Rapid enzyme release from acutely infarcted myocardium after early thrombolytic therapy: washout or reperfusion damage?

Aldehyde dehydrogenase-2 activation during cardioplegic arrest enhances the cardioprotection against myocardial ischemia-reperfusion injury

Ischemia/reperfusion damage is common during open-heart surgery. Activation of aldehyde dehydrogenase-2 can significantly reduce ischemia/reperfusion damage. We hypothesized that adding aldehyde dehydrogenase-2 agonist to regular cardioplegia solution would further ameliorate ischemia/reperfusion damage. Alda-1 was used as an aldehyde dehydrogenase-2 agonist. Cardioprotection by histidine-tryptophan-ketoglutarate solution with and without Alda-1 was compared using an ex vivo perfused rat heart model of ischemia/reperfusion. Three groups of ex vivo rat hearts endured different treatments with variant ischemia or an ischemia/reperfusion time course: sham, no ischemia/reperfusion; histidine-tryptophan-ketoglutarate; and histidine-tryptophan-ketoglutarate plus Alda-1. Aldehyde dehydrogenase-2 expressions and activities, oxidative parameters (including 4-hydroxy-2-nonenal-His adducts, malondialdehyde levels, and glutathione/oxidized glutathione ratios), myocardial protein carbonyl levels, coronary effluents creatine kinase isoenzyme MB levels, and heart function parameters were measured and compared. Alda-1 significantly elevated myocardium aldehyde dehydrogenase-2 activity (P < .01). Increased aldehyde dehydrogenase-2 activity in turn attenuated ischemia/reperfusion-induced elevation in cardiac aldehydes, creatine kinase isoenzyme MB leakage, and protein carbonyl formation (P < .01). The Alda-1 group also obtained higher glutathione/oxidized glutathione ratios (P < .01). Aldehyde dehydrogenase-2 activation alleviated ischemia/reperfusion-induced cardiomyocyte contractile function impairment as evidenced by improved maximal velocity of pressure development and decline, left ventricular developed pressure, and heart rate (P < .01). Alda-1 supplementation can significantly improve the cardioprotection effect of cardioplegia solution, possibly through activation of aldehyde dehydrogenase-2, to remove toxic aldehydes. This may aid in the identification of novel cardioplegia solutions.

Adjunct thrombus aspiration reduces mortality in patients undergoing percutaneous coronary intervention for ST-elevation myocardial infarction with high-risk angiographic characteristics

Routine aspiration thrombectomy (AT) in percutaneous coronary intervention for patients with ST-segment elevation myocardial infarction (STEMI) has not proved effective in randomized trials. However, in patients undergoing primary percutaneous coronary intervention with severely reduced flow or visible thrombus, AT remains an intuitively attractive option. The use of adjunctive AT in a high-risk cohort of 158 consecutive patients with STEMI and Thrombolysis In Myocardial Infarction (TIMI) 0 to 1 flow or visible thrombus on baseline angiography was examined. Of these, 80 patients underwent AT as an adjunct to primary percutaneous coronary intervention, and 78 underwent percutaneous coronary intervention without AT (non-AT). TIMI 3 flow rates, residual thrombus after percutaneous coronary intervention, and major adverse cardiac events (mortality and nonfatal Q-wave myocardial infarction) at 30 days, 6 months, and 1 year were compared. Baseline characteristics were similar between groups. The AT group more frequently achieved TIMI 3 flow after the intervention (91.3% AT vs 67.9% non-AT; p <0.001) and had less residual thrombus (7.5% AT vs 19.2% non-AT; p = 0.03). AT was associated with reduced major adverse cardiac events at 6 months (6.8% AT vs 24.0% non-AT; p = 0.004) and 1 year (16.6% AT vs 29.2% non-AT; p = 0.009), and decreased mortality rates in the AT group at 6 months (5.4% AT vs 21.3% non-AT; p = 0.004) and 1 year (7.7% AT vs 26.2% non-AT; p = 0.005). In conclusion, for patients with STEMI and TIMI 0 or 1 flow or visible thrombus on baseline angiography, AT was associated with increased TIMI 3 flow rates, decreased residual thrombus, and decreased clinical events, including mortality.

