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PubMed1998

[Quantification of myocardial ischemia in regions dependent on occluded coronary arteries in patients without previous infarction].

INTRODUCTION AND OBJECTIVES: The aim of this study is to assess myocardial ischemia in regions with no infarction dependent occluded coronary arteries. PATIENTS AND METHODS: 149 patients with proved coronary artery disease and without previous myocardial infarction were studied by 99mTc-MIBI SPECT (long protocol) and coronary angiography. The extent of the uptake reversibility was quantified in 3 regions (antero-septal, inferior and lateral) of the polar maps, assessing the percentage of each region that had a > 10% difference resulting from the rest uptake minus the stress uptake. The regions dependent on one occluded artery were compared to those dependent on non-occluded arteries. In the regions dependent on one occluded artery a comparison was also made between those which had a good collateral circulation and those which did not. RESULTS: Fifty-four out of 149 patients (36%) had at least one occluded coronary artery (20 anterior descending, 22 right and 27 circumflex coronary arteries). In the visual analysis, reversible defects were observed in all patients with occlusion of the anterior descending and the right coronary artery, but only in half of the occlusions of the circumflex coronary artery. The extent of this reversibility was significantly higher in the regions dependent on occluded arteries and was highly variable, though lower when good collateral circulation was present. CONCLUSIONS: Reversible defects were always observed in the occlusions of the left anterior descending and right coronary arteries, but only in half of those of the circumflex artery. The extent of the ischemia was higher in the regions dependent on one occluded coronary artery, mainly when there was an absence of good collateral circulation.

Aged↗

PubMed2002

Characterization of tissue components in the temporomandibular joint disc and posterior disc attachment region: internal derangement and control autopsy specimens compared by morphometry.

PURPOSE: Our aim was to morphologically investigate the occurrence of fibroblasts, chondrocytes, and blood vessels in the tissue of the temporomandibular joint (TMJ) disc, the intermediate zone, and the posterior disc attachment region in control autopsy specimens and to compare the results with those observed in corresponding tissues from patients with TMJ internal derangement. PATIENTS AND METHODS: First, 20 bilateral TMJ disc specimens from selected autopsy cases were analyzed by conventional morphometry. Thus, the volume density of fibroblasts, chondrocytes, and blood vessels was determined. Second, the obtained results from the right joint of the autopsy disc specimens were compared with 12 TMJ disc specimens obtained at surgery from patients with internal derangement. RESULTS: The tissue compartments of interest (disc, intermediate zone, and posterior disc attachment region) were identified unequivocally in all specimens. None of the autopsy cases showed any significant difference between the right and left joints or related to gender. The only variable that differed between autopsy and patient specimens was volume density of blood vessels, which was higher in patient specimens. CONCLUSIONS: We found that the volume density of blood vessels was significantly higher in the posterior disc attachment region in patient specimens than in autopsy controls. Whether this reflects a role for vessels in the pathogenesis of TMJ internal derangement or merely is a reaction to another type of injury remains to be settled. In both the autopsy control and patient specimens, chondrocytes and fibroblasts were characteristic for disc respective posterior disc attachment region. Thus it appears that the occurrence of these cells can be used to distinguish TMJ disc from posterior disc attachment in small biopsy specimens.

Adolescent↗

PubMed1989

Prevalence and mechanisms of mitral regurgitation in the absence of intrinsic abnormalities of the mitral leaflets.

