Seismic reflection images of the Moho underlying melt sills at the East Pacific Rise.

The determination of melt distribution in the crust and the nature of the crust-mantle boundary (the 'Moho') is fundamental to the understanding of crustal accretion processes at oceanic spreading centres. Upper-crustal magma chambers have been imaged beneath fast- and intermediate-spreading centres but it has been difficult to image structures beneath these magma sills. Using three-dimensional seismic reflection images, here we report the presence of Moho reflections beneath a crustal magma chamber at the 9 degrees 03' N overlapping spreading centre, East Pacific Rise. Our observations highlight the formation of the Moho at zero-aged crust. Over a distance of less than 7 km along the ridge crest, a rapid increase in two-way travel time of seismic waves between the magma chamber and Moho reflections is observed, which we suggest is due to a melt anomaly in the lower crust. The amplitude versus offset variation of reflections from the magma chamber shows a coincident region of higher melt fraction overlying this anomalous region, supporting the conclusion of additional melt at depth.

Seismic structure of the southern East pacific rise.

Seismic data from the ultrafast-spreading (150 to 162 millimeters per year) southern East Pacific Rise show that the rise axis is underlain by a thin (less than 200 meters thick) extrusive volcanic layer (seismic layer 2A) that thickens rapidly off axis. Also beneath the rise axis is a narrow (less than 1 kilometer wide) melt sill that is in some places less than 1000 meters below the sea floor. The small dimensions of this molten body indicate that magma chamber size does not depend strongly on spreading rate as predicted by many ridge-crest thermal models. However, the shallow depth of this body is consistent with an inverse correlation between magma chamber depth and spreading rate. These observations indicate that the paradigm of ridge crest magma chambers as small, sill-like, midcrustal bodies is applicable to a wide range of intermediate- and fast-spreading ridges.

Seismic Images of Active Magma Systems Beneath the East Pacific Rise Between 17{degrees}05' and 17{degrees}35'S.

Seismic reflection data from the East Pacific Rise between 17 degrees 05' and 17 degrees 35'S image a magma lens that varies regularly in depth and width as ridge morphology changes, confirming the notion that axial morphology can be used to infer ridge magmatic state. However, at 17 degrees 26'S, where the ridge is locally shallow and broad, the magma lens is markedly shallower and wider than predicted from regional trends. In this area, submersible dives reveal recent volcanic eruptions. These observations indicate that it is where the width and depth of the magma chamber differ from regional trends, indicating an enhanced magmatic budget, that is diagnostic of current magmatism.

Long-term changes in left ventricular hypertrophy after renal transplantation.

BACKGROUND: Concentric and eccentric left ventricular hypertrophy are common progressive disorders in dialysis patients and are associated with cardiac failure and death. Although partial regression of these abnormalities is known to occur during the first post-transplant year, their long-term evolution is unknown. METHODS: A total of 143 of 433 dialysis patients participating in a long-term prospective cohort study received renal transplants. Laboratory parameters were assessed monthly. Echocardiography was performed annually. Left ventricular mass index (LVMI) and cavity volume index were calculated according to standard formulae. Multiple linear regression was used to model change in LVMI as a function of baseline clinical and laboratory variables. RESULTS: LVMI fell from 161 g/m2 at 1 year to 146 g/m2 (P=0.009) g/m2 after 2 years. No further regression was seen in years 3 and 4. Left ventricular volume index showed similar trends, with a decline from year 1 to year 2 (P=0.05) followed by stabilization in years 3 and 4. Older age, long duration of hypertension, need for more than one antihypertensive, high pulse pressure in normal-size hearts, and low pulse pressure in dilated hearts were significantly associated with failure of regression of LVMI between the first and second years (MLR, P<0.000001, r2=0.57). CONCLUSIONS: Regression of left ventricular hypertrophy continues beyond the first year after renal transplantation, reaching a nadir at 2 years and persisting into the third and fourth posttransplant years. Failure to regress was associated with older age, hypertension, high pulse pressure in normal-size hearts and low pulse pressure in dilated hearts.

Impact of renal transplantation on uremic cardiomyopathy.

