Efficacy, safety and tolerability of anagrelide in the treatment of essential thrombocythaemia

BACKGROUND

Essential thrombocythaemia (ET) has an associated risk of thrombotic and haemorrhagic complications, which can be minimised by control of the platelet count. Anagrelide selectively lowers the platelet count, however, there is little Australasian experience with its use and scant data on symptom control.

AIMS

To evaluate the efficacy of anagrelide for platelet reduction and symptom control in a broad cohort of patients with well-defined ET, and to determine the safety and tolerability in such a population.

METHODS

Seventeen patients with ET and a platelet count > 600 x 10(9)/L were prospectively enrolled. The evaluable four males and 12 females with a median age of 58 years (range 14-79) included ten patients (63%) previously treated with two or more agents and 12 patients (75%) who had failed other therapies. The median follow-up was seven months (range 15 days to 36 months).

RESULTS

Anagrelide, in an average dose of 1.9 mg/day, reduced the platelet count from a mean of 728 x 10(9)/L (95% CI 611-845 x 10(9)/L) to 412 x 10(9)/L (95% CI 319-504 x 10(9)/L) (p < 0.001) and maintained it at this level. Fourteen patients (88%) had a platelet reduction to < 600 x 10(9)/L. All symptomatic patients had improvement in symptoms attributable to thrombocythaemia. There were three haemorrhagic and three thrombotic episodes in a total of three patients (19%), including one death from an intracerebral haemorrhage. Six patients (37%) were removed from therapy due to toxicity after a median of 151 days. Side effects included palpitations, abdominal pain and cough.

CONCLUSIONS

Anagrelide is efficacious and safe in ET, both for platelet and symptom control. Minor side effects are common, however, tend to occur early and resolve spontaneously in most cases.

A hyperstable collagen mimic

BACKGROUND

Collagen is the most abundant protein in animals. Each polypeptide chain of collagen is composed of repeats of the sequence: Gly-X-Y, where X and Y are often L-proline (Pro) and 4(R)-hydroxy-L-proline (Hyp) residues, respectively. These chains are wound into tight triple helices of great stability. The hydroxyl group of Hyp residues contributes much to this conformational stability. The existing paradigm is that this stability arises from interstrand hydrogen bonds mediated by bridging water molecules. This model was tested using chemical synthesis to replace Hyp residues with 4(R)-fluoro-L-proline (Flp) residues. The fluorine atom in Flp residues does not form hydrogen bonds but does elicit strong inductive effects.

RESULTS

Replacing the Hyp residues in collagen with Flp residues greatly increases triple-helical stability. The free energy contributed by the fluorine atom in Flp residues is twice that of the hydroxyl group in Hyp residues. The stability of the Flp-containing triple helix far exceeds that of any untemplated collagen mimic of similar size.

CONCLUSIONS

Bridging water molecules contribute little to collagen stability. Rather, collagen stability relies on previously unappreciated inductive effects. Collagen mimics containing fluorine or other appropriate electron-withdrawing substituents could be the basis of new biomaterials for restorative therapies.

The platelet in cardiopulmonary bypass

Platelets are the smallest of the blood cells and are known to be activated during cardiopulmonary bypass. They play a role in many associated complications. Both quantitative and qualitative platelet defects have been demonstrated, resulting in microvascular hemorrhage and thromboembolism. As their interactions with endothelium and other blood cells are unraveled, the important contribution they make toward the systemic inflammatory response to operation seen in cardiopulmonary bypass is increasingly evident. In this review, we consider platelet activation during cardiopulmonary bypass, the resultant clinical effects, and potential approaches to therapy and prevention.

Effects of cardiopulmonary bypass on leukocyte and endothelial adhesion molecules

During the inflammatory response, triggered by cardiopulmonary bypass, interaction between activated leukocytes, platelets, and endothelial cells is mediated through the expression of three main groups of adhesion molecules: the selectins, the integrins, and the immunoglobulin superfamily. The selectins, which mediate the initial rolling of the leukocyte on the endothelium, are divided in three subgroups: L-selectin is expressed on all three leukocyte types, P-selectin is expressed on platelets and endothelial cells, and E-selectin is only expressed on endothelial cells. Integrins can be found on most cell types, consist of an alpha and a beta subunit and mediate firm adhesion of the leukocyte and migration into the tissues. They are classified into subgroups according to the type of their beta subunit. Immunoglobulins such as ICAM-1 and VCAM-1 are expressed mainly on endothelium and act as ligands for certain integrins. This review article summarizes the existing, and rapidly expanding, literature concerning the effects of cardiopulmonary bypass on the expression of leukocyte and endothelial adhesion molecules. Deeper understanding of the, behavior and the role of adhesion molecules during cardiopulmonary bypass may facilitate effective intervention in the inflammatory response process and suppression of its adverse effects.

