Attitudes to female roles, aspects of menstruation and complaining of menstrual symptoms

Mofidied limb electrode positions are often used in studies which require the recording of rest and exercise ECGs, whereby the arm electrodes are placed at the infraclavicular fossae and the left lef electrode on the left lower abdomen. The effect of the modified limb electrode positions on electrocardiographic waveforms was investigated in 68 supine adult male subjects at rest. The modification produced profound amplitude and waveform changes in the frontal plane ECG leads. The QRS axis shifted on the average by 16 degrees towards a more vertical position with considerable individual variation. Concomitant with the QRS axis shift, the R wave amplitude decreased in leads I and a VL and increased in leads II, III, and aVF. The S wave amplitude increased in leads III and aVF and decreased in lead III. The P and T wave amplitude changes were in a direction similar to those observed for the R waves: a reduction of the amplitude in aVL and an increase in II, III and aFV. Of importance to exercise ECG interpretation are the ST segment waveform changes: The ST slope decreased in aVL and increased in leads II, III and aVF. Waveform changes in the chest leads caused by the modification were less important although statistically significant. These systematic changes in recorded ECG waveforms arise from changes directions and strength of the lead vectors of the six frontal plane leads. Large inter-individual variations in the magnitude of the changes produced by modification of the limb electrode positions prevent effective systematic correction of the distortions by means of a universal lead transformation.     

An alternative limb lead system for electrocardiographs in emergency patients

It is occasionally difficult to record the standard 12-lead electrocardiograph (ECG) in emergency patients. The aim of this study was to evaluate the influence on electrocardiographic wave form recordings of moving the location of electrodes from the standard limb lead position to the trunk. The participants were 10 normal subjects and 20 patients with heart disease. In the new lead system, the limb electrodes were placed on the anterior acromial region and the anterior superior iliac spine using adhesive electrodes. Conventional 12-lead ECGs were recorded by the standard and the new lead system simultaneously in the supine position. Wave form analysis was done by an automatic analysis program. Motion artifacts in the recordings were less in the new lead system. The R wave amplitude of the new lead system increased in leads II, III and aVF, and decreased in leads I and aVL. However, the amplitudes of each wave obtained by standard electrocardiography and the new lead system correlated well (y = 1.008x + 2.038, r = 0.99, n = 2,880). In 99.6% of all wave forms, the differences in amplitudes were within 5% of the values of standard recordings. The average of differences in the ST-segment was 2.6 +/- 11.4 microV. The frontal plane QRS axis obtained by the new lead system showed a vertical shift of 7.8 +/- 8.5 degrees (y = 0.94911x + 10.346, r = 0.98, n = 30). The recording errors produced by the new lead system were within the permissible range of variation. The new lead system is a reasonable alternative for recording ECGs if application of the standard lead is difficult in an emergency.     

Left anterior and left posterior hemiblock in tricuspid atresia and transposition of the great vessels: observations and electrocardiographic nomenclature and electrophysiologic mechanisms

A patient with tricuspid atresia and characteristic electrocardiographic features of counterclockwise and superiorly oriented frontal plane QRS loop (left anterior hemiblock) is presented. Operative intervention resulted in a clockwise and inferior rotation of the frontal QRS loop (left posterior hemiblock) without the development of complete left bundle branch block. This observation suggests that the electrocardiographic pattern of left anterior hemiblock may result from other mechanisms in addition to block of the left bundle branch fibers oriented toward the anterior part of the left ventricle. The case further suggests that electrocardiographic patterns of apparent A-V conduction defects may not be at all associated with true block in the A-V conduction system. Further, it emphasizes the fact that various electrophysiologic mechanisms may account for identical electrocardiographic patterns.     