Microdialysis separately monitors myocardial interstitial myoglobin during ischemia and reperfusion

Direct monitoring of myoglobin efflux during ischemia and reperfusion has been limited because of inherent sample collection problems in the ischemic region. Recently, the cardiac dialysis technique has offered a powerful method for monitoring myocardial interstitial levels of low-molecular-weight compounds in the cardiac ischemic region. In the present study, we extended the molecular target to high-molecular-weight compounds by use of microdialysis probes with a high-molecular-mass cutoff and monitored myocardial interstitial myoglobin levels. A dialysis probe was implanted in the left ventricular free wall in anesthetized rabbits. The main coronary artery was occluded for 60 or 120 min. We examined the effects of myocardial ischemia and reperfusion on myocardial interstitial myoglobin levels. Interstitial myoglobin increased within 15 min of ischemia and continued to increase during 120 min of ischemia, whereas blood myoglobin increased at 45 min of ischemia. Lactate and myoglobin in the interstitial space increased during the same period. At 60 min of ischemia, reperfusion markedly accelerated interstitial myoglobin release. The interstitial myoglobin level was fivefold higher at 0–15 min of reperfusion than at 60–75 min of coronary occlusion. The dialysis technique permits earlier detection of myoglobin release and separately monitors myoglobin release during ischemia and reperfusion. Myocardial interstitial myoglobin levels can serve as an index of myocardial injury evoked by ischemia or reperfusion.

Time course and determinants of left ventricular function recovery after primary angioplasty in patients with acute myocardial infarction

OBJECTIVES

We sought to evaluate the importance of time in relation to treatment, time course and determinants of recovery of left ventricular (LV) function in patients with acute myocardial infarction (AMI) undergoing primary percutaneous transluminal coronary angioplasty (PTCA).

BACKGROUND

Myocardial salvage has been shown to be dependent on the time elapsed from the onset of AMI to reperfusion.

METHODS

Left ventricular function was evaluated at hospital admission, after angioplasty, at 24 h and 6 months by both echocardiography and angiography and at 1, 7, 30, 90 and 180 days by echocardiography in 101 consecutive patients.

RESULTS

Patients were allocated to three groups according to interval between symptom onset and angioplasty: <2 h (group A), 2 to 4 h (group B) and >4 h (group C). Patients in groups A and B showed a progressive improvement of LV function between day 7 and day 90, which became statistically significant at day 30 (p < 0.01). No LV function changes were noted in group C patients. Thrombolysis In Myocardial Infarction (TIMI) flow grade <3 at 24 h was not associated with any significant change in LV volume and function during the six-month follow-up period. Restenosis, when associated with TIMI flow grade 3 in the infarct-related vessel, did not influence LV function. Flow grade <3 of the infarct-related artery was not associated with any improvement of cardiac events independently from the time to treatment at the initial procedure.

CONCLUSIONS

Patients undergoing primary PTCA for AMI have a good recovery of LV function if TIMI flow grade 3 is restored within 4 h. Coronary angioplasty limits further remodeling of the LV in patients treated after 4 h.

Shifting the open-artery hypothesis downstream: the quest for optimal reperfusion

