Left Upper Lobectomy After Coronary Artery Bypass Grafting: A National Analysis of Postoperative Outcomes

Abstract

Background

To determine whether previous coronary artery bypass grafting (CABG) is a risk factor for postoperative mortality, morbidity, or worse quality metrics in patients undergoing left upper lobectomy.

Methods

Using International Classification of Diseases 10th revision codes, the Healthcare Cost and Utilization Project Nationwide Readmissions Database was queried for patients with pulmonary neoplasms undergoing left upper lobectomy from 2016 to 2018 and categorized by history of CABG. Sociodemographic factors, comorbidities, and hospital characteristics were analyzed using univariable and multivariable regressions.

Results

A total of 11,118 patients met inclusion criteria, of whom 465 (4.2%) had a history of CABG. On bivariate analysis, postoperative myocardial infarction and atrial fibrillation rates were higher (P < .004) in patients with prior CABG. However, multivariable modeling revealed no association between history of CABG and worse outcomes across all metrics: in-hospital mortality (odds ratio [OR], 0.806; P = .563), cardiovascular complications (OR, 0.826; P = .0985), pulmonary complications (OR, 0.849; P = .154), length of stay (relative risk, 0.982; P = .619), 30-day readmission (OR, 1.057; P = .747), and 90-day readmission (OR, 1.137; P = .396). Thoracotomy patients experienced worse outcomes across all metrics (P < .05) compared with thoracoscopy. Prior CABG was not associated with worse outcomes in either thoracoscopy or thoracotomy subgroup analyses. Although not statistically significant (P = .255), patients with previous CABG had approximately $6500 in additional charges.

Conclusions

Prior CABG in patients undergoing left upper lobectomy is not associated with increased mortality, morbidity, length of stay, readmissions, or increased hospital charges. Thoracoscopy may be preferred in this population and is associated with improved outcomes compared with thoracotomy.

Visual Abstract

In Short.

• ▪Prior coronary artery bypass grafting in patients undergoing left upper lobectomy was not associated with increased in-hospital mortality, cardiovascular/pulmonary complications, length of stay, readmissions, or total charges. These findings persisted in both thoracoscopic and thoracotomy subgroups.
• ▪Thoracoscopy was associated with improved outcomes compared with thoracotomy in this unique patient population and may be the preferred approach.

Many patients undergoing thoracic oncology evaluation may have history of coronary disease requiring coronary artery bypass grafting (CABG). Because the overwhelming majority of CABGs utilize the left internal mammary artery (LIMA), any future left-sided pulmonary resection becomes more technically challenging owing to adhesions between the LIMA graft and lung.¹ Thus, surgical decision-making for patients with a history of CABG requiring a left upper lobectomy is less straightforward.

Safety of lobectomy in patients with a CABG history has been demonstrated for both open¹ and thoracoscopic approaches² with no differences in perioperative mortality, morbidity, or oncologic outcomes. However, the existing literature has analyzed small, single-institution case series or case reports^3,4 and is skewed towards thoracotomies. As such, differences between thoracoscopic and open approaches require investigation. With an increasing focus on outcomes/quality metrics, analyses of larger datasets with broader clinical and administrative implications are needed.

The objectives of this study were to utilize a national database to determine whether previous CABG is a risk factor for (1) postoperative mortality and morbidity or (2) worse quality metrics (ie, length of stay, 30- and 90-day nonelective readmission, total hospital charges) in patients undergoing left upper lobectomy. With this information, thoracic surgeons can better understand the perioperative risks and potential quality metric impacts associated with these operations and counsel patients more effectively.

Patients and Methods

Data Source

Data were sourced from the Healthcare Utilization Project Nationwide Readmission Database (HCUP-NRD), sponsored by the Agency for Healthcare Research and Quality. The HCUP-NRD is the largest publicly available inpatient care database that contains data on approximately 18 million hospital discharges annually and includes patients covered by Medicare, Medicaid, private insurance, and the uninsured.⁵ All patient data in the HCUP-NRD are deidentified. This study was approved by the University of Southern California institutional review board (HS-16-00906).

Study Population and Design

Patients with a primary pulmonary neoplasm who underwent left upper lobectomy between 2016 and 2018 were identified using International Classification of Diseases, 10th revision (ICD-10) (Supplemental Table 1). Those with nonelective hospitalizations, undergoing chemotherapy or radiation therapy, aged less than 18 years, missing length of stay or survival data (Supplemental Table 2), or other malignancies (Supplemental Table 3) were excluded. The resulting cohort was stratified by prior surgical history of CABG (Figure 1).

Figure 1.

A schematic diagram showing the cohort selection process. Arrows indicate consecutive steps in cohort selection. (CABG, coronary artery bypass grafting; HCUP-NRD, Healthcare Utilization Project Nationwide Readmission Database.)