Tricuspid valve replacement: UK Heart Valve Registry mid-term results comparing mechanical and biological prostheses

BACKGROUND

Little is known of time-related outcome and comparative performance of biological and mechanical prostheses following tricuspid valve replacement (TVR).

METHODS

A retrospective UK Heart Valve Registry study (Jan 1, 1986 to June 30, 1997) identified 425 patients who underwent TVR. Two-hundred twenty-five (52.9%) received biological and 200 (47.1%) received mechanical valves. One-hundred sixty (38%), 158, and 76 had isolated, double, and triple valve replacements, respectively. The follow-up was 96% complete with a total of 1,585 patient-years.

RESULTS

Thirty-day mortality for TVR was 17.3% (73 deaths). One-, 5-, and 10-year survival rates were 72.2%, 59.9%, and 42.9%, respectively. Year of operation (p = 0.04), age (p = 0.04), and number of valves implanted (p = 0.0 3) predicted overall mortality. Age (p<0.001) and year of operation (p = 0.002) predicted overall survival. Thirty-day mortality for biological and mechanical prostheses was 18.8% and 15.6%, respectively. One-, 5-, and 10-year survival rates were 70.5%, 61.5%, and 47.7% for biological and 74.0%, 57.9%, and 33.9% for mechanical prostheses, respectively. Freedom from reoperation at 1 and 10 years was 98.7% and 97.4%. Freedom from death or reoperation was 71.2% at 1 year and 41.9% at 10 years. None of the above outcomes was significantly different between the type of valve prostheses.

CONCLUSIONS

TVR carries a high 30-day mortality and a poor longer term survival. No superiority could be identified for biological or mechanical prostheses in the tricuspid position for either survival or reoperation.

Central nervous system effects of cardiopulmonary bypass

BACKGROUND

The spectrum of approaches to the issue of brain injury in cardiac surgical practice ranges from refusal to acknowledge that the problem exists to an overemphasis on cerebral risks that can unduly frighten patients. An appropriate approach to therapeutic and preventive strategies requires a fitting sense of proportion and an understanding of the mechanisms of cerebral injury.

METHODS

This article reviews the incidence and severity of cerebral injury during cardiopulmonary bypass, the identification of high-risk patients, and the mechanisms of injury, including hypoperfusion, microemboli, and inflammatory response. It discusses the influences of alpha-stat and pH-stat strategies on cerebral blood flow during cardiopulmonary bypass; the use of retinal angiography to image the retinal circulation, thus providing a window on the cerebral microcirculation during bypass; magnetic resonance imaging evidence of an inflammatory response in the brain during bypass; and current efforts to gain better understanding of the molecular mechanisms involved in the inflammatory response.

RESULTS

The current incidence of stroke during cardiopulmonary bypass is somewhat lower than in the 1980s but still remains a significant problem. Levels of cognitive impairment also are unacceptably high. Recognized predictors enable us to identify patients at particularly high risk of stroke. Hypertensive patients are particularly susceptible to ischemic injury during bypass and should be perfused at mean perfusion pressures higher than those for normotensive patients. Under conditions of hypothermia, a pH-stat strategy causes loss of cerebral blood flow autoregulation, and the cerebral blood flow becomes pressure-passive. With both the pH-stat and alpha-stat strategies, cooling of the patient greatly increases the flow to metabolism ratio of the cerebral blood flow; however, this luxury perfusion brings to the brain not just an excess supply of oxygen but also an increased quantity of microemboli. Current investigative efforts are focused on the endothelial cell-leukocyte adhesion cascade, attempting to characterize beta2 and beta1 adhesion molecule expression in patients undergoing cardiac surgery. Hammersmith Hospital is about to complete a study of the effects of high-dose aprotinin on the inflammatory response pattern and on cerebral infarction.

CONCLUSIONS

Further progress in the development of therapeutic and preventive strategies with respect to cerebral injury during cardiac bypass depends on an increase in the understanding of the mechanisms involved. Current strategies should include optimizing cerebral perfusion and minimizing macroembolic and microembolic damage. The possibility of modifying the systemic inflammatory response is the most interesting challenge of the next few years.

