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Biomedical subjects

R C Chiu

Publications and source records attributed to R C Chiu.

At least 19 recordsLinked to original sources
PubMed1995

Optimizing "delay period" for burst stimulation in dynamic cardiomyoplasty.

Hemodynamic evidence of systolic assist after dynamic cardiomyoplasty remains inconsistent. One of the relevant factors may be how the burst stimulator is programmed. In 3 patients who underwent cardiomyoplasty for idiopathic dilated cardiomyopathy, we examined the modes used to determine the delay period between the R-wave sensing and the onset of burst stimulation during cardiac systole. These modes include the fixed time mode, the valve-synchronized mode, and the flow-optimized mode. The rationale for choosing these modes and the benefits conferred by each are discussed.

Aged↗
PubMed1995

Biological perspective on "myocardial preconditioning".

There has been an upsurge of research on myocardial preconditioning because of its potential clinical application in areas such as cardiology, cardiac surgery, and transplantation. From a broad biological standpoint, a conceptual framework may help in both promoting understanding and suggesting future research paths. The living organism's tendency toward developing evolutionarily advantageous strategies has led to a fight or flight response, for which the authors consider preconditioning a component. Added to preconditioning, the production of stress proteins and altered myocardial states (especially that of "hibernating myocardium") can be seen as a series of biological strategies developed and maintained during evolution. An increased understanding of the mechanisms involved in the body's self-defense strategies should lead to better approaches, those in which we can help the cells, including those comprising the myocardium, to preserve themselves.

Adaptation, Physiological↗
PubMed1995

Universal health care and high-tech medicine.

The purpose of this article is to review the Canadian universal health care system, focusing on the benefits and consequences of high-tech medicine. Such knowledge could be valuable in guiding the evolving universal health care system in Taiwan. The Canadian Health Care System was developed under the ideals of universality, accessibility and portability. It has successfully provided health care to all citizens regardless of their financial resources and is supported by the great majority of Canadians. However, in spite of various efforts to control health care costs, the governmental financial burden continues to escalate, seriously affecting the development and availability of high-tech medicine for patients who require such services. Delay in the acquisition of high-tech equipment, scarcity of high-tech resources relative to the population size and long waiting periods for certain services have been experienced in Canada. An aging population and advances in medical technology will force the continued escalation of health care costs in spite of optimization of the health care delivery system, and the most serious impact will be felt in high-tech medicine. A number of possible solutions such as user fees or rationing of health care services in high-tech medicine are so far unacceptable in Canada, both for ideologic and ethical reasons. However, rationing and user fees, which the author considers to be inevitable, can be designed to diminish undesirable effects and address the problem of deteriorating high-tech medical care in a universal health care system. Approaches such as a graded user fee based on income, and technologic rationing based on a cost/utility ratio may have to be explored.(ABSTRACT TRUNCATED AT 250 WORDS)

Canada↗
PubMed1995

Cellular cardiomyoplasty: myocardial regeneration with satellite cell implantation.

BACKGROUND: Damaged skeletal muscle is able to regenerate because of the presence of satellite cells, which are undifferentiated myoblasts. In contrast, destruction of cardiac myocytes is associated with an irreversible loss of myocardium and replacement with scar tissue, because it lacks stem cells. We tested the hypothesis that skeletal muscle satellite cells implanted into injured myocardium can differentiate into cardiac muscle fibers and thus repair damaged heart muscle. METHODS: Two series of canine studies were performed. In the first series (n = 26), satellite cells were isolated from skeletal muscle, cultured, and labeled with tritiated thymidine. The cells were implanted into acutely cryoinjured myocardium and the specimens harvested 4 to 18 weeks later. In the second series (n = 20), satellite cells in culture were labeled with lacZ reporter gene, which encodes production of Escherichia coli beta-galactosidase. Four to 6 weeks later, beta-galactosidase activity was studied using X-Gal stain. RESULTS: New striated muscles were found in the first series of experiments at the site of implantation, within a dense scar created by cryoinjury. These muscles showed histologic evidence of intercalated discs and centrally located nuclei, similar to those seen in cardiac muscle fibers. Tritiated thymidine radioactivity was not identified clearly, presumably due to dilutional effect as the stem cells replicated repeatedly. In the second series, histochemical studies of reporter gene-labeled and implanted satellite cells revealed the presence of beta-galactosidase within the cells at the implant site, which confirmed the survival of implanted cells. CONCLUSIONS: Our data are consistent with the hypothesis of milieu-influenced differentiation of satellite cells into cardiac-like muscle cells. Confirmation of these findings and its functional capabilities could have important clinical implications.

