Relationship between enzymatically estimated infarct size and short- and long-term survival after acute myocardial infarction

Reduction of ischemia/reperfusion injury with bendavia, a mitochondria-targeting cytoprotective Peptide

Background

Manifestations of reperfusion injury include myocyte death leading to infarction, contractile dysfunction, and vascular injury characterized by the “no-reflow” phenomenon. Mitochondria-produced reactive oxygen species are believed to be centrally involved in each of these aspects of reperfusion injury, although currently no therapies reduce reperfusion injury by targeting mitochondria specifically.

Methods and Results

We investigated the cardioprotective effects of a mitochondria-targeted peptide, Bendavia (Stealth Peptides), across a spectrum of experimental cardiac ischemia/reperfusion models. Postischemic administration of Bendavia reduced infarct size in an in vivo sheep model by 15% (P=0.02) and in an ex vivo guinea pig model by 38% to 42% (P<0.05). In an in vivo rabbit model, the extent of coronary no-reflow was assessed with Thioflavin S staining and was significantly smaller in the Bendavia group for any given ischemic risk area than in the control group (P=0.0085). Myocardial uptake of Bendavia was ≈25% per minute, and uptake remained consistent throughout reperfusion. Postischemic recovery of cardiac hemodynamics was not influenced by Bendavia in any of the models studied. Isolated myocytes exposed to hypoxia/reoxygenation showed improved survival when treated with Bendavia. This protection appeared to be mediated by lowered reactive oxygen species–mediated cell death during reoxygenation, associated with sustainment of mitochondrial membrane potential in Bendavia-treated myocytes.

Conclusions

Postischemic administration of Bendavia protected against reperfusion injury in several distinct models of injury. These data suggest that Bendavia is a mitochondria-targeted therapy that reduces reperfusion injury by maintaining mitochondrial energetics and suppressing cellular reactive oxygen species levels. (J Am Heart Assoc. 2012;1:e001644 doi: 10.1161/JAHA.112.001644.)

Changes in plasma enzyme activity after intramuscular injection of bupivacaine into the human biceps brachii

The purpose of this study was to examine the time course of changes in plasma creatine kinase (CK), lactate dehydrogenase (LDH), aspartate (AST) and alanine aminotransferase (ALT) activity after intramuscular injection of 0.5% bupivacaine (BPVC). A total of 10 mL BPVC was injected into the biceps brachii (two sites, 5 mL per site) of five healthy, male subjects. Blood samples were obtained from the antecubital vein before and 2, 4, 8, 12, 24, 48, 72 and 96 h after the injection. Affected muscle size was visualized using magnetic resonance imaging (MRI), which was performed 4 days after the injection. Plasma CK activity started to increase 2 h and peaked 12 h after the injection. The peak CK activity (470 +/- 62 IU L-1) was approximately four times the pre-injection value (133 +/- 24 IU L-1), and no additional increase was observed after 24 h. Plasma LDH, AST and ALT activities did not change significantly over time. Muscle around the injection sites showed increased T2 signal intensity using MRI. When smaller (2 mL) or larger (20 mL) amounts of BPVC were injected into the biceps brachii in additional experiments, the amount of increase in plasma CK activity appeared to be related to the size of the affected muscle. It was concluded that CK started to leak from damaged muscle cells shortly after the BPVC injection, and the amount of increase in plasma CK activity appeared to reflect the amount of muscle damage.

Ten year mortality in relation to original size of myocardial infarct: results from the Gothenburg metoprolol study

OBJECTIVE

To describe the relation between the extent of a myocardial infarct, measured according to maximum serum enzyme activity of lactate dehydrogenase, and mortality at 10 years.

PATIENTS

In 759 patients with acute myocardial infarction in whom serum activity of heat stable lactate dehydrogenase had been determined every 12 hours for 108 hours after randomisation in an early intervention trial with metoprolol.

MAIN OUTCOME MEASURE

Mortality at 10 years in relation to quartile of maximum serum lactate dehydrogenase activity and history of cardiovascular disease.

RESULTS

Among all patients mortality at 10 years was 39% in the lowest quartile, 51% in the second quartile, 50% in the third, and 59% in the fourth (p < 0.001 for relation between infarct size and 10 year mortality). Among patients without a history of myocardial infarction, angina pectoris, diabetes mellitus, or hypertension the mortality in each quartile was 29%, 32%, 41%, and 56%, respectively (p < 0.001 for relation between infarct size and 10 year mortality). Among patients with any of these risk indicators the association between the estimated infarct size and mortality at 10 years was weak (p < 0.05).

