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1.
Science ; 379(6634): 815-820, 2023 Feb 24.
Article in English | MEDLINE | ID: mdl-36821693

ABSTRACT

Pyrocumulonimbus (pyroCb) are wildfire-generated convective clouds that can inject smoke directly into the stratosphere. PyroCb have been tracked for years, yet their apparent rarity and episodic nature lead to highly uncertain climate impacts. In situ measurements of pyroCb smoke reveal its distinctive and exceptionally stable aerosol properties and define the long-term influence of pyroCb activity on the stratospheric aerosol budget. Analysis of 13 years of airborne observations shows that pyroCb are responsible for 10 to 25% of the black carbon and organic aerosols in the "present-day" lower stratosphere, with similar impacts in both the North and South Hemispheres. These results suggest that, should pyroCb increase in frequency and/or magnitude in future climates, they could generate dominant trends in stratospheric aerosol.

2.
Public Health ; 159: 89-94, 2018 Jun.
Article in English | MEDLINE | ID: mdl-29599056

ABSTRACT

OBJECTIVES: This article presents the findings of a project focusing on building evaluation capacity in 10 Ontario public health units. The study sought to identify effective strategies that lead to increased evaluation capacity in the participating organizations. STUDY DESIGN: This study used a qualitative, multiple case research design. METHODS: An action research methodology was used to design customized evaluation capacity building (ECB) strategies for each participating organization, based on its specific context and needs. This methodological approach also enabled monitoring and assessment of each strategy, based on a common set of reporting templates. A multiple case study was used to analyze the findings from the 10 participating organizations and derive higher level findings. RESULTS: The main findings of the study show that most of the strategies used to increase evaluation capacity in public health units are promising, especially those focusing on developing the knowledge, skills, and attitudes of health unit staff and managers. Facilitators to ECB strategies were the engagement of all staff members, the support of leadership, and the existence of organizational tools and infrastructure to support evaluation. It is also essential to recognize that ECB takes time and resources to be successful. CONCLUSIONS: The design and implementation of ECB strategies should be based on organizational needs. These can be assessed using a standardized instrument, as well as interviews and staff surveys. The implementation of a multicomponent approach (i.e. several strategies implemented simultaneously) is also linked to better ECB outcomes in organizations.


Subject(s)
Capacity Building/methods , Public Health Administration , Public Health Practice , Health Services Research , Humans , Ontario , Qualitative Research
3.
Am J Gastroenterol ; 95(6): 1456-62, 2000 Jun.
Article in English | MEDLINE | ID: mdl-10894578

ABSTRACT

OBJECTIVE: The diagnosis of gastroparesis implies delayed gastric emptying. The diagnostic gold standard is scintigraphy, but techniques and measured endpoints vary widely among institutions. In this study, a simplified scintigraphic measurement of gastric emptying was compared to conventional gastric scintigraphic techniques and normal gastric emptying values defined in healthy subjects. METHODS: In 123 volunteers (aged 19-73 yr, 60 women and 63 men) from 11 centers, scintigraphy was used to assess gastric emptying of a 99Tc-labeled low fat meal (egg substitute) and percent intragastric residual contents 60, 120, and 240 min after completion of the meal. In 42 subjects, additional measurements were taken every 10 min for 1 h. In 20 subjects, gastric emptying of a 99Tc-labeled liver meal was compared with that of the 99Tc-labeled low fat meal. RESULTS: Median values (95th percentile) for percent gastric retention at 60, 120, and 240 min were 69% (90%), 24% (60%) and 1.2% (10%) respectively. A power exponential model yielded similar emptying curves and estimated T50 when using images only taken at 1, 2 and 4 h, or with imaging taken every 10 min. Gastric emptying was initially more rapid in men but was comparable in men and women at 4 h; it was faster in older subjects (p < 0.05) but was independent of body mass index. CONCLUSIONS: This multicenter study provides gastric emptying values in healthy subjects based on data obtained using a large sample size and consistent meal and methodology. Gastric retention of >10% at 4 h is indicative of delayed emptying, a value comparable to those provided by more intensive scanning approaches. Gastric emptying of a low fat meal is initially faster in men but is comparable in women at 4 h; it is also faster in older individuals but is independent of body mass.


