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Biomedical subjects

J L Cox

Publications and source records attributed to J L Cox.

At least 127 records · Page 7Linked to original sources
PubMed1994

Restoration of atrial function after the maze procedure for patients with atrial fibrillation. Assessment by Doppler echocardiography.

BACKGROUND: The purpose of the present study was to evaluate the effects of the maze procedure on atrial function in patients operated on for atrial fibrillation. The maze procedure is a new surgical intervention that is designed to restore sinus rhythm and active mechanical atrial contraction as a definitive treatment for patients with atrial fibrillation. METHODS AND RESULTS: Doppler echocardiographic analysis of mitral and tricuspid inflow as well as pulmonary venous flow velocity was carried out in 46 patients 8 +/- 7 months after the maze procedure, and results were compared with those obtained from 27 age-matched control subjects. To evaluate atrial contraction, we determined the presence of atrial contribution to ventricular filling at the mitral and tricuspid valve levels and measured the percent atrial filling fractions of the left and right atria. To evaluate atrial compliance, we measured the systolic and the systolic-to-diastolic flow velocity ratios of the pulmonary venous inflow. Results were compared with similar measurements obtained from control subjects. Restoration of active atrial contraction was detected in 40 of the 46 patients (87%); right atrial contraction was noted in 38 patients (83%), and left atrial contraction was noted in 28 patients (61%). In patients with active atrial contraction, the percent atrial filling fraction of the right atrium was comparable to that of control subjects (32 +/- 7% versus 33 +/- 8%, P = NS), whereas that of the left atrium was smaller (20 +/- 5% versus 36 +/- 7%, P < .005). In addition, compared with control subjects, pulmonary venous flow in maze patients exhibited a reduced systolic component (17 +/- 4 versus 53 +/- 16 cm/s, P < .001) and decreased systolic-to-diastolic flow velocity ratio (0.3 +/- 0.01 versus 1.1 +/- 0.3, P < .001) and velocity integral ratio (0.3 +/- 0.01 versus 1.3 +/- 0.4, P < .001), all suggesting decreased left atrial filling. CONCLUSIONS: The maze procedure restores active right atrial contraction and improves left atrial contraction in most patients. Obtained measurements suggest decreased left atrial compliance and reduced left atrial contribution to ventricular filling compared with control subjects. Despite the reduced indexes, qualitative restoration of function in either atria should translate in improved atrioventricular synchrony and reduction in thromboembolic events in patients with chronic or paroxysmal atrial fibrillation.

Atrial Fibrillation↗
PubMed1994

Comparison of activated coagulation time and whole blood heparin measurements with laboratory plasma anti-Xa heparin concentration in patients having cardiac operations.

Previous reports suggest that activated clotting times do not correlate with heparin concentration during cardiopulmonary bypass. This study was designed to compare whole blood heparin concentration and activated clotting time measurements with laboratory-based plasma heparin concentration. Sixty-two patients having cardiac operations requiring cardiopulmonary bypass were enrolled in this study. The study was conducted in two phases. In phase I of this trial, blood specimens were obtained from 30 patients before heparin administration and after each of three heparin doses (20, 80, and 150 U/kg). In phase II, blood specimens were obtained from 32 patients before heparin administration and 10 minutes after each of the following: heparin administration (250 or 300 U/kg), initiation of cardiopulmonary bypass, achievement of hypothermia, initiation of rewarming, and immediately before discontinuation of bypass. Blood specimens were used to measure activated clotting time (kaolin and celite), whole blood heparin concentration, and anti-factor Xa plasma heparin concentration. In phase I, activated clotting time (celite: r = 0.91; kaolin: r = 0.93) and whole blood heparin concentration (r = 0.98) measurements correlated well with plasma heparin concentration. After initiation of cardiopulmonary bypass (phase II), weak correlations for activated clotting time measurements (celite: r = 0.34; kaolin: r = 0.59) and a strong correlation for whole blood heparin concentration (r = 0.95) were evident when compared with plasma heparin concentration. During bypass, activated clotting time measurements also inversely correlated with temperature (celite: r = -0.21; kaolin: r = -0.19) and hematocrit (celite: r = -0.26; kaolin: r = -0.21). A weak correlation between activated clotting time measurements and plasma heparin concentration is evident during the cardiopulmonary bypass period, probably because of the influence of both reduced hematocrit and temperature on the activated clotting time assay. In contrast, whole blood heparin measurements correlate well with plasma heparin concentration before and during bypass. Further studies are needed to determine whether maintaining heparin levels during cardiopulmonary bypass by monitoring heparin concentration is more effective in preventing consumptive activation of the hemostatic system, reducing bleeding, and minimizing the use of blood products after cardiopulmonary bypass when compared with a protocol based on activated clotting time.