In chronic uremia, cardiomyopathy manifests itself as systolic dysfunction, concentric left ventricular (LV) hypertrophy, or LV dilatation. To determine the impact of renal transplantation on uremic cardiomyopathy, all dialysis patients participating in a long-term cohort study who received a successful renal transplant were followed with echocardiography. The transplanted group comprised 102 of 433 (24%) endstage renal disease (ESRD) patients. They were significantly younger and, on starting ESRD therapy, had significantly less ischemic heart disease and cardiac failure than the overall ESRD cohort. During followup, ischemic heart disease developed in only 1 patient and none experienced cardiac failure. In the 12% (n = 12) of patients with systolic dysfunction before renal transplant, fractional shortening normalized in all patients, increasing from 21.5 +/- 4.6% to 33.5 +/- 5.6% after transplantation. In the 41% (n = 41) with concentric LV hypertrophy before transplantation, the LV mass index improved from 158 +/- 39 g/m2 to 132 +/- 39 g/m2. LV dilatation was present in 32% (n = 32) of patients before transplantation. After transplantation, LV volume fell from 116 +/- 3.1 ml/m2 to 89 +/- 21 ml/m2, and LV mass index in this group fell from 166 +/- 55 g/m2 to 135 +/- 37 g/m2. It was not possible to associate risk factors characteristic of the uremic state with the improvement in cardiac structure and function, although the fall in LV mass was significantly associated with fall in blood pressure. We conclude that correction of the uremic state by renal transplantation leads to normalization of LV contractility in systolic dysfunction, regression of hypertrophy in concentric LV hypertrophy, and improvement of cavity volume in LV dilatation. The degree of improvement suggests that dialysis patients with uremic cardiomyopathy would benefit from renal transplantation.

Age-related differences in the response to myocardial ischemic stress.

Clinical experience indicates that the risk of reparative cardiac operations is increased in the neonatal period relative to that in older infants and children. Age-related differences in the susceptibility to myocardial ischemic dysfunction were evaluated by comparison of left ventricular function and metabolism in neonatal (mean age = 7 days) and weanling (mean age = 96 days) piglets. Six animals in each group supported on cardiopulmonary bypass were subjected to (1) 120 minutes of hypothermic crystalloid cardioplegic arrest (CP-120) and (2) 15 minutes of normothermic ischemic arrest (NA-15) after a 60 minute interval of reperfusion. Left ventricular systolic and diastolic function was measured after each intervention via endocardially implanted ultrasonic dimension crystals in a septolateral minor-axis position. In both groups, systolic dysfunction was evidenced by an increase in the dimension-axis intercept (p = 0.001), but not the slope of the end-systolic pressure-dimension relation. Left ventricular end-diastolic stiffness, expressed as left ventricular end-diastolic pressure versus Lagrangian strain, increased to a similar degree in both groups (p = 0.001). Adenosine triphosphate levels declined significantly (p = 0.001) in both groups in response to the ischemic interventions with no evident intergroup differences. Lactate levels increased significantly during the course of the experiment (p = 0.04); however, the increases were greater (p = 0.009) at all intervals in the neonatal group. This study demonstrates age-related metabolic differences in response to ischemia consistent with a greater dependence on glycolysis in neonatal myocardia. However, the fact that discriminating age-related differences in left ventricular function were not evident suggests that factors other than young age per se account for the increased surgical mortality in the neonatal period.

Need for coronary artery bypass grafting in Newfoundland and Labrador: the impact of increased demand.

BACKGROUND: In the past decade, growth of coronary revascularization in Canada has been substantial. It was hypothesized that as coronary angiography (CA) rates increased, referral for necessary coronary artery bypass grafting (CABG) would also increase, and include patients with multivessel disease and class I to III angina who required elective surgery. Furthermore, it was proposed that the number of CABG surgeries needed would increase at a similar rate to that of CA. METHODS: An incident cohort of patients who received CA in 1998/1999 was identified, and the group referred for CABG was followed. Clinical characteristics, appropriateness and necessity scores using specific criteria, and waiting times were evaluated and compared with a similar cohort from 1994/1995. Utilization data for coronary revascularization procedures from 1994 to 2002 were reviewed. RESULTS: Between 1994/1995 and 1998/1999, the number of CAs per year increased by 37%. The inappropriateness rate for CA was 4% in 1998/1999. The proportion of patients diagnosed with critical coronary artery disease increased from 68% in 1994/1995 to 74% in 1998/1999. The number referred for CABG increased by 48%, and the number for percutaneous transluminal coronary angioplasty (PTCA) increased by 137%. The increase in the number referred for CABG was attributable to the increase in the number of patients with less severe symptoms who required delayed elective CABG. The necessity rate for CABG in the referred group was 94% in 1994/1995 and 95% in 1998/1999. A further 91 patients were identified who needed CABG but did not receive it, 86% of whom had PTCA. From 1999 to 2002, the annual growth rate in those referred for CABG was higher than the growth rate for CA. CONCLUSIONS: With the growth in CA, the rate of discovery of high risk coronary anatomy actually increased. Growth in CABG volume was attributable to growth in the need for elective surgery in patients with class I to III angina. The rate of CABG increased disproportionately to the rate of CA, despite higher rates of PTCA with stenting. It is likely that the demand for CABG will continue to rise steadily, as expansion of angiography occurs, and may be higher than expected from the growth in CA.

