Comparison of low-dose dobutamine stress echocardiography and echocardiography during glucose-insulin-potassium infusion for detection of myocardial viability after anterior myocardial infarction

CT imaging of myocardial scars with collagen-targeting gold nanoparticles

In the setting of myocardial ischemia, recovery of myocardial function by revascularization procedures depends on the extent of coronary disease and myocardial scar burden. Currently, computed tomographic (CT) imaging offers superior evaluation of coronary lesions but lacks the capability to measure the transmural extent of myocardial scar. Our work focuses on determining if collagen-targeting gold nanoparticles (AuNPs) can effectively target myocardial scar and provide adequate contrast for CT imaging. AuNPs were coated with a collagen-homing peptide, collagen adhesin (CNA35). Myocardial scar was created in mice by occlusion/reperfusion of the left anterior descending coronary artery. Thirty days later, un-gated CT imaging was performed. Over 6h, CNA35-AuNPs provided uniform and prolonged opacification of the vascular structures (100-130 HU). In mice with larger scar burden, focal contrast enhancement was detected in the myocardium, which was not apparent within that of control mice. Histological staining confirmed myocardial scar formation and accumulation of AuNPs.

FROM THE CLINICAL EDITOR

This team of investigators presents a collagen-targeting gold nanoparticle-based approach that enables the imaging of myocardial scars via CT scans in a rodent model. This information would enable clinicians to judge the recovery potential of myocardium more accurately than the current CT-scan based approaches.

The effect of insulin on the heart : Part 1: Effects on metabolism and function

Positive inotropic effects of insulin were described early after the isolation of insulin from the pancreas but data on the effect of insulin on the heart are conflicting. Systemic insulin administration results in a reduction in circulating free fatty acids and an improvement in myocardial glucose uptake, which causes an efficiency improvement in the myocardial cell. There is strong evidence that insulin administration results in functional improvement in dysfunctional myocardium. (Neth Heart J 2010;18:197-201.).

Effects of GIK (glucose-insulin-potassium) on stress-induced myocardial ischaemia

Despite the evidence in experimental animal models that insulin, or GIK (glucose-insulin-potassium), improves left ventricular function and perfusion during both acute and chronic ischaemia, clinical studies have generated conflicting results. We tested the hypothesis that pretreatment with GIK attenuates the vascular and functional effects of stress-induced myocardial ischaemia in humans. Twenty-two patients with evidence of inducible myocardial ischaemia were enrolled; 11 patients with normal ventricular function underwent two dipyridamole echocardiography tests, and 11 with regional contractility defects from previous myocardial infarction were submitted to two ECG exercise tests combined with 201Tl myocardial perfusion scintigraphy; the tests were preceded by 60 min of either normal saline or an isoglycaemic GIK infusion. On a stress echocardiogram, a 30% reduction in the severity of ischaemia was observed. On ECG ergometry, GIK infusion slightly increased the time to ischaemia (+0.6 min, P=0.07); however, the higher workload (+8%, P=0.07) was achieved at a similar rate-pressure plateau. On scintigraphy, an increase in ischaemic segments (+48%, P<0.001) was imaged mainly at the expense of viable (but non-ischaemic) and non-viable segments, which were reduced by 60%. GIK affected stress-induced left ventricular underperfusion only marginally (GIK: 39.7+/-2.5 compared with saline: 35.4+/-2.2 units, P<0.05), but significantly improved its acute reversibility (-42+/-4 compared with -25+/-4%, P<0.001). We conclude that GIK pretreatment attenuates the effect of ischaemia on myocardial contractility, slightly improves exercise tolerance and causes a more rapid and diffuse recovery of post-ischaemic reperfusion.