Blood Coagulation↗
PubMed1994

Prospective evaluation and clinical utility of on-site monitoring of coagulation in patients undergoing cardiac operation.

Although laboratory coagulation tests permit a rational approach to both diagnosis and management of coagulation disorders after cardiopulmonary bypass, their clinical utility is limited by delays in obtaining results. This study was designed to evaluate prospectively the impact of on-site coagulation testing on blood product use, operative time, and intraoperative management of microvascular bleeding. Patients who underwent cardiac procedures involving cardiopulmonary bypass and subsequently developed microvascular bleeding were randomly assigned to receive either standard therapy (n = 36) or therapy defined by a treatment algorithm based on results from an on-site coagulation monitoring laboratory (n = 30). No differences were found between treatment groups in hematologic assay data, operative procedures, or duration of cardiopulmonary bypass. Patients treated in accordance with on-site laboratory results (algorithm therapy) received significantly less intraoperative fresh frozen plasma (0.4 +/- 1.1 U versus 2.4 +/- 2.8 U; p = 0.0006) during the treatment interval, had shorter operative times, and had less mediastinal chest tube drainage during the initial perioperative interval (158 +/- 169 ml versus 326 +/- 258 ml; p = 0.003) than did patients in the standard therapy group. Patients who underwent algorithm therapy also received fewer platelet (1.6 +/- 5.9 versus 6.4 +/- 8.2 U; p = 0.02) and red blood cell (1.9 +/- 1.7 U versus 4.1 +/- 4.1 U; p = 0.01) transfusions after the operation. Nine of 36 (25%) standard group patients received initial therapy which differed from that which would have been guided by the on-site algorithm protocol. Our findings indicate that rapid and accurate coagulation test results can guide specific therapy and optimize treatment of microvascular bleeding in patients who undergo cardiac operations.

Blood Coagulation Tests↗
PubMed1993

Five-year experience with the maze procedure for atrial fibrillation.

Between September 25, 1987, and December 31, 1992, 75 patients (53 men, 22 women; average age, 52 years) underwent the maze procedure for the treatment of atrial fibrillation. Six patients had undergone a previous cardiac operation and 28% underwent concomitant cardiac procedures in addition to the maze procedure. One patient (1.3%) died 10 days after undergoing a combined maze procedure and Morrow procedure for the management of chronic atrial fibrillation and hypertrophic obstructive cardiomyopathy. Postoperative atrial pacemakers were required in 40%: 26% for preoperative sick sinus syndrome and 6% for iatrogenic injury of the sinus node, and 8% had pacemakers in place preoperatively. As of December 31, 1992, 65 patients had been followed up for at least 3 months after operation (range, 3 to 63 months). The maze procedure cured atrial fibrillation, restored atrioventricular synchrony, and preserved atrial transport function in 64 of 65 patients (98%). The procedure has been curative without the need for medications in 58 of 65 patients (89%) and with the need for medications in 6 of 65 (9%), with medications failing in only 1 of the 65 patients (2%). The results support the maze procedure as the treatment of choice in patients with medically refractory symptomatic atrial fibrillation.

Adult↗
PubMed1993

Hazards of postoperative atrial arrhythmias.