Subject(s)
Dietary Fats/administration & dosage , Gastric Emptying , Adult , Aged , Aging/physiology , Animals , Body Mass Index , Cattle , Female , Humans , International Cooperation , Liver , Male , Meat , Middle Aged , Reference Values , Sex Characteristics , Time Factors
4.
J Urol ; 158(4): 1372-5, 1997 Oct.
Article in English | MEDLINE | ID: mdl-9302123

ABSTRACT

PURPOSE: We investigated the effect of a neurovascular intact gracilis muscle urethral wrap to restore urinary continence in men with severe stress urinary incontinence after radical retropubic prostatectomy. MATERIALS AND METHODS: Three men with stress incontinence after radical retropubic prostatectomy and external beam radiation therapy for adenocarcinoma of the prostate underwent gracilis urethral myoplasty. Video urodynamic evaluation and cystourethroscopy revealed Valsalva leak point pressure of less than 40 cm. water and a damaged urinary sphincter mechanism in all 3 patients. One man underwent concomitant ileocystoplasty. RESULTS: At 6 to 24-month followup all patients reported improved continence. Mean Valsalva leak point pressure increased from 26.3 +/- 3.2 cm. water before to 83.0 +/- 32.1 cm. water after surgery. The gracilis muscle urethral wrap did not have a deleterious effect on erectile function or ambulation. Complications included 1 wound infection. CONCLUSIONS: An autologous gracilis muscle urinary neosphincter can be constructed in the bulbous urethra in a fashion similar to that of the artificial urinary sphincter with encouraging results in this preliminary series. The gracilis neosphincter may be an alternative to the artificial sphincter, especially in patients at higher risk for complications, such as after radiation and cryotherapy.


Subject(s)
Prostatectomy/adverse effects , Urinary Incontinence, Stress/etiology , Urinary Incontinence, Stress/surgery , Urinary Sphincter, Artificial , Aged , Humans , Male , Middle Aged , Muscle, Smooth , Severity of Illness Index , Urethra
5.
Spinal Cord ; 35(8): 546-9, 1997 Aug.
Article in English | MEDLINE | ID: mdl-9267922

ABSTRACT

PURPOSE: To investigate the effect of a neurovascularly intact gracilis muscle urethral wrap, to be used to restore urinary continence as a transposed urinary sphincter graft, in patients with neurogenic lower urinary tract dysfunction. METHODS: Five neurologically impaired men with a denervated and damaged urinary sphincter mechanisms were treated. The etiology of sphincteric insufficiency included sphincter denervation in three patients, external sphincterotomy in one, and urethral trauma due to a chronic indwelling catheter in one. All patients underwent gracilis urethromyoplasty sphincter reconstruction. Two patients also underwent concomitant ileocystoplasty and one patient ileocystostomy because of poor bladder compliance and a bladder capacity of < 200 ml. RESULTS: The gracilis urethromyoplasty functioned as a new autologous sphincter with follow-ups ranging from 6-35 months. The surgery was successful in four patients. Three of the four patients were managed with intermittent catheterization, and one managed by ileocystostomy. The fifth patient continued to require an indwelling urethral catheter. CONCLUSION: Gracilis urethromyoplasty achieves compression of the urethra using a neurovascularly intact muscle graft. The functional urethral closure, obtained from the gracilis muscle wrap, assures dryness, and permits intermittent self-catheterization. It also avoids the risks of infection, erosion, or malfunction associated with the artificial urinary sphincter. The potential exists for electrical stimulation of this muscle graft to allow volitional control of the neo-sphincter mechanism, and voluntary voiding.


Subject(s)
Muscle, Skeletal/surgery , Spinal Cord Injuries/complications , Urethra/surgery , Urinary Bladder/surgery , Urinary Incontinence, Stress/surgery , Adult , Electric Stimulation Therapy , Female , Humans , Male , Muscle Denervation , Transplantation, Autologous , Urinary Incontinence, Stress/physiopathology , Urodynamics/physiology
6.
Eur Heart J ; 17(4): 574-82, 1996 Apr.
Article in English | MEDLINE | ID: mdl-8733091

