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PubMed1996

[Follow-up of left ventricular systolic function in the first year following previous infarction].

OBJECTIVES: To follow the left ventricular systolic function changes as assessed by global and regional ejection fraction during the first year of evolution after anterior myocardial infarction, as well as to analyse how the most relevant clinical and angio-graphic parameters influence them. MATERIALS AND METHODS: Sixty-six consecutive patients with a first infarction of anterior location, completed 1 year of follow-up with radionuclide ventriculography, T1-SPECT after exercise or dypiridamole and cardiac catheterization before discharge; radionuclide ventriculography was repeated 6 and 12 months later. Twenty-five patients underwent revascularization procedures at the time of predischarge, 16 using successful percutaneous angioplasty of the left anterior descending artery and 9 using aorto-coronary graft surgery. Dilated patients were controlled, from an angiographic point, of view 6 months after PTCA. RESULTS: Predischarge global EF (42.9 +/- 12.6) increased significantly between the 6-month (46.9 +/- 12.8; p < 0.001) and 12-month (47.6 +/- 12; p < 0.001) studies. Differences in these two last studies were minor and had no statistical significance. A significant increase was present in revascularized or medically treated patients; i.e. those who underwent thrombolytic therapy or conventional treatment at admittance as well as mono or multivessel disease patients. No significant differences were detected in the mean ejection fraction in patients without residual stenosis in the infarct-related artery (48.1 +/- 13.3 vs 50 +/- 12.6; NS) or those presenting a pre-discharge ejection fraction > or = 45% (53.5 +/- 7.5 vs 55.1 +/- 3.3; NS). Among different variables tested, predischarge global ejection fraction (negative coefficient) and, to a lesser extent, percutaneous angioplasty were independent predictors of a significant increase of ejection fraction during follow-up. Changes from predischarge to 12 month study were significant in the regional ejection fraction in the anteroseptal (33.1 +/- 14.7 vs 40.1 +/- 13.3; p < 0.001), inferoseptal (34.6 +/- 15.8 vs 42 +/- 16.9; p < 0.001), apical (46.3 +/- 19.1 vs 50.8 +/- 19.7; p < 0.01), antero-medial (50.6 +/- 22.4 vs 56.6 +/- 24.3; p < 0.01) and anteroapical (51.6 +/- 23.5 vs 58 +/- 27.5; p < 0.01) segments. In the anterobasal segment, regional ejection fraction only showed a statistical tendency to increase during follow-up and changes in inferior and lateral segments, distal to the infarcted area, were minor and without statistical significance. The most distinct infarct-related segments, antero- and inferoseptal, showed significant increases in the main group of patients, revascularized or nonrevascularized, undergoing thrombolitic or conventional therapy, with single or multivessel disease. Only patients without residual stenosis of the infarct-related artery (the left descending anterior) disclosed negligible or negative changes without statistical significance. Percutaneously dilated patients showed the highest increase of the infarct-related segments regional ejection fraction. In multivessel disease, the infarct-related segments regional ejection fraction did not increase significantly in surgically treated patients, conversely to those who underwent medical therapy. CONCLUSIONS: Global and regional ejection fraction of the infarcted area increased significantly during the first year after anterior myocardial infarction, mainly prior to six months patients with significant residual stenosis of the artery related to the infarct. Recovery is present both in patients who underwent thrombolysis or conventional treatment at admittance and revascularization or medical treatment before discharge and is inversely correlated to the predischarge global ejection fraction value. This evolution suggests that a significant amount of stunned myocardium is still present before discharge.

Adult↗

PubMed2005

Quantification of regional left and right ventricular longitudinal function in 75 normal fetuses using ultrasound-based strain rate and strain imaging.

