Lars-Göran Dahlin

Are electrocardiographic Q-wave criteria reliable for diagnosis of perioperative myocardial infarction after coronary surgery?

OBJECTIVE A major assumption in cardiovascular medicine is that Q-waves on the electrocardiogram indicate major myocardial tissue damage. The appearance of a new Q-wave has therefore been considered the most reliable criterion for diagnosis of perioperative myocardial infarction (PMI) in cardiac surgery. In a study, originally intended to evaluate troponin-T as a marker of PMI, analysis of our data aroused the need to address the reliability of Q-wave criteria for diagnosis of PMI. METHODS In 302 consecutive patients undergoing coronary surgery, Q-wave and other electrocardiogram (ECG) criteria were compared with biochemical markers of myocardial injury and the postoperative course. All ECGs were analysed by a cardiologist blinded to the biochemical analyses and the clinical course. RESULTS The incidence of positive Q-wave criteria was 8.1%. Combined biochemical (CK-MB > or = 70 microg/l) and Q-wave criteria were found in 1.0%. Patients with new Q-waves did not have CK-MB or troponin-T levels significantly different from those without Q-waves. More than 25% of the Q-waves were associated with plasma troponin-T below the reference level (< 0.2 microg/l) on the fourth postoperative day. Q-wave criteria alone did not influence the postoperative course. In contrast, biochemical markers correlated with clinical outcome. CONCLUSIONS The majority of Q-waves appearing after coronary surgery were not associated with major myocardial tissue damage, and according to troponin-T one-fourth of the Q-waves were not associated with myocardial necrosis. Furthermore, the appearance of Q-waves had little influence on short term clinical outcome. Therefore, the use of Q-wave criteria as the gold standard for diagnosis of PMI may have to be questioned.

Collagen-gentamicin implant for prevention of sternal wound infection; long-term follow-up of effectiveness

In a previous randomized controlled trial (LOGIP trial) the addition of local collagen-gentamicin reduced the incidence of postoperative sternal wound infections (SWI) compared with intravenous prophylaxis only. Consequently, the technique with local gentamicin was introduced in clinical routine at the two participating centers. The aim of the present study was to re-evaluate the technique regarding the prophylactic effect against SWI and to detect potential shifts in causative microbiological agents over time. All patients in this prospective two-center study received prophylaxis with application of two collagen-gentamicin sponges between the sternal halves in addition to routine intravenous antibiotics. All patients were followed for 60 days postoperatively. From January 2007 to May 2008, 1359 patients were included. The 60-day incidences of any SWI was 3.7% and of deep SWI 1.5% (1.0% mediastinitis). Both superficial and deep SWI were significantly reduced compared with the previous control group (OR=0.34 for deep SWI, P<0.001). There was no increase in the absolute incidence of aminoglycoside resistant agents. The majority of SWI were caused by coagulase-negative staphylococci (CoNS). The incidence of deep SWI caused by Staphylococcus aureus was 0.07%. The results indicate a maintained effect of the prophylaxis over time without absolute increase in aminoglycoside resistance. (ClinicalTrials.gov NCT00484055).

Wound contamination in cardiac surgery

Objectives: To investigate the degree of bacterial contamination in the sternal wound during cardiac surgery and the sternal skin flora after operation in order to increase our understanding of the pathogenesis of sternal wound infections. Design: Prospective study where cultures were taken peri‐ and postoperatively from sternal wounds and skin. Setting: University Hospital. Patients: 201 cardiac surgery patients. Results: 89% of the patients grew bacteria from the subcutaneous sternal tissue. 98% of the patients showed bacterial growth on the surrounding skin at the end of the operation. We found both commensal and nosocomial bacteria in the sternal wound. These bacteria had different temporal distribution patterns. Coagulase‐negative staphylococci (CoNS) and Propionibacterium acnes (PA) were by far the most prevalent bacteria during and after the operation. Furthermore, 41% of patients had more than 10 000 CFU/pad CoNS on the skin. There was no correlation between length of operation and number of bacteria. Men displayed higher bacterial counts than women on the skin. Conclusion: Skin preparation with ethanol/chlorhexidine is unable to suppress the physiological skin flora for the duration of a heart operation. A decrease of CoNS and PA postoperatively can be caused by competitive recolonisation of commensal and nosocomial bacteria.

