A model that predicts morbidity and mortality after coronary artery bypass graft surgery.

OBJECTIVES: This study was performed to develop a method for identifying patients at increased risk for morbidity or mortality after coronary artery bypass graft surgery. BACKGROUND: Postoperative morbidity is more common than mortality and is important because of its relation to cost. METHODS: Univariate and forward stepwise logistic regression analysis was used to retrospectively analyze a group of 1,567 consecutive patients who underwent bypass surgery between July 1991 and December 1992. We developed a model that predicted postoperative morbidity or mortality, or both, which was then prospectively validated in a group of 1,235 consecutive patients operated on between January 1993 and April 1994. A clinical risk score was derived from the model to simplify utilization of the data. RESULTS: The following factors, listed in decreasing order of significance, were found to be significant independent predictors: cardiogenic shock, emergency operation, catheterization-induced coronary artery closure, severe left ventricular dysfunction, increasing age, cardiomegaly, peripheral vascular disease, chronic renal insufficiency, diabetes mellitus, low body mass index, female gender, reoperation, anemia, cerebrovascular disease, chronic obstructive pulmonary disease, renal dysfunction, low albumin, elevated blood urea nitrogen, congestive heart failure and atrial arrhythmias. Observed morbidity and mortality for the validation group fell within the 95% confidence interval of that predicted by the model. Costs were closely related to the incidence of postoperative morbidity. CONCLUSIONS: Analysis of preoperative patient variables can predict patients at increased risk for morbidity or mortality, or both, after bypass surgery. Increased morbidity results in higher costs. Different strategies for high and low risk patients should be used in cost reduction efforts.

Right coronary artery-pulmonary artery arteriovenous fistula secondary to open heart surgery.

A patient is described who underwent atrial septal defect repair at age 12 and presented 16 years later with angina. Coronary angiography revealed a right coronary artery to pulmonary artery fistula that had developed at the site of the previous thoracotomy. This is the first report of an acquired fistula of this type developing secondary to trauma associated with open heart surgery. Diagnosis, shunt quantification and treatment are discussed.

Optimism and rehospitalization after coronary artery bypass graft surgery.

OBJECTIVE: To determine whether optimism predicts lower rates of rehospitalization after coronary artery bypass graft surgery for the 6 months after surgery. METHODS: A prospective, inception cohort design was used. The sample consisted of all consenting patients (N=309) from a consecutive series of patients scheduled for elective coronary artery bypass graft surgery at a large, metropolitan hospital in Pittsburgh, Pa. To be eligible, patients could not be scheduled for any other coincidental surgery (eg, valve replacement) and could not be in the cardiac intensive care unit or experiencing angina at the time of the referral. Participants were predominantly men (69.9%) and married (80.3%), and averaged 62.8 years of age. Recruitment occurred between January 1992 and January 1994. RESULTS: Compared with pessimistic persons, optimistic persons were significantly less likely to be rehospitalized for a broad range of aggregated problems (including postsurgical sternal wound infection, angina, myocardial infarction, and the need for another bypass surgery or percutaneous transluminal coronary angioplasty) generally indicative of a poor response to the initial surgery (odds ratio=0.50, 95% confidence interval=0.33- 0.76; P=.001). The effect of optimism was independent of traditional sociodemographic and medical control variables, as well as independent of the effects of self-esteem, depression, and neuroticism. All-cause rehospitalization also tended to be less frequent for optimistic than for pessimistic persons (odds ratio=0.77, 95% confidence interval=0.57-1.05; P=.07). CONCLUSIONS: Optimism predicts a lower rate of rehospitalization after coronary artery bypass graft surgery. Fostering positive expectations may promote better recovery.

Use of nifedipine during cardiac surgery for improved myocardial protection.

