Author + information
- Dan Wichterle, MD, PhD⁎ ( and )
- Vlastimil Vancura, MD, PhD
- ↵⁎Department of Cardiology, Institute for Clinical and Experimental Medicine, Videnska 9, Prague 140 21, Czech Republic
We read with interest the paper by Spragg et al. (1) regarding optimal left ventricular (LV) endocardial pacing sites for cardiac resynchronization therapy in patients with ischemic cardiomyopathy.
However, we would like to challenge the authors' conclusion that “LV endocardial pacing is capable of dramatic improvements in LV systolic function when the optimal site is stimulated” and to offer the authors an alternative explanation for their findings.
Although experimental data were not fully disclosed, it appeared that standard epicardial coronary sinus pacing was associated with an ∼20% increase in LV dP/dtmax compared with right ventricular apex (RVA) pacing. The best endocardial pacing site further improved LV dP/dtmax by ∼13%, yielding an overall hemodynamic benefit (optimal endocardial site vs. RVA pacing) of ∼36%. The fundamental problem is that LV sweet spot was sought among a considerable number (∼51) of LV endocardial sites and the correction for inherited statistical bias, due to multiple measurements design together with biological variability and non-zero analytical error of dP/dtmax assessment, was not performed. It can easily be demonstrated by mathematical modeling that a relatively small measurement error projects into a rather wide range of extreme results. For example, under the assumption that all endocardial LV pacing sites have an invariable hemodynamic impact (dP/dtmax of 120% of RVA pacing, i.e., comparable to epicardial CS pacing) and that the coefficient of variation for dP/dtmax measurements is 6%, which is a quite realistic estimate, the 1,000-run simulation experiment in 11 patients, each with 51 pacing sites analyzed, offers a mean dP/dtmax of 136% at “best” sites versus RVA pacing. Such a magnitude of improvement is identical to that observed and declared as a biological pacing site–specific effect in the mentioned study.
We thus wonder whether Spragg et al. (1) would agree that some of their findings might be significantly biased because apparent hemodynamic improvement during LV endocardial pacing may predominantly originate from the statistical analysis used in their paper. Interestingly, another recent report on optimizing hemodynamics by LV endocardial pacing in patients with nonischemic dilated cardiomyopathy (2) used almost identical analytical methods that could similarly influence their interpretation favoring endocardial over the standard coronary sinus pacing.
An endocardial approach to cardiac resynchronization is certainly a promising concept, providing more flexibility in pacing site selection compared with standard epicardial biventricular pacing, but adequate experimental design and correct data analysis should be prerequisites for valid conclusions.
- American College of Cardiology Foundation
- Spragg D.D.,
- Dong J.,
- Fetics B.J.,
- et al.
- Derval N.,
- Steendijk P.,
- Gula L.J.,
- et al.