## 3 Results
### Changes in RVfvLS during Pacing  
Significant overall improvements in RVfvLS were observed in response to higher-paced HRs (Figure 1). Only seven patients (16%) experienced a worsening of RVfvLS that were greater or equal to 10%. Twenty-five participants (56%) exhibited improvements and 13 (29%) maintained stable values at higher HRs (Supplementary Figure S1). We identified a high concordance (78%) between measures of RV strain and HR (Figure S1). The results shown in Figure 1 document HR-related changes in RVfvLS in participants in whom this parameter remained unchanged. Figure 3 reports, as well, three different cases of RVfvLS HR-related changes. The percentages of participants that exhibited a worsening of RVfvLS were similar in patients with ICD and CRT (19% and 18%, respectively). By contrast, none of the patients with PM exhibited deteriorations in RVfvLS. Interestingly, participants with PM were more likely to experience improvements in RVfvLS compared to participants with ICD and CRT (86% versus 57% and 41%, respectively). As shown in Table 4, participants exhibiting deteriorations in RVfvLS were those who presented initially with depressed LV and RV functions, as determined by baseline measurements of LVGLS, RVGLS, and RVfvLS. These participants also presented with higher PASPs and diminished levels of RV arterial coupling. \begin{table}
\begin{tabular}{l c c c} \hline \hline  & \multicolumn{3}{c}{**Changes in LVGLS in Response to**} \\  & \multicolumn{3}{c}{**Increasing HR**} \\ \hline  & \multicolumn{3}{c}{**Worsened**} \\  & **(n = 34)** & **(n = 11)** & **\(p\)** \\ \hline Age (years) & \(67\pm 14\) & \(65\pm 13\) & 0.714 \\ BMI (kg/m\({}^{2}\)) & \(24\pm 5\) & \(25\pm 4\) & 0.559 \\ SAP (mm Hg) & \(114\pm 21\) & \(123\pm 22\) & 0.212 \\ NYHA & \(2.4\pm 0.6\) & \(2.0\pm 0.8\) & 0.141 \\ Baseline HR (bpm) & \(66\pm 7\) & \(68\pm 5\) & 0.392 \\ ICD/CRTD/PM (\%) & \(53/35/12\) & \(27/45/43\) & 0.261 \\ LVEDV (mL) & \(178\pm 83\) & \(170\pm 104\) & 0.794 \\ LVEF (\%) & \(33\pm 11\) & \(44\pm 16\) & 0.019 \\ LVEF \(\leq 40\)\% (\%) & \(81\) & \(19\) & 0.237 \\ LVGLS (\%) & \(-9.5\pm 3.4\) & \(-12.0\pm 5.15\) & 0.049 \\ LV Tei index & \(0.69\pm 0.21\) & \(0.47\pm 0.19\) & 0.003 \\ CI (L/min/m\({}^{2}\)) & \(2.1\pm 0.5\) & \(2.5\pm 0.6\) & 0.057 \\ LVMI (g/m\({}^{2}\)) & \(153\pm 39\) & \(164\pm 44\) & 0.457 \\ LAVi (mL) & \(40\pm 20\) & \(38\pm 17\) & 0.712 \\ E/e’ ratio & \(132\pm 6.1\) & \(12.9\pm 5.8\) & 0.884 \\ MR (a.u.) & \(1.9\pm 0.9\) & \(2.2\pm 0.9\) & 0.440 \\ TAPSE (mm) & \(18.6\pm 3.5\) & \(20.2\pm 3.4\) & 0.189 \\ PASP (mmHg) & \(34\pm 11\) & \(32\pm 10\) & 0.680 \\ TR (a.u.) & \(1.7\pm 1.0\) & \(2.2\pm 1.7\) & 0.193 \\ RVGLS (\%) & \(-15.2\pm 3.9\) & \(-16.4\pm 3.7\) & 0.355 \\ RVfvLS (\%) & \(-20.8\pm 5.2\) & \(-21.3\pm 5.4\) & 0.787 \\ RVGLS/PASP & \(-0.55\pm 0.19\) & \(-0.50\pm 0.18\) & 0.425 \\ RVfvLS/PASP & \(-0.68\pm 0.26\) & \(-0.70\pm 0.26\) & 0.868 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison between patients with and without HR relate worsening of LVGLS. Figure 3: Three examples of changes in RVGLS. The example in (**A**) documents improved RVGLS with increasing HR. The examples in (**B,C**) document no changes and deterioration in RVGLS, respectively, in response to increasing HR. Note that the scale of left and right panels automatically changes according to the strain values recorded.