The combined results of extended clinical trials conducted in two centers following successful laboratory trials are evaluated. From a population of 4,777 patients who underwent open heart surgery, 205 high-risk patients were selected for study. One hundred seventy patients (3.6 percent) were given nifedipine in cardioplegic solution. The remaining 35 patients served as control subjects and were compared with 39 treated patients in the randomized subset of 74. One third of the patients underwent valve replacement, one quarter underwent coronary artery bypass, and 40 percent underwent combinations of valve replacement, coronary artery bypass, and other procedures. Characteristically, the third group had a 50 percent increase in end-diastolic volumes and low cardiac indexes (1.7 +/- 0.1 liters/minute/m2). Average cross-clamp time was 77 minutes. At one center, an extracellular hyperkalemic-type solution was used to deliver an average dose of 407 +/- 22 micrograms nifedipine per patient. At the other center, a low-sodium hyperkalemic solution was used, and the average nifedipine dose was 476 +/- 22 micrograms. Hemodynamic studies in the randomized subset demonstrated approximately a twofold improvement in the treated group in cardiac index, stroke volume, stroke work index, and pulmonary vascular resistance following cardiopulmonary bypass. The incidence of acute low cardiac output death was 4 percent versus 11 percent in the control group. Survival for all treated patients was 86 percent. It is concluded that the addition of nifedipine reduced the incidence of acute global cardiac failure in the immediate postoperative interval.

Prevention of reperfusional damage from ischemic myocardium.

Reperfusional damage refers to the serious structural, functional, and metabolic derangements commonly observed during restoration of coronary circulation following cardiopulmonary bypass. Damage is believed to result from ischemic injury incurred during aortic cross-clamping and unmasked in the recovery period and/or certain metabolic processes activated during postischemic reperfusion. It has been postulated that reperfusional damage can be minimized or eliminated if normal myocardial metabolic parameters can be maintained or restored before the initiation of reperfusion. Studies have tested a variety of cardioplegic solution compositions and administration modes. However, much controversy exists over the different methods. We have tested the hypothesis that improved myocardial protection during cardioplegia can prevent reperfusional damage and investigated the possibility of achieving optimal myocardial protection. Elective cardiac arrest was induced in isolated perfused rat hearts, under working conditions reported previously. We tested two arresting temperatures (8 degrees C and 28 degrees C), three infusion frequencies (single, double, and multiple dose), and different combinations of cardioplegic additives with demonstrated benefits (glucose, adenosine, creatine, and albumin). Metabolic and hemodynamic functions were used to evaluate the protection of the ischemic myocardium. Glucose (0.5%) and adenosine (1 mmol/L) provided clear benefits under all experimental conditions. Double-dose cardioplegia at 8 degrees C also surpassed the single- and multiple-dose groups. When oxygenated cardioplegic solution containing glucose and adenosine was reinfused for 1 minute after 30 minutes of cross-clamping, no measurable changes were detected after ischemic arrest, as compared with normal hearts. Reperfusional damage was eliminated by this procedure. We concluded that an optimal condition for myocardial preservation during elective cardiac arrest in our model was established.

Internal mammary artery grafting. Clinical results, patency rates, and long-term survival in 833 patients.

This report reviews 833 patients who underwent internal mammary artery grafting alone or with vein grafts between 1968 and 1981. Use of the internal mammary artery was indicated in young or middle-aged patients with the following characteristics: a significant lesion of the proximal left anterior descending artery or its diagonal branch alone (70.1%) or combined with diffuse atherosclerosis (19.9%) or a small caliber (3.4%); absent or unsuitable veins for grafting (5.5%); atherosclerosis or an aneurysm of the ascending aorta (0.6%); and failure of previous vein grafts (0.5%). The left anterior descending artery system was grafted by the left internal mammary artery in 53.2%, and the arterial graft was complimented by vein grafts in 2.6%. In 45.2% of the patients, grafts of the left anterior descending artery by the left internal mammary artery were supplemented by vein grafts to the right coronary artery (23.8%), to the circumflex artery (15.2%), or to both (6.2%). The overall operative mortality was 2.2%. It rose to 16.7% with associated cardiac procedures and to 18.5% in patients who were in New York Heart Association Class IV. If these two high-risk categories of patients are excluded, the perioperative death rate in the remaining 750 was only 0.4%. Of the 815 patients who survived the perioperative period (mean 53.1 months follow-up), 63.1% were relieved of angina and 83.4% were in Class I or II of the New York Heart Association, as compared to 27.4% before the operation. At cardiac recatheterization (mean 18.9 months), 87.9% of the internal mammary artery grafts and 63.3% of the vein grafts were patent (p less than 0.05). The cumulative actuarial 10 year survival rate was 88.6% +/- 1.3%.

