Edward V. Bennett

Do Hospitals and Surgeons With Higher Coronary Artery Bypass Graft Surgery Volumes Still Have Lower Risk-Adjusted Mortality Rates?

Background—Studies that are the basis of recommended volume thresholds for CABG surgery are outdated and not reflective of recent advances in the field. This study examines both hospital and surgeon volume-mortality relations for CABG surgery through the use of a population-based clinical data set. Methods and Results—Data from New York’s clinical CABG surgery registry from 1997 to 1999 (total number of procedures, 57 150) were used to examine the individual and combined impact of annual hospital volume and annual surgeon volume on in-hospital mortality rates after adjusting for differences in severity of illness. Significantly lower risk-adjusted mortality rates occurred above all annual hospital volume thresholds between 200 and 800 and above all surgeon volume thresholds between 50 and 200. The number needed to treat (NNT) at higher-volume providers to avoid a death was minimized for a hospital threshold volume of 100 (NNT=50) and a surgeon threshold volume of 50 (NNT=118). The risk-adjusted mortality rate (RAMR) for patients undergoing surgery performed by surgeons with volumes of ≥125 in hospitals with volumes of ≥600 was 1.89%. The RAMR was significantly higher (2.67%) for patients undergoing surgery performed by surgeons with volumes of <125 in hospitals with volumes of <600. Conclusions—Higher-volume surgeons and hospitals continue to have lower risk-adjusted mortality rates, and patients undergoing surgery performed by higher-volume surgeons in higher-volume hospitals have the lowest mortality rates.

Is the Impact of Hospital and Surgeon Volumes on the In-Hospital Mortality Rate for Coronary Artery Bypass Graft Surgery Limited to Patients at High Risk?

Background—Restriction of volume-based referral for CABG surgery to high-risk patients has been suggested, and earlier studies have reached different conclusions regarding volume-based referral for low-risk patients. Methods and Results—Patients who underwent isolated CABG surgery in New York from 1997 through 1999 (n=57 150) were separated into low-risk and moderate-to-high-risk groups with a predicted probability of in-hospital death of 2% as the cutoff point. The provider volume-mortality relationship was examined for both groups. For annual hospital volume thresholds between 200 and 600 cases, the adjusted ORs of in-hospital mortality for high-volume to low-volume hospitals ranged from 0.45 to 0.77 and were all significant for the low-risk group; for the moderate-to-high-risk group, ORs ranged from 0.62 to 0.91, and most were significant. The number needed to treat at higher-volume hospitals to avoid 1 death was greater for the low-risk group (a range of 114 to 446 versus 37 to 184). As the annual surgeon volume threshold increased from 50 to 150 cases, the ORs for high- to low-volume surgeons increased from 0.43 to 0.74 for the low-risk group; for the moderate-to-high-risk group, ORs ranged from 0.79 to 0.86. Compared with patients treated by surgeons with volumes of <125 in hospitals with volumes of <600, patients treated by higher-volume surgeons in higher-volume hospitals had a significantly lower risk of death; in particular, the OR was 0.52 for the low-risk group. Conclusions—For both low-risk and moderate-to-high-risk patients, higher provider volume is associated with lower risk of death.

Comparison of flow differences among venous cannulas.

1. Double caval cannulas with snares provide maximum venous decompression, especially of the superior vena cava. Decompression of the right side of the heart is passive and in the heart being perfused requires venting of the right atrium by release of tapes or atrial suction. 2. Double caval cannulas without snares provide good and consistent venous and atrial decompression. The ventricle is decompressed well except when the perfused heart is in the circumflex position. 3. A large single cannula (e.g., USCI 40F) can decompress both the venous system and right side of the heart, although venous and atrial drainage are much less efficient when the heart is in the circumflex position. 4. The Sarns 51F cavoatrial cannula decompressed the venous system as efficiently as the double caval cannulas. In fact, decompression of the atrium and ventricle were consistently much better with the cavoatrial cannula than with any of the other methods. 5. Efficient venous and myocardial decompression using the 51F cavoatrial cannula requires the atrial drainage ports to be positioned in the upper middle section of the atrium. Clinically, the cannula position is correct when both the single and double marking bands on the cannula are outside the atrium.

