Analyzing a national database of hospital inpatient records, a team of researchers reports an expected spike in mortality six days after cardiac surgery, but also a more surprising and potentially troubling jump in deaths at the 30-day mark.
In a report on the study, they suggest that while there could be “organic” medical reasons for the extra deaths, the more likely explanation may be an unintended consequence of putting so much emphasis on marking one-month “survival” as a critical measurement of surgical success.
“One possibility for the spike is that by often measuring survival at 30 days, such quality improvement metrics may be inadvertently influencing the timing of end-of-life decision-making and withdrawal of aggressive treatment,” says Johns Hopkins anesthesiologist Bryan G. Maxwell, M.D., M.P.H., who led the research that was conducted when he was a fellow at Stanford University.
After heart surgery, Maxwell says, a certain percentage of patients will die in the first few days or week, and the new increases in-hospital mortality seen in their analysis likely reflect the fact that patients who are going to do well have already been discharged, leaving behind the sickest and most complicated cases.
Imagine you’re on a highway. An accident causes traffic to pile up ahead. Emergency crews redirect cars around the congestion. Finally, you’re able to get back on the road, and the route is clear.
If you need heart bypass surgery, the procedure is pretty similar. A surgeon takes blood vessels from another part of your body to go around, or bypass, a blocked artery. The result is that more blood and oxygen can flow to your heart again.
It can help lower your risk for a heart attack and other problems. Once you recover, you’ll feel better and be able to get back to your regular activities.
Bypass surgery is also known as coronary artery bypass grafting (CABG). It’s the most common type of open-heart surgery in the U.S. Most people have great results and live symptom-free for a decade or more.
Why Do I Need It?
Bypass surgery treats symptoms of coronary heart disease. What happens when a waxy substance called plaque builds up inside the arteries in your heart and blocks blood and oxygen from reaching it. You may feel things like:
- Chest pain, which is known as angina
- Irregular heartbeat
- Shortness of breath
But in a report published online April 9 in the journal Health Services Research, he and his colleagues say they can find no similar “organic” explanation for the spike in deaths at day 30, the most common outcome measure used nationally to assess the postoperative course of cardiac surgery patients in a given hospital. “We observed these shifts in the pattern of mortality, and we don’t have any good medical explanation for them,” says Maxwell, an assistant professor of anesthesiology and critical care medicine at the Johns Hopkins University School of Medicine. “But they raise the possibility that when there’s a motivation to get to that 30-day mark, the very act of measuring may lead to more aggressive treatment behaviours.”
He fears, he says, that the standard but somewhat arbitrary use of 30-day survival as a benchmark of surgical “success” rates may be leading to delays in facing inevitable deaths, increased patient and family discomfort, and additional days in intensive care units.
For the study, Maxwell and his team analyzed data from over 595,000 heart surgery admissions — primarily for cardiac bypass or valve surgery — between 2005 and 2009 in a federal database known as the Nationwide Inpatient Sample. Overall, 19,454 patients (3.27 percent) died in the hospital.
Using statistical modelling, Maxwell determined that if a patient is alive on the 30th day in the hospital, the risk of dying by day 31 is about 1 percent. In contrast, the same statistic for any day the previous week is between .63 percent and .81 percent.
That change in hazard from day 30 to day 31 — an increase of about 35 percent — was the most significant change of any day in the first 60 days, says Maxwell.
Maxwell is seeking funding to study more detailed Medicare data to analyze each patient’s situation more closely and investigate more comprehensively how this pattern of postoperative deaths relates to the types of medical interventions used and the timing of decisions made for patients who do not survive.
Professional societies, hospitals and regulatory agencies measure and report postoperative mortality rates so that patients considering cardiac surgery can compare outcomes for surgeons and hospitals. “There is public pressure to grade surgeons and see how they stack against one another, and one might think that this can’t help but weigh on some of them,” Maxwell says.
Maxwell would like to see more nuanced quality metrics that take into account severity of illness preoperatively and how fully patients recover — for instance, whether they can return home and resume normal activities — instead of just a measure of who is alive or not on day 30.
“If our speculation is correct, we clearly need a way to measure and improve quality without creating perverse incentives,” he says.
When your arteries cannot supply enough blood to your heart, your doctor may recommend coronary artery bypass graft (CABG) surgery. One of the most common heart surgeries in the United States, CABG surgery restores blood flow to your heart.