The importance of skeletal muscle fiber orientation for dynamic cardiomyoplasty.

Dynamic cardiomyoplasty has been performed clinically to provide a substitute for myocardium, to assist dyskinetic ventricles, and to benefit patients with Chagas disease or dilated cardiomyopathy. Encouraging results have been observed for the patients; however, a conclusive experimental study is not available. How to use conditioned skeletal muscle for maximal augmentation of cardiac function in an appropriate animal model is the goal of this study. Dogs were used for heart failure induction, for single versus burst muscle stimulation, and for cardiac function augmentation. Muscle transformation was documented by histochemical evaluations. Propranolol infusion (3 mg/kg) induced temporary heart failure for 4 to 6 hours with significantly decreased cardiac output and blood pressure. Dynamic cardiomyoplasty significantly improved hemodynamic function during induced heart failure with better improvement by multiple (burst) stimulation as compared with single stimulation. Skeletal muscle fiber orientation is a critical factor for the success of this procedure. Our results indicated that skeletal muscle fiber oriented circumferential to the heart and perpendicular to the ventricular septum is the preferred procedure for dynamic cardiomyoplasty.

Internal mammary artery graft: retrospective report with 17 years' survival.

This report describes one of the earliest cases of successful internal mammary artery grafting. A left internal mammary-right coronary artery titanium stent anastomosis was performed on Jan. 5, 1968, at Allegheny General Hospital. Repeated cardiac catheterization 2 weeks, 6 months, and 6 years after the operation showed a patent anastomosis. The patient survived over 17 years after the operation.

Improved myocardial protection with nifedipine and potassium-based cardioplegia.

Thirty dogs were studied acutely on cardiopulmonary bypass in four groups. Hearts in Groups 1C (standard cardioplegia, n = 5) and 2c (n = 10) were subjected to periods of global ischemia of 1 and 2 hours, respectively. Both groups received 300 cc boluses of hypothermic (4 degrees C), potassium-based cardioplegic solution infused via an 18 gauge needle proximal to the aortic cross-clamp, at every 30 minute interval of ischemia. Groups 1CN (standard cardioplegia plus nifedipine, n = 5) and 2CN (n = 10) were treated similarly, except that nifedipine (5 microgram/kg) was added to each 300 cc bolus of cardioplegic solution. The addition of nifedipine in Groups 1CN and 2CN resulted in statistically significant reduction in myocardial water content (p less than 0.005), mean left atrial pressure (MLAP) (p less than 0.05), and myocardial compliance (p less than 0.005) as compared to the control groups (1C and 2C). Recovery of left ventricular dp/dt in Experimental Group 2CN was also statistically better (p less than 0.025) than in Control Group 2C. Examination of myocardial biopsy tissue by electron microscopy was not conclusive. Nifedipine used in combination with hypothermic, potassium-based cardioplegia provided significant additional myocardial protection over cardioplegia alone.

A new radioisotope-powered cardiac pacer.

A small lighweight nuclear pacer is described. The unit weighs 6) Gm. and occupies a bolume of 33 c.c. It is a standard, R-wave inhibited, demand pacer and has been shown to be insensitive to electromagnetic interference. The unit has met all United States and Foreign Atomic Energy Commission (AEC) safety specification requirements, including cechanical shock, industrial fire, accidental crush, cremation, impact, and corrosion. Its calculated life is in excess of 20 years. Extensive dog testing has been completed and will be described in detail elsewhere. The United States AEC has been issued a license to conduct extensive clinical trials. These began in October 1974, and will be the subject of a later report.

A thirteen-year review of the Magovern-Cromie aortic valve.