Previous reports have demonstrated that myocardial velocities are not sufficiently sensitive in fetal heart studies. Strain (S) and strain rate (SR) imaging is a new noninvasive ultrasonic technique able to quantify regional myocardial deformation properties. SR imaging has a superior sensitivity than myocardial velocity for noninvasive assessment of ventricular function, but this technique has not been used in the fetal heart. Our aim was to evaluate the feasibility of S/SR imaging in the fetal heart and to study characteristics of myocardial deformation properties and their changes with the gestational age in healthy fetuses. We studied 75 normal fetuses (weeks gestation 25 +/- 4, no evidence of structural cardiovascular disease by 2-D echo and Doppler study) using S/SR imaging. Left (LV) and right ventricle (RV) peak myocardial systolic, early diastolic and SR values during atrial contraction were obtained but, for S, we measured only peak systolic values. The sample volume was placed in the mid-segment of LV septal, lateral and RV free wall. S and SR curves were obtained in all the studied population. Peak longitudinal systolic deformation was homogeneous in all the walls studied. Moreover, fetal myocardial S and SR during diastole were characterized by a higher deformation during atrial contraction than during early filling. Peak systolic and peak diastolic ratios of regional myocardial deformation properties significantly correlated with the gestational age. Inter- and intraobserver variabilities for S and SR parameters were < 15%, < 18% and < 13%, < 15%, respectively. SR imaging is feasible in selected healthy fetuses, with a limited reproducibility; we presented normal values for the fetal heart; S/SR during fetal life are homogeneous in both LV and RV; and longitudinal myocardial deformation properties increase with the gestational age.

Echocardiography, Doppler, Color↗

PubMed1982

Patterns of flow and conduction during early ventricular arrhythmias following coronary arterial occlusion in the dog.

The early ventricular arrhythmias of acute myocardial ischaemia arise against a background of rapid alterations in regional myocardial blood flow and electrophysiological properties. The relation between patterns of flow and epicardial activation has been examined in eight open chest anaesthetised dogs at time of onset of these arrhythmias following a proximal occlusion of the left anterior descending coronary artery. Data were derived from 80 epicardial and endocardial sites within a 4 X 5 cm area of left ventricular free wall and processed utilising a three-dimensional computer plotting program. Mean flow within the ischaemic zone was reduced to 0.27 and 0.24 cm3 x g-1 x min-1 in epicardium and endocardium respectively. Marked epicardial activation delays and fragmentation of conduction were observed confined to areas of flow less than 0.3 cm3 x g-1 x min-1. 74% of endocardial and 71% of epicardial tissue samples within the ischaemic zone derived from this area and analysis of flow distribution between adjacent samples demonstrated spatial heterogeneity of flow. It is suggested that local spatial variability in flow within the central ischaemic region may be a prerequisite for abnormal fractionation of conduction leading to re-entrant excitation at the time of onset of early ventricular arrhythmias.

Animals↗

PubMed2005

Surgical anatomy of the recurrent laryngeal nerve revisited.

OBJECTIVES: Previous anatomic studies of the recurrent laryngeal nerves (RLNs) have described the variability in the course of the RLN. The anatomy of the nerve appears more constant along its distal segment near the cricothyroid joint, which is our surgical approach to the initial identification of the nerve. Understanding the topographical anatomy of the nerve in this region facilitates quick and safe nerve identification. The surgical topographical anatomy of the nerve in this region has not been studied in detail, which is the focus of this study. METHODS: A total of 278 RLNs in 190 patients were dissected during thyroidectomy and/or parathyroidectomy. The course of the nerve was recorded, paying particular attention to the directional course along its distal portion. The angle in which it coursed in relationship to a line paralleling the tracheoesophageal groove was determined. RESULTS: All 278 nerves were identified. Seventy-eight percent of the right-sided nerves coursed between 15 and 45 degrees, and 77% of the left-sided nerves coursed between 0 and 30 degrees. It appears that the nerve is more likely to travel at a more obtuse angle with right-sided RLNs and in patients with a low-lying cricoid. There was no permanent postoperative RLN palsy, and the incidence of temporary palsy was 1%. CONCLUSIONS: Approaching the nerve along its distal portion is safe and effective. The surgical topographical anatomy in this region is described in detail. Some of the potential advantages of identifying the nerve more distally include less chance of disrupting the blood supply to the inferior parathyroid gland, dissection along a shorter portion of the nerve, and less variability of the nerve.

