Effects of Cardiac Contractility Modulation Therapy on Right Ventricular Function: An Echocardiographic Study

Round 1

Reviewer 1 Report

This small observational study reports on the effect of cardiac contractility modulation (CCM) for specific echo parameters indicative of right ventricular function.  The authors have chosen TAPSE and S' which are commonly used for evaluating RV function, RV freewall strain less so. 21 patients entered the study, however 2 died during follow-up allowing for data acquisition in 90% of the cohort.

Can we based on the present analysis comfortably conclude that RV function is independently improved by CCM? Presently I would have to say "no" since there is no mention of change in LV function. In other words, does the RV function change regardless of what happens to the left ventricular function? This paper would be greatly strengthened understanding the context of RV function with what happened to the left ventricular function. This might have implications as we apply the technology to patients with EF 40-60% in upcoming studies.

Did any patients undergo bypass after implant? This could significantly effect the TAPSE and S' from loss of the pericardium through underestimation of their values. If all bypass was pre-procedure, then each bypass patient would serve as their own control (i.e the delta would not be affected). This should be commented on. 

Author Response

Thank you.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments to the Author

The Authors present the study entitled “Effects of Cardiac Contractility Modulation Therapy on Right Ventricular Function. An Echocardiographic Study”. Cardiac contractility modulation (CCM) is a device-based therapy for patients with advanced heart failure (HF). It is intensively studied in left ventricular failure; however, little evidence is available on the effect of CCM on right ventricle (RV) performance. Therefore, the presented study could be of great interest. The Reviewer appreciates the Authors’ effort; however, essential changes are to be introduced before my final decision. 

  Major comments: 1.     A schematic figure presenting the described CCM localization should be added for helping the readers to understand the technique. 2.     Nevertheless, the study concentrated on RV function improvement, the brief information about LVEF and LV sizes after 6 months of therapy (Table 2)  is obligatory.

3.     The information in the discussion does not match the performed calculations presented in the results part (‘The increase of all three indices of RV function occurred in both normal and reduced RV function patients.” ). The Authors did not perform such analyses and that sentence does not present the results of the study.

4.     There is no information about the implanted electrical devices, while the Authors mentioned that as the explanation in the discussion prat regarding TI after 6 months of the CCM treatment.

5.     The comparison between the medications at the first and second examination should be added.

Minor comments:

1.     In the Abstract methods the Author wrote: “By Doppler-echocardiography, tri- cuspid annular systolic excursion (TAPSE)…” – TAPSE is M-Mode technique result, therefore, that should be rewritten correctly.

2.     In the Abstract results the Authors wrote “After six months, patients who underwent CCM” – was the group without CCM? It is not clear in the abstract, please correct it.

3.     The Abstract result should include some numbers, not only the text.

4.     The sentence in the Abstract conclusions “At six months, CCM increases RV reverse remodelling and performance” is not clear – please rewrite it.

5.     The writing style should be corrected to avoid some repeats, merging words, spelling and grammar mistakes in the text. The Authors should restrict the number of small paragraphs, connecting information to the bigger ones.

6.     The followed text should be transferred to the description of the statistics “Receiver Operating Feature (ROC) curve analysis was performed to select the cut-off values of echocardiographic measurements. Reproducibility of measurements was determined in all patients. Inter-observer and intra-observer variability were examined using Pearson's two-tailed bivariate correlations and Bland-Altman analysis. Correlation co-efficient, 95% confidence limits, and percentage errors were reported. “

7.     M-mod should be changed on M-mode.

8.     After the paragraph in the methodology, the appropriate citations should be added; ‘Pulmonary artery systolic pressures (PASP) were estimated from the maximum velocity of the tricuspid regurgitant jet using the modified Bernoulli equation and then adding to this value the right atrial pressures calculated based on both the size of the inferior vena cava and the change in caliber of this vessel with respiration, according to international recommendations”.  

9.     The lack of 3D RV assessment is a certain limitation of the study, which is acceptable but should be noted in the study.

 

Author Response

Thank you.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Change in LV function has been added to the results table, however there has been no added commentary discussing the implications of change in LV function on RV function. Do the authors think that the improvement in RV functional indices is independent of change in LV status? This needs to be included in the discussion. 

Author Response

Thank you

Author Response File: Author Response.docx

Reviewer 2 Report

The Authors precisely corrected all comments and I do not have any further demands.

Author Response

Thank you