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Impact Of Transfusion Threshold On Cardiovascular Events Following Complex Endovascular Thoracoabdominal Aortic Repair
Arunvijay R. Iyer, BA¹, Anastasia Plotkin, MD¹, Sukgu M. Han, MD, MS¹, Li Ding, MD, MPH¹, Fred A. Weaver, MD, MMM¹, Mahmoud B. Malas, MD², Gregory A. Magee, MD, MSc¹.
¹University of Southern California, Los Angeles, CA, USA, ²University of California San Diego, San Diego, CA, USA.

OBJECTIVES: While it has been shown that anemia negatively affects outcomes, the optimal transfusion threshold for patients undergoing aortic surgery remains unclear and controversial. The purpose of this study was to evaluate the impact of blood transfusion on cardiovascular outcomes in patients undergoing complex endovascular thoracoabdominal aortic repair (cEVAR).
METHODS: After excluding ruptures, patients undergoing cEVAR in the Vascular Quality Initiative database were stratified by lowest postoperative hemoglobin (Hgb) level (<7, 7-8, 8-9, 9-10, >10 g/dL) with the primary exposure variable being red blood cell transfusion. The primary endpoint was postoperative major adverse cardiac events (MACE), including myocardial infarction, heart failure, dysrhythmia, and stroke. Secondary endpoints were in-hospital mortality and 1-year survival.
RESULTS: Of the 4,966 cEVAR patients who met criteria for analysis the cohorts were: Hgb <7 (452, 9%), Hgb 7-8 (708, 14%), Hgb 8-9 (809, 16%), Hgb 9-10 (852, 17%), and Hgb >10 (2145, 43%). The rate of transfusion by group was (89%, 74%, 40%, 21%, 6%). MACE increased in lower Hgb groups as did in-hospital mortality; however, transfusion was associated with higher MACE in each Hgb cohort. Table 1 In-hospital mortality was higher in transfused patients within all Hgb levels except <7 and 1-year survival was lower in the 8-9, 9-10, >10 Hgb groups for transfused patients. After accounting for other covariates, on multivariable analysis transfusion remained a strong independent predictor for MACE. Transfusion of ≥3 units was also independently predictive of MACE (OR: 4.0, p<.0001), in-hospital mortality (OR: 5.0, p<.0001), and 1-year mortality (OR: 3.0, p<.0001).
CONCLUSIONS: While more severe anemia level is associated with worse outcomes, the use of transfusion does not attenuate the negative impact of anemia, rather it is independently associated with increased MACE and lower 1-year survival for Hgb thresholds above 7 g/dL. Thus, a transfusion threshold of 7 g/dL appears to be a safe strategy, while transfusion above 8 g/dL is associated with lower 1-year survival. These data suggest that a liberal transfusion strategy (>8 g/dL) should be avoided in patients undergoing cEVAR.

Table 1: Outcomes of MACE and mortality by transfusion within each hemoglobin cohort

	<7 g/dL		P-value	7-8 g/dL		P-value	8-9 g/dL		P-value
Transfusion	Yes	No		Yes	No		Yes	No
MACE	33%	16%	.048	23%	14%	.008	19%	6%	<.0001
In-hospital mortality	17%	9%	.33	8%	3%	.04	8%	0.6%	<.0001
1-year survival	66%	78%	.267	78%	84%	.058	79%	91%	<.0001
	9-10 g/dL		P-value		>10 g/dL			P-value
Transfusion	Yes	No			Yes		No
MACE	14%	7%	.0006		13%		3%	<.0001
In-hospital mortality	6%	0.5%	<.0001		5%		0.3%	<.0001
1-year survival	85%	94%	<.0001		86%		95%	<.0001

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