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Biomedical subjects

J L Cox

Publications and source records attributed to J L Cox.

At least 19 recordsLinked to original sources
PubMed2001

Differences between perspectives of physicians and patients on anticoagulation in patients with atrial fibrillation: observational study.

OBJECTIVE: To determine and compare physicians' and patients' thresholds for how much reduction in risk of stroke is necessary and how much risk of excess bleeding is acceptable with antithrombotic treatment in people with atrial fibrillation. DESIGN: Prospective observational study. SETTING: Tertiary and peripheral referral centres in Nova Scotia, Canada. PARTICIPANTS: 63 physicians who were treating patients with atrial fibrillation and 61 patients at high risk for atrial fibrillation. MAIN OUTCOME MEASURES: Participants underwent a face to face interview with a probability trade-off tool. Thresholds were determined for the minimum reduction in risk of stroke necessary and the maximum increase in risk of excess bleeding acceptable for treatment with aspirin and warfarin in people with atrial fibrillation. RESULTS: The minimum number of strokes that needed to be prevented in 100 patients over two years for warfarin to be justified was significantly lower for patients than for physicians (1.8 (SD 1.9) v 2.5 (1.6), P=0.009), whereas for aspirin there was no difference between patients and physicians (1.3 (1.3) v 1.6 (1.5), P=0.29). The maximum number of excess bleeds acceptable in 100 patients over two years for use of warfarin and aspirin was significantly higher for patients than for physicians (warfarin 17.4 (7.1) v 10.3 (6.1); aspirin 14.7 (8.5) v 6.7 (6.2); P<0.001 for both comparisons). CONCLUSIONS: Patients at high risk for atrial fibrillation placed more value on the avoidance of stroke and less value on the avoidance of bleeding than did physicians who treat patients with atrial fibrillation. The views of the individual patient should be considered when decisions are being made about antithrombotic treatment for people with atrial fibrillation.

Adult↗
PubMed2001

The structure and function of the helical heart and its buttress wrapping. I. The normal macroscopic structure of the heart.

The Gordian knot of anatomy has been the architectural arrangement of ventricular muscle mass, which may have finally become understood. The description of Francisco Torrent-Guasp's model of the helical heart is presented, which includes the cardiac structures that produce 2 simple loops that start at the pulmonary artery and end in the aorta. An unscrolled ventricular band is shown, achieved by blunt dissection that extends between the points of origin of the right ventricle, at the pulmonary artery root, to termination at the aortic root, in the left ventricle. These components include a spiral horizontal basal loop that surrounds the right and left ventricular cavities, and changes direction to cause a second spiral, produced by almost vertically oriented fibers, giving rise to the helical configuration of the ventricular myocardial band. These anatomic structures are successively activated, as with a peristaltic wave, starting at the right ventricle (just below the pulmonary artery) and progressing toward the aorta to produce a sequence of narrowing, caused by the basal loop contraction, shortening (related predominantly to the descendant segment contraction), lengthening (produced by the ascendant segment contraction), and widening, as a consequence of several factors that act during ventricular myocardium relaxation. These sequences control the ventricular events responsible for ejection to empty and suction to fill. These mechanical interactions of structure and function are defined in relation to chronologic location of the successive cardiac functional events in the aortic, left ventricular, and left atrial recordings.

Animals↗
PubMed2001

The structure and function of the helical heart and its buttress wrapping. III. The electric spiral of the heart: The hypothesis of the anisotropic conducting matrix.

The study of the dissemination of the electric impulse throughout the ventricular myocardium, which gave rise to the current theories, was performed without taking into consideration the complex architecture of the cardiac muscle elucidated by more recent researchers. We propose a novel hypothesis based on the special macroscopic structure of the heart, the anisotropic electric and mechanical behavior of the myocardium, the characteristics of the intercellular matrix and its very special collagen scaffolding, chemical composition, and biochemistry. The unique properties of the intercellular matrix would make it especially suited to function, in conjunction with the specialized conducting system (His-Purkinje system), as an efficient anisotropic conductor for the spread of electric activation in the heart, and to allow an optimal sequence of excitation-contraction coupling that results in the coordination of effective myocardial contraction in birds and mammals of the most varied known heart rates.

Animals↗
PubMed2001

The structure and function of the helical heart and its buttress wrapping. IV. Concepts of dynamic function from the normal macroscopic helical structure.