Quality-of-life information and clinical practice: the oncologist's perspective

OBJECTIVE

To collect information from a group of Canadian oncologists about their perspectives on quality of life (QOL) and QOL information.

DESIGN

A self-administered questionnaire (MD-QOL) containing 75 items with a 4-point Likert categorical response scale was administered by mail using Dillman survey methodology to all staff oncologists at a single institution.

SETTING

A large Canadian cancer care centre (Princess Margaret Hospital, Toronto).

MAIN OUTCOME MEASURES

Oncologists' knowledge, attitude, current behaviour and intended willingness to use QOL information.

RESULTS

Of 67 eligible respondents 54 replied (80% response rate). In all, 74% felt that QOL can be quantified, and 95% felt that it gives information distinct from performance status measures. A total of 87% felt that published QOL data are useful for individual patient care, but 69% indicated that, at present, they would be more likely to base their recommendations on personal experience rather than on published literature. Of the respondents, 57% felt that decisions were made more difficult when QOL issues are considered.

CONCLUSIONS

The surveyed oncologists support the relevance and importance of QOL information. Data from this study were used to develop a predictive model to assess oncologists' willingness to use QOL information; the model is being tested in other studies.

Magnetic resonance spectroscopy of high-energy phosphates and lactate immediately after coronary artery bypass surgery

Hypothermic cardiopulmonary bypass (CPB) is associated with a high incidence of neuropsychological defects, marked cerebral swelling immediately after surgery and jugular bulb desaturation during rewarming. This suggests cerebral ischaemia may occur, but evidence is indirect. We studied four patients with 31P magnetic resonance spectroscopy (MRS) and four with 1H MRS before and immediately after coronary surgery. There was no visible lactate in 1H MR spectra. In 31P MR spectra, the ratio of phosphocreatine to adenosine triphosphate was maintained (before: 2.13 +/- 0.86 vs after: 2.57 +/- 1.31; mean +/- 1 SD) and there was no intracellular acidosis (intracellular pH: 7.1 +/- 0.04 vs 7.16 +/- 0.08), while phosphocreatine/inorganic phosphate was increased immediately after the operation (2.92 +/- 0.37 vs 6.39 +/- 2.67, p = 0.03). This suggests rebound replacement of energy stores following recovery from temporary cerebral ischaemia during CPB: intra-operative studies would be needed to test this hypothesis further.

Localised cerebral phosphorus-31 MR spectroscopy in man before and immediately after coronary bypass surgery with hypothermic cardiopulmonary bypass

Coronary artery bypass surgery classically is undertaken with hypothermic cardiopulmonary bypass (CPB). There is a high incidence of neuropsychological defects after cardiac surgery, which may be related to cerebral ischaemia during the rewarming period. In this study, phosphorus-31 magnetic resonance spectroscopy (31P MRS) was used to identify changes in cerebral 31P MR spectra in patients before and immediately after hypothermic CPB. Four neurologically normal patients undergoing coronary artery bypass surgery were studied. Localised cerebral 31P MRS (TR 5000 ms) was performed at 1.5 Tesla on each patient the day before and within an hour of completion of surgery. Peak areas for phosphomonoesters (PME), inorganic phosphate (Pi), phosphodiesters (PDE), phosphocreatine (PCr) and beta ATP (betaATP) were measured. Metabolite peak area ratios and relative percentages of each 31P MR resonance with respect to the total 31P MR signal were calculated. In the post-operative MR spectra, each patient displayed a marked reduction in Pi/betaATP and increase in PCr/Pi ratios. Spectral changes in percentage metabolite signals following surgery varied both in magnitude and pattern between patients. In two patients there was an increased postoperative percentage PME and percentage PCr with a decrease in percentage betaATP. The converse was found in the other two patients, but all four subjects displayed a markedly decreased percentage Pi after CPB. These metabolite changes probably reflect rebound phosphorylation in the immediate postoperative period and suggest increased metabolic activity in the hyperaemic brain on rewarming from hypothermic CPB.

Thirty-day mortality and long-term survival following surgery for prosthetic endocarditis: a study from the UK heart valve registry

OBJECTIVE

To assess the 30-day mortality, long-term survival and freedom from reoperation following surgery for prosthetic endocarditis (PVE).