Evaluation of electrocardiographic left ventricular hypertrophy with both QRS voltage and ST-T change using echocardiography

The purpose of the present study is to determine whether electrocardiographic QRS voltage criteria with ST-T change is useful in the diagnosis of left ventricular hypertrophy (LVH) using echocardiography. One hundred men including 59 with hypertension (HT), 9 with hypertrophic cardiomyopathy (HCM), and 32 without any cardiovascular disease were enrolled in this study. All of them had the electrocardiographic evidence of LVH by Sokolow-Lyon voltage criteria (RV5 or RV6 > 2.6 mV, SV1+RV5 or SV1+RV6 > or = 3.5 mV). They were classified into three groups based on ST-T pattern as follows: Normal ST-T (group N): normal ST-T in twelve leads; Early strain ST-T (group ES): ST depression, flat T (T/R < 1/10), diphasic T or T wave inversion < 0.1 mV in V5 or V6; and Strain ST-T (group S): inverted T wave in V5 and V6. Echocardiographic LVH was determined when either interventricular septal thickness (IVST) or left ventricular posterior wall thickness (LVPWT) > or = 12 mm was present. According to this echocardiographic evidence, 31.7%(20/63) of group N, 75.0% (12/16) of group ES, and 100% (21/21) of group S were diagnosed. There were significant correlations between QRS voltage indices (RV5, RV6, SV1+RV5 and SV1+RV6) and IVST, (IVST+LVPWT)/2, and LV mass in group S(r = 0.650 to 0.858, p < 0.05) but not in group N. Values for IVST and LV mass were significantly greater in group S than in group ES or N. The electrocardiographic diagnosis of LVH with both QRS voltage and ST-T change thus appeared to be more useful than that with QRS voltage criteria alone.     

Effects of antipyrine on umbilical and regional metabolism in late gestation in the fetal lamb

OBJECTIVE: Antipyrine has been used extensively in fetal metabolic studies and is now known to inhibit prostaglandin synthesis; therefore we wished to determine the effects of antipyrine on fetal umbilical and regional metabolism. STUDY DESIGN: Chronically catheterized fetal lambs were randomly assigned to antipyrine (n = 6) or control (n = 5) groups. Animals in the antipyrine group were infused with antipyrine (mean +/- SD 9.6 +/- 0.9 mg/min for 165 +/- 38 minutes), and control group animals were not infused. Measurements were made of fetal blood gases, oxygen content, glucose, lactate, lower-body blood flow, upper-body flow distribution, and substrate uptakes across the umbilical and hind limb circulations. The unpaired t test, correlation coefficient, and regression analysis were used for comparisons. RESULTS: There were no differences in antipyrine and control group animals with respect to blood gases, metabolite levels, umbilical blood flow, or umbilical uptakes. Hind limb blood flow (p < 0.10) and oxygen uptake (p < 0.05) were lower and lactate production was higher (p < 0.01) in antipyrine animals than in control group animals. Duration of antipyrine exposure correlated directly with hind limb lactate production (r = 0.85, p < 0.001) and inversely with hind limb oxygen uptake (r = -0.65, p < 0.05). The distribution of blood flow within the fetal upper body also differed between groups, with higher cardiac distribution in the antipyrine group (p < 0.025). CONCLUSIONS: Antipyrine does not affect umbilical metabolism but does affect carcass metabolism and fetal blood flow distribution.     

Vectorcardiographic diagnosis of diaphragmatic myocardial infarction

Vectorcardiograms of 31 patients with arteriographic evidence of complete occlusion of the right coronary artery were analyzed in order to evaluate and attempt to improve the vectorcardiographic criteria for the diagnosis of an old diaphragmatic myocardial infarction. The electrocardiogram showed no evidence of a diaphragmatic infarction in 48 percent of these patients. This was advantageous, since the intent of the study was to develop vectorcardiographic criteria that exceeded the capability of the electrocardiogram. The criteria that appeared optimal were: (1) an instantaneous 0.02 second QRS vector equal or superior to 315 degrees (-45 degrees) in the sagittal plane, or (2) ratio of voltages of 0 to left x-intercept to maximal QRS vector greater than 0.22 in the frontal plane. These criteria identified a diaphragmatic infarction in 77 percent of patients (24 of 31) with complete occlusion of the right coronary artery. There were no false positive findings in 40 normal subjects. A group of criteria previously defined by others, based upon rotation, contour of initial forces, duration of superior forces relative to the contour, magnitude of 0 to left x-intercept, and maximal QRS vecotr, was equally sensitive. Other previously defined criteria were less sensitive. The criteria developed in this study, when tested in 22 patients with prominent Q waves indicative of an old diaphragmatic infarction, properly diagnosed the infarction in all 22 patients. All previous criteria also successfully detected infarction in these patients. However, the new criteria identified a greater number of patients without electrocardiographic evidence of diaphragmatic infarction than were identified with previously defined vectorcardiographic criteria unless the latter were complex.     

