Evidence of ischemic preconditioning in patients experiencing first non-ST-segment elevation myocardial infarction (NSTEMI)

Association Between Preinfarction Angina and Angiographic Findings in Non-ST-Segment Elevation Myocardial Infarction

BACKGROUND

The association between preinfarction angina and angiographic findings has not been elucidated in patients with non-ST-segment elevation myocardial infarction (NSTEMI).

HYPOTHESIS

Patients with preinfarction angina have favorable angiographic findings.

METHODS

This retrospective study analyzed 481 patients who underwent coronary angiography within 5 days of presenting NSTEMI. Preinfarction angina was defined as experiencing ≥1 chest-pain episode within 7 days prior to admission. Infarct size was measured as the peak cardiac troponin I (cTnI) level, and large myocardial infarction (MI) was defined as a peak cTnI level >85th percentile value in the study population. Infarct-related artery (IRA) patency was defined as Thrombolysis In Myocardial Infarction grade 2 or 3 flow. Clinical and angiographic characteristics and in-hospital mortality were compared between patients with and without preinfarction angina.

RESULTS

Among 481 patients, 200 (42%) had preinfarction angina. Preinfarction angina was associated with smaller infarct size, indicated by lower peak cTnI levels (P = 0.006) and lower incidence of large MI (P = 0.02), and IRA patency (P = 0.03). There was no significant difference in in-hospital mortality. On multivariate analysis, both preinfarction angina (odds ratio: 0.53, 95% confidence interval: 0.29-0.94, P = 0.03) and IRA patency (odds ratio: 0.30, 95% confidence interval: 0.17-0.52, P < 0.001) were independent negative predictors of large MI.

CONCLUSION

Our study demonstrates that preinfarction angina is a predictor of smaller infarct size and infarct-related artery patency in NSTEMI patients, suggesting that NSTEMI patients presenting without preinfarction angina are at increased risk of developing a large MI.

Pre-infarction angina and outcomes in non-ST-segment elevation myocardial infarction: data from the RICO survey

Background

The presence of pre-infarction angina (PIA) has been shown to confer cardioprotection after ST-segment elevation myocardial infarction (STEMI). However, the clinical impact of PIA in non-ST-segment elevation myocardial infarction (NSTEMI) remains to be determined.

Methods and Results

From the obseRvatoire des Infarctus de Côte d'Or (RICO) survey, 1541 consecutive patients admitted in intensive care unit with a first NSTEMI were included. Patients who experienced chest pain <7 days before the episode leading to admission were defined as having PIA and were compared with patients without PIA. Incidence of in-hospital ventricular arrhythmias (VAs), heart failure and 30-day mortality were collected. Among the 1541 patients included in the study, 693 (45%) patients presented PIA. PIA was associated with a lower creatine kinase peak, as a reflection of infarct size (231(109–520) vs. 322(148–844) IU/L, p<0.001) when compared with the group without PIA. Patients with PIA developed fewer VAs, by 3 fold (1.6% vs. 4.0%, p = 0.008) and heart failure (18.0% vs. 22.4%, p = 0.040) during the hospital stay. Overall, there was a decrease in early CV events by 26% in patients with PIA (19.2% vs. 25.9%, p = 0.002). By multivariate analysis, PIA remained independently associated with less VAs.

Conclusion

From this large contemporary prospective study, our work showed that PIA is very frequent in patients admitted for a first NSTEMI, and is associated with a better prognosis, including reduced infarct size and in hospital VAs. Accordingly, protecting the myocardium by ischemic or pharmacological conditioning not only in STEMI, but in all type of MI merits further attention.

Beneficial effect of ischemic preconditioning on post-infarction left ventricular remodeling and global left ventricular function

BACKGROUND

Preinfarction angina (PA) is a clinical analogue of ischemic preconditioning that improves postinfarct prognosis. Data concerning the association of PA with post infarction left ventricular (LV) remodeling and LV diastolic function are limited. We aimed to evaluate this association in patients with acute myocardial infarction (AMI) in the modern clinical era of widespread use of revascularization and antiremodeling medical treatment.

METHODS

We studied 53 patients with anterior AMI who underwent complete reperfusion and received up to date antiremodeling medical treatment. LV remodeling, systolic and diastolic function were assessed using 2D echocardiography at baseline and 6 at months follow-up. Patients were divided into two groups regarding the presence or absence of PA.

