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PubMed1989

Assessment of regional myocardial blood flow with myocardial contrast two-dimensional echocardiography.

It was hypothesized that regional myocardial blood flow could be measured using myocardial contrast echocardiography. Accordingly, arterial blood was perfused into the coronary circulation in 16 dogs. In Group 1 dogs (n = 8), blood flow to the cannulated left circumflex artery was controlled with use of a roller pump, whereas in Group 2 dogs (n = 8) blood flow to the left anterior descending coronary artery was controlled by a hydraulic occluder placed around it. Sonicated microbubbles (mean size 4 microns) were used as the contrast agent. In Group 1 dogs the microbubbles were injected subselectively into the left circumflex artery, whereas in Group 2 dogs they were injected selectively into the left main coronary artery and two-dimensional echocardiographic images were recorded. Computer-generated time-intensity curves were derived from these images and variables of these curves correlated with transmural blood flow measured with radiolabeled microspheres. A gamma-variate function (y = Ate-alpha t) best described the curves, and alpha (a variable of curve width) correlated well with transmural blood flow at different flow rates in all Group 1 and Group 2 dogs (mean r = 0.81 and 0.97, respectively). Other variables of the curve width also correlated well with myocardial blood flow, but peak intensity had a poor correlation with myocardial blood flow in both groups of dogs (r = 0.39 and r = 0.63, respectively). When data from all dogs were pooled, Group 1 dogs still showed good correlation between variables of curve width and myocardial blood flow (r = 0.81); Group 2 dogs did not (r = 0.45). The difference between the two sets of dogs was related to the site of contrast agent injection. It is concluded that measurement of the transit time of microbubbles through the myocardium with two-dimensional echocardiography accurately reflects regional myocardial blood flow. Although injection of contrast agent selectively into the left main coronary artery only allows measurement of relative flow, it may be feasible to measure absolute flow by injecting contrast agent subselectively into a coronary artery. Myocardial contrast echocardiography may, therefore, offer the unique opportunity of simultaneously assessing regional myocardial perfusion and function in vivo.

Animals↗

PubMed1997

Modulation of electrical heterogeneity by compensated hypertrophy in rat left ventricle.

Modulation of the regional distribution of the action potential by left ventricular hypertrophy and the role of the L-type Ca2+ current (I(Ca)) and transient outward current (I(to)) in the action potential duration (APD) were investigated in normal and hypertrophied rat ventricular myocytes from the apex (A), septum (S) and left ventricular free wall (FW) by using whole cell current- and voltage-clamp techniques. Hypertrophy was induced by abdominal aortic constriction. In control cells, the APD measured at 20% repolarization (APD20) assumed the shortest values in the A and the longest in the S, whereas FW cells showed intermediate values. Hypertrophy significantly prolonged the APD20 and increased APD variability within the A and FW regions but did not modify the APD in S cells. Analysis of the APD, I(Ca), and I(to) at the instant of 20% repolarization in the same cell showed that in control cells the shortest APD20 was associated with a prominent I(to) in the A and FW, whereas the long APD20 was identified with a lower I(to) in S myocytes. Hypertrophy-induced prolongation ofAPD20 was associated with a reduction in the I(to) in the A and FW. Significant correlations could be established between the APD20 and the "net current," defined as the algebraic addition of I(to) and I(Ca) in the A and FW control groups but not in the control S or hypertrophied cells whatever their origin. Our results indicate that interregional APD heterogeneity is lost while intraregional APD variability is increased in the A and FW during the hypertrophic process. These effects are largely due to a change in the balance between the I(Ca) and I(to), which is a major contributing factor to the heterogeneity of the initial phase of repolarization in the normal rat ventricle.

Action Potentials↗

PubMed1994

Detection of regional left ventricular asynchrony in obstructive hypertrophic cardiomyopathy by magnetic resonance imaging.