Cost effectiveness of local collagen-gentamicin as prophylaxis for sternal wound infections in different risk groups

Objectives. In a randomized trial addition of local collagen-gentamicin in the sternal wound reduced the rate of sternal wound infection (SWI) to about 50% compared to intravenous prophylaxis alone. The aim of the present study was to evaluate the economic rationale for its use in every-day clinical practice. This includes the question whether high-risk groups that may have particular benefit should be identified. Design. For each patient with SWI in the trial the costs attributable to the SWI were calculated. Risk factors for SWI were identified and any heterogeneity of the effect of the prophylaxis examined. Results. The mean cost of a SWI was about 14500 Euros. A cost effectiveness analysis showed that the prophylaxis was cost saving. The positive net balance was even higher in risk groups. Assignment to the control group, overweight, diabetes, younger age, mammarian artery use, left ventricular ejection fraction < 35% and longer operation time were independent risk factors for infection. Conclusion. The addition of local collagen-gentamicin to intravenous antibiotic prophylaxis was dominant, i.e. resulted in both lower costs and fewer wound infections.

Lack of effect of synthetic pericardial substitute on right ventricular function after coronary artery bypass surgery. An echocardiographic and magnetic resonance imaging study.

Abnormal right heart function after cardiac surgery is a well-known finding. Inadequate preservation during the operation and restricted cardiac motion due to pericardial adhesions have been proposed as underlying mechanisms. This study focuses on the impact of a pericardial substitute implantation on right ventricular function, using echocardiography and magnetic resonance imaging. A test group of six patients (mean age 54 years) was examined before surgery, and 4-15 days and 5-9 months after coronary artery bypass surgery, where the pericardium was closed with a biodegradable pericardial patch. A group of 11 patients (mean age 63 years) in whom the pericardium was left open served as controls. Tricuspid annulus motion was markedly decreased, abnormal septal motion was present and decreased systolic to diastolic ratio in the vena cava superior flow was present in all patients in both groups one week after surgery. At the late follow-up, all patients still had decreased tricuspid annulus motion, while 17% of the patients in the test group and 22% of the patients in the control group (ns) demonstrated normal septal motion. We conclude that closing the pericardium with a biodegradable patch does not affect the postoperative changes in right heart function normally seen after open-heart surgery.

Early Identification of Permanent Myocardial Damage after Coronary Surgery is Aided by Repeated Measurements of CK-MB

Objective - ECG diagnosis of myocardial infarction after cardiac surgery is associated with major pitfalls and enzyme diagnosis is interfered by unspecific elevation unrelated to permanent myocardial injury. Sustained release of troponin-T is a marker of permanent myocardial injury if renal function is maintained. However, early identification of perioperative myocardial infarction is desirable and therefore the usefulness of creatine kinase monobasic (CK-MB) kinetics to detect myocardial injury early after coronary surgery was investigated. Design - Two hundred and eighty-six patients undergoing coronary surgery were studied with respect to release of enzymes and troponin-T preoperatively and postoperatively 3 and 8 h after unclamping the aorta, and every morning postoperative days 1-4. Results - CK-MB peak was found at 3 h ( n = 145), 8 h ( n = 103) and 16-20 h after unclamping ( n = 38). Depending on when the CK-MB peak was recorded different demographic and perioperative characteristics were found. A sustained release of troponin-T was characteristic for the group with the CK-MB peak at 16-20 h after unclamping. Conclusion - If CK-MB is measured only once it may be advisable to do it on the first postoperative morning as these measurements provided the best discrimination between patients with and without sustained elevation of troponin-T. However, repeated sampling provides additional information that aids in the early identification of permanent myocardial injury particularly in patients with borderline elevations of CK-MB.

Perioperative myocardial infarction in cardiac surgery--risk factors and consequences. A case control study.