Left ventricular lesions in arrhythmogenic right ventricular dysplasia and 12-lead electrocardiographic findings

Left ventricular lesions in arrhythmogenic right ventricular dysplasia have not been well described, and the relationship between the left ventricular lesions and the 12-lead electrocardiographic findings has not been analyzed. This study examined whether the presence of left ventricular lesions and the extent of right ventricular lesions due to arrhythmogenic right ventricular dysplasia are predictable by 12-lead electrocardiographic findings. The 12-lead electrocardiograms during sinus rhythm and left and right ventriculography were studied in 29 patients (27 males and 2 females, mean age 42.6 +/- 15.5 years) diagnosed by the current criteria for this disease. After evaluation, patients were divided into two groups: those with normal left ventricles (normal group) and those with left ventricular wall motion abnormalities (abnormal group). Seventeen of the 29 patients (59%) were classified into the abnormal group. Left ventricular wall motion abnormalities were located in the posterolateral (4 patients), apical (1), and posterolateral and apical regions (12). QS patterns of abnormal Q waves in lead I, aVL or V5, V6 rS patterns (R/S ratio < 1) in leads I and V6, and/or R or Rs patterns (R/S ratio > 1) in lead V1 were observed in all patients in the abnormal group, but in none in the normal group. There was a positive correlation between the right ventricular end-diastolic volume index and the number of precordial negative T waves (r = 0.746, p < 0.0001), and the time from onset of the QRS to the terminal portion of the epsilon wave in lead V1 (r = 0.627, p < 0.001). The correlation coefficients showed no significant differences between the groups. A left ventricular lesion associated with arrhythmogenic right ventricular dysplasia was not unusual (59%), and our study suggests that the posterolateral and apical regions are the most frequent sites. The presence of these lesions were predictable by the QRS abnormalities. Moreover, regardless of the presence of such a lesion, the extent of the right ventricular lesion is also predictable by the 12-lead electrocardiographic findings.     

Recovery from severe cyclic antidepressant overdose with hypertonic saline/dextran in a swine model

OBJECTIVE: To determine the effect of a hypertonic saline and dextran (HSD) solution on blood pressure and QS duration during severe cyclic antidepressant (CA) toxicity in swine. METHODS: Ten domestic swine weighing 20-24 kg were anesthetized and placed on mechanical ventilation. Nortriptyline solution was infused intravenously to achieve hypotension (systolic blood pressure equal to 50% of baseline) and a QRS duration of 120 msec. After reaching toxicity, the animals received in a randomized fashion either 10 mL/kg of a 7.5% saline/6% dextran solution or an equal volume of 0.9% saline as a rapid intravenous bolus. The animals were observed for one hour or until they died. Blood pressure and ECG were recorded continuously. Arterial pH was maintained in the physiologic range by controlled ventilation. RESULTS: Mean systolic blood pressure 10 minutes after treatment was 45 +/- 8 torr in the normal- saline group compared with 115 +/- 12 torr in the HSD group (p < 0.05). Mean QRS duration 10 minutes after treatment was 180 +/- 8 msec in the normal-saline group; it was 88 +/- 13 msec in the HSD group (p < 0.05). All normal-saline--group animals died within 20 minutes, and four of the five animals in the HSD group survived to 60 minutes (p < 0.05). The mean peak sodium concentration was 157 mmol/dL (mEq/dL) in the HSD group, and this was transient. CONCLUSION: In this swine model of severe CA toxicity, a solution of 7.5% saline/6% dextran significantly reversed hypotension and QRS prolongation. HSD also improved survival to 60 minutes.     