Two hundred nineteen consecutive patients referred for echocardiography were analyzed to determine the occurrence of mitral regurgitation (MR) in the absence of intrinsic abnormalities of the mitral leaflets. MR was assessed by means of the pulsed-Doppler technique. There was a higher incidence of MR associated with absence of mitral leaflet abnormalities compared to the presence of these abnormalities (59% vs 41%, p less than 0.01). The most common causes of MR were mitral annular calcification (MAC) and incomplete mitral leaflet closure (IMLC). The extent of calcific deposit in patients with MAC and the distance from the mitral leaflet coaptation point to the mitral annular plane in systole patients with IMLC correlated well with the severity of MR by Doppler technique (rho = 0.91 and 0.71, respectively). To determine the mechanisms of MR in these two conditions, 29 consecutive patients with MAC and 28 with IMLC were referred to the echocardiography laboratory, and 10 age-matched control subjects were prospectively analyzed. Patients with MAC had a 50% reduction in the sphincteric action of the mitral anulus in systole compared to control subjects. All patients with IMLC had poor left ventricular systolic function; most had left ventricular, mitral annular, and left atrial dilation, and only eight had regional wall motion abnormalities. When discriminant function analysis was used, poor left ventricular systolic function was the principal variable that separated patients with IMLC from normal subjects (F = 81.6, p less than 0.0001). We conclude that: (1) MR in adults occurs most commonly in the absence of intrinsic abnormalities of the mitral leaflets, primarily those resulting from MAC and IMLC; (2) MR in patients with MAC results from a reduced sphincteric action of the mitral anulus in systole; and (3) IMLC results from poor left ventricular systolic function, irrespective of the cause.

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PubMed2006

Asymmetry of shufflon-specific recombination sites in plasmid R64 inhibits recombination between direct sfx sequences.

The shufflon of plasmid R64 consists of four DNA segments separated and flanked by seven sfx recombination sites. Rci-mediated recombination between any inverted sfx sequences causes inversion of the DNA segments independently or in groups. The R64 shufflon selects one of seven pilV genes encoding type IV pilus adhesins, in which the N-terminal region is constant, while the C-terminal regions are variable. The R64 sfx sequences are asymmetric. The sfx central region and right arm sequences are conserved, but left arm sequences are not. Here we constructed a symmetric sfx sequence, in which the sfx left arm sequence was changed to the inverted repeat of the right arm sequence and made artificial shufflon segments carrying symmetric sfx sequences in inverted or direct orientations. The symmetric sfx sequence exhibited the highest inversion frequency in a shufflon segment flanked by two inverted sfx sequences. Rci-dependent deletion of a shufflon segment flanked by two direct symmetric sfx sequences was observed, suggesting that asymmetry of R64 sfx sequences inhibits recombination between direct sfx sequences. In addition, intermolecular recombination between symmetric sfx sequences was also observed. The extra C-terminal domain of Rci was shown to be essential for inversion of the R64 shufflon using asymmetric sfx sequences but not essential for recombination using symmetric sfx sequences, suggesting that the Rci C-terminal segment helps the binding of Rci to asymmetric sfx sequences. Rci protein lacking the C-terminal domain bound to both arms of symmetric sfx sequence but only to the right arm of asymmetric sfx sequence.

Base Sequence↗

PubMed1982

A noncomputerized count-based technique for the determination of resting left ventricular ejection fraction.

A noncomputerized, count-based technique for the determination of left ventricular ejection fraction (LVEF), which does not use geometric assumptions of left ventricular shape, was developed. The noncomputerized technique and computerized multigated ventriculography using both fixed and variable region-of-interest (ROI) methods were performed on 16 patients. The LVEFs obtained with the noncomputerized technique correlated well with both the fixed ROI computerized technique (r = .87) and the variable ROI computerized technique (r = .86). It is concluded that when a computer is not available, the noncomputerized technique is a valid alternative for the determination of LVEF in resting patients in stable sinus rhythm.

Cardiac Output↗

PubMed1995

Cardiac sympathetic denervation in transthyretin-related familial amyloidotic polyneuropathy: detection with iodine-123-MIBG.

In familial amyloidotic polyneuropathy (FAP), the peripheral nervous system is predominantly impaired. Cardiac sympathetic function has not been directly assessed. A 65-yr-old man with severe peripheral neuropathy due to primary systemic amyloidosis was studied. Echocardiograms and scintigraphic examinations with 20Tl and 99mTc-pyrophosphate demonstrated highly thickened but normally perfused left ventricular walls with intense diffuse amyloid deposits. No definite myocardial activity of [123I]metaiodobenzylguanidine (MIBG) was detected in any cardiac region, indicating lack of sympathetic nerve endings. Despite maintained cardiac contractility, left ventricular diastolic performance and heart rate variability assessed by power spectral analysis were markedly depressed. Thus, the myocardial defect of MIBG activity may provide direct evidence of impaired cardiac sympathetic nerve endings due to amyloid deposits in FAP.

