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PubMed1978

[Evaluation of blocking and activation response of focal EEG abnormalities by opening and closing the eyes (author's transl)].

Blocking and activation of constant focal EEG abnormalities by opening and closing the eyes were assessed by visual analysis in 173 EEG recordings of 173 patients. Correlations between single variable were weak in general and did not gain statistical significance in any case. The blocking response had similar extent on both hemispheres. There was no sign of direct dependence from extra- or intracerebral localisation of the causal process. However, the biplot method of computing the results discovered several constellations of variables responsible for blocking and activation. Two of them are reported here. 1) Both responses were more prominent at frontal than at occipital areas. 2) A prodominant slowing localized in mainly frontal regions on the left hemisphere and caused by a process extending from extracerebral or cortical to subcortical showed the greatest tendency to be blocked by opening the eyes while the cause of the focus had no influence.

Alpha Rhythm↗

PubMed1991

Influence of exercise-induced myocardial ischemia on the pattern of left ventricular diastolic filling: a Doppler echocardiographic study.

Previous studies using Doppler echocardiography to evaluate left ventricular diastolic filling have shown that myocardial ischemia induced by coronary balloon angioplasty or atrial pacing results in a decrease in the left ventricular inflow peak early (E) to peak atrial (A) velocity ratio. To investigate the effects of exercise-induced ischemia on Doppler-derived filling variables, 20 patients with coronary artery disease and exercise-induced electrocardiographic changes and regional wall motion abnormalities determined by two-dimensional echocardiography were evaluated and compared with 20 patients without evidence of exercise-induced ischemia. Doppler echocardiography was performed at rest and immediately after exercise before the resolution of exercise-induced wall motion abnormalities. Peak E and A velocities increased from rest to postexercise in both the ischemic and nonischemic groups, although the ischemic group demonstrated a greater increase in peak E velocity (from 68 +/- 15 cm/s at rest to 88 +/- 22 cm/s after exercise) than the nonischemic group (70 +/- 13 to 77 +/- 18 cm/s) (p less than 0.05 for the difference in response between groups). Accompanying these changes was a slight increase in the peak E/A velocity ratio in the ischemic group (1.04 +/- 0.28 at rest to 1.13 +/- 0.42 after exercise) versus a decrease in the nonischemic group (1.07 +/- 0.30 to 0.90 +/- 0.28) (p less than 0.05 intergroup difference).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗

PubMedDate not supplied

Lung uptake of technetium 99m sestamibi: relation to clinical, exercise, hemodynamic, and left ventricular function variables.

BACKGROUND: Technetium 99m sestamibi (2-methoxyisobutyl isonitrile [MIBI]) is a relatively new radiopharmaceutical with improved imaging characteristics for exercise myocardial perfusion studies compared with thallium 201. Although increased lung uptake of 201Tl has been shown to have important clinical significance, reflecting severity of coronary artery disease and left ventricular function, the factors affecting MIBI lung uptake are unknown. Therefore we examined the potential clinical, exercise, hemodynamic, myocardial perfusion, and ventricular function determinants of lung uptake of MIBI on exercise myocardial perfusion studies. METHODS AND RESULTS: The study cohort consisted of 103 patients referred for evaluation of coronary artery disease with exercise MIBI myocardial perfusion imaging. All patients underwent both a standard 1-day rest-stress MIBI planar imaging protocol and rest echocardiography. With the anterior-view stress images obtained 1 hour after MIBI injection, regions of interest were drawn over peak lung and myocardial activities and a lung/heart ratio was calculated. Multivariate regression analysis was used to relate the lung/heart ratio to clinical, exercise and hemodynamic, myocardial perfusion, and echocardiographic left ventricular function scores. We found no significant relation between lung/heart ratio and any patient variable. CONCLUSIONS: Unlike 201Tl, lung uptake of MIBI is not related to indexes of exercise, left ventricular dysfunction, or perfusion abnormalities. Thus MIBI lung uptake does not appear to have the same clinical significance as 201Tl lung uptake.