Approximately every 10 minutes, someone has a beating heart or “off-pump” bypass surgery1. Beating heart bypass surgery is — in simple terms — bypass surgery that is performed on your heart while it is beating. Your heart will not be stopped during the operation. You will not need a heart-lung machine. Your heart and lungs will continue to perform during your surgery.
Surgeons use a tissue stabilization system to immobilize the area of the heart where they need to work.
Beating heart bypass surgery is also called Off-Pump Coronary Artery Bypass Surgery (OPCAB). Both OPCAB and conventional on-pump medicine restore blood flow to the heart. However, off-pump bypass surgery has proven to reduce side effects in certain types of patients.
During the operation
The length of time it takes to carry out open-heart surgery depends on the type of procedure and the needs of the individual. As a guide, the National Heart, Lung, and Blood Institute (NHLBI) state that a coronary artery bypass takes 3 to 6 hours.
To access the heart, the surgeon makes a 6-to-8-inch incision along the middle of the chest. The cut will go through the breastbone.
The medical team might use a heart-lung bypass machine during the surgery. This involves stopping the heart from beating. The bypass machine takes over the heart’s pumping action and removes blood from the heart via tubes. The device then removes carbon dioxide from the blood, adds oxygen, and returns the blood to the body. This surgery is called “on-pump” surgery.
Sometimes, a surgeon might work “off-pump.” When a bypass machine is not in use, the person’s heart keeps beating. A member of the surgical team uses a device to steady the heart while the surgeon performs the procedure.
There is insufficient evidence to confirm whether on-pump open heart surgery is safer than off-pump surgery. However, according to the National Institute for Health and Clinical Excellence (NICE), survival rates one year after either form of open-heart surgery are similar at about 96–97 percent.
Of a total of 1,628 patients undergoing on-pump coronary artery bypass grafting, 141 (8.7%) died. The following risk factors for mortality were identified after logistic regression: dialysis (OR=7.61; 95%CI 3.58-16.20), neurologic dysfunction type I (OR=4.42; 95%CI 2.48-7.81), use of IABP (OR=3.38; 95%CI 1.98-5.79), cardiopulmonary bypass time (OR=3.09; 95%CI 2.04-4.68), serum creatinine on admission and peak values > 0.4mg/dL (OR=2.67; 95%CI 1.79-4.00), age > 65 years (OR=2.31; 95%CI 1.55-3.44), and time between hospital admission and and surgical procedure (OR=1.53; 95%CI 1.03-2.27).
This study identified seven risk factors for mortality in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass. In patients who died, the most common variables included male, pulmonary complications, use of intra-aortic balloons and type I neurological lesion. After logistic regression, risk factors for mortality were as follows: dialysis (OR=7.61 ), neurological damage type I (OR=4.42), use of intra-aortic balloon (OR=3.38), cardiopulmonary bypass time (OR=3.09), creatinine peak – Intake> 0.4 mg/dL (OR=2.67), age> 65 years (OR=2.31) and time between hospital admission and surgery (OR=1.53).
In this research, the mortality rate was 8.7%, close to that recorded by DATASUS for CABG, or that is, 7%. In the period 2005-2007, Piegas et al.analyzed 63,272 CABG surgeries performed in 191 hospitals and found that the mortality rate was 6.2%. Cadore et al., investigating 2,809 patients undergoing CABG alone or combined with valve replacement reported that the mortality rate was 10%. It is noteworthy that the performance of combined surgery increases the risk of mortality.
These mortality rates are higher than in countries like the United States (2.9%) and Canada (1.7%), possibly due to the high prevalence of cardiovascular risk factors among Brazilian who underwent CABG. On the other hand, the comparison of surgical results in national centres for European and North American centres is inadequate, because both the registration of the Society of Thoracic Surgeons (S.T.S.) as the U.K. Cardiac Surgical Register are volunteers, while DATASUS is administrative.
In this study, the peak-admission creatinine ≥ 0.4 mg/dL was considered a risk factor for death. This finding was similar to that found by Machado et al. who studied 817 patients with acute kidney injury (A.K.I.), and found that the creatinine peak-admission ≥0.3 mg/dl was an independent predictor of death in 30 days after on-pump CABG. However, these authors used the criterion proposed by Acute Kidney Injury Network (AKIN) classification, or that is, percentage increase (≥ 50%) or absolute (≥ 0.3 mg/dL) of serum creatinine characterizes A.K.I. In this research, the value of creatinine peak-admission ≥ 0.4 mg/dL were considered as the cutoff point for death by the R.O.C. curve.