Cricoid Cartilage↗

PubMed1993

DNA sequence analysis of conserved and unique regions of swinepox virus: identification of genetic elements supporting phenotypic observations including a novel G protein-coupled receptor homologue.

Swinepox virus (SPV) contains a double-stranded cross-linked linear DNA genome of approximately 175 kilobase pairs with terminal inverted repetitions (TIRs) of 4.3 kb. The nucleotide sequence was determined for fragments from several regions of the genome including a 2.85-kb fragment from the central potentially conserved portion and two fragments within the presumed variable near-terminal regions which tend to be unique to a given poxvirus. The core sequence contains one partial and two complete open reading frames that are highly conserved and colinear with three contiguous ORFs within the HindIII D fragment of vaccinia virus (VV). The two near-terminal fragments, encompassing 14.2 and 3.6 kb, are respectively located 2.1 kb internal to the left and right cross-linked termini of the DNA and span the TIR junctions. The sequences encode 25 open reading frames including numerous proteins predicted to be membrane-bound or secreted in infected cells. Several ORFs unique to SPV were identified that may be involved in cell attachment, immune modulation, and pathogenesis including a novel poxvirus G protein-coupled receptor. In addition, several polypeptides encoded within the near-terminal regions of vaccinia virus DNA that function as host range or virulence factors are lacking within this region of swinepox virus including the VV growth factor, complement-binding protein, and ORFs C7L and K1L, associated with host range. The lack of these functional homologues could explain the characteristic attenuated phenotype and limited host range of SPV.

Amino Acid Sequence↗

PubMed1995

[Normal values for dobutamine stress echocardiography].

Dobutamine stress echocardiography having established itself as a sensitive method for diagnosing coronary heart disease, even in the absence of normative values, the physiological haemodynamics as well as the physiological values for global and regional left ventricular myocardial function were measured. TEST PERSONS AND METHODS: 14 healthy subjects (ten men, four women; median age 25 [range 21-32] years) underwent dobutamine stress echocardiography according to an internationally practised dosage steps protocol (5-40 micrograms/kg/min with additional 0.5 mg atropine at 40 micrograms). RESULTS: Maximal infusion rate achieved a serum dobutamine level of 1.67 micrograms/ml with minimal quartiles; it did not influence serum electrolytes (especially potassium). Heart rate increased from 64 to 150/min (P < 0.0001), blood pressure from 111/66 to 158/88 mmHg (systolic: P < 0.0001; diastolic P < 0.001) and the double product of systolic pressure and heart rate from 6714 to 24571 (P < 0.001). While the end-diastolic volume index decreased from 50 to 37 ml/m2 (P < 0.05), the end-systolic volume index fell from 20 to 7 ml/m2 (P < 0.0001). Regional wall motion analysis indicated an increase in left ventricular circumferential contractility with little scatter. CONCLUSIONS: The usual protocol for dobutamine stress echocardiography is a sensible one, because the haemodynamic effect occurs already at low dosage and can then be increased significantly with further dosage steps. High serum dobutamine concentrations can be achieved without arrhythmogenic hypokalaemia. Volume index and ejection fraction are especially discriminatory variables. Quantitative analysis of wall motion is justified because of the low scatter of values.

Adult↗

PubMed2006

Emotional responses to unpleasant music correlates with damage to the parahippocampal cortex.

