Coronary Artery Bypass Graft Surgery in New Jersey 1994-1995
A Technical Report

November 1997

Cardiovascular Health Advisory Panel (CHAP)

Coronary Heart Disease and Coronary Artery Bypass Graft Surgery

Coronary heart disease (also known as coronary artery disease or ischemic heart disease) occurs when the coronary arteries, which carry blood to the heart, are clogged with fatty deposits on the artery walls. This can lead to angina (chest pain) that is caused by oxygen deficiency, particularly when the arteries are closed by 50% or more. Furthermore, angina is a warning sign for heart attack, when a coronary artery that carries blood to the heart is occluded or blocked. This leads to starvation of a portion of the heart muscle and an area of heart tissue that is no longer alive.

It has been estimated that almost 14 million Americans have coronary artery disease, and that coronary artery disease or other cardiovascular diseases caused nearly 1 million deaths in the United States in 1994- one out of every 2.4 deaths that occurred.

One of the primary treatments for coronary heart disease is coronary artery bypass graft (CABG) surgery, which consists of using a vein in the patient's leg or an internal mammary artery to create a detour around the blocked portion of the patient's coronary artery. Nationally, in 1994, 501,000 people were estimated to have undergone CABG surgery. A total of 14,510 people underwent isolated CABG surgery (patients without acute mitral regurgitation undergoing CABG surgery with no other major heart operations during the same hospital admission) in New Jersey in 1994-1995; these people, the hospitals in which they underwent surgery, and the surgeons who performed the surgery are the subject of this report.

New Jersey's Quality Improvement Program For CABG Surgery

Under the expert guidance of the Cardiovascular Health Advisory Panel (CHAP), the New Jersey Department of Health and Senior Services has initiated a program whereby the 13 hospitals in the state who have the Department's approval to perform coronary artery bypass graft (CABG) surgery submit detailed information to the Department for analysis and feedback to hospitals, surgeons, and the public.

Information that is collected for each patient undergoing CABG surgery in New Jersey includes demographics, pre-operative risk factors, complications that occur during or after surgery, and discharge status(died in the hospital, discharged alive). These data have been collected since 1993, and advice has been sought throughout the process from the Cardiovascular Health Advisory Panel.

Analyses consisted of identifying the pre- operative risk factors that were significantly associated with patients' chances of being discharged alive, and using statistical methods to develop a formula for predicting each patient's probability of in-hospital mortality based on those risk factors. This information was then used to assess the average pre- operative severity of illness for each hospital's (and each surgeon's) patients. The next step consisted of using the mortality rate for each hospital's (and each surgeon's) patients in conjunction with their severity of illness to arrive at a "risk-adjusted mortality rate" that serves as a measure of quality of care. This report provides risk-adjusted mortality rates for 1994-1995 for all hospitals in which CABG surgery is performed, and for all surgeons performing 100 or moreisolated CABG operations in at least one hospital (CABG surgery without any other major heart surgery performed during the same admission, on patients without acute mitral valve regurgitation).

The release of this information to hospitals, surgeons, and the public in New York and Pennsylvania has lead to numerous hospital quality improvement initiatives and significant decreases in mortality rates in those states, and the Department is confident that this and subsequent releases in New Jersey will have the same effect. Another reason for the report is to enable consumers and potential patients to become more informed about their options and to be aware of patient outcomes associated with CABG surgery providers (hospitals and surgeons).

The following is a description of the patient population and the process for calculating risk- adjusted mortality rates for hospitals and surgeons. The statistical model that is used, along with all significant pre-operative risk factors, is also presented. The last section presents risk-adjusted mortality rates for hospitals and surgeons in New Jersey for 1994- 1995.

Patient Population

The patients represented in this report are the 14,510 patients who have undergone isolated coronary artery bypass graft (CABG) surgery (CABG surgery with no other major heart surgery during the same admission and without acute mitral valve regurgitation) in New Jersey in 1994 and 1995. The total number of these patients who died during or after surgery in the same admission was 544, and the in- hospital mortality rate was 3.75%.