OBJECTIVE The aim of the study was to analyze risk factors and clinical outcome in patients sustaining perioperative myocardial infarction (PMI) after cardiac surgery. DESIGN A retrospective, case control study was conducted, in which 42 patients fulfilling both Q-wave criteria and enzyme criteria for PMI, or autopsy diagnosis, from a cohort of 1147 operated on during the same time period were compared with matched controls. A follow-up by telephone interview was conducted, on average 24 months after the operation. RESULTS Unstable angina, peripheral vascular disease, short stature and low body weight were more prevalent in the PMI group. Intraoperative remarks of poor quality coronary vessels and incomplete revascularization were more frequent in the PMI group; 30-day mortality was 24% in the PMI group vs 0% in the control group (p < 0.01). The postoperative course was more complicated and protracted in the PMI group. At follow-up, the control group managed significantly better with regard to freedom from angina and the need for nitroglycerine. However, 24 of the 30 survivors in the PMI group reported an improved quality of life after surgery. CONCLUSIONS We found that PMI was mainly associated with coronary surgery and that unstable angina was the most important preoperative risk factor for PMI. Poorer conditions for revascularization may explain some of the infarcts and could also contribute to the impaired long-term outcome in the PMI group.Objective- The aim of the study was to analyze risk factors and clinical outcome in patients sustaining perioperative myocardial infarction (PMI) after cardiac surgery. Design- A retrospective, case control study was conducted, in which 42 patients fulfilling both Q-wave criteria and enzyme criteria for PMI, or autopsy diagnosis, from a cohort of 1147 operated on during the same time period were compared with matched controls. A follow-up by telephone interview was conducted, on average 24 months after the operation. Results- Unstable angina, peripheral vascular disease, short stature and low body weight were more prevalent in the PMI group. Intraoperative remarks of poor quality coronary vessels and incomplete revascularization were more frequent in the PMI group; 30-day mortality was 24% in the PMI group vs 0% in the control group (p < 0.01). The postoperative course was more complicated and protracted in the PMI group. At follow-up, the control group managed significantly better with regard to freedom from angina and the need for nitroglycerine. However, 24 of the 30 survivors in the PMI group reported an improved quality of life after surgery. Conclusions- We found that PMI was mainly associated with coronary surgery and that unstable angina was the most important preoperative risk factor for PMI. Poorer conditions for revascularization may explain some of the infarcts and could also contribute to the impaired long-term outcome in the PMI group.

Vectorcardiography is Superior to Conventional ECG for Detection of Myocardial Injury after Coronary Surgery

Objective - The reliability of conventional scalar ECG for diagnosis of perioperative myocardial infarction (PMI) in cardiac surgery has been questioned. For the diagnosis of myocardial infarction in general vectorcardiography (VCG) is superior to ECG. Therefore, the usefulness of conventional VCG and computerized analysis of spatial VCG changes for diagnosis of PMI were studied. Design - VCG registrations were obtained from 218 patients undergoing coronary surgery. The spatial QRS vector loop area of each VCG registration was calculated and the loop area before surgery compared with the loop area after surgery. Conventional VCG criteria for myocardial infarction and set values for loop area reduction were related to sustained elevation of plasma troponin-T and clinical course. Results - Both conventional VCG criteria and spatial changes translated better than Q-waves on scalar ECG into elevation of biochemical markers of myocardial injury and impaired clinical course. Conclusion - VCG appears superior to conventional ECG as regards detection of myocardial injury in coronary surgery. Computerized programs have facilitated the registration and the interpretation of VCG and this methodology deserves further evaluation in cardiac surgery.OBJECTIVE The reliability of conventional scalar ECG for diagnosis of perioperative myocardial infarction (PMI) in cardiac surgery has been questioned. For the diagnosis of myocardial infarction in general vectorcardiography (VCG) is superior to ECG. Therefore, the usefulness of conventional VCG and computerized analysis of spatial VCG changes for diagnosis of PMI were studied. DESIGN VCG registrations were obtained from 218 patients undergoing coronary surgery. The spatial QRS vector loop area of each VCG registration was calculated and the loop area before surgery compared with the loop area after surgery. Conventional VCG criteria for myocardial infarction and set values for loop area reduction were related to sustained elevation of plasma troponin-T and clinical course. RESULTS Both conventional VCG criteria and spatial changes translated better than Q-waves on scalar ECG into elevation of biochemical markers of myocardial injury and impaired clinical course. CONCLUSION VCG appears superior to conventional ECG as regards detection of myocardial injury in coronary surgery. Computerized programs have facilitated the registration and the interpretation of VCG and this methodology deserves further evaluation in cardiac surgery.

Impella Used for Hemostasis by Left Ventricular Unloading, in a Case With Left Ventricular Posterior Wall Rupture

Left ventricle wall rupture is a feared complication in mitral valve surgery. We report a combined mitral valve anuloplasty and coronary artery bypass grafting procedure with severe, life-threatening bleeding complication due to left ventricular posterior wall rupture. The patient was successfully treated with a temporary left ventricular assist device to decompress the left ventricle in an attempt to minimize the bleeding, as the patients condition did not allow standard repair of the left ventricle.

The Linköping experience—ups and downs

This is a brief single‐centre report of experiences regarding different prophylactic measures against sternal wound infection during a period of about 10 years. It illustrates the difficulties associated with evaluating the effect of specific prophylactic methods in the clinical situation. Possible explanations for perceived shifts in the rate of wound infections are discussed.