Searching in databases and registers identified 8760 studies. After removing duplicates and title and abstract screening, 56 full text studies were assessed for eligibility and 19 studies were identified. An additional 10 eligible studies were identified through search engines and handsearching of reference lists of included studies, with a total of 29 studies included in the review (Fig. 1) [24,25,26,27,28,29,30, 56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77].

PRISMA flow diagram of search results and study selection

Key characteristics of the included studies are summarized in Table 1. Mean age of the population across studies ranged from 49 to 68 years (average: 59 years [SD 5.2]) and the proportion of male patients ranged from 42.3 to 84.5% (mean 62.6% [SD 11.9]). Patient spectrum varied across the studies, mainly in the inclusion (13 studies) [24, 29, 30, 56, 61, 63, 65, 70, 72,73,74, 76, 77] or exclusion (13 studies) [25, 27, 57,58,59,60, 62, 64, 66, 67, 69, 71, 75] of patients with previous heart disease. See e-Table 1 (Additional File 1: e-Appendix 4) for additional information.

Cardiac ultrasound was conducted as POCUS in 5 studies [28, 30, 59, 72, 74] and as a TTE in 20 studies (either standard [24, 26, 29, 60,61,62, 66, 67, 70, 71, 73, 75, 76] or limited-TTE).[25, 27, 57, 58, 63, 64, 69] Cardiac ultrasound operators were from the cardiology department in 6 studies (cardiologists, cardiology fellows or sonographers),[27, 60, 63, 66, 67, 76] emergency department in 6 studies (emergency physicians or residents),[28, 30, 57, 59, 72, 77] sonographers without a description of department or training backgrounds in 3 studies[24, 29, 75], and not reported in 11 studies.[25, 26, 56, 58, 62, 64, 65, 68,69,70,71] In two studies, the person performing the ultrasound was described as “an experienced operator” [61, 73] and in one study was performed by 3rd year medical students [74]. The timing of cardiac ultrasound varied widely across all studies. Of note, nine studies reported ultrasound was conducted at arrival to the ED or immediately after arrival [24, 29, 60, 69, 70, 72, 73, 75, 76], during the first 4 h[63], 8 h [25], 12 h [62],or 24 h [71], and in most studies [16] the timing of ultrasound was not reported [27, 28, 30, 56,57,58,