ABSTRACT

The benefits of dual (DDD) over single chamber pacing (VVI) have been demonstrated in haemodynamics, exercise capacity, quality of life and reduced complications in atrioventricular block and sick sinus syndrome. The literature was reviewed to provide complication rates for dual and VVI pacing. Cost calculations were based on United Kingdom 1991 prices. Over a 10-year period, a computer model calculated the incidence and prevalence of atrial fibrillation, stroke, permanent disability, heart failure and mortality in six patient categories: sick sinus syndrome paced VVI, sick sinus syndrome upgraded to DDD, sick sinus syndrome paced DDD from outset, atrioventricular block paced VVI and those upgraded to DDD and atrioventricular block paced initially DDD. Calculations were based on intention to treat. The 10 year survival with DDD vs VVI pacing was 71% vs 57% in sick sinus syndrome and 61% vs 51%, respectively, in atrioventricular block. In both indications the prevalence of heart failure in the 10 year survivors was 60% lower with DDD pacing. In sick sinus syndrome patients paced VVI, 36% had severe disability while only 8% experienced this with DDD pacing. For atrioventricular block the figures were, respectively, 22% vs 3%. The difference in 10 year cumulative cost between VVI and DDD is 13 times the purchase price of a VVI pulse generator for sick sinus syndrome and 7 times for atrioventricular block. In the third year after implantation the cumulative costs of DDD were lower than for VVI for both indications. Dual chamber pacing for both indications, sick sinus syndrome and atrioventricular block, is both clinically and cost effective.


Subject(s)
Cardiac Pacing, Artificial , Heart Block/therapy , Sick Sinus Syndrome/therapy , Atrial Fibrillation/etiology , Cardiac Pacing, Artificial/economics , Cardiac Pacing, Artificial/methods , Computer Simulation , Cost of Illness , Cost-Benefit Analysis , Heart Block/economics , Heart Block/mortality , Humans , Sick Sinus Syndrome/complications , Sick Sinus Syndrome/economics , Sick Sinus Syndrome/mortality , Survival Rate , Treatment Outcome , United Kingdom
7.
Neurourol Urodyn ; 15(3): 223-33, 1996.
Article in English | MEDLINE | ID: mdl-8732989

ABSTRACT

The purpose of this study was to utilize a rat model of bladder augmentation to determine the effect on bladder rupture pressure and volume of bladders augmented using myomyotomy autoaugmentation, intestinal patch ileocystoplasty alone, and a combination of ileocystoplasty and detrusor-myoplasty techniques. Four groups of female rats were studied: 1) sham animals served as controls, 2) ileocystoplasty, 3) autoaugmentation using a myomyotomy technique, and 4) ileocystoplasty reinforced with a rectus muscle flap to envelop the augmented bladder (detrusormyoplasty). One month after surgery bladder rupture pressure and volume were determined by cystometry. Sham control rats manifested bladder rupture at a mean pressure of 154 +/- 43 mmHg and mean volume of 2.5 +/- 2.0 ml. Myomyotomy animals demonstrated a diminished mean rupture pressure and rupture volume (101 +/- 13 mmHg and 1.2 +/- 0.4 ml, respectively) compared to control (both P < 0.05). Ileocystoplasty animals demonstrated bladder rupture at a significantly higher volume of 4.0 +/- 1.9 ml than either myomyotomy or control animals (P < 0.05), although rupture pressure of 111 +/- 49 mmHg did not differ significantly from control values (P = 0.55). The combination of ileocystoplasty and detrusor-myoplasty yielded a statistically significant increase in rupture pressure (262 +/- 108 mmHg) than the other three groups (P < 0.05). Rupture volume in this group of animals did not differ significantly from animals with ileocystoplasty but without detrusormyoplasty (P = 0.46). Bladder autoaugmentation results in a significantly reduced rupture pressure and volume than noted in the native bladder. Although ileocystoplasty significantly increases bladder capacity, the risk of urinary extravasation is also increased with this technique. The combination of ileocystoplasty and detrusor-myoplasty affords not only an increase in bladder capacity, but also significantly increases rupture pressure and thereby decreases the risk of bladder rupture after bladder augmentation.