Adult↗

PubMed1987

Effects of pacing-induced ischemia on early left ventricular filling and regional myocardial dynamics and their modification by nifedipine.

The effect of pacing-induced ischemia on early left ventricular filling and regional myocardial lengthening was studied in 11 patients with coronary artery disease (CAD) and six control patients with normal coronary arteriograms. All of the 11 patients with CAD developed typical anginal pain during pacing tachycardia, and in the postpacing beat, the left ventricular end-diastolic pressure (LVEDP) rose from 13 +/- 4 to 26 +/- 4 mm Hg (mean +/- SD, p less than .01), the relaxation time constant increased from 43 +/- 9 to 59 +/- 7 msec (p less than .01), and the ejection fraction diminished from 62.1 +/- 6.7 to 51.6 +/- 10.6% (p less than .01). However, the peak rate of early left ventricular filling (LVPF) obtained from frame-by-frame analysis of left ventriculograms and the LVPF normalized for the stroke volume and for the end-diastolic volume did not change significantly. In the ischemic segment, the peak rate of lengthening (PL) decreased by 45% with ischemia, and the PL normalized for the end-diastolic segment length decreased by 42%. However, the PL normalized for the extent of systolic shortening did not change. In the control segment there was a tendency for these three variables to increase, but the changes were not statistically significant. The time difference from the PL to the LVPF increased significantly in the ischemic segment (31 +/- 28 vs 75 +/- 48 msec, p less than .05). Although the LVEDP rose slightly but significantly from 9 +/- 3 to 12 +/- 5 mm Hg (p less than .05) in the control patients in the postpacing beat, the other global hemodynamic variables and the variables of regional myocardial dynamics did not change. The administration of nifedipine in six patients with CAD resulted in the disappearance or diminution of anginal pain even with the same duration and rate of pacing and was associated with restoration of global systolic function and regional myocardial shortening and lengthening in the ischemic segment. In the control segment, the three variables of segmental lengthening increased with administration of nifedipine. Thus, the segmental myocardial lengthening rate decreased with ischemia due to a decrease in segmental shortening and impairment of myocardial distensibility. The LVPF did not decrease with ischemia despite impairment in isovolumetric relaxation, accentuation of asynchrony in left ventricular filling, and a decrease in the PL in the ischemic segment because of an increase in the PL in the nonischemic segment secondary to an increase in left ventricular filling pressure.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1999

Regional differences of cerebral hemoglobin concentration in preterm infants measured by near infrared spectrophotometry.

Near infrared spectrophotometry has been used to measure total cerebral hemoglobin concentration (micromol/l) as a major indicator of the oxygen transport capacity in neonates. The aim of this study was to find out how the position of the probe influences the quality of the measurement and the actual cerebral hemoglobin concentration-values. We studied 10 healthy preterm infants with a mean gestational age of 31.5 weeks and a birthweight of 1513 g. The data were collected by a two channel near infrared spectrophotometry system using a geometrical principle to measure absolute cerebral hemoglobin concentration. The incoming signal of the light emitting diode as a value allows a prediction of the quality of the measurement: a high value refers to a high signal/noise ratio. Starting from the centre of the forehead (0%) for each measurement the probe was moved by 2.5% of the headcircumference to the left respectively right side of the head up to 20%. The cerebral hemoglobin concentration-values increased from 87 respectively 93 micromol/l up to 164 respectively 173 micromol/l on the right respectively left side, while the light emitting diode signal-values decreased from 21 respectively 21 down to 10 respectively 11, the more laterally the probe was moved. There were two plateaus of these variables in the frontal (0-5%) respectively lateral (15-20%) region. A further investigation on a solid phantom for premature heads showed that hair has either no or a contrary effect on the cerebral hemoglobin concentration-values than expected. The extracerebral tissue (soft tissue, skull, cerebrospinal fluid layer) is discussed to have a significant influence on the light attenuation in adult heads. Still there is no evidence for a significant effect on prematures, because this overlying tissue is much thinner and more translucent than the one in adults. Absolute cerebral hemoglobin concentration measured by near infrared spectrophotometry is substantially influenced by the position of the probe at the infant's head. Considering our results we recommend placing the probe at 2.5% of the headcircumference away from the centre of the forehead for the measurement of cerebral hemoglobin concentration in premature infants.