Cine magnetic resonance imaging was used to analyze global and regional left ventricular function in seven patients with obstructive hypertrophic cardiomyopathy (HC) and 10 normal subjects. In patients with HC a 38% higher left ventricular mass index (106.4 +/- 20.2 gm/m2 vs 77.0 +/- 16.1 gm/m2, p < 0.005) associated with a lower end-diastolic volume index (44.9 +/- 8.9 ml/m2 vs 58.3 +/- 9.0 ml/m2, p < 0.005) resulted in an 85% higher mass-to-volume ratio (2.4 +/- 0.52 vs 1.3 +/- 0.57, p < 0.0005). Stroke volume did not differ significantly, whereas ejection fraction was higher (80.4% +/- 6.5% vs 65.4% +/- 7.2%, p < 0.0005) in patients with HC. Although early diastolic filling fraction was smaller in patients with HC (61.0% +/- 22.8% vs 68.4% +/- 14.6%), the difference did not reach significance because of substantial variability. In patients with HC (in contrast to normal subjects) the time to maximal wall thickening was shorter (p < 0.025) in the hypertrophied basal region of the ventricle (223 +/- 42 msec) than in the apical region (267 +/- 35 msec), reflecting asynchrony between these regions. Additionally, in patients with HC the standard deviation of the time to maximal wall thickening in the basal region was significantly higher when compared with that of normal subjects (40.0 +/- 24 msec vs 16.9 +/- 17 msec, p < 0.0005), reflecting asynchrony even within one region. Thus magnetic resonance imaging can detect regional left ventricular asynchrony, an important cause of impaired diastolic function, in patients with HC and normal global systolic function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1983

Effects of acute hypercapnia on the central and peripheral circulation of conscious sheep.

We studied the cardiorespiratory effects of acute hypercapnia in 10 unanesthetized sheep. After a 15-min exposure to either 7.3 or 10% CO2 in air, we measured arterial blood gases, minute ventilation (VE), O2 consumption (VO2), cardiac output (Q), heart rate (HR), an index of left ventricular contractility [(dP/dt)/P], and vascular pressures. In addition, regional flows to all major organs were determined by injecting 15-microns radiolabeled microspheres into the left heart. Exposure to 7.3% CO2 (arterial CO2 partial pressure, PaCO2, 58 Torr) resulted in increased VE, (dP/dt)/P, and higher blood flows to the brain and respiratory muscles. All other variables remained unchanged. Exposure to 10% CO2 (PaCO2 75 Torr) resulted in a further augmentation of VE and a 48% increase in Q, which was associated with a tachycardia, a decrease in systemic vascular resistance, and an increase in VO2. Coronary and respiratory muscle flows increased, but all other variables remained unchanged. Thus the hemodynamic effects of hypercapnia are not related linearly to the level of PaCO2.

Acute Disease↗

PubMed1987

Relation between cardiac dyspnea and left ventricular function. A non-invasive study of 67-year-old men.

The relation of dyspnea of presumed cardiac origin to regional and global left ventricular (LV) function was evaluated among 67-year old men sampled from the general population of Gothenburg, Sweden. From a screened cohort of 644 men, 42 men with cardiac dyspnea and without obstructive pulmonary disease, and 45 controls were sampled. Dyspnea was measured and graded according to the World Health Organization standard. Two-dimensional and M-mode echocardiography, carotid pulse tracing, apexcardiography and phonocardiography were used to evaluate regional wall motion, systolic time intervals, LV ejection indices, wall stress, diastolic time intervals, direct and indirect indices of LV filling properties, and indices of pulmonary hypertension. The plasma concentrations of immunoreactive atrial natriuretic peptide (IrANP) and catecholamines were also assessed. The dyspneic men had more regional wall motion abnormalities than the controls. Systolic, as well as diastolic LV impairment, and increased LV mass were more abundant. Dyspnea grade was significantly related to either of these abnormalities in univariate analyses, and also in multivariate analyses when clinical information, such as chest X-ray, electrocardiogram, and clinical history were taken into account. Multivariate analyses of all the studied indices of cardiac function, together with clinical information, showed dyspnea grade to be significantly and independently related to mitral valve E-point to septal separation (EPSS), presence of akinetic segments, a history of angina pectoris, exercise capacity, and left atrial dimension. Taken together these variables explained 74% of dyspnea grade variance. There was also a relation between dyspnea grade and IrANP, which was independent of clinical findings, but only appeared under conditions of severe dyspnea. It is concluded that the degree of dyspnea is associated with a fairly similar progressive impairment of diastolic, regional and systolic function. In mild heart failure LV hypertrophy and diastolic abnormalities are more prevalent than systolic dysfunction. In severe dyspnea a mixture of regional, systolic, and diastolic abnormalities are present. A decrease of fractional shortening and increased levels of IrANP are late phenomena. EPSS may be a useful indicator of LV dysfunction in population studies.