Successful reperfusion after acute myocardial infarction (MI) has traditionally been considered to be restoration of epicardial patency, but increasing evidence suggests that disordered microvascular function and inadequate myocardial tissue perfusion are often present despite infarct vessel patency. Thus, optimal reperfusion is being redefined to include intact microvascular flow and restored myocardial perfusion, as well as sustained epicardial patency. Coronary angiography has been used as the gold standard to define failed reperfusion, according to the Thrombolysis In Myocardial Infarction (TIMI) flow grades. However, new angiographic techniques, including the corrected TIMI frame count and myocardial blush grade, have been used to show that epicardial TIMI flow grade 3 may be an incomplete measure of reperfusion success. Furthermore, evolving noninvasive diagnostic techniques, including measurement of infarct size with cardiac marker release patterns or technetium-99m-sestamibi single-photon emission computed tomographic imaging and analysis of ST segment resolution appear to be useful complements to angiography for the assessment of myocardial tissue reperfusion. Promising adjunctive therapies that target microvascular dysfunction, including platelet glycoprotein IIb/IIIa inhibitors, and agents designed to improve tissue perfusion and attenuate reperfusion injury are being evaluated to further improve clinical outcomes after acute MI. To accelerate development of these new reperfusion regimens, an integrated approach to phase II clinical trials that incorporates multiple efficacy variables, including angiography and noninvasive biomarkers of microvascular dysfunction, should be considered. Thus, as the reperfusion era moves into the next millennium, the open-artery hypothesis is expected to shift downstream and guide efforts to further improve myocardial salvage and clinical outcomes after acute MI.

The distinction between coronary and myocardial reperfusion after thrombolytic therapy by clinical markers of reperfusion

OBJECTIVES

We sought to examine the hypothesis that rapid resolution of ST-segment elevation in acute myocardial infarction (AMI) patients with early peak creatine kinase (CK) after thrombolytic therapy differentiates among patients with early recanalization between those with and those without adequate tissue (myocardial) reperfusion.

BACKGROUND

Early recanalization of the epicardial infarct-related artery (IRA) during AMI does not ensure adequate reperfusion on the myocardial level. While early peak CK after thrombolysis results from early and abrupt restoration of the coronary flow to the infarcted area, rapid ST-segment resolution, which is another clinical marker of successful reperfusion, reflects changes of the myocardial tissue itself.

METHODS

We compared the clinical and the angiographic results of 162 AMI patients with early peak CK (< or =12 h) after thrombolytic therapy with (group A) and without (group B) concomitant rapid resolution of ST-segment elevation.

RESULTS

Patients in groups A and B had similar patency rates of the IRA on angiography (anterior infarction: 93% vs. 93%; inferior infarction: 89% vs. 77%). Nevertheless, group A versus B patients had lower peak CK (anterior infarction: 1,083+/-585 IU/ml vs. 1,950+/-1,216, p < 0.01; and inferior infarction: 940+/-750 IU/ml vs. 1,350+/-820, p=0.18) and better left ventricular ejection fraction (anterior infarction: 49+/-8, vs. 44+/-8, p < 0.01; inferior infarction: 56+/-12 vs. 51+/-10, p=0.1). In a 2-year follow-up, group A as compared with group B patients had a lower rate of congestive heart failure (1% vs. 13%, p < 0.01) and mortality (2% vs. 13%, p < 0.01).

CONCLUSIONS

Among patients in whom reperfusion appears to have taken place using an early peak CK as a marker, the coexistence of rapid resolution of ST-segment elevation further differentiates among patients with an opened culprit artery between the ones with and without adequate myocardial reperfusion.

Thrombolysis-induced coronary reperfusion causes acute and massive interstitial release of cardiac muscle cell proteins

OBJECTIVE

Reperfusion of the infarct-related artery in patients with acute myocardial infarction limits infarct size, but also causes accelerated release into plasma of cardiac tissue proteins. The latter effect could reflect either enhanced protein washout from the heart or abrupt disruption of myocyte membranes. The present study indicates that the latter mechanism prevails.

METHODS

In 26 patients, patency of the infarct-related artery was determined by coronary angiography 90 min and 5-7 days after thrombolytic treatment. Continuous electrocardiography was performed during the first 24 h after admission. Cumulative release of myoglobin (Mb) and creatine kinase (CK) into plasma was calculated from frequently sampled plasma concentrations.

