In our study, RV function assessment by strain was a better predictor of the primary outcome than the other routinely used parameters; thus, subtle changes in RV function could still predict a worse effect on the outcome. Multivariate analysis revealed that only RV GLS continued to significantly predict poor outcomes in patients with AHF and LVEF < 50%. In contrast, another study showed that RV GLS predicted lower event-free survival in patients with normal LV, but not in those with LV systolic dysfunction. However, this study was conducted on 282 patients with inferior STEMI; only 30% had impaired LVEF [25]. On the other hand, in accordance with our results, Carluccio et al. [26] studied 200 patients with HFrEF for about 28 months and demonstrated that RV strain predicted death and HHF better than FAC, RV S', and TAPSE –the latter was preserved in all patients. However, in this study, the RV FWS was an independent predictor of outcomes, whereas in our study, it was the RV GLS. In another study, RV FAC, TAPSE, and RV strain were able to predict the composite endpoint of all-cause death, reinfarction, and HHF in 621 AMI patients, after a mean follow-up period of 24 months. In multivariate analysis, only RV FWS and RV FAC remained independent predictors of the composite endpoint. Nevertheless, the predictive value of RV strain at a cutoff value of < -2.1% was even more potent than that of FAC. So, like our study, they showed the incremental value of speckle tracking echocardiography over conventional RV functional parameters [27].

In our study, RVD also correlated with lower LVEF, which is similar to the findings of another study on new-onset HF, which showed that HFrEF had more RVD than HFmrEF and heart failure with preserved ejection fraction (HFpEF) (43.5% vs. 30.7%) [28]. In agreement with our findings, a CMR study conducted on patients with DCM and a mean LVEF of 32.9% ± 11.6 showed that reduced LVEF was one of the independent predictors of RVD, which in turn was a strong predictor of cardiac mortality [29]. Interestingly, Movahed et al., using gated equilibrium radionuclide angiography, showed an increasing correlation between RVEF and LVEF with decreasing LVEF and RVEF –the strongest correlation being in those with LVEF and RVEF < 30%, while there was no correlation in patients with normal biventricular EF [30].

In our study, the prevalence of CAD and dyslipidemia was higher in patients with normal RV function. This may be explained by the higher proportion of patients with ACS and de novo AHF with uncontrolled atherosclerotic risk factors. In contrast, RVD was more commonly associated with idiopathic DCM, longer HF duration, and ADHF. In contrast to these findings, Parcharidou et al. [31] reported that RVD was more noticeable in patients having ICM than in those with DCM. Although the mean LVEF was comparable to that in our study (29.3 ± 8 in the DCM group and 27.8 ± 6.3 in the ICM group), they excluded patients with AF, recent myocardial infarction, unstable angina, or severe HTN. On the other side, in accordance with our study, D'Andrea et al. [32] reported that RVD, defined by impaired RV GLS and assessed in 110 patients who were candidates for cardiac resynchronization therapy device implantation, was more pronounced in idiopathic than in ICM patients. Similarly, Grebe et al. [33] demonstrated that RV function, assessed using CMR in 141 patients with LVEF < 35%, was significantly worse in patients with DCM than in those with ICM.

The primary outcome, in our study, occurred in 42% of our patients after a follow-up period of 4.2 ± 3.3 months; CV death occurred in 30.5% and HHF in 23.9% of the patients. These rates are much higher than those seen in the ESC-HF-LT Registry [21]: 23.6% all-cause mortality (51.7% due to CV deaths), 18.7% HHF, and 36% combined endpoint, but their follow-up period was longer (one year). Nevertheless, the in-hospital death rate in our study was lower (4% vs. 4.9%) –both numbers are comparable to the rates reported globally (4–10%). In contrast, in the OPTIMIZE-HF registry, rehospitalization alone and the composite endpoint of death or rehospitalization occurred in 29.6% and 36% respectively, during the 60 to 90 days after hospital discharge. However, their in-hospital death rate was 3.8%, which is lower than ours [34].

As reported in literature, atrial tachyarrhythmia is the most common arrhythmia observed in patients with RVF. In our study, RVD was significantly associated with AF, larger LA dimensions, and increased end-systolic volumes. Similarly, Aziz et al. [35] showed that RVD was a strong predictor of AF in 904 patients with ADHF. RVD was also a predictor of a twofold higher composite endpoint of HHF and all-cause death when compared with those with normal RV [35].

Finally, we found that RVD was significantly associated with longer CCU stays but not with total hospital stays. In contrast, Yamin et al. [36] reported that RV function assessed using TAPSE was a significant predictor of hospital LOS. Although, similarly to our study, they had a high prevalence of CAD and LVEF < 40% (76.5% and 74.1%, respectively), they excluded patients with evidence of ACS, severe TR, and those who died during admission [36].

Our study had some limitations. It was performed at a single center on a relatively small number of patients. Most participants were male and had CAD, which may limit the value of our findings when extrapolated to female and non-ischemic patients. Finally, we did not compare our results to those of 3DE or CMR, which are better modalities for evaluating RV function. However, most of our patients were critically ill, and it would have been difficult to perform a lengthy procedure or one that required patient transfer to the radiology unit.