Porous-coated total hip arthroplasty in the young

OBJECTIVE: To evaluate whether thromboxane A2 participates in the ischemia-reperfusion injury associated with acute compartmental syndrome (ACS) and if by using a cyclooxygenase inhibitor this can be either reduced or abolished. DESIGN: To assess the role of thromboxane A2 in ACS, a tourniquet was applied for 2 hours to the hind limb of 12 dogs. Group 1 (n = 6) served as controls while group 2 (n = 6) was pretreated with lysine-acetyl-salicylate (Lysoprim). Blood thromboxane B2 levels and intracompartmental pressures were assayed prior to inflation of the tourniquet and at 5 minutes, 90 minutes, and 24, 72, and 144 hours after deflation. RESULTS: Five minutes after deflation, the compartmental pressure increased from 11.2 +/- 2.2 mm Hg to 16.1 +/- 3.3 mm Hg and 17 +/- 2.2 mm Hg (mean +/- SD) in groups 2 and 1, respectively. At 90 minutes and 24 hours, pressures were 17.1 +/- 3.3 mm Hg and 23.2 +/- 3.3 mm Hg (P<.01) and 15.3 +/- 2.6 mm Hg and 25.2 +/- 1.8 mm Hg (mean +/- SD) (P<.001), respectively, in groups 2 and 1. A similar effect, although of a lesser magnitude, was observed in the counterlateral limb. Thromboxane B2 levels increased from a mean (+/- SD) of 46 +/- 5.5 pg/0.1 mL to 132 +/- 7.5 pg/0.1 mL at 90 minutes in group 1, while remaining unchanged in group 2. CONCLUSIONS: Thromboxane A2 plays a major role in the ischemia-reperfusion injury of acute compartmental syndrome. By using a cyclooxygenase inhibitor both the levels of thromboxane and the compartmental pressures can be reduced.     

Vectorcardiograms in aortic and mitral regurgitation -- a comparative study

Thirteen patients with aortic regurgitation (AR) and 13 with mitral regurgitation (MR) were compared quantitatively from the standpoint of their vector-cardiograms (VCG). Vectorcardiographic parameters were also compared with left ventricular angiographic parameters. The QR time interval was longer and the magnitude of the spatial maximum QRS vector was larger in the AR group, but these differences were thought to be attributed to the differences in length of the left ventricular long axis and the left ventricular end diastolic volume (LVEDV). In the AR group, the ratio of the width to the long axis of the QRS loop in the horizontal plane correlated well with the length of the left ventricular long axis and the angle made by the axis from the middle of the aortic valve to the left ventricular apex and the horizontal axis in the lateral view of the angiogram. In the MR group, these correlations were poor.     

Effect of alpha-ketoisocaproate and leucine on the in vivo oxidation of glutamate and glutamine in the rat brain

A successful primary percutaneous transluminal coronary angioplasty (PTCA) program requires a learning process whereby the efficiency of the cardiac catheterization laboratory to deliver prompt intervention can be refined. The purpose of this study was to (1) quantify this learning process in terms of shortening the time to reperfusion, (2) examine the changes in strategy that allowed for this, and (3) determine if expedited reperfusion by primary PTCA improved patient outcomes. A database of all primary PTCA procedures was established in February 1, 1994. Continuous quality assurance analysis was performed, and program modifications introduced as needed. Patients were separated into early (group A = February 1, 1994 through January 31, 1995) and late (group B1 = February 1, 1995 through June 31, 1995, and group B2 = July 1, 1995 through December 31, 1995) cohorts. Time intervals to certain treatment landmarks were compared among groups. In-hospital outcomes were tabulated. Fifty-two consecutive patients were included (group A = 19, group B1 = 17, group B2 = 16). Time intervals shortened significantly (group A vs group B1 vs group B2) with the time from hospital presentation to first balloon inflation decreasing progressively (from 205 to 119 to 97 minutes; p <0.001). Most of this decrease was obtained by shortening the time from hospital presentation to xylocaine administration (158 to 85 to 72 minutes; p <0.005), although the time from xylocaine to first balloon inflation also decreased (from 47 to 33 to 24 minutes; p <0.005). Parallel decreases for in-hospital mortality (26% vs 0%; p = 0.004), adverse events (47% vs 18%; p = 0.05), and length of hospital stay (13.3 +/- 13.7 vs 8.4 +/- 4.4 days; p = NS) were demonstrated for groups A versus B1 and B2. A learning effect following initiation of a primary PTCA program is demonstrated in which reperfusion was more rapidly achieved as the result of procedural changes directed by quality improvement analysis with a concurrent improvement in in-hospital outcomes.     

