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PubMed2002

[Prediction of in-stent restenosis by measurement of fractional flow reserve and the influence of diabetes mellitus].

OBJECTIVES: This study tried to predict in-stent restenosis by the measurement of fractional flow reserve and to evaluate the effect of diabetes mellitus control on the relationship between in-stent restenosis and fractional flow reserve. METHODS: Fractional flow reserve was measured in 62 patients (mean age 61 +/- 9 years, 32 with angina pectoris and 30 with myocardial infarction) after stent implantation. The patients were divided into three groups according to the value of HbA1c and fasting blood sugar (FBS): Group P (HbA1c > or = 6.5% or FBS > or = 126 mg/dl, n = 15), Group G (6.5% > HbA1c > or = 5.8% or 126 > FBS > or = 100 mg/dl, n = 12), and Group N (HbA1c < 5.8% and FBS < 100 mg/dl, n = 35). The relationship between fractional flow reserve at the end point of stent implantation and target lesion revascularization (TLR) was evaluated. RESULTS: In all patients, fractional flow reserve was 0.89 +/- 0.17 and percentage diameter stenosis was 17.6 +/- 11.6% after stent implantation. The TLR rate was 21%. Fractional flow reserve was significantly lower in patients with TLR (0.85 +/- 0.08 vs 0.91 +/- 0.06, p < 0.01). Fractional flow reserve was significantly lower in patients with TLR in Groups N and G (Group N: 0.85 +/- 0.04 vs 0.91 +/- 0.06, p < 0.05, Group G: 0.77 +/- 0.06 vs 0.91 +/- 0.05, p < 0.01). Fractional flow reserve showed no significant difference between patients with TLR and without TLR in Group P (0.85 +/- 0.10 vs 0.87 +/- 0.08, p = NS). In patients with optimal results (fractional flow reserve > or = 0.90), TLR rate was 60% in Group P, 0% in Group G and 0% in Group N. CONCLUSIONS: Fractional flow reserve after stent implantation is useful for the prediction of TLR in patients without diabetes mellitus. However, diabetic control in patients with diabetes mellitus might be attributable to TLR rather than fractional flow reserve.

Aged↗
PubMed2002

Perfusion and contractile reserve in chronic dysfunctional myocardium: relation to functional outcome after surgical revascularization.

BACKGROUND: Chronic dysfunctional but viable myocardium may exhibit contractile reserve and/or intact perfusion. Segments with intact perfusion without contractile reserve are frequently observed inpatients with ischemic cardiomyopathy. The clinical relevance of this observation is unclear; in particular, the functional outcome after revascularization is unknown. Thus, contractile reserve (using low-dose dobutamine echocardiography) and perfusion (using resting (99m)Tc tetrofosmin) were evaluated in 114 patients with ischemic cardiomyopathy and the findings were related to functional outcome (9 to 12 months after revascularization). METHODS AND RESULTS: Patients (n=114) with ischemic cardiomyopathy undergoing surgical revascularization were evaluated for perfusion (using (99m)Tc tetrofosmin) and contractile reserve (using low-dose dobutamine echocardiography). Contractile function (two-dimensional echocardiography) was assessed before and 9 to 12 months after revascularization. In the 1 336 dysfunctional segments, perfusion was preserved in 51% of the segments and contractile reserve in 31% (P<.05); 47% of the segments with perfusion did not exhibit contractile reserve. The majority (66%) of segments with recovery of function postrevascularization had intact perfusion and contractile reserve; the majority (58%) of segments without functional recovery lacked both perfusion and contractile reserve. Interestingly, 22% of segments with functional recovery and 25% of segments without functional recovery showed intact perfusion without contractile reserve. CONCLUSION: Segments with intact perfusion/contractile reserve have a high likelihood of recovery of function postrevascularization; segments without contractile reserve/perfusion have a low likelihood of recovery and segments with intact perfusion without contractile reserve have an intermediate likelihood of recovery.

Angina Pectoris↗
PubMed2006

Reduced vascular reserve measured by stressed single photon emission computed tomography carries a high risk for stroke in patients with carotid stenosis.

