Myocardial rewarming mirrors intraoperative mammary artery graft function

BACKGROUND

The internal mammary artery (IMA) bypass graft provides a satisfactorily long-lasting blood supply to the myocardium. However, its initial flow capacity can be insufficient with subsequent regional myocardial ischemia. We evaluated a method to assess the IMA graft function intraoperatively.

METHODS

Twenty-five patients with three-vessel coronary artery disease underwent coronary artery bypass grafting on cardiopulmonary bypass. The in situ IMA was grafted to the left anterior descending coronary artery (LAD) in combination with two saphenous vein grafts to the left circumflex and right coronary artery. Distal anastomoses were performed during cold intermittent blood cardioplegia. After unclamping of the aorta and of the grafted IMA, the temperature at the cardiac anterior and posterior side was measured during the first 5 minutes of warm reperfusion.

RESULTS

A sufficient IMA graft function was expressed by a typical rise in temperature: the cardiac anterior and posterior sides showed a parabolic and exponential course, respectively. The rewarming velocity expressed as the first derivative of temperature over time led to a sharp and early peak for the anterior side, and a smaller and delayed peak for the posterior side. Insufficient IMA graft function could be recognized by an atypical temperature course.

CONCLUSIONS

Temperature measurement of the heart during warm reperfusion after hypothermic cardioplegia can help to assess the effectiveness of the IMA-LAD graft function.

[Coronary artery bypass grafting in patients with highly impaired ventricular function. Long-term outcome]

BACKGROUND AND OBJECTIVE

Left ventricular function is the most important predictor of survival in patients with coronary artery disease. It is also an important indicator for hospital mortality after operation for end-stage coronary artery disease. In our study we investigated, how preoperative ventricular dysfunction influences long term survival after coronary bypass surgery.

PATIENTS AND METHODS

Between 4/1986 and 12/2000, 1751 patients (1440 men/311 women) with left ventricular ejection fraction (LVEF) 10-30% underwent coronary bypass grafting (CABG) at the Deutsches Herzzentrum Berlin. The age of the patients was calculated to an average of 59,2 years. The prime criterion for CABG was ischemia ("hibernating myocardium") diagnosed by myocardial scintigraphy, echocardiography and in some cases with magnetic resonance imaging and positron emission tomography.

RESULTS

Operative mortality for the group was 7,1%. The actuarial survival rate was 87,6% after 2 years, 76,0% after 5, and 53,3% after 9. 455 had LVEF 10-20%, in these actuarial survival was 79,8% after 2 years, 63,0% after 5 and 45,7% after 9 years.

CONCLUSION

We conclude that CABG can be used successfully to improve life expectancy of patients with end-stage coronary artery disease. CABG leads to acceptable prognosis for these high-risk patients when the myocardium is preoperatively identified as being viable.

Prognosis after the implantation of an intra-aortic balloon pump in cardiac surgery calculated with a new score

BACKGROUND

Over the past decade, the use of a ventricular-assist device (VAD) in patients with postcardiotomy cardiogenic shock has resulted in hospital discharge rates of 25% to 40% and is improving. Nevertheless, indications for and timing of the implantation of a VAD in patients who have received an intra-aortic balloon pump (IABP) remain unclear.

METHODS AND RESULTS

From July 1996 to March 2000, 391 patients with cardiac low-output syndrome who underwent open-heart surgery and had an IABP implanted were analyzed in a retrospective pilot study. The perioperative mortality was 34% (133 patients). Clinical parameters were analyzed 1 hour after IABP support began. Statistical multivariate analysis showed that patients with an adrenaline requirement higher than 0.5 microg x kg(-1) x min(-1), a left atrial pressure >15 mm Hg, urine output <100 mL/h, and mixed venous saturation (SVO(2)) <60% had poor outcomes. Using this data, we developed an IABP score (0 to 5 points) to predict survival early after IABP implantation in cardiac surgery. We evaluated our score by monitoring another 101 patients as a control group prospectively. Additionally, 210 patients who received coronary artery bypass grafting (CABG) exclusively were analyzed. All investigations confirmed the validity of the score.

CONCLUSIONS

The IABP score can predict survival early after IABP implantation. In patients with a high IABP score, implantation of a VAD should be considered.