Color-coded measures of myocardial velocity throughout the cardiac cycle by tissue Doppler imaging to quantify regional left ventricular function

TDI is a new echocardiographic technique that calculates and displays color-coded myocardial velocity on-line. To determine the feasibility of endocardial velocity throughout the cardiac cycle as a means to quantify regional function, 20 normal subjects aged 30 +/- 5 years and 12 patients with heart disease aged 62 +/- 17 years were studied with a prototype TDI system. TDI M-mode images were acquired by using a multicolored velocity map (display range, -30 to 30 mm/sec; temporal resolution, 90 Hz). Color-coded velocity data were then converted to numeric values off-line at 50 msec intervals. Posterior wall velocities throughout the cardiac cycle by TDI were closely correlated with velocity calculations from the first derivative of routine digitized M-mode tracings (group mean r = 0.88 +/- 0.03, SEE = 7.0 +/- 1.1 mm/sec). Anteroseptal TDI color-coded systolic velocity occurred 164 +/- 84 msec from the onset of the electrocardiographic QRS compared with 203 +/- 33 msec in the posterior wall (P < 0.05) in normal subjects, consistent with normal electrical activation. Significant differences in systolic and diastolic posterior wall TDI velocity data were observed in patients with hypokinetic or akinetic segments assessed by independent routine study when compared with normal controls. Calculated systolic and early diastolic posterior wall TDI indexes correlated significantly with percentage of wall thickening. Of abnormal anteroseptal segments, TDI systolic time velocity integrals were significantly different than normal and correlated with percentage of wall thickening. TDI has potential to quantitatively assess regional left ventricular function.     

Solution structure of human p8MTCP1, a cysteine-rich protein encoded by the MTCP1 oncogene, reveals a new alpha-helical assembly motif

MTCP1 (for Mature-T-Cell Proliferation) is the first gene unequivocally identified in the group of uncommon leukemias with a mature phenotype. The three-dimensional solution structure of the human p8(MTCP1) protein encoded by the MTCP1 oncogene was determined by homonuclear proton two-dimensional NMR methods at 600 MHz. After sequence specific assignments, a total of 931 distance restraints and 57 dihedral restraints were collected. The location of the three previously unassigned disulfide bridges was determined from preliminary DIANA structures, using a statistical analysis of intercystinyl distances. The solution structure of p8(MTCP1) is presented as a set of 30 DIANA structures, further refined by restrained molecular dynamics using a simulated annealing protocol with the AMBER force field. The r.m.s.d. values with respect to the mean structure for the backbone and all heavy atoms for a family of 30 structures are 0.73(+/-0.28) and 1.17(+/-0.23) A, when the structured core of the protein (residues 5 to 63) is considered. The solution structure of p8(MTCP1) reveals an original scaffold consisting of three alpha helices, associated with a new cysteine motif. Two of the helices are covalently paired by two disulfide bridges, forming an alpha-hairpin which resembles an antiparallel coiled-coil. The third helix is oriented roughly parallel to the plane defined by the alpha-antiparallel motif and its axis forms an angle of approximately 60 degrees with respect to the main axis of this motif.     

