Author + information
- Hoong Sern Lim, MD∗ ()
- ↵∗University Hospital Birmingham, NHS Foundation Trust, Edgbaston, Birmingham B15 2TH, United Kingdom
It is axiomatic that the presence of a substrate that is amenable to a specific treatment, coupled with effective delivery of that treatment, is likely to produce the most favorable clinical outcomes. In patients with heart failure, left bundle branch block (LBBB) and the associated abnormal electro-mechanical activation represents the substrate for biventricular pacing (BivP). This LBBB substrate has been defined by (“strict”) electrocardiographic or echocardiographic criteria.
Risum et al. (1) showed that echocardiographic LBBB is independently associated with long-term survival after BivP. The implicit assumptions are that: 1) the echocardiographic criteria for LBBB is closely aligned with the substrate that is amenable to correction by BivP; 2) BivP was effective in reversing the abnormal electro-mechanical activation; and 3) correction of the echocardiographic LBBB-related electro-mechanical activation resulted in the better outcomes in patients with echocardiographic LBBB.
We have recently reported that baseline LBBB (by the strict electrocardiographic criteria) and the reversal of LBBB, as evidenced by reversal of electrocardiographic activation pattern, was associated with the most favorable clinical outcomes (2). Clinical outcomes in patients with LBBB without correction by BivP were comparable to patients with non-LBBB, which supports electrocardiographic LBBB as a substrate for BivP.
In this regard, it is not clear if the clinical outcomes observed by Risum et al. (1) are due to correction of the echocardiographic LBBB-related electro-mechanical contraction abnormality by BivP, or even worsening of the contraction pattern in patients without echocardiographic LBBB. The clinical outcomes in patients with/without echocardiographic LBBB and with/without correction by BivP should be examined to demonstrate the relevance of echocardiographic LBBB as a (or perhaps the) substrate for BivP.
Please note: Dr. Lim has reported that he has no relationships relevant to the contents of this paper to disclose.
- 2015 American College of Cardiology Foundation
- Risum N.,
- Tayal B.,
- Hansen T.F.,
- et al.
- Wan D.,
- Tan Y.T.,
- Al-Lawati K.,
- Lim H.S.