Between January 1, 1986, and December 31, 1991, 4,507 adult patients underwent cardiac surgical procedures requiring cardiopulmonary bypass. Of these patients, 3,983 patients who did not undergo operation for supraventricular tachycardia and who were in normal sinus rhythm preoperatively form the study group for the present study. Postoperatively, all patients were monitored continuously for the development of arrhythmias until the time of hospital discharge. The incidence of atrial arrhythmias requiring treatment for the most commonly performed operative procedures were as follows: coronary artery bypass grafting, 31.9%; coronary artery bypass grafting and mitral valve replacement, 63.6%; coronary artery bypass grafting and aortic valve replacement, 48.8%; and heart transplantation, 11.1%. For all patients considered collectively, the risk factors associated with an increased incidence of postoperative atrial arrhythmias (p < 0.05 by multivariate logistic regression) included increasing patient age, preoperative use of digoxin, history of rheumatic heart disease, chronic obstructive pulmonary disease, and increasing aortic cross-clamp time. Postoperative atrial fibrillation was associated with an increased incidence of postoperative stroke (3.3% versus 1.4%; p < 0.0005), increased length of hospitalization in the intensive care unit (5.7 versus 3.4 days; p = 0.001) and postoperative nursing ward (10.9 versus 7.5 days; p = 0.0001), increased incidence of postoperative ventricular tachycardia or fibrillation (9.2% versus 4.0%; p < 0.0005), and an increased need for placement of a permanent pacemaker (3.7% versus 1.6%; p < 0.0005). These data provide a basis for targeting specific patient subgroups for prospective, randomized trials of therapeutic modalities designed to decrease the incidence of postoperative atrial arrhythmias.

Atrial Fibrillation↗
PubMed1993

Early cardiac allograft rejection is independent of regional myocardial blood flow.

Noninvasive telemetric monitoring of canine heterotopic cardiac allograft unipolar peak-to-peak amplitude (UPPA) has permitted prospective surveillance for rejection; moreover, this technique is able to reliably detect rejection before the development of histologic evidence of myocyte necrosis. This study was performed to determine whether early cardiac allograft rejection and the accompanying decline in allograft UPPA were associated with alterations in regional myocardial blood flow (RMBF). Seven heterotopic, intrathoracic canine cardiac transplantations were performed using triple-drug immunosuppression. Native hearts and allografts were instrumented with right ventricular and left ventricular epicardial screw-in electrodes connected to subcutaneous telemeters. Daily measurement of native and graft UPPA was performed; using radioactive microspheres, native and graft RMBF were determined during the control period and when UPPA had declined by 15%, 30%, and 45%. Graft histologic status was determined by endomyocardial biopsy at the time of RMBF determination. Mean duration of the study was 19.7 +/- 3.9 days. Rejection was documented in all animals. The UPPA was stable in native hearts; UPPA declined in the allografts after the onset of rejection. A biphasic change in allograft blood flow was seen. Initially RMBF increased as UPPA declined; a 30% to 45% reduction in UPPA was associated with a 41% increase in RMBF (p = 0.028 versus allograft control). Subsequently, a significant decline in blood flow was observed for reductions in UPPA greater than 45% (0.68 +/- 0.44 versus 1.07 +/- 0.47 mL.g-1 x min-1 for a 30% to 45% decline in UPPA; p = 0.007).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Use of intraoperative mapping to optimize surgical ablation of atrial flutter.

The purpose of this study was to develop a surgical treatment for atrial flutter using intraoperative activation sequence mapping to minimize the surgical procedure necessary to ablate the flutter. A canine model (n = 10) of left atrial enlargement was developed by creating a shunt from the left subclavian artery to the left superior pulmonary vein. Sustained atrial flutter was easily induced in this model. The flutter consisted of a single reentrant circuit that rotated around one or two anatomic obstacles linked by a region of functional block. Epicardial templates, consisting of 252 bipolar electrodes, were used to record activation time maps. After localization of the reentrant circuit, surgical incisions were placed to interrupt the pathways. In all 10 animals, flutter could be induced and intraoperative mapping localized the reentrant circuit. Seven circuits were in the right atrium and three were in the left atrium. The operation ablated all of the preoperative circuits. However, in 5 of the animals, flutter originating from a new circuit could be induced. Activation sequence mapping before and after operation demonstrates that there are multiple potential reentrant pathways in this canine model of atrial flutter. Therefore, all potential pathways must be surgically interrupted to prevent inducibility of atrial flutter.

Animals↗
PubMed1993

Long-term effectiveness of surgical treatment of ectopic atrial tachycardia.

