The comparison of the outcomes of different surgical techniques is the foundation of progress in cardiac surgery. Still, estimating treatment effects is a complex methodological challenge.

Randomized trials have low risk of bias but limited external validity. On the other hand, observational studies have a higher risk of bias and confounders but are more representative of clinical practice. While in theory biases may lead to an overestimation of the treatment effect in observational studies and the lower external validity may reduce the treatment effect in randomized trials, it has been reported that in other fields the estimates of treatment effects are qualitatively and quantitively similar between the two.¹ Although no data specific to cardiac surgery exist, we believe that this concordance does not hold true for cardiac surgery studies (and probably for surgical studies in general).

不同手术技术结果的比较是心脏手术取得进展的基础。尽管如此，估计治疗效果仍然是一项复杂的方法学挑战。

随机试验的偏倚风险低，但外部有效性有限。另一方面，观察性研究具有较高的偏倚和混杂风险，但更能代表临床实践。虽然理论上的偏差可能导致观察性研究中对治疗效果的高估，而较低的外部有效性可能会降低随机试验中的治疗效果，但据报道，在其他领域，治疗效果的估计在质量和数量上是相似的二。¹虽然不存在特定于心脏手术的数据，但我们认为这种一致性不适用于心脏手术研究（可能也适用于一般的手术研究）。