Implantable Loop Recorders (ILR)

Implantable Loop Recorder

AKA implantable cardiac monitors (ICMs)

Implanted under the skin to monitor heart rhythm

Capture, record, and classify rhythm

Send alerts using RM

Did the device get it right?

Modern ILRs

1-2 inches long

Implanted in left parasternal region

Up to 5 years

Continuously loop over data, saving specific episodes

Patients with infrequent symptoms

Unable to document using another method

Holter Monitor

electrodes on chest (24-72 hours)

Event Recorder

only record events or when patient presses button (week to a month)

External Loop Recorder

patch with continuous monitoring like ILR (week to a month)

ILR Indications

Document arrhythmia correlated to symptoms

Syncope: bradycardia, pauses, VT, VF

Palpitations: bradyarrhythmia, tachyarrhythmia

Monitor VT, assess medications

Post AF ablation monitoring

Cryptogenic stroke

ILR Implant

Sometimes called injectable loop recorders

Left parasternal region for best signal

A: Diagonal between 4th and 5th ribs (most common)

B: Parallel to sternum

C: Horizontal

ILR Implant Steps

Numbed with local anesthetic

Initial incision

Delivery-system inserted

Delivery-system rotated 180°

Device advanced using plunger

Delivery system removed
Incision sealed

Clinical Specialist Role

Coach physician on implant procedure

Check device sensing

Reposition if signal is bad

Program device to match indications

Input patient info

Educate patient

Set up RM

ILR Sensing

Electrodes under skin: small signals

Typically < 1 mV, recommended R waves > 0.2 mV

Auto-adjusting sensitivity

Avoid P waves and T waves

Lowest programmable value for max sensitivity: 0.025 mV

ILR Programming

ILR Programmer Screen

Fewer parameters

Sensing/detecting only

Subcutaneous ECG

Home page:

Battery capacity

Parameters

AF burden

Episodes

Sensing test

Analyze stored episodes

Adjust alerts

AF Detection

No atrial lead: based on R-R irregularity

Compare current interval to previous intervals

Sinus rhythm: regular

AF: irregularly irregular

AT: regular or regularly irregular

Fooled by PACs, PVCs, 2nd degree HB

Difficult to assess with small atrial signals

Once AF detected and treated, turn alerts off

CIED Indication

Sinus bradycardia: must have documented symptoms

Ignore bradycardia while patient asleep

Some indications do not require symptoms:

Asystole > 3 seconds

Escape rhythm < 40 bpm

VT: may indicate for ICD