OBJECTIVES: The purpose of this study was to determine the long-term clinical outcome of patients with ectopic atrial tachycardias treated surgically. BACKGROUND: Ectopic atrial tachycardia is an uncommon arrhythmia that can be symptomatic and is associated with the development of a cardiomyopathy. Management strategies are not well defined because of the paucity of data on the long-term effectiveness of pharmacologic and nonpharmacologic therapies. METHODS: The long-term clinical impact of medical and surgical therapy was determined in 15 consecutive patients with ectopic atrial tachycardia. All 15 patients were initially treated with antiarrhythmic drugs (mean 5.7 +/- 2.2 drugs/patient). An effective drug regimen was identified in only 5 (33%) of the 15 patients; the remaining 10 patients were treated surgically. In each, individualized surgical procedures were guided by computer-assisted intraoperative mapping, with atrial plaques comprising up to 156 electrodes. Focal ablation was performed in four patients and atrial isolation procedures in six. RESULTS: The 10 patients treated surgically were followed up a mean of 4 +/- 3.2 years. Ectopic atrial tachycardia recurred in one patient. A permanent pacemaker was implanted in two patients, one of whom also required reoperation for constrictive pericarditis. There were no operative deaths. Ectopic atrial tachycardia recurred in three (60%) of the five patients discharged on antiarrhythmic drug therapy during a mean follow-up interval of 6.4 +/- 4.3 years. There was one nonarrhythmic death. CONCLUSIONS: Map-guided surgery demonstrated long-term efficacy in abolishing symptoms in 9 of the 10 patients with ectopic atrial tachycardia. Results demonstrate that surgery is effective for patients with ectopic atrial tachycardias who are not easily treated with antiarrhythmic drugs.

Adolescent↗
PubMed1993

A trainer's perspective of an innovative programme teaching health visitors about the detection, treatment and prevention of postnatal depression.

Health visitors in North Staffordshire, Edinburgh and Lewisham were given the opportunity to participate in a training programme in the detection, treatment and prevention of postnatal depression, based on previously reported successful intervention strategies. They were trained in the use of the Edinburgh Postnatal Depression Scale (EPDS), and given information about the value and practice of non-directive counselling and about preventative strategies. Knowledge acquisition was evaluation by self-report questionnaires given before and after training. The health visitors were encouraged to screen postnatal women at three specified times using the EPDS and to offer non-directive counselling to women who obtained high scores. A baseline measure of the incidence of postnatal depression was obtained by asking health visitors to give an EPDS form to all women in their caseload with a 6-month-old baby before training commenced. A comparison of the number of women with high EPDS scores at 6 months postnatally, before and after training, showed that participation in the programme enabled health visitors to positively influence the emotional well-being of postnatal women. These results have implications for the role of health visitors which is currently being challenged, as well as for components of their training and continuing professional development.

Community Health Nursing↗
PubMed1993

Hemodynamic effects of atrial interaction.

BACKGROUND: Ventricular pressure and volume overload may induce hemodynamically important ventricular interactions mediated by the thick interventricular septum. The purpose of this study was to determine whether analogous hemodynamically manifest atrial interactions occur across the thinner interatrial septum. METHODS: Right atrial (RA) and left atrial (LA) pressures were measured with micromanometer-tipped catheters before and after atrial pressure and volume overload elicited by sequential right ventricular (RV), RA, and septal ischemia induced in nine open-chest dogs. RESULTS: Following RV ischemia, RA pressure increased and RA contraction and relaxation were enhanced, as indicated by an augmented A wave and X descent. Despite decreased LV diastolic size, LA pressure increased, with similar increases in its A wave and X descent. RA ischemia depressed RA contraction and relaxation, resulting in diminished A wave and X descent. Parallel changes occurred in the LA waveform. Following septal ischemia, LA contraction and relaxation were enhanced, as reflected in an augmented A wave and X descent. Despite persistent RA ischemia, the RA A wave and X descent increased. CONCLUSIONS: These findings demonstrate interatrial transmission of pressure and waveform changes that may influence hemodynamic evaluation and cardiac function.

Animals↗
PubMed1993

Simultaneous epicardial and endocardial activation sequence mapping in the isolated canine right atrium.