Aged↗

PubMed1994

[Effects of coronary angioplasty on heart rate variability explored in the domain of time and frequency in patients with one-vessel coronary disease].

BACKGROUND: Heart period variability is frequently reduced in patients with coronary artery disease. Although the mechanism for this reduction is still unclear, it seems to reflect alterations in cardiac autonomic control. In this study we have evaluated the relation between reversible segmental left ventricular dysfunction and time and frequency domain measures of heart period variability in patients with coronary artery disease. METHODS AND RESULTS: Echocardiographic segmental left ventricular wall motion and time and frequency domain measures of heart period variability were evaluated in 32 patients with one-vessel coronary artery disease before and 16-24 days after successful percutaneous transluminal coronary angioplasty (PTCA). At baseline examination 12 patients (Group A) had normal and 20 (Group B) abnormal regional wall motion. Prevalence of previous myocardial infarction was higher and mean angiographic ejection fraction lower in Group B than in Group A. At baseline, time domain measures were comparable between the 2 groups, while low frequency (LF) and high frequency (HF) power were lower in Group B than in Group A. After PTCA, in Group A regional wall motion and time and frequency domain measures of heart period variability were unchanged. In Group B summed segment score improved from 17.1 +/- 3.6 to 12.8 +/- 2.0 (p < 0.01) and a significant increase occurred in standard deviation of the average normal RR (NN) intervals for all 5-minute segments of a 24-hour recording (SDNN index), in root mean square successive difference (r-MSSD) and in the percentage of differences between adjacent NN intervals > 50 msec (pNN50). In this group also LF and HF power (logarithmic units) increased from 6.14 +/- 0.23 to 6.35 +/- 0.34 (p < 0.01) and from 5.43 +/- 0.32 to 5.68 +/- 0.52 (p < 0.01) respectively. There was no correlation between measures of heart period variability, summed segment score, and left ventricular ejection fraction. CONCLUSIONS: This study demonstrates that segmental left ventricular dysfunction is involved in determining sympathovagal imbalance in patients with one-vessel coronary artery disease; the reversal of left ventricular dysfunction by successful PTCA improves heart period variability. These findings support the hypothesis that alterations in cardiac geometry may influence the discharge of afferent sympathetic mechanoreceptors, thus contributing to the derangement in autonomic control of heart rate.

Aged↗

PubMed1993

Systemic and regional haemodynamics in conscious BIO T0-2 cardiomyopathic hamsters.

OBJECTIVE: The recently developed BIO T0-2 strain of cardiomyopathic hamster shows a uniform pathogenesis of dilated cardiomyopathy and represents a useful model of congestive heart failure. Although used in biochemical studies, BIO T0-2 animals have not been characterised by haemodynamic measurements. The aim was to compare the systemic and the regional haemodynamic variables in conscious BIO T0-2 animals at a stage of compensated heart failure with those of age matched normal hamsters of BIO F1B designation. METHODS: Hamsters were studied at 8-10 months of age, a stage at which the BIO T0-2 animals have been found to have non-oedematous heart failure. Catheters were implanted in normal and cardiomyopathic hamsters. Following a 3 h recovery, systemic and regional haemodynamic variables were measured with pressure transducers and radioactive microspheres. RESULTS: BIO T0-2 hamsters had lower (p < 0.05) mean arterial pressure [83(SEM 3) v 126(2) mm Hg] and cardiac index [205(19) v 338(25) ml.min-1.kg-1], and higher (p < 0.05) left ventricular end diastolic pressure [21(1) v 4(1) mm Hg] and total peripheral resistance index [30(4) v 15(2) mm Hg.min.ml-1.kg-1] than BIO F1B animals. Blood flows to the heart and kidneys were less (p < 0.05) in BIO T0-2 than in BIO F1B animals. CONCLUSIONS: The haemodynamic profile in the BIO T0-2 strain of cardiomyopathic hamsters is characterised by low cardiac output, increased preload, and reduced renal blood flow, and resembles that in many patients with congestive heart failure.