Music is typically a pleasurable experience. But under certain circumstances, music can also be unpleasant, for example, when a young child randomly hits piano keys. Such unpleasant musical experiences have been shown to activate a network of brain structures involved in emotion, mostly located in the medial temporal lobe: the parahippocampal gyrus, amygdala, hippocampus and temporal pole. However, the differential roles of these regions remain largely unknown. In this study, pleasant and unpleasant music was presented to 17 patients with variable excisions of the medial temporal lobe, as well as to 19 matched controls. The pleasant music corresponded to happy and sad selections taken from the classical instrumental repertoire; the unpleasant music was the dissonant arrangement of the same selections. Only patients with substantial resections of the left or right parahippocampal cortex (PHC) gave highly abnormal judgements to dissonant music; they rated dissonant music as slightly pleasant while controls found it unpleasant. This indifference to dissonance was correlated with the remaining volume in the PHC, but was unrelated to the volume of the surrounding structures. The impairment was specific: the same patients judged consonant music to be pleasant, and were able to judge music as happy or sad. Furthermore, this lack of responsiveness to unpleasantness was not due to a perceptual disorder, because all patients were able to detect intentional errors in the musical excerpts. Moreover, the impairment differed from that induced by amygdala damage alone. These findings are consistent with a two-dimensional model of defensive responses to aversive stimuli, in which the PHC and the amygdala subserve different roles.

Adult↗

PubMed1994

Speed and sensitivity of mechanical versus electrographic indicators to mild or moderate myocardial ischemia in the pig.

BACKGROUND: Intraoperative myocardial ischemia may be detected and quantified by indexes of myocardial contraction or by electrography. The relative reliability of these two approaches is controversial. Two issues are relevant: the timing of events after the onset of mild to moderate ischemia, and the sensitivity of measures to ischemia at steady state. METHODS: In eight pigs, a carotid-to-left anterior descending coronary artery shunt with a flow meter was installed. Flow to the left anterior descending coronary artery was reduced in steps of 10% from baseline values to 50% of baseline. Wall thickness, myocardial QRS amplitude, and ST-segment deviation were measured every 1 min for 6 min at each step. Regional myocardial lactate extraction was measured at 6 min. RESULTS: Linear relations were found between the percentage of baseline coronary flow and all four dependent variables at steady state, indicating equal sensitivity (defined as rate of change with respect to flow reduction) to myocardial ischemia. After flow reduction, decreases in systolic wall thickening occurred first and were followed by a QRS amplitude decrease and then ST-segment elevation. The onset of ischemia was earlier with more severe reductions of coronary flow. CONCLUSIONS: Mechanical and electric measures of myocardial ischemia show equal sensitivity at steady state even though regional contraction changed more quickly than did QRS amplitude or the ST-segment after an abrupt reduction in coronary flow.

Animals↗

PubMed2001

Myocardial viability: recent developments in detection and clinical significance.

The long-term prognosis of patients with ischemic cardiomyopathy is highly variable, depending on the extent of myocardial viability and the success and completeness of the revascularization techniques used. Other important factors include left ventricular function, extent of coronary artery disease (CAD), and patient age. Chronic left ventricular dysfunction in ischemic cardiomyopathy is the result of a mixture of scarred as well as hibernating myocardium. In fact, most patients have both scarring and hibernation in different regions. Transmural biopsies of dysfunctional segments reveals that recovery of function is inversely proportional to the extent of fibrosis and that endocardial fibrosis extending over 30% of the myocardial thickness precludes recovery of function.Nagueh et al. [1] evaluated the relation of contractile reserve and thallium uptake in hibernating myocardium to myocardial structure in humans. The authors found that segments with postoperative functional recovery had more wall thickening at low-dose dobutamine echocardiography (DE), higher thallium uptake, and less fibrosis (2.0 vs 28%) than those segments without recovery. Also, segments with viability on DE had less fibrosis, less vimentin and fibronectin, more glycogen, and higher thallium uptake, than those segments without viability. Importantly, segments viable by single-photon emission computed tomography (SPECT) and DE had significantly less fibrosis (1%) than those viable by only one of the two techniques. In this review, we discuss recent developments in the detection of myocardial viability, including echocardiography, nuclear cardiac imaging, magnetic resonance imaging (MRI), and other techniques.

Cell Survival↗

PubMed2003

Molecular analysis of incHI1 antimicrobial resistance plasmids from Salmonella serovar Typhi strains associated with typhoid fever.

