a static magnetic field of 1.5 Tesla must be used
Gradient systems with max slew rate performance per axis of < or = to 200 Tesla/m/sec must be used
Scanner must be in normal operating mode: whole body average specific absorption rate (SAR) < or = to 2 W/kg; head SAR must be <or = 3.2W/kg
Proper patient monitoring must be provided including visual and verbal contact with patient and heart rate monitoring with pulse ox or EKG
An external defibrillator must be available nearby during the MRI scan
Source: Medtronic
MRI precautions
Do not scan patients with a whole body average SAR of >2W/kg as this may increase the risk of myocardial tissue damage due to lead tip heating
Do not scan patients with capture thresholds >2 V at 0.4 ms as this indicate that there is a problem with the implanted lead
Do not scan patients whose device will be programmed to an asynchronous mode who have diaphragmatic stimulation at 5V at 1 ms as it may be difficult for patient to remain still in order to obtain a quality image
Use of lead extenders or lead adaptors is not recommended as they may increase the risk of myocardial tissue damage due to lead tip heating and other MRI field related hazards
Scanning patients with multiple MR conditional devices is acceptable as long as the MR labeling conditions for all implants can be satisfied
Indications for Implantable Cardioverter Defibrillators
Primary prevention
Secondary prevention
ICDs for the Secondary Prevention of Sudden Cardiac Death
Survivors of cardiac arrest due to VF or hemodynamically unstable VT
Completely reversible causes of VF or VT are not covered
ICDs for the Primary Prevention of Sudden Cardiac Death
Patients with ischemic dilated CM , documented prior MI, NYHA functional Class II and III and LV EF less than or equal to 35%
Patients with non-ischemic dilated CM greater than 3 months, NYHA functional class II and III and LV EF less than or equal to 35%
LV dysfunction due to prior MI and at least 40 days post MI, EF less than 30% and NYHA functional Class I
Hypertrophic cardiomyopathy and risk of SCD
Long QT syndrome and risk of SCD
Brugada syndrome and risk of SCD
Disqualifiers for ICD implantation for Primary prevention
Patient unable to give informed consent
Cardiogenic shock or symptomatic hypotension while in a stable baseline rhythm
CABG or PCI within the past 3 months
Acute MI within the last 40 days
Clinical symptoms that would make patient a candidate for revascularization
Irreversible brain damage from preexisting cerebral disease
Any disease other than cardiac disease (e.g. cancer, uremia, liver failure associated with a survival of less than one year
Goal of Cardiac Resynchronization therapy
Reestablish synchronous contraction between the left ventricular free wall and the ventricular septum in an attempt to improve left ventricular efficiency and subsequently to improve functional class
Benefits of Cardiac Resynchronization therapy
Improve pump performance
Reduce functional mitral regurgitation
Reverse adverse effects of ventricular remodeling in patients with heart failure
Reduce mortality
Reduce heart failure symptoms
Reduce heart failure hospitalizations
Schematic of Biventricular ICD
Coronary sinus venogram
Biventricular ICD
MADIT CRT-
Designed to determine whether cardiac resynchronization therapy (CRT) with biventricular pacing would reduce the risk of death or heart failure in patients with mild symptoms, a reduced EF and a wide QRS complex
1820 patients with ischemic or non-ischemic CM, EF of 30% or less, QRS 130ms or more, NYHA functional Class I or II symptoms
Patients randomly assigned in 3:2 ratio to receive CRT plus ICD or CRT alone
Primary endpoint death from any cause or nonfatal heart failure event(whichever came first)
MADIT CRT Results
Average follow up of 2.4 years
Primary endpoint occurred in 187 of 1089 CRT-ICD patients(17.2%) and 185 of 731 patients in the ICD-only group (25.3%) (p=0.001)
Benefit did not differ significantly between ischemic and non-ischemic CM
Superiority of CRT driven by a 41% reduction in risk of HF events ( evident in subgroup of patients with QRS of 150 msec or more
CRT associated with a significant reduction in LV volumes and improvement in EF
No significant difference in between 2 groups in overall risk of death-3 % annual mortality in both groups
ICD Programming
Pacing therapy for tachy and bradyarrhythmias
Cardioversion therapy
Defibrillation therapy
Multicenter Automatic Defibrillator Implantation Trial Reduce Inappropriate Therapy – MADIT-RIT- Background
ICD is highly effective in reducing mortality in high risk cardiac patients
Despite sophisticated device detection algorithms, 8-40% of ICD therapies are inappropriate with adverse side effects
Question: can ICDs be reprogrammed to reduce inappropriate therapies?