Animals↗

PubMed1987

Effect of regional alveolar hypoxia on permeability pulmonary edema formation in dogs.

We studied the effects of regional alveolar hypoxia on permeability pulmonary edema formation. Anesthetized dogs had a bronchial divider placed so that the left lower lobe (LLL) could be ventilated with a hypoxic gas mixture (HGM) while the right lung was continuously ventilated with 100% O2. Bilateral permeability edema was induced with 0.05 ml/kg oleic acid and after 4 h of LLL ventilation with an HGM (n = 9) LLL gross weight was 161 +/- 13 (SE) g compared with 204 +/- 13 (SE) g (P less than 0.05) in the right lower lobe (RLL). Bloodless lobar water and dry weight were also significantly lower in the LLL as compared with the RLL of the study animals. In seven control animals in which the LLL fractional inspired concentration of O2 (FIO2) was 1.0 during permeability edema, there were no differences in gravimetric variables between LLL and RLL. In eight additional animals, pulmonary capillary pressure (Pc), measured by simultaneous occlusion of left pulmonary artery and vein, was not significantly different between LLL FIO2 of 1.0 and 0.05 either before or after pulmonary edema. We conclude that, in the presence of permeability pulmonary edema, regional alveolar hypoxia causes reduction in edema formation. The decreased edema formation during alveolar hypoxia is not due to a reduction in Pc.

Animals↗

PubMed2001

[Dumesnil's method: is it viable?].

BACKGROUND: Left ventricular (LV) ejection fraction (EF) is an indicator of left ventricular systolic function and is a potent predictor of cardiovascular mortality. LVEF is assessed by a variety of methods, however echocardiography is the most used in clinical practice. Simpson biplane multiple disc method (BMDM) is recommended by the American Society of Echocardiography; Dumesnil's method based on doppler echocardiography seems to be simpler and theoritically less influenced by distortion of LV geometry. OBJECTIVE AND METHODS: To assess the accuracy and reproducibility of Dumesnil's method a group of 100 patients proposed for coronarography with left ventricular angiography, prospectively underwent LVEF measurements by both BMDM and Dumesnil's method. RESULTS: Compared with LV angiography, the correlation coefficient for the Dumesnil's method was r = 0.85 and it was r = 0.9 for BMDM. Correlation in patients with LV regional asynergy were respectively r = 0.69 and r = 0.85. Intraobserver and interobserver variabilities were less then 7% for both echocardiographic methods. CONCLUSION: Although Dumesnil's method is less accurate than BMDM, it is simpler, more rapid with a satisfactory reliability and reproducibility.

Adult↗

PubMed1995

Large deletions in antigenic variants of the chlorella virus PBCV-1.

Four spontaneously derived, antigenic variants of chlorella virus PBCV-1 contained 27- to 37-kb deletions in the left end of the 330-kb genome. Two of the mutants, which were serologically identical, had deletions that began from map position 4.9 or 16 and ended at position 42.2 kb. In total, the two deleted regions encoded 28 putative functional open reading frames (ORFs); these deletions probably arose from homologous recombination. The other two mutants, which were serologically identical but distinct from the first two mutants, lacked the entire left terminal 37 kb of the PBCV-1 genome, including an identical 2.2-kb inverted terminal repeat region present at both ends of the wild-type genome. The deleted left end region was replaced by the transposition of an inverted 7.7- or 18.5-kb copy of the right end of the PBCV-1 genome. The region deleted in these two viruses encoded 26 single-copy ORFs, of which 23 were common to those deleted in the first two mutant viruses. The junctions of the deletions/transpositions probably arose from nonhomologous recombination. Taken together, the results indicate that 40.1 kb of single-copy DNA encoding 31 ORFs at the left end of the genome are unnecessary for PBCV-1 replication in Chlorella strain NC64A in the laboratory. The results also indicate that the size of the inverted terminal repeat region in this virus can be highly variable and that the PBCV-1 DNA packaging process tolerates large changes in genome size.

