CRM13: CRT Flashcards
What is heart failure?
-Complex, progressive disorder in which heart function is reduced
-Heart muscles either becomes stiff or dilated
What are the 2 types of heart failure?
HFpEF - diastolic dysfunction
HFrEF - systolic dysfunction
Symptoms of heart failure
-SOB
-Fluid retention
-Fatigue
-Cough
Causes of HF
-IHD
-Valvular disease
-Hypertension
-HCM
-DCM
What does electrical dyssynchrony look like on ECG?
LBBB
-Left and right ventricle are not pumping in synchrony
Risks of directly stimulating the LV
-Higher pressure in the left ventricle
-Clots
How is LV stimulation achieved?
-Placing a pacing lead in a branch of the coronary sinus
Difference between CRT-P and CRT-D
-CRT-D has shocking lead which goes into right ventricle (thick)
NICE guidelines for ICD and CRT implant based on NYHA class and QRS interval
Features of coronary sinus leads
-Coronary sinus leads are flexible to negotiate venous system
-Variety of shapes available for selected veins
-Majority do not have fixation as friction of vessel walls holds them in place
-IS-4 leads have 4 poles to pace from and can cover different vectors within ventricle
Which area of heart is best for achieving effective CRT?
-Posterolateral
Is basal or apical activation better in CRT?
Basal
Risk of going for coronary sinus in CRT?
-AV node can be disturbed
-Patients with BBB could get complete heart block
Which cardiac veins are most commonly gone for in CRT to target left ventricle?
-Lateral cardiac vein
-Postero-lateral cardiac vein
Why should there be a distance between left and right leads?
-To activate the largest area possible
Process of CRT implantation
-Venous access
-Place atrial and RV leads - test
-Use delivery catheter to intubate coronary sinus
-Perform venogram
-Select vein and lead shape
-Place lead
-Measure threshold and QLV
-Test of phrenic nerve stimulation
Threshold and impedance ranges in CRT
-High thresholds and impedance are acceptable, especially with limited suitable veins
-Threshold 2.0V @ 0.4ms
-Impedance 300-1300ohms
Phrenic nerve stimulation in CRT
-Phrenic nerve stimulation is tested at 5V and 10V
-Don’t want to cause phrenic nerve stimulation when pacing ventricle
-Place hand on stomach to see if twitching
-No fixation to vessel so leads may move
What is QLV interval?
-Measurement from onset of QRS of surface ECG to first positive or negative peak of LV electrogram (EGM)
-Indicates dyssynchrony and the latest area of deactivation
-QLV>95ms is good indication of resynchronisation
Issues with pacing in scar tissue
-Substrate for arrhythmias
-Delayed conduction
Features of lead testing in CRT
-Multiple vector testing
-Ideal vector should be as basal as possible
-Threshold should be low
-Higher impedances can reduce current drain on battery however need for balance
-Can have unipolar pacing vectors
-Assess ECG changes during testing (Look at V1 for LBBB and RBBB)
Complications of CRT implant
-CS lead displacement
-Asystole during CS cannulation
-CS dissection
-CS lead leading to arrhythmia
-High thresholds (battery drain)
-Phrenic nerve stimulation
-Long procedure time = increased risk of infection
Why does RV lead go in first?
-RV lead goes in first so you can pace if left lead causes arrhythmia
Benefits of conduction system pacing?
-Preservation of native activation
-Better results
-More stable lead positions
-Does not depend on venous anatomy
-Pacing along conduction system avoids cardiac remodelling
What is WISE CRT?
Wireless Stimulation Endocardially:
-Delivers ultrasonic energy to LV endocardial receiver to achieve biventricular pacing
-Potential solution to patients who failed conventional CRT
-Percutaneously delivered LV endocardial electrode delivers electrical stimulus that is synchronised to RV pacing output
CRT follow up
-6/12 month follow up
-Effective CRT Biventricular pacing percentage (>95%)
-Causes of reduced BiVp - lead malfunction, arrhythmia, ectopics
-Assess lead measurements
-Heart rate histograms - maintain BiVp at higher rates and rates not going too fast
-Patient symptoms - HF symptoms?
-Optimisation of ECG - narrowest ECG possible
What device should patient get?
CRT-D
-NYHA 3
-LBBB with prolonged QRS
Why were the sensing values lower at implant?
-Dilated ventricle
-Ischaemia (scarring)
What has happened?
-LV lead has displaced
-Not capturing
-Needs to be repositioned
-Patient still has LBBB