CONCLUSION

Estimated size of a myocardial infarct and mortality over 10 years seem to be related but mainly in patients without a history of cardiovascular disease.

Measurement of oxygen consumption after uncomplicated acute myocardial infarction

BACKGROUND

Oxygen consumption (VO2) has been shown to be decreased after acute myocardial infarction (AMI) complicated by cardiogenic shock.

STUDY OBJECTIVE

To evaluate early measurement of VO2 by indirect calorimetry after an uncomplicated AMI (UAMI).

STUDY DESIGN

Prospective nonrandomized case study.

SETTING

Emergency department of a large urban hospital.

PARTICIPANTS AND INTERVENTIONS

Twenty-six consecutive patients presenting with confirmed UAMI. VO2 was measured by indirect calorimetry (Deletrac, Datex Ins,) which is noninvasive. All patients received buccal or intravenous nitroglycerin and thrombolytic therapy, and none received opiates before VO2 measurement.

RESULTS

Two groups of patients were identified by subsequent development of cardiogenic shock. Group 1 did not develop cardiogenic shock, and group 2 developed shock within 24 h of admission. Group 1 (n = 22) had a significantly higher VO2 compared to group 2 (n = 4), mean 154(SD 25) vs mean 100(SD 13) ml/min.m2, p < 0.002. Group 1 had a significantly higher increase in basal metabolic rate than group 2, mean 30 percent (SD 11) vs mean 10(SD 15) percent, p < 0.007. There was no significant difference in age, heart rate (HR), shock index (SI), or rate-pressure product (RPP) between groups 1 and 2. All patients in group 2 developed cardiogenic shock despite thrombolytic therapy, and two died within 24 h of admission.

CONCLUSION

VO2 is increased in UAMI and represents increased metabolic demands of peripheral tissues and not cardiac oxygen uptake. A reduction in VO2 (< 100 ml/min.m2) after AMI may be an early predictor of subsequent development of cardiogenic shock. Measurement of VO2 in UAMI by indirect calorimetry in the emergency department may be of value to identify patients at high risk and could influence their management.

The relationship between serum enzyme activity, infarct site, and cardiac complications after a first myocardial infarction. A follow-up study in general practice

The aim of the present study was to relate the clinical course in patients after a first acute myocardial infarction with the site and size of infarct, estimated from standard enzyme measurements. One hundred and eight consecutive patients who suffered an acute myocardial infarction for the first time were followed-up after 30 months in general practice. Twenty-six patients had died and 8 had had another infarction. Sixty-two of the surviving patients had received treatment for ischaemic heart disease, usually for angina pectoris and less often for heart failure and arrhythmias. No correlation was found between ischaemic heart disease requiring treatment and the enzyme-estimated size or the site of the infarct. With anterior infarcts there was, however, an overweight of arrhythmias requiring treatment. Of the patients at work, 31% had changed job or job status because of ischaemic heart disease. At the end of the 30 month period, 50 patients were in functional class 1 and 2, and 32 in functional class 3 and 4 (New York Heart Association's classification).

Morbidity during five years after myocardial infarction and its relation to infarct size

In 809 patients with a recent myocardial infarction, morbidity during 5-year follow-up was assessed. The overall 5-year mortality rate was 33% (39% in patients with larger infarcts and 26% in patients with smaller infarcts) as judged from maximum serum enzyme activity (p less than .001). In terms of morbidity, no significant association with estimated infarct size was observed. Patients with smaller infarcts tended to have a higher reinfarction rate and were rehospitalized more often, whereas a similar proportion of patients with large and small infarcts developed stroke. Among survivors, chest pain tended to be more common in patients having smaller infarcts, whereas symptoms of dyspnea and claudicatio intermittens were similar in both groups, as were smoking habits, work capability, and varying forms of medication. We thus conclude that during a 5-year follow-up after acute myocardial infarction, mortality, but not morbidity, was related to the original infarct size.