3-Iodobenzylguanidine↗

PubMed2002

[Interindividual-variability of the analysis of regional myocardial wall function after myocardial infarction and revascularization].

PURPOSE: The gold standard for diagnosis myocardial viability is the functional recovery after revascularization. Aim of the study was to compare (1) qualitative analysis and (2) quantitative wall thickening by cine MRI and (3) circumferential shortening by tagged MRI the analysis of regional wall function of an infarcted area before and after revascularization. MATERIAL AND METHODS: Ten patients (age 60 +/- 11 years) with infarct-associated regional left ventricular wall motion abnormalities were examined by cine and tagged MRI on average two weeks after the myocardial infarction and re-examined three months after revascularization. Eight healthy volunteers served as a control for tagged MRI. Interobserver-variabilities of two observers were calculated using the kappa-statistics for grading of wall motion abnormalities as well as for detection of functional recovery by qualitative analysis, measurement of wall thickening of cine MRI, and measurement of circumferential shortening by tagged MRI, respectively. RESULTS: Grading of wall motion abnormalities revealed interobserver-variabilities of the study and control group of kappa = 0.8 and kappa = 0.84, kappa = 0.02 and kappa = 0.5, and kappa = 0.1 and kappa = 0.17 for qualitative analysis, wall thickening analysis and measurement of circumferential shortening, respectively. The interobserver-variability for the definition of wall motion recovery was kappa = 0.8 for all three methods. CONCLUSION: Qualitative analysis of wall motion abnormalities has the lowest interobserver-variability for the grading of wall motion abnormalities. The interobserver-variabilities of qualitative and quantitative analysis are comparable for the diagnosis of regional wall motion recovery. Thus, qualitative analysis of cine MRI can be used for grading regional wall motion in clinical studies.

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PubMed1985

The effects of coronary revascularization on left ventricular function in ischemic heart disease.

Although it is well established that coronary revascularization can reverse exercise-induced ischemic dysfunction, the effects on resting ventricular performance are controversial. From a group of 183 patients receiving surgical therapy for ischemic heart disease, 166 underwent bypass graft arteriography at an average of 7 to 14 days postoperatively. In 149 patients, satisfactory preoperative and postoperative biplane left ventriculograms were obtained. Regional wall motion was assessed by the 100 segment method of Sheehan and Dodge, and a perioperative change in shortening greater than 2 standard deviations of normal variability over 20 or more adjacent segments was considered significant. Ninety-five patients had stable or progressive angina, 88 had medically refractory unstable angina, 155 were in New York Heart Association Class IV, and 37 had a preoperative left ventricular ejection fraction of less than 0.4. Myocardial integrity was preserved with crystalloid cardioplegia and topical hypothermia. Seven hundred ninety-eight bypass grafts were performed (522 vein grafts and 276 mammary artery grafts), and 13 patients had concomitant left ventricular aneurysmectomy. Hospital mortality was 2.2%. The overall early graft patency rate was 95.9% (93.7% for vein grafts and 100% for mammary arteries). Only one patient had a decrement in regional wall motion, and 51 (37%) had significant postoperative improvement (27 in the unstable angina group and 24 in the stable angina group); in the patients with improved regional wall motion, ejection fraction increased by an average of 0.18 (p less than 0.01). Ejection fraction also improved after aneurysmectomy, and the increment seemed to result from both a reduction in end-diastolic volume and improved regional wall motion. Thus, reversible ischemic myocardial dysfunction appears to be common in the general population of patients undergoing coronary artery bypass grafting; 40% of patients with unstable angina and 34% of those with stable angina can be expected to have improved regional wall motion after successful revascularization. Finally, ventricular aneurysm resection significantly enhances left ventricular performance as assessed by ventriculographic ejection fraction.