Phagocytosis and related phenomena in polymorphonuclear leukocytes from cow's milk.

There were fewer efficient phagocytes among leukocytes collected from artificially irritated mammary glands than among the leukocytes from blood of the same animals. The milk polymorphonuclear (PMN) leukocytes adhered poorly to a column of siliconised glass beads when compared with the blood cells. However, investigations of the O(2) uptake and CO(2) production of the milk PMN leukocytes revealed that these cells appeared to utilize metabolic pathways similar to those used by human and guinea pig PMN leukocytes during phagocytosis. These pathways are associated with degranulation and the production of H(2)O(2) following particle ingestion. It is therefore suggested that the milk PMN leukocytes appear not to have lost the ability to produce this bactericidal substance.

Risk factors for the development of left ventricular hypertrophy in a prospectively followed cohort of dialysis patients.

The objective of this study was to determine the role of hypertension, age, anemia, and hyperparathyroidism in the pathogenesis of left ventricular hypertrophy (LVH) developing after the initiation of dialysis for ESRD. A cohort of dialysis patients who were being treated for ESRD and whose initial echocardiograms after the start of dialysis therapy do not show LVH were studied. Three hundred and thirty-nine patients have been monitored at three centers since 1985. Serial echocardiograms have been performed with M-mode and two-dimensional echocardiography. Data on blood pressure, height, weight, hemoglobin, number and type of antihypertensive medications, and the presence of functioning vascular access have been collected prospectively. Prospective data on serum calcium, serum phosphorus, alkaline phosphatase, and parathyroid hormone levels and skeletal x-rays have also been collected. By the use of set criteria and blinding to echocardiographic outcome, the presence and severity of hyperparathyroidism were graded by consensus. Fifty-one patients met eligibility criteria for inclusion; of these, 14 developed LVH (cases) and 37 did not (controls). Cases had significantly higher systolic blood pressure (P = 0.009) and were older (P = 0.01) than controls. Systolic blood pressure correlated significantly with final posterior left ventricular wall thickness (r = 0.39; P < 0.01). By the use of multivariate analysis, age and systolic blood pressure were significantly and independently associated with increased left ventricular mass index. The frequency of hyperparathyroidism was low and equal in both groups. There was a trend toward more severe anemia in cases that did not reach statistical significance.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac function and hematocrit level.

Patients on dialysis have an age-adjusted death rate 3.5 times that of the general population. The most common cause of death in patients on dialysis is cardiovascular disease. We prospectively followed a cohort of 433 patients in three centers for a mean of 41 months. Mean hemoglobin level at the beginning of dialysis was 8.39 (+/- 1.7) g/dL, and the mean hemoglobin level during follow-up was 8.84 (+/- 1.5) g/dL. Using Cox's regression model, we found that anemia predicted mortality independently of age, diabetes mellitus, cardiac failure, hypoalbuminemia, serum creatinine, mean arterial pressure, or echocardiographic heart disease. The independent relative risk (RR) of mortality was 1.18 per 1.0 g/dL decrease in hemoglobin level. Anemia also independently predicted the de novo occurrence of congestive heart failure when the same covariates were controlled for (RR, 1.49 per 1.0 g/dL decrease). Anemia was also independently predictive of heart failure at the start of dialysis (RR, 1.14 per 1.0 g/dL decrease) and heart failure recurrence (RR, 1.25 per 1.0 g/dL decrease). Left ventricular hypertrophy is present in 75% of patients on dialysis at the start of therapy for end-stage renal disease. It independently predicts mortality. Our prospective cohort study identified increasing age, hypertension, and anemia as risk factors for its development. One controlled study and several uncontrolled studies demonstrated improvement (but not complete regression) of elevated left ventricular mass in patients on dialysis treated with recombinant human erythropoietin (epoetin).