Risk stratification scores for predicting mortality in coronary artery bypass surgery

BACKGROUND

Four risk-stratification scores (RSSs - Euro, French, CCS/Higgins, Parsonnet) were tested as predictors of mortality in coronary artery bypass grafting (CABG) surgery.

METHODS

From March to April 2000, the perioperative courses of 245 consecutive CABG patients were compared to the predictions according to the RSSs. Sensitivity and specificity were determined with receiver operating characteristics (ROC) curves.

RESULTS

CCS/Higgins uses the most easily acquired patient data, and rates emergency conditions as high-risk. Euro focuses on advanced age and septal rupture. French uses the smallest number of patient parameters and rates rare critical situations as high-risk. Parsonnet is partially based on the physician's subjective assessment of a "catastrophic state," making the scoring arbitrary. All RSSs gave similar (not significant) areas under the ROC curves regarding mortality (Euro 0.826 +/- 0.080, French 0.783 +/- 0.094, CCS/Higgins 0.820 +/- 0.060, Parsonnet 0.831 +/- 0.042). Predicted risk levels for the 11 patients who died differed between the RSSs--Higgins placed these patients in 3 of 5 risk levels with ascending distribution. The other RSSs placed these patients in the highest risk level except for one and two patients, respectively, who were placed in the lowest Euro and French risk level. Euro and Parsonnet placed about half of all patients with non-lethal outcome in the highest risk level.

CONCLUSIONS

All RSSs satisfactorily estimated the group risk for mortality. No RSS expressed sufficient validity to predict individuals with lethal outcome. In clinical use, CCS/Higgins proved the most practicable.

Factors influencing results and outcome after transmyocardial laser revascularization

BACKGROUND

Transmyocardial laser revascularization (TMR) has been increasingly used during the recent past for patients with diffuse coronary artery disease. Because this operation is associated with significant morbidity and mortality, it is important to select patients for TMR who are likely to benefit from the procedure.

METHODS

We performed an univariate logistic regression analysis of 20 factors on the benefits and outcomes of 134 patients who underwent isolated TMR at our institution between November 1994 and May 2000.

RESULTS

Responders and nonresponders differed significantly with regard to the incidence of diabetes mellitus. For diabetic patients the chance of profiting from the TMR operation was only 43% of that of nondiabetic patients (odds ratio = 0.43 [0.20 to 0.92]). Furthermore, patients with a preoperative body mass index of less than 25 had a threefold increase in the probability of death during the first year after TMR as compared to patients whose body mass index was 25 or more (odds ratio = 2.97 [1.05 to 8.40]). The incidence of diabetes was also slightly but not significantly different between 1-year survivors and nonsurvivors.

CONCLUSIONS

In diabetic patients we recommend caution in selecting therapeutic TMR because outcomes are less satisfactory than in nondiabetics. Furthermore, patients with a body mass index below 25 have a significantly higher risk for death during the first postoperative year. Studies based on larger patient populations should follow.

[Long-term follow-up after direct intramyocardial implantation of an internal thoracic artery pedicle (Vineberg operation)]

We report on a patient with coronary artery 3-vessel disease who presented 30 years after a unilateral Vineberg operation with a patent graft. The patient successfully underwent coronary artery bypass grafting. The theoretical basis, operative variations and the results of this historical indirect revascularization procedure are briefly discussed.

Extent of myocardial tissue damage during transmyocardial laser revascularization with the CO2 Heart Laser

OBJECTIVE AND BACKGROUND

Transmyocardial laser revascularization (TMR) is the only surgical treatment for patients with severe diffuse coronary artery disease, who are not candidates for bypass grafting or percutaneous angioplasty. However, vaporization of tissue during the creation of channels leads to a certain loss of viable myocardium during every TMR procedure.

METHODS

We analyzed serum levels of creatine kinase and creatine kinase MB subtype in 163 patients after sole TMR with a CO2 laser (wave length 10.6 microm, 800-watt power). The control group consisted of 35 consecutive CABG patients and 30 consecutive redo-CABG patients. Additionally, in the TMR group we measured echocardiographically the left ventricular ejection fraction before and after TMR. We recorded the total amount of laser energy applied, average and maximum energy per channel, and the number of created channels, in order to calculate the correlation between these parameters and postoperative enzyme levels or changes in the LVEF.