Assessment of a prototype battery operated wax-knife for domiciliary and surgery use

The aims of this study were to examine a prototype battery operated wax-knife, assess the extent to which manufacturer's claims have been achieved and determine its potential for clinical use. The mean time required for the wax-knife to achieve an operating temperature of 150 degrees C was 20.2(+/-4.3) s. The mean operating temperature of the ceramic blade was 155.4(+/-3.9) degrees C, range 150 degrees C to 162 degrees C. The mean usage time following full battery recharge was 42 (+/-2) minutes. The wax-knife provided a direct heating tool which retained many of the characteristics of the traditional wax-knife and was suitable for use in the surgery and in domiciliary situations.     

Randomised double-blind clinical trial of intermediate- versus high-dose chloral hydrate for neuroimaging of children

Orally administered chloral hydrate is the most widely used sedative in children undergoing MRI. We compared intermediate- and high-dose oral chloral hydrate in 97 consecutive children undergoing MRI in a prospective, controlled, double-blind, randomised clinical trial. There were 50 girls and 47 boys, mean weight (+/- SD) 14.7 +/- 6.4 kg, and mean age 38 +/- 31. The children were randomly allocated to receive chloral hydrate syrup either 70 mg/kg (group A, n = 50) or 100 mg/kg (group B, n = 47). These two groups were not significantly different in sex, weight, age, diagnosis or ambulatory medication. The mean initial dose (+/- SEM) was 64 +/- 2 mg/kg for group A and 93 +/- 2 mg/kg for group B. Because adequate sedation was not achieved, 14 patients in group A and 6 in group B required a second dose, giving a mean total dose of 70 +/- 2 mg/kg for group A and 96 +/- 2 mg/kg for group B. The percentage of successful examinations after the initial dose (A: 64%, B: 87%; p < 0.05) and the total dose (A: 92%, B:100%; p = 0.14) was higher in group B. Significant differences were found for the time of onset of sedation (A:28 +/- 2 min, B: 21 +/- 1 min; p < 0.05), but not for the time to spontaneous awakening after the completion of the examination. The rate of adverse reactions was similar (A: 20%, B: 21%; p = 1.00). We conclude that high-dose oral chloral hydrate improves the management of children undergoing MRI.     

Electrocardiographic characteristics of endurance-trained Alaskan sled dogs

OBJECTIVE: To determine electrocardiographic characteristics of endurance-trained Alaskan sled dogs. DESIGN: Case series. ANIMALS: 319 Alaskan sled dogs entered to compete in the 1994 Iditarod Trail Sled Dog Race. PROCEDURE: ECG were recorded while dogs were standing and were analyzed digitally. RESULTS: Amplitudes of P waves (median, 0.40 mV; fifth to 95th percentile range, 0.11 to 0.61 mV) and R waves in lead II (median, 3.02 mV; fifth to 95th percentile range, 1.49 to 4.40 mV) were high; durations of P waves in lead II (median, 61 milliseconds; fifth to 95th percentile range, 36 to 96 milliseconds), QRS complexes (median, 64 milliseconds; fifth to 95th percentile range, 52 to 80 milliseconds), and QT intervals (median, 236 milliseconds; fifth to 95th percentile range, 208 to 277 milliseconds) were prolonged. Median value for mean axis of ventricular depolarization was 57 degrees (fifth to 95th percentile range, 19 to 90 degrees). Atrial and ventricular premature depolarizations were observed in 3 (0.9%) and 4 (1.3%) of 319 dogs, respectively, and paroxysmal ventricular tachycardia was detected in 1 (0.3%). CLINICAL IMPLICATIONS: Results suggest that electrocardiographic characteristics of endurance-trained Alaskan sled dogs differ from those reported for nonsled dogs, probably as a result of effects of endurance training on heart size. Some of these characteristics could be mistaken as evidence of pathologic cardiac hypertrophy.     