Subject(s)
Ileum/transplantation , Muscle, Skeletal/surgery , Surgical Flaps/methods , Urinary Bladder/injuries , Urinary Bladder/surgery , Urinary Diversion/methods , Animals , Female , Humans , Pressure/adverse effects , Rats , Rats, Sprague-Dawley , Risk Factors , Rupture, Spontaneous , Surgical Flaps/adverse effects , Urinary Diversion/adverse effects , Urinary Incontinence/surgery
8.
Dis Colon Rectum ; 38(8): 878-85, 1995 Aug.
Article in English | MEDLINE | ID: mdl-7634983

ABSTRACT

PURPOSE: To study muscle behavior for anal sphincter repair, radiologic, manometric, and histologic techniques in a dog animal model have been used. Special attention was given to the problem of resting length of the transposed muscle. METHODS: The semitendinosus muscle of the dog could be transposed successfully to create a new anal sphincter based on an intact neurovascular pedicle. The parallel-fibered muscle was split at its distal end and encircled around the anal canal. Manometry was performed intraoperatively and postoperatively. A sufficiency high basal and squeeze pressure had to be obtained intraoperatively to guarantee a final continent neosphincter. This could be realized by a progressive stretching of the muscle until maximum squeeze is reached. In one animal a pacemaker was implanted, and postoperatively a fixed sphincter stimulation protocol was started. Muscle biopsies of the normal anal sphincter and the neosphincter were taken. RESULTS: 1) Muscle transposition gave a high degree of continence in this experimental model, with a mean resting pressure of +/- 40 mmHg and a mean squeezing pressure of +/- 73 mmHg. 2) Electric stimulation of the neosphincter in one animal influenced the resting pressure but not the squeeze pressure. 3) Muscle fiber type composition changed toward a slow fiber type composition after transposition of the fast muscle and even more after stimulation. CONCLUSIONS: 1) Creation of a muscle cuff around the anal sphincter can substitute normal anal sphincter. 2) Adequate stretch of muscle fibers is essential for continence. 3) Electrical pacing helps preserve resting tension and subsequent continence.


Subject(s)
Anal Canal/surgery , Muscle, Skeletal/transplantation , Surgical Flaps/methods , Anal Canal/diagnostic imaging , Anal Canal/physiology , Animals , Defecation , Disease Models, Animal , Dogs , Electric Stimulation , Male , Manometry , Monitoring, Intraoperative , Muscle Contraction , Muscle Fibers, Slow-Twitch/physiology , Muscle Fibers, Slow-Twitch/ultrastructure , Muscle Tonus , Muscle, Skeletal/pathology , Muscle, Skeletal/physiology , Pressure , Radiography , Rectum/physiology , Surgical Flaps/pathology
9.
Am J Cardiol ; 69(14): 1143-9, 1992 May 01.
Article in English | MEDLINE | ID: mdl-1575182

ABSTRACT

Spinal cord stimulation (SCS) can relieve symptoms in patients with severe angina pectoris refractory to conventional medical or surgical therapy. This symptomatic improvement may result from decreased myocardial ischemia. To test this hypothesis, positron emission tomography (PET) and potassium-38 as a flow tracer were used in 8 patients for the quantitative evaluation of regional myocardial perfusion at rest and after exercise, before and during SCS. Potassium uptake was evaluated as myocardial clearance (flow times net extraction) in ml/min/100 g. Tomographic segments were categorized as nonaffected and affected on the basis of the absence or presence of arterial stenosis on coronary angiography and on the basis of thallium scintigraphic data. In nonaffected segments, before SCS, regional myocardial clearance significantly increased from rest (28 +/- 4) to exercise (47 +/- 13 clearance units; p less than 0.004). A similar increase occurred after SCS. In affected segments, before SCS, regional myocardial clearance barely increased (p = 0.065) from rest (26 +/- 6) to exercise (33 less than or equal to 12). In comparison, after SCS, the resting regional myocardial clearance was slightly elevated (29 +/- 8) reflecting an increased double product, but did not increase (p = 0.192) with exercise (34 +/- 12). However, the magnitude and duration of ST-segment depression decreased during treatment with SCS. Anginal pain occurred in all patients during control exercise, but was attenuated in all but one with SCS. These results indicate that SCS improves exercise-induced angina and electrocardiographic signs of ischemia but this influence does not appear to be mediated by changes in regional myocardial perfusion.