AIM: A few studies have observed reduced vascular reserve measured by single photon emission computed tomography (SPECT) to be a risk factor for stroke in patients with carotid artery occlusion, but stenosis has been excluded from these former studies. This study has evaluated the prognosis of reduced vascular reserve in patients with stenosis, and the effect of carotid endarterectomy (CEA) on these patients. METHODS: Forty patients diagnosed as having >70% stenosis of the carotid artery at the University of Tokyo Hospital, between 2001 and 2004, underwent acetazolamide-stress SPECT test first. A resting SPECT study was performed on a different day from the stressed SPECT study. The patients were grouped as having reduced vascular reserve or normal vascular reserve from the SPECT results. Analysis of risk factors and the stroke-free curve analysis for reduced vascular reserve was performed. RESULTS: Of the 40 patients, 24 (60%) had reduced vascular reserve and 18 underwent CEA. The mean follow-up period was 21.5+/-15.5 months (mean+/-SD). Four strokes occurred during follow-up: in 1 patient with CEA and 3 without CEA. All stroke patients had reduced vascular reserve. The patients with reduced vascular reserve without any surgery had a significantly lower stroke-free rate compared with those with normal vascular reserve or reduced vascular reserve, but also receiving CEA. CONCLUSIONS: We propose performing SPECT tests in patients with severe carotid stenosis regardless of symptoms, and performing CEA on those with a reduction in vascular reserve.

Aged↗
PubMed1991

[Prognostic significance of the electrocardiographic coronary reserve in stable angina].

We've studied the prognostic significance of the electrocardiographic coronary reserve, evaluated by seried effort tests, in patients with stable angina and proved coronary disease. Seventy-three patients with stable angina, who performed 2 exercise tests (basal and after vasodilator therapy) were included. It's considered variable reserve when in the second test the ST-descent improves greater than or equal to 1 mm for equal or higher double product (43 patients) and fixed reserve when it doesn't (30 patients). All of them underwent to coronariography study. The exercise test was seried each term during the first year. Clinical follow-up lasted 3 years and we considered cardiac events: myocardial infarction, unstable angina, surgery, PTCA or death. Patients with fixed reserve had higher maximal ST-descent (2.5 +/- 0.7 vs 1.9 +/- 0.6; p less than 0.05), lesser effort-time (359 +/- 144 vs 430 +/- 112; p less than 0.05), and more severe coronary disease (score: 3.5 +/- 1.5 vs 2.4 +/- 0.8; p less than 0.01) as compared with variable reserve group. Unfavorable clinic evolution was similar in both groups (44.3% in the fixed reserve group and 34.8% in the variable reserve group). We verified that 92.3% of patients with variable reserve who didn't modify its character in a year had good evolution; 76.4% of patients who changed to fixed reserve had unfavorable evolution (significant association, p less than 0.01). We conclude that in patients with variable reserve, the periodic evaluation of the reserve character has important prognostic implication.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1996

Influence of cognitive reserve on neuropsychological functioning in asymptomatic human immunodeficiency virus-1 infection.

OBJECTIVE: To evaluate the influence of cognitive reserve or brain reserve capacity on neuropsychological performance in early human immunodeficiency virus (HIV)-1 infection. DESIGN: Cross-sectional group comparison study, based on neuropsychological performance, of HIV-1 seropositive and HIV-1 seronegative participants. SUBJECTS: Seventy-five medically asymptomatic HIV-1-seropositive homosexual or bisexual men and 50 HIV-1-seronegative homosexual or bisexual male controls. Subjects were grouped by HIV-1 status (seropositive vs seronegative) and by cognitive reserve scores (low reserve vs high reserve). MEASURES: Cognitive reserve scores were based on a combination of years of education, a measure of occupational attainment, and an estimate of premorbid intelligence. Performance on a battery of neuropsychological tests was summarized by empirically derived factor scores and clinical summary ratings. RESULTS: The HIV-1-seropositive subjects with low cognitive reserve scores exhibited significantly greater deficits on measures of attention and information processing speed, verbal learning and memory, executive functioning, and visuospatial performance than did the HIV-1-seropositive subjects with high cognitive reserve scores. In contrast, there were no significant group differences on these measures between both groups of HIV-1-seronegative subjects. CONCLUSIONS: Early neuropsychological impairments in HIV-1 infection are most evident in individuals with lower cognitive reserve. As has been found in other neurologic disorders, such as Alzheimer's disease, individuals with greater cognitive reserve may be less sensitive to the initial clinical effects of the underlying neuropathologic process.