Perfusion of malignant hyperthermia susceptible and normal isolated pig livers with halothane.

We have perfused malignant hyperthermia susceptible and normal isolated pig livers with halothane for one hour. The liver temperatures, oxygen and carbon dioxide tensions, the base deficits and lactate concentrations in blood entering and leaving the liver have been measured at the beginning and at the end of the perfusion. Statistical analysis has shown that there are no significant differences in these parameters between the beginning and the end of the perfusion period or between the normal and the malignant hyperthermia susceptible livers. We conclude, therefore, that the livers of malignant hyperthermia susceptible pigs are either normal or else, if abnormal, the abnormalities are sufficiently benign as to be not measurably expressed.

Effective management of spinal pain in one hundred seventy-seven patients evaluated for manipulation under anesthesia.

OBJECTIVE: To demonstrate that manipulation under anesthesia (MUA), a conservative treatment modality, is both safe and efficacious in the treatment of both acute and chronic spinal pain disorders in appropriately selected patients. MUA can be safely used to treat pain arising from the cranial, cervical, thoracic, and lumbar spine, as well as the sacroiliac and pelvic region. SETTING: An ambulatory surgical center. SUBJECTS: The treatment group consisted of 177 patients between ages 17 and 65 years. Evaluation followed a treatment algorithm created by the authors as a multidisciplinary approach to patient selection, evaluation, treatment, and timing of specialized referral, in consideration of previously published algorithms. Prior forms of treatment, both conservative and surgical in nature, had failed in these patients. INTERVENTION: Patients underwent three sequential manipulations under intravenous sedation, followed by 4 to 6 weeks of skilled spinal manipulation and therapeutic modalities. OUTCOME MEASURES: Data regarding changes in Visual Analog Scale (VAS), range of motion, medication needs, and return to work status were used to document progress. All patients had follow-up for 6 months. RESULTS: On average, VAS ratings improved by 62.2% in those patients with cervical pain problems. On average, VAS ratings improved by 60.1% in those patients with lumbar pain problems. There was a near-complete reversal in patients out of work before MUA (68.6%) and those returning to unrestricted activities at 6 months after MUA (64.1%). There was a 58.4% reduction in the percentage of patients requiring prescription pain medication from the pre-MUA period to 6 months after MUA. Additionally, 24.0% of the treatment group required no medication at 6 months after MUA. CONCLUSION: A multidisciplinary approach to evaluation and treatment, including MUA, offers patient benefits above and beyond what can be obtained through the individual providers working alone.

Hypoalbuminemia, cardiac morbidity, and mortality in end-stage renal disease.

A cohort of 432 ESRD (261 hemodialysis and 171 peritoneal dialysis) patients was followed up prospectively for an average of 41 months. Baseline and annual demographic, clinical, and echocardiographic assessments were performed, as well as serial clinical and laboratory tests measured monthly while patients were on dialysis therapy. Among hemodialysis patients, after adjustment was made for age, diabetes, and ischemic heart disease, as well as hemoglobin and blood pressure levels measured serially, a 10-g/L fall in mean serum albumin level was independently associated with the the development of de novo (relative risk [RR], 2.22; P = 0.001) and recurrent cardiac failure (RR, 3.84; P = 0.003), de novo (RR, 5.29; P = 0.001) and recurrent ischemic heart disease (RR, 4.24; P = 0.005), cardiac mortality (RR, 5.60; P = 0.001), and overall mortality (RR, 4.33; P < 0.001). Among peritoneal dialysis patients, a 10-g/L fall in mean serum albumin level was independently associated with the progression of left ventricular dilation as seen on follow-up echocardiography (beta, 13.4 mL/m2; P = 0.014), the development of de novo cardiac failure (RR, 4.16; P = 0.003), and overall mortality (RR, 2.06; P < 0.001). Hypoalbuminemia, a major adverse prognostic factor in dialysis patients, is strongly associated with cardiac disease.