Subject(s)
Angina Pectoris/diagnostic imaging , Angina Pectoris/therapy , Electric Stimulation Therapy/methods , Tomography, Emission-Computed , Aged , Angina Pectoris/physiopathology , Electrocardiography , Humans , Middle Aged , Potassium Radioisotopes , Spinal Cord
10.
Lancet ; 338(8776): 1163-5, 1991 Nov 09.
Article in English | MEDLINE | ID: mdl-1682590

ABSTRACT

Serious faecal incontinence due to anal sphincter damage should be treated by surgery. Graciloplasty has had limited success because the gracilis is a fast-twitch muscle and fatigues quickly. A favourable outcome in a patient who had dynamic (electrically stimulated) graciloplasty encouraged us to further assess this procedure. Gracilis muscle transposition was done in ten patients with complete anal incontinence due to anal atresia, sphincter damage, or neurogenic causes, and who had had several other unsuccessful treatments. 6 weeks after muscle transposition, intramuscular leads were implanted and connected to an implantable electric stimulator. Eight patients became continent, one patient still has a diverting colostomy, and a fistula developed in the other patient. Anal sphincter pressure improved from 35 mm Hg without stimulation to 62 mm Hg with stimulation at 8 weeks (mean increase 28 mm Hg [95% confidence interval 18, 36], p less than 0.01). Retention time of a phosphate enema increased from 22 to 281 s (mean increase 259 s [82, 436], p less than 0.01). Defaecography showed that the new sphincter was functioning. Defaecation was possible when the stimulator was turned "off" with a magnet. Dynamic graciloplasty can restore continence and it improves quality of life in faecally incontinent patients for whom other treatments have been unsuccessful.


Subject(s)
Anal Canal/surgery , Electric Stimulation Therapy/methods , Fecal Incontinence/surgery , Muscles/transplantation , Adult , Aged , Anal Canal/physiopathology , Combined Modality Therapy , Electrodes, Implanted , Electromyography , Evaluation Studies as Topic , Fecal Incontinence/physiopathology , Female , Follow-Up Studies , Humans , Male , Manometry , Middle Aged , Muscle Contraction/physiology , Muscles/physiopathology
12.
J Card Surg ; 6(1 Suppl): 80-8, 1991 Mar.
Article in English | MEDLINE | ID: mdl-1807515

ABSTRACT

From 1985 to April 1990, 78 clinical dynamic cardiomyoplasty procedures were performed using the latissimus dorsi muscle stimulated with the Medtronic Cardiomyoplasty System. Indications for surgery were mostly ischemic and idiopathic dilated cardiomyopathies with patients in severe cardiac insufficiency (NYHA Class III and IV). Results of this multicenter study (11 centers) indicate that the dynamic cardiomyoplasty procedure can be transferred and reproduced in many centers with low perioperative mortality and that it improves the functional status of patients who survive the procedure. The survival rate suggests a long-term benefit (average implant time: 11.7 months). Although clinical functional improvement was reported, actual hemodynamic augmentations could not be clearly demonstrated under the protocol. Further studies of functional and hemodynamic parameters are necessary to determine if dynamic cardiomyoplasty is efficacious for a well-defined group of congestive heart failure patients. These points will be addressed in forthcoming studies.


Subject(s)
Heart Failure/surgery , Surgical Flaps/methods , Adolescent , Adult , Aged , Assisted Circulation , Child , Clinical Protocols , Electric Stimulation , Female , Follow-Up Studies , Heart Failure/mortality , Heart Failure/physiopathology , Hemodynamics , Humans , Male , Middle Aged , Muscle Contraction , Thorax
13.
Circulation ; 82(5 Suppl): IV183-9, 1990 Nov.
Article in English | MEDLINE | ID: mdl-2225401