Adolescent↗
PubMed1986

Dipyridamole versus intracoronary injection of contrast medium for the evaluation of coronary reserve in man: a comparative study.

Coronary reserve can be assessed by the ratio of coronary blood flow after "maximum" vasodilation to control flow. The intravenous infusion of dipyridamole (0.56 mg X kg-1) is considered to elicit maximum coronary vasodilation. The present study was designed to compare coronary flow and resistance responses to intravenous dipyridamole and intracoronary injection of contrast medium (ioxaglate), this latter technique being frequently used in digital radiology to stimulate hyperemia. The comparison was performed in seven normal patients, nine patients with coronary artery disease, and 16 patients with dilated cardiomyopathy. Coronary flow reserve was calculated as the ratio of peak flow after dipyridamole or contrast medium to control flow, and coronary resistance reserve was calculated as the ratio of minimal to control coronary resistance after each stimulus. Although flow reserve after dipyridamole was approximately twice that obtained after contrast medium in the normal group (4.01 +/- 0.56 vs 2.02 +/- 0.24) there was a close and linear relationship between coronary flow and resistance reserve estimated by both techniques (r = 0.846, p less than 0.001 for flow reserve ratios, and r = 0.844 p less than 0.001 for resistance reserve ratios). However, contrast-induced hyperemia identified 13/25 (52%) of patients with coronary artery disease or dilated cardiomyopathy as having a reduced flow reserve, while dipyridamole revealed a restrained coronary flow reserve in 20/25 (80%) of these patients. Similar proportions were obtained when using coronary resistance reserve (56% for contrast vs 80% for dipyridamole). (ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Superiority of intracoronary papaverine to radiographic contrast for measuring coronary flow reserve in patients with ischemic heart disease.

Measurement of coronary flow reserve has been suggested as an adjunct to anatomic assessment of coronary stenoses in patients with ischemic heart disease. We compared papaverine hydrochloride and radiographic contrast to determine which agent was superior for the determination of coronary flow reserve. Coronary flow reserve was determined during cardiac catheterization by means of digital coronary angiography and parametric imaging. Two groups of patients were studied. Among patients in group 1, coronary flow reserve was determined by means of both papaverine and contrast. In group 1 patients with normal coronary arteries, papaverine-induced flow reserve was greater than contrast-induced reserve in all but one vascular region (n = 9, 4.98 +/- 1.15 vs 3.56 +/- 0.89; p = 0.29). Group 1 patients with coronary disease also demonstrated significantly greater flow reserve with papaverine (n = 25, 2.57 +/- 0.20 vs 1.83 +/- 0.11, p less than 0.01). Group 2 included patients with single-vessel coronary artery stenoses. These patients were studied by means of either papaverine or contrast to determine coronary flow reserve for both the stenotic "ischemic" region and an adjacent nonstenotic, "nonischemic" region. Those patients in group 2 who were studied by means of contrast had a modest difference between flow reserve values in the nonischemic and those in the ischemic regions (n = 15, 1.78 +/- 0.10 vs 1.26 +/- 0.09; p less than .0001) with considerable overlap. Patients studied by means of papaverine had a much greater separation in flow reserve between nonischemic and ischemic regions (n = 22, 2.78 +/- 0.19 vs 1.46 +/- 0.14; p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1987

Assessment of coronary flow reserve using digital angiography before and after successful percutaneous transluminal coronary angioplasty.

Important alterations of coronary blood flow and coronary flow reserve occur during percutaneous transluminal coronary angioplasty (PTCA). This study evaluated these alterations using digital subtraction angiography. Coronary flow reserve was determined before and after successful PTCA in 20 patients with 1-vessel coronary artery disease (CAD). Ten other patients with angiographically normal coronary arteries, normal exercise electrocardiographic responses and normal cardiac structure also were evaluated. Coronary flow reserve was calculated as the ratio of papavarine-induced hyperemic flow to basal flow. Flow reserve for the stenotic artery in patients who underwent PTCA was 1.6 +/- 0.2 (mean +/- standard error of the mean) (range 0.9 to 3.9, n = 20). After successful PTCA, flow reserve for this artery increased to 3.1 +/- 0.2 (range 1.7 to 5.2, n = 20) (p less than 0.0001 vs before PTCA). Flow reserve for adjacent nonstenotic, nondilated arteries was 2.6 +/- 0.2 (range 1.4 to 4.5, n = 13). Coronary flow reserve in the stenotic arteries before PTCA was far below normal. In addition, both successfully dilated arteries and nondilated, nonstenotic arteries in these patients with CAD had flow reserve values smaller than those in the patients with normal arteries (4.8 +/- 0.6, range 2.3 to 12.6, n =22) (p less than 0.01). These findings suggest that digital angiographic determinations of coronary flow reserve can reveal important alterations of individual artery vasodilatory capacity. The data suggest that although an epicardial coronary in a patient with CAD may appear angiographically normal, flow reserve remains impaired due to abnormalities as yet undefined.