Antigenic Variation↗

PubMed2006

Exercise tissue Doppler echocardiography with strain rate imaging in healthy young individuals: feasibility, normal values and reproducibility.

PURPOSE OF THE STUDY: The study was done to determine the clinical feasibility and reproducibility of tissue Doppler echocardiography (TDE) with strain rate imaging (SRI) at rest and under physical exercise in healthy young individuals and to report normal values for parameters of regional myocardial function under exercise. METHODS: Forty-five young volunteers (age 9-29 years) underwent echocardiography with TDE/SRI at rest and during a bicycle exercise test (2 W/kg body weight). RESULTS: Velocities could be obtained in 93% of segments, whereas strain rate was measurable at least in 80% of segments. Inter- and intraobserver variability for measurement of velocities under exercise was 14% and 9%, respectively for strain rate 28% and 20%. Except for peak strain, values for all other parameters were higher during exercise with the clearest response in the left lateral and the right ventricular wall. CONCLUSIONS: (1) Tissue Doppler with strain rate imaging is a practical and robust method for assessment of regional function of both ventricles under exercise. (2) Systolic motion, local myocardial relaxation and contractility increased significantly under physical exercise. These normal values obtained from healthy young subjects can serve as a reference database for further clinical studies.

Adolescent↗

PubMed1984

Constructional apraxia as a function of lesion locus and size in patients with focal brain damage.

Patients with penetrating missile wounds confined to one of the four brain quadrants were evaluated to determine the incidence and severity of constructional apraxia. The visual constructive tasks used were the WAIS Block Designs subtest and the Bender Gestalt (reproduction) Test. Estimates of lesion size were used to investigate the effect of this factor on constructional ability. Patients with right posterior lesion tended to perform least adequately in general, although significant differences were obtained only for the Bender Gestalt Test. The effect for lesion laterality was greater than that for caudality , although neither analysis reached statistical significance. Lesion size made a relatively minor contribution to the visual constructional deficits in this sample. Only in the left posterior sample did lesion size correlate significantly with measures of constructional impairment. The lack of consistent findings may have been due to the restricted lesion size in these patients and to the absence of significant cognitive deficits in most subjects. The results support either a regional interpretation of the mass action theory or the possible role of deficient verbal mediation in the constructional performance of patients with left hemisphere lesions. This study emphasizes the importance in neurobehavioral research of controlling potentially confounding variables (e.g., lesion size and type of associated cognitive deficits) when studying any specific aspect of neuropsychological functioning.

Adolescent↗

PubMed1999

Phylogeographical structure of the Dover sole Microstomus pacificus: the larval retention hypothesis and genetic divergence along the deep continental slope of the northeastern Pacific Ocean.

Population genetic variability and phylogeographical structure of the Dover sole, Microstomus pacificus (Teleostei: Pleuronectidae), were examined along the continental slope of the north-eastern Pacific Ocean using sequences of the left domain of the mitochondrial DNA (mtDNA) control region. Six sites were sampled in three primary biogeographical provinces (based on surface water temperatures), ranging from the subarctic to the warm temperate zones. Many haplotypes were discerned, totalling 90 for 110 individuals. Neighbour joining and parsimony analyses of the entire data set showed that some groups of haplotypes of adult Dover sole were widely distributed, suggesting either panmixia or homoplasy and reversals. However, a substantial number of groups of related haplotypes were geographically circumscribed, and there were significant differences among sites in the distribution of restricted haplotypes (based on a reduced number of characters), supporting geographical structure. Geographical differentiation of populations appeared to be consistent with the member-vagrant hypothesis for retention of the pelagic larvae in currents and recruitment to adult habitats, reducing long-distance dispersal. Results of this study indicate phylogeographical structure among some populations, despite extended pelagic larval periods, and apparent environmental homogeneity in the adult habitats along the continental slope.