Torrent-Guasp's model of the helical heart is presented, which includes the cardiac muscular structures that produce 2 simple loops and that start at the pulmonary artery and end in the aorta. These components include a horizontal basal loop that surrounds the right and left ventricles, changes direction through a spiral fold in the ventricular band to cause a ventricular helix produced by now obliquely oriented fibers, forming a descending and ascending segment of the apical loop with an apical vortex. These anatomic concepts are successively activated to produce a sequence of narrowing by the basal loop, shortening by the descending segment, lengthening by the ascending segment, and widening in the cardiac cycle that causes ventricular ejection to empty and suction to fill. The factors responsible for internal torsional movements for cardiac output and suction are defined, together with mechanisms responsible for electromechanical activity produced during sequential changes in contraction and relaxation properties. These interactions of mechanical structure and function are defined in relation to pressure-related cardiac events observed from aortic, left ventricular, and left atrial recordings.

Animals↗
PubMed2001

The challenge with tracking health outcomes.

Rising health care costs, questions about the effectiveness of medical interventions and demands for greater accountability and efficiency with respect to health care delivery have led to a growing interest in using patient outcomes as a primary measure of the quality of care. However, measuring outcomes is complex and expensive given the widespread lack of an integrated and comprehensive electronic health information system. Furthermore, the science of outcome measurement is relatively undeveloped and caution needs to be taken when attempting to relate health care provision to differences in outcomes. While the foregoing problems do not invalidate outcome measurement programs, they do stress the point that such initiatives need to be pursued cautiously and that their limitations must be clearly appreciated. The challenge with tracking health outcomes is discussed from the perspective of the Improving Cardiovascular Outcomes in Nova Scotia study. This outcome measurement and management project, one of the most ambitious ever undertaken in Canada, has been seeking to improve the medical care of patients with cardiovascular disease in Nova Scotia since October 1997.

Canada↗
PubMed2000

HRT to prevent cardiovascular disease. What studies show, how to advise patients.

How should you advise postmenopausal patients who are considering estrogen therapy? Do the potential cardiovascular benefits outweigh the risks? Does hormone therapy improve the cardiovascular risk profile in women with established coronary artery disease? In this article, Drs Wood and Cox help clarify the current clinical data for and against hormone replacement therapy for prevention of cardiovascular disease. In addition, they discuss current treatment recommendations and future directions in hormone therapy.

Cardiovascular Diseases↗
PubMed2000

Efficacy estimates from parasite count data that include zero counts.

Because of the positive skewness of parasite distributions and the greater constancy of percentage of response of therapy in animal populations, parasite count data are conventionally transformed logarithmically before combining results from different animals, either all controls or all treated. Observations of zero counts raise difficulties, since the logarithm of zero is not useful. In this study, several types of zero count adjustments are compared. Two systems for assigning values to zero counts were considered: a fixed system, which assigns the same value to all zero counts regardless of the proportion of such counts in a treatment group, and a variable system, which replaces zero counts with a value based on the proportion of zero counts in the group. The values assigned by either system are then adjusted to reflect aliquot size. An evaluation was performed by using 32 compound Poisson lognormal distributions, three sample sizes, and three representatives of each zero count adjustment system. The Poisson lognormal distribution provides a convenient method with which to provide variability greater than Poisson. Expected values of the sample estimate of the (known) population mean were calculated for each of the 576 combinations of these factors, and the bias associated with each combination was derived. The bias associated with the three representatives of the variable adjustment system was similar. The variable adjustment system had a lower overall bias than any representatives of the fixed adjustment system.

Animals↗
PubMed2000

The development of the Maze procedure for the treatment of atrial fibrillation.

The Maze procedure was developed for the treatment of atrial fibrillation over a period of several years. Extensive experimental and clinical studies of the underlying electrophysiology of the arrhythmia were performed, and numerous surgical techniques and principles were tried before the Maze procedure was conceived. Few cardiac surgical procedures have undergone more extensive research and experimental trials before being applied clinically. This article gives a brief summary of the work leading up to the eventual Maze-III procedure that is now in clinical use.

Animals↗
PubMed2000

Current status of the Maze procedure for the treatment of atrial fibrillation.