The first outbreak of multidrug-resistant (MDR) typhoid fever in Vietnam was in 1993, and by 1995 nearly 90% of cases were MDR. Plasmid HCM1, sequenced in full, is an incHI1 plasmid from Salmonella enterica serovar Typhi strain CT18, isolated in Vietnam in 1993. Restriction analysis shows that pHCM1 shares a restriction fragment length polymorphism (RFLP) pattern with plasmids isolated from the first outbreak and 10 of 17 MDR plasmids isolated from sporadic cases occurring at the same time in Vietnam. A core region of pHCM1 has significant DNA sequence similarity to plasmid R27, isolated in 1961 from S. enterica in the United Kingdom. There are five regions of DNA in pHCM1 which are not present in R27. Two of these are putative acquisition regions; the largest is 34.955 kbp in length and includes sequences of several antibiotic resistance genes and several insertion sequences. The borders of this region are defined by two identical IS10 left elements, associated with an inversion of DNA or with a truncated Tn10 element. The second, smaller region is 14.751 kbp and carries a trimethoprim resistance gene dfr14A cassette associated with a class 1 integrase. In 1993 to 1994, restriction analysis revealed some variations in the structures of Salmonella serovar Typhi MDR plasmids which were mapped to the two putative acquisition regions and three smaller variable regions. In 1996 a single RFLP type, RFLP7, was found to carry the dfrA7 and sul-1 genes, which were not present on R27 or pHCM1. This plasmid type appears to have a selective advantage over other plasmids with the same resistance phenotype.

Conjugation, Genetic↗

PubMed2001

Atrial mapping by basket catheter in patients with atrial fibrillation submitted to linear ablation.

Recently non-pharmacological therapies for atrial fibrillation (AF) have been developed. The electrophysiological mechanisms of AF is thought to be the development of multiple reentrant wavelets circulating around anatomic barriers and variable regions of functional conduction block responsible of the perpetuation of the arrhythmia. Also the role of the triggering foci has been highlighted. To cure AF by means of non pharmacological therapy we may eliminate and/or modify the substrate. To better understand the mechanism underlying the AF and to choose the best ablation strategy is of fundamental importance to map the right and the left atrium during AF. Our experience shows that in chronic idiopathic AF disorganized atrial activity is observed at all atrial regions while in paroxysmal idiopathic AF the left septum and the right atrial posterior areas are highly disorganized while the lateral region shows more organized atrial electrical activity. Multipolar basket catheters are extremely useful in mapping right and left atrium in order to guide the best ablation strategy.

Atrial Fibrillation↗

PubMed2002

Diagnostic pitfall: atypical cerebral venous drainage via the vertebral venous system.

We report a case of atypical cerebral venous drainage in a 38-year-old woman with symptoms of benign paroxysmal positional vertigo. Thrombosis of the left internal jugular vein and sigmoid sinus was suspected on the basis of spin-echo and time-of-flight MR findings, but multisection CT angiograms showed a patent sigmoid sinus and predominant drainage via the emissary veins toward the vertebral plexus, with only a minor contribution of the jugular veins. This case illustrates the variability of the venous anatomy in the craniocervical region.

Adult↗

PubMed1998

Effect of ethanol on myocardial infarct size in a canine model of coronary artery occlusion-reperfusion.