Aged↗

PubMed1994

Precise accurate mineral measurements of excised sheep bones using X-ray densitometry.

An Hologic QDR 1000-W dual energy X-ray absorptiometer (DXA) was used to make a densitometric evaluation and to optimize ex vivo scanning and analysis conditions for excised sheep bones. Articulated lumbar spines and femora, removed at autopsy from eight 1-2-year-old cross-bred merino ewes, were studied using standard lumbar spine and hip protocols (version 4.20). Spine data were analysed with the ultra-high resolution (UHR) protocol (version 4.25). Preliminary hip measurements also were made using the lumbar spine (version 4.20) and scoliosis protocols (version 4.25). Bone mineral density (BMD) precision for the total hip (n = 5) was 0.4% using version 4.20, and 0.8% using the scoliosis protocol (version 4.25) but was 1.2-3.4% for femoral sub-regions. Precision for the lumbar spine was 0.8% (version 4.20). There was considerable variation in BMD and bone mineral content (BMC) at the same site between animals. Right and left hip BMD were highly correlated (r = 0.98, P < 0.00001). Measurement variables evaluated to determine the optimal conditions included: Hologic scanning protocols, depth of water immersion of bone and dimensions of the region of interest. Accuracy was determined by ashing. Use of the scoliosis protocol (version 4.25) gave the best results for proximal femur measurement. Measured BMC decreased by 4.4% as the water depth increased from 0 to 22.5 cm. At 5 cm water, BMC accuracy was 99% for the total hip, and BMD precision values (n = 3) were 0.3% (total hip) and 0.4% (femoral neck, trochanteric region and femoral shaft). The much-improved precision was attributed to use of a positioning device and to optimizing of the depth of water immersion. Rib segments (length 2.5 cm) were measured using the ultra-high resolution protocol (version 4.25). BMC accuracy determined using 6 ribs was best (100 +/- 2%) at 5 cm water. BMD precision (n = 5) was best (0.3%) at 0 cm water depth and was 0.5% at 4.5 cm water depth. Rib sample BMC (n = 15, 4.5 cm water depth) and ash weight were highly correlated (r = 0.985, P < 0.001). It is concluded that highly precise, accurate densitometry can be performed on excised small and large sheep bones. This technique will support studies evaluating the sheep as an animal model of human osteoporosis.

Absorptiometry, Photon↗

PubMed2003

Clinical significance and contributing factors of long-term variability in induced ventricular tachyarrhythmias.

UNLABELLED: Long-Term Variability in Induced Tachyarrhythmias. INTRODUCTION: Ventricular arrhythmias induced during electrophysiologic study (EPS) may vary over time, making arrhythmia induction studies unreliable. The aim of this prospective study was to clarify the clinical significance of long-term variability in induced arrhythmias and to elucidate factors determining this variability. METHODS AND RESULTS: Three noninvasive EPSs were performed 1, 13, and 25 months after implantation of a cardioverter defibrillator in 40 patients with ventricular tachyarrhythmias, without a change in their antiarrhythmic drug regimens. The induced ventricular arrhythmias were categorized into five grades. Long-term variability, which was defined as a variation in the grades during the three EPSs, was observed in 23 patients (group A) and not in the remaining 17 patients (group B). During the 2-year period, spontaneous sustained ventricular arrhythmias developed in 15 patients (65%) in group A but in only 4 patients (24%) in group B (P = 0.01). Inducibility of sustained tachyarrhythmias was not associated with emergence of spontaneous arrhythmias. All patients also underwent thallium-201 and iodine-123-metaiodobenzylguanidine (MIBG) scans to evaluate the extent of the regions showing normal thallium uptake with reduced MIBG uptake. Group A patients showed greater thallium/MIBG mismatched regions than did group B patients (P = 0.01). Logistic regression analysis revealed that long-term variability (relative risk [RR] 7.55, P = 0.03), amiodarone therapy (RR 0.14, P = 0.04), and left ventricular ejection fraction <35% (RR 6.26, P = 0.04) were independent predictors of spontaneous arrhythmia occurrence. CONCLUSION: In patients with ventricular tachyarrhythmias, long-term variability in induced arrhythmias, but not the inducibility of arrhythmias, is associated with a higher incidence of spontaneous arrhythmias. Regional cardiac sympathetic denervation may be an important mechanism of this variability. These results also may explain why inducibility-based antiarrhythmic drug testing does not predict patient prognosis.