Assessing Hospital and Surgeon Performance For CABG Surgery By Calculating Risk-Adjusted Mortality Rates

Provider (hospital and surgeon) performance for CABG surgery is assessed by looking at patient outcomes and how they compare with outcomes throughout the state. Ideally, "patient outcomes" include such things as whether the patient died during or after surgery, what complications of surgery they suffered, their long-term survival, and their satisfaction with the care they received. This report concentrates on in-hospital mortality, which is arguably the most important outcome.

In-hospital mortality is affected by the pre-operative severity of illness of CABG surgery patients as well as by the quality of surgery and hospital care patients receive. Consequently, if some hospitals treat sicker patients, they will have higher mortality rates even if their quality of care is comparable to hospitals with patients who are not as sick. Thus, it is important to try to adjust for differences in patient severity of illness when reporting outcomes. The following is a description of how this is done when reporting hospital and surgeon outcomes.

Data Collection and Data Quality Audit

All 13 hospitals in New Jersey in which cardiac surgery is performed collect detailed patient- specific information related to the patient's demographics, pre-operative risk factors, complications of surgery and discharge status (died in the hospital, discharged alive). This process began in 1993 with a pilot data collection from a few hospitals. Full participation by all 13 cardiac centers began in 1994. This information is forwarded to the Department for data accuracy, validation and analysis. The accuracy of the data was verified by the Peer Review Organization of New Jersey comparing a random sample of cases against medical records. When discrepancies were found between the data and the medical records, the hospitals were asked to produce corroborating medical record documentation of their coding or to recode the cases. A verification against hospital discharge records was also conducted to assure that all cases and deaths were reported. Error trapping and frequency reports were also run several times throughout the data cleaning process and shared with the hospitals for correction.

Computing the Observed Mortality Rates for Hospitals and Surgeons

The observed mortality rate for each hospital and for each surgeon can be easily computed by dividing the number of patients who died in the hospital during or after CABG surgery by the number of patients who underwent CABG surgery (the number who died in the hospital plus the number who were discharged alive). Unfortunately, this number can be very misleading as a measure of hospital or surgeon performance because it does not account for how sick the patients were prior to surgery. If one hospital had considerably sicker patients than another hospital, it would be expected that its mortality rate would be somewhat higher. Consequently, a more fair way of comparing performance of the two hospitals would take into account both their observed mortality rates and a measure of how sick their patients were prior to surgery.

Computing the Predicted Mortality Rates for Hospitals and Surgeons

The measure of how seriously ill each CABG patient is prior to his/her surgery is called the predicted probability of death, and represents the chance that the patient will die during or after surgery but before discharge from the hospital. The predicted probability of death is obtained using a statistical model (called logistic regression) that identifies which of a group of proposed patient risk factors are significantly related to a patient's chance of dying during or after CABG surgery, and then assigns statistical weights to those risk factors. The weights are used in a formula that generates the patient's predicted probability of death.

If a patient's predicted probability of death is .05, this means that it is estimated that there are five chances in 100 (or 1 chance in 20) that the patient will die in the hospital prior to discharge. The estimate of the average risk for all of a hospital's or all of a surgeon's patients is obtained by summing the predicted probabilities of death for all of the patients and dividing by the number of patients. This number, which is called the provider's predicted or expected mortality rate, is an estimate of what the provider's mortality rate would have been if the provider's performance had been identical to the statewide performance for those patients.

The statistical methods used to predict mortality on the basis of the significant risk factors are tested to determine if they are sufficiently accurate in predicting mortality for patients who are extremely ill prior to undergoing the procedure as well as for patients who are relatively healthy. These tests have confirmed that the models are reasonably accurate in predicting how patients of all different risk levels will fare when undergoing coronary bypass surgery.