RESULTS

LV remodeling at follow-up was less frequent in the PA group (25 vs. 55 %, P<.05). Patients with PA had lower end-systolic volume index at baseline and follow up (24.1±6 vs. 30.1±14 ml/m(2), P<.001 and 25.3±8 vs. 35.6±2 ml/m(2), P=.001 respectively). Additionally at 6 months, they had better LV ejection fraction (52.1±9 vs. 42.9±10 %, P=.002) and exhibited improved diastolic filling as reflected by mitral E/e' (14.6±5 vs. 18.8±8, P=.05).

CONCLUSIONS

Ischemic preconditioning in the form of PA promotes better LV systolic and diastolic function in the mid-term and is associated with less postinfarct LV remodeling in this specific study population. The results of the study underline the possible need for further risk stratification of AMI patients regarding the absence of PA.

Loss of cardioprotection with ageing

Not only the prevalence, but also the mortality due to ischaemic cardiovascular disease is higher in older than in young humans, and the demographic shift towards an ageing population will further increase the prevalence of age-related cardiovascular disease. In order to develop strategies aimed to limit reversible and irreversible myocardial damage in older patients, there is a need to better understand age-induced alterations in protein expression and cell signalling. Cardioprotective phenomena such as ischaemic and pharmacological pre and postconditioning attenuate ischaemia/reperfusion injury in young hearts. Whether or not pre and postconditioning are still effective in aged organs, animals, or patients, i.e. under conditions where such cardioprotection is most relevant, is still a matter of debate; most studies suggest a loss of protection in aged hearts. The present review discusses changes in protein expression and cell signalling important to ischaemia/reperfusion injury with myocardial ageing. The efficacy of cardioprotective manoeuvres, e.g. ischaemic pre and postconditioning in aged organs and animals will be discussed, and the development of strategies aimed to antagonize the age-induced loss of protection will be addressed.

Interaction of cardiovascular risk factors with myocardial ischemia/reperfusion injury, preconditioning, and postconditioning

Therapeutic strategies to protect the ischemic myocardium have been studied extensively. Reperfusion is the definitive treatment for acute coronary syndromes, especially acute myocardial infarction; however, reperfusion has the potential to exacerbate lethal tissue injury, a process termed "reperfusion injury." Ischemia/reperfusion injury may lead to myocardial infarction, cardiac arrhythmias, and contractile dysfunction. Ischemic preconditioning of myocardium is a well described adaptive response in which brief exposure to ischemia/reperfusion before sustained ischemia markedly enhances the ability of the heart to withstand a subsequent ischemic insult. Additionally, the application of brief repetitive episodes of ischemia/reperfusion at the immediate onset of reperfusion, which has been termed "postconditioning," reduces the extent of reperfusion injury. Ischemic pre- and postconditioning share some but not all parts of the proposed signal transduction cascade, including the activation of survival protein kinase pathways. Most experimental studies on cardioprotection have been undertaken in animal models, in which ischemia/reperfusion is imposed in the absence of other disease processes. However, ischemic heart disease in humans is a complex disorder caused by or associated with known cardiovascular risk factors including hypertension, hyperlipidemia, diabetes, insulin resistance, atherosclerosis, and heart failure; additionally, aging is an important modifying condition. In these diseases and aging, the pathological processes are associated with fundamental molecular alterations that can potentially affect the development of ischemia/reperfusion injury per se and responses to cardioprotective interventions. Among many other possible mechanisms, for example, in hyperlipidemia and diabetes, the pathological increase in reactive oxygen and nitrogen species and the use of the ATP-sensitive potassium channel inhibitor insulin secretagogue antidiabetic drugs and, in aging, the reduced expression of connexin-43 and signal transducer and activator of transcription 3 may disrupt major cytoprotective signaling pathways thereby significantly interfering with the cardioprotective effect of pre- and postconditioning. The aim of this review is to show the potential for developing cardioprotective drugs on the basis of endogenous cardioprotection by pre- and postconditioning (i.e., drug applied as trigger or to activate signaling pathways associated with endogenous cardioprotection) and to review the evidence that comorbidities and aging accompanying coronary disease modify responses to ischemia/reperfusion and the cardioprotection conferred by preconditioning and postconditioning. We emphasize the critical need for more detailed and mechanistic preclinical studies that examine car-dioprotection specifically in relation to complicating disease states. These are now essential to maximize the likelihood of successful development of rational approaches to therapeutic protection for the majority of patients with ischemic heart disease who are aged and/or have modifying comorbid conditions.