Adult↗
PubMed1996

Relative heart rate, heart rate reserve, and VO2 during submaximal exercise in the elderly.

BACKGROUND: The purpose of this study was to examine the relationships among relative maximal heart rate (%HRmax), maximal heart rate reserve (%HRmax reserve), and maximal oxygen uptake (%VO2max) during submaximal exercise by elderly subjects. METHODS: VO2max and HRmax were determined on 36 women and 19 men, 60 to 80 yrs of age, by a maximal treadmill test to volitional exhaustion. On a separate day, subjects underwent a submaximal treadmill protocol consisting of three 6-min exercise stages at treadmill speeds and grades estimated to elicit 40%, 60%, and 80% of HRmax reserve. Cardiorespiratory responses were determined during mins 4-5 and 5-6 of each stage. RESULTS: Measured exercise intensities expressed by the three methods were: %HRmax reserve = 36, 55, and 79%; %HRmax = 65, 75, and 88%; %VO2max = 53, 69, and 88%. %HRmax was greater (p < .05) than %VO2max at 53 and 69% of VO2max. %HRmax reserve was less (p < .05) than %VO2max for all three intensities. Slopes and intercepts for the linear regression equations relating %VO2max with %HRmax and with %HRmax reserve differed between men and women (p < .05). The regression equation relating %VO2max and %HRmax was y = -22.8 + 1.2 (%HRmax) -13.0 (Gender) + 0.2 (%HRmax x Gender): standard error of the estimate (SEE) = 9.7% and R2 = .71. The regression equation relating %VO2max and %HRmax reserve was y = 32.4 + 0.7 (%HRmax reserve) -10.9 (Gender) + 0.2 (%HRmax reserve x Gender): SEE = 9.8% and R2 = .70 (Gender: F = 0; M = 1). CONCLUSIONS: The data indicate that there is considerable variability among methods of expressing exercise intensity and that %HRmax more closely represents %VO2max than does %HRmax reserve (p < .05) in older adults. These results are in contrast to what has been shown with younger subjects and with American College of Sports Medicine guidelines for exercise prescription.

Aged↗
PubMed2002

Growth of young apple trees in relation to reserve nitrogen and carbohydrates.

Bench-grafted Fuji/M.26 apple (Malus domestica Borkh.) trees were fertilized with a nutrient solution (fertigation) containing 0, 2.5, 5, 7.5, 10, 15 or 20 mM nitrogen (N) in a modified Hoagland's solution from June 30 to September 1. In mid-October, half of the trees in each N treatment were sprayed twice with 3% urea, 1 week apart. The remaining trees served as controls. All trees were harvested after leaf fall and stored at 2 degrees C over winter. One group of trees from each treatment was destructively sampled before bud break to determine amounts of reserve N and total nonstructural carbohydrates (TNC); the remaining trees were transplanted to N-free medium in the spring. These trees were supplied with Hoagland's solution with or without 10 mM N (from 15N-depleted NH4NO3) for 60 days, starting from bud break. With increasing N supply from fertigation, tree N concentration increased, whereas TNC concentration decreased. Foliar urea applications increased tree N concentration and decreased TNC concentration in each N fertigation treatment. There was a negative linear relationship between tree N concentration and TNC concentration. Irrespective of whether N was provided the following spring, trees with high N reserves but low carbohydrate reserves produced a larger total leaf area at the end of the regrowth period than trees with low N reserves but high carbohydrate reserves. The pooled data on reserve N used for new growth showed that, regardless of the spring N supply, there was a linear relationship between total N accumulated in the tree during the previous season and the amount of reserve N remobilized for new shoot and leaf growth. About 50% of tree N content was remobilized to support new shoot and leaf growth over the range of tree N status examined. We conclude that the initial growth of young apple trees in the spring is determined mainly by reserve N, not reserve carbohydrates. The amount of reserve N remobilized for new growth in spring was proportional to tree N status and was unaffected by current N supply.