Animals↗
PubMed1995

An integrated approach to the surgical management of heart failure.

Many among the large and increasing number of patients suffering from heart failure can benefit from surgical interventions. The indications, efficacy and limitations of various surgical procedures currently available are reviewed, and an integrated approach to offer surgical therapy optimal for the particular patients is proposed.

Canada↗
PubMed1994

The enigma of myocardial preconditioning models.

Myocardial preconditioning has been reported in the hearts of many species of animals, including dogs, pigs, rabbits, rats, and anecdotally in humans. However, most studies were carried out in the regional ischemic model, although protection against global ischemic injury had been observed in rat models. Besides biochemical endpoints, the criterion of protection in regional ischemia was usually reduction in infarct size, while in global ischemia, recovery of contractile force and time-to-onset of ischemic contracture were used. We attempted to reproduce preconditioning of myocardium against global ischemic injury using an isolated perfused rabbit heart model with the rationale that global ischemia is more relevant to cardiac surgery, the rabbit model is logistically convenient, and it can be used for future comparison with the responses in immature hearts. The preconditioning was induced with 5 minutes of normothermic global ischemia followed by 10 minutes of reperfusion. The principal ischemic injury lasted 35 minutes, followed by 60 minutes of reperfusion. The control group underwent similar principal ischemic injury and reperfusion but no prior preconditioning ischemia. Results showed that there was no difference between the two groups in left ventricular resting tension, recovery in left ventricular developed pressure, contractility (dP/dt), and rate of relaxation (-dP/dt), nor were there any differences in heart rate and coronary flow rate. The reason for our negative findings is not clear, but if the results are confirmed, it will suggest that extrapolation of observations obtained from one experimental model to another should be made with caution.

Animals↗
PubMed1994

Character of shed blood in cardiac and thoracic surgery patients: implications for reinfusion.

OBJECTIVE: To determine whether the independently observed increase in the levels of cardiac enzymes in peripheral blood can be accounted for by elevations from postoperative shed-blood reinfusion in patients who have undergone cardiac or thoracic operations. DESIGN: Prospective, case-controlled study. SETTING: A cardiothoracic surgery unit at a university referral centre. PATIENTS: Thirty-four consecutive patients who underwent cardiac or thoracic surgery within a 3-week period. INTERVENTIONS: Coronary artery revascularization (23 patients), cardiac valve replacement or repair (4) and lung resection (7). MAIN OUTCOME MEASURES: Determination of levels of cardiac enzymes and isoenzymes in samples of peripheral and shed blood. Statistical comparison was by paired t-tests within groups and by unpaired t-tests between groups. RESULTS: Serum levels of creatine kinase, lactic dehydrogenase and aspartate aminotransferase were significantly (p < 0.001) elevated in samples of shed blood compared with peripheral blood in all groups. The elevations were found to be related to skeletal muscle injury and were not of cardiac origin. In the absence of myocardial infarction, cardiac isoenzyme levels were significantly (p < 0.001) elevated in the peripheral blood of cardiac surgery patients compared with that of thoracic surgery patients. CONCLUSION: Reinfusion of shed blood will result in elevated levels of cardiac enzymes in peripheral blood but will not increase the percentage of isoenzymes.

Alanine Transaminase↗
PubMed1994

Double gloving might predispose to injury by blunting temperature perception.

Double gloving may blunt perception of excessively warm instruments. We describe a case where this might have contributed to a cutaneous burn in a patient undergoing laparoscopic cholecystectomy. To test the role of two gloves in blunting temperature perception, we performed two experiments. In the first, 250 ml of water at 70 degrees C were placed in one glove or two gloves, and the rate of change of temperature after submersion in a bath at 18 degrees C was measured. The use of two gloves was associated with a marked decrease in rate of change in temperature (temperature at 5 min 37 +/- 2.3 degrees C [double gloves] versus 24 +/- 2.6 degrees C [single glove]; p < 0.001). In the second experiment, a thermometer covered with no gloves, one glove, or two gloves (group 5; n = 5) was submerged in a water bath at 90 degrees C. After 5 s, the temperature without gloves was 85.2 +/- 2.2 degrees C compared with 61.3 +/- 0.8 degrees C with one glove and 45.6 +/- 1.1 degree C with two gloves (p < 0.001). After 15 s, the temperature without gloves was 90.2 +/- 1.6 degrees C compared with 76.5 +/- 0.5 degrees C with one glove, and 64.4 +/- 0.8 degrees C with two gloves (p < 0.001). We conclude that the use of two gloves significantly decreases heat transmission, thus altering temperature perception.

