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1
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2
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- CRT has sustained benefit in patients with moderate to severe heart
failure (NYHA III-IV) + severe LV dysfunction (LVEF ≤ 30%) + wide
QRS
- Improvement in symptoms
- Reduction in rehospitalization
- Increase exercise capacity
- Improved LV systolic performance
- Improved long-term survival compared to medical therapy
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3
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- MUSTIC (NEJM 2001:344;873-80)
- MIRACLE (NEJM 2002:346;1845-53)
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4
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- Severe refractory heart failure
- Severe LV dysfunction (LVEF≤30%)
- Wide QRS >120 ms (LBBB)
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5
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- 20-30% unresponsiveness rate
- Challenges:
- To identify the ideal patients for CRT
- To optimize pacing parameters in patients already treated with CRT
- Find an imaging technique to address these challenges
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6
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- Defining responders
- Acute: dp/dt (> 22%)
- Chronic: reverse remodelling
- Factors influencing responsiveness:
- QRS complex
- Interventricular dyssynchrony
- Intraventricular dyssynchrony
- Successful lead placement
- Adequate pre-excitation
- Physiologic atrial-ventricular delay
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7
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- Atrio-Ventricular - abnormal delay between atrial and ventricular
contraction
- Inter-Ventricular - abnormal delay between RV and LV contraction
- Intra-Ventricular - abnormal delay in contraction of the various LV
walls
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8
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- MV incompetence (late diastolic MR)
- Shortened ventricular filling time
- Dyssynchronization between passive to active diastole
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9
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- Optimizing atrial and ventricular activation
- Too short or too long is too bad
- Mechanical responses similar over a broad range of AV timing intervals
(110-140 ms)
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10
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- Immediate effect of optimized AV synchronization is systolic improvement
through:
- Increase in stroke volume
(increase in LVOTTVI)
- Prolongation of diastolic filling time (trans-mitral) by at least
10-20%
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11
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- The longest LV filling time w/o
premature truncation of the A wave by the mitral closure
- OR
- AV delay 100-120 ms is
sufficient
- The best choice is not determined yet and none of them was validated
with CRT
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12
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- Attach ECG electrodes to patient’s chest
- Obtain a pulsed wave Doppler view of trans-Mitral flow via a 4-chamber
view
- Ensure biventricular capture
- Make sure device is not in magnet mode
- Visualize a good ECG, E-wave and A-wave. Note the Doppler region of
interest is at the tips of the mitral valve leaflets
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13
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14
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- Program a Short Sensed AV interval, e.g. 50 ms. (SAVshort)
- Measure QAshort (Q wave to the end of the truncated A wave)
- Program a Long Sensed AV Interval, e.g. 150 ms (SAVlong)
- Measure QAlong (Q wave to the end of the A-wave)
- Calculate:
- AVopt = AVshort + [(AVlong + QAlong) - (AVshort + QAshort)]
- (AV opt = Optimal AV-Delay)
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15
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16
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17
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- Delay in LV contraction and relaxation compared to RV
- Early RV systole when LV is in end-diastole
- Peak systolic RV pressure exceeds LV, hence displaces the septum into LV
- Decreased contribution of the septum (abnormal motion) to LVEF
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18
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- Evaluation of inter-ventricular mechanical delay (IVMD): time between LV to RV pre-ejection
interval
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19
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- Abnormal ventricular activation causing premature contraction of some of
the walls
- Altered LV performance, increased wall stress, increased LVESV, delayed
relaxation
- premature contraction when the intracavitary pressure is still low
leads to low ejection (wastes work)
- Late contraction when the intracavitary is high, stress is high,
leading to paradoxical stretching of the early contracting segments
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20
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- M-mode in PSL-SX (papillary m. level): measuring IVS to PW motion delay
(SPWMD)
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21
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- Cardiac variability imaging technique: endocardial border is traced
manually in apical 4ch view. The change in fractional area against time
(”displacement map”). Comparison between IVS and LW determines
dyssynchrony.
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22
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- Use of a single image view -
dyssynchrony in other walls may be overlooked (RT3D may be a better
alternative).
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23
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- Peak systolic velocities of different regions of the myocardium can be
measured and compared.
- Timing of peak tissue velocity in relation to electrical activity (QRS)
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24
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- 12 samples volumes placed in the myocardium.
- Onset of QRS to peak systolic velocity
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25
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- Measuring time to peak between 2 samples (basal septum vs. basal lateral
wall).
- Time to peak delay ≥60 ms
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26
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- If PW TDI is used, one has to consider beat to beat variability, changes
in loading with breathing, etc.
- The proper way is to sample the various locations simultaneously.
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27
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- Yu et al. found intra-ventricular dyssynchrony in 73% with wide QRS and
in 51% with narrow QRS.
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28
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- Helpful in dyssynchrony diagnosis because of:
- Direct assessment of myocardial deformation
- Information on the timing of onset and peak myocardial contraction
- Better than TDI in differentiating active systolic contraction from
passive displacement (scar tissue tethered by adjacent viable tissue)
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29
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30
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- Similar information can be obtained more easily with the use of a
color-coded display of myocardial displacement (Tissue Tracking)
- Global and regional systolic performance can be visualized , and quick
assessment of regional strain distribution by the width of LV color
bands.
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31
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- Correct timing of LV mechanical event is crucial (LV
ejection/filling/IVC/IVR)
- These events can be synchronized to valves opening and closure (by
Doppler or M-mode)
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32
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33
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- CRT improves LVEF (28±10% => 40±15% but others showed only
+∆4.6%)
- MR reduction (ERO decreases immediately)
- Reverse remodeling (-∆30% in LVESV and LVEDV after 6 months). The
effect on sphericity index (LV geometry) and LVM is less established.
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34
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- Using the pw TDI (5 segments sampling) reverse remodeling, improved FC
and elongation of 6-minute walk distance were induced by CRT and
inter-ventricular re-synchronization.
- The pre-CRT intra-ventricular dis-synchronization was correlated to
post-CRT improvement
- In the contrast-enhanced echo approach CRT immediately improved
intra-ventricular synchronization by 40%
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35
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- With the 12 samples TDI method (Yu et al.), the only predictor of
reverse remodeling after CRT was the extent of dis-synchrony
- The dyssynchrony index can separate the pts into 2 groups: only those
with pre-CRT index >33 ms had reverse remodeling after CRT
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36
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- TDI studies showed the latest mechanical activity in the LW (35%), AW
(26%), PW (23%), IW and IVS (16%).
- The optimal re-synchronization and clinical response were obtained when
the wall with the latest activity was paced.
-
Ansalone et al. JACC 2002;39:489-99
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37
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- Which is the best mode?
- What should be done in ischemic cases with multiple scars (each showing
delayed activation)?
- Is pacing a scar (nonviable) tissue useful?
- Sequential ventricular pacing can enhance the benefit from CRT using TT.
Increases LVEF from 30±5% to 34±6%.
- Sogard et al. Circulation
2002;106:2078-84
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Notes
