Myocardial oxygen consumption: The quest for its determinants and some clinical fallout

Type 2 myocardial infarction due to supply-demand mismatch

The best-accepted definition of myocardial infarction (MI) is provided by statements from the Universal Definition of MI Global Task force. This article, now in its third iteration, defines MI as myocardial cell death due to prolonged myocardial ischemia. It further delineates an increasingly incident subclassification of MI known as type 2 MI (T2MI). T2MI identifies instances of myocardial necrosis in which an imbalance between myocardial oxygen supply and/or demand occurs for reasons other than atherosclerotic plaque disruption. While associated with considerable risk (comparable to that of type 1 MI, which has well-defined management strategies), the spectrum of potential etiologies for T2MI makes development of precise diagnostic criteria and therapeutic implications of the diagnosis challenging.

Clozapine-induced cardiotoxicity in rats: Involvement of tumour necrosis factor alpha, NF-κβ and caspase-3

Clozapine, an ideal antipsychotic drug for the treatment of resistant schizophrenia, is considered the most underutilised treatment for schizophrenia. However, safety concerns have been raised about clozapine-induced cardiotoxicity, which may lead to sudden death, particularly in young patients. The exact mechanism of clozapine cardiotoxicity has not yet been thoroughly studied. This study aimed to investigate the possible mechanisms of clozapine-induced cardiotoxicity in a rat model. Young male Wistar rats were treated with clozapine (10, 15 and 25 mg/kg/day, i.p.) for 21 days. Haemodynamic and echocardiographic studies were performed for assessment of cardiac functions. Heart sections were studied histopathologically and immunohistochemically. Serum and cardiac markers of cardiotoxicity, oxidative stress, inflammation and apoptosis were evaluated. Heart sections of CLZ-treated animals showed increased cardiac inflammation that correlated with the clozapine dose. Serum levels of CK-MB and LDH levels increased, as did cardiac levels of TNF-α, MDA, NO, myeloperoxidase (MPO), 8-OHdG, caspase-3 and NF-κB p65. In contrast, GSH levels and GSH-Px activity decreased. Furthermore, immunohistochemical examination of the heart sections showed positive immunostaining for both 3-nitrotyrosine and caspase-3 in all clozapine-treated groups. Clozapine, particularly in relatively high doses, has a clear cardiotoxic effect. This cardiotoxicity is accompanied by increased myocardial oxidative stress, inflammatory cytokines, DNA damage and apoptosis with attenuation in antioxidant defences, thus explaining the previously reported myocarditis and pericarditis during clozapine therapy in clinical studies.

Reproducibility of intravascular ultrasound and intracoronary Doppler measurements

The aim of this study was to evaluate the reproducibility of intravascular ultrasound (IVUS) and intracoronary (IC) Doppler flow velocity measurements. The use of IVUS and IC Doppler has been suggested as a means for percutaneous coronary intervention (PCI) guidance in a series of studies. This would require an acceptable level of accuracy and reproducibility of these two methods for lesion evaluation. In this study, the main focus was on the issue of reproducibility. One hundred and eight patients referred for PCI entered into the study. Inter- and intraobserver variability was measured. Catheter difference was assessed. On-line and off-line measurements were compared. MUSIC criteria were assessed off-line, twice. Calculated and measured diameters were compared. After having obtained initial IC Doppler measurements, the Doppler wire was immediately withdrawn and repositioned for reacquisition of Doppler measurements. IVUS measurements are reproducible and reliable off-line and, to a slightly lesser degree, on-line. Area measurements should be performed more than once and the mean used for vessel description. Lumen diameters should be calculated from the mean of the area measurements. A measuring technique consensus should be reached and adhered to. CFR measurements can be used to determine reduced vs. normal flow reserve. In this study, it was found that proximal to distal velocity ratio and diastolic to systolic velocity ratio variability made these parameters unsuitable for PCI guidance.

Cost-effectiveness analysis of intravascular ultrasound guided percutaneous coronary intervention versus conventional percutaneous coronary intervention

OBJECTIVE

Investigation of the cost-effectiveness of intravascular ultrasound (IVUS) guided percutaneous coronary intervention (PCI) compared to PCI guided by coronary angiography (CAG).

METHODS

One hundred and eight men referred for PCI, were randomized to IVUS or CAG guided PCI. After 6 months, the patients were subjected to a study related clinical and invasive follow-up investigation by CAG, IVUS and intracoronary Doppler flow measurements. Incremental costs of IVUS guided procedures and costs of re-interventions were estimated using the Activity Based Costing (ABC) method.

RESULTS

Patients randomized to IVUS guided PCI experienced an improved clinical outcome, with lower angina levels than patients in the CAG guided group. The initial cost of performing IVUS guidance was increased due to extra procedure time, IVUS catheters and slightly more balloons and stents, but fewer patients in the IVUS guided group needed re-intervention. Overall, these savings outweighed the initial cost increase.

CONCLUSION

Our data suggest that when performing IVUS guided PCI, costs as well as benefits increase. The increased benefits measured as cost savings resulting from less restenosis outweigh the cost increase from performing the IVUS guided PCI as opposed to CAG guided PCI.