Cardiac Resynchronization Therapy

1. Cardiac
Resynchronizati
on Therapy
DR SEEBAT MASRUR
D-CARD RESIDENT
CARDIOLOGY DEPARTMENT
SZMCH

2. CRT
CRT is treatment for heart
failure, appropriate in the
setting of sufficiently
depressed LVEF and
electrically dyssynchronous
ventricular function
It is the last device option to
treat heart failure before
LVAD, heart transplant!

3. What is Dyssynchrony?
▪ Dyssynchrony refers to impaired mechanical coordination due to impaired
electrical activation of heart muscle.
▪ Electrical dyssynchrony identified by prolonged QRS duration on ECG.
▪ QRS prolongation typically due to conduction system disease, such as
bundle branch block.
▪ Chronic pacing-induced conduction delays due to high RV(single chamber)
pacing burden.

4. Types of Dyssynchrony
▪ AV Dyssynchrony
▪ Interventricular Dyssynchrony
▪ Intraventricular Dyssynchrony
Other Types
▪ Mechanical Dyssynchrony
▪ Electrical Dyssynchrony

6. Cardiac Resynchronization Therapy
▪ All patient with heart failure need optimal pharmacological therapy and
lifestyle modifications.
▪ But in a small subset, there is a definite role for devices.
▪ Intraventricular dyssynchrony in the presence of severe left ventricular
dysfunction is an important indication for cardiac resynchronization therapy.
▪ Delay between the contractions of the septum and the lateral left
ventricular wall causes reduced left ventricular stroke volume.

7. Cardiac Resynchronization Therapy
▪ The important surrogate of ventricular dyssnchrony is an increased QRS
duration.
▪ In CRT, septum and lateral left ventricular wall contracts simultaneously
producing improvement in the left ventricular stroke volume.
▪ CRT improves the symptomatic status and survival of the heart failure
patients with left ventricular dyssynchrony.
▪ But still there is a 30% non-responder rate of patients who do not
respond to CRT.

8. Cardiac Resynchronization Therapy
▪ QRS duration of 150 ms or more with LBBB pattern in a person with
refractory heart failure will be a strong indication for cardiac
resynchronization therapy.
▪ It is often associated with mechanical dyssynchrony and wasted systolic
effort of the left ventricle.
▪ CRT produces a narrowing of the QRS complexes as the right ventricle and
posterolateral left ventricle are paced in synchrony, to produce a better left
ventricular output.
▪ CRT system may include ICD protection(CRT-D), or provide only pacing
therapy(CRT-P)

10. CRT System-Three leads

11. CRT implant Objectives- lead Placement

12. CRT advantages with Quadripolar LV lead
REF-https://www.ahajournals.org/doi/10.1161/JAHA.117.007026
▪ Better CRT
▪ Lead Stability
▪ Phrenic Nerve capture
▪ Lowest threshold
CRT using QUAD, programmed to
biventricular pacing with
single‐site LV pacing, is
associated with a lower total
mortality, cardiac mortality,
and HF hospitalization.

13. Patient selection criteria

14. CRT guidelines for
pt in AF

15. Recommendation for
upgrade from right
ventricular
pacing to cardiac
resynchronization
therapy

16. Selection criteria
for CRT

17. Who Qualifies for
CRT

19. Who responds to CRT?
Overall response rate 70%
1. Significant dyssynchrony
2. Minimal Lateral LV scar
3. Adequate CS anatomy

20. Sliding Scale of Efficacy

21. Predictors of CRT Response
▪ LBBB is best marker
▪ QRS duration is critical
▪ NICM>ICM
▪ Women>Men

22. CRT in heart failure with narrow QRS complex
▪ In patient with systolic HF and a
QRS duration of less than 130
msec, CRT does not reduce the
rate of death or hospitalization
for heart failure and may
increase mortality.

23. Echocardiographic parameters
▪ M-mode: Septal posterior wall motion delay at papillary muscle level in
parasternal short axis view , 130 ms has a sensitivity of 24% specificity of
66%.
▪ Interventricular mechanical delay: Difference between LV and RV pre-ejection
period.
▪ Beginning of QRS chamber view and beginning of QRS to beginning of RV
ejection in short axis view; difference > 40 ms is significant.
▪ Tissue Doppler Imaging: Septal to lateral wall delay in time to peak velocity >
60ms is suggestive of dyssynchrony.

24. PROSPECT TRIAL
▪ Conclusion
▪ Echo guided CRT patient
selection has no prospect

25. Procedure

27. Reverse Remodeling with CRT reduces life
threatening Ventricular arrhythmias
▪ There have been some reports of whether the altered sequence of
ventricular depolarization with CRT can be arrhythmogenic.

28. CRT reduces life threatening ventricular
arrhythmias
▪ They grouped the subjects into three- those
with 25% or more reduction in LV end
systolic volume at one year compared with
baseline, those with less than 25%
reductions and those who received only ICD
and not CRT-D.
▪ The first group was the CRT responders and
the second one CRT non-responders.
▪ The highest rates of ventricular
tachyarrhythmias was highest in the
nonresponder(28%) & lowest in the
responders(12%)

29. CRT reduces life threatening ventricular
arrhythmias
The ICD only group had an
intermediate value of 21%
This was for the cumulation
probability of first ventricular
tachyarrhythmias at two
years after the initial
assessment

30. CRT reduces life threatening ventricular
arrhythmias
▪ Multivariate analysis showed a 55% risk reduction between CRT
responders and ICD only patients, while the difference was not
significant between non responders and ICD only patients.
▪ It concluded that reverse remodeling with CRT is associated with
significant ventricular arrhythmias

31. ECG in CRT
Leads I, II & III are most
useful in deciding whether it
is RV, LV or biventricular
pacing.
Since the pattern varies
from individual to individual,
it is good to preserve the
tracings of all modes of
pacing for future
comparison.