Brain↗

PubMed1985

Retroperitoneal paraganglia and the peripheral autonomic nervous system in the human fetus.

By means of the AChE in toto staining method retroperitoneal paraganglia and the peripheral autonomic nervous system in human fetuses have been investigated. Many small retroperitoneal paraganglia are present near the sympathetic trunks close to the sympathetic trunk ganglia. In the thoracic region small paraganglia are present in the intercostal spaces. Small splanchnic nerves entering small paraganglia have been described. In the lower sacral region no paraganglia are present. The major splanchnic nerve arises at various levels from the sympathetic trunks as well as many smaller thoracic splanchnic nerves. Intermediate ganglia are present in the major splanchnic nerve, the smaller splanchnic nerves and the communicating rami. In the sympathetic trunks many ganglia are fused. In the human fetus there exists a large variability in number and diameter of the communicating rami. Interconnecting bundles of nerve fibers between the left and right sympathetic trunks are present at all levels, but most numerous at the sacral level.

Autonomic Nervous System↗

PubMed1996

Amrinone reverses bupivacaine-induced regional myocardial dysfunction.

Amrinone has been shown to have therapeutic effects on bupivacaine-induced cardiovascular toxicity, but its exact effects on the heart are not well understood. This study evaluated the regional myocardial effect of amrinone on bupivacaine-induced cardiovascular toxicity in in situ beating hearts in 10 dogs using a selective coronary perfusion and sonomicrometry. In the control group, bupivacaine was administered into the left anterior descending coronary artery (LAD) for 15 min at four steps: baseline, step 1, step 2 and step 3, (calculated LAD plasma concentrations; 0, 5, 5 and 10 mu g center dot ml-1, respectively). In the amrinone group, amrinone (5 mu g center dot ml-1) was simultaneously infused at steps 2 and 3 in addition to bupivacaine infusions. Regional myocardial function of the LAD supplied area was evaluated by analysis of the left ventricular pressure-segment length loop. In the control group, systolic shortening decreased from the baseline (10.5 +/- 1.3%, mean +/- SEM) to step 3 (0.1 +/- 1.3%), and post-systolic shortening increased from the baseline (18.0 +/- 3.7%) to step 3 (52.3 +/- 5.5%) dose-dependently. In contrast, with amrinone infusion at steps 2 and 3, both variables returned to near baseline values. These results indicate that amrinone reverses bupivacaine-induced regional myocardial dysfunction.

Amrinone↗

PubMedDate not supplied

Relation of myocardial perfusion at rest and during pharmacologic stress to the PET patterns of tissue viability in patients with severe left ventricular dysfunction.

