Unspecific elevation of plasma troponin-T and CK-MB after coronary surgery

Evaluation of left ventricular diastolic function in patients operated for aortic stenosis

Background

Left ventricular diastolic dysfunction is common in patients with aortic valve stenosis (AS) and reportedly affects prognosis after surgical aortic valve replacement (SAVR). Here we investigated whether and how diastolic function (assessed following the most recent guidelines) was affected by SAVR, and whether preoperative diastolic function affected postoperative outcome. We also examined whether long-term mortality was associated with preoperative NT-proBNP and postoperative heart failure (PHF).

Methods

We performed a prospective observational study of 273 patients with AS who underwent AVR with or without concomitant coronary artery bypass surgery. Of these patients, 247 were eligible for assessment of left ventricular (LV) filling pressure. Preoperatively and at the 6-month postoperative follow-up, we measured N-terminal pro-B type natriuretic peptide (NT-proBNP) in serum and assessed diastolic function with Doppler echocardiography. PHF was diagnosed using prespecified criteria. Multivariable logistic regression was performed to explore variables associated with high LV filling pressure. Cox regression was performed to explore variables associated with mortality, accounting for timeto-event.

Results

At the time of surgery, 22% (n = 54) of patients had diastolic dysfunction expressed as high LV filling pressure. Of these 54 patients, 27 (50%) showed postoperative diastolic function improvement. Among the 193 patients with preoperative low LV filling pressure, 24 (12%) showed postoperative diastolic function deterioration. Increased long-term mortality was associated with PHF and high preoperative NT-proBNP, but not with preoperative or postoperative diastolic dysfunction. Cox regression revealed the following independent risk factors for long-term mortality: diabetes, renal dysfunction, preoperative NT-proBNP>960 ng/L, age, and male gender.

Conclusions

Surgery for aortic stenosis improved diastolic function in patients with high LV filling pressure in 50% of the patients. Our results could not confirm the previously suggested role of diastolic dysfunction as a marker for poor long-term survival after SAVR. Our findings showed that both PHF and high preoperative NT-proBNP were associated with long-term mortality.

The impact of glutamate infusion on postoperative NT-proBNP in patients undergoing coronary artery bypass surgery: a randomized study

Background

Glutamate, a key intermediate in myocardial metabolism, may enhance myocardial recovery after ischemia and possibly reduce the incidence and severity of postoperative heart failure in coronary artery bypass surgery (CABG). N-terminal pro-B-type natriuretic peptide (NT-proBNP) can be used to assess postoperative heart failure (PHF) after CABG. Our hypothesis was that glutamate enhances myocardial recovery in post-ischemic heart failure and, therefore, will be accompanied by a mitigated postoperative increase of NT-proBNP.

Methods

Substudy of the GLUTAmate for Metabolic Intervention in Coronary Surgery (GLUTAMICS) trial (ClinicalTrials.gov Identifier: NCT00489827) a prospective triple-center double-blind randomized clinical trial on 399 patients undergoing CABG with or without concomitant procedure for acute coronary syndrome at three Swedish Cardiac Surgery centres (Linköping, Örebro, and Karlskrona) from May 30, 2007 to November 12, 2009. Patients were randomly assigned to intravenous infusion of 0.125 M l-glutamic acid or saline (1.65 mL/kg of body weight per hour) intraoperatively and postoperatively. Plasma NT-proBNP was measured preoperatively, the first (POD1) and third postoperative morning (POD3). A Clinical Endpoints Committee, blinded to both intervention and NT-proBNP used prespecified criteria to diagnose PHF. The primary endpoints were the absolute levels of postoperative NT-proBNP and the difference between preoperative and postoperative levels of NT-proBNP.

Results

Overall no significant difference was detected in postoperative NT-proBNP levels between groups. However, in high-risk patients (upper quartile of EuroSCORE II ≥ 4.15; glutamate group n = 56; control group n = 45) glutamate was associated with significantly lower postoperative increase of NT-proBNP (POD3-Pre: 3900 [2995–6260] vs. 6745 [3455–12,687] ng•L⁻¹, p = 0.012) and lower NT-proBNP POD3 (POD3: 4845 [3426–7423] vs. 8430 [5370–14,100] ng•L⁻¹, p = 0.001). After adjusting for significant differences in preoperative demographics, NT-proBNP POD3 in the glutamate group was 0.62 times of that in the control group (p = 0.002). Patients in the glutamate group also had shorter ICU stay (21 [19–26] vs. 25 [22–46] h, p = 0.025) and less signs of myocardial injury (Troponin T POD3 (300 [170–500] vs. 560 [210–910] ng•L⁻¹, p = 0.025).

Conclusions

Post hoc analysis of postoperative NT-proBNP suggests that intravenous infusion of glutamate may prevent or mitigate myocardial dysfunction in high-risk patients undergoing CABG. Further studies are necessary to confirm these findings.

Trial registration Swedish Medical Products Agency 151:2003/70403 (prospectively registered with amendment about this substudy filed March 17, 2007). ClinicalTrials.gov Identifier: NCT00489827 (retrospectively registered) https://clinicaltrials.gov/ct2/show/NCT00489827?term=glutamics&draw=1&rank=1

The relationship between ASAT, CKMB, Troponin-T and mortality after cardiac surgery

OBJECTIVE

To investigate the relationship between ASAT, CKMB, troponin-T and mortality after cardiac surgery.

DESIGN

ASAT, CKMB and TnT were analysed in 116 patients. Correlation, sensitivity, specificity and predictive values for permanent myocardial injury (defined as TnT > or = 2.0 microg/l postoperative day four) were calculated. In the second part our clinical protocol (ASAT on postoperative day 1 and TnT on day 3-4 in patients with ASAT above 2.5 microkat/l) was evaluated. Mortality was compared between patients with ASAT < 2.5 microkat/l (ASAT-), 2. ASAT > or = 2.5 microkat/l and TnT < 2.0 microg/l (ASAT+/TnT-) and 3. ASAT > or = 2.5 microkat/l and TnT > or = 2.0 microg/l (ASAT+/TnT+).

RESULTS

Both ASAT and CKMB had irrespectively of cut-off level, low positive and high negative predictive value of permanent myocardial injury. Early and mid-term mortality did not differ significantly between ASAT- and ASAT+/TnT- patients.

CONCLUSIONS

ASAT and CKMB can be used to exclude but not to diagnose permanent myocardial injury after cardiac surgery. Increased postoperative ASAT in the absence of increased TnT is not associated with worse clinical outcome than after normal postoperative ASAT.

Biochemical injury markers and mortality after coronary artery bypass grafting: a systematic review

The strength of the association between cardiac biomarker release and prognosis is uncertain. We performed a systematic literature search to find articles regarding these markers and death after coronary surgical interventions, and evaluated the results with meta-analytic methods. We found 23 articles concerning 29,483 patients that reported the MB fraction of creatine kinase (CK-MB) and troponin T and I. Heterogeneity of existing studies prevented the pooling of the results of troponin studies. The pooled data of the CK-MB studies suggest that after coronary artery bypass grafting, CK-MB release of more than five to eight times the upper limit of the reference range is associated with an increased risk of death during the next 40 months.