Primary outcomes were in-hospital mortality, cardiovascular complications (Supplemental Table 4), and pulmonary complications (Supplemental Table 5). Secondary outcomes included quality metrics: 30-day and 90-day nonelective readmissions, length of stay, and total charges billed by the hospital.

Statistical Analysis

All variables were reported as mean with t test or frequency with χ² test between CABG status. Multivariable regression was used to evaluate association between CABG status and outcomes. Logistic regression was used for in-hospital mortality, pulmonary and cardiovascular complications, and 30- and 90-day readmissions. Hosmer-Lemershow fitness was used for the model's overall fitting. A negative binomial model was used for hospital length of stay to adjust for variance inflation and linear regression for hospital charges. All costs were converted to reflect costs as of January 2023. Model assumptions were checked by Q-Q plot and residual plots. The generalized estimation equation was applied to all models to account for the hospital clustering effect. Significance was defined as a 2-sided P value ≤ .05. All analyses were performed using SAS 9.4 (SAS Institute Inc).

Results

In total, 11,118 patients met inclusion criteria and underwent left upper lobectomy between 2016 and 2018 in the HCUP-NRD database (Table). Of these, 465 (4.2%) had a history of CABG. On bivariate analysis, patients with prior CABG were significantly more likely to have cardiovascular complications (26.2% vs 18.6%; P < .001), 90-day nonelective readmissions (18.5% vs 13.1%; P = .005) (Supplemental Table 6), longer length of stay (6.9 average days vs 6.0 days; P < .001) and greater total charges billed by the hospital ($152,797 average vs $133,529; P < .001). The rates of postoperative myocardial infarction (P = .004) and atrial fibrillation (P < .001) were significantly higher in patients who had a history of CABG (Supplemental Table 7). However, on multivariable analysis, the history of CABG was not associated with postoperative myocardial infarction (odds ratio [OR], 1.958; 95% CI, 0.786-4.878; P = .1491) or postoperative atrial fibrillation (OR, 0.836; 95% CI, 0.664-1.052; P = .126). While patients with a prior CABG on average had approximately $6500 additional charges billed by the hospital, this difference was not significant (P = .255).

Table.

Univariate Analysis of Demographic Characteristics for Patients Who Underwent Left Upper Lobectomy Stratified by CABG History in the Healthcare Utilization Project Nationwide Readmission Database between 2016 and 2018

Characteristic	No History of CABG (N = 10,653)		History of CABG (N = 465)		P Value
	n	%	n	%
Age, y					<.001
<62	2711	25.4	37	8
62-67	2236	21	104	22.4
68-73	2786	26.2	148	31.8
≥74	2920	27.4	176	37.8
Sex					<.001
Male	4713	44.2	379	81.5
Female	5940	55.8	86	18.5
Primary insurance					<.001
Missing	< 10	0.1	0	0
Medicare	6902	64.8	365	78.5
Medicaid	680	6.4	< 10	1.9
Private insurance	2795	26.2	78	16.8
Other	270	2.5	13	2.8
Elixhauser index					<.001
0	1020	9.6	11	2.4
1	2117	19.9	39	8.4
2	2688	25.2	86	18.5
≥3	4828	45.3	329	70.8
Income quartiles					.04
Missing	124	1.2	14	3
0-25th percentile	2393	22.5	99	21.3
26th-50th percentile	2791	26.2	145	31.2
51st-75th percentile	2807	26.3	117	25.2
76th-100th percentile	2538	23.8	90	19.4
Smoking history					<.001
No	2788	26.2	74	15.9
Yes	7865	73.8	391	84.1
Patient residence same as hospital state					.51
No	847	8	41	8.8
Yes	9806	92	424	91.2

CABG, coronary artery bypass grafting.

Compared to patients without prior bypass grafting, there was no association between a history of CABG and worse outcomes across all metrics: in-hospital mortality (OR, 0.806; 95% CI, 0.388-1.675; P = .563), cardiovascular complications (OR, 0.826; 95% CI, 0.658-1.036; P = .098), pulmonary complications (OR, 0.849; 95% CI, 0.678-1.063; P = .154), length of stay (relative risk, 0.982; 95% CI, 0.914-1.055; P = .619), 30-day readmission (OR, 1.057; 95% CI, 0.754-1.482; P = .747), and 90-day readmission (OR, 1.137; 95% CI, 0.845-1.529; P = .396) (Figure 2).

Figure 2.

Forest plot demonstrating that a history of coronary artery bypass grafting is not associated with worse outcomes (all P > .05) for patients undergoing left upper lobectomy in the full cohort and in both thoracoscopy and thoracotomy subgroups. (RR, relative risk.)