ABSTRACT

The purpose of right atrial cardiomyoplasty is to increase atrial-pulmonary flow in patients undergoing Fontan-type procedures. We developed two surgical techniques to bypass the right ventricle, followed by right atrial cardiomyoplasty with a stimulated latissimus dorsi muscle flap (LDMF). In 10 goats, the left LDMF was transferred into the chest by removal of the second rib. After sternotomy, the right atrial appendages of five goats (group 1) were connected to the distal main pulmonary artery with polytetrafluoroethylene tubing and the proximal pulmonary trunks were ligated. In the other five goats (group 2), under cardiopulmonary bypass, bioprosthetic valves were implanted into the inferior venae cavae. The tricuspid orifice was closed, and the atriopulmonary connection was performed. The left LDMF was sutured over the right atrium and stimulated using synchronous 30-Hz bursts of impulses delivered by a Medtronic Cardiomyostimulator. Hemodynamic studies were performed in the acute phase. Right atrial, pulmonary arterial, and aortic pressures were assessed. Cardiac output was measured using ultrasonic flow studies. LDMF stimulation restored pulsatile pressure patterns in the pulmonary artery and increased the cardiac output. These observations were more evident in the model with caval valvular implant. This functional "ventricularization" of the right atrium could improve long-term results after Fontan-type procedures and extend operative indications. Chronic experimental studies are necessary to evaluate the diastolic and systolic functions of the neo-right ventricle.


Subject(s)
Assisted Circulation/methods , Heart Atria/surgery , Heart Defects, Congenital/surgery , Heart-Assist Devices , Myocardial Contraction/physiology , Surgical Flaps , Animals , Cardiac Output/physiology , Female , Goats , Muscle Contraction/physiology , Muscles/physiology , Pulmonary Artery/physiology
14.
J Heart Transplant ; 9(3 Pt 1): 239-51, 1990.
Article in English | MEDLINE | ID: mdl-2355276

ABSTRACT

Dynamic cardiomyoplasty was conceived to enhance cardiac performance by assisting myocardial contraction. Technically, this procedure consists of placing a pedicled latissimus dorsi muscle flap around the heart and subsequent muscle electrostimulation in synchrony with ventricular systole. Three types of dynamic cardiomyoplasty can be considered. (1) Atrial or ventricular reinforcement is accomplished by wrapping the latissimus dorsi muscle flap around the heart to support hypokinetic or akinetic areas secondary to congenital or acquired diseases. The atrial reinforcement may be performed to improve atrial output after Fontan-type procedures. (2) Ventricular substitution is performed to replace a portion of the ventricular wall. Autologous pericardium is used to create a neoendocardium and facilitate hemostatic closure of the ventricle. The pedicled latissimus dorsi is then secured to replace the resected myocardium. (3) The two previous techniques of ventricular substitution and reinforcement are combined. This reconstructive procedure, which normalizes the ventricular geometrical shape, is particularly useful after extended cardiac resections, such as is done in treatment of large ventricular aneurysms, cardiac tumors, or echinococcal cyst formations. At present, improvement in ventricular function has been obtained in 12 patients at our institution. Preoperative severe cardiac dysfunction was present in all of these patients (New York Heart Association functional class III or IV). Postoperative echocardiography, multigated acquisition scan, and hemodynamic studies demonstrate an improvement in ventricular function and no impairment of ventricular compliance by the muscle flap. After a mean follow-up period of 18 months, all patients are in functional class I or II. We believe that dynamic cardiomyoplasty prolongs and improves the quality of life of patients suffering from severe chronic and irreversible myocardial dysfunction by improving ventricular contraction and limiting cardiac dilatation.


Subject(s)
Assisted Circulation/methods , Electric Stimulation Therapy , Heart Diseases/surgery , Muscles/transplantation , Myocardial Contraction , Electrodes, Implanted , Heart Atria , Heart Ventricles , Heart-Assist Devices , Humans , Pericardium/transplantation , Surgical Flaps
15.
Ann Thorac Surg ; 49(2): 225-30, 1990 Feb.
Article in English | MEDLINE | ID: mdl-2306144