Characteristics and outcome of patients with acute myocardial infarction according to presenting electrocardiogram (from the MONICA/KORA Augsburg Myocardial Infarction--Registry)

Acute myocardial infarctions (AMIs) are categorized according to presenting electrocardiography into ST-elevation (STE), non-STE, and bundle branch block AMIs. Data on the characteristics and risks of these categories originate mainly from voluntary registries or clinical trials and may be hampered by selection and information bias. This study evaluated these different categories, with the additional differentiation of non-STE AMIs into ST-depression (STD) AMIs and those with nonspecific electrocardiographic signs (no-ST) in an unselected cohort. From 1985 to 2004, all consecutive patients aged 25 to 74 years who were hospitalized with AMI at the study region's major clinic were registered prospectively. A total of 6,748 patients were identified, of whom 45.8% had STE, 14.0% STD, 32.4% no-ST, and 7.8% bundle branch block AMIs, respectively. There were substantial differences in medical history, presentation, and therapy among the AMI types. Even after adjusting for the latter factors, the odds ratios of 28-day case fatality compared with no-ST were 1.26 (95% confidence interval 1.01 to 1.59) for STE, 1.84 (95% confidence interval 1.39 to 2.44) for STD, and 3.18 (95% confidence interval 2.37 to 4.27) for bundle branch block. In conclusion, after considering in-hospital therapy, the difference between STE and no-ST was nonsignificant, whereas the case-fatality difference between no-ST and STD persisted, suggesting some other unknown underlying factors associated with STD.

Endogenous estrogen mediates a higher threshold for endotoxin-induced myocardial protection in females

Myocardial endotoxin tolerance may be induced in both males and females; however, it remains unknown whether there are mechanistic and threshold differences between the sexes. We hypothesized that endogenous estrogen mediates a higher threshold for endotoxin (ETX)-induced protection in females. Adult proestrus and ovariectomized (OVX) female rats were preconditioned (PC) with intraperitoneal injections of 125 (PC+125) or 500 (PC+500) μg/kg Salmonella typhimurium LPS (ETX) or normal saline (PC−). Twenty-four hours later, injury dose ETX (500 μg/kg) was injected. After 6 h, myocardial function was measured via Langendorff. p38 MAPK and JNK activation and TNF-α, IL-1, and IL-6 expression were evaluated. ETX injury significantly decreased left ventricular developed pressure in PC− groups vs. controls. PC+500 regimen protected against ETX injury, resulting in normal cardiac function. PC+125 regimen protected OVX but not proestrus females, which had diminished myocardial function. Activated JNK and TNF-α increased in PC− but were diminished in PC+500 animals. Importantly, activated JNK and TNF increased in PC+125 proestrus females, whereas PC+125 OVX females displayed decreases in these molecules. There were no differences in p38 MAPK activation or expression of IL-1 or IL-6. These results demonstrate that proestrus females require a higher stimulus (PC+500) to achieve myocardial protection against ETX injury. Removal of endogenous estrogen (OVX) lowered the preconditioning threshold (PC+125), resulting in protection after lesser injury. Additionally, myocardial JNK and TNF expression was decreased in OVX PC+125 females, which correlated with myocardial function differences. Therefore, we conclude that endogenous estrogen mediates a higher threshold for ETX tolerance in female myocardium.

Is the Preconditioning Threshold Different in Females?

BACKGROUND

Preconditioning is injury induced protection against subsequent insult. Studies have shown that both males and females may be preconditioned. Females appear to have an innate cardioprotection, therefore, we hypothesized that the preconditioning threshold may differ between males and females.

MATERIALS AND METHODS

Male and female rats were divided into five groups (n=4-9). Animals were given an intraperitoneal (i.p.) injection of 125, 250, or 500 micrograms/kilogram Salmonella typhimurium lipopolysaccharide (ETX) or 0.4-ml normal saline (NS). After 24-h incubation another i.p. injection of either 500 micrograms/kilogram ETX (injury dose) or NS was given and the animals incubated an additional 6 h. Shams received two injections of NS. Non-preconditioned rats (PC-) received NS followed by ETX. Preconditioned rats had i.p. injections of 125 mug/kg ETX (PC +125), 250 microg/kg ETX (PC +250), or 500 microg/kg ETX (PC +500) followed by the injury dose ETX. The rats were then anesthetized and myocardial function evaluated with the Langendorff perfusion model.

RESULTS

PC +500 females were preconditioned and were able to maintain cardiac function similar to shams. Conversely, PC +125 females were not preconditioned with this stimulus and had a significant decrease in cardiac function similar to PC- rats. Male PC +500 and PC +125 rats, however, retained cardiac function comparable to shams, while PC- males showed a significant decrement.

CONCLUSIONS

Males and females may each be preconditioned by endotoxin; however, the preconditioning threshold is higher in females than males.