Increased Risk and Decreased Morbidity of Coronary Artery Bypass Grafting Between 1986 and 1994

doi:10.1016/S0003-4975(97)01125-9

The Annals of Thoracic Surgery

Volume 65, Issue 2, February 1998, Pages 383-389

https://doi.org/10.1016/S0003-4975(97)01125-9 Get rights and content

Abstract

Background. The collective impact of advances in medical, surgical, and anesthetic care on the characteristics and outcomes of patients who undergo coronary artery bypass grafting was assessed.

Methods. We compared the demographic and clinical characteristics, preoperative risk factors, morbidity, and mortality of two groups of patients who underwent coronary artery bypass grafting in isolation or in combination with other procedures between July 1, 1986, and June 30, 1988 (group 1, n = 5,051), and between January 1, 1993, and March 31, 1994 (group 2, n = 2,793). The patients were stratified according to their preoperative risk level. Outcome measures consisted of changes in preoperative risk categories; hospital mortality rates; overall and risk-adjusted major cardiac, neurologic, pulmonary, renal, and septic morbidity rates; and intensive care unit length of stay.

Results. Changes in the distribution of risk categories, from a median of 2 to 4 on a 9-point scale (p < 0.001), indicated that patients in group 2 were at significantly higher risk than those in group 1. The risk-adjusted mortality rate did not change (2.8% to 2.9%; p = 0.15), but the risk-adjusted morbidity rate decreased significantly (14.5% to 8.8%; p < 0.001).

Conclusions. At our institution, patients who undergo coronary artery bypass grafting are now at greater preoperative risk at the time of hospital admission. However, their morbidity rate is significantly lower and their mortality rate is unchanged, results that we attribute to the collective impact of changes in our medical and surgical procedures.

Section snippets

The Cardiovascular Anesthesia Registry

The Cardiovascular Anesthesia Registry was established in 1982 to permit detailed analyses of patient characteristics and outcomes. The registry contains prospectively collected data on all adult patients who undergo cardiac operations at our institution.

The registry is maintained by one full-time database manager and statistician who supervises all data entry and extraction, one full-time database coordinator who is responsible for data entry and verification, and three data abstractors (two

Differences in Risk Scores

The distributions of risk scores differed significantly, with patients in group 2 being at significantly increased risk (p < 0.001 by χ² analysis; Kendall’s tau = 0.102; 95% confidence interval = 0.082 to 0.122, indicating essentially no correlation between the distributions) (Fig. 1). Group 2 had significantly higher percentages of patients in 8 of the 13 risk factor categories, including higher percentages of patients with severe left ventricular dysfunction and emergency operations (Table 1

Comment

This retrospective analysis revealed that the patients admitted today to The Cleveland Clinic for cardiac operations are at greater preoperative risk than were the patients admitted 8 to 10 years ago. This increased risk is accompanied by a significant reduction in the overall morbidity rate (from 14.5% to 9%) and in the morbidity rate of traditionally high-risk subpopulations, such as patients who undergo emergency operations, those who undergo reoperations, and those who are of advanced age.