RESULTS

In patients with a patent infarct-related artery after 90 min, onset of a rapid (> 50%) decrease in ST-vector magnitude coincided with an equally rapid increase in QRS-vector magnitude, and with a sudden onset of release into plasma of Mb as well as CK. In these patients, a maximal initial release rate was observed and cumulative release conformed closely to a simple model for sudden interstitial liberation of proteins. In contrast, protein release started more gradually and could not be fitted to this model, in patients with persistent occlusion of the infarct-related artery at 90 min and absence of ST-vector normalisation.

CONCLUSIONS

Previous studies have demonstrated significant myocardial salvage by timely reperfusion therapy. Nevertheless, this study indicates that the moment of recanalisation of the infarct-related artery coincides with sudden and massive disruption of myocyte membranes. Attenuation of this effect, if possible, could further improve the benefits of reperfusion therapy.

Ridogrel as an adjunct to thrombolysis in acute myocardial infarction

An open pilot study was performed to assess the safety and preliminary efficacy of ridogrel, a selective thromboxane-A2 synthetase inhibitor and thromboxane-A2/prostaglandin endoperoxide receptor blocker, as adjunct to thrombolysis, with alteplase and heparin. In 50 patients with acute myocardial infarction, 300 mg ridogrel was injected intravenously in addition to alteplase and heparin. Ridogrel was continued orally (300 mg) twice daily for 5 days. Patency rate at initial (90 min) angiography, defined as thrombolysis in myocardial infarction perfusion grades 2 or 3, was 86%. Rescue percutaneous transluminal coronary angioplasty was performed in 10 patients; immediate results were good in nine, while a large dissection occurred in one patient. New ischemia occurred in 10 patients within 24 h, and after the second angiogram in seven cases. Three underwent coronary artery bypass grafting and seven percutaneous transluminal coronary angioplasty without further complication. Patency rate at second angiography (between 6 and 24 h) was 94%. New Q-waves appeared in 56% of the patients; 36% had a non-Q-wave infarction and 8% had no enzyme rise. Enzymatic infarct size, estimated by the cumulative quantity of alpha-hydroxybutyrate dehydrogenase released in 72 h, was substantially smaller than in comparable studies with rt-PA and heparin. One patient died due to a cerebrovascular hemorrhage. No other deaths occurred. Bleeding complications were seen in 18 patients (36%), necessitating blood transfusion in three. Reinfarction did not occur. Eventually 49 patients were discharged in good condition. Safety with regard to bleeding complications of ridogrel in conjunction with alteplase is about the same as that of aspirin. Immediate and late patency rates were high. Rescue percutaneous transluminal coronary angioplasty could be performed with relative safety and early reocclusion could be successfully dealt with by repeat percutaneous transluminal coronary angioplasty. Further studies with this or similar compounds seem warranted.

Defibrotide versus heparin in the prevention of coronary reocclusion after thrombolysis in acute myocardial infarction

A multicenter controlled study versus heparin was conducted to explore the activity of defibrotide, a polydesoxyribonucleotide drug, in preventing reocclusion after urokinase thrombolysis in patients with acute myocardial infarction (AMI). The study involved 137 consecutive patients with AMI and a time from the onset of symptoms < or = 6 hours, treated with urokinase (1,000,000 U intravenous bolus followed by 1,000,000 U slow-drip infusion over 12 hours). Immediately after thrombolysis, patients were allocated to treatment with defibrotide (group D: day 0, 3.6 g by intravenous infusion in 12 hours; days +1 to +6, 800 mg tid intravenously; days +7 to +10/+12, 400 mg tid intramuscularly), or heparin (group H: day 0, 1000 IU/hour infused over 12 hours; days +1 to +10/+12, 5000 IU tid subcutaneously). Coronary angiography was done, whenever possible, at +10/+12 days. The following parameters were assessed: (a) noninvasive estimate of myocardial reperfusion, through the analysis of CPK time-activity curves; (b) incidence of infarct-related artery (IRA) patency (TIMI scores 2-3) at coronary angiography. A total of 125 patients had a complete enzymatic curve (63 in group D and 62 in group H) and 106 had coronary angiography as well. IRA patency (the main end point) was observed in 63% of group D versus 43% of group H patients (p = 0.07). No statistically significant differences were found in the proportion of patients with indirect signs of early reperfusion (63% in group D versus 52% in group H patients).(ABSTRACT TRUNCATED AT 250 WORDS)