Since the first patient underwent the Maze procedure on September 25, 1987, 346 patients have undergone this operation for the treatment of atrial fibrillation. The procedure was designed as an open-heart operation performed through a median sternotomy. It underwent 2 major modifications relatively early in the series, evolving into the so-called Maze-III procedure, which has been used exclusively since April 16, 1992. Since that time, the Maze-III procedure has been adapted to allow it to be done by minimally invasive techniques. In addition, we recently performed the entire procedure in 2 patients without the use of cardiopulmonary bypass. The operative mortality rate has remained at 2% to 3%. This includes patients undergoing concomitant high-risk cardiac surgical procedures and all re-do cases. The overall success rate in curing atrial fibrillation has been 99%. The procedure itself has been shown to cause no permanent damage to the sinus node. The left atrium has been documented to function long-term postoperatively in 93% of patients and the right atrium functions in 99% of patients. The Maze-III procedure remains the surgical procedure of choice for the treatment of medically refractory atrial fibrillation.

Atrial Fibrillation↗
PubMed2000

The importance of cryoablation of the coronary sinus during the Maze procedure.

Although the Maze procedure has proven to be very effective in the treatment of atrial fibrillation, some authors have chosen to delete some of the important steps of the technique. Both our experimental and clinical experiences with the Maze procedure indicate that 1 of the most important principles is to interrupt conduction across the posterior-inferior portion of the left atrium. This is accomplished by creating a transmural lesion in the myocardium and then creating a circumferential lesion at the same site in the coronary sinus. We have used surgical incisions in the atrium and a cryolesion in the coronary sinus to block conduction in this area. If either fails, there is a high rate of arrhythmia recurrence.

Atrial Fibrillation↗
PubMed2000

The Maze-III procedure combined with valve surgery.

Previous studies have suggested that the Maze procedure is not as effective in controlling atrial fibrillation when the arrhythmia is associated with significant valvular heart disease. In this study, we evaluate our own results in 83 patients who underwent 96 valve procedures in combination with the Maze-III procedure. Our results indicate that the Maze-III procedure is just as safe and effective in controlling atrial fibrillation associated with valvular heart disease as it is in controlling atrial fibrillation not associated with valvular heart disease.

Aged↗
PubMed2000

Stroke prevention as an indication for the Maze procedure in the treatment of atrial fibrillation.

The Maze procedure has proven to be extremely effective in curing medically refractory atrial fibrillation. This analysis of our surgical results with the Maze procedure indicates that the Maze procedure, with or without associated cardiac surgery, has the lowest perioperative stroke rate of any major cardiac surgical procedure. This is surprising in view of the fact that all of the patients who undergo the Maze procedure have an elevated risk of stroke because of the presence of atrial fibrillation. In addition, many of the patients have already had strokes, further increasing the likelihood of perioperative stroke. Only 1 patient has had a stroke in the 12-year follow-up period following the Maze procedure. This is comparable to the risk of stroke in the general population and indicates that the Maze procedure essentially abolishes the risk of stroke associated with atrial fibrillation.

Adult↗
PubMed2000

Observations on the perioperative management of patients undergoing the Maze procedure.

In addition to the usual measures that constitute optimal perioperative care after cardiac surgery, the Maze procedure demands several other measures because of certain complications that are unique to this particular operation. These complications include preoperative conditions such as amiodarone therapy, thromboembolism, diastolic dysfunction of the left ventricle, and associated valvular heart disease, as well as intraoperative differences that include multiple atriotomies and excision of both atrial appendages. The most common postoperative complications are atrial arrhythmias, excessive fluid retention, and pulmonary complications. In this article, we outline our own approach to the perioperative care of patients undergoing the Maze procedure.

Atrial Fibrillation↗
PubMed2000

New surgical and catheter-based modifications of the Maze procedure.

There is currently an intense interest in applying the principles of the Maze procedure in a less invasive manner so that a wider group of patients with atrial fibrillation can be treated safely and effectively. These efforts have centered around surgical attempts to curtail the number of lesions placed in the atria at the time of valve surgery and catheter-based attempts to re-create a part or all of the Maze procedure with radiofrequency ablation. Thus far, these techniques remain highly experimental and largely without merit. Many of the problems that we encountered several years ago in developing the surgical Maze procedure are now being repeated in patients undergoing these highly experimental and inadequately evaluated procedures. Nevertheless, there are occasional flashes of promise with some of these approaches. Moreover, it is clear that only a miniscule percentage of the patients with atrial fibrillation will ever become candidates for the open-heart Maze procedure as it is now performed. Therefore, the continuing struggle to relieve the invasive downside of the Maze procedure is warranted but with the caveat, especially to our cardiologist colleagues, to proceed with caution.

Animals↗