Time to Calm the Fick Down? A Systematic Review and Meta-Analysis of Thermodilution Compared to Direct Fick in Tricuspid Regurgitation

BackgroundMany clinicians consider thermodilution (TD) cardiac output (CO) unreliable in patients with tricuspid regurgitation (TR). No systematic appraisals of this clinical question have been conducted. We hypothesized that the inaccuracy of TD in TR, compared to direct Fick (DF) CO, is overstated.MethodsWe performed a systematic search of six major literature databases from 1946 to July 2023. Studies were included if both TD and DF CO measurements were included in patients with and without TR. Meta-analysis of the correlation between TD and DF was performed, stratified by the presence of TR.ResultsA total of 1,064 studies were identified, of which eight met inclusion criteria. Four of the studies were included in the pooled analysis. The presence of TR did not affect the correlation between TD and DF CO (moderate to severe TR: r = 0.90, 95% confidence interval [CI] 0.76, 0.96; mild or no TR, r = 0.86, 95% CI 0.71, 0.93). Many studies had high heterogeneity and risk of bias.ConclusionThe accuracy of thermodilution cardiac output, compared to the gold-standard direct Fick method, may not be meaningfully affected by the presence of moderate to severe tricuspid regurgitation. Given high heterogeneity and risk of bias of included studies, these findings should be replicated in a modern cohort.