The assessment of renal function by serum creatinine in patients undergoing CABG with C.P.B. is essential because even a subclinical increase is considered an independent predictor of death within 30 days after CABG in patients with normal renal function or preoperative renal injury. Besides, A.K.I. after CABG is a common complication that increases the length of hospital stay and I.C.U. and is associated with high morbidity and mortality rates with prognostic importance.
Of the 1,628 patients undergoing CABG with C.P.B., 40 (2.5%) required dialysis postoperatively. The need for dialysis is observed in up to 30.6% of cases. Yehia et al., assessing 104 patients undergoing CABG, found that 41.3% of them developed A.K.I. after surgery, requiring dialysis in up to 9.6%, mainly in those with preoperative renal injury. Santos et al.found that of 223 patients undergoing CABG with C.P.B., dialysis was required in 4.9% of them.
In this series, of 40 patients requiring dialysis postoperatively, 23 (57.5%) died, close to the mortality rate recorded by Santos et al.and Chertow et al.63 6% (n=223) and 63.7% (n=460), respectively. Despite this proximity, the comparison between the studies is complex because it is related to the number and characteristics of hospitals involved in each study, patient profiles and sample size.
The relative risk of death in patients requiring dialysis postoperatively was significantly higher (OR=7.61, 95% CI 3.58 to 16.20; P<0.0001). This finding is consistent with the literature. According to Chertow et al.the need for dialysis increases by 7.9 times the odds ratio of death among these patients. When there is severe renal injury enough to require dialysis, a sharp increase in mortality occurs. Therefore, the identification of preoperative risk factors for A.K.I. may contribute to the use of preventive strategies to minimize risk and improve the treatment of this injury.
The surgery carries many benefits, including some particularly for patients who have serious cardiovascular disease. The operation can save your life if you are having a heart attack or are at high risk of having one. If you have ongoing angina and shortness of breath from diseased heart arteries, elective coronary bypass surgery is highly effective at eliminating or reducing discomfort. Coronary bypass surgery can give you your life back.
Because coronary bypass surgery is an open-heart procedure requiring general anesthesia and in many cases that the heart is stopped during the operation, bypass carries risks. The good news is that recent decades have seen a steep drop in serious complications. Today, more than 95 percent of people who undergo coronary bypass surgery do not experience serious complications, and the risk of death immediately after the procedure is only 1–2 percent.
The risk of serious complications is higher for emergency coronary bypass surgeries, such as for patients who are having a heart attack, when compared to elective surgery for treatment of angina and other symptoms. Additionally, patients may be at higher risk if they are over 70 years old, are female or have already had heart surgery. Patients who have other serious conditions, such as diabetes, peripheral vascular disease, kidney disease or lung disease, may also be at higher risk.
Death. In-hospital death is infrequent after coronary bypass surgery. It is typically caused by heart attack or stroke.
In this series, age> 65 years was considered a risk factor for mortality. This finding was similar to that found by Rocha et al. in patients aged ≥ 70 years. Naughton et al. studied 3,683 patients undergoing CABG and found that age ≥ 75 years was an independent risk factor for mortality within 30 days. However, Aikawa et al. investigating the impact of CABG on 253 elderly patients, found that age ≥ 65 years was not associated with death variable.
Considering the increased prevalence of CAD with age , an increasing number of elderly patients may be candidates to CABG in the coming years. Therefore, a careful assessment of cardiac and non-cardiac variables during pre-, intra- and postoperative patients over 65 years is necessary because age can be associated with other severe comorbidities such as renal and neurological injuries in the postoperative period.
In this study, the C.P.B. time was identified as a risk factor for mortality. The average time in patients undergoing CABG was 94.4 min. In the literature, this time varies from 65.8 to 120 min. In patients who died, the mean C.P.B. time was higher (118.58 min), confirming the findings of Oliveira et al.