Computing the Risk-Adjusted Mortality Rate

The risk-adjusted mortality rate represents the best estimate, based on the associated statistical model, of what the provider's mortality rate would have been if the provider had a mix of patients identical to the statewide mix. Thus, the risk-adjusted mortality rate has, to the extent possible, ironed out differences among providers in patient severity of illness, since it arrives at a mortality rate for each provider on an identical group of patients.

Interpreting the Risk-Adjusted Mortality Rate

If the risk-adjusted mortality rate is lower than the statewide mortality rate, the provider has a better performance than the state as a whole; if the risk-adjusted mortality rate is higher than the statewide mortality rate, the provider has a worse performance than the state as a whole.

The risk-adjusted mortality rate is used in this report as a measure of quality of care provided by hospitals and surgeons. However, there are reasons that a provider's risk-adjusted mortality rate may not be indicative of its true quality.

For example, extreme outcome rates may occur due to chance alone. This is particularly true for low- volume providers, for whom very high or very low mortality rates are more likely to occur than for high- volume providers. In order to minimize misinterpretation due to chance variation, coronary bypass surgeon data have been reported only for surgeons who have performed at least 100 operations over the two- year period. Another attempt to prevent misinterpretation of differences caused by chance variation is the use of expected ranges (confidence intervals) in the reported results. The interpretations of those terms are provided later when the data are presented.

Differences in hospital coding of risk factors could be an additional reason that a provider's risk-adjusted rate may not be reflective of quality of care. However, the Department of Health and Senior Services monitors the quality of coded data by reviewing patients' medical records to ascertain the presence of key risk factors. When significant coding problems have been discovered, hospitals have been required to review their CABG cases and number of deaths, and the recoded data have been used in the calculations that appear in this booklet.

Another reason that risk-adjusted rates may be misleading is that overall pre-procedural severity of illness may not be accurately estimated because important risk factors are missing. This is not considered to be an important factor, however, because the New Jersey system contains a large number of risk factors that have been demonstrated to be related to patient mortality in various national and international studies. Also, as mentioned earlier, there are ways of testing the statistical model to confirm that its predictions are accurate, and the tests indicate that the model is an accurate predictor of in- hospital mortality for New Jersey patients.

A final reason why these data may not provide a definitive measure of provider quality of care is that patient mortality is not the only way of measuring quality; for instance, complications of surgery, patient quality of life following surgery, and patient satisfaction are also important markers of quality. Although the risk-adjusted mortality rates presented here may not be a totally accurate depiction of the quality of care, the New Jersey Department of Health and Senior Services feels that this information is a valuable aid in choosing providers for coronary artery bypass graft surgery. Perhaps even more impor- tantly, the Department feels that the information provided here can serve as a guide and an impetus for hospitals and surgeons to improve the quality of care they provide to CABG surgery patients.

Results

1994-1995 Risk Factors for CABG Surgery

The significant pre-operative risk factors for CABG surgery in 1994-1995 in New Jersey are presented in Table 1, along with coefficients for the statistical model, p-values, and odds ratios. The coefficients can be used to compute a given patient's probability of death given the patient's risk factors. The p-values state the level of significance for each of the risk factors in Table 1. Note that the smaller the p- value, the more significant the risk factor is as a predictor of in-hospital mortality. Also, note that the only risk factors used in the statistical model were ones that were highly significant predictors (ie. had p-values of .05 or smaller).

For all risk factors except age and ejection fraction, the odds ratios represent the odds of a patient with the risk factor dying in the hospital divided by the odds of a patient without the risk factor dying in the hospital. Roughly speaking, this is the number of times more likely a patient with the risk factors is to die in the hospital than a patient without the risk factor, all other risk factors being identical. For example, the odds ratio for diabetes is 1.420. This means that a CABG surgery patient with diabetes has odds of dying in the hospital during or after surgery that are 1.420 times the odds of a patient without diabetes, assuming the two patients are identical with respect to the other risk factors presented in Table 1.

