Statistical analysis of ST segments in ECG signals for detection of ischaemic episodes

This paper highlights a new method for the detection of ischaemic episodes using statistical features derived from ST segment deviations in electrocardiogram (ECG) signal. Firstly, ECG records are pre-processed for the removal of artifacts followed by the delineation process. Then region of interest (ROI) is defined for ST segment and isoelectric reference to compute the ST segment deviation. The mean thresholds for ST segment deviations are used to differentiate the ischaemic beats from normal beats in two stages. The window characterization algorithm is developed for filtration of spurious beats in ischaemic episodes. The ischaemic episode detection is made through the coefficient of variation (COV), kurtosis and form factor. A bell-shaped normal distribution graph is generated for normal and ischaemic ST segments. The results show average sensitivity (Se) 97.71% and positive predictivity (+P) 96.89% for 90 records of the annotated European ST-T database (EDB) after validation. These results are significantly better than those of the available methods reported in the literature. The simplicity and automatic discarding of irrelevant beats makes this method feasible for use in clinical systems.

Administration of brain natriuretic peptide improves cardiac function following operations using extracorporeal circulation in an animal model

The critical phase during cardiosurgical procedures is weaning the diseased heart from the ECC (extracorporeal circulation). Post-ischaemic heart failure sometimes requires the administration of inotropic and/or vasconstrictive agents. The natriuretic peptides influence pre- and after-load through their natriuretic, diuretic and vasodilating actions. To date, there are only a few reports describing the therapeutic effect of BNP (brain natriuretic peptide) administration during cardiosurgical procedures. The aim of the present study was to evaluate the effect of BNP administration following ECC in an animal model. Surgery was performed on 20 pigs using ECC. A 30-min ischaemic episode was simulated. Following de-clamping, BNP was administered to the BNP group (n=10) by an i.v. (intravenous) bolus at 0.3 μg·kg−1 of body weight·min−1, followed by an infusion at a rate of 0.015 μg·kg−1 of body weight·min−1 for 60 min. The animals in the control group (n=10) received a saline solution instead of BNP. Haemodynamic and clinical chemistry parameters as well as the amount of catecholamines that were required were measured. All of the animals in the BNP group had a significantly better cardiac output and cardiac index at the end of the experiment. Seven out of 10 animals from the control group required catecholamines, whereas only one animal from the BNP group did. Creatine kinase levels were significantly lower in the BNP group. Systemic vascular resistance was markedly lower in the BNP group. In conclusion, administration of BNP is highly effective in treating post-ischaemic heart failure following ECC. Haemodynamics are greatly improved, and there is almost no need for pharmacological support.

Anti-arrhythmic actions of polyunsaturated fatty acids in cardiac muscle exerted via the sarcoplasmic reticulum

Cardiac arrhythmias can be triggered from ischaemic cardiac muscle due to the damage inflicted on individual myocytes. During an ischaemic episode free fatty acids accumulate in the ischaemic tissue. The importance of these fatty acids lies in the apparent ability of some classes of fatty acid to protect against cardiac arrhythmias. As cardiac sudden death is a likely cause of death in patients who have suffered an initial ischaemic insult, protection against such arrhythmias may be of crucial importance. The following review discusses how this protection may be produced, dealing specifically with changes in electrophysiological properties of cells and intracellular calcium regulation.

Cerebrovascular disease and oxidative stress

There is strong indirect evidence that free radical production appears to be an important mechanism of brain injury after exposure to ischaemia and reperfusion. Although significant brain damage occurs during an ischaemic episode, new cerebral damage can occur after reperfusion. One proposed mechanism for the brain damage that occurs during reperfusion involves generation of free radicals. Body defences against free radicals depends on the balance between free radical generation and the antioxidant protective defence system. Many of these protective antioxidants are essential nutrients or have essential nutrients as part of their molecule that has to be obtained from diet.