RESULTS

After TMR, we measured higher creatine kinase levels compared to those in CABG patients (607.8+/-558.4 U/L vs. 285.0+/-292.3 U/L, p < 0.01). The relative proportion of CK-MB of total CK, however, was significantly lower after TMR, compared to that of the control group (4.5+/-3.0% vs. 10.1+/-6.4%, p < 0.01). Patients with a pronounced postoperative increase in CK-MB levels or a higher percentage of CK-MB of total CK also after TMR operations show a decline in left ventricular contractility. In the laser group, the maximum enzyme levels were detected significantly later than in the control group (25.0+/-19.4 h postoperatively vs. 8.7+/-9.1 h, p < 0.01). There was no significant correlation between the technical laser parameters or the number of created channels and the percentage of CK-MB of total CK or changes in left ventricular ejection fraction.

CONCLUSIONS

CO2 laser TMR does not result in significant injury to the myocardium. Cardiac enzymes play an important role in the detection of perioperative myocardial infarction in TMR patients.

Risk scores currently used in German heart surgery

BACKGROUND

Risk scores (RS) in heart surgery assess mortality and morbidity and mirror the degree of severity of disease of the patients when presented for surgery. We examined the use and dissemination of RS in Germany.

MATERIAL AND METHODS

Our survey included 79 German heart surgery institutes in Fall 1999 and Winter 2000.

RESULTS

Four institutes did not respond. Out of 75 (ad 100 %) responders 56 (75 %) institutes did not use RS, 17 (22 %) institutes used one RS method and 2 (3 %) institutes used two RS methods. The most frequently applied RS methods were the Cleveland Clinic Score and the Euro Score (n = 7, each) followed by institution-specific, internally developed RS methods (n = 5), Parsonnet's RS (n = 1) and the RS from the STS database (n = 1). Fourteen institutes used RS for internal quality control. Of these, 2 institutes publish their RS data for external quality control. The patient-related individual procedure risk was used in 6 institutes.

CONCLUSIONS

A quarter of the German heart surgery institutes use one or more RS methods. The most commonly used were the Cleveland Clinic Score and the Euro Score, followed by internally developed RS methods. RS methods were most frequently used for internal quality control. The degree of the severity of disease of the patients who presented for surgery could only be compared between a small number of institutes using the same RS.

Transmyocardial laser revascularization in ischemic cardiomyopathy

BACKGROUND

In ischemic cardiomyopathy (left ventricular ejection fraction [LVEF] < or = 30%), myocardial revascularization by coronary artery surgery has better results than heart transplantation, provided there is sufficient ischemic but viable myocardium. The mode of action of transmyocardial laser revascularization (TMR) is still being debated, but if the procedure induces improved myocardial perfusion it could be a "bridge," or alternative, to heart transplantation.

METHODS

We retrospectively analyzed 194 patients, who underwent TMR between July 1997 and October 1999. Patients with TMR as an adjunct to coronary artery surgery (n = 30) and those who did not provide written consent to the procedure (n = 8) were excluded; 126 patients had normal or moderately reduced left ventricular function, and 30 patients with ischemic cardiomyopathy (LVEF < or = 30%) were included.

RESULTS

After 12 months, the Canadian Cardiovascular Society (CCS) score dropped significantly from 3.6 (3 to 4) to 2.4 (1 to 4) and maximum work load increased significantly from 58 W (25 to 100 W) to 73 W (25 to 120 W). However, thallium score and LVEF did not improve significantly (27% [15% to 30%] to 32% [15% to 45%]). Prior to the TMR procedure, all 30 patients had a "low risk" or "medium risk" of death according to the Aaronson classification. The 30-day, 1-year, and 2-year survival rates were 83%, 50%, and 47%, respectively.

CONCLUSIONS

We conclude that TMR in ischemic cardiomyopathy (LVEF < or = 30%) has a perioperative risk comparable to that for heart transplantation, but there is no improvement of myocardial performance or life expectancy. Therefore, TMR cannot be regarded as a "bridge," or alternative, to transplantation. However, in individual cases with contraindications for transplantation the anti-anginal effect may justify use of the procedure.