For age, the odds ratio represents the number of times more likely a patient of a certain age is to die in the hospital than a patient who is one year younger. For example, a CABG patient of age 63 has odds of dying in the hospital that are 1.061 times the odds of a patient who is 62 with the same other risk factors.

For ejection fraction, the odds ratios are relative to the reference group of patients, which are the patients with an ejection fraction that is 50% or greater or has not been reported. Thus, for example, the odds of a patient with an ejection fraction of less than 29% or "poor" dying in the hospital are 2.516 times the odds of a patient with an ejection fraction greater than 50% dying in the hospital, all other risk factors being the same.

(Note: the ejection fraction is the percentage of blood in the left ventricle that is expelled when it contracts).

Figure 1 shows the number of isolated CABG surgery cases by hospital in 1994-1995.

Table 1: Multivariable Risk Factor Equation for Isolated CABG Hospital Deaths in New Jersey State in 1994-1995.

1994-1995 Hospital and Surgeon Outcomes For CABG Surgery

Table 2 presents the 1994-1995 isolated CABG surgery results for the 13 hospitals in which this procedure was performed in New Jersey. For each hospital, the table contains the number of isolated CABG operations performed in 1994-1995, the number of in-hospital deaths, the observed mortality rate, the expected mortality rate based on the statistical model presented in Table 1, the risk-adjusted mortality rate, and a 95% confidence interval for the risk-adjusted rate.

Table 3 presents the 1994-1995 CABG surgery results for 48 New Jersey surgeons performing at least 100 isolated CABG surgery operations (CABG operations with no other major heart surgery) in at least one hospital during this time period. The table contains, for each hospital and surgeon, the number of isolated CABG operations performed in 1994-1995, the number of in- hospital deaths, the observed mortality rate, the expected mortality rate based on the statistical model presented in Table 1, the risk-adjusted mortality rate, and a 95% confidence interval for the risk-adjusted rate. Note that the results for surgeons who performed fewer than 100 isolated CABG operations in 1994-1995 in one hospital are grouped together and reported as "all others" in the hospital in which the operations were performed.

Definitions of key terms are as follows:

The observed mortality rate (OMR) is the number of observed deaths divided by the number of patients.

The expected mortality rate (EMR) is the sum of the predicted probabilities of death for all patients divided by the total number of patients.

The risk-adjusted mortality rate (RAMR) is the best estimate, based on the statistical model, of what the provider's mortality rate would have been if the provider had a mix of patients identical to the state- wide mix.

Confidence intervals for the risk-adjusted mortality rate indicate which hospitals and surgeons had significantly more or fewer deaths than expected given the risk factors of their patients. Hospitals and surgeons with significantly higher rates than expected after adjusting for risk are those with confidence intervals entirely above the statewide rate. Hospitals and surgeons with significantly lower rates than expected given the severity of illness of their patients before surgery have confidence intervals entirely below the statewide rate. It should be noted that, in general, hospitals with higher volumes have smaller confidence intervals than hospitals with lower volumes.

As demonstrated in Table 2, a total of 14,510 isolated CABG operations were performed in New Jersey in 1994-1995, with an in-hospital mortality rate of 3.75%. Hospital volumes ranged from 123 at the University of Medicine and Dentistry of New Jersey to 1860 at Morristown Memorial Hospital. Observed mortality rates (number of deaths divided by number of patients) ranged from 2.53% to 7.04%, and the predicted mortality rates (a measure of patient pre- operative severity of illness) ranged from 2.74% to 5.03%. Risk-adjusted mortality rates (a measure of hospital performance) ranged from 2.73% to 6.67%.

Two hospitals, Hackensack University Medical Center and Morristown Memorial Hospital, had risk- adjusted mortality rates that were significantly lower than the statewide average rate. One hospital, Newark Beth Israel, had a risk-adjusted mortality rate that was significantly higher than the statewide average rate.