Impact of hypertension on cardiomyopathy, morbidity and mortality in end-stage renal disease.

A cohort of 432 ESRD (261 hemodialysis and 171 peritoneal dialysis) patients was followed prospectively for an average of 41 months. Baseline and annual demographic, clinical and echocardiographic assessments were performed, as well as serial clinical and laboratory tests measured monthly while on dialysis therapy. The average mean arterial blood pressure level during dialysis therapy was 101 +/- 11 mm Hg. After adjusting for age, diabetes and ischemic heart disease, as well as hemoglobin and serum albumin levels measured serially, each 10 mm Hg rise in mean arterial blood pressure was independently associated with: the presence of concentric LV hypertrophy (OR 1.48, P = 0.02), the change in LV mass index (beta = 5.4 g/m2, P = 0.027) and cavity volume (beta = 4.3 ml/m2, P = 0.048) on follow-up echocardiography, the development of de novo cardiac failure (RR 1.44, P = 0.007), and the development of de novo ischemic heart disease (RR 1.39, P = 0.05). The association with LV dilation was of borderline statistical significance (OR 1.48, P = 0.06). Mean arterial blood pressures greater than 106 mm Hg were associated with both echocardiographic and clinical endpoints. Paradoxically, low mean arterial blood pressure (RR 1.36 per 10 mm Hg fall, P = 0.009) was independently associated with mortality. The association of low blood pressure with mortality was a marker for having had cardiac failure prior to death. We conclude that even moderate hypertension worsens the echocardiographic and clinical outcome in ESRD patients, especially in those without previous clinical cardiac disease.

Outcome and risk factors of ischemic heart disease in chronic uremia.

To determine the prognosis and risk factors for ischemic heart disease in chronic uremia, a cohort of 432 dialysis patients were followed prospectively from start of dialysis therapy until death or renal transplantation. Baseline demographic, clinical and echocardiographic data were obtained. After the initiation of dialysis laboratory data were collected at monthly intervals, and clinical and echocardiographic data at yearly intervals. Twenty-two percent of patients (N = 95) had either a history of angina pectoris or myocardial infarction on starting dialysis therapy. Median time to onset of heart failure was 24 months in those with ischemic heart disease on initiation of dialysis, compared to 55 months in those without (P < 0.0001). This effect was independent of age, diabetes and underlying cardiomyopathy. Median survival was 44 months in those with ischemic disease compared to 56 months in those without (P = 0.0001). This adverse impact was independent of age and diabetes mellitus but, when cardiac failure was added to the Cox's model, ischemic heart disease was no longer an independent predictor of survival. De novo ischemic heart disease, not evident on starting dialysis therapy, occurred in 41 (9%) patients. When compared to patients who never developed ischemic disease (N = 296; 69%), significant and independent predictors of de novo disease were older age (P = 0.0007), diabetes mellitus (P = 0.0001), high blood pressure during follow up on dialysis (P = 0.02) and hypoalbuminemia (P = 0.03), whereas anemia was not an independent predictor. LV mass index was 174 +/- 7 g/m2 in those who developed de novo ischemic disease compared to 155 +/- 3 g/m2 (P < 0.001) in those who did not. Concentric LV hypertrophy, LV dilation and systolic dysfunction were independent risk factors for de novo ischemic heart disease. We conclude that ischemic heart disease occurs frequently in dialysis patients, that its adverse impact is mediated through the development of heart failure, and that the most important, potentially reversible risk factors are hypertension, hypoalbuminemia, and underlying cardiomyopathy.

The impact of anemia on cardiomyopathy, morbidity, and and mortality in end-stage renal disease.