Sudden increase of the ST segment elevation at time of reperfusion predicts extensive infarcts in patients with intravenous thrombolysis

Within 4 hours from the onset of symptoms in 61 patients with myocardial infarction and intravenous thrombolysis, ST segment elevation and creatine phosphokinase (CK) were measured every 15 minutes. Because of a premature enzyme rise, 42 patients (69%) were reperfused early (group 1). Immediately following reperfusion, eight of them (13%, group 1a) showed a marked increase of the ST elevation, in six of whom it was associated with clearly intensified chest pain. These patients exhibited a much steeper enzyme release and developed a larger enzymatic infarct size than patients (group 1b) without an additional transient ST elevation at reperfusion (CK peak 5.1 +/- 1.6 vs 9.8 +/- 4.2 hours after the start of thrombolysis; CK release 48 +/- 22 vs 19 +/- 18 IU/ml x hours, both p < 0.005). At angiography 11 days later, left ventricular function was significantly worse in group 1a than in group 1b (regional dyssynergic area 51 +/- 24 vs 21 +/- 18, global ejection fraction 39 +/- 14 vs 58 +/- 11; both p < 0.0005). During intravenous thrombolysis in acute myocardial infarction, some patients show a marked transient increase of the ST segment elevation at reperfusion. Their enzyme rise is very rapid and suggests a special reperfusion pattern. Most of these patients suffered large infarcts.

Serum phospholipase A2 and lysolecithin changes following myocardial infarction

We have examined changes in the activities of phospholipase A2 (PLA2) and the concentrations of total choline-phospholipids and lysolecithin, in serum from patients following a myocardial infarction by comparison with patients suffering from unstable angina. A significant increase in PLA2 activity was found after myocardial infarction. The peak increase occurred approximately 36 h after infarction. No significant PLA2 change was found in the patients with unstable angina. Concentrations of lysolecithin, the major metabolite of PLA2 activity, were high in the admission samples from the infarction patients, followed by an overall fall during the first 24 h: the concentrations in the patients with angina were normal. PLA2 and lysolecithin changes post-infarction showed they were involved in processes not occurring in angina.

Are enzymatic tests good indicators of coronary reperfusion?

OBJECTIVE

To assess the accuracy of four enzymatic tests, including early release rates of creatine kinase and alpha-hydroxybutyrate dehydrogenase, in assessing coronary reperfusion after thrombolytic therapy.

DESIGN

A prospective clinical trial identifying patients with a successful thrombolytic treatment.

PATIENTS

Eighty nine patients with acute myocardial infarction were studied. Arteriography showed a closed infarct related artery in all of them. Reperfusion due to thrombolysis occurred in 74 patients and there was no reperfusion in 15 patients.

RESULTS

The 74 patients showing coronary reperfusion had a significantly shorter time to peak creatine kinase activity, higher early release rates for creatine kinase and alpha-hydroxybutyrate dehydrogenase, and a more rapid release of alpha-hydroxybutyrate dehydrogenase (ratio of cumulative release of alpha-hydroxybutyrate dehydrogenase during the first 24 hours to that 72 hours after infarction). All these differences were statistically significant (p less than 0.001). Optimum cut off levels were determined with decision level plots and the accuracy of the four enzymatic tests was calculated. Accuracy was low for all four tests (73%, 70%, 70%, and 82%).

CONCLUSION

None of the four enzymatic tests accurately predicted the perfusion state of the infarct related coronary artery after thrombolysis. These tests cannot be used reliably in routine clinical practice as non-angiographic markers of coronary reperfusion.