Adenosine-enhanced ischemic preconditioning provides enhanced postischemic recovery and limitation of infarct size in the rabbit heart

OBJECTIVE: The purpose of this study was to determine the effect of an intracoronary bolus injection of adenosine used in concert with ischemic preconditioning on postischemic functional recovery and infarct size reduction in the rabbit heart and to compare adenosine-enhanced ischemic preconditioning with ischemic preconditioning and magnesium-supplemented potassium cardioplegia. METHODS: New Zealand White rabbits (n = 36) were used for Langendorff perfusion. Control hearts were perfused at 37 degrees C for 180 minutes; global ischemic hearts received 30 minutes of global ischemia and 120 minutes of reperfusion; magnesium-supplemented potassium cardioplegic hearts received cardioplegia 5 minutes before global ischemia; ischemic preconditioned hearts received 5 minutes of zero-flow global ischemia and 5 minutes of reperfusion before global ischemia; adenosine-enhanced ischemic preconditioned hearts received a bolus injection of adenosine just before the preconditioning. To separate the effects of adenosine from adenosine-enhanced ischemic preconditioning, a control group received a bolus injection of adenosine 10 minutes before global ischemia. RESULTS: Infarct volume in global ischemic hearts was 32.9% +/- 5.1% and 1.03% +/- 0.3% in control hearts. The infarct volume decreased (10.23% +/- 2.6% and 7.0% +/- 1.6%, respectively; p < 0.001 versus global ischemia) in the ischemic preconditioned group and control group, but this did not enhance postischemic functional recovery. Magnesium-supplemented potassium cardioplegia and adenosine-enhanced ischemic preconditioning significantly decreased infarct volume (2.9% +/- 0.8% and 2.8% +/- 0.55%, respectively; p < 0.001 versus global ischemia, p = 0.02 versus ischemic preconditioning and p = 0.05 versus control group) and significantly enhanced postischemic functional recovery. CONCLUSIONS: Adenosine-enhanced ischemic preconditioning is superior to ischemic preconditioning and provides equal protection to that afforded by magnesium-supplemented potassium cardioplegia.     

High-fidelity spectrocardiography for the diagnosis of ischemic cardiopathy. The validation of a new method for analyzing the spectral components of the QRS complex

BACKGROUND: Analysis of high-frequency QRS complex envelope has been suggested as a method that could detect myocardial ischemia but the characteristics of the turbulence spectral from an spectral-temporal mapping into the QRS complex has not been studied yet. This is a prospective study of phase I for the validation of a new diagnostic test. AIMS: The aims for this study are: 1) To validate a new method for the detection of transient myocardial ischemia by both, high-frequency QRS and spectral turbulence analysis, which we have named "high-fidelity spectrocardiogram" (HFS). 2) To compare the sensitivity, specificity and accuracy of this HFS versus those obtained from nuclear medicine (NM-MIBI) and a conventional exercise ECG test, in a highly selected population. PATIENTS AND METHODS: Twenty-five patients (P) were studied: 10 P (Group B) with risk factors for coronary artery disease, without previous infarct, who had atypical precordial pain and a conventional ECG considered as "normal" by two cardiologists. The group A was formed by 15 P without risk factors or another kind of heart disease. All patients underwent a conventional surface ECG, which had to be normal in order to be considered for this study. Echocardiogram, exercise testing ECG and a NM-MIBI study were also normal. The HFS recording was taken before and after Dipyridamole testing, similar to the conventional method for the NM-MIBI (dipyridamole 0.25 mg/Kg/doses) studies. Our software for the analysis of QRS-frequencies was constructed from a language Turbo C++. The Fourier's transform allowed the construction of 3-dimensional graphics. After the determination of the best wide band for detecting changes in the frequency contained of QRS, the determination coefficients (r2) were obtained and compared before and after the challenge with dipyridamole. These changes were compared between groups (A vs B) later. RESULTS: The r2 changed more than 30% after dipyridamole in those patients in whom myocardial ischemia was demonstrated later by NM-MIBI. The sensitivity (85%) and specificity (90%) of HFS were similar to the nuclear medicine for identifying myocardial ischemia, but higher than a conventional exercise ECG testing (p.001). The main change in HFS was in the frequency-contained QRS in the 130-260 Hz band. The accuracy of our method was increased when an analysis of each orthogonal lead was made. There was a clear tendency of the group B to increase the QRS duration, while the contrary was found in group A, being the QRS the shorter (p.064). The chronological responses were different in those patients with ischemia. CONCLUSION: This study suggests that an episode of myocardial ischemia is able to change in a dramatic manner the frequency-contained within of the QRS complex, in spite of an unchanged ST segment in the conventional exercise ECG. We suggest that the HFS could be a good method for identifying myocardial ischemia. Its advantages could be important, particularly when the conventional exercise ECG is non informative.     