Predictors of survival 1 hour after implantation of an intra-aortic balloon pump in cardiac surgery

From July 1996 to March 2000, 391 patients with intraoperative cardiac low-output syndrome who underwent surgery with heart-lung bypass and had an intra-aortic balloon pump (IABP) implanted were analyzed in a prospective study. Of these 391 patients, 153 (39%) were operated on in an emergency situation, and 238 (61%) patients had elective surgeries. The perioperative mortality was 34% (133 patients). Clinical parameters were analyzed 1 hour after IABP support began. Statistical multivariate analysis showed that patients with an adrenaline requirement higher than 0.5 microg/kg/min, a left atrial pressure higher than 15 mmHg, output of less than 100 mL/hour, and mixed venous saturation (SvQ2) of less than 60% had poor outcomes. Using this data, we developed an IABP score to predict survival early after IABP implantation in cardiac surgery. We conclude that the success or failure of perioperative IABP support can be predicted early after implantation of the balloon pump. In patients with low-output syndrome despite IABP support, implantation of a ventricular assist system should be considered.

Concept of and preliminary trial protocol for adjuvant treatment of mediastinitis with immunoglobulins after cardiac surgery (ATMI): response to comments and criticism

During the consensus-based process of protocol development external experts were invited to comment on a proposal for a trial protocol on adjuvant immunotreatment of patients with wound infection after median sternotomy (ATMI). Controversies and arguments can be divided into five main areas: 1) rationale and objectives; 2) criteria for patient selection; 3) adjuvant treatment; 4) measures of efficacy; and 5) course and timetable of the study. We present and summarise the experts comments and criticism as well as the result of the final discussion of the study group with respect to these areas.

Thoracic transposition of the greater omentum as an adjunct in the treatment of mediastinitis--pros and cons within the context of a randomised study

Mediastinitis after cardiac surgery is a rare but life-threatening complication. The omentum is particularly well-suited for the treatment of severe sternal wound infections, because it contains large numbers of immunologically active cells that seem to be responsible for the high anti-infective activity of the omentum. The additional transposition of parts of the greater omentum into the thorax was discussed in the development of a protocol for the planned ATMI study, which will investigate the effectiveness of immunoglobulins in the treatment of severe sternal wound infections that require reoperation. We present two different points of view about whether omentopexy should be allowed within the study design.

Contrast media radiography in patients with retrosternal irrigation drainage for severe sternal wound infection

Severe wound infection after open-heart surgery is a potentially life-threatening complication, which is mostly treated by re-operation with debridement, and insertion of closed irrigation drainage. Until now there is no consensus about the appropriate duration of irrigation therapy. Since the retrosternal irrigation cavity is likely to become continually smaller as the infection heals, this study was intended to answer the question, as to whether this process can be made visible by the use of contrast media radiography, and whether this information could be used to determine when an irrigation therapy can safely be discontinued. In 1997, 34 patients suffered from sternal wound healing disturbances which required re-operation at our institution (incidence = 0.97%). During the re-operation, a closed retrosternal irrigation drainage was inserted. Of the 34 patients contrast media radiography examinations were carried out on the first, 4th and 12th postoperative day (POD), which consisted of an antero-posterior x-ray of the chest after contrast media injection through each inlet tube. At POD 4 and 12 in the majority of cases, the retrosternal irrigation cavity became smaller when compared with the previous x-ray examination. Only in three of the non-survivors there was a huge irrigation cavity visible at the 12th POD, which sometimes even included the pleural cavity. We conclude that in patients with mediastinitis treated by insertion of a closed irrigation drainage, the retrosternally irrigated cavity seems to become smaller over the therapeutic course of treatment. This process can be visualized by contrast media radiography. Results from this examination should be included in decision making about the best time for discontinuation of the irrigation therapy.

