DOH Home  >>  Office of Health Care Quality Assessment

Coronary Artery Bypass Graft Surgery in NJ, 1994 - 1995


This guide is for patients and families of patients considering coronary artery bypass graft (CABG) surgery. It summarizes the results of a study of CABG surgery in this state and answers many of the questions you may have about this common procedure.

For this study, the Department collected data on the 14,510 patients who had bypass surgery during 1994 and 1995. This information included the patient's health condition prior to surgery and the outcome of the surgery. Using a special "risk-adjustment formula," we are able to offer an overview of the performance of CABG surgery in New Jersey by hospital and cardiac surgeon.

This study was a collaborative effort with a select committee of experts known as the Cardiovascular Health Advisory Panel, which includes physicians who specialize in cardiac surgery, cardiologists and other health care professionals.

We had two goals for this project. The first was to provide hospitals and surgeons with meaningful comparative data about their patients and the outcomes of bypass surgery. There is strong evidence, from the handful of states with similar studies, that this kind of information prompts hospitals to examine their procedures in order to improve the overall quality of bypass surgery and, ultimately, save lives.

We also had another goal -- to give you, the patients, and your families -- data that will help you have more informed discussions with your physicians. Since every patient has different health concerns and risks, we encourage you to discuss the information in this guide with your physicians, who can answer your questions and concerns.

Please remember that the numbers in this guide should not be the only factors you consider when choosing a hospital or cardiac surgeon. Also remember that the data in this guide covers the years 1994 and 1995 and may not reflect the current performance of specific hospitals or cardiac surgeons.

I am confident that New Jersey's risk-adjusted mortality rate for bypass surgery will show a steady improvement in years to come as we publish this report annually. The Department will continue to work with hospitals and physicians to ensure the high quality of cardiac surgery in New Jersey.

Len Fishman



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 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 13 hospitals in New Jersey who offer this type of surgery and 48 surgeons who perform this complex operation. 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.


In 1994-95 there were a total of 14,510 bypass surgeries performed in New Jersey. The number of people who died during or after surgery was 544.

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

In order to produce a fair comparison among hospitals and surgeons, the New Jersey Department of Health and Senior Services has developed a methodology that reports risk-adjusted mortality rates. The risk-adjusted mortality rate gives hospitals and surgeons who operate on sicker patients extra credit, so that they won't be at a disad- vantage in the performance comparisons.

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

  • the patient's age and sex;
  • whether the patient has various diseases such as, diabetes, or kidney failure;
  • whether the patient has had previous heart surgery;
  • whether the main artery that supplies blood to the heart is the one that is blocked;
  • the ability of the patient's heart to pump blood;
  • the need before surgery for a mechanical device to strengthen the heart;
  • whether the patient has various heartbeat irregularities.

Weights were assigned for each of these factors and calculations were performed for each hospital and surgeon to produce risk-adjusted mortality rates as a fairer basis of comparison. The average risk-adjusted mortality rate for the state is 3.75 percent.


This performance report can be used not only by you and your doctor, but also by hospitals and surgeons to improve the quality of their care and their patient outcomes. Evidence from other states that have published performance reports similar to New Jersey's indicates 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 publish annual performance reports on cardiac surgery to promote steady improvement in the state's mortality rate.


Only 13 hospitals in New Jersey are licensed to perform coronary artery bypass surgery. This booklet provides risk-adjusted mortality rates for each of these hospitals. There are variations among hospitals. In some cases the data suggest that these differences are not a matter of chance, but reflect real differences in performance. 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.


A risk-adjusted mortality rate has also been calculated for each of the 48 surgeons who performed at least 100 bypass operations in one hospital during 1994-95. Statistics for surgeons who performed fewer than 100 operations during this period are grouped under the hospital where the operations took place, in an All Others category. These surgeons are not listed by name, because they did not perform the minimum number of procedures necessary for the Department to have confidence in the results of the analysis. For these low-volume surgeons, therefore, risk- adjusted mortality rates are not necessarily an accurate indication of their individual performance.


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 surgeons and hospitals with high volumes have relatively higher mortality rates, while others with low volumes have lower mortality rates. As a group, low volume surgeons in New Jersey (those who performed fewer than 100 procedures in 1994-995) had a significantly higher mortality rate than the state average.


The following three graphs reflect the number of bypass surgeries performed in each hospital during 1994-95; the risk-adjusted performance rates for hospitals; and the risk- adjusted performance rates for surgeons.

Figure 1: Number of CABG Surgeries by Hospital: 1994-1995

This figure shows how many coronary artery bypass operations were performed in each hospital in the two-year period 1994-1995. You can see that some hospitals do more of these procedures than others, with totals ranging from 123 at University Hospital to 1860 at Morristown Memorial Hospital.

Figure 1-A


Figure 2: Hospital Risk-Adjusted Mortality Rates, 1994-95

This graph shows the 1994-95 risk-adjusted mortality rate for each hospital in New Jersey. The risk-adjusted mortality rate takes into account the key risk factors patients have prior to surgery in addition to the actual mortality rate of patients in the hospital.

Figure 2-6

Figure 3: Surgeon Risk-Adjusted Mortality Rates, 1994-95

This graph shows the risk-adjusted mortality rate for each of 48 surgeons who performed at least 100 isolated bypass surgery operations in at least one hospital in New Jersey in 1994-1995. The surgeons are grouped by hospital, and the hospital risk- adjusted mortality rates shown in Figure 2 are repeated as well.