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Table 2: Hospital Observed, Expected and Risk-Adjusted Mortality Rates for Isolated CABG Surgeries in New Jersey State, 1994-1995 (Listed Alphabetically by Hospital)

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FIGURE 2: HOSPITAL RISK-ADJUSTED MORTALITY RATES, 1994-95

Surgeon and Hospital Volumes For Isolated CABG Surgery

For each hospital and for each surgeon performing at least 100 isolated CABG surgery operations in that hospital in 1994-1995, Table 3 presents the total number of isolated CABG operations performed. As in Table 2, surgeons who performed fewer than 100 operations in one hospital are reported in the "All Others" category.

Isolated CABG volumes include patients who undergo CABG surgery with no other major heart surgery during the same admission, and who do not have acute mitral valve regurgitation.

Table 3: Observed, Expected and Risk-Adjusted Mortality Rates for Isolated CABG Surgeries by Hospital and Surgeon in New Jersey State, 1994-1995 (Listed Alphabetically by Hospital and Surgeon)

Hospital/Surgeon	Cases	Deaths	OMR	EMR	RAMR		95% CI for RAMR
Cooper Hospital/University M.C.
Cilley, Jonathan	250	7	2.80	4.47	2.35		(	0.94	,	4.84	)
Delrossi, Anthony	179	6	3.35	4.68	2.68		(	0.98	,	5.84	)
Grosso, Michael	187	3	1.60	3.30	1.82		(	0.37	,	5.33	)
All Others	181	13	7.18	5.00	5.39		(	2.86	,	9.21	)
Total	797	29	3.64	4.36	3.13		(	2.09	,	4.49	)
Deborah Heart and Lung Center
Adkins, Mark	138	4	2.90	2.79	3.90		(	1.05	,	9.98	)
Anderson, William	360	14	3.89	2.54	5.75		(	3.14	,	9.65	)
Laub, Glenn	404	6	1.49	2.94	1.89		(	0.69	,	4.12	)
McGrath, Lynn B.	687	19	2.77	2.72	3.81		(	2.29	,	5.94	)
All Others	87	8	9.20	3.80	9.08	+	(	3.91	,	17.90	)
Total	1,676	51	3.04	2.80	4.08		(	3.04	,	5.36	)
General Hosp. Center at Passiac
Baeza, Oscar	184	11	5.98	4.09	5.48		(	2.73	,	9.80	)
#Goldenberg, Bruce	141	5	3.55	3.83	3.47		(	1.12	,	8.10	)
Kaushik, Raj	150	6	4.00	4.21	3.56		(	1.30	,	7.75	)
Saxena, Amarkanth	211	7	3.32	3.72	3.35		(	1.34	,	6.90	)
All Others	152	7	4.61	3.68	4.70		(	1.88	,	9.68	)
Total	838	36	4.30	3.90	4.13		(	2.89	,	5.72	)
Hackensack University Medical Center
Brenner, William I.	176	6	3.41	5.52	2.31		(	0.85	,	5.04	)
Hutchinson III, John E.	463	19	4.10	4.86	3.16		(	1.90	,	4.94	)
Praeger, Peter I.	494	13	2.63	3.55	2.78		(	1.48	,	4.75	)
Somberg, Eric D.	421	7	1.66	3.25	1.92		(	0.77	,	3.96	)
Total	1,554	45	2.90	4.08	2.66	-	(	1.94	,	3.56	)
Jersey Shore Medical Center
Rajaii-Khorasani, Ahmad	405	23	5.68	4.58	4.65		(	2.95	,	6.98	)
Roberts, Arthur J.	417	15	3.60	3.50	3.86		(	2.16	,	6.36	)
All Others	13	2	15.38	4.63	12.46		(	1.40	,	44.98	)
Total	835	40	4.79	4.04	4.45		(	3.18	,	6.05	)
Morristown Memorial Hospital
Brown, John M. III	293	4	1.37	3.27	1.56		(	0.42	,	4.01	)
Casale, Alfred S.	384	11	2.86	3.66	2.93		(	1.46	,	5.24	)
##McCormick, John R.	143	6	4.20	3.83	4.11		(	1.50	,	8.95	)
Neibart, Richard M.	391	9	2.30	3.51	2.46		(	1.12	,	4.66	)
Parr, Grant V. S.	270	6	2.22	2.96	2.81		(	1.03	,	6.13	)
Wenger, Robert K.	282	9	3.19	3.23	3.71		(	1.69	,	7.03	)
