A letter to the editor in response to “Association between vasoactive–inotropic score, morbidity and mortality after heart transplantation”

Dear Editor,

We have carefully read the recent publication published by Thome et al. on vasoactive-inotropic score (VIS)-associated morbidity and mortality after a heart transplant, which we believe is the first study to investigate this topic [1]. The authors' findings demonstrate a significant association between maximum VIS_, measured within the initial 24 h after a heart transplant (VIS_max), and reduced 1-year survival rates. We would like to respond to the authors' conclusion and call for a multicentric study and further investigation to support their thesis.

Using data from our centre collected between 2012 and 2021, which included 189 patients who received heart transplants, we were able to validate and replicate the authors' results in a contemporary Eurotransplant cohort. Due to data availability, our approach to performing calculations differed from that of Thome et al.: We calculated the VIS upon admission to the intensive care unit (VIS_0h) instead of the maximum score within the first 24 h. Our analysis revealed a median VIS_0h of 15.5 (9.1–28.5), which contrasted with the authors’ median VIS_max of 39.2 (19.4–83). We categorized the patients in 4 groups, as did the authors, and observed post-transplant 1-year survival rates of 96.7% for the 16th percentile, 92.2% for the 17‒50th percentile, 85.7% for the 50‒83rd percentile and 68.8% for the >83rd percentile of VIS_0h. These results were statistically significant (P = 0.002 vs P = 0.030). We also found an association between length of stay in the intensive care unit and VIS groups (VIS_0h  P = 0.026 vs VIS_max  P = 0.002). However, we did not observe significant associations between VIS_0h and the need for renal replacement therapy (P = 0.077 vs P < 0.001), length of mechanical ventilation (P = 0.103 vs P < 0.001) or length of inotropic support (P = 0.713 vs P < 0.001).

However, it is crucial to acknowledge that there were differences in our baseline parameters compared to the authors' population, possibly due to variations in recipient selection rules between France Transplant and Eurotransplant. Our patients differed i.a. in age, long-term mechanical circulatory support rates, and ischaemic times [48.0 years ± 12.3 years vs 54 years (47–62 years), 47.6% vs 17.2% and 275.4 min ± 55.2 min vs 198 min (164.5–228.5 min), respectively].

Despite these findings, several questions remain unanswered. Although the authors identified an association between VIS and 1-year survival, the underlying reasons for the increased requirement of catecholamines remain unclear. Additionally, we believe it is important to address intraoperative parameters, including the administration of red blood cell units, which have been linked to impaired 1-year survival [2]. In the ongoing debate surrounding the influence of ischaemic time on 1-year survival, it is noteworthy that extensive research has been dedicated to exploring non-ischaemic organ preservation methods. Furthermore, investigators have examined the impact of ischaemic time on adverse events, such as the need for renal replacement therapy [3–5]. Although the authors explored ischaemic time, this aspect was not discussed in their final paper.

We appreciate the opportunity to externally validate the authors' results. However, we strongly urge further research into the underlying causes.

DATA AVAILABILITY

The data underlying this article will be shared on reasonable request to the corresponding author.