32. CXR in CRT

33. Complication
▪ Lead related reintervention-
dislodgement, malposition, subclavian
crush syndrome
▪ CIED-related infections, <12 months-
Superficial infection, pocket infections,
systemic infections
▪ CIED-related infections, >12 months-
Pocket infections, systemic infections
▪ Pneumothorax
▪ Hemothorax
▪ Brachial plexus injury
▪ Cardiac perforation
▪ Coronary sinus dissection/perforation
▪ Diaphragmatic stimulation
▪ Hematoma, Seroma
▪ Tricuspid regurgitation
▪ Pacemaker syndrome

34. Non responders to CRT
About 30% of patients do not respond to CRT.
The reasons could be any one of the following;
▪ Not every patient with wide QRS has dyssynchrony and vice versa.
▪ Leads may be too close to each other to produce synchronous contraction of
septum and lateral wall.
▪ Scarred region of the ventricular can cause poor capture and synchronization.

35. Non responders to CRT
▪ Consistent ventricular capture by spontaneous impulses can also prevent
resynchronization. This is more likely to occur in atrial fibrillation with fast
ventricular rate.Attempts at AV nodal ablation to counter this problem have
been tried.In sinus rhythm, this problem can be reduced by programming a AV
delay.
▪ Dislodgement of LV lead can also be a cause of poor synchronization.

36. Monitoring Improvement
▪ ECG-Electrical dyssynchrony improvement
▪ ECHO-Mechanical dyssynchrony improvement
▪ NYHA Class
▪ 6 mins walk test
▪ Quality of life scores

37. CRT benefits
Identifying responders
▪ Symptoms
-Improved exercise tolerance
-Reduced SOB
-Improved NYHA status
▪ Reversed LV remodeling
-Improved LVEF, Reduced size, reduced MR
▪ Prognosis
-Reduced CHF hospitalization
Reduced mortality

38. Take Home Message
▪ CRT has emerged as an effective therapy in patients with LVD refractory to CHF
medications and a wide QRS duration.
▪ Major clinical trials have proven significant morbidity and mortality benefits from
CRT.
▪ The issue of nonresponse to CRT continues to be a major problem.
▪ While the response to CRT in patients with a native LBBB or RV-paced rhythm is
well documented, the response in patients with RBBB or a nonspecific IVCD
continues to be debated.

39. Thank you

40. Selection criteria for CRT
▪ Severe heart failure NYHA class III or IV.
▪ Depressed left ventricular ejection fraction <35%
▪ QRS duration 150 ms or more.
▪ Most widely used marker of dyssynchrony is surface ECG. But it is
not absolute marker as it may not have complete correction with
mechanical dyssynchrony.
▪ LBBB is associated with dyssynchony of lateral wall compared to
the septum.
▪ Should be in sinus rhythm for better synchronization and should be
on optimal medical therapy.

41. Selection criteria for CRT
▪ Those with recent myocardial infarction or have undergone
coronary revascularization within 3 months as well as those
scheduled for coronary revascularization are excluded.
▪ This is in view of the potential for improvement in the left
ventricular function in the short term.

43. Take Home Message
▪ CRT address systolic heart failure
▪ Rectify mechanical dyssynchrony
▪ Improve symptoms and reduce mortality

44. CRT implantation- Basic cannulation of coronary
sinus
▪ Start ventricular to tricuspid valve and withdraw applying counter
clockwise torque to stay septally to cannulate the coronary sinus
ostium.
▪ LAO is lined upon the interventricular septum.
▪ The orthogonal view is RAO.
▪ A prominent Thebesian valve with ab associated pouch causes the
lead to fall into it and causes difficult in cannulating the coronary
sinus.
▪ Injecting a whiff of dye will help delineate the position of the
sheath in the pouch, which causes transient dye stasis.

45. CRT implantation-Inability to advance in coronary
sinus
▪ In ability to advance in CS could be due to stenosis, valves, subs
election, dissection and tortuosity.
▪ Vieussen`s valve is an embryonic remnant, seen at the origin of
the posterolateral ventricular vein.
▪ If there is a prominent valve in the posterolateral vein, we can
cannulate the middle cardiac vein and go into a lateral branch of
this vein

46. CRT implantation-Inability to advance in coronary
sinus
▪ CS stenosis can be ballon dilated, but branch vein stenosis is
better left alone.
▪ Search for other veins which could be used. This will also reduce
the dye load in attempted dilation.
▪ Dissections can occur due to dye injections and by sheath
advancement.
▪ In most of the dissection is distal, try using the lateral branch of
the middle cardiac vein.
▪ Pushing a catheter which is sub selected without recognizing it is
one of the reasons for dissection.

47. CRT implantation-Inability to advance in coronary
sinus
▪ If it is atrial vein subselection, withdraw it
▪ If it is ventricular vein subselection, cannulation is over!
▪ So try to recognize it with appropriate views

48. CRT implantation-Inability to get lateral veins
▪ If it is atrial vein subselection, withdraw it.
▪ If it is ventricular vein subselection, cannulation is over.
▪ So try to recognize it with appropriate views

49. Need for ICD lead in Left ventricle
▪ When there is a mechanical tricuspid valve which you don’t want
to cross, an ICD lead may have to be placed in a coronary vein.