BACKGROUND: Stress perfusion imaging can assess effectively the amount of jeopardized myocardium, but its use for identifying underperfused but viable myocardium has yielded variable results. We evaluated the relation between measurements of myocardial perfusion at rest and during pharmacologic stress and the patterns of tissue viability as determined by positron emission tomographic (PET) imaging. METHODS AND RESULTS: We studied 33 patients with coronary artery disease and left ventricular (LV) dysfunction (LV ejection fraction, 30%+/-8%). PET imaging was used to evaluate regional myocardial perfusion at rest and during pharmacologic stress with [13N]-ammonia as a flow tracer, and to delineate patterns of tissue viability (i.e., perfusion-metabolism mismatch or match) using [18F]-deoxyglucose (FDG). We analyzed 429 myocardial regions, of which 229 were dysfunctional at rest. Of these, 30 had normal perfusion and 199 were hypoperfused. A severe resting defect (deficit >40% below normal) predicted lack of significant tissue viability; 31 of 35 regions (89%) had a PET match pattern denoting transmural fibrosis. Although regions with mild or moderate resting defects (deficit <40% below normal) showed evidence of metabolic activity, perfusion measurements alone failed to identify regions with PET mismatch (reflecting hibernating myocardium). Reversible stress defects were observed with slightly higher frequency in regions with a PET mismatch (10 of 37) than in those with a PET match (36 of 162) pattern of viability. A reversible stress defect was a specific (78%) marker, but was a relatively insensitive marker (27%) of viable myocardium as defined by the PET mismatch pattern. CONCLUSIONS: In patients with LV dysfunction, the severity of regional contractile abnormalities correlates with the severity of flow deficit at rest. Severe reductions in resting blood flow in these dysfunctional regions identify predominantly nonviable myocardium that is unlikely to have improved function after revascularization. Although dysfunctional myocardium with mild to moderate flow reductions contains variable amounts of viable tissue (as assessed by FDG uptake), flow measurements alone do not distinguish between regions with PET mismatch (potentially reversible dysfunction) and PET match (irreversible dysfunction). The presence of an irreversible defect on stress imaging is a relatively specific (78%) marker of PET match, whereas a reversible stress defect is a rather insensitive (27%) marker of viability, as defined by the PET mismatch pattern.

Aged↗

PubMedDate not supplied

Validation of a new counts-based gated single photon emission computed tomography method for quantifying left ventricular systolic function: comparison with equilibrium radionuclide angiography.

BACKGROUND: Because myocardial wall thickness is smaller than the spatial resolution of single photon emission computed tomography (SPECT) imaging, changes in myocardial wall thickness are related to changes in maximum pixel counts via the partial volume effect, allowing for quantification of regional systolic wall thickening. We have developed a new gated SPECT method for computing the global left ventricular ejection fraction (LVEF) based entirely on changes in maximum regional myocardial counts during systolic contraction. This new method is independent of endocardial edge detection or other geometric measurements. METHODS AND RESULTS: In 23 patients the gated SPECT method was validated by comparison with radionuclide angiography. The correlation between computed LVEFs was excellent (slope = 0.97, r = 0.91). The measurement of LVEF by gated SPECT was highly reproducible, with minimal intraoperator (slope = 0.97, r = 0.97) or interoperator (slope = 1.00, r = 0.97) variability. Measurements of regional thickening indexes were also reproducible, with a mean intraoperator correlation coefficient of 0.89 +/- 0.05 (range 0.79 to 0.95) for the 14 myocardial regions. Finally, the measurement of LVEF was not significantly influenced by changes in reconstruction filter parameters over a range of cutoff frequencies from 0.16 to 0.28. CONCLUSIONS: This new counts-based gated SPECT method for measuring global left ventricular systolic function correlates well with radionuclide angiography, is highly reproducible, and has theoretic advantages over geometric methods.

Adult↗

PubMed2005

Finger tapping, handedness and grey matter amount in the Rolando's genu area.

The morphology of the central sulcus (CS), at the level of the hand primary motor cortex, has been shown to be related to hand preference and skill. Differences in the cerebral functional organisation of left and right-handers have been described, notably with respect to hemispheric specialisation, which might cause the neural substrate of hand dominance or skill to differ between the two groups. Here, we further explored the relationship between the anatomical variability of the central sulcus and hand skill in two groups of young male subjects differing by handedness (n = 56 right-handers and n = 55 left-handers). Grey matter volume (GMV) in the upper region of the central sulcus was estimated with Voxel Based Morphometry, using a probabilistic region of interest approach, while hand motor skill was measured with the finger tapping test. No significant anatomical differences could be evidenced between the two hand preference groups, a rightward hemispheric asymmetry being observed in both samples. However, multiple regression analyses showed that, in the right-handed group, the maximum tapping rate of the right hand correlated positively with the left central sulcus GMV, but negatively with the right. Similar analyses showed that, in left-handers, the maximum tapping rate of the non-dominant right hand was strongly correlated with the GMV of the ipsilateral CS but not significantly with that of the contralateral CS. These results may be due to differences in the organisation of motor systems between these two groups, possibly concerning a left hemispheric specialisation for fast repetitive movements in right-handers, which would be different in left-handers.