Adaptation, Physiological↗

PubMed2005

Acetaminophen and myocardial stunning after transient ischemia in rabbit hearts.

BACKGROUND: Myocardial stunning is a lingering contractile dysfunction that occurs after brief ischemia, even in the absence of necrosis. Recent studies have shown that acetaminophen may have some benefit on the return of left ventricular function after brief global ischemia in an in vitro model. This study was conducted to determine whether treatment with acetaminophen results in enhanced myocardial tolerance to transient ischemia-reperfusion by improving left ventricular function and decreasing stunning in an in vivo model. METHODS: Anesthetized, open-chest rabbits were randomized to receive acetaminophen (37 mg/kg, n = 13) or saline (n = 11) 15 minutes before a series of transient coronary artery occlusions followed by reperfusion (three 10-minute periods of ischemia with 5 minutes reperfusion between). Hemodynamics and maximal and minimal values of developed pressure velocity (dP/dt) were measured at baseline, during ischemia, and throughout 2 hours of reperfusion. To assess myocardial stunning, echocardiography was used to determine regional systolic wall thickening fractions and global indices of function such as LV cavity dimensions and ejection fraction. RESULTS: Hemodynamic variables, including left ventricular systolic pressure and positive and negative dP/dt, were similar in both groups throughout the study. Left ventricular end-diastolic pressure was significantly lower in the acetaminophen group during occlusion and early reperfusion. The repeated short periods of ischemia in the free wall of the heart caused myocardial stunning in both groups. During ischemia, contractile function in the free wall was severely reduced, and although it improved during reperfusion, dysfunction persisted in the postischemic free wall after 2 hours of reflow, recovering to less than 52% of preischemic values (P < .01). The degree of dysfunction was similar in both groups. During ischemia, the end-diastolic left ventricular cavity area increased from 1.14 +/- 0.05 cm2 at baseline to 1.33 +/- 0.08 cm2 (P < .05) in controls, but had recovered after 2 hours of reflow. The end-diastolic area in acetaminophen-treated hearts increased from 1.13 +/- 0.08 cm2 at baseline to 1.35 +/- 0.08 cm2 during ischemia and also recovered 2 hours later. No significant differences in LV cavity areas were noted between the groups. Acetaminophen had no effect on changes in ejection fraction, which decreased similarly in both groups during ischemia to approximately 75% of baseline values. Although ejection fraction improved, it remained depressed at the end of reflow in both groups. CONCLUSION: Data from this study show that in a rabbit model of myocardial stunning, acetaminophen has a neutral effect on hemodynamics, recovery of fractional thickening, and on indices of global recovery such as left ventricular cavity dimensions or ejection fraction. Thus in the setting of experimental myocardial stunning, treatment with acetaminophen was safe but not cardioprotective.

Acetaminophen↗

PubMed1994

Lung volumes and distribution of regional air content determined by cine X-ray CT of pneumonectomized rabbits.

Lung volume, gradients in lung air content, and maximum in vivo lung dimensions were determined in rabbits in the prone, supine, and right and left lateral positions with a high-speed electron beam X-ray computed tomography scanner (Imatron C-100). Measurements were made at lung volumes corresponding to tracheal pressures of 0, 10, and 25 cmH2O. Three groups of rabbits were studied > or = 8 wk after surgery: sham-operated controls, left pneumonectomized, and left pneumonectomized with wax plombage. The magnitudes of the gradients in each direction (lung, length, width, and height) depended on lung volume and body position. The vertical gradient in air content was the largest in each group in each posture. In general, pneumonectomy did not influence the effects of the prone and supine positions on lung volume and volume distribution but did influence the effects of the right and left lateral positions on those variables. These results may be attributed to the variable effects of the mediastinal and abdominal contents on regional distending pressures.