Aged↗
PubMed1992

Adverse effect of prearrest hypothermia in immature hearts: rate versus duration of cooling.

It has been suggested that rapid cooling before the induction of arrest may be harmful to the newborn myocardium. The objective of this study was twofold: (1) to evaluate whether prearrest rapid cooling is indeed detrimental to myocardial recovery and (2) if so, to evaluate whether the adverse effect of prearrest hypothermia is dependent on the rate of cooling or the total duration of cold perfusion. After an initial stabilization period isolated Langendorff hearts (n = 5 per group) from neonatal piglets (5 to 7 days old) were randomized to four groups: group 1, 5 minutes of rapid cooling to 15 degrees C; group 2, 20 minutes of slow cooling to 15 degrees C; group 3 and group 4, rapid and slow cooling, respectively, with the addition of St. Thomas cardioplegic solution. All groups were then subjected to 2 hours of ischemia at 15 degrees C followed by 30 minutes of reperfusion at 38.5 degrees C. Post-ischemic recovery of left ventricular developed pressure was significantly greater in group 1 versus group 2 (80% +/- 3% versus 61% +/- 2%; p less than 0.05) and in the presence of cardioplegia, group 3 versus group 4 (72% +/- 3% versus 57% +/- 3%; p less than 0.05). The increase in left ventricular end-diastolic pressure was significantly less in group 1 versus group 2 (8% +/- 5% versus 33% +/- 7%; p less than 0.01). Myocardial adenosine triphosphate content recovery correlated with ventricular recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1992

Effects of hypothermia on hemodynamic responses to dopamine and dobutamine.

Hemodynamic characteristics, arrhythmogenicity, and dose-related hemodynamic responses to intravenous dopamine (group I) and dobutamine (group II) were examined in 16 swine at three different core body temperatures (38.5 degrees C, 35 degrees C, and 30 degrees C). The animals were anesthetized with isoflurane and mechanically ventilated. Cooling and re-warming were accomplished by a femoral-jugular A-V shunt. The animals were cooled down to 30 degrees C and stabilized for 1 hour before intravenous infusion of dopamine (group I, n = 8) or dobutamine (group II, n = 8) was started at 2, 5, 10, 15, 20, and 30 micrograms/kg/min. Hemodynamic responses to the two inotropes were continuously monitored with a bedside monitor equipped with a PC mode for customized data collection and analysis. Computerized arrhythmia detection was performed. Our findings were: (1) profound hypothermia (30 degrees C) causes significant depression of hemodynamic functions; (2) IV infusion of dopamine and dobutamine can be used safely and effectively for inotropic support during profound hypothermia, and the optimal dosage for improving cardiac output is 10-20 micrograms/kg/min; (3) no risk of inducing arrhythmia was noted with IV infusion of both inotropes up to a maximum dosage of 30 micrograms/kg/min, even though significant sinus tachycardia was consistently seen at 30 micrograms/kg/min.

Animals↗
PubMed1992

Cell transplantation for myocardial repair: an experimental approach.

Myocardium lacks the ability to regenerate following injury. This is in contrast to skeletal muscle (SKM), in which capacity for tissue repair is attributed to the presence of satellite cells. It was hypothesized that SKM satellite cells multiplied in vitro could be used to repair injured heart muscle. Fourteen dogs underwent explantation of the anterior tibialis muscle. Satellite cells were multiplied in vitro and their nuclei were labeled with tritiated thymidine 24 h prior to implantation. The same dogs were then subjected successfully to a myocardial injury by the application of a cryoprobe. The cells were suspended in serum-free growth medium and autotransplanted within the damaged muscle. Medium without cells was injected into an adjacent site to serve as a control. Endpoints comprised histology using standard stains as well as Masson trichrome (specific for connective tissue), and radioautography. In five dogs, satellite cell isolation, culture, and implantation were technically satisfactory. In three implanted dogs, specimens were taken within 6-8 wk. There were persistence of the implantation channels in the experimental sites when compared to the controls. Macroscopically, muscle tissue completely surrounded by scar tissue could be seen. Masson trichrome staining showed homogeneous scar in the control site, but not in the test site where a patch of muscle fibres containing intercalated discs (characteristic of myocardial tissue) was observed. In two other dogs, specimens were taken at 14 wk postimplantation. Muscle tissue could not be found. These preliminary results could be consistent with the hypothesis that SKM satellite cells can form neo-myocardium within an appropriate environment. Our specimens failed to demonstrate the presence of myocyte nuclei.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