Biomass↗
PubMed1997

Myocardial perfusion reserve: assessment with multisection, quantitative, first-pass MR imaging.

PURPOSE: To demonstrate the feasibility of determining myocardial blood flow changes and the myocardial perfusion reserve with magnetic resonance (MR) first-pass imaging, to validate the MR results by means of comparison with radiolabeled microsphere flow measurements in an animal model, and to compare the coronary flow reserve with the perfusion reserve at MR imaging in patients with hemodynamically nonsignificant coronary lesions and angina. MATERIALS AND METHODS: Arrhythmia-insensitive, first-pass, multisection, T1-weighted MR imaging with contrast agent enhancement was performed in eight pigs with acute ischemia and in eight adult patients (six women, two men). In the pigs, microsphere flow measurements were obtained in parallel with the MR measurements. In the patients, the coronary flow reserve was measured with an intracoronary Doppler flow ultrasound probe for comparison with the MR perfusion reserve. RESULTS: In the animal studies, there was linear correlation between MR perfusion indexes and the microsphere flow measurements (r = .88, P < .01). In the patients, the regional perfusion reserve matched the coronary flow reserve (linear regression with a slope of 1.02 +/- 0.09, r = .80). CONCLUSION: The myocardial perfusion reserve can be quantified with first-pass MR imaging. In patients with microvascular dysfunction, the myocardial perfusion reserve matches the reduced coronary flow reserve.

Animals↗
PubMed2006

Reserve networks based on richness hotspots and representation vary with scale.

While the importance of spatial scale in ecology is well established, few studies have investigated the impact of data grain on conservation planning outcomes. In this study, we compared species richness hotspot and representation networks developed at five grain sizes. We used species distribution maps for mammals and birds developed by the Arizona and New Mexico Gap Analysis Programs (GAP) to produce 1-km2, 100-kmn2, 625-km2, 2500-km2, and 10,000-km2 grid cell resolution distribution maps. We used these distribution maps to generate species richness and hotspot (95th quantile) maps for each taxon in each state. Species composition information at each grain size was used to develop two types of representation networks using the reserve selection software MARXAN. Reserve selection analyses were restricted to Arizona birds due to considerable computation requirements. We used MARXAN to create best reserve networks based on the minimum area required to represent each species at least once and equal area networks based on irreplaceability values. We also measured the median area of each species' distribution included in hotspot (mammals and birds of Arizona and New Mexico) and irreplaceability (Arizona birds) networks across all species. Mean area overlap between richness hotspot reserves identified at the five grain sizes was 29% (grand mean for four within-taxon/state comparisons), mean overlap for irreplaceability reserve networks was 32%, and mean overlap for best reserve networks was 53%. Hotspots for mammals and birds showed low overlap with a mean of 30%. Comparison of hotspots and irreplaceability networks showed very low overlap with a mean of 13%. For hotspots, median species distribution area protected within reserves declined monotonically from a high of 11% for 1-km2 networks down to 6% for 10,000-km2 networks. Irreplaceability networks showed a similar, but more variable, pattern of decline. This work clearly shows that map resolution has a profound effect on conservation planning outcomes and that hotspot and representation outcomes may be strikingly dissimilar. Thus, conservation planning is scale dependent, such that reserves developed using coarse-grained data do not subsume fine-grained reserves. Moreover, preserving both full species representation and species rich areas may require combined reserve design strategies.

Animals↗
PubMed2006

Dispersal per recruit: an efficient method for assessing sustainability in marine reserve networks.

