Coronary Artery Bypass Graft Surgery in New Jersey 1998

Message From The Commissioner

We are pleased to present Cardiac Surgery in New Jersey, 1998, the state's third consumer report on coronary artery bypass graft surgery. In 1998, New Jersey hospitals have achieved the lowest patient mortality rate for bypass surgery since 1994-1995, the first years of data reporting by the Department of Health and Senior Services.

This guide provides comparative data on the performance of hospitals offering cardiac surgery. We also hope this guide can answer some of the questions patients may have, and help them discuss their concerns and treatment options with their physicians.

The Department has worked closely with the Cardiovascular Health Advisory Panel to bring consumers and providers the best possible data on cardiac surgery outcomes. This expert panel includes physicians who specialize in cardiac surgery, cardiologists and other health care professionals. I would like to thank the panel members for their efforts.


This guide is for patients and families of patients considering coronary artery bypass graft (CABG) surgery. It provides mortality rates for the 14 hospitals performing this common cardiac surgical procedure in 1998. This is the first report to include data from Saint Francis Medical Center in Trenton, which began performing cardiac surgery in January 1998.

This year's guide is different from previous reports in that it does not report on the performance of individual surgeons. With this guide, the Department of Health and Senior Services makes available performance information based on a refined hospital data reporting system. Subsequent guides will include surgeon performance based on data collected under this statewide system.

For this study, the Department collected data on the 8,377 patients who had bypass surgery in 1998. All data have been "risk-adjusted," which means the data were adjusted to take into account the patient's health condition before surgery. This risk-adjustment allows for fair comparisons among hospitals treating diverse patient populations.

An important goal of this study is to give hospitals data they can use in assessing quality of care related to bypass surgery. There is strong evidence, from the handful of states with similar studies, that this information encourages hospitals to examine their procedures and make changes that can improve quality of care and, ultimately, save lives.

In fact, New Jersey's mortality rate for bypass surgery has shown a dramatic decline. For 1998, the statewide mortality rate following bypass surgery was 2.60 percent. This is nearly a 40 percent improvement since 1994, based on risk-adjustment to reflect the larger number of higher-risk patients undergoing bypass surgery in recent years.

Another goal of the study is to give patients and physicians information to use in discussing questions and issues related to bypass surgery. Please remember that the numbers in this guide are just one factor to consider in deciding where to have cardiac surgery. You and your physician together can make the best choice after full consideration of your medical needs. Also note that data in this guide are from 1998. These data may not reflect the current performance of specific hospitals, which may have revamped their programs since then.

Heart Disease And Cardiac Surgery In New Jersey

Heart disease is the single largest killer of Americans. About every 20 seconds a person somewhere in this country will suffer a heart attack, and about once every minute someone will die from one. In New Jersey, cardiovascular disease, including heart disease, is the leading cause of death.

The most common form of heart disease is coronary artery disease. It occurs when the coronary arteries, which carry blood to the heart muscle, become clogged or partially blocked by fatty deposits on the artery walls. This can lead to chest pain, or angina, which is a warning sign for a heart attack. A heart attack occurs when a coronary artery is totally blocked.

Treatment Options

Treatment for coronary artery disease will vary for different patients. The choice of treatment depends on the nature and severity of the disease and other factors unique to each patient.

For some patients, lifestyle changes such as quitting smoking, eating a low-fat diet, and getting more exercise may be enough. Some patients require special medications. Others may need medical procedures such as angioplasty or coronary artery bypass graft surgery. Angioplasty reduces obstructions of fatty deposits in coronary arteries. Bypass surgery uses an artery or vein taken from another part of the body to divert blood around the clogged part of a patient's artery or arteries.

This guide is about coronary artery bypass graft surgery. It will help you learn about the performance records of 14 hospitals in New Jersey that offered this type of surgery in 1998. This guide will also help you begin talking with your doctor about bypass surgery. You and your doctor should make decisions after taking all available information into account.

Performance Data

In 1998 there were 8,377 isolated bypass surgeries performed in New Jersey. In an isolated bypass surgery, no other major heart procedure is performed at the same time. The number of people who died in the hospital during or after isolated bypass surgery was 218 or 2.60 percent.