Myocardial Preservation: Effect of Venous Drainage

We compared the effect of three methods of venous drainage on myocardial temperature, coronary blood flow as determined with radioactive microspheres, myocardial metabolites (lactate, adenosine triphosphate [ATP], and glycogen), and left ventricular function before, during, and after cardiopulmonary bypass with hypothermic, hyperkalemic cardioplegic arrest. Venous drainage was established in the 6 dogs in Group 1 using a Sarns 51F cavoatrial catheter, in the 7 dogs in Group 2 using two USCI 32F vena caval catheters with tourniquets, and in the 7 dogs in Group 3 using two USCI 32F vena caval catheters without tourniquets. The lowest myocardial temperature was achieved in Group 1 (7.26 degrees +/- 0.45 degrees C compared with 10.45 degrees +/- 0.56 degrees C in Group 2 and 9.78 degrees +/- 0.43 degrees C in Group 3) (p less than 0.001). Myocardial rewarming to 20 degrees C was not significantly different among the groups. Myocardial ATP and lactate levels were similar in all three groups. Myocardial glycogen levels were maintained during ischemia in Group 1 (1,010 +/- 76 mg/dl compared with 686 +/- 39 mg/dl in Group 2) (p less than 0.005). Myocardial blood flow was similar in all groups during the preischemic periods, but during reperfusion a markedly decreased flow was seen in all areas of the myocardium in Group 1 compared with Group 2 (p less than 0.004). Left ventricular function, as measured by the maximum rate of rise of left ventricular pressure, stroke work, and pressure/volume curves, was similar in all groups. We interpret the postischemic blood flow data, glycogen levels, and ventricular compliance differences to suggest that the dogs in Group 1 had less ischemia.

The Human Tumor Clonogenic Assay in the Treatment of Patients with Lung Cancer

The human tumor clonogenic assay has allowed the growth of human tumor cells and their testing to chemotherapeutic agents in vitro in a manner much like bacterial antibiotic sensitivities. This report deals with the in vitro test results compared with the in vivo therapeutic sensitivities of human lung cancer. Three hundred twenty-six lung tumor specimens from either primary or metastatic disease were plated using a two-layer technique. Of these, 68% (223) were grown and 41% (133) were applicable to chemosensitivity testing. Only 28 patients were considered for a retrospective analysis of in vitro tumor sensitivity versus in vivo tumor response to chemotherapeutic agents. Among them the percentage of true positives for the assay was 60%, while the percentage of true negatives was 91%. This technique has been encouraging in its initial stages and, with further development, may have an expanding role in the treatment of patients with lung cancer.

Comparison of Roller Pump versus Pressurized Bag Administration of Potassium Cardioplegic Solution

We sought to determine the relative efficacy of administering cardioplegia by the pressurized bag versus roller pump technique. Fourteen dogs were placed on cardiopulmonary bypass at 30 degrees C and subjected to 2 hours of cardioplegic arrest. Group 1 (7 dogs) was administered cardioplegic solution from a plastic bag under pressure into the ascending aorta every 20 minutes for the 2-hour period, and Group 2 (7 dogs) was given cardioplegia by means of a roller pump. Myocardial temperature decreased in Group 1 to 13.4 degrees C following administration of the cardioplegic solution, and to 13.1 degrees C in Group 2 (not significant). These temperatures were reached in 3.0 minutes in Group 1 and 1.9 minutes in Group 2 (p less than 0.03). Aortic root pressures during cardioplegic infusion were 31 +/- 2 mm Hg in Group 1 versus 46 +/- 2 mm Hg in Group 2 (p less than 0.01). No significant differences between groups were noted in myocardial distribution of cardioplegia, myocardial blood flow or metabolism, or left ventricular hemodynamics. We conclude that both methods of administering cardioplegia lowered myocardial temperature adequately and protected the myocardium for a period of 2 hours in these normal hearts. The roller pump method facilitated faster cooling and produced significantly higher aortic perfusion pressures, however, which may be important in hearts with coronary stenosis.

Porcine Valve Bioprosthesis: Early Thrombosis with Systemic Emboli

Abstract We report the case of a patient who had early postoperative thrombosis, with systemic emboli, of an aortic Hancock porcine valve bioprosthesis. Anticoagulants were not used postoperatively because the patient had a history of epistaxis. Progressive symptoms and a 57 mm Hg transvalvular gradient prompted reoperation at six months. Thrombosis of the valve may have been related to postoperative low cardiac output, prolonged dysrhythmias, or lack of anticoagulants.