NEJM 2012;367:2275-2283
MADIT RIT Hypothesis
Dual chamber ICD or CRT-D devices with a high rate cut-rate cut of (200 BPM), or a duration delay( initial 60 sec monitoring delay) will be associated with fewer first inappropriate therapies than standard conventional programming (2.5.sec delay@>170 BPM) without an increase in mortality
Randomized 3 arm study of patients randomized 1:1:1 to either conventional, high-rate cutoff, or duration delay programming
Primary endpoint : first episode of inappropriate therapy ( defined as shock or ATP)
Secondary endpoints: All cause mortality , Syncope
NEJM 2012;367:2275-2283
MADIT RIT-Three treatment arms Conventional therapy
Conventional therapy: 2 detection zones
First detection zone : 170-199 BPM with a 2.5 second delay and atrial discriminators turned on
Second detection zone: 200 BPM with a one second delay before delivery of anti-tachycardia pacing or shock
MADIT RIT: High rate group
Monitor only zone between 170 and 199 BPM
Therapy zone beginning at 200 BPM after a 2.5 second delay
MADIT RIT: Delayed therapy group
3 detection rates
First zone –detection rate 170-199 BPM with rhythm detection on and a 60 second delay before initiation of therapy
Second zone-detection rate of 200 BPM with rhythm detection on and a 12 second delay before therapy
Third zone-detection rate of 250 BPM or higher with a 2.5 second delay before initiation of therapy
In all zones anti-tachycardia pacing was followed by shock therapy if pacing did not terminate the detected tachyarrhythmia
NEJM 2012:367;2275-2283
MADIT RIT –Probability of first occurrence of inappropriate therapy according to treatment group
MADIT RIT Summary
Improved ICD programming to high rate (>200 BPM) or 60 second duration delay is associated with :
~75% reduction in first inappropriate therapy
~50% reduction in all-cause mortality when compared to conventional programming
Source :NEJM 2012;367:2275-2283
Remote monitoring of devices-why should we do it?
To identify clinically important issues such as device integrity issues, programming issues and asymptomatic arrhythmia detection
Advantages of remote monitoring
Earlier detection of supraventricular and ventricular arrhythmias
Earlier detection of atrial fibrillation
Earlier detection of CHF
Earlier detection of lead problems
Follow up of leads on advisory list
Device clinic
Device clinic
Device clinic team
Subcutaneous ICDs
Generator is connected to a subcutaneous electrode
ICD electrode is subcutaneously implanted from device pocket along rib margin to the sternum
Advantages of the Sub Q ICD
Absence of leads inside the heart and the preservation of central venous circulation make it a great alternative for children with congenital heart disease or patients with no venous access who were unsuitable for transvenous ICD
No risk of vascular injury or pneumothorax
Risk of systemic infections appears very low, best in high risk cases of previous device infection, hemodialysis, chronic immunosuppressive therapy, immunodeficiencies or artificial heart valves
Although pocket infections can occur(5-10%, similar to transvenous devices)infection resolves with antibiotics in the majority of cases
Explantation is rarely necessary, however explantation is much simpler and safer than transvenous lead extraction
Advantages of the Sub Q ICD
Simplified implant procedure with no need for fluoroscopy
Cosmetic advantages, despite its larger size due to the anatomic location in the lateral axilla
Well tolerated
Lack of apparent myocardial damage despite greater shock intensity (80J)
Subcutaneous ICD
Limitations of Sub Q ICD
No pacing capability except post shock pacing ( no anti-tachycardia pacing and no CRT)
Remote monitoring and atrial tachyarrhythmia monitoring not available yet
Pulse generator is larger with anticipated battery life shorter and transvenous devices
Cost is higher than transvenous device
DeMaria et al ESC Council for Cardiology Practice March 2014
Limitations of Sub Q ICD
Pre-implantation screening is mandatory. Must use a transparent plastic tool provided by the company to perform an “ad hoc” EKG skin electrode positioning to verify adequate sensing of subcutaneous signals to avoid double counting of the QRS or T wave over sensing
Up to 7.4% of possible candidates would not be suitable (hypertrophic CM, heavy weight, prolonged QRS duration and an R/T ratio <3 were independently associated with screening failure)
Risks of inappropriate shocks is similar to transvenous ICDs
Risk of under sensing true arrhythmias(VF with low amplitude waves)
Prolonged time to therapy compared to transvenous device (14-18 sec compared to 7-8 sec)
Demaria et al ESC Council for Cardiology practice March 2014
Why is EKG screening necessary for Sub Q ICDS?
Must identify the small number of patients whose Sub Q ICD signals may be unusually challenging for detection and discrimination
Surface EKG is representative of the subcutaneous signal, therefore pre-op screening process was developed to analyze patient’s EKG without the need to first implant the device
Screening process is used to analyze the QRS amplitude, QRS –T wave amplitude ratios, QRS width and morphology consistency in sinus rhythm in multiple positions
EKG screening for SubQ ICD
EKG screening for Sub Q ICD
ACCEPTABLE EKG :Entire QRS complex and trailing T wave are contained within the colored profile
UNACCEPTABLE EKG: Some portion of the QRS complex or trailing T wave extends outside of the colored profile
Brugada EKG
What’s on the horizon?
Leadless pacemakers
MRI compatible ICDs
Size comparison :match stick: loop recorder: leadless pacemaker
Summary
Top Related