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Perioperative myocardial infarction in cardiac surgery: a diagnostic dilemma
Linköping University, Department of Medicine and Care, Thoracic Surgery. Linköping University, Faculty of Health Sciences.
2001 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Perioperative myocardial infarction remains a major cause of morbidity and mortality after cardiac surgery. In spite of this there is no consensus regarding diagnostic criteria and consequently the reported incidence varies widely. In this thesis risk factors for PMI and outcome after PMI were studied in a retrospective case control study on 42 patients fulfilling strict criteria for PM! collected from a cohort of 1147 adult cardiac surgical patients. Traditional diagnostic criteria for PMI, release characteristics of biochemical markers for myocardial injury and VCG were evaluated in a prospective study on 302 consecutive patients undergoing isolated frrst time CABG. PM! was found to be a problem mainly associated with surgery for ischaemic heart disease. Unstable angina and unfavourable conditions for revascularisation were found to be the most important risk factors for PMI. Patients with PM! had an impaired short-term and mid-term outcome compared with controls. In the prospective study a sustained elevation of troponin-T was used as a marker for permanent myocardial damage. It was demonstrated that Q-wave criteria, previously accepted as the gold standard for diagnosis of PM!, correlated poorly with biochemical markers of myocardial injury and clinical outcome. One fourth of the patients with new Q-waves after CABG had no evidence of permanent myocardial injury. The use of biochemical markers for early diagnosis of myocardial injury is interfered by unspecific release unrelated to permanent myocardial damage. However, little is known about the magnitude of this "diagnostic noise". To address this issue a subgroup with no or minimal permanent myocardial damage was identified by use of the unique release characteristics of troponin-T. The time frame of unspecific release and the plasma levels of CKMB and troponin-T caused by unspecific release were assessed. A substantial early release of both CKMB and troponin-T nnrelated to permanent myocardial injury was found. As the unspecific release can be expected to differ depending on type of cardiac intervention this type of knowledge may prevent inappropriate comparisons. Repeated early sampling for CKMB provided additional information of value for early identification of patients who would later show sustained elevation of troponin-T. VCG was found to correlate better with sustained levels oftroponin-T and clinical outcome than scalar ECG. To conclude, diagnostic pitfalls associated with both ECG and enzymatic diagnosis of PM! were addressed and novel approaches to improve detection of permanent myocardial damage are suggested.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2001. , 54 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 668
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-27472Local ID: 12125ISBN: 91-7219-961-X (print)OAI: oai:DiVA.org:liu-27472DiVA: diva2:248024
Public defence
2001-04-20, Berzeliussalen, Universitetssjukhuset, Linköping, 13:15 (Swedish)
Opponent
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-09-06Bibliographically approved
List of papers
1. Perioperative myocardial infarction in cardiac surgery - risk factors and consequences: a case control study
Open this publication in new window or tab >>Perioperative myocardial infarction in cardiac surgery - risk factors and consequences: a case control study
2000 (English)In: Scandinavian Cardiovascular Journal, ISSN 1401-7431, Vol. 34, no 5, 522-527 p.Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-26845 (URN)10.1080/140174300750064710 (DOI)11463 (Local ID)11463 (Archive number)11463 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-09-06Bibliographically approved
2. Are electrocardiographic Q-wave criteria reliable for diagnosis of perioperative myocardial infarction after coronary surgery?
Open this publication in new window or tab >>Are electrocardiographic Q-wave criteria reliable for diagnosis of perioperative myocardial infarction after coronary surgery?
Show others...
1998 (English)In: European Journal of Cardio-Thoracic Surgery, ISSN 1010-7940, E-ISSN 1873-734X, Vol. 13, no 6, 655-661 p.Article in journal (Refereed) Published
Abstract [en]

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≥70 μg/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 μg/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.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-81054 (URN)10.1016/S1010-7940(98)00091-8 (DOI)
Available from: 2012-09-06 Created: 2012-09-06 Last updated: 2017-12-07Bibliographically approved
3. An attempt to quantify the plasma levels of troponin-T and CK-MB after coronary surgery caused by release unrelated to permanent myocardial injury
Open this publication in new window or tab >>An attempt to quantify the plasma levels of troponin-T and CK-MB after coronary surgery caused by release unrelated to permanent myocardial injury
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Background: Release of biochemical markers of myocardial injury unrelated to permanent myocardial damage has been claimed to explain a major proportion of elevations seen after cardiac surgery. However, little is known about the magnitude of this unspecific release. The aim of this study was to shed light on this issue by serial measurements in patients without permanent myocardial injury after coronary surgery.

Methods: The unique release kinetics of troponin-T were employed to identify patients with no or minimal permanent myocardial injury. 302 patients undergoing CABG procedures (employing cardiopuhnonary bypass, crystalloid cardioplegia and retransfusion of shed mediastinal blood) were studied.

Results: 90 patients were found to have normalized troponin-T levels no later than the fourth postoperative day indicating that early elevation of biochemical markers was explained almost purely by unspecific release. In this subgroup troponin-T (2.03±1.36 µg/L; range 0.35-8.99 µg/L) peaked at the 3 hour recording and CK-MB (28.3±10.7 µg/L; range 11.9-86 µg/L) peaked at the 8 hour recording after unclamping the aorta.

Conclusions: A substantial early release of CK-MB and troponin-T occurred in patients with no or minimal permanent myocardial injury after CABG. The time frame when unspecific release was most pronounced is frequently studied to evaluate myocardial protective strategies or to compare different treatment modalities. Also, differences in unspecific release of biochemical markers can be expected depending on type of surgical procedure or coronary intervention. Therefore, further efforts to hring clarity about diagnostic pitfalls are warranted to prevent inappropriate comparisons and to improve our assessment of myocardial damage in association with revascularisation procedures.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-81055 (URN)
Available from: 2012-09-06 Created: 2012-09-06 Last updated: 2012-09-06Bibliographically approved
4. Early Identification of Permanent Myocardial Damage after Coronary Surgery is Aided by Repeated Measurements of CK-MB
Open this publication in new window or tab >>Early Identification of Permanent Myocardial Damage after Coronary Surgery is Aided by Repeated Measurements of CK-MB
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2002 (English)In: Scandinavian Cardiovascular Journal, ISSN 1401-7431, Vol. 36, no 1, 35-40 p.Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-25193 (URN)10.1080/140174302317282366 (DOI)9632 (Local ID)9632 (Archive number)9632 (OAI)
Note

On the day of the defence day the status of this article was submitted.

Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2012-09-06Bibliographically approved
5. Vectorcardiography is Superior to Conventional ECG for Detection of Myocardial Injury after Coronary Surgery
Open this publication in new window or tab >>Vectorcardiography is Superior to Conventional ECG for Detection of Myocardial Injury after Coronary Surgery
Show others...
2001 (English)In: Scandinavian Cardiovascular Journal, ISSN 1401-7431, Vol. 35, no 2, 125-128 p.Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-26844 (URN)10.1080/140174301750164835 (DOI)11462 (Local ID)11462 (Archive number)11462 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-09-06Bibliographically approved

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