A review of 375 cases of aortic valve replacement with the Magovern-Cromie sutureless prosthesis demonstrated a 43 per cent survival rate 10 to 13 years following the operation. Of the 308 patients surviving zero to 30 days, 238 patients are alive after one to 14 years. A total of 70 patients (22 per cent died during the 14 year follow-up period. The actuarial survival rate of all patients at risk was 64 per cent at the fifth year and 51 per cent at the tenth year. For those patients who lived at least one year after surgery, the probability of survival was 84 per cent and 70 per cent at 5 and 10 years, respectively. These results compare favorably with reports of up to only 8 years with the Smeloff-Cutter and Starr-Edwards prostheses. There was only a 1.5 per cent incidence of perivalvular leak with this method of fixation, and no valve has migrated. Ball variance has not occurred with any valve inserted since 1964, and the incidence of thromboembolism with the Model A4 prosthesis is 2.4 per cent. Improvement in results depend on reduction of thromboembolism, lessening of late and operative morality rates, and by earlier operative intervention to reduce the late deaths from cardiogenic factors.

The control of myocardial Ca++ sequestration with nifedipine cardioplegia.

Myocardial 45Ca sequestration was studied in dogs after an injection of 45CaCl2 during 60 minutes of global ischemia and 30 minutes of reperfusion using cardiopulmonary bypass (CPB) at 32 degrees C. Group I (n = 10) received a standard hyperkalemic cardioplegic solution and Group II (n = 10) received the same cardioplegia solution plus nifedipine (100 micrograms/300 cc). After aortic cross-clamping, 300 cc of cardioplegic solution was delivered at 0 and 30 minutes at 4 degrees C. Tissue specific activity (SA = cpm x 10(4)/gm) and plasma specific activity (SA = cpm x 10(4)/ml) were determined before release of the cross-clamp and serially by biopsy during reperfusion. The ratio of tissue SA to plasma SA, termed relative specific activity (RSA), indicates myocardial 45Ca sequestration. Nifedipine led to a marked decrease in sequestration. Group II RSAs were 31.5%, 82.1%, and 39.6% less than Group I RSAs at 0, 20, and 30 minutes of reperfusion. All differences were highly significant (p less than 0.01). During the first 20 minutes of reperfusion, the Group I RSA increased 498% while the Group II RSA increased only 23.8%. A correlation is shown between the decreased calcium sequestration and improved myocardial performance after CPB, demonstrated in previous experiments using nifedipine. Nifedipine in combination with a hypothermic hyperkalemic cardioplegic solution effectively controls myocardial calcium sequestration during 60 minutes of ischemia arrest and the immediate 30 minutes of reperfusion.

Myocardial scintigraphy. Post-Vineberg study.

In order to assess myocardial perfusion of Vineberg implants, tracer particles (99mCc and 131I-MAA) were injected into the internal mammary implants of 7 patients (6 years after the operation) after selective contrast visualization. The myocardial perfusion images were correlated with the internal mammary arteriographic findings. Of those patients with patent implants with communication, the myocardial scintigrams demonstrated even distribution of radioactive particles reflecting myocardial perfusion at the capillary or precapillary bed.

Reversal of pulmonary circulation.

The preliminary results and the technique of total reversal of the pulmonary circulation (RPC) are presented. Total RPC is technically feasible and not incompatible with life. It affords a new experimental model for in vivo study of pulmonary pathophysiology. The influence of this reversal on blood oxygenation, on pulmonary vascular resistance, and on established pulmonary hypertension, as well as its reaction to hypoxia and acidosis, needs further investigation. RPC may have clinical implications in essential pulmonary hypertension and congenital pulmonary vascular anomalies.

Redo cardiac surgery: late bleeding complications from topical thrombin-induced factor V deficiency.