All Others	97	2	2.06	4.69	1.65		(	0.19	,	5.95	)
Total	1,860	47	2.53	3.47	2.73	-	(	2.01	,	3.63	)
Newark Beth Israel Medical Center
Gielchinsky, Isaac	324	21	6.48	5.36	4.53		(	2.80	,	6.93	)
#Hussain, Syed	311	24	7.72	5.18	5.59		(	3.58	,	8.31	)
#Karanam, Ravindra	134	7	5.22	3.73	5.25		(	2.10	,	10.82	)
All Others	169	14	8.28	5.18	6.00		(	3.28	,	10.07	)
Total	938	66	7.04	5.03	5.24	+	(	4.05	,	6.67	)
Our Lady of Lourdes Medical Center
Dipaola, Douglas	255	7	2.75	3.71	2.77		(	1.11	,	5.72	)
Eisen, Morris	123	5	4.07	3.83	3.98		(	1.28	,	9.28	)
Kuchler, Joseph	268	9	3.36	3.82	3.30		(	1.50	,	6.26	)
Manuele, Victor	144	4	2.78	4.53	2.30		(	0.62	,	5.89	)
Mnayarji, Nabil	136	9	6.62	4.53	5.48		(	2.50	,	10.40	)
Nayar, Amrit	200	6	3.00	3.55	3.17		(	1.16	,	6.90	)
Ray, Subhash	138	5	3.62	3.83	3.55		(	1.14	,	8.29	)
Santaspirt, John	216	8	3.70	4.04	3.44		(	1.48	,	6.78	)
All Others	192	12	6.25	4.26	5.51		(	2.84	,	9.62	)
Total	1,672	65	3.89	3.97	3.67		(	2.83	,	4.68	)
Robert Wood Johnson University Hosp.
Hall, Timothy	209	4	1.91	3.32	2.16		(	0.58	,	5.54	)
Krause, Tyrone	248	8	3.23	3.26	3.71		(	1.60	,	7.31	)
Scholz, Peter	203	3	1.48	2.62	2.12		(	0.43	,	6.18	)
Scott, Gregory	419	18	4.30	2.92	5.51		(	3.26	,	8.70	)
Spotnitz, Alan	300	9	3.00	2.86	3.94		(	1.80	,	7.48	)
All Others	21	0	0.00	3.26	0.00		(	0.00	,	20.06	)
Total	1,400	42	3.00	2.99	3.76		(	2.71	,	5.09	)
St. Joseph's Hospital/Medical Center
##Bregman, David	107	6	5.61	5.14	4.09		(	1.49	,	8.91	)
Jihayel, Ayad	190	14	7.37	4.30	6.42		(	3.51	,	10.77	)
Mekhjian, Haroutune	554	11	1.99	3.79	1.97	-	(	0.98	,	3.52	)
All Others	94	10	10.64	5.42	7.36		(	3.52	,	13.53	)
Total	945	41	4.34	4.21	3.87		(	2.77	,	5.25	)
St. Michael's Medical Center
##Asher, Alain	158	3	1.90	4.16	1.71		(	0.34	,	5.00	)
Codoyannis, Aristotle	244	7	2.87	3.56	3.02		(	1.21	,	6.22	)
##Seaver, Philip	209	8	3.83	3.65	3.94		(	1.69	,	7.76	)
All Others	263	16	6.08	4.38	5.20		(	2.97	,	8.45	)
Total	874	34	3.89	3.94	3.71		(	2.57	,	5.18	)
The Valley Hospital
#Goldenberg, Bruce	240	11	4.58	3.64	4.72		(	2.35	,	8.44	)
Markovitz, Lawrence	137	5	3.65	2.80	4.88		(	1.57	,	11.40	)
#Mindich, Bruce	621	26	4.19	3.61	4.35		(	2.84	,	6.37	)
Total	998	42	4.21	3.51	4.50		(	3.24	,	6.08	)
UMDNJ/University Hospital
All Others	123	6	4.88	2.74	6.67		(	2.43	,	14.51	)
Total	123	6	4.88	2.74	6.67		(	2.43	,	14.51	)
Statewide Total	14510	544	3.75	3.75	3.75
# Performed operations in another New Jersey State Hospital.
## Performed operations in two or more other New Jersey State Hospitals.
OMR: Observed mortality rate.
EMR: Expected mortality rate.
RAMR: Risk-adjusted mortality rate; RAMR = (OMR/EMR)*Statewide OMR.
+ Risk-adjusted mortality rate significantly higher than statewide rate based on 95 percent confidence interval.
- Risk-adjusted mortality rate significantly lower than statewide rate based on 95 percent confidence interval.
Note: Only surgeons performing 100 or more operations in 1994-1995 at the hospital identified are listed by name. Source: New Jersey Open Heart Surgery Database, 1994-1995.