ABSTRACT

The efficacy of skeletal muscle contractile force to augment left ventricular function has been demonstrated experimentally and clinically by the cardiomyoplasty procedure. Another approach in biomechanical cardiac assistance is the use of electrostimulated skeletal muscle in an extracardiac position. We describe an autologous counterpulsating device using the native ascending aorta as a ventricular chamber wrapped by an electrostimulated latissimus dorsi muscle flap (LDMF). This model avoids thrombotic complications observed in skeletal muscle neo-ventricles associated with prosthetic chambers. In 8 goats, a right LDMF was transferred to the thoracic cavity by removal of the second rib. In 4 goats, the diameter of the aorta was enlarged by surgical implantation (using lateral clamping) of an autologous pericardial patch. The LDMF was wrapped around the ascending aorta and electrostimulated using an external diastolic pulse generator connected to a sensing myocardial lead and to LDMF pacing electrodes. Hemodynamic studies were performed (left ventricular, aortic, and pulmonary artery pressures and rate of rise of left ventricular pressure). The LDMF diastolic counterpulsation was performed using a burst of 30 Hz, with a delay from the R wave adjusted to provide optimal diastolic augmentation. Percent increase in the subendocardial viability index was calculated during unassisted and assisted cardiac cycles (1:2) at baseline and after acute heart failure induced by the administration of high doses of propranolol hydrochloride (3 mg/kg intravenously). Diastolic aortic counterpulsation by the stimulated LDMF resulted in a significant improvement in the subendocardial viability index both at baseline and after induced cardiac failure in both groups, though the increase was greater in the group with aortic enlargement.


Subject(s)
Aorta/surgery , Assisted Circulation/methods , Counterpulsation/methods , Muscles/transplantation , Animals , Blood Pressure , Cardiac Output, Low/surgery , Goats , Hemodynamics , Myocardial Contraction , Pericardium/transplantation , Surgical Flaps
19.
Int J Artif Organs ; 11(6): 469-74, 1988 Nov.
Article in English | MEDLINE | ID: mdl-3203974

ABSTRACT

Dynamic cardiomyoplasty involves the use of an electrically stimulated skeletal muscle wrapped around part of the heart to restore or augment myocardial contractility. In our approach, a Latissimus Dorsi muscle flap (LDMF) is transferred to the heart via a partial resection of the second rib, and sutured around the ventricles. The muscle flap is stimulated in synchrony with the heart contractions with bursts of impulses delivered by a "Cardio-Myostimulator" implantable pulse generator via intramuscular electrodes. The object of this study was to identify features of muscle stimulation and to measure the efficacy of L.D. cardiomyoplasty in increasing cardiac output, using an ultrasonic Doppler technique. This report shows the results obtained for goats in which such procedures were performed. Ultrasonic measurements were recorded at the time of cardiomyoplasty and 3-6 months later, during which period the muscle was put progressively into use by slowly increasing the burst frequency content, number of pulses as well as the heart-muscle contraction ratio (3:1, 2:1, 1:1). This postoperative muscle stimulation protocol takes into account the delay of gradual conversion of fast-twitch glycolytic muscular fibers into slow-twitch oxidative, fatigue-resistant fibers, as well as the healing time after cardiomyoplasty required for the muscle flap to recover collateral blood circulation and to adhere to the heart. Results show that synchronous burst stimulation of the muscle flap increases the blood peak velocity in the descending aorta (+36 +/- 8%) and increases the left ventricular stroke volume (+70 +/- 14%).(ABSTRACT TRUNCATED AT 250 WORDS)


Subject(s)
Cardiac Surgical Procedures/methods , Surgical Flaps , Animals , Blood Flow Velocity , Electrocardiography , Female , Goats , Myocardium/pathology , Stroke Volume
20.
Life Support Syst ; 5(4): 323-7, 1987.
Article in English | MEDLINE | ID: mdl-3431152

ABSTRACT

The concept of 'reconstructive cardiac surgery' using a stimulated autologous skeletal muscle has been investigated in this research. Our approach has been to investigate the substitution or reinforcement of a ventricular wall by a contractile tissue. The experiments have demonstrated the feasibility of this technique and the long-term adaptability and adequate electrophysiological properties of the Latissimus Dorsi flap transferred to a heterotopic position over the heart. Long-term biocompatible fatigue resistant muscle stimulation has become possible in experimental and clinical cases as a result of the development of specially designed electrodes and the use of a progressive sequential stimulation protocol to adapt the skeletal muscle to a cardiac support function. Autologous pericardium treated with glutaraldehyde was found to be a suitable material to close the ventricular cavity. Cardiomyoplasty with autologous skeletal muscle to restore ventricular contractility seems to be a valid alternative in addition to current methods of treatment for irreversible myocardial failure.


Subject(s)
Cardiac Output, Low/surgery , Cardiac Surgical Procedures , Muscles/transplantation , Surgical Flaps , Animals , Chronic Disease , Electric Stimulation , Goats , Humans , Myocardial Contraction
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