Vittorio Mantovani

Monitoring of Extracellular Aspartate Aminotransferase and Troponin T by Microdialysis during and after Cardioplegic Heart Arrest

This study aims at developing per- and postopertive surveillance of the myocardium and focuses on ischemic damage following cardioplegic heart arrest. Levels of troponin T and total aspartate aminotransferase (ASAT) were analyzed in the myocardial interstitium of 10 patients with ischemic heart disease (IHD) who underwent coronary bypass surgery and in 12 patients with nonischemic heart disease (N-IHD) who underwent valvular surgery. Fluid from the myocardial interstitium of the anterior and the lateral wall of the heart was sampled by microdialysis probes that were implanted during surgery and extracted percutaneously 70–100 h later. There were no adverse reactions, and the equipment did not interfere with the surgical procedures. The peak in troponin T serum levels that occurred 4 h after cardiac arrest was preceded by a peak in troponin T levels in the microdialysates from the interstitium that occurred 1 h earlier. The concentration of troponin T in the microdialysate peak was 300 times higher than in the serum peak. The increase in serum ASAT levels during the first 7 h after cardiac arrest corresponded in time with a decrease in interstitial ASAT levels, which had already reached a maximum during cardiac arrest. The microdialysate/serum concentration ratio was considerably smaller for ASAT than for troponin T. Interstitial peak levels of troponin T correlated positively and significantly with peak levels of ASAT. Of the 22 patients, 15 had no postoperative events according to clinical outcome, ECG and serum tests. Fourteen of these had low to normal levels of interstitial ASAT and troponin T. Conversely, atrial fibrillation and/or premature atrial contractions were recorded in 8/22 patients, 7 of whom had elevated interstitial ASAT and/or troponin T concentrations in one or both of the sampled heart regions. The N-IHD patients had higher levels of troponin T in the interstitium 20–70 h following cardioplegia, while the peak levels did not differ between the groups. In conclusion, microdialysis sampling of troponin T and ASAT is safe and allows a highly sensitive analysis of the ischemic trauma exerted by the cardioplegic arrest.

Extracellular Amino Acids as Markers of Myocardial Ischemia during Cardioplegic Heart Arrest

Extracellular levels of amino acids in the myocardial interstitium are sensitive indicators of myocyte function. Lowered ATP leads to a rapid extracellular appearance of amino acids with a high intra- to extracellular concentration ratio, such as taurine and glutamate. Nitrogen fluxes are reflected by glutamine, while alanine, glycine, serine and leucine are markers of proteolysis. In addition, degradation of membrane phospholipids is reflected by other primary amines, such as phosphoethanolamine. The time course of these changes was determined before, during and after cardioplegic heart arrest. Two regions of the heart were monitored in 20 patients by means of microdialysis sampling. After only 20 min of heart arrest, extracellular taurine, glutamate and phosphoethanolamine increased transiently up to 25 times the basal level. Ten–20 min later, glutamine increased by 6 times. A doubling of alanine, glycine, serine and leucine levels took place 30 min after release of the aortic cross-clamp. After 2 h, all were at levels similar to those recorded 15–30 h later. Levels of taurine and glutamate in the anterior wall of the heart correlated significantly with those of its lateral wall. The response to surgery and heart arrest was studied in a group of patients with ischemic heart disease as well as in another group of patients, who underwent heart surgery for nonischemic reasons. The response of taurine and glutamine was significantly higher for the patients with ischemic heart disease, in spite of a shorter mean time of heart arrest. No sex differences were recorded. High levels of amino acids coincided frequently with clinical events, which were suggestive of ischemia, but were also recorded in a few patients without diagnosed events. We conclude that monitoring of extracellular amino acids is valuable for evaluation and development of cardioprotective strategies.