METHOD

A retrospective analysis of data from the UK Heart Valve Registry of 322 patients who had undergone single mechanical/bioprosthetic valve replacement for PVE between 1 January 1986 and 31 December 1996. The mean age was 54.9 +/- 12.8 years and 213 (66.1%) were males. There were 170 aortic and 152 mitral valve implantations. Eighty-five (26%) of the infected valves were bioprosthetic and 237 (74%) were mechanical. Of the new prostheses implanted 53 (17%) were bioprosthetic and 269 (83%) were mechanical. Of those with infected bioprostheses, 50 (15.2%) had mechanical valves at redo surgery, whilst 219 (68.3%) of infected mechanical prostheses were re-replaced by mechanical prostheses. The follow-up was 98% complete with a total of 1084.9 patient years.

RESULTS

The 30-day mortality was 63 (19.9%; 95%CI 15.9-24.7%). There were 85 late deaths. One, 5 and 10 year survival rates were 67.1% (61.6-72.0%), 55.0% (49.0-60.7%) and 37.6% (27.9-47.2%), respectively. Age was the only significant determinant of 30-day mortality (P = 0.04). Age (P = 0.001) and explanting of infected bioprosthesis and replacement by mechanical valve (P = 0.04) determined long-term survival (P = 0.001). The incidence of re-reoperation was 9.9%. Freedom from reoperation for PVE was 88.4, 87.3 and 87.3% at 1, 5 and 10 years, respectively. Explanting of bioprosthesis and replacement by mechanical valve (P < 0.001) and reoperation within 60 days of native valve replacement (P = 0.02) were determinants of reoperation for PVE. Freedom from death or reoperation was 61.1, 50.6 and 34.2% at 1, 5 and 10 years, respectively. Age (P = 0.003), explanting of bioprosthesis and replacement by mechanical valve (P = 0.002) and the period between prosthetic re-replacement (P = 0.04) determined freedom from death or reoperation.

CONCLUSION

Operation for PVE carries a high 30-day mortality and reduced long-term survival. There is no evidence that type of prosthesis used for re-reoperation determines survival or freedom from re-reoperation.

Imaging bioluminescent indicators shows Ca2+ and ATP permeability thresholds in live cells attacked by complement

A series of permeability thresholds to Ca2+ metabolites and macromolecules, occurring at different times when cells are attacked by complement, has been established by imaging HeLa cells transiently expressing a recombinant cytosolic fusion protein of firefly luciferase and aequorin (luciferase-aequorin) to measure changes in ATP and cytosolic free Ca2+. Nuclear fluorescence of propidium was used as a measure of permeability to small molecules, and luciferase activity imaged to assess lysis. The rise in cytosolic free Ca2+ observed after C9 attack preceded by at least 60 s both the increase in propidium fluorescence, measured in single cells, and the decrease in ATP monitored by luciferase light emission. These effects were dependent on the concentration of C9. At concentrations of C9 up to 4 micrograms/ml no loss of luciferase-aequorin protein was detected at the end of the experiment. Thus the membrane integrity of the cells remained intact, even though the cells were permeable to propidium. These results confirmed our earlier observations that propidium permeability in cells attacked by complement was not a reliable measure of cell death. They also show that it is vital to take account of cellular heterogeneity if the mechanisms by which cells respond to membrane pore former attack are to be correctly interpreted.

Brain damage during cardiopulmonary bypass

The development of systems that allow cardiopulmonary bypass have been responsible for the growth of our specialty. In recent years continuing reduction in the mortality associated with cardiac operations has reinforced our confidence in the reliability and safety of perfusion equipment. Cardiac surgeons are aware that the mortality for most cardiac surgical procedures has decreased dramatically and overall morbidity has been reduced significantly. However, it is still clear that cardiopulmonary bypass techniques are not perfect. Indeed, it is fair to say that the period of bypass still contributes to significant morbidity in most patients. In particular, cerebral injury, the focus of this review, is a significant problem for patients and their caregivers and for funding of health-care systems. Incidence rates for stroke are around 2% to 3%, with increased risk in elderly patients and other high-risk groups. This relatively low incidence of what is universally recognized as a serious complication may be contrasted with the much higher reported incidence of cognitive defects assessed by neuropsychologic testing. The incidence of cognitive defects is as high as 60% at 8 days postoperative with reduction to 25% to 30% incidence at 8 weeks and 12 months. There are a variety of ways, at least potentially, in which the brain may be injured during an operation with cardiopulmonary bypass, including reduced cerebral blood flow, microembolism and macroembolism, and a systemic inflammatory response. These mechanisms interrelate and produce synergistic, cumulative effects on brain function during and after the operation. Reducing the incidence and effects of this altered brain function will rely on both preventive and therapeutic strategies. These, in turn, must be based on an understanding of the pathophysiology of these mechanisms of cerebral injury and directed toward ways to optimize cerebral perfusion, minimize embolic vascular occlusion, and develop pharmacologic approaches to modify the systemic inflammatory response.

