"Preserved function in the lateral wall seemed to be crucial to achieve a normal or near-to-normal heart function after CRT," Dr. Helge Skulstad of Oslo University Hospital told Reuters Health by email. "This could be achieved even if the function in the central part of the heart, the interventricular septum, was low."
"Thus," he said, "clinicians should focus on the lateral wall - not only the global left heart - when deciding if a patient with LBBB should receive CRT."
"Our findings have the potential to change current guidelines," he added. "We have initiated further clinical studies to confirm and extend the findings."
As reported in JACC: Cardiovascular Interventions, the cross-sectional study included 76 patients (average age 66) with LBBB and without ischemic heart disease from two previous studies and 11 controls without LBBB from another study.
The team measured strain using speckle-tracking echocardiography, and regional work using pressure-strain analysis. They stratified LBBB patients according to LV ejection fraction (LVEF): 50% or more, EFpreserved; 36% to 49%, EFmid; and 35% or less, EFlow.
Sixty-four patients underwent CRT and were re-examined six months later.
Septal work was successively reduced from controls - through EFpreserved, EFmid, and Eflow - and showed a strong correlation to LVEF.
By contrast, LV lateral wall work was increased in EFpreserved and EFmid versus controls, and did not significantly correlate with LVEF in these groups.
However, in EFlow, LV lateral wall work was substantially reduced.
There was a moderate overall correlation between LV lateral wall work and LVEF. In CRT recipients, LVEF was normalized to 50% or greater in 54% of patients with preserved LV lateral wall work, but in only 13% of patients with reduced LV lateral wall work.
The authors conclude, "In early stages, LBBB-induced heart failure is associated with impaired septal function but preserved lateral wall function. The advent of LV lateral wall dysfunction may be an optimal time-point for CRT."
Dr. Paul Hauptman, Professor and Dean, Division of Cardiology at the University of Tennessee Graduate School of Medicine in Knoxville, commented on the study in an email to Reuters Health. "Predicting progression of cardiomyopathy and optimal timing of CRT implantation in patients with LBBB remains clinically challenging," he said.
"In the current meticulously performed three-center analysis, the authors purport to show progression from septal to lateral wall dysfunction in the non-ischemic LBBB cohort," he noted. "But confirmatory data are needed, given the study's cross-sectional design."
"Nevertheless, the fact that lateral wall work appears to be increased in patients with relatively preserved LVEF and decreased in patients with low LVEFs suggests a progressive sequence of events," he added. "Whether the implantation of CRT devices can be most effective when timed at the first indication of lateral wall dysfunction remains to be seen."
SOURCE: https://bit.ly/3h2mQWE JACC: Cardiovascular Interventions, online June 16, 2021.
By Marilynn Larkin
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