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Citation Excerpt :
The risk of stroke following 190 449 CABGs was 1.71% (95% CI 1.5–1.9). The incidence was significantly higher in prospective5–37 as opposed to retrospective38–63 studies (2.0% (95% CI 1.7–2.3) versus 1.4% (95% CI 1.1–1.6), p < 0.0001). There was no evidence that the risk of stroke had changed over the last three decades.
To determine the role of carotid artery disease in the pathophysiology of stroke after coronary artery bypass (CABG).
Systematic review of the literature.
The risk of stroke after CABG was 2% and remained unchanged between 1970-2000. Two-thirds occurred after day 1 and 23% died. 91% of screened CABG patients had no significant carotid disease and had a <2% risk of peri-operative stroke. Stroke risk increased to 3% in predominantly asymptomatic patients with a unilateral 50–99% stenosis, 5% in those with bilateral 50–99% stenoses and 7–11% in patients with carotid occlusion. Significant predictive factors for post-CABG stroke included; (i) carotid bruit (OR 3.6, 95% CI 2.8–4.6), (ii) prior stroke/TIA (OR 3.6, 95% CI 2.7–4.9) and (iii) severe carotid stenosis/occlusion (OR 4.3, 95% CI 3.2–5.7). However, the systematic review indicated that 50% of stroke sufferers did not have significant carotid disease and 60% of territorial infarctions on CT scan/autopsy could not be attributed to carotid disease alone.
Carotid disease is an important aetiological factor in the pathophysiology of post-CABG stroke. However, even assuming that prophylactic carotid endarterectomy carried no additional risk, it could only ever prevent about 40–50% of procedural strokes.
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This study was undertaken to assess the impact of increasing patient complexity and health care cost on coronary artery bypass grafting quality and cost-effectiveness in the United States over an 18-year period.
A retrospective study was carried out utilizing the Nationwide Inpatient Sample to track the characteristics and outcomes of 5,549,700 patients having isolated coronary artery bypass grafting in the United States from 1988 to 2005. Expected mortality, risk-adjusted mortality, and hospital charges were tracked over this period.
The prevalence of congestive heart failure, pulmonary disease, diabetes, and acute myocardial infarction increased significantly over the study period. Expected mortality increased from 2.57% to 3.66%, reflecting the increasing patient comorbidity burden (P < .0001). Despite this, coronary artery bypass grafting outcomes improved, leading to a decrease in risk-adjusted mortality from 6.20% to 2.12% (P < .0001). Furthermore, when hospital charges were corrected for medical care inflation, hospital charges declined significantly, from $26,210 in 1988 to $19,196 in 2005 (1988 dollars, P < .0001).
Coronary artery bypass grafting surgery is being performed on an increasingly complex, high-risk patient population in the United States. Despite this challenge, risk-adjusted operative mortality has progressively declined. Moreover, hospital charges for coronary artery bypass grafting in relation to other medical care services have been reduced. These findings reflect improved quality and cost-effectiveness of coronary artery bypass grafting in the United States. Ongoing efforts directed at quality improvement should address the risks associated with comorbidities that increasingly accompany the diagnosis of coronary artery disease in patients having coronary artery bypass grafting.
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The statin group had more comorbidities. Although they had increased risk factors, including previous stroke (30 of 203 vs 16 of 244, p = 0.004), diabetes (66 of 203 vs 32 of 244, p < 0.0001), cerebrovascular disease (45 of 203 vs 24 of 244, p = 0.003), and dyslipidemia (191 of 203 vs 63 of 244, p < 0.0001), they had better outcomes. The unadjusted odds ratio (OR) for the composite end point of death/stroke/renal failure was 1.90 (95% confidence interval [CI], 0.95 to 3.76; p = 0.068) favoring the statin group. By univariate analysis, the adjusted OR for the composite end point demonstrated a benefit with statin therapy: diabetes, 2.29 (95% CI, 1.16 to 4.71; p = 0.024); stroke, 2.15 (95% CI, 1.06 to 4.35; p = 0.034); and renal dysfunction, 2.05 (95% CI, 1.02 to 4.13; p = 0.045).
Statin therapy in this population undergoing cardiac valve procedures was associated with decreased postoperative morbidity and death. The mechanism may be independent of statins' lipid-lowering effects. A prospective, randomized-control trial of statin therapy in this population is warranted.
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A minority of patients develop severe systemic inflammatory response syndrome (SIRS) with high mortality following cardiopulmonary bypass-assisted cardiac surgery. We assessed whether intravenous immunoglobulin G (ivIgG) improves postoperative short-term (5-day) morbidity and reduces 28-day mortality in these patients.
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Of 6,984 patients screened, we identified 244 with severe SIRS (Acute Physiology and Chronic Health Evaluation II score ≥28 on the first postoperative day).
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Original ArticlesIncreased Risk and Decreased Morbidity of Coronary Artery Bypass Grafting Between 1986 and 1994

Abstract

Section snippets

The Cardiovascular Anesthesia Registry

Differences in Risk Scores

Comment

Ann Thorac Surg

J Am Coll Cardiol

J Thorac Cardiovasc Surg

J Thorac Cardiovasc Surg

J Cardiothorac Vasc Anesth

Am J Cardiol

J Cardiothorac Vasc Anesth

Ann Thorac Surg

J Thorac Cardiovasc Surg

J Thorac Cardiovasc Surg

Ann Thorac Surg

J Thorac Cardiovasc Surg

Anesthesia for coronary artery surgerycurrent issues

Ann Cardiac Surg

A 20-year experience in coronary artery reoperation

Eur Heart J

Original Articles
Increased Risk and Decreased Morbidity of Coronary Artery Bypass Grafting Between 1986 and 1994