Adult↗

PubMed2004

A replication study of the neural correlates of deception.

The authors attempted to replicate prior group brain correlates of deception and improve on the consistency of individual results. Healthy, right-handed adults were instructed to tell the truth or to lie while being imaged in a 3T magnetic resonance imaging (MRI) scanner. Blood oxygen level-dependent functional MRI significance maps were generated for subjects giving a deceptive answer minus a truthful answer (lie minus true) and the reverse (true minus lie). The lie minus true group analysis (n = 10) revealed significant activation in 5 regions, consistent with a previous study (right orbitofrontal, inferior frontal, middle frontal cortex, cingulate gyrus, and left middle frontal), with no significant activation for true minus lie. Individual results of the lie minus true condition were variable. Results show that functional MRI is a reasonable tool with which to study deception.

Adolescent↗

PubMed1993

Cardiovascular consequences of correction of the anemia of renal failure with erythropoietin.

The purpose of this study was to define the physiologic responses of the heart and peripheral circulation to chronic anemia using noninvasive measurements while eliminating confounding biochemical, pharmacologic and physiologic variables. Stable chronic hemodialysis patients were studied at the University Hospital based chronic dialysis unit and echocardiography laboratory before and after therapy with human recombinant erythropoietin (rHuEPO). Subjects included maintenance hemodialysis patients free of left ventricular regional wall motion abnormalities discernible by echocardiography, rhythm disturbance, significant valvular or ischemic heart disease. Two-dimensional echocardiograms and simultaneous targeted M-mode echocardiograms, phonocardiograms and externally acquired subclavian artery pulse tracings were used to measure whole blood viscosity, arterial blood gases and ionized calcium, complete blood count, electrolytes, creatinine, blood urea nitrogen (BUN), and inorganic phosphate. All measurements were made immediately post-dialysis before and after therapy with rHuEPO. The interval between pre- and post-rHuEPO studies was 8.3 +/- 2.3 months. We found that post-dialysis hematocrit rose from 24.7 +/- 0.9 to 36.4 +/- 0.9%, hemoglobin from 83 +/- 3 to 121 +/- 3 g/liter and whole blood viscosity from 2.87 +/- 0.11 to 3.71 +/- 0.18 centipoise (all, P < 0.001 after therapy with rHuEPO). The remaining biochemical measurements did not change. Heart rate fell from 83 +/- 3 to 77 +/- 3 beats/min (P = 0.013). Left ventricular preload and afterload were not statistically different before and after rHuEPO. Total vascular resistance rose from 1313 +/- 84 to 1568 +/- 129 dynes.sec.cm-5, P = 0.029. Cardiac output and cardiac index fell by 12 and 15% (P = 0.024 and 0.030), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2005

Regional deficits in brain volume in schizophrenia: a meta-analysis of voxel-based morphometry studies.

