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relative wall thickness

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VENTRICULAR TACHYCARDIA AND RWT

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relative wall thickness

  1. 1. 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
  2. 2. 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
  3. 3. Assessment of Remodeling patterns of the LV by echo  relative wall thickness (RWT) 
  4. 4.  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
  5. 5. 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
  6. 6. 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.
  7. 7. 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.
  8. 8.  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.
  9. 9.  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.
  10. 10. RESULTS
  11. 11. 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.
  12. 12.  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 .
  13. 13.  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
  14. 14. Patients with low RWT had a significantly higher VA and VA/death events
  15. 15. 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
  16. 16. 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
  17. 17.  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
  18. 18. 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
  19. 19.  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
  20. 20. 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
  21. 21.  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.
  22. 22. 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
  23. 23. 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
  24. 24. THANK YOU

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