Marine reserves are an increasingly important tool for the management of marine ecosystems around the world. However, the effects of proposed marine reserve configurations on sustainability and yield of populations are typically not estimated because of the computational intensity of direct simulation and uncertainty in larval dispersal and density-dependent recruitment. Here we develop a method for efficiently assessing a marine reserve configuration for persistence and yield of a population with sedentary adults and dispersing larvae. The method extends the familiar sustainability criteria of individual replacement for single populations based on eggs-per-recruit (EPR) to spatially distributed populations with sedentary adults, a dispersing larval phase, and limited carrying capacity in the settlement-recruit relationship. We refer to this approach as dispersal-per-recruit (DPR). In some cases, a single DPR calculation, based on the assumption that post-settlement habitat is saturated (i.e., at maximum recruitment), is sufficient to determine population persistence, while in other cases further iterative calculations are required. These additional calculations reach an equilibrium more rapidly than a full simulation of age- or size-structured populations. From the DPR result, fishery yield can be computed from yield-per-recruit (YPR) at each point. We assess the utility of DPR calculations by applying them to single reserves, uniformly distributed systems of reserves, and randomly sized and spaced systems of reserves on a linear coastline. We find that for low levels of EPR in fished areas (e.g., 10% or less of the natural, unfished EPR when post-settlement habitats are saturated by 35% of natural settlement), a single DPR calculation is sufficient to determine persistence of the population. We also show that, in uniform systems of reserves with finite reserve size, maximal fisheries yield occurs when the density of reserves is such that all post-settlement habitat is nearly saturated with settlers. Finally, we demonstrate the application of this approach to a realistic proposed marine reserve configuration.

Animals↗
PubMed2001

[Clinical significance of coronary flow reserve in hypertrophied heart: comparison with Doppler index, hemodynamics and plasma natriuretic peptide concentrations].

OBJECTIVES: The relationship was investigated between coronary flow reserve and Doppler echocardiographic parameters, hemodynamic parameters and plasma natriuretic peptide concentrations in the hypertrophied heart. METHODS: The subjects were 19 patients with hypertrophied heart due to various etiologies and no significant coronary artery stenosis. All patients were in sinus rhythm. The left ventricular wall thickness, the E/A ratio in transmitral flow velocity pattern and the Doppler index were determined by Doppler echocardiography, and the plasma atrial and brain natriuretic peptide concentrations were measured. At cardiac catheterization, pulmonary capillary wedge pressure and left ventricular end-diastolic pressure were measured, and the coronary flow reserve was obtained by injecting intracoronary adenosine triphosphate into the left anterior descending artery using a Doppler guidewire. RESULTS: Coronary flow reserve in the patients was significantly lower than in 11 normal control subjects (2.50 +/- 0.76 vs 3.90 +/- 0.64, p < 0.001). There were no significant correlations between coronary flow reserve and the left ventricular wall thickness or the E/A ratio. The mean value of the Doppler index in the patients was 0.48 +/- 0.10 and there was a significant negative correlation between coronary flow reserve and the Doppler index (r = -0.73, p < 0.001). The correlation between coronary flow reserve and left ventricular end-diastolic pressure was not significant, but there was a significant negative correlation between coronary flow reserve and pulmonary capillary wedge pressure (r = -0.64, p < 0.01). There were significant negative correlations between coronary flow reserve and atrial (r = -0.62, p < 0.01), or brain natriuretic peptide concentrations (r = -0.56, p < 0.05). CONCLUSIONS: Coronary flow reserve may reflect overall cardiac performance evaluated by the Doppler index and plasma natriuretic peptide concentrations in the hypertrophied heart, and the measurement of coronary flow reserve may be useful for evaluating disease severity in patients with hypertrophied heart.

Aged↗
PubMed1990

[Clinical and angiographic expression of myocardial ischemia in stable angina as a function of its coronary reserve].

We have studied the distribution of the coronary reserve, evaluated by serial effort tests, in patients with proved coronaropathy, determining the correlation between clinic (effort and mixed angina) and coronary reserve (fixed and variable), assessing angiographic findings in function to that reserve. We took 120 patients with stable angina to whom 2 effort tests were performed, basal and after vasodilator drugs. It was considered variable reserve if in the second test the S-T descend improved greater than or equal to 1 mm for a similar of greater double product and fixed when it didn't improve. In all patients coronarography was performed. Seventy two patients (60%) showed fixed reserve, 58 with effort angina (80%) and 14 (20%) with mixed. Forty eight showed variable reserve, 40 (80%) with mixed angina and 8 (17%) with effort. The group with fixed reserve had a greater S-T max. descent (2.9 +/- 0.9 vs 2.2 +/- 0.4) (p less than 0.001), a lower double product max. (221 +/- 44 vs 284 +/- 37) (p less than 0.001) and a lower maximal oxygen consumption (MVO2 7 +/- 2 vs 11 +/- 2) (p less than 0.001) than the variable reserve group. Considering the angiography, the fixed reserve group had more number of vessels affected (1.9 +/- 0.7 vs 1.4 +/- 0.5) (p less than 0.01), a higher angiographic score (4.88 +/- 2.4 vs 2.2 +/- 1.2) (p less than 0.001), a lower ejection fraction (59 +/- 8.5 vs 65 +/- 7.5) (p less than 0.001), more multivessel and descending anterior artery lesion than the variable reserve group.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1996

Depletion of energy reserve via the creatine kinase reaction during the evolution of heart failure in cardiomyopathic hamsters.