BACKGROUND: Since the atria are thin-walled structures, most studies that have examined the spread of activation in the atria have assumed that they behave electrophysiologically as a two-dimensional surface. It was the objective of this study to determine whether or not this assumption is true by simultaneously mapping the epicardial and endocardial activation sequences in the right atrium. METHODS AND RESULTS: Identical precisely superpositioned epicardial and endocardial electrode templates with 250 unipolar electrodes each were used to map the isolated canine right atrium (n = 8) during continuous perfusion and superfusion with Krebs-Henseleit buffer. Data were recorded during control conditions (normal sinus rhythm), continuous pacing (S1S1 = 300 msec), and premature stimulation (S1S2 = effective refractory period + 5 msec). Pacing was performed at two sites, one located on the inferior crista terminalis and one lateral to the crista terminalis on a pectinate muscle. Tachyarrhythmias were induced by a single extrastimulus during the continuous perfusion of acetylcholine (10(-3.5) mol/L). Individual electrode sites were correlated with the gross anatomy and histology. Activation time differences were calculated between each two corresponding epicardial and endocardial sites. There were differences in the activation times between the epicardium and endocardium during all experimental conditions. However, the average difference for each condition was < 1 msec, suggesting that overall activation did not spread faster on either the epicardium or the endocardium, even though in certain regions one surface could lead the other. The dispersion of time differences was smallest during normal sinus rhythm and continuous pacing (SD = 5.6-5.8 msec) and largest after premature stimulation (SD = 6.3 msec for crista pacing, p < 0.05; SD = 8.1 msec for pacing lateral to the crista, p < 0.001). Differences in the activation sequence correlated with the underlying anatomic architecture. The largest differences in activation times between the epicardium and endocardium were associated with those regions of the atrium where pectinate muscles ran below the epicardial surface. The pectinate muscles in those areas were often discontinuous with the epicardial surface and facilitated the discordant epicardial-endocardial activation. The discordant activation was also found in regions where the atrial wall thickness was < 0.5 mm and correlated with transmural differences in fiber orientation. A tachyarrhythmia induced in the presence of acetylcholine, which demonstrated a focal activation pattern, was shown to have a reentrant loop that used free-running muscle bundles connecting the epicardial and endocardial surfaces, resulting in a three-dimensional pathway. CONCLUSIONS: The findings of this study demonstrate that epicardial and endocardial activation can be discordant in specific regions and that discordance increases with abnormal activation sequences. Many of the differences in the epicardial and endocardial activation can be correlated with the heterogeneity of the anatomic architecture of the right atrium. The study also demonstrates that reentry can occur in a three-dimensional plane using the epicardial and endocardial surfaces connected by transmural muscle fibers.

Animals↗
PubMed1993

A controlled study of the onset, duration and prevalence of postnatal depression.

In a two-stage screening procedure using the Edinburgh Postnatal Depression Scale and Goldberg's Standardised Psychiatric Interview, 232 women six months after delivery were compared with control women individually matched for age, marital status and number of children, obtained from general practitioner lists, who were not pregnant nor had had a baby in the previous 12 months. No significant difference in the point prevalence of depression at six months was found between the postnatal (9.1%) and control women (8.2%) nor in the six-month period prevalence (13.8% postnatal, 13.4% controls), but a threefold higher rate of onset of depression was found within five weeks of childbirth. The possible explanations relate to the long duration of depression in women with young children, and the stressful effect of childbirth and its psychosocial sequelae.

Adolescent↗
PubMed1993

Lessons learned from computerized mapping of the atrium. Surgery for atrial fibrillation and atrial flutter.