Endothelin-Mediated Vascular Tone following Focal Cerebral Ischaemia in the Cat

The actions of Bosentan and PD155080, non-peptide endothelin receptor antagonists, were examined in feline pial arterioles in situ following middle cerebral artery (MCA) occlusion to gain insight into the cerebrovascular influence of endogenous endothelins in focal cerebral ischaemia. Immediately following permanent MCA occlusion, all pial arterioles overlying the suprasylvian and ectosylvian gyri displayed marked dilatations, which were maintained in a population of vessels but differentiated into sustained constrictions in others. Perivascular subarachnoid microinjections of Bosentan (30 μ M), PD155080 (30 μ M), and artificial CSF (pH 7.2) were performed between 30 and 210 min following MCA occlusion. The perivascular microapplication of Bosentan (30 μ M) and PD155080 (30 μ M) around pial vessels overlying the suprasylvian and ectosylvian gyri, which are within the territory of the occluded MCA, elicited an increase in the calibre of postocclusion dilated and constricted pial arterioles. The perivascular microapplication of PD155080 (30 μ/ M) around postocclusion constricted arterioles overlying the ectosylvian and suprasylvian gyri elicited an increase in the calibre of arterioles (69 ± 49% from preinjection baseline; n = 8). The perivascular microapplication of Bosentan (30 μ M) around postocclusion constricted arterioles overlying the ectosylvian and suprasylvian gyri also elicited an increase in the calibre of arterioles (68 ± 60% from preinjection baseline; n = 13). In contrast, the microapplication of CSF (pH 7.2) elicited small reductions in pial arteriolar calibre of postocclusion constricted arterioles (—8 ± 13% from preinjection baseline; n = 8). The perivascular microapplication of PD155080 (30 μ M) around postocclusion dilated pial arterioles overlying the ectosylvian and suprasylvian gyri elicited an increase in the calibre of arterioles (11 ± 10% from preinjection baseline; n = 38). The perivascular microapplication of Bosentan (30 μ M) around postocclusion dilated arterioles elicited an increase in the calibre of arterioles (16 ± 15% from preinjection baseline; n = 36). In contrast, the microapplication of CSF (pH 7.2) elicited small reductions in pial arteriolar calibre of postocclusion dilated arterioles (—9 ± 6% from preinjection baseline; n = 44). Perivascular microapplication of Bosentan or PD155080 had minimal effect on the calibre of pial arterioles on the parasagittal gyrus (anterior cerebral artery territory), although these arterioles had also displayed sustained dilatation following MCA occlusion. These results indicate that contractile factors (whose effects can be reversed with endothelin receptor antagonists) constrict or impair dilatation of cortical resistance arterioles in an acute cerebral ischaemic episode.

Origins of endogenous noradrenaline overflow during reperfusion of the ischaemic rat heart

1. Reperfusion of the globally ischaemic isolated rat heart is associated with an enhanced overflow of endogenous noradrenaline (NA) after ischaemic periods of 20, 40 or 60 min but not of 10 min. 2. Reperfusion NA overflow, after 40 min of ischaemia, is suppressed by desipramine and increased when ischaemia follows a period of substrate deprivation. 3. Reperfusion after 40 min of ischaemia is associated with a significant rise in NA concentration despite a simultaneous 20-fold increase in flow. This increase in concentration is abolished by treatment with desipramine or if ischaemia follows a period of substrate deprivation. 4. Reperfusion NA overflow correlates with the reperfusion overflow of an extracellular space marker infused before the ischaemic episode. 5. These results suggest that ischaemia is heterogeneous and that NA is released into regions of particularly profound ischaemia from which it is subsequently eluted during reperfusion.

Intravenous Nitroglycerin during Surgery for Coronary Artery Disease

Intravenous infusions of nitroglycerin decreased systemic systolic, pulmonary systolic and wedge pressures in β-blocked patients anaesthetised for coronary artery surgery with high dose of fentanyl without changing heart rate, diastolic pressure, or cardiac index, thus leading to an improvement in endocardial viability ratio. The use of a nitroglycerin bolus to abort an acute myocardial ischaemic episode is described.