Background

Invasive cardiac output (CO) is measured with the thermodilution (TD) or the indirect Fick method (iFM) in right heart catheterization (RHC). The iFM estimates CO using approximation formulas for oxygen consumption (\(\dot {\mathrm{V}}\)O₂), but there are significant discrepancies (> 20%) between both methods. Although regularly applied, the formula proposed by Krakau has not been validated. We compared the CO discrepancies between the Krakau formula with the reference (TD) and three established formulas and investigated whether alterations assessed in cardiac magnetic resonance imaging (CMR) determined the extent of the deviations.

Methods

This retrospective study included 188 patients aged 63 ± 14 years (30% women) receiving both CMR and RHC. The CO was measured with TD or with the iFM using the formulas by Krakau, LaFarge, Dehmer, and Bergstra for \(\dot {\mathrm{V}}\)O2 estimation (iFM-K/-L/-D/-B). Percentage errors were calculated as twice the standard deviation of the difference between two CO methods divided by their means; a cut-off of < 30% was regarded as acceptable. The iFM and TD-derived CO ratio was built, and deviations > 20% were counted. Logistic regression analyses were performed to identify determinants of a deviation of > 20%.

Results

The TD-derived CO (5.5 ± 1.7 L/min) was significantly different from all iFM (K: 4.8 ± 1.6, L: 4.3 ± 1.6; D: 4.8 ± 1.5 L/min; B: 5.4 ± 1.8 L/min all p < 0.05). The iFM-K-CO differed from all methods (p < 0.001) except iFM‑D (p = 0.19). Percentage errors between TD-CO and iFM-K/-L/-D/-B were all beyond the acceptance limit (44/45/44/43%), while percentage errors between iFM‑K and other iFM were all < 16%. None of the parameters measured in CMR was predictive of a discrepancy of > 20% between both methods.

Conclusion

The Krakau formula was comparable to other iFM in estimating CO levels, but none showed satisfactory agreement with the TD method. Improved derivation cohorts for \(\dot {\mathrm{V}}\)O₂ estimation are needed that better reflect today’s patients undergoing RHC.

中文翻译：

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根据广泛使用的用于预测心输出量的 Krakau 公式估算 VO2 的准确性

背景

有创心输出量 (CO) 通过右心导管插入术 (RHC) 中的热稀释法 (TD) 或间接菲克法 (iFM) 进行测量。iFM 使用耗氧量近似公式 ( \(\dot {\mathrm{V}}\) O ₂ ) 估算 CO，但这两种方法之间存在显着差异 (> 20%)。尽管经常被应用，但克拉考提出的公式尚未得到验证。我们比较了 Krakau 公式与参考 (TD) 和三个已建立公式之间的 CO 差异，并研究了心脏磁共振成像 (CMR) 评估的变化是否决定了偏差的程度。

方法

这项回顾性研究纳入了 188 名年龄在 63 ± 14 岁的患者（30% 为女性），同时接受了 CMR 和 RHC。CO 通过 TD 或 iFM 使用 Krakau、LaFarge、Dehmer 和 Bergstra 的公式测量\(\dot {\mathrm{V}}\) O2 估算 (iFM-K/-L/-D/- B）。百分比误差计算为两种 CO 方法之间的差异除以其平均值的标准差的两倍；< 30% 的截止值被认为是可以接受的。建立了 iFM 和 TD 衍生的 CO 比率，并计算了 > 20% 的偏差。进行逻辑回归分析以确定偏差 > 20% 的决定因素。

结果

TD 衍生的 CO (5.5 ± 1.7 L/min) 与所有 iFM 显着不同（K：4.8 ± 1.6，L：4.3 ± 1.6；D：4.8 ± 1.5 L/min；B：5.4 ± 1.8 L/min）p  < 0.05）。iFM-K-CO 与除 iFM‑D ( p = 0.19) 之外的所有方法 ( p < 0.001) 都不同 。TD-CO 和 iFM-K/-L/-D/-B 之间的百分比误差均超出可接受限度 (44/45/44/43%)，而 iFM‑K 与其他 iFM 之间的百分比误差均 < 16 %。CMR 中测量的参数均无法预测两种方法之间存在 > 20% 的差异。

结论

Krakau 公式在估算 CO 水平方面与其他 iFM 相当，但没有一个公式与 TD 方法表现出令人满意的一致性。需要改进\(\dot {\mathrm{V}}\) O ₂估计的推导队列，以更好地反映当今接受 RHC 的患者。