In this study, we described the prevalence of left ventricular myocardial dysfunction assessed by GLS measurements in a population of patients admitted to the intensive care unit with a good grade SAH (WFNS 1 or 2). On day 1 after hemorrhage, we found altered GLS in 60.6% of patients, a higher prevalence than previously reported in the literature. GLS appears to provide better detection of left ventricular myocardial dysfunction than standard biological, electrocardiographic, or echocardiographic markers.
Markers of left ventricular injury
Acute left ventricular dysfunction in the early phase of SAH is a common complication that appears to be a risk factor for poor neurological outcome and death [11, 27]. In addition, there appears to be an association between long-term cardiac mortality and acute cardiac injury in the initial phase of SAH, highlighting the need for systematic screening for this complication. In the literature, the prevalence of left ventricular dysfunction during SAH varies from 8–28% depending on the study and technique used [13, 28]. In a 2006 study, Banki et al. found left ventricular systolic dysfunction in 28% of patients admitted with SAH of all grades [29]. Left ventricular systolic dysfunction was defined by at least one regional wall-motion abnormality (RWMA). Of these patients, 15% had an LVEF < of 50%. In another 2008 study, Sugimoto et al. reported LVEF < 50% in 11% of patients and RWMA in 28% of patients, all severities grades of SAH included [30]. In 2016, Cinotti et al. were the first to investigate the contribution of GLS to the diagnosis of stress cardiomyopathy during SAH, in the ICU [20]. In their population of poor-grade SAH (WFNS ≥ 3), they found GLS impairment, defined by a GLS > -16%, in 37% of patients, although LVEF impairment occurred in only 10% on day 1. These results were confirmed in 2020 by Kagiyama et al., who found a GLS > -17% in 24% of patients with SAH of any grade, compared with 9% of patients with LVEF < 50% [12]. In this study, GLS > -17% was an independent risk factor for in-hospital mortality. In our study, we focused on the good-grade SAH population. Altered GLS was defined as GLS ≥ -20% and affected 60.6% of patients at day 1, compared with 1.7% with LVEF < 50%. In addition, we found 21.2% of patients with GLS ≥ -17%. Our results showed a higher prevalence of left ventricular dysfunction during SAH than previous studies, although our population was less severe. This could be explained by a better sensitivity of the strain method compared with the usual echocardiographic markers, and by a different definition of altered GLS than in the two previous studies.
Strain ranges
The range of normal strain value remains under discussion, but cardiology literature is increasingly rich. In a recent cohort of 549 healthy volunteers, from the NORRE (Normal Reference Range Echocardiography) study, the value of normal GLS of left ventricle was − 22.5 ± 2.7% [31]. In ICU, higher values are suggested to define impaired GLS, mostly in shocked or ventilated patients [12, 20, 32–34]. In our study, we decided to take a GLS value ≥ -20% as the pathological limit. Our population had very few severity criteria, with a median SAPS 2 at 17 [15–21]. No patient was mechanically ventilated and only a small minority required norepinephrine. GLS depends on loading conditions which vary in patients in the ICU, under mechanical ventilation, under general anesthesia, or in shock [35–37]. For this reason, and because we expected few severity criteria in our population, we chose to use a pathological longitudinal strain value close to that used in conventional cardiology.
Strain over the time
In the definition of adrenergic stress cardiomyopathy, there is a notion of evolutivity, with progressive improvement in left cardiac systolic function. This recovery has been noted in most studies, with significant improvement in the first few days after SAH [20, 29, 38]. However, some studies suggest the possibility of incomplete recovery. Banki et al. found that the prevalence of patients with an LVEF < of 50% did no decrease between the first and seventh days although the RWMA score improved [29]. Similarly, in a prospective cohort examining the rate of cardiac recovery after neurogenic stress cardiomyopathy, Kilbourn et al. found that less than half of patients with initial systolic dysfunction recovered normal cardiac function [38]. In our study, we showed no improvement in longitudinal strain over time. This may be because this work was not designed to study the evolution of cardiac dysfunction, and because systolic function had not yet returned to normal on day 7 in some patients.
Study limitations
Our study has some some limitations. First, strain measurement was only available in 33 patients (44.6%) for the GLS, and in 55 patients (74.3%) for the 4C-LS. The literature on strain measurements in the ICU shows feasibility in the range of 75–89%, much higher than in our study [12, 32, 39]. Second, assessment of RWMA was not included in the protocol, although it is an important marker of neurogenic stress cardiomyopathy. In addition, the value of pathological strain remains controversial, especially in the ICU. There seems to be a difference between the value of pathological longitudinal strain and the value with the best clinical relevance. Finally, external validity is low because our study is the first to examine left ventricular strain in the clinical good-grade SAH population.