Early branching eukaryotes?

The effect of hyperbaric oxygen (HBO) on ischemic muscle tissue pH was evaluated continuously. The hind limbs of male Sprague-Dawley rats (N=11, both groups) were amputated and stored in room air (20.1% oxygen [O2], 1.0 ATM, 24 degrees C) or in HBO (100% O2, 2.9 ATM, 24 degrees C) for 240 minutes. Rat muscle tissue pH was continuously monitored with a micro-pH electrode following amputation. There was no significant difference between the average starting tissue pH of control and treated limbs (p=0.45). At 240 minutes of ischemia the control group tissue pH decreased 0.80 pH units whereas the treatment group decreased 0.68 pH units (p < 0.05). The tissue pH of control limbs declined 30.7 times faster than treated limbs during the first 36 minutes of ischemia (p < 0.05). From 36 to 240 minutes the rates of acidosis were similar and did not differ significantly (p=0.46). In a separate study, male Sprague-Dawley rats were anesthetized with pentobarbital and ketamine. Aortic arterial blood gases were obtained at 5 minutes (N=8) and 15 minutes (N=8) postanesthesia. The average serum pH, carbon dioxide, oxygen, and bicarbonate levels remained within normal limits in both groups and did not differ significantly (p > 0.05 for all parameters). Anesthesia produced no serum respiratory or metabolic acidosis and did not contribute to the initial ischemic tissue pH. These results suggest that HBO delays the progression of metabolic acidosis in this amputated limb model. This is further supporting evidence for the tissue-preserving effect of oxygen when delivered in hyperbaric conditions. However, the clinical application of this technique may be limited due to the difference in the volume of tissue presented for major limb replantation and the short window of beneficial effects.     

Heart rate variability during the first 24 hours of successfully reperfused acute myocardial infarction: paradoxic decrease after reperfusion

Heart rate variability (HRV) was evaluated during the first 24 hours of hospitalization in 36 patients with acute myocardial infarction. Reperfusion was achieved by 60 minutes in 21 patients (group M1) and by 130 minutes in the remaining 15 (group M2). Mean 24-hour HRV measures were not significantly different between groups M1 and M2. Hourly spectral analysis revealed a decrease in total power (0.01 to 1.0 Hz) from 0 to 8 hours to 9 to 16 and 17 to 24 hours in groups M1 (7.04 +/- 0.27 to 6.94 +/- 0.28 and 6.52 +/- 0.18; p = 0.0006) and in group M2 (6.88 +/- 0.30 to 6.57 +/- 0.23 and 6.40 +/- 0.15; p = 0.002). Total power decreased immediately after reperfusion: in group M1 it decreased during the second hour (7.32 +/- 0.96 to 6.42 +/- 1.2; p = 0.001) and in group M2 during the third (7.47 +/- 1.2 to 6.73 +/- 1.4; p = 0.049) and fourth hours (7.47 +/- 1.2 to 6.48 +/- 1.4; p = 0.029). Mean change in total power in the second hour was -11.6% in group M1 and +3.9% in group M2 (p = 0.0001) and in the third hour, +14.5% in group M1 and -8.6% in group M2 (p = 0.006). During the remaining 21 hours, there was no significant difference in hourly change in total power between groups. Similar changes were noted in high-frequency power, but the ratio of low-frequency to high-frequency power was unchanged. In acute myocardial infarction, HRV is higher during the early phase and decreases as hours progress. Reperfusion causes an immediate, transient, and seemingly paradoxic decrease in HRV, probably because of an abrupt decrease in parasympathetic tone.