Bovine thrombin-induced factor V deficiency was though to be a very rare acquired coagulopathy, with only three documented cases. We report a series of nine patients seen during a period of 32 months; these patients had normal preoperative coagulation profiles, and this unique coagulopathy developed 1 to 2 weeks after cardiovascular operations. The coagulopathy was characterized by a markedly elevated prothrombin time (40.9 +/- 5.8 seconds), an elevated activated partial thromboplastin time (96.3 +/- 12.2 seconds), a study positive for lupus anticoagulation (9/9), and markedly decreased levels of factor V (0.09 +/- 0.03 U/ml) and factor XI (0.04 +/- 0.02 U/ml), respectively. All patients had been exposed to commercially available bovine thrombin during prior cardiovascular or vascular operations and received a second bovine thrombin challenge during the latest procedure. Coagulopathic bleeding developed in four of the nine patients. Bleeding was unrelated to absolute fall in factor V level, but cessation of hemorrhage appeared to correlate with improvement in factor V level. Treatment with vitamin K, fresh frozen plasma, and platelet infusion were all unsuccessful in altering prothrombin time or factor V levels. Intravenous gamma globulin was used in three patients, two of whom were bleeding. All three patients showed a transient increase in factor V levels. Bleeding stopped in one of the two patients; the other continued to bleed and subsequently died. The third patient was treated prophylactically to increase factor V levels in preparation for flap reconstruction of his sternum. His factor V level increased from 0.26 to 0.49 U/ml, and he underwent the procedure without incident. Bovine thrombin-induced factor V deficiency may have been previously unrecognized. This deficiency should be suspected in patients who have undergone redo cardiovascular operations and in whom marked elevations in their prothrombin time occur 7 to 10 days after exposure to bovine thrombin. The resulting coagulopathy, although usually self-limited, has the potential to produce devastating bleeding complications. Intravenous gamma globulin (1 gm/kg during each of 2 days) has been used to increase factor V levels transiently but its role in therapy of this coagulopathy requires further investigation.

Immunoprofile studies for patients with bronchogenic carcinoma. I. Correlation of pretherapy studies with survival.

The general immune competence of 146 patients with bronchogenic carcinoma was measured, prior to irradiation therapy, by determining dinitrochlorobenzene (DNCB) reactivity, delayed cutaneous hypersensitivity (DCH) response to microbial antigens, peripheral lymphocyte counts, peripheral T and B lymphocyte counts, and the response of patient's lymphocytes to stimulation by phytohemagglutinin (PHA), concanavallin A (Con A) and pokeweed mitogen (PWM). Analyses were performed by the life-table method to determine the correlation of the immune status of these patients with survival rates. Statistically significant differences in survival were noted between the groups of patients with normal values when compared with the patients with abnormal values for the majority of the tests of general immunity. A stage of disease correlation with survival rate was noted for all groups of patients with abnormal immune measurements, but it was absent for many of the immune parameters when patients with normal values were compared. The effects of histology, age, and sex did not appear to influence the survival data as significantly as did the immune status of the patient. These data indicate that measurements of general immune competence may be of significant prognostic value for the management of patients with bronchogenic carcinoma. The measurement of DNCB reactivity shows the strongest correlation with survival rate.

Recovery of the failing canine heart with biventricular support in a previously fatal experimental model.

Prolonged normothermic ischemia in the canine model is generally fatal with standard resuscitative techniques. To determine whether such myocardial injury is recoverable with biventricular support, we subjected 10 dogs to 45 minutes of ischemia at 37 degrees C. After ischemia, the animals were supported for 24 hours with biventricular assist with the centrifugal pump. During early reperfusion, none of the hearts could sustain a stable rhythm or blood pressure. Myocardial adenosine triphosphate concentration, expressed as micromoles per gram of heart protein, was dramatically reduced from a control of 31.5 +/- 2.4 to 14.6 +/- 2.9 (p less than 0.01 versus control), a 54% reduction. Ultrastructural analysis did not reveal the explosive cell swelling of irreversible cell injury. After 12 hours of biventricular assist, developed pressure partially recovered to 60.0 +/- 10 mm Hg (p less than 0.01 versus control) and maximal positive dP/dt measured 2,649 +/- 412 mm Hg/sec (p less than 0.01 versus control). Adenosine triphosphate concentration increased to 25.2 +/- 5.5 (p less than 0.01 versus control). Electron microscopic examination showed less chromatin clumping, no further mitochondrial distortion, and more abundant glycogen. After 24 hours of biventricular assist, cardiac output in the seven dogs successfully weaned from biventricular assist measured 3.6 +/- 0.6 L/min, developed pressure recovered to 76.3 +/- 8.9 mm Hg, and its first derivative recovered to 4,282 +/- 585 mm Hg/sec (all measurements not significant compared with control). Examination by an electron microscope revealed no severe mitochondrial injury.

Left ventricular aneurysmectomy. Factors influencing postoperative results.