FIGURE 3: SURGEON RISK-ADJUSTED MORTALITY RATES, 1994-95

Medical Terminology

angina pectoris - the pain or discomfort felt when blood and oxygen flow to the heart are impeded by blockage in the coronary arteries. Can also be caused by an arterial spasm.

arteriosclerosis - the group of diseases characterized by thickening and loss of elasticity of the arterial walls, popularly called "hardening of the arteries". Also called atherosclerotic coronary artery disease or coronary artery disease.

atherosclerosis - one form of arteriosclerosis in which plaques or fatty deposits form in the inner layer of the arteries.

double, triple, quadruple bypass- the average number of bypass grafts created during coronary artery bypass graft surgery is three or four. Generally, all significantly blocked arteries are bypassed unless they enter areas of the heart that are permanently damaged by previous heart attacks. Five or more bypasses are occasionally created. Multiple bypasses are often performed to provide several alternate routes for the blood flow and to improve the long-term success of the procedure, not necessarily because the patient's condition is more severe.

cardiac catheterization - also known as coronary angiography - a procedure for diagnosing the condition of the heart and the arteries connecting to it. A thin tube threaded through an artery to the heart releases a dye, which allows doctors to observe blockages with an x- ray camera. This procedure is required before coronary bypass surgery.

cardiovascular disease - disease of the heart and blood vessels, the most common form of which is coronary artery disease.

coronary arteries - the arteries that supply the heart muscle with blood. When they are narrowed or blocked, blood and oxygen cannot flow freely to the heart muscle or myocardium.

ischemic heart disease (ischemia) - heart disease that occurs as a result of inadequate blood supply to the heart muscle or myocardium.

myocardial infarction - partial destruction of the heart muscle due to interrupted blood supply, also called a heart attack or coronary thrombosis.

plaque - also called atheroma, this is the fatty deposit in the coronary artery that can block blood flow.

risk factors for heart disease - certain risk factors have been found to increase the likelihood of developing heart disease. Some are controllable or avoidable, and some cannot be controlled. The biggest heart disease risk factors are heredity, gender, and age, all of which cannot be controlled. Men are much more likely to develop heart disease than women before the age of 55, although it is the number one killer of both men and women. The risk increases with age, so that half of all cases are in those who are over 75 years old.

Some controllable risk factors that contribute to a higher likelihood of developing coronary artery disease are high cholesterol levels, cigarette smoking, high blood pressure (hypertension), obesity, a sedentary lifestyle or lack of exercise, diabetes, and stress or Type A personality characteristics.

stenosis - the narrowing of an artery due to blockage. Restenosis is when the narrowing recurs after surgery.