Glucose-insulin-potassium echocardiography detects improved segmental myocardial function and viable tissue shortly after acute myocardial infarction

Previous studies showed that glucose-insulin-potassium (GIK) increases cardiac output in patients after cardiac surgery and improves segmental myocardial wall motion. We hypothesized that GIK improves regional wall motion, detects contractile reserve, and predicts functional recovery at follow-up to a similar extent as low-dose dobutamine (LDD) in patients with recent myocardial infarction. Forty-one patients underwent LDD and GIK echocardiography. Data were analyzed according to a 13-segment model. Segments were scored from 0 (normokinesia) to 2 (a-/dyskinesia). Wall motion score index was calculated for baseline and intervention. During GIK, wall motion score index improved from 0.60 +/- 0.25 to 0.39 +/- 0.20 (P < .0001) and from 0.58 +/- 0.25 to 0.39 +/- 0.21 (P < .0001) during LDD. Overall agreement between GIK and LDD echocardiography to detect contractile reserve (improvement of segmental function by >or= 1 point) was 93% with a kappa value of 0.88. Sensitivity, specificity, and positive and negative predictive values of GIK echocardiography to predict functional recovery at follow-up (mean time to follow-up, 13 months) were 74%, 84%, 85%, and 72% respectively, and values were similar to LDD echocardiography. Thus, GIK infusion improves regional left ventricular function and allows the detection of myocardial viability to a similar extent as LDD in patients shortly after infarction.

The impact of glucose-insulin-potassium infusion in acute myocardial infarction on infarct size and left ventricular ejection fraction [ISRCTN56720616]

BACKGROUND

Favorable clinical outcomes have been observed with glucose-insulin-potassium infusion (GIK) in acute myocardial infarction (MI). The mechanisms of this beneficial effect have not been delineated clearly. GIK has metabolic, anti-inflammatory and profibrinolytic effects and it may preserve the ischemic myocardium. We sought to assess the effect of GIK infusion on infarct size and left ventricular function, as part of a randomized controlled trial.

METHODS

Patients (n = 940) treated for acute MI by primary percutaneous coronary intervention (PCI) were randomized to GIK infusion or no infusion. Endpoints were the creatinine kinase MB-fraction (CK-MB) and left ventricular ejection fraction (LVEF). CK-MB levels were determined 0, 2, 4, 6, 24, 48, 72 and 96 hours after admission and the LVEF was measured before discharge.

RESULTS

There were no differences between the two groups in the time course or magnitude of CK-MB release: the peak CK-MB level was 249 +/- 228 U/L in the GIK group and 240 +/- 200 U/L in the control group (NS). The mean LVEF was 43.7 +/- 11.0 % in the GIK group and 42.4 +/- 11.7% in the control group (P = 0.12). A LVEF < or = 30% was observed in 18% in the controls and in 12% of the GIK group (P = 0.01).

CONCLUSION

Treatment with GIK has no effect on myocardial function as determined by LVEF and by the pattern or magnitude of enzyme release. However, left ventricular function was preserved in GIK treated patients.

Insulin therapy in critically ill patients

PURPOSE OF REVIEW

The recent publication of the results of an aggressive approach to the treatment of hyperglycaemia in critically ill patients, and a rekindling of interest in the use of an infusion of glucose insulin and potassium as adjunctive therapy in a diverse group of patients with cardiovascular disease, warrants a review of the multiple effects of insulin and a review of laboratory and clinical studies.

RECENT FINDINGS

The use of an aggressive protocol to maintain normoglycaemia in critically ill patients has been demonstrated to be a beneficial technique in the critical care setting. Implementation of the protocol outside of a research setting appears to be feasible. Recent studies on the use of insulin in addition to glucose and potassium in patients with diverse cardiovascular diseases have also demonstrated positive results.

SUMMARY

This review will summarize some of the putative beneficial effects of insulin as a pharmacological agent, and review recent clinical data. Although the relative benefits of normoglycaemia in the critical care setting and the beneficial effects of insulin are difficult to differentiate, a substantial overlap exists. The extent to which these converging therapies (aggressive normoglycaemia and insulin pharmacotherapy) will be applicable to diverse clinical settings has yet to be determined.