The relative risk of death is 209% higher when the C.P.B. time is higher than 115 minutes (OR=3.09, 95% CI 2.04 to 4.68; P <0.001). A primary concern related to cardiopulmonary bypass is systemic inflammatory response syndrome (SIRS), characterized by clinical changes in ventricular function, lung and kidney, coagulation disorders, susceptibility to infections, abnormal vascular permeability and fluid accumulation in the interstitium, leukocytosis, vasoconstriction and hemolysis. It is noteworthy that despite these changes, the body’s ability to reverse this situation, and the use of corticosteroids, an effective alternative in reducing the systemic effects caused by the release of cytokines during and after C.P.B. , can reduce morbidity and mortality rate.
On the other hand, the C.P.B. substitutes the cardiopulmonary functions, seeks to maintain cell integrity, structure, function and metabolism of organs and individual systems, enabling more complex and longer surgeries such as coronary artery bypass grafting.
In this study, the patients studied (n=1,628) 4.4% had neurological damage type I. This finding was consistent with the two most significant series in the literature that assessed more than 16,000 patients undergoing CABG with incidences of 2 to 4.6%. In our country, Guaragna et al. assessing 1,760 patients undergoing CABG with C.P.B. found this lesion in 3% of them.
Among the patients who died (n=141), 19% had neurological injury type I. This result is consistent with previous studies that showed high mortality (13-41%) in patients who have had this injury after CABG.
The relative risk of death in patients with type I neurological injury postoperatively was significantly higher (OR=4.42, 95% CI 2.48 to 7.81; P<0.0001). This finding was similar to that observed by Guaragna et al., and the relative risk of death was 4.6 times higher in patients with this injury. Considering the severity of this type of injury in postoperative patients undergoing CABG with C.P.B., some preventive measures can be adopted as an individualized management strategy for patients with previous cerebrovascular disease, including minimal manipulation of the aorta and maintenance of the highest pressure gradient during C.P.B.
Among the 141 patients undergoing CABG with C.P.B. who died, 21% of them used intra-aortic balloon. This rate was consistent with the literature. In a review of 27 years of IAB use by the Massachusetts General Hospital, mortality among patients who received IAB ranged from 13.6 to 35%.
According to Christenson et al., the preoperative prophylactic use of IAB has excellent value to prevent trans- and postoperative complications. In this sample, the relative likelihood of patients who used this type of device for ventricular assistance to die was significantly high. The use of IAB is related to the existence of low left ventricular ejection fraction and or severe coronary lesions, indicating poor heart condition, which can increase morbidity and mortality rate in patients undergoing CABG with C.P.B.
In patients who died, the median time between hospital admission and surgery was six days. Oliveira et al.found that mortality was higher among patients with the time of preoperative stay less than three days.
Importantly, the hospital stay before surgery may be related to the clinical severity, suggesting an advanced degree of coronary involvement that may result in increased morbidity and mortality rate in the postoperative period.
As limitations of the study, we should mention that it is not randomized. Besides, the influence of preoperative, intraoperative and postoperative mortality of patients undergoing CABG with C.P.B. needs more long-term scientific research. The clinical importance of the results obtained herein reinforces the multidisciplinary approach in patients undergoing coronary artery bypass grafting, especially in the postoperative period.
The identification of risk factors for mortality is critical since this knowledge can support interventions aimed at the planning and execution of new preventive strategies and minimizing the complications associated with this surgery. This information may also be used as an essential care quality indicator in the postoperative period, in this case, provided by SUS.
In patients undergoing coronary artery bypass grafting with cardiopulmonary bypass who died, the more frequent preoperative, intraoperative and postoperative variable were male, pulmonary complications, use of intra-aortic balloon and neurological damage type I.
Dialysis, neurological damage type I, use of an intra-aortic balloon, C.P.B. time (> 115 minutes), creatinine peak-admission> 0.4 mg/dL, age> 65 years and time between hospital admission and surgery were identified as risk factors for mortality in the postoperative period.
Recovery and long-term outlook depend on the overall health of the person and the particular procedure they need.
After recovery from a bypass operation, people should see an improvement in symptoms, such as chest pain and breathlessness.
The surgery also reduces the risk of a heart attack. Open heart surgeries are not necessarily a cure, however. Disease in the coronary arteries can still progress even after a bypass.
Open heart surgery can be a daunting prospect for a newly-diagnosed person, but its success rate is high, and experienced professionals will make the procedure as comfortable as possible.