Animals↗

PubMed1976

Myocardial imaging in the noninvasive evaluation of patients with suspected ischemic heart disease.

Three noninvasive radioactive tracer techniques for evaluating patients with ischemic heart disease are described: (1) myocaridal perfusion imaging, (2) acute infarct imaging, and (3) the gated blood pool scan. Myocardial perfusion imaging with tracers that distribute in the myocardium in relation to regional blood flow allows detection of patients with transmural and nontransmural infarction by the finding of decreased tracer concentration in the affected region of the myocardium. If these tracers are injected at the time of maximal stress to patients with significant coronary arterial stenosis but without infarction, areas of transient ischemia can be identified as zones of decreased tracer concentration not found when an examination is performed at rest. Acute infarct imaging with tracers that localize in acutely damaged tissue permits separation of patients with acute myocardial necrosis from those without infarction and those with more chronic damage. The gated blood pool scan permits assessment of left ventricular function and regional wall motion. The measurement of ventricular volumes, ejection fraction and regional wall motion adds significantly to the determination of hemodynamic variables in assessing patients with acute infarction. The technique also permits detection of right ventricular dysfunction. Performance of a combination of these radioactive tracer techniques is often advantageous, particularly in patients with suspected infarction. The techniques can establish whether infarction is present, whether it is acute, where the damage is located and how extensive it is; they can also provide a measure of the effect of this damage on left ventricular function.

Acute Disease↗

PubMed1991

Reasons for the lack of benefit of immediate angioplasty during recombinant tissue plasminogen activator therapy for acute myocardial infarction: a regional wall motion analysis. European Cooperative Study Group.

Regional ventricular wall motion analysis utilizing three different methods was performed on predischarge left ventriculograms from 291 of 367 patients enrolled in a randomized trial of single chain recombinant tissue-type plasminogen activator (rt-PA), aspirin and heparin with and without immediate angioplasty in patients with acute myocardial infarction. With univariate analysis, no difference in regional wall motion variables between the two treatment groups was observed. However, with individual baseline risk assessment by multivariate linear regression analysis using baseline characteristics known to be related to left ventricular function after thrombolytic therapy or outcome of coronary angioplasty, or both, an excess of high risk patients in the invasive treatment group was detected. To adjust for this unequal distribution of baseline risk, multivariate linear regression analysis was performed. No benefit of immediate coronary angioplasty was observed after adjustment. Reocclusion or reinfarction, or both, occurred more frequently in the invasive than in the noninvasive treatment group (18% versus 13%, respectively). Among patients with a patent infarct-related vessel on angiography between days 10 and 22 and without reinfarction before angiography, there was a trend toward benefit from the invasive strategy, indicating that reocclusion and reinfarction might be responsible for the lack of benefit of the invasive strategy. This implies that immediate coronary angioplasty may be beneficial in selected patients, provided that these complications can be prevented.

Angioplasty, Balloon, Coronary↗

PubMed1991

Variation between femurs as measured by dual energy X-ray absorptiometry (DEXA).

It is commonly assumed that there is minimal variation between the hips in an individual, but is densitometry of one femur representative of the other? We performed bone mineral density (BMD) measurements of both hips using a Hologic QDR 1000 densitometer. There were 110 patients, all of whom were right handed, and three main groups of subjects: (1) normal volunteers (n = 36); (2) subjects with known hip pathology (n = 36); (3) subjects with medical conditions not affecting the hip (n = 38). The mean age of the subjects was 46 (21-87) years and a standard analysis protocol was followed in all patients. The coefficient of variation (COV) for femurs was 0.9-3%, depending upon the region studied and the BMD. The left femur had a greater BMD 48% of the time and there were variable differences between femurs in each group studied. While the greatest differences were found in people with unilateral hip pathology, all groups had mean differences greater than the COV. It may be acceptable to study only one hip, but the large variation between femurs in individuals should be borne in mind when interpreting data.