OBJECTIVE: Voxel-based morphometry is a method for detecting group differences in the density or volume of brain matter. The authors reviewed the literature on use of voxel-based morphometry in schizophrenia imaging research to examine the capabilities of this method for clearly identifying specific structural differences in patients with schizophrenia, compared with healthy subjects. The authors looked for consistently reported results of relative deficits in gray and white matter in schizophrenia and evaluated voxel-based morphometry methods in order to propose a future strategy for using voxel-based morphometry in schizophrenia research. METHOD: The authors reviewed all voxel-based morphometry studies of schizophrenia that were published to May 2004 (15 studies). The studies included a total of 390 patients with a diagnosis of schizophrenia and 364 healthy volunteers. RESULTS: Gray and white matter deficits in patients with schizophrenia, relative to healthy comparison subjects, were reported in a total of 50 brain regions. Deficits were reported in two of the 50 regions in more than 50% of the studies and in nine of the 50 regions in one study only. The most consistent findings were of relative deficits in the left superior temporal gyrus and the left medial temporal lobe. Use of a smaller smoothing kernel (4-8 mm) led to detection of a greater number of regions implicated in schizophrenia. CONCLUSIONS: This review implicates the left superior temporal gyrus and the left medial temporal lobe as key regions of structural difference in patients with schizophrenia, compared to healthy subjects. The diversity of regions reported in voxel-based morphometry studies is in part related to the choice of variables in the automated process, such as smoothing kernel size and linear versus affine transformation, as well as to differences in patient groups. Voxel-based morphometry can be used as an exploratory whole-brain approach to identify abnormal brain regions in schizophrenia, which should then be validated by using region-of-interest analyses.

Amygdala↗

PubMed1989

Cerebrocortical microdysgenesis in neurologically normal subjects: a histopathologic study.

Previous studies showed that few foci of cerebro-cortical microdysgenesis (molecular layer neuronal ectopias and focal laminar dysplasia) are present in up to 26% of variably processed normal brains; they are more common in the right inferior frontal region. Brains of male developmental dyslexics processed in serial histologic sections showed 30 to 140 foci of these types of anomalies, predominantly in left perisylvian cortex. Here, we present the results of a detailed analysis of ten normal brains also processed in serial sections. The ages ranged from 3.5 to 87 years, all male. Three brains showed abnormalities similar in type to those of the dyslexic, but in far smaller numbers and in different locations: two showed a single cingulate focus--one right, one left; the third brain showed two right supratemporal foci. We conclude that the present form of developmental anomaly is rare in normal brains, and that the findings in the dyslexic brains may be significant.

Adolescent↗

PubMed1998

Absence of normal activation of the left anterior fusiform gyrus during naming in left temporal lobe epilepsy.

Patients with left temporal lobe epilepsy (TLE) often have impaired naming. We studied 13 patients with left TLE and 10 healthy control subjects with [(15)O]H2O PET during visual confrontation naming. Statistical mapping detected multiple regions of significant cerebral blood flow increases within individuals. The left fusiform gyrus was activated in nine healthy subjects, but only in two patients with TLE (a significant difference, p < 0.001). Other activation sites were more variable in healthy subjects and those with TLE. Impaired naming ability may be associated with a lack of increased cerebral blood flow in the left fusiform gyrus in TLE.

Adolescent↗

PubMed1994

Electrophysiological mechanisms for postcardioplegia reperfusion ventricular fibrillation.

BACKGROUND: Reperfusion arrhythmias that follow regional ischemia at normothermia have been studied extensively and are considered to be a manifestation of ischemia-reperfusion injury. In contrast, reperfusion arrhythmias that occur following hypothermic cardioplegic arrest have received little attention from investigators. This study defines the electrophysiological mechanisms for postcardioplegia reperfusion ventricular fibrillation (RVF). METHODS AND RESULTS: The electrophysiology of postcardioplegia RVF was examined by using in situ porcine hearts. Complete heart block was created by using cryoablation before cardioplegic arrest so that isolated ventricular electrical activity could be observed for a prolonged time after reperfusion. Electrophysiological data were collected from limb leads, right atrial electrodes, and left ventricular electrodes in all 12 pigs. In 5 pigs, right and left ventricular endocardial electrograms were also recorded. A total of 103 episodes of RVF were analyzed. In 90 instances, an accelerating automatic ventricular focus initiated RVF. In five animals, RVF occurred after ventricular pacing (ie, purely re-entrant RVF). The mechanism for RVF was indeterminant in 8 instances. The origin of RVF was mapped in 44 instances. RVF usually originated in the left ventricle (25 instances) or septum (16 instances). CONCLUSIONS: Enhanced automaticity and re-entry are the mechanisms for postcardioplegia and regional ischemia-reperfusion arrhythmias. This finding supports the use of postcardioplegia RVF as a variable for comparing strategies for myocardial protection and suggests that information generated by the study of regional ischemia reperfusion arrhythmias can be used to understand postcardioplegia reperfusion arrhythmias and ischemia-reperfusion injury.