Thoracoscopy vs Thoracotomy: Subgroup Analyses

For the 6258 patients undergoing thoracoscopy, there was no statistically significant association between a history of CABG (225 [4%]) and worse outcomes across any metric (Ps > .05) on multivariable regression. For the subgroup undergoing thoracotomy, there was similarly no statistically significant association between CABG history and outcomes (Figure 2).

Compared to thoracoscopy, patients undergoing thoracotomy had statistically significant increased odds to experience worse outcomes: in-hospital mortality (OR, 2.577; 95% CI, 1.739-3.820; P < .001), postoperative pulmonary complications (OR, 1.302; 95% CI, 1.179-1.437; P < .001), postoperative cardiovascular complications (OR, 1.354; 95% CI, 1.217-1.506; P < .001), longer length of stay (RR 1.379; 95% CI, 1.334-1.425; P < .001), 30-day readmissions (OR, 1.206; 95% CI, 1.040-1.399; P = .013), and 90-day readmissions (OR, 1.273; 95% CI, 1.110-1.461; P < .001). Thoracotomy was associated with $17,850 in incremental total charges (P < .001).

Comment

This study of 11,118 patients from the HCUP-NRD who underwent left upper lobectomy indicates that there is no association between a history of CABG and worse outcomes across any metric (ie, in-hospital mortality, cardiovascular and pulmonary complications, length of stay, 30- and 90-day readmissions, and total charges billed by the hospital). For both thoracoscopy and thoracotomy subgroups, there was similarly no association between prior CABG and worse outcomes. Compared with thoracoscopy, thoracotomy was associated with significantly worse postoperative morbidity, mortality, length of stay, readmissions, and total charges (all P < .05).

Existing literature has summarized descriptive outcomes of individual institutional experiences,^1,6,7 inclusive of thoracotomy and video-assisted thoracoscopy, with no study comparing outcomes between thoracoscopy and thoracotomy in this higher-risk patient population. In the present study, however, the rates of all postoperative morbidity were lower for those undergoing thoracoscopy. Thus, these data suggest that a minimally invasive approach is preferable for patients with a history of CABG.

To date, Serna-Gallegos and associates⁷ have described the largest comparable cohort with 88 total pulmonary resections (all performed via thoracoscopy) after prior sternotomy, of which 71 had prior coronary artery bypass grafting. However, conversion to open was required in 14 patients (15.9%) and only 26 (37%) included the left upper lobe: 21 left upper lobectomies and 5 trisegmentectomies. By utilizing a national database, the present study examined 465 patients undergoing left upper lobectomy after CABG, with 225 (48%) undergoing thoracoscopy.

Utilization of a LIMA graft in every patient’s prior CABG is a core assumption, as evidenced by published benchmarks quantifying the mean use of the internal mammary artery graft as 93.6% (interquartile range, 89.9%-96.0%),⁸ in accordance with The Society of Thoracic Surgery guidelines. Even if 93.6%-96.4% of this study’s patients who underwent left upper lobectomy with a CABG history (465) had a LIMA graft, that yields 435-448 patients and thereby maintains the robust size of the cohort studied.

Proximity of the assumed LIMA bypass graft to the operative field could alter coronary blood flow, causing arrhythmic or ischemic disturbances. However, history of CABG was not associated with increased rates of postoperative atrial fibrillation or myocardial infarction after left upper lobectomy, consistent with prior studies.^1,2 There are various techniques to perform this dissection, including leaving small wedge of lung parenchyma adjacent to graft (which carries increased risk of local recurrence, though no oncologic compromise reported³), using advanced energy or vessel-sealing devices, and utilizing limited electrocautery at safe distance from graft with sharp dissection via endoscopic or open devices and use of hemostatic agents when dissecting close to graft.⁹

There are limitations associated with this retrospective study. The incorporation of clinical decision-making data may have provided insight as to why 44% (4860) of the study’s total cohort underwent thoracotomy instead of thoracoscopy. For minimally invasive surgeries, the NRD unfortunately does not distinguish between video-assisted and robotic-assisted thoracic surgery – only open and thoracoscopy. Furthermore, because the sequence of ICD-10 is unknown, the Nationwide Readmission Database does not provide the granularity necessary to discern rates of conversion from thoracoscopy to thoracotomy. Lastly, the study design is predicated upon ICD-10 codes to define the cohorts, covariates, and outcome variables. As such, despite national coding standards, the recorded results still may be influenced by institutional variation in coding practices.

In conclusion, prior CABG in patients undergoing left upper lobectomy is not associated with worse postoperative mortality, morbidity, or quality metrics. This finding persisted in both subgroup analyses of thoracoscopy and thoracotomy only. Although there were increased rates of postoperative myocardial infarction, atrial fibrillation, and 90-day readmissions, these were not significant on multivariable modeling. Thoracoscopy was associated with improved outcomes compared with thoracotomy and may be the preferred approach. With this information, surgeons can better understand the clinical risks and outcomes implications when crafting surgical plans for this unique patient population.