Time course of cellular enzyme release in dog heart injury

The transport time of enzyme from heart to plasma was studied in two experimental models. First, the enzyme alanine aminotransferase was slowly infused into the left ventricular wall in open-chest dogs. The half-life for the washout of alanine aminotransferase activity into plasma was 20 +/- 4 minutes (mean +/- SEM, n = 8) and was not different in ischemic and normally perfused tissue. From measurements of arteriovenous differences in alanine aminotransferase activity and left ventricular blood flow, it was concluded that 77 +/- 14% of total enzyme washout from ischemic tissue occurred by direct entry into the bloodstream. The corresponding value for the vascular permeability-surface area product was 264 +/- 55 ml.kg-1.hr-1. For a second model, we studied myocardial enzyme release into plasma after abrupt heart injury induced by 10 minutes of calcium-free coronary perfusion followed by reintroduction of calcium (calcium-paradox mechanism). The half-life for the release into plasma was 1.9 +/- 0.2 hours (mean +/- SEM, n = 6) and was again not influenced by sustained ischemia. Slower washout, as observed for this second model, is consistent with increased interstitial protein space and corresponds to a permeability--surface area product between 135 and 285 ml.kg-1.hr-1. These results were used to calculate the time course of cellular enzyme leakage from the rate of enzyme release into plasma in various forms of heart injury. Significant shifts between the time curves of evolving cellular injury and enzyme release into plasma are observed after 2 hours of ischemia followed by coronary reperfusion, but not after permanent ischemia.

At what level of serum total creatine kinase activity can measurement of serum creatine kinase MB isoenzyme activity be omitted in suspected myocardial infarction?

The purpose of this study was to establish a discriminatory limit for serum total creatine kinase activity (CK activity) below which CK isoenzyme fractionation is unnecessary. We looked at 2610 serum samples from 1077 consecutive patients with suspected acute myocardial infraction (AMI). The CK activity was determined according to the Scandinavian recommended method. Isoenzymes of CK were separated by agarose gel electrophoresis, followed by fluorometric scanning. When the threshold for CK activity was 150 U/l, none of the samples had a creatine kinase MB isoenzyme activity (CK-MB activity) equal to or higher than 30 U/l (the diagnostic level), which has been found to differentiate between patients with AMI and those without AMI. Only 14 patients (1.3% of all patients investigated) had CK-MB activity peaks between 10 U/l (detection limit) and 30 U/l. Of these, AMI was only diagnosed in one. We recommend that CK-MB activity should be measured only when CK activity is higher than 150 U/l. This would make about 50% of all CK-MB measurements unnecessary.

Optimal criteria for rapid detection of myocardial reperfusion by creatine kinase MM isoforms in the presence of residual high grade coronary stenosis

Analysis of isoforms of MM creatine kinase (CK) in plasma is being developed as a means for rapid detection of coronary recanalization in patients given thrombolytic agents. To determine whether flow-limiting residual stenosis typical of that seen in patients affects plasma isoform profiles, stenosis sufficient to preclude reactive hyperemia was induced in dogs before coronary occlusion, followed by recanalization in 2 h. Plasma activities of the MM CK isoform released from myocardium (MM3) and its two conversion products elaborated sequentially (MM2 and MM1) were assayed in serial samples with a rapid quantitative chromatofocusing procedure. Reperfusion in 10 dogs shortened the mean intervals (+/-SD) to the occurrence of peak MM3 activity (3.7 +/- 0.9 h), peak MM3 expressed as a percent of total CK activity (MM3%, 2.5 +/- 0.3 h) and the maximal ratio of MM3 to MM1 (2.7 +/- 0.3 h) compared with results in 10 control dogs without reperfusion. Nevertheless, the appearance of these peaks was delayed by 8% to 57% when residual stenosis was present. In contrast, the rate of increase of MM3% was delineated before the peak, was fivefold greater with recanalization (1.19 +/- 0.46 versus 0.26 +/- 0.11% min-1 in control dogs) and was not attenuated by residual stenosis. Thus, this criterion appears capable of delineating recanalization early after thrombolysis whether or not high grade residual stenosis is present.