This study was conducted to determine if elevated blood alcohol prior to acute coronary artery occlusion affects myocardial infarct size in an in vivo canine model. Seven pentobarbital anesthetized open-chest dogs received 10 min iv infusion of ethanol (0.08 g/kg/min). Ten min after ethanol, the left anterior descending coronary artery (LAD) was occluded distal to its first major branch for 60 min. The LAD was then reperfused for 5 h. Following electrically induced ventricular fibrillation, the area at risk of infarction was delineated with dye. The area of infarction was identified by staining with triphenyl tetrazolium chloride. Eleven untreated control experiments were also conducted. Mean blood ethanol concentration was 155+/-26 mg/dl just prior to LAD occlusion and 47+/-3 mg/dl after 4 h reperfusion. Ethanol infusion had no effect on systemic hemodynamic variables during ischemia. In ethanol treated animals, the area at risk was 19.7+/-3.0% of the left ventricle, and the infarct size was 20.9 +/-4.8% of the area at risk. In control experiments, the area at risk was 23.0+/-4.1% of the left ventricle (p > 0.05), and the infarct size was 21.6+/-3.8% of the area at risk (p > 0.05). Collateral blood flow to ischemic region did not differ between the two groups, and the relationships between infarct size and collateral flow were similar for control and untreated hearts. Acute ethanol exposure prior to coronary artery occlusion and subsequent reperfusion does not affect myocardial infarct size in the heart of the anesthetized dog.

Animals↗

PubMed1990

Hypofrontal vs. hypo-Sylvian blood flow in schizophrenia.

Hypofrontality in schizophrenia has been a frequent but not consistent finding in regional cerebral blood flow studies. However, the contributions of subject and state variables such as age, education, task activation, and anxiety, some of which are known to influence blood flow profiles, have not been thoroughly examined in this population. Here, in a sample including 24 normal, 18 schizophrenic, 22 bipolar, and 13 unipolar depressive subjects, narrative prose memory deficit was found to distinguish both schizophrenic and bipolar subjects from normal controls. Further, when these subjects were engaged in repeated trials of a verbal recognition memory task, left hemisphere hypofrontal blood flow in the early stage of learning was related to narrative memory, independent of diagnostic group. In the late stage of learning, state anxiety was significantly associated with left hypofrontality, while right hypofrontality was significantly related to narrative memory--both findings again independent of diagnostic group. A focal suppression of left hemispheric peri-Sylvian activation (in Broca's and Wernicke's areas) uniquely characterized schizophrenia after taking into account variance due to age, education, gender, state anxiety, and verbal memory. It is concluded that a failure of left peri-Sylvian activation during memory task performance reflects a unique language-related focal deficit in schizophrenia.

Adolescent↗

PubMed1997

Effects of thrombolytic regimen, early catheterization, and predischarge angiographic variables on six-week left ventricular function. The TAMI Investigators. Thrombolysis and Angioplasty in Acute Myocardial Infarction.

The Thrombolysis and Angioplasty in Acute Myocardial Infarction phase 5 (TAMI-5) trial randomized patients to 1 of 3 thrombolytic regimens (alteplase, urokinase, or both), then further randomized them to acute or deferred catheterization. The group of patients randomized to acute catheterization had improved infarct zone but not global left ventricular function on predischarge left ventriculography. To better explore the late effects of these strategies on global and regional left ventricular function, a subset of patients (n = 296) were prospectively evaluated at 6 weeks by multiple uptake gated acquisition (MUGA) radionuclide ventriculography scan. Of these patients, 219 had interpretable studies with paired predischarge and late left ventriculographic data for comparison. At 6 weeks, choice of thrombolytic regimen had no impact on either global or infarct-zone left ventricular function. Further, catheterization strategy (acute vs deferred) did not influence global or infarct-zone function at 6 weeks. In patients randomized to acute catheterization, those undergoing rescue angioplasty had worse infarct-zone wall motion at 6 weeks than patients with a patent infarct vessel not requiring rescue angioplasty (p = 0.002). The early benefit on regional left ventricular function of triage to acute catheterization after thrombolysis for acute myocardial infarction did not persist at 6 weeks, which is most likely attributable to a high incidence of reocclusion. The worse infarct-zone regional wall motion in patients undergoing rescue angioplasty in the acute-catheterization group likely reflects failed reperfusion and illustrates the difficulty in identifying and consequences of early thrombolytic failures.

Aged↗

PubMed1980

Differential sensitivity of regional vascular beds in the dog to low-dose prostacyclin infusion.