Absorptiometry, Photon↗

PubMed1991

Augmented efficiency of regional myocardial work by ouabain.

STUDY OBJECTIVE: The effect of ouabain on regional myocardial mechanics and corresponding regional myocardial oxygen consumption was investigated. DESIGN: Regional myocardial segment length (ultrasonic dimension crystals) and force development (miniature strain gauge) were measured. The integrated multiples of myocardial shortening by corresponding force during an averaged beat was used to express regional segment work (= area under the systolic portion of the length-force loop). External cardiac work was calculated from aortic blood pressure and cardiac output. Global and regional myocardial O2 consumption (MVO2) were evaluated at baseline and during intravenous infusion of ouabain (7 micrograms.kg-1.min-1). Regional coronary blood flow was measured with radioactive microspheres, and microspectrophotometry of frozen myocardial biopsies was used to evaluate O2 saturation in small arteries and veins. These variables were used to calculate regional myocardial MVO2. Arterial and coronary sinus O2 saturation was used to calculate global left ventricular O2 consumption. Myocardial efficiency was expressed as regional work/regional myocardial MVO2. SUBJECTS: Ten open chest anaesthetised dogs, weight about 20 kg, were used. MEASUREMENTS AND MAIN RESULTS: Ouabain increased regional myocardial segment work [from 5291(SEM 1067) to 8916(2338) mm.g-1.min-1] to a greater extent than regional myocardial MVO2 [from 6.33(0.75) to 8.54(0.75) ml O2.min-1.100 g-1]. Regional efficiency was increased from 734(78) to 1036(160) g.mm.ml O2(-1).100 g-1. External efficiency was not raised. Percent shortening was increased to a greater extent than peak force development (+76% v + 38%), possibly indicating increased myocardial compliance. The length-force loop was shifted upward and to the right. CONCLUSIONS: Ouabain increases regional efficiency of myocardial contraction.

Animals↗

PubMed1997

Cardiac contractile function during coronary stenosis in dogs: association of adenosine in glycolytic dependence.

We tested the hypothesis that during critical coronary stenosis, endogenous adenosine alters myocardial glucose utilization to support myocardial contractile function (MCF). Anesthetized mongrel dogs were instrumented to measure hemodynamic variables, regional MCF (sonomicrometry), and substrate uptakes. Critical coronary artery stenosis was established with a screw clamp on the left circumflex coronary artery (LCX). Either 8-phenyltheophylline (3 x 10(-7) mol/min; adenosine-receptor blockade), iodoacetate (1 x 10(-5) mol/min; glycolysis blockade), or vehicle was infused into the LCX and the left anterior descending coronary artery (LAD). Critical coronary stenosis caused small decreases in arterial blood pressure and LCX blood flow, but no significant changes in MCF or other hemodynamics. There was a significant decrease in the O2 supply-to-consumption ratio in the stenotic region and an increased glucose uptake. Infusion of either 8-phenyltheophylline or iodoacetate caused a decrease in MCF in the stenotic LCX region concomitant with a decreased glucose uptake and without further changes in blood flow. This was not seen in the nonstenotic (LAD) region. These data support the hypothesis, indicating that glycolysis is vital for maintaining regional MCF during a decrease in the myocardial O2 supply-to-consumption ratio and that adenosine is important in this regard, independent of its vasoactive properties.

Adenosine↗

PubMed2002

Unusually prolonged progressing stroke: an expanding anterior cerebral artery infarction.

Progressive clinical deterioration over a period of weeks coupled with MRI evidence of infarction growth is quite uncommon. In this report, we describe a patient with an occluded left anterior cerebral artery (ACA) at the origin of the A2 segment. His symptoms attributable to a posteriorly located small infarction within the ACA territory slowly progressed during the following 8 weeks. A follow-up MRI revealed that the infarction had expanded to involve the whole region of the left ACA. Occasional patients like ours indicate that stroke is a dynamic disorder with an extremely variable clinical course and state of tissue injury.

Aged↗