Secondary prevention after myocardial infarction: effects of beta blocking agents and calcium antagonists

Therapeutic interventions in patients with myocardial infarction, whether during the first hours after coronary occlusion or several days later, aim to reduce mortality and morbidity by several mechanisms: Prevention of fatal ventricular fibrillation, limitation of infarct size, and inhibition of platelet aggregation are some examples of such mechanisms. Results from early intervention trials with beta blocking agents, particularly from ISIS-I, suggest that 1-year mortality is significantly lower in selected patients randomized to active treatment. Late intervention studies also suggest a significant reduction in coronary mortality and morbidity with beta blockade, particularly when data are pooled. Studies with the calcium channel blockers nifedipine and verapamil were unable to demonstrate any beneficial effects of these drugs on mortality or reinfarction. In this review article, attention will be directed to the most recent information about the preventive value of beta adrenergic blocking drugs and slow calcium channel inhibitors.

Five-year mortality rate in relation to enzyme-estimated infarct size in acute myocardial infarction

In 727 patients with acute myocardial infarction, different enzyme variables reflecting infarct size were related to the 5-year mortality rate. The maximum activity of serum heat-stable lactate dehydrogenase (LD), analyzed every 12 hours for 48 to 108 hours, was significantly associated with the 5-year mortality rate when patients with a first myocardial infarction were evaluated (p less than 0.001), and similarly (p less than 0.001) when patients with a previous myocardial infarction were included in the analyses. Very similar results were found when the maximum activity of aspartate aminotransferase (ASAT) analyzed once daily for 3 days was related to the mortality rate over 5 years, whereas the maximum activity of creatine kinase (CK) and CK subunit B analyzed every 6 hours for 48 hours in a subset of patients did not predict the outcome to the same extent. The results from LD and ASAT analyses clearly indicated that the association between infarct size and 5-year mortality rate was caused by the much higher mortality rate in patients with larger infarcts during the first year after onset of infarction, whereas after the first year, incidence of death appeared to be independent of the original infarct size. Thus we conclude that although a highly significant relationship between infarct size and overall 5-year survival was found, the mortality rate seemed to be higher in patients with larger infarcts, particularly during the first year after infarction.

Appearance of T-wave inversions without raised serum enzyme activity in suspected acute myocardial infarction: clinical outcome in relation to subendocardial infarction

In 67 patients with a clinical history of suspected acute myocardial infarction (MI) who developed T-wave inversions in standard ECG and had normal serum aspartate aminotransferase activity (possible MI) the clinical outcome was compared with that in patients fulfilling criteria for subendocardial infarction. Patients with possible MI had a lower mortality (p = 0.02) and also a lower reinfarction rate (p = 0.14) during the first 2 years as compared with those with subendocardial MI. Although patients with subendocardial MI had more problems with chest pain in the acute phase, angina pectoris occurred more frequently in patients with possible MI during a longer follow-up period. Congestive heart failure occurred more frequently in patients with subendocardial MI during initial hospitalization, whereas treatment for heart failure appeared similar in the two groups during a longer follow-up time. We conclude that the clinical course in patients with possible MI, here defined as chest pain and appearance of T-wave inversions without elevation of serum enzyme activity, seems to differ from that in patients with subendocardial MI, particularly regarding long-term survival and incidence of angina pectoris.

Long-term treatment with metoprolol after myocardial infarction: effect on 3 year mortality and morbidity

The effects of metoprolol treatment in patients surviving acute myocardial infarction have been investigated in a double-blind randomized study. The patients were stratified according to age, infarct size and type of ventricular arrhythmias before administration of metoprolol, 100 mg twice daily (n = 154), or placebo (n = 147). All patients were followed up for 36 months. There were 31 (29 cardiac) and 25 (20 cardiac) deaths in the placebo and metoprolol groups, respectively. Subgroup analyses showed a significant reduction of cardiac death in patients with a large infarct (32.1% with placebo versus 12.5% with metoprolol, p less than 0.05) as a result of active treatment. Sudden death rates were 14.7% in the placebo versus 5.8% in the metoprolol group (p less than 0.05). The incidence of nonfatal reinfarction was 21.1% in the placebo versus 11.7% in the metoprolol group (p less than 0.05). The reduction in nonfatal reinfarction was similar in all pretreatment risk strata. The difference between the two groups in cumulative number of cardiac deaths and patients experiencing nonfatal reinfarction increased throughout the study. Furthermore, cerebrovascular events (p less than 0.05) and coronary bypass surgery (p = 0.058) were more frequent in the placebo group. In conclusion, after 36 months of metoprolol treatment after myocardial infarction, there was a significant reduction of nonfatal reinfarction and sudden death in all patients and a reduction of cardiac death in those with a large infarct.