Post-infarction cardiac rupture: surgical treatment

OBJECTIVE Rupture of ventricular free wall (VFWR) may complicate acute myocardial infarction and accounts for high mortality. Surgical repair is the only therapeutic option. A review of our surgical experience is presented. METHODS Seventeen patients (11 men, mean age 68 years) underwent surgery for VFWR. Patch covering technique was used in 13 patients, infarctectomy with patch reconstruction in three patients, direct suture without patch in one patient. Coronary artery bypass grafting was performed in eleven patients. RESULTS Hospital mortality was 17.6% (three patients). Three patients died of cancer during the follow-up. The remaining 11 patients are in good condition after a mean follow-up of 45.8 months (range 7.5-84.2). CONCLUSIONS Postinfarction rupture of ventricular free wall treated surgically gives excellent long-term results. Our first choice for repair is the covering technique with a large pericardial patch anchored with biological glue and epicardial sutures.

Microdialysis for myocardial metabolic surveillance: developing a clinical technique

Metabolic surveillance of the myocardium is of great interest in cardiac surgery. Microdialysis allows sampling of chemical substances from the interstitial fluid for immediate analysis. The two objectives of this study were to develop a technique for simple and safe implantation of a commercially available microdialysis probe (CMA‐70) into the myocardium and to obtain reference data for further use and metabolic control. Eighteen pigs were used in an experimental ischaemic heart model where the left anterior descending coronary artery was occluded for 20 min. Microdialysis was performed proximally as well as distally to the arterial occlusion site corresponding to a control and an ischaemic area in the heart. Two techniques were tried for probe implantation, using either a pacemaker wire attached to the probe tip or a needle introducer. Metabolic substrates (glucose, lactate, glycerol and pyruvate) were collected before, during and after ischaemia, for up to 6 h. Both techniques were highly effective in registering metabolic changes due to ischaemia with sharp time resolution, but the needle introducer was superior regarding probe durability. It is concluded that the CMA‐70 microdialysis probe implanted with the needle introducer allows for an accurate monitoring of myocardial metabolism during a prolonged period of time. Future studies in the human heart are warranted to further validate the technique.

In Situ Detection of Myocardial Infarction in Pig by Measurements of Aspartate Aminotransferase (ASAT) Activity in the Interstitial Fluid

Microdialysis probes permeable to large molecules (m.w. cut-off > 200 kD) were introduced into the myocardium of anaesthetized pigs in order to evaluate their potential for early detection of myocardial ischaemia and enzyme markers for infarction. The left anterior descending coronary artery was occluded for 30 min and the myocardium was reperfused for 3 h. The concentrations of aspartate aminotransferase (ASAT), lactate, glucose and selected free amino acids were measured. The levels in the interstitium of ischaemic and non-ischaemic myocardium were compared with those in plasma from the coronary sinus as well as from a peripheral vein. Twelve probes were inserted in six pigs and withdrawn after 8-72 hours of sampling. No complications occurred. Simultaneous 100% increase of ASAT and lactate was found in myocardial dialysates after 30 min of ischaemia. ASAT activity remained at that level until the end of reperfusion. The plasma peak ASAT level was not attained until after 3 h. Glutamate was the only amino acid which increased significantly in the myocardial interstitium during ischaemia, peaking after 30 min of reperfusion. Dialysates from the unaffected myocardium showed no effects on lactate, ASAT or glutamate. The use of myocardial microdialysis for pre- and postoperative recordings in man is discussed.

Myocardial metabolic monitoring with the microdialysis technique during and after open heart surgery

Background:  Post‐operative ischemia after coronary artery bypass grafting (CABG) is well described but effective intervention requires immediate diagnosis. One possible way of increasing efficacy of peri‐operative myocardial monitoring is using the microdialysis technique.

Intramyocardial Troponin-T Monitoring with Microdialysis in Coronary Artery Bypass Surgery

Objective: To investigate the time course of troponin-T release into the extracellular fluid of the myocardium and to distinguish between a rise in troponin-T due to implantation trauma and an increase due to cardiac arrest during coronary surgery. Design: Microdialysis probes were implanted in the heart of seven patients soon after sternotomy. Troponin-T was measured in the microdialysates and in peripheral blood from 3 h before to 24 h after heart arrest. Results: The troponin-T concentration in the microdialysates increased immediately after probe implantation and decreased to baseline within 70 min. This early peak is interpreted to reflect a local trauma. Three hours after crossclamp release, a second peak of microdialysate troponin-T was recorded; 50 times higher than in serum. Eight to 24 h later a third peak occurred in five patients. Serum troponin-T was below the detection level at the beginning of the operation but increased linearly during the first 3 h of reperfusion and remained at that level thereafter. Conclusion: Microdialysis is a safe technique providing more information on myocardial metabolism during and after bypass surgery than can be obtained from peripheral blood. The release of troponin-T in response to cardiac arrest can be distinguished in time from the local tissue response to probe implantation.