Animals↗

PubMed1984

Effects of atrial fibrillation on myocardial blood flow in the ischemic heart of the dog.

Atrial fibrillation has a variable effect on myocardial blood flow in the intact heart. To assess its action on myocardial blood flow in the ischemic heart, measurements were made in nine dogs after ligation of the left anterior descending coronary artery before and during atrial fibrillation and with atrial pacing at the average ventricular response during atrial fibrillation. During atrial fibrillation, cardiac output decreased (from 2.4 +/- 0.2 to 1.5 +/- 0.2 liters/min, p less than 0.001) and mean aortic pressure decreased (from 90 +/- 9 to 72 +/- 7 mm Hg, p less than 0.001). Mean myocardial blood flow decreased from 63 +/- 9 to 51 +/- 9 ml/min per 100 g. Although myocardial blood flow decreased in ischemic myocardium (from 28 +/- 5 to 16 +/- 2 ml/min per 100 g, p less than 0.001), in nonischemic myocardium the changes were more variable (from 71 +/- 8 to 61 +/- 8 ml/min per 100 g, p = NS). During atrial pacing, mean and nonischemic regional myocardial blood flow were comparable with that in atrial fibrillation, whereas in the ischemic region, myocardial blood flow (20.3 +/- 3 versus 14.6 +/- 2.3 ml/min per 100 g, p less than 0.01) and left ventricular inner/outer layer ratio (0.43 +/- 0.07 versus 0.32 +/- 0.06, p less than 0.05) were lower. ST segment elevation increased with both atrial fibrillation (by 89 +/- 31%, p less than 0.05) and atrial pacing (by 51 +/- 28%). Thus, atrial fibrillation has an unfavorable influence on myocardial blood flow in the ischemic heart and worsens myocardial ischemia. This effect is at least in part due to the rapid ventricular rate.

Animals↗

PubMed2000

Late post-myocardial infarction induces a tetrodotoxin-resistant Na(+)Current in rat cardiomyocytes.

Left ventricular remodeling after myocardial infarction is accompanied by electrical abnormalities that might predispose to rhythm disturbances. To get insight into the ionic mechanisms involved, we studied myocytes isolated from four different regions of the rat ventricles, 4-6 months after ligation of the left coronary artery. Using the whole-cell patch-clamp technique, we never observed T-type Ca(2+)current in both diseased and control hearts. In contrast, in 41 out of 78 cells isolated from 16 post-myocardial infarcted rats, analysed in the presence of 30 m m Na(+)ions, we found a tetrodotoxin (TTX)-resistant Na(+)current with quite variable amplitude in every investigated region. Albeit being resistant to 100 microM TTX, this Na(+)-dependent current was highly sensitive to lidocaine since 3 microM lidocaine induced about 65% tonic block. It was also inhibited by 5 microM nifedipine and 2 m m Co(2+), but was insensitive to 100 microM Ni(2+). The TTX-resistant Na(+)channel availability was shifted rightward by 25-30 mV with respect to TTX-sensitive Na(+)current; therefore, a large "window current" might flow in the voltage range from -70 to -20 mV. In conclusion, in late post-myocardial infarction, a Na(+)current with specific kinetics and pharmacology may provide inward charges in a critical range of membrane voltages that are able to alter action potential time course and trigger ventricular arrhythmia. These apparent new characteristics of the Na(+)channel might result in part from environmental changes during heart remodeling.

Animals↗