Figure 3-7
Figure 3-8


Figure 3-9
Figure 3-10
Figure 3-11
Figure 3-12

Interpreting the Graphs - "Statistical Significance"

Risk-adjusted mortality rates for each hospital and surgeon in Figures 2 and 3 are shown as circles.

The bars extending on either side of each risk-adjusted mortality rate circle represent the statistical margin of error for the calculation of that rate. The bars are based on 95% confidence intervals. That means we can be 95% confident that the hospital's or surgeon's true risk-adjusted mortality rate falls within the range indicated by the bar.

The length of each bar depends primarily on the number of patients the hospital or surgeon had during the 1994-95 period. The bar is shorter for higher volume providers and longer for lower volume providers, reflecting the fact that larger numbers increase the reliability of a statistic. The length of each bar also depends to a lesser extent on the level of risk presented by each patient.

In addition to circles and bars for the risk-adjusted mortality rates for hospitals and surgeons, there is a vertical line representing New Jersey's statewide mortality rate of 3.75 percent.

When differences are large enough that they are not likely the result of mere luck or random variation, these differences are called "statistically significant." In other words, the differences are probably due to actual differences in performance. When a bar showing a provider's risk-adjusted mortality rate overlaps the line for the statewide mortality rate, there is no statistically significant difference between that provider's rate and the statewide average. However, if the bar does not overlap the statewide rate, there is a statistically significant difference.

For example, in Figure 2 Morristown Memorial Hospital and Hackensack University Medical Center have risk-adjusted mortality rates that are significantly lower than the statewide average, since the bars for those hospitals are entirely to the left of the line representing the statewide rate. The risk-adjusted mortality rate for Newark Beth Israel Hospital is significantly higher than the statewide average rate, since its bar lies entirely to the right of the line.


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 or surgeons with below-average risk-adjusted mortality rates?

A: You should discuss this report with the physician who refers you for cardiac surgery. This is generally a specialist known as a cardiologist. This report, together with the cardiologist's knowledge and expertise, should be helpful in determining the best hospital and surgeon for you. Other considerations may include the type of risk factors you have and the experience of certain hospitals and surgeons in treating patients with those risk factors. You should also keep in mind that the data in this guide is from 1994-995 and that hospitals' and surgeons' performance may have improved since then.

Q: Why doesn't the report contain data for surgeons who performed fewer than 100 bypass operations in 1994-95?

A: When the volume of procedures performed by a provider is relatively small, it is difficult to provide a very precise estimate of that provider's performance. As a result, the Department has omitted individual data for this group. However, as a group low volume surgeons had a significantly higher mortality rate than the state average.

Q: Does that mean that I should avoid any surgeon whose name is not included in this report?

A: No, not necessarily. First, there are lower volume surgeons with good patient outcomes. Second, there may be a good explanation for why a surgeon had a low volume that is unrelated to his/her experience. For example, the surgeon might be beginning his/her career or has recently moved from another state, where he/she performed a high volume of these procedures. It is best to discuss your concerns with your referring doctor.

Q: Should I avoid a surgeon who has a risk-adjusted mortality rate higher than the state average?

A: Not necessarily. The surgeon's rate may not be significantly different from that of other surgeons. Remember, you need to look at the bars as well as the circles. Also, that surgeon may be especially skilled at operating on certain types of patients. It is best to decide on a surgeon with advice from your referring doctor.

Q: Should I refuse to go to a hospital for heart surgery if that hospital has a worse than average mortality record?

A: Important decisions in areas such as cardiac surgery should be made after considering all available information. The statistics in this report are a starting point for discussions with your doctor. But they do not tell the complete story. That is why it is critical to bring your concerns and questions to your doctor.

Q: Is it better to go to a hospital with a high volume of cases and a surgeon who handles a large number of cases?

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

Limitations of Data:

The data used in this study were reported by each hospital, according to criteria established by the Department with assistance from a select committee of experts known as the Cardiovascular Health Advisory Panel (CHAP). The CHAP includes doctors who specialize in cardiac surgery and cardiology and other health care professionals.

The Department took steps to assure that each hospital was kept informed of reporting requirements, the risk-adjustment methodology and auditing requirements. In addition, input was sought from a special research subcommittee of the CHAP, which includes a cardiac surgeon or cardiologist from each of the 13 hospitals. The data was audited by the Peer Review Organization of New Jersey.

With all of these precautions, some hospitals have recently reported to us that there have been "under coding" errors. An under coding error occurs when one or more of a patients' risk factors are not identified, meaning the hospital and surgeon do not get credit for operating on a sicker patient.

These kinds of errors are not unusual, especially the first time such information is made public. Experience indicates that once information is made public, hospitals and surgeons are even more careful to document all relevant risk factors.

Also, as data collection procedures are improved, the Department will be able to capture more information on risk factors, strengthening the analysis of each hospital's risk-adjusted mortality rate.

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) 633-0807.


This document may only be reproduced in its entirety. No portion of this document may be reproduced without the permission of the New Jersey Department of Health and Senior Service.

Privacy policy, terms of use and contact form links State Privacy Notice legal statement DOH Feedback Page New Jersey Home

department: njdhss home | index by topic | programs/services
statewide: njhome | my new jersey | people | business | government | departments | search

Copyright © State of New Jersey, 1996-
Department of Health and Senior Services
P. O. Box 360
Trenton, NJ 08625-0360

Last Modified: Friday, 16-Mar-07 08:03:59