relative wall thickness

RELATIVE WALL THICKNESS AND
THE RISK FOR VENTRICULAR
TACHYARRHYTHMIAS IN PATIENTS
WITH LV DYSFUNCTION
 J O U R N A L O F T H E A M E R I C A N C O L L E G E O F C A R D I O L O G Y;2016

INTRODUCTION
 Reduced LVEF and the presence of myocardial
scar are associated with higher risk of ventricular
arrhythmia (VA) and SCD
 ICD-reduces mortality associated with VA
 CRT-D compared with ICD -reduces VA incidence by
reverse remodelling
 We assessed relationship between remodelling and
the risk for VA

Assessment of Remodeling
patterns of the LV by echo
 relative wall thickness (RWT)


 concentric remodeling(high RWT) is associated
with increased morbidity and mortality in
hypertensive patients with HCM-Hiwada K et al
 Relation between the magnitude of eccentric
hypertrophy(low RWT) and the risk of VA in DCM –
scarce data

MADIT –CRT TRIAL (Multicenter Automatic Deﬁbrillator
Implantation Trial With Cardiac Resynchronization
Therapy)
 patients who had ischemic cardiomyopathy (NYHA FC I or II)
or nonischemic cardiomyopathy (NYHA FC II), LVEF ≤30%,
normal sinus rhythm, and QRS duration ≥130 ms, were
randomized to receive CRT-D or ICD therapy in a 3:2 ratio.
 superiority of CRT -41% reduction in the risk of heart-failure
events, more so in patients with a QRS duration of 150 msec or
more.
 CRT -significant reduction in LV volumes and improvement in
EF
 no significant difference between the two groups in the
overall risk of death, with a 3% annual mortality rate in each
treatment group

AIMS
 1) the predictive value of RWT for the risk of VA
compared with other commonly used echo variables
 2) the relationship between LV morphology and the
risk of VA by measuring RWT; and
 3) the remodelling effect of CRT-D on RWT.

METHODS
 1,260 patients enrolled in the MADIT-CRT trial with
LBBB at baseline electrocardiogram .
 programmed to monitor and deliver therapy, ATP,
and/or shock therapy
 interrogated 1 month after enrolment ;thereafter
every 3 months
 VA episode was defined when device-rendered
therapy ( ATP or shock) was appropriately delivered.

 VT= episode with ventricular rates between 180 and
250 beats/min
 VF- episode with ventricular rates ≥250 beats/min.
 Fast VT = episode with ventricular rates ≥200
beats/min or VF.

 Echo - baseline, which was before device implantation,
and at 1 year
 Septal wall thickness (SWT) and posterior wall thickness
(PWT) were assessed in PLAX view
 RWT = 2 times PWT divided by the LV diastolic diameter
 second method =sum of SWT and PWT divided by LV
diastolic diameter
 Patients were dichotomized between the lowest RWT
tertile (<0.24) and the upper 2 tertiles (≥0.24)
 primary endpoint - combined endpoint of VT or VF.
 Secondary endpoints -separate endpoints of VT, VF, fast
VT , and the combined endpoint of VT,VF, and death.

RELATIONSHIP BETWEEN RWT AND
VA.
 compared the risk associated with several echo
parameters (including LVEDV, LVESV, LA volume,
LVEF, LV mass, and LV mass/LVEDV ratio)
 RWT –best echocardiographic variable
 Patients with low RWT (<0.24) had 83% (p < 0.001)
increased risk for VA and 68% (p < 0.001) increase in
VA risk or death (VA/death) compared with patients
with higher RWT values.

 RWT was a significant and superior predictor even
when combined with other echo variables and added
significantly to the predictive capacity of all of the
models .

 The 2 components of RWT, LVEDD and LV PWT,
were significant independent predictors of VT/VF
and VT/VF/death.
 LVEDD was a better predictor versus LVPWT
 wider LVEDD -increased hazard; lower LVPWT -
harmful
 RWT had a better fit compared with its 2 components
and with the LV mass/LVEDV ratio

Patients with low RWT had a significantly higher VA and VA/death
events

multivariable analysis
 lower RWT as either categorical or continuous (i.e., every
0.01-U decrease in RWT) variable was significantly related
to higher event rates
 significant, even after further adjustments to baseline
differences (BNP, BMI, and smoking),and in all pre-
specified subgroups
 consistent when an alternative formula was used for
measuring RWT (SWT +PWT divided by LVEDD)
 each 0.01-U decrease in RWT
1. 11% (HR: 0.89;p < 0.001) increase in the risk of VA
2. 9% (HR: 0.91;p < 0.001) increase in the risk of VA
/death

THE EFFECT OF CRT-D ON RWT
 greater increase in RWT compared with ICD therapy
at 12 months (4.6 +/- 6.8% vs. 1.5 +/-2.7%; p < 0.001).
 Kaplan-Meier survival analysis -cumulative probability
of a first occurrence of VT/VF 3 years after assessment
of echo response was significantly lower in those with
increased RWT compared with those with lower
changes in RWT at 12 months.
 every 10% increase of RWT at 12months -34% and
36% reductions in the rates of subsequent VA events
and subsequent VA/death

 Baseline RWT was a significant predictor of VT/VF in
both the ischemic and nonischemic subgroups
 HR for the ischemic subgroup was 1.11 and for the
nonischemic subgroup was 1.12
 RWT increase at 12 months was associated with risk
reduction for VT/VF in both subgroups

DISCUSSION
 RWT was the best echo predictor for VA events
compared with commonly used echo measurements
 RWT was inversely related to the risk of VA in
patients with eccentric hypertrophy
 increased RWT after 1 year of CRT-D treatment was
related to lower risk for VA in patients with eccentric
hypertrophy

 In the present study, almost all of the patients had
eccentric hypertrophy (RWT <0.32), and only a few
had normal geometry (0.32 < RWT <0.42), as one
would expect in the case of severe systolic HF leading
to dilated cardiomyopathy

mechanisms
 remodeling process of the diseased heart is characterized
by the replacement of necrotized myocytes with
fibroblasts, which in turn increase collagen formation
 This process induces fibrosis and scar formation that can
potentially cause even healthy myocytes to undergo
apoptosis; this paradigm is known to serve as a substrate
for reentry circuits, EADs, and the formation of VA,
especially in patients with enlarged ventricles with slowed
impulse propagation velocities over fibrotic tissue
 Fibrosis enhances the ability of oxidative stress to induce
spontaneous VF

 eccentric hypertrophy, the magnitude of RWT can
mirror the extent of LV fibrosis and scarring on one
hand and the extent of the remodeling process on
the other hand
 both of these measures (wall thickness as a measure
of wall fibrosis and diastolic diameter as a
measure of remodeling) were independently
associated with the risk of VA.
 RWT had a higher predictive capacity compared with
its own components.

STUDY LIMITATIONS
 Retrospective, nonrandomized post-hoc study
 Even after adjustment for many confounders, this was
not a prospective trial and so possible unmeasured
confounders may have biased the results
 Only included patients with LBBB morphology
because CRT-D benefit was shown to be limited to this
subgroup

CONCLUSIONS
 Defining the baseline degree of eccentric hypertrophy
using RWT measurement can be useful for prediction
of VA in patients with impaired LVEF and mild HF
 among patients implanted with a CRTD device, the
magnitude of RWT increase attributed to CRT-D can
predict VA risk as well

relative wall thickness

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