Cerebral swelling after normothermic cardiopulmonary bypass

BACKGROUND

Marked cerebral swelling visible on magnetic resonance images has been found immediately after hypothermic (28 degrees C) cardiopulmonary bypass. The mechanism is unknown, but indices of cerebral ischemia are seen during rewarming from hypothermic bypass that are not present with normothermic bypass (37 degrees C).

METHODS

T1-weighted and fluid-attenuated inversion recovery magnetic resonance images were taken of seven patients undergoing routine coronary artery bypass surgery before, 1 h, and 7 days after the operation using normothermic bypass.

RESULTS

Marked cerebral swelling was seen in fluid-attenuated inversion recovery images in five of seven patients 1 h after bypass. Scans in four patients taken 7 days after bypass showed that the cerebral swelling had returned to normal. There was no change in cerebral ventricular size, and all patients had uncomplicated postoperative courses.

CONCLUSIONS

Normothermic bypass is followed by acute postoperative cerebral swelling. However, the amount of swelling was similar to that found in a previous study after hypothermic bypass. The mechanism of swelling is still obscure, and its relation to neurologic outcome is unknown.

Cerebral functional changes following cardiac surgery: Neuropsychological and EEG assessment

OBJECTIVE

Some form of organic and functional cerebral deficit may occur in up to one third of patients following cardiopulmonary bypass surgery. This study was designed to assess cerebral functional deficit in cardiac surgical patients.

METHODS

Neuropsychological and quantitative electroencephalographic (EEG) changes were assessed in 62 first time coronary artery bypass graft surgery patients before surgery and within 1 week and 2 months after surgery. Patients underwent surgery with a standard Hammersmith Hospital anaesthesia and hypothermic cardiopulmonary bypass (28 degrees C), using either bubble (Harvey 1700, n = 28) or membrane (Cobe CML, n = 34) oxygenators with arterial line filters (Pall 40 microm). Neuropsychological performance was assessed using a well established battery of ten tests. Four EEG relative power frequency bands; delta (1-3.5 Hz), theta (4-7.5 Hz), alpha (8-11.5 Hz), and beta (12-23 Hz), were determined using Fast Fourier Transformation (FFT).

RESULTS

Neuropsychological and EEG deficits were found in 48% of patients 1 week after surgery and in 34% 2 months after surgery. Post-operative deficits were not associated with duration of perfusion, type of oxygenator used in surgery or patient age. Neuropsychological and EEG deficits were associated 2 months after surgery, but not 1 week after surgery. Post-operative EEG deficit was associated with pre-operative deficit.

CONCLUSIONS

Cerebral functional deficit was found following CABG surgery using quantitative EEG and neuropsychological assessments. Patients who had neuropsychological deficit were also more likely to show EEG deficit. EEG deficit before and after surgery suggests vulnerability of patients with already compromised cerebral function to the effects of CPB procedure.

Aortic valve replacement in patients 80 years of age and older: survival and cause of death based on 1100 cases: collective results from the UK Heart Valve Registry

BACKGROUND

Aging of the population and advances in preoperative and postoperative care are reflected in an increasing number of patients > or = 80 years of age undergoing aortic valve replacement (AVR) in the United Kingdom. The present study presents data on postoperative 30-day mortality, actuarial survival, and cause of death based on a large collective patient population.

METHODS AND RESULTS

Data were extracted from the UK Heart Valve Registry. From January 1986 to December 1995, 1100 patients > or = 80 years of age underwent AVR and were reported to the registry. Six hundred eleven patients (55.5%) were women. The mean follow-up time was 38.9 months. The 30-day mortality was 6.6%. Of the 73 early deaths, 42 were due to cardiac reasons. The actuarial survival was 89%, 79.3%, 68.7%, and 45.8% at 1, 3, 5, and 8 years, respectively. After the first 30 postoperative days, 144 of the 205 deaths were due to noncardiac reasons. Malignancy, stroke, and pneumonia were the most common causes of late death. Bioprosthetic valves were implanted in 969 patients (88%) and mechanical valves in 131 (12%) patients. There was no difference in early mortality and actuarial survival between the two groups (P>.05).

CONCLUSIONS

The above results suggest that under the selection criteria for AVR currently applied in the United Kingdom, patients > or = 80 years of age show a satisfactory early postoperative outcome and moderate medium-term survival benefit.