To determine the possible association between anemia and clinical and echocardiographic cardiac disease, a cohort of 432 end-stage renal disease patients (261 on hemodialysis and 171 on peritoneal dialysis) who started dialysis therapy between 1982 and 1991 were followed prospectively for an average of 41 months. Baseline demographic, clinical, and echocardiographic assessments were performed, as well as monthly serial clinical and laboratory tests while the patients were on dialysis therapy. The mean (+/-SD) hemoglobin level during dialysis therapy was 8.8 +/- 1.5 g/dL. After adjusting for age, diabetes, and ischemic heart disease, as well as for blood pressure and serum albumin levels measured serially, each 1 g/dL decrease in mean hemoglobin was independently associated with the presence of left ventricular dilatation on repeat echocardiogram (odds ratio, 1.46; P = 0.018) and the development of de novo (relative risk [RR] = 1.28; P = 0.018) and recurrent (RR = 1.20; P = 0.046) cardiac failure. In addition, each 1 g/dL decrease in the mean hemoglobin level was independently associated with mortality while the patients were on dialysis therapy (RR = 1.14; P = 0.024). Anemia had no independent association with the development of ischemic heart disease while the patients were on dialysis therapy. Anemia, an easily reversible feature of end-stage renal disease, is an independent risk factor for clinical and echocardiographic cardiac disease, as well as mortality in end-stage renal disease patients.

The prognostic importance of left ventricular geometry in uremic cardiomyopathy.

The objective of this study was to determine the effect of left ventricular (LV) mass, volume, and mass-to-volume ratio on mortality in chronic dialysis patients. The Design was a multicenter, prospective inception cohort study with a median follow-up of 41 months. The Setting was three university-affiliated nephrology units. A total of 433 patients who (1) survived > 6 months from the start of ESRD therapy and (2) had a technically satisfactory baseline echocardiogram were studied. Measurements included a baseline clinical, laboratory and echocardiographic assessment. LV hypertrophy was present in 74% and LV dilation was present in 36% of patients. In patients with normal cavity volume (< or = 90 mL/m2) and normal systolic function, high LV mass index (> 120 g/m2) and mass-to-volume ratios (> 2.2 g/mL) were independently associated with late mortality (> 2 yr after starting dialysis therapy). After adjusting for baseline age, diabetes, and ischemic heart disease, the relative risk for the former was 3.29 and for the latter was 2.24. Cavity volume was of no prognostic significance in this group. In patients with LV dilation and normal systolic function, high cavity volume (> 120 mL/m2) and low mass-to-volume ratio (< 1.8 mL/m2) were independently associated with late mortality, the relative risk in the former being 17.14 and the latter being 4.27. LV mass index was of no prognostic significance in this group. The baseline echocardiographic classification, based on LV mass and cavity volume, was the strongest predictor of late mortality, after adjusting for age, gender, diabetes mellitus, coronary artery disease, angina pectoris, chronic hypertension, and hemoglobin and serum albumin levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Outcome and risk factors for left ventricular disorders in chronic uraemia.

BACKGROUND: Left ventricular disease occurs frequently in dialysis patients. It may be manifest as concentric LV hypertrophy, LV dilatation with or without LV hypertrophy, or systolic dysfunction. Little is known concerning the clinical outcome and risk factors for these disorders. METHODS: A cohort of 432 end-stage renal disease patients who survived at least 6 months had an echocardiogram on initiation of dialysis therapy. Clinical, laboratory and echocardiographic data was obtained annually during follow-up. RESULTS: On initiation of ESRD therapy 16% of patients had systolic dysfunction, 41% concentric LV hypertrophy, 28% LV dilatation, and only 16% had normal echocardiograms. Median time to development of heart failure was 19 months in patients with systolic dysfunction, 38 months in concentric LV hypertrophy and 38 months in LV dilatation. The relative risks of heart failure in the three groups were significantly worse than in the normal group, after adjusting for age, diabetes and ischaemic heart disease. Median survival was 38 months in systolic dysfunction, 48 months in concentric hypertrophy, 56 months in LV dilatation, and >66 months in the normal group. Two hundred and seventy-five patients had a follow-up echocardiogram 17 months after starting dialysis therapy together with serial measurement of potential risk factors prior to the echocardiogram. On follow-up echocardiogram the degree of concentric LV hypertrophy was independently related to hypertension while on dialysis, older age, and anaemia while on dialysis; the degree of LV dilatation was related to ischaemic heart disease, anaemia, hypertension and hypoalbuminemia while on dialysis; the degree of systolic dysfunction was associated with ischaemic heart disease and anaemia during follow-up. CONCLUSIONS: Manifestations of left ventricular disease are frequent and persistent in chronic uraemia, and are associated with high risks of heart failure and death. Potentially reversible risk factors include anaemia, hypertension, hypoalbuminaemia and ischaemic heart disease.