Successful Outcome After Massive Bleeding in A Heart Transplant Recipient With Mycotic Aortitis

Sudden mediastinal haemorrhage one month after heart transplantation in an 18-year-old youth was found to originate from a rupture of the ascending aorta associated with mycotic aortitis. Aortic continuity was restored with a Dacron graft. Cultures from the resected vessel wall showed Candida albicans. The patient recovered, and 11 months later is well.

Glucose-insulin-potassium (GIK) prevents derangement of myocardial metabolism in brain-dead pigs.

Brain death is associated with neuroendocrine changes resulting in reduced myocardial glycogen content. The purpose of this study was to investigate the effects of glucose-insulin-potassium (GIK), on myocardial metabolism in brain-dead pigs. Sixteen brain-dead pigs were given GIK infusion (n = 8), or Ringer solution (n = 8). At end-point (7 h post brain death) arterial concentrations and myocardial arteriovenous (a-v) concentration differences of glucose, lactate and free fatty acids (FFA) were assessed, and myocardial biopsy specimens were taken from the right atrium and left ventricle. Biopsies were also taken from five normal pigs. Myocardial glycogen content in the GIK group was significantly higher compared to the control group, but comparable to the non-brain-dead animals. There was a higher and significant myocardial uptake of glucose and lactate in the GIK group compared to the controls. Plasma levels of FFA were significantly lower in the GIK group, and the myocardial uptake of FFA was 5 times higher in the control group compared to the GIK group. There were no significant differences in hemodynamic variables among the groups. In conclusion, intravenous supply of GIK to brain-dead pigs results in increased myocardial glycogen content and seems to prevent abnormal myocardial metabolism, which may have clinical implications for the myocardial protection of donor hearts.

Myocardial release of FKBP12 and increased production of FKBP12.6 in ischemia and reperfusion experimental models

BACKGROUND Coronary artery occlusion and reperfusion may trigger reversible and irreversible ischemic and reperfusion injury. The primary aim of this study was to evaluate protein release into the myocardium in a porcine model during ischemia and reperfusion to search for clarifying models for reperfusion injury and secondarily to investigate release and production of the immunophilins FKBP12/12.6 in this model and in cell cultures. METHODS In a porcine model local myocardial ischemia was induced during 45min followed by 120min of reperfusion. Microdialysis samples from ischemic and non-ischemic areas were analyzed with surface-enhanced laser desorption ionization (SELDI) mass spectrometry (MS) and Western blotting (WB). Myocardial biopsies from areas at risk and control areas were analyzed with reverse transcription polymerase chain reaction (RT-PCR). Myocardial cell cultures from mice (HL-1 cells) were exposed to hypoxia and then analyzed with WB and RT-PCR. RESULTS FK binding protein12 (FKBP12), ubiquitin and myoglobin were identified as being released during ischemia and reperfusion in microdialysates. RT-PCR analysis on the biopsies after ischemia revealed a non-significant increase in mRNA expression of FKBP12 and a significant increase in mRNA expression of FKBP12.6. Lysates from HL-1 cells exposed to hypoxia demonstrated increase of FKBP12 and a significant increase in mRNA expression of FKBP12.6. CONCLUSION In a myocardial ischemic-reperfusion porcine model as well as in hypoxic HL-1 cells, release of FKBP12 and increased production of FKBP12.6 was demonstrated. The findings indicate important mechanisms related to these immunophilins in the reaction to ischemia/hypoxia and reperfusion in the heart.