Animals↗

PubMed1995

Reproducibility of digital exercise echocardiography.

We determined the intra, inter-observer and temporal variability of upright bicycle exercise echocardiography in 50 consecutive patients with suspected coronary heart disease. Using significant artery stenoses as reference, the sensitivity of digital exercise echocardiography was 89% and the specificity 92%. Regarding the presence or absence of exercise-induced ischaemia, intra-observer agreement was 86% (73-94% with 95% confidence limits, kappa value (K) 0.70 (0.50-0.91)). Inter-observer agreement between two independent observers was 92 (81-98)% (K = 0.81 (0.63-0.99)). Temporal variability was examined by repeating exercise echocardiography after one week in 30 stable patients; it demonstrated 90 (78-97)% agreement (K = 0.71 (0.40-1.00)). The inter-observer agreement appeared to be lower in patients or myocardial segments with wall motion abnormalities at rest (86% and 82%, respectively) than in patients or segments with normal myocardial function at rest (96% and 94%, respectively); ns, P < 0.05, respectively). Analysis of specific regions showed a significantly higher level of agreement (P < 0.05) regarding exercise-induced ischaemia in segments supposed to be supplied by the circumflex branch of the left coronary artery (96%) than in the perfusion bed of the left anterior descending branch (87%) and right coronary artery (88%). Comparing estimated values of echocardiographic ejection fraction, analysis of intra-observer variability showed a correlation coefficient of 0.91 and 95% confidence limits of a single estimate of ejection fraction of +/- 10.3%. Corresponding analyses of inter-observer and temporal variability showed correlation coefficients of 0.93 and 0.84, respectively, and 95% confidence limits of single estimates of ejection fraction of +/- 9.6% and +/- 13.0%, respectively. Thus, the diagnostic result and the reproducibility of digital exercise echocardiography are satisfactory and comparable with those obtained by myocardial scintigraphy. However, approximately 10% of the examination results may be reversed when the test is repeated or reevaluated by the same or by another observer. The result seems to be less reproducible in patients with abnormal wall motion at rest than in patients with normal myocardial function before exercise.

Adult↗

PubMed1998

Importance of intrinsic calf vasodilator capacity in determining distribution of skeletal muscle perfusion during supine bicycle exercise in patients with left ventricular dysfunction.

BACKGROUND: Distribution of skeletal muscle perfusion during exercise is an important factor in determining exercise capacity and is markedly impaired in patients with cardiac disease. This study examined the importance of intrinsic calf vasodilator capacity in determining distribution of skeletal muscle perfusion during supine bicycle exercise in patients with left ventricular dysfunction. METHODS: We studied 19 patients with left ventricular dysfunction (left ventricular ejection fraction <45%) after myocardial infarction. All the patients underwent cardiopulmonary exercise testing with measurements of central hemodynamics, leg blood flow (LBF), and the percentage of cardiac output distributed to both legs (%LBF). Calf reactive hyperemic flow (RH) was measured by venous occlusive plethysmography at supine rest. RESULTS: LBF at peak exercise was closely related to peak cardiac output and RH. Furthermore, %LBF at peak exercise had modest correlation with peak cardiac output and good correlation with RH. Although peak cardiac output and RH were independent determinants of LBF at peak exercise by multiple regression analysis, RH had higher correlation with %LBF at peak exercise than peak cardiac output. Despite marked changes in other hemodynamic variables, nonleg blood flow during exercise was constantly maintained at a level identical to resting value. CONCLUSIONS: Calf vasodilator capacity, which was the major determinant of distribution of skeletal muscle perfusion during exercise, may have contributed to maintaining perfusion of important nonexercising regions during exercise in patients with left ventricular dysfunction.