The supraventricular arrhythmias of atrial fibrillation (AF), both chronic and paroxysmal, and atrial flutter (AFL) have been more difficult to study than most other clinical arrhythmias. Initial epicardial mapping studies at Washington University in canine models and in patients undergoing surgical ablation of other supraventricular arrhythmias demonstrated that AFL resulted from a macroreentrant circuit that was thought to occur only on the right side of the atrium with passive depolarization of the left atrial tissue. Atrial fibrillation was initially demonstrated to be considerably more complex with multiple circuits present. Furthermore, these circuits occurred simultaneously on both the right and left atria. Inability to map the atrial septum and the orifices of the pulmonary veins, however, led to the development of second-generation form-fitting experimental endocardial templates for the canine studies and an endocardial right atrial template for the patient studies. These second-generation experimental maps demonstrated that AFL circuits could involve the fixed anatomic obstacles of the right and left atria and adjacent areas of conduction block, frequently involving the septal and pulmonary vein tissue, with passive depolarization of the contralateral atrium. In contrast to this single-circuit mechanism, AF was confirmed to result from varying degrees of multiple reentrant circuits, occurring transiently in time and migrating over the surface of both atria. Furthermore, the single clinical arrhythmia of AF could result from a spectrum of endocardially or epicardially mapped arrhythmias, ranging from rapid AFL with variable atrioventricular block on one end to very fine multiple-circuit AF on the other end. It was clear that the development of a surgical procedure to ablate AF would need to isolate the atrial tissue in such a way that the transient reentrant circuits responsible for AF could not form because they were extinguished by a fixed or surgically created (eg, a suture line) anatomic obstacle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Characterization and surgical ablation of acute atrial flutter following the Mustard procedure. A canine model.

BACKGROUND: A high incidence of refractory atrial flutter has been reported as a late postoperative complication of the Mustard procedure. The objective of this study was to reproduce experimentally the long-cycle-length atrial flutter that occurs in these patients and attempt to ablate the arrhythmia surgically. METHODS AND RESULTS: Nine dogs underwent a simulated Mustard procedure, which included a longitudinal right atriotomy, a septectomy, and a continuous suture line placed in the usual baffle location. All animals were subsequently inducible into sustained atrial flutter after surgery. Activation-time electrophysiological maps of the various pathways of atrial reentry were determined using atrial endocardial molds containing 252 bipolar electrodes. Four distinct reentrant circuits were observed in the following locations: (1) around the tricuspid value annulus (n = 5; cycle length, 175 +/- 5 milliseconds), (2) around the atriotomy incision (n = 2; cycle length, 208 +/- 3 milliseconds), (3) in a pathway involving both atria (n = 1; cycle length, 180 milliseconds), and (4) around the mitral valve (n = 1; cycle length, 135 milliseconds). A common pathway for eight of the nine reentrant circuits included the free-wall segment of the right atrium (excluding the mitral valve circuit). In the first three animals, surgical ablation of the atrial flutter was not attempted, but an incision made perpendicular to the atriotomy down to the tricuspid valve annulus resulted in termination of the atrial flutter in the other six animals. One of these animals was subsequently inducible into an atrial flutter of different morphology (cycle length, 125 milliseconds) that involved an isolated left atrial reentrant circuit. CONCLUSIONS: The Mustard procedure creates several anatomic substrates that increase the probability of the heart to develop atrial flutter, and these may be amenable to subsequent surgical correction.

Animals↗
PubMed1993

Smoking cessation in the elderly patient.

An older smoker tends to be asked less often to quit although he or she has much to gain from achieving a nonsmoking status. Multiple barriers may interfere with attempting to quit including nicotine withdrawal, doubted self-efficacy, other smokers in one's environment, or misperceptions of little gain from quitting. The physician is in a unique position to interact with the older smoker and through careful questioning, outline a quit smoking strategy that has the greatest chance for success. Every older smoker deserves a chance for increased quality as well as quantity in life.

Age Factors↗
PubMed1993

Surgical therapy for atrial fibrillation.

Atrial fibrillation is the most common sustained rhythm other than sinus rhythm encountered in clinical practice. There are three detrimental sequelae to the rhythm of atrial fibrillation, although the relative magnitude of the detriment varies from patient to patient. These include the sensation of the irregular heart beat, the hemodynamic compromise that is associated with the loss of atrial transport function, and the third is the risk of thromboembolism. Twelve years of experimental and clinical investigation have resulted in the development of a surgical procedure to cure patients with both paroxysmal and chronic atrial fibrillation, as well as atrial flutter. The operation is successful in restoring all patients to sinus rhythm, restoring atrial transport function, and in preventing the recurrence of atrial fibrillation. This procedure is becoming the treatment of choice in patients with drug-refractory, symptomatic atrial fibrillation.

Adult↗