In evaluating the performance of hospitals, it would be unfair to make comparisons only on the basis of how many patients died. The mortality risk for patients undergoing bypass surgery varies significantly with how healthy patients are prior to surgery. For instance, a 75-year-old woman, who has diabetes and had previous open heart surgery, would be at higher risk for this surgery than a 50-year-old non-smoking man who had no history of chronic disease.

In order to produce fair comparisons, the New Jersey Department of Health and Senior Services developed a methodology that reports risk-adjusted mortality rates. The risk-adjusted mortality rate gives extra credit to hospitals with sicker patient populations, so that those hospitals won't be at a disadvantage in the performance comparisons.

Each hospital was required to submit data which contain a risk profile for each patient undergoing bypass surgery. Key factors that influence a patient's chance of surviving the operation include:

Weights were assigned for each key risk factor and calculations were performed for each hospital to produce risk-adjusted mortality rates as a fairer basis of comparison.

Performance Reports Lead To Improvement

This performance report can be used not only by you and your doctors, but also by hospitals to improve the quality of their care and their patients' outcomes. In New Jersey, the statewide, risk-adjusted mortality rate for bypass surgery has declined dramatically - nearly 40 percent from 1994 to 1998. Evidence from other states that have published similar performance reports also shows that mortality rates have declined and the overall quality of bypass surgery care has improved substantially. The Department of Health and Senior Services intends to continue to publish performance reports on cardiac surgery to promote the continued steady improvement in the state's mortality rate.


In 1998, 14 hospitals in New Jersey were licensed to perform coronary artery bypass surgery. This booklet provides risk-adjusted mortality rates for each of these hospitals. You will see that there are variations among the hospitals. Through statistical analysis, the Department is able to determine in which cases the differences reflect real differences in performance, and not different levels of risk among patients or random variation. Nevertheless, this data should not be used as the sole factor in making choices about hospitals, but should be part of the discussion between you and your doctor.

Refined Data Reporting System

In 1998, for the first time, all hospitals used one standard system to report patient risk profile data to the Department. This is a system used by the Society of Thoracic Surgeons, a medical specialty society for heart and lung surgeons, and based on guidelines and definitions developed by the American College of Cardiology and the American Heart Association. This more standardized statewide reporting system allows the Department to include more patient risk factors in the calculations that yield comparative performance data among hospitals. As a result, the Department can offer consumers and health care providers data incorporating even more refined risk adjustments than in the past.


This year's report does not include information on surgeons. In switching to the standardized data reporting system, the Department decided to limit this report to one year's data. For each hospital, there are enough cases in one year to give a statistically reliable mortality rate. This is not the case for individual surgeons, however. The next cardiac surgery report, which will include data from 1998 and 1999, will report on individual surgeons who perform at least 100 isolated bypass surgeries in one hospital during the two-year period. Using this higher volume of cases will give a more reliable picture of individual surgeon performance.

Volume Affects Quality

Many studies nationally and in other states have shown that, in general, hospitals and surgeons that perform bypass surgery more frequently have lower patient mortality rates. However, some hospitals and surgeons with high volumes have relatively higher mortality rates, while others with low volumes have lower mortality rates.

Bypass Surgery Volume At New Jersey Hospitals

Figure 1: Number of Isolated Coronary Artery Bypass Graft Surgeries, 1998.

Firgure 1

This shows how many bypass operations were performed in each hospital in 1998. You can see that some hospitals do more of these procedures than others, with totals ranging from 109 at University Hospital to 1,177 at Morristown Memorial Hospital.

Statewide Performance Data

In 1998, the mortality rate for the state was 2.60 percent, based on data on the 8,377 patients who underwent this surgery.

Individual Hospital Performance

Figure 2: Hospital Risk-Adjusted Mortality Rates, 1998.

Figure 2

This shows the risk-adjusted mortality rate for each hospital in New Jersey performing bypass surgery in 1998. The risk-adjusted mortality rate takes into account both the patients' risk factors going into surgery and the actual mortality rate of patients in the hospital.

