Assessment and management of patients with ischemic heart disease

[Cardiac biomarkers for diagnosis of myocardial infarction]

Diagnosis of postoperative myocardial infarction is often difficult, based on tools with a low sensitivity (clinical symptoms, EKG), or with a low specifity (old biomarkers, echocardiographic abnormalities) or inadequate for clinical practice (scintigraphy). Since 1995, clinicians may use more cardiospecific markers (troponin) allowing to modify strategy for postoperative myocardial infarction diagnosis. The aim of this review is to resume such an attitude.

Significance and interpretation of elevated troponin in septic patients

Because no bedside method is currently available to evaluate myocardial contractility independent of loading conditions, a biological marker that could detect myocardial dysfunction in the early stage of severe sepsis would be a helpful tool in the management of septic patients. Clinical and experimental studies have reported that plasma cardiac troponin levels are increased in sepsis and could indicate myocardial dysfunction and poor outcome. The high prevalence of elevated levels of cardiac troponins in sepsis raises the question of what mechanism results in their release into the circulation. Apart from focal ischemia, several factors may contribute to the microinjury and minimal myocardial cell damage in the setting of septic shock. A possible direct cardiac myocytotoxic effect of endotoxins, cytokines or reactive oxygen radicals induced by the infectious process and produced by activated neutrophils, macrophages and endothelial cells has been postulated. The presence of microvascular failure and regional wall motion abnormalities, which are frequently observed in positive-troponin patients, also suggest ventricular wall strain and cardiac cell necrosis. Altogether, the available studies support the contention that cardiac troponin release is a valuable marker of myocardial injury in patients with septic shock.

Activation of an efferent cholinergic pathway produces strong protection against myocardial ischemia/reperfusion injury in rats

OBJECTIVE

A vagus nerve-mediated, brain cholinergic protective mechanism activated by melanocortin peptides is operative in conditions of circulatory shock; moreover, there is anatomical evidence of dual vagal-cardiac efferent pathways in rats, which could play different roles in controlling heart function. Therefore, we investigated the role and functional mechanism of such vagal efferent pathway(s) in an experimental model of ischemic heart disease.

DESIGN

Randomized experimental study.

SETTING

Research laboratory.

SUBJECTS

Adult Wistar rats of either sex.

INTERVENTIONS

After bilateral cervical vagotomy (with or without pretreatment with atropine), efferent vagal fibers were electrically stimulated in rats subjected to coronary artery occlusion (5 mins) followed by reperfusion (5 mins). Other rats (intact, vagotomized, or pretreated with atropine) were treated with nanomolar doses of melanocortin peptides.

MEASUREMENTS AND MAIN RESULTS

Electrical stimulation of efferent vagal fibers (5 V, 2 m secs, 1-9 Hz, for the whole period of ischemia/reperfusion) strongly reduced the high incidence of severe arrhythmias and lethality, reduced the increase in free radical blood levels and left-ventricle histologic alterations, and augmented the extracellular signal-regulated kinase activation. Treatment with the melanocortin peptides adrenocorticotropin and gamma2-melanocyte-stimulating hormone (162 nmol/kg intravenously or 16.2 nmol/kg intracerebroventricularly, during coronary occlusion) produced the same protective effects of electrical stimulation and with the same muscarinic acetylcholine receptor-dependent mechanism, seemingly through brain activation (mediated by melanocortin MC3 receptors, as previously described) of such efferent vagal pathway.

CONCLUSIONS

The present results give evidence for the identification of a protective, melanocortin-activated, efferent vagal cholinergic pathway, operative in conditions of myocardial ischemia/reperfusion. These data suggest that melanocortins and pertinent compounds able to activate such a pathway could provide the potential for development of a new class of drugs for a novel approach to management of ischemic heart disease.

Usefulness of noncoronary vascular disease in predicting adverse events in the year following percutaneous coronary intervention

It is unknown whether noncoronary vascular disease is associated with persistent cardiac risk in patients who undergo percutaneous coronary intervention (PCI). Using the National Heart, Lung, and Blood Institute Dynamic Registry, the incidence of death, myocardial infarction (MI), and repeat revascularization outcomes were compared in patients who had noncoronary vascular disease (n = 554) with patients who did not (n = 4,075). Vascular disease was defined as a history of stroke, transient ischemic attack, claudication, vascular bypass, limb amputation, or aortic aneurysm. Patients who had concomitant noncoronary vascular disease had more significant co-morbidities. Angiographic success rate was lower in patients who had concomitant noncoronary vascular disease (89.5% vs 93.2%, p <0.01), whereas in-hospital adverse events, including death (2.7% vs 1.3%, p <0.05), MI (4.7% vs 2.6%, p <0.01), stroke (1.1% vs 0.2%, p <0.001), major entry site complication (6.7% vs 3.5%, p <0.001), and need for coronary artery bypass grafting (2.2% vs 1.1%, p <0.05) were significantly higher. One-year death rate (10.5% vs 4.5%, p <0.001) and MI rate (9.2% vs 5.2%, p <0.001) were also significantly higher in patients who had vascular disease. After adjustment, vascular disease was independently associated with a higher risk of death or MI (risk ratio 1.4, 95% confidence interval 1.1 to 1.8) and death, MI, or coronary artery bypass grafting (risk ratio 1.3, 95% confidence interval 1.1 to 1.6) at 1 year. Repeat PCI rates were similar (15.9% vs 13.8%, p = NS). In conclusion, the presence of noncoronary vascular disease is an independent predictor of MI and death or MI 1 year after PCI. Because PCI is often performed before vascular surgery, these data may lend insight to the risk/benefit ratio of such an approach.