One hundred consecutive patients who underwent resection of aneurysms of the left ventricle were reviewed. Eighty-four of these patients had resection or plication of an aneurysm of the anterior left ventricular wall either alone or in combination with coronary artery bypass grafting. In 27 patients who had little or no congestive heart failure, the primary indication for operation was disabling angina pectoris. In them the early mortality was 4% and late mortality, 4%. In nine other patients the primary indication for operation was life-threatening ventricular arrhythmias. In this group the early mortality was 56% and late mortality, 0%. Severe congestive heart failure was the primary indication for aneurysmectomy in 48 patients. In these patients the early mortality was 21% and late mortality, 34%. When the primary indication for operation was severe congestive heart failure, overall survival and postoperative results were best in patients in whom the nonaneurysmal left ventricle had good function preoperatively and was supplied by coronary arteries either unobstructed or favorable for bypass grafting; results were poorest in those patients with three-vessel coronary artery disease who had impaired motion of the lateral left ventricular wall and distal lateral wall vessels that were unfavorable for bypass grafting. It is concluded that patients with left ventricular aneurysms form a heterogeneous group in which the prognosis varies markedly. The probability of a good postoperative result can be predicted by careful preoperative analysis of a patient's symptoms, ventricular function, and coronary artery anatomy.

Direct selective myocardial revascularization by internal mammary artery-coronary vein anastomosis.

In this report, we shall describe our work with retrograde coronary perfusion, first in mongrel dogs and then in 6 patients. The left internal mammary artery (LIMA) is anastomosed to the left anterior descending coronary vein (LADV) to provide myocardial perfusion. This procedure may be of great value in the treatment of patients who are not suitable candidates for direct coronary bypass grafting, i.e., those who have diffuse atherosclerosis, with poor or no runoff of the left anterior descending coronary artery (LADA),but who have satisfactory left ventricular contraction.

Microemboli during coronary artery bypass grafting. Genesis and effect on outcome.

Cerebral dysfunction after coronary artery bypass operations represents some of the most serious and costly complications of cardiac surgery. We used transcranial Doppler ultrasonography to detect and quantify the number of microemboli in the right middle cerebral artery of patients undergoing elective first coronary bypass operations (n = 117) and second coronary bypass operations (n = 10). We hypothesized that total microemboli were related to clinical outcome. A 2 MHz transducer was positioned in front of the ear above the zygomatic arch and depth gated to 50 mm. Microemboli were recorded as perturbations of the blood flow velocity in the middle cerebral artery and aurally monitored. Each episode of microembolism was specified both by clock time and as a perfusion or surgical event. Forty-one patients (32%) completed neuropsychologic evaluation with a battery of tests for cognitive function. Anxiety states and traits were also assessed. The distribution of microembolism showed that there were three groups of patients: < 30 microemboli (n = 83); 30 to 59 (n = 24); and > 60 (n = 20). Seven of 10 patients with cerebral complications (stroke, coma, delirium, aberrant behavior) were in the > 60 microemboli group. Those with cerebral complications had 20.7 +/- 4.5 microemboli from perfusion and 57.4 +/- 15.6 from surgical events. The 13 patients in the > 60 microemboli group without central nervous system symptoms had 95.5 +/- 19.5 microemboli from perfusion and 36.0 +/- 6.9 from surgical events. Neuropsychologic scores were most often depressed for memory (73%), comprehension (49%), attention (46%), and constructional ability (44%). The greatest change was in total score in the > 60 microemboli group (-3.3 +/- 0.6) compared with -1.1 +/- 0.2 and -1.9 +/- 0.2 for the 30 to 59 and < 30 groups, respectively. The incidences of cardiac and pulmonary complications and mortality were different between those patients with < 60 microemboli versus those with > 60 microemboli. Cardiac and pulmonary complications and mortality percentages were 4.7%, 3.7%, and 0.9%, respectively, for the < 60 microemboli group and 20%, 20%, and 15%, respectively, for the > 60 microemboli group. We concluded that transcranial Doppler ultrasonography is a useful technique to quantify and detect the source of microemboli during coronary artery bypass operations and may be useful in assessing new operative strategies, the quality of the perfusion, and potentially as an indicator for pharmacologic therapy in the operating room in patients with high microemboli counts.