On the graph, the vertical line represents New Jersey's statewide mortality rate of 2.60 percent. Each hospital's performance is displayed graphically in relation to this statewide average.

Figure 2 shows that two hospitals have bars completely to the left of the statewide average line -- Saint Francis Medical Center of Trenton and Morristown Memorial Hospital. This means that these hospitals' mortality rates were significantly below the statewide average, according to the rules of statistics.

Two hospitals -- Newark Beth Israel Medical Center and Cooper Hospital/University Medical Center -- have bars completely to the right of the line. That means their mortality rates were significantly above the statewide average.

The remaining 10 hospitals have bars that touch the average line. That means that their rates were not statistically different than the statewide average.

Statistical Significance

In trying to determine a hospital's performance, it is important to account for the fact that some differences occur simply due to chance or random variation. Statistical tests are conducted on data so that we can be as certain as possible that the differences are due to actual differences in performance. A difference is called "statistically significant" when it is large enough that it is not likely due to chance or random variation.

The circle on each hospital's bar represents its calculated risk-adjusted mortality rate. However, we can't really be certain that number is the precise rate. We can only be relatively sure that the true rate falls somewhere on the bar. In analyzing data, we use what is called a "95 percent confidence interval," and the bar represents this confidence interval. We are 95 percent confident that the hospital's true risk-adjusted mortality rate falls within the range shown by the bar. Another way of saying it is that the bar represents the statistical margin of error for the calculation of that rate.

When using this report, it is important to remember that the charts are designed to show whether a hospital's risk-adjusted mortality rate is significantly above or below the statewide rate, or whether a rate is statistically the same as the statewide rate. Thus, it is more important to view the bars in relation to the average line than it is to examine the individual calculated rates, or circles on the bars. The chart should not be used to make hospital-to-hospital comparisons, only to compare hospitals to the statewide rate.

In examining the charts, you will see that some bars are shorter than others. The bar is shorter for hospitals performing more surgeries, and longer for those with lower volumes. This reflects the fact that larger numbers -- in this case, more surgeries -- increase the precision of a statistic.

Questions And Answers

These are some commonly asked questions that may be of interest to you as you read this booklet.

Q: Should I go only to the hospitals with below-average risk-adjusted mortality rates?

A: Not necessarily. There are many factors to consider in determining the best hospital for you. Among these are your own personal risk factors and the experience certain hospitals have treating patients with those risk factors. Before making up your mind, you should discuss this report with the physician, usually a cardiologist, who refers you for cardiac surgery. The cardiologist's knowledge and expertise will be a valuable guide in your decision making. You should also keep in mind that the data in this guide is from 1998 and that a hospital's performance may have changed since then.

Q: Why doesn't the report contain data for surgeons who performed bypass operations in 1998?

A: This year's report includes only one year's data. As a result, the number of cases handled by each individual surgeon is too low to make statistically reliable estimates of performance.

Q: Is it better to go to a hospital with a high volume of cases?

A: National studies have demonstrated that, in general, hospitals with higher volume have better results. However, some hospitals with high volumes have relatively high mortality rates, while others with low volumes have lower mortality rates.

Notes on Data:

The data used in this study were reported by hospitals according to criteria established by the Department, with assistance from the Cardiovascular Health Advisory Panel (CHAP). The panel includes doctors who specialize in cardiac surgery and cardiology, and other health care professionals. The data were audited by the independent Peer Review Organization of New Jersey.

Throughout the process of developing this report, the Department has taken steps to make sure that all hospitals were informed about data reporting and auditing requirements, as well as the statistical methods being used to risk-adjust the reported mortality data.

The Department considers it a vital function of hospitals to be able to collect and report complete, accurate medical information on patients. This function is critical not only to the success of the cardiac surgery report, but to the hospitals' own ongoing efforts to improve the quality of care for all patients. The Department and hospitals will continue working to improve data collection procedures so that this report contains the best possible information.

To obtain a copy of this guide, please contact the New Jersey Department of Health and Senior Services, Office of Research and Development, PO Box 360, Trenton, NJ 08625, (888) 393-1062, fax (609) 292-6523.

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