Adult↗

PubMed1988

Clinical utility of exercise, pacing, and pharmacologic stress testing for the noninvasive determination of myocardial contractility and reserve.

The ability of the left ventricle to modulate its performance is an important and integral component in the cardiovascular system's adaptive response to increased workload. Abnormalities in ventricular contractility can blunt this response and thus significantly limit the patient's functional capacity. The accurate determination and quantitation of cardiac contractility and reserve is a difficult task in the symmetrically contracting ventricle and more so when regional contraction abnormalities are present. Moreover, derangements in other physiologic variables, such as ventricular loading conditions, heart rate, systemic vascular tone, cardiac autonomic function, and pulmonary gas exchange, can diminish cardiopulmonary reserve. This report relates the determinants of myocardial oxygen demand and efficiency to the currently available forms of exercise, pacing, and pharmacologic stress testing. Within this framework, commonly used as well as newer approaches to the noninvasive assessment of stress-induced changes in left ventricular performance and contractility are addressed. In addition, several examples are presented in which noninvasive techniques for assessing intracardiac structures, pressures, and flows (eg, echo/Doppler, radionuclide angiography, rapid acquisition computed tomography, and magnetic resonance imaging) are combined with various cardiovascular stress tests to achieve more reliable measures of myocardial contractility and reserve.

Cardiac Pacing, Artificial↗

PubMed1983

Microvascular evidence for a transition zone around a chronic myocardial infarct in the rat.

Muscle fibers in the transition zone of an infarcted heart are thought to be potentially ischemic during the first 6-9 h following coronary artery occlusion. However, the long-term fate of the muscle fibers at the margin of the necrosis is uncertain. Ischemia implies reduced oxygenation, possibly owing to a reduced capillary supply; thus our objective was to determine whether a region of reduced microvascular supply exists at the margin of a necrosis produced by chronic coronary artery occlusion. Five variables were used to quantitate the capillary supply in the transition zone: C/F (capillary to fiber) ratio, Vf (number of vessels around a fiber), Fv (number of fibers surrounding a vessel), capillary density, and fiber diameter. Infarcts were induced in young male rats by ligating the left coronary artery midway between its origin and the apex of the heart. Five weeks later, the capillary supply in the transition zone was significantly below control values, i.e., significant reductions in C/F, Vf, and Fv were found. This region of reduced capillary supply extended 225-525 microns laterally from the edge of the necrosis. Thus, a narrow transition zone, defined as a region of viable muscle fibers with a subnormal microvascular supply, exists as long as 5 weeks following coronary artery occlusion in the rat.

Animals↗

PubMed2007

Density and morphologic features of primary epidermal laminae in the feet of three-year-old racing Quarter Horses.

OBJECTIVE: To quantify the density of primary epidermal laminae (PELs) around the solar circumference and evaluate the relationship between regional PEL density and hoof capsule morphology in horses. SAMPLE POPULATION: Forefeet from nine 3-year-old Quarter Horse cadavers. PROCEDURES: Data pertaining to gross features of hoof morphology and PEL variables, including number, density, and distribution patterns around the perimeter of the hoof wall and number of bar PELs, were collected. Tissues of the laminar junction were examined histologically. RESULTS: No significant differences were found between left and right forefeet with respect to gross hoof morphologic measurements. Mean +/- SD number of PELs, including those at the bars of the hoof, was 551 +/- 30. Primary epidermal laminar density in the toe was significantly higher, compared with that in the quarter and heel regions, and was higher on the lateral aspect of the foot, compared with the medial aspect. Feet were significantly wider on the lateral aspect of the foot, compared with the medial aspect, as measured across the widest point of the solar surface. Histologic examination revealed atypical laminar morphology at the toe. CONCLUSIONS AND CLINICAL RELEVANCE: Variations were detected in PEL density and morphology around the solar circumference of hooves from 3-year-old racing Quarter Horses. A better understanding of relationships between laminar density, laminar morphology, and gross morphology of the hoof capsule in different populations of horses may aid practitioners in diagnosis and treatment of disease involving the hoof wall in horses.

Animals↗