To study the contribution of myocardial energy reserve to the deterioration of cardiac function during the development of heart failure, we defined energy reserve via the creatine kinase (CK) reaction and the isovolumic contractile performance in hearts of cardiomyopathic hamsters at the ages of 1.5, 4, 17, 30 and 43 weeks and in age-matched normal hamsters. Energy reserve via the CK reaction was estimated by the product of total CK activity and the content of total creatine in the heart. Isovolumic contractile performance was measured as rate pressure product (RPP, 10(3) mmHg/min) in isolated hearts. Contractile reserve was assessed as the increase of RPP elicited by high calcium stimulation. Compared to the controls, decreases in total CK activity and content of total creatine were observed in hearts of 17-, 30- and 43-week-old cardiomyopathic hamsters. These changes were not observed in the skeletal muscle. Although the decrease of baseline RPP first occurred at the age of 30 weeks (11.5 +/- 0.9 v 20.5 +/- 0.8, P < 0.05), the contractile reserve was already reduced at the age of 17 weeks (9.9 +/- 1.3 v 23.6 +/- 1.9, P < 0.05). A linear relationship was found between the energy reserve via creatine kinase reaction and the contractile reserve of the heart (r2 = 0.85). Furthermore, concomitant decreases in the CK reaction velocity and the contractile reserve were observed in cardiomyopathic hearts, suggesting that depletion of energy reserve may contribute to the development of heart failure.

Age Factors↗
PubMed2000

On optimal size and number of reserves for metapopulation persistence.

Habitat fragmentation is generally considered to be detrimental to the persistence of natural populations. In nature management, one therefore tends to prefer few large nature reserves over many small nature reserves having equal total area. This paper examines whether this preference is warranted in a metapopulation framework with circular reserves (patches) by formulating the dependence of metapopulation persistence on the size and number of reserves, both of which depend on reserve radius if the total area is kept constant. Two measures of metapopulation persistence are used: R(0), the number of patches colonized by an occupied patch during its lifetime as an occupied patch, and T(e), the expected time to extinction. These two measures are functions of the extinction and colonization rates of the metapopulation. Several mechanisms for the extinction and colonization processes are formulated from which the dependence of these rates on reserve radius is calculated. It turns out that T(e)generally increases with reserve radius for all mechanisms, which supports the preference of few large reserves. However, R(0)supports this preference only in the case of some special, rather unrealistic, mechanisms. In many other, more realistic, cases an intermediate reserve size exists for which metapopulation persistence measured by R(0)is optimal.

Animals↗
PubMed2004

Marine reserves: long-term protection is required for full recovery of predatory fish populations.

No-take marine reserves are advocated widely as a potential solution to the loss of marine biodiversity and ecosystem structure, and to over-fishing. We assess the duration of protection required for unfished populations of large predatory reef fish to attain natural states. We have monitored two marine reserves at Sumilon and Apo Islands, Philippines, regularly for 17 years (1983-2000). The biomass of large predatory fish was still increasing exponentially after 9 and 18 years of protection at Sumilon and Apo reserves, respectively. There was little evidence that the rate of accumulation of biomass inside the reserves was slowing down even after so many years of protection. This suggests that the length of time to full recovery will be considerable. We made two assumptions in order to estimate this period. Firstly, that biomass growth will follow the logistic model. Secondly, the conservative assumption that biomass had already attained 90% of the local carrying capacity of the environments in the reserves. We conclude that the time required for full recovery will be 15 and 40 years at Sumilon and Apo reserves, respectively. Such durations of recovery appear consistent with known life history characteristics of these fish, and with empirical data on recovery rates of heavily exploited fish stocks. By the time the full fisheries or ecosystem benefits from such reserves are apparent, human populations and impacts will have doubled in much of the developing world. Thus, networks of such reserves need to be implemented immediately. Furthermore, the management mechanisms for the reserves need to be successful over timescales of human generations.

Animals↗