Transmyocardial laser revascularization in the treatment of end-stage coronary artery disease

Transmyocardial laser revascularization has been used in 171 patients suffering from severe angina pectoris unresponsive to medical therapy at Deutsches Herzzentrum Berlin within the period from 7/1994 to 12/1997. In all patients conventional bypass surgery or PTCA, did not seem to offer the possibility of success. Postoperatively, the majority of the patients experienced a significant decrease in angina and better physical endurance. A statistically significant increase in myocardial perfusion or left ventricular contractility has not been detected. Perioperative mortality after TMR decreased from 8% among the first 40 patients to 2.5% among the 40 patients operated on most recently, with an overall mortality of 7%. The relief of angina symptoms and the improved quality of life after TMR seems to justify the use of the method in patients who presented with urgent indications for CABG surgery, although their coronary vessel status did not seem to promise success for this procedure. However, considering its experimental foundation and long-term effects, it seems that a conclusive assessment of TMR is not yet possible.

Secondary transmyocardial laser revascularization in the treatment of end-stage coronary artery disease

Transmyocardial laser revascularization (TMR) has received more acceptance within the last few years. The vast majority of TMR users report impressive clinical benefits. The underlying mechanism for benefit by TMR, however, remains somewhat unclear. Between July 1994 and September 1997, 165 patients underwent TMR at our institution. In three of our TMR patients after an initial angina-free interval of 1 to 2 years we decided to repeat the laser operation. This article focuses on the three re-TMR patients who underwent a second TMR operation 12 to 14 months after the first one. Two of the three patients are well and experience significantly less angina than preoperatively.

[Histomorphology after transmyocardial laser revascularization]

From 11/1994 to 4/1997 we enrolled 140 patients with diffuse CAD refractory to maximum antianginal therapy who are not candidates for PTCA or CABG for transmyocardial laser revascularisation (TMLR). Of these patients aged 63.5 +/- 15 years, 98 had coronary 3-vessel disease, and the average left ventricular ejection fraction was 44%. Eleven out of these 140 patients died from different reasons (pneumonia, myocardial infarction, septicemia). Seven patients who died between the 1st and 20th postoperative day underwent a postmortem examination with histological analysis of the areas treated by TMLR. On the seven investigated ventricles a total of 220 channels were created. The predominant finding in specimens within five days after TMLR was recently closed channels. Furthermore, a zone of necrosis with an average extension of 500 microns on each side of the channel was evident. Many changes were noticeable in specimens from patients who died two or three weeks after TMLR. Freshly clotted material had been replaced by a granular tissue of variable density. High macrophage and monocyte activity was evident. The extent of this cellular activity could be depicted by staining with a special proliferation marker, such as MiB. On the one hand numerous dividing macrophages were observed, on the other, active fibroblasts indicative for the transformation into scar-like tissue. After staining for type-4-collagen, typical for the basal membrane of capillaries, a large number of stained structures was noticeable in the closed channel lumen. Numerous garlandlike structures became visible under higher magnification. By CD 31 incubation, these structures, were found to be lined with endothelium. Further research will be required to indicate whether the laser channels later are partially or completely open, from where the capillaries are supplied, and whether they even connect to the ventricle lumen. But in conclusion, it seems unlikely, that TMLR follows the mechanism of the amphibian heart.

Histological findings after transmyocardial laser revascularization

In recent time, it has become more and more probable that patients with severe diffuse coronary artery disease, who are not candidates for aortocoronary bypass surgery or percutaneous transluminal coronary angioplasty procedures, can benefit from transmyocardial laser revascularization (TMR). But the underlying principle of TMR still remains unclear. This study reports on a histological analysis of eight patients, in whom a total of 250 channels had been created, who died after TMR. The TMR channels were created by a CO2 laser surrounded by a zone of necrosis with an extent of about 500 microns. In the hearts of patients who died in the early postoperative period (1 to 7 days postoperative), almost all channels were closed by fibrin clots, erythrocytes, and macrophages. There were no obvious connections between the channels and the ventricular cavity. In specimens from patients, who died 2 or more weeks after the procedure, a granular tissue with high macrophage and monocyte activity was observable. Within this tissue, we observed a developing network of capillaries. Otherwise, the tissue filling the channels did not substantially differ from scar tissue. We failed to observe connections between the ventricular cavity and the new capillaries. Whether these vessels within the closed channels have any impact on myocardial perfusion remains unclear, but it seems unlikely that the clinical effects of TMR are based on the principle of the amphibian heart.