The effects of low-dose prostacyclin (PGI2) infusion on abdominal organ, regional central nervous system, and regional myocardial blood flow distribution was studied in 14 open-chested, anesthetized dogs. Blood flow was measured using the radioactive microsphere technique and left atrial (LA) injection of 15-micron spheres. Continuous LA PGI1 infusion (25-35 ng/kg per minute) significantly (P less than 0.05 to P less than 0.005) increased renal cortical (+13%), splenic (+20%), small intestinal (+41%), large intestinal (54%), fundic mucosal (+53%), and antral mucosal (+65%) blood flows whereas pancreatic, gallbladder, and hepatic (arterial) flow remained unchanged. Within the central nervous system blood flow increased in the medulla (+18%) and cerebral cortical gray matter (+17%) but was unchanged in the cervical spinal cord, pons, dorsal thalamus, cerebellum, caudate nucleus, and cerebral white matter. Atrial and ventricular myocardial blood flows and masseter muscle blood flow were unchanged during PGI2 administration. Thus blood flow changes are variable between and within regional vascular beds during low-dose PGI2 infusion in the dog.

Abdomen↗

PubMed1984

Role of site of microsphere injection and catheter position on systemic and regional hemodynamics in rat.

The influences of the site of microsphere injection (intra-atrial vs. intraventricular) and positioning of the left ventricular catheter (aortoventricular vs. atrioventricular) on systemic, renal, and coronary hemodynamics were evaluated in anesthetized rats. The effect of anesthesia on aortoventricular catheter positioning was also evaluated. In anesthetized and open-chest preparations, the systemic and renal hemodynamics were not affected by catheter position or site of microsphere injection; however, myocardial blood flow was dependent on these variables. Variations in coronary blood flow were significantly greater when the catheter was in the aortoventricular position (34 +/- 3%) than with an atrioventricular catheter (11 +/- 2%, P less than 0.01), irrespective of whether the microspheres were injected into the atrium or ventricle. Comparison of anesthetized and conscious rats with aortoventricular catheter indicated lesser variability in coronary blood flow in the conscious rats (P less than 0.01). Therefore, the greater variability of coronary flow measurements in anesthetized rats was caused by the position of the cardiac catheter in the aortoventricular route. However, the variability caused by the aortoventricular catheter was much less in conscious rats. Therefore, coronary flow hemodynamic measurements (microsphere technique) are less variable when they are made in conscious rats.

Anesthesia, General↗

PubMed1992

Role of systemic arterial pressure, heart rate, and derived variables in prediction of severity of myocardial ischemia during acute coronary occlusion in anesthetized dogs.

The present study examined the postulate that the quotient of mean systemic arterial pressure and heart rate predicts the severity of myocardial ischemia during occlusion of the left anterior descending coronary artery. Studies were performed in open-chest fentanyl-anesthetized dogs before and during halothane (n = 8) or isoflurane (n = 8) anesthesia. The pressure-rate quotient (PRQ) decreased significantly in both groups during incremental increases in halothane or isoflurane to 68% and 57% of control values at 0.5 MAC and to 41% and 38% at 1.5 MAC for halothane and isoflurane, respectively. Myocardial lactate production was unchanged from the ischemic region, and no correlation between the PRQ and myocardial lactate production was observed. In contrast, heart rate correlated significantly (r = 0.376; P less than 0.05) with lactate production. The product of systolic systemic arterial pressure and heart rate (rate-pressure product) correlated with blood flow (r = 0.493; P less than 0.001) and with oxygen consumption (r = 0.571; P less than 0.001) in the normal myocardium. A weak correlation (r = 0.330; P less than 0.05) of rate-pressure product with myocardial lactate production from the ischemic region was observed. There were no correlations between the PRQ and myocardial lactate production from the ischemic region or indices of blood flow distribution (i.e., inner/outer ratio in the ischemic region or ischemic/normal ratio). The relationship of hemodynamic variables to measurements of regional myocardial metabolism was independent of background anesthetic agent of depth of anesthesia. The current data suggest that heart rate changes are weakly predictive of severity of myocardial ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