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Biomedical subjects

A D Slater

Publications and source records attributed to A D Slater.

At least 19 recordsLinked to original sources
PubMed2001

Vascular delay and intermittent stimulation: keys to successful latissimus dorsi muscle stimulation.

BACKGROUND: The goal of this study was to obtain physiologically significant increases in peak left ventricular (LV) systolic pressure and stroke volume with latissimus dorsi muscle (LDM) stimulation in cardiomyoplasty (CMP). We hypothesized that preserving LDM integrity by vascular delay and intermittent stimulation would significantly increase LDM cardiac assistance. METHODS: In 4 control dogs and 12 dogs that had undergone a vascular delay (VD) procedure, LV dysfunction was induced by intracoronary microsphere injections. Cardiomyoplasty surgery was performed 14 days later, followed by progressive LDM conditioning. In the control dogs and in 6 of the VD dogs, the LDM was stimulated 24 hours per day (VD plus constant stimulation [CS]). In the other 6 VD dogs, LDMs were stimulated on a daily schedule of 10 hours on and 14 hours off (VD plus interrupted stimulation [IS]). Latissimus dorsi muscle stimulated beats were compared with nonstimulated beats 9 weeks later. RESULTS: In the control dogs, LDM stimulation had minimal effects. In VD + CS and VD + IS, LDM stimulation increased peak LV pressure, stroke volume, stroke work, and stroke power (p < 0.05). However, these changes were greater in the VD + IS group, in which LDM stimulation increased peak aortic pressure by 17.6 +/- 1.7 mm Hg, peak LV pressure by 19.7 +/- 1.1 mm Hg, peak positive LV dp/dt by 398 +/- 144 mm Hg per second, stroke volume by 5.1 +/- 0.7 mL, stroke work by 10.9 +/- 0.9 gm.m, and stroke power by 122.7 +/- 11.6 gm.m per second (p < 0.05 compared with VD + CS). Quantitative morphometric analysis showed minimal LDM degeneration in the VD + IS group (7.5% +/- 1.1%), and VD + CS group (10.5% +/- 4.5%) compared with the control group (29.5% +/- 4.5%, p < 0.05). CONCLUSIONS: VD and IS considerably increased the LV assistance with LDM stimulation. Further studies of this combined approach to CMP should be planned.

Animals↗
PubMed1999

Vascular delay of the latissimus dorsi provides an early hemodynamic benefit in dynamic cardiomyoplasty.

OBJECTIVES: Dynamic cardiomyoplasty (CMP) as a surgical treatment for chronic heart failure improves functional class status for most patients. However, significant hemodynamic improvement with latissimus dorsi muscle (LDM) stimulation has not been consistent. The current protocols do not allow early LDM stimulation after CMP surgery. We hypothesized that vascular delay of LDM would increase myocardial assistance after CMP and allow early (48-h) LDM stimulation after CMP. METHODS: Mongrel dogs (n = 24) were divided in four groups: 1) controls (n = 6), single-stage CMP; 2) Group ES (n = 6), single-stage CMP with early LDM stimulation beginning 48 h, postoperatively; 3) Group VD (n = 6), vascular delay of the LDM followed by CMP without early LDM stimulation, and 4) Group VDES (n = 6), vascular delay of LDM (14-18 days), followed by CMP with early stimulation (48 h postoperatively). Two weeks after CMP, global cardiac dysfunction was induced by injecting microspheres into the left coronary artery. LDM-assisted (S) beats were compared with nonstimulated beats (NS) by measuring aortic pressure (AoP), LV pressure, aortic flow, and by calculating first derivative of LV contraction (+/-dP/dt), stroke volume (SV), and stroke work (SW). RESULTS: In ES, LDM stimulation had no effect on the hemodynamic parameters. In the other groups, LDM stimulation significantly (p < 0.05) increased AoP, LVP, dP/dt, SV, and SW. However, these increases were much larger in VD and VDES. In VD, LDM stimulation increased peak AoP by 21.5+/-3.8 mm Hg, LVP by 22.1+/-4.1 mm Hg, dP/dt by 512+/-163 mm Hg/sec, SV by 10.4+/-2.3 mL, and SW by 22.1+/-5.4 g/m(-1). Similarly, in VDES, LDM stimulation increased peak AoP by 24.1+/-4.7 mm Hg, LVP by 26.2+/-4.3 mm Hg, dP/dt by 619+/-47 mm Hg/sec, SV by 6.5+/-0.7 mL, and SW by 16.7+/-4.1 g/m(-1). CONCLUSIONS: In dogs with global LV dysfunction, CMP after vascular delay resulted in a significant improvement in hemodynamic function measured 2 weeks after surgery. This improvement was not provided by single-stage CMP with or without early stimulation. Vascular delay of the LDM before surgery may play an important role for early benefit after CMP, shorten the overall muscle training period, as well as increase hemodynamic response to LDM stimulation.

Animals↗
PubMed1998

Preconditioning of the latissimus dorsi muscle in cardiomyoplasty: vascular delay or chronic electrical stimulation.

OBJECTIVES: In standard single stage cardiomyoplasty (CMP), the latissimus dorsi muscle (LDM) is not preconditioned prior to surgery. We hypothesized that latissimus dorsi preconditioning by vascular delay or by chronic electrical stimulation would result in an improved LV hemodynamic function early (14 days) after CMP. METHODS: Mongrel dogs had preconditioning of the latissimus dorsi by a vascular delay procedure followed by CMP 14-18 days later (group I VD). Dogs in group II underwent 4 weeks of chronic stimulation (CS) of the latissimus dorsi (2 V/30 Hz, six bursts/min) followed by CMP. The latissimus dorsi muscle was fully stimulated from 48 h after cardiomyoplasty in both groups (2 V/30 Hz, three bursts/min). Two weeks after myoplasty, injecting 2.0-3.0 x 10(5) 90 microm latex microspheres in the left main coronary artery induced global cardiac dysfunction. Hemodynamic function was then evaluated for latissimus dorsi muscle assisted (S) beats and non-stimulated beats (NS) in each group by measuring peak systolic aortic pressure (AOP), left ventricular pressure (LVP) and end diastolic pressure (LVEDP), and by calculating maximum and minimum dP/dt. RESULTS: Dogs with vascular delay of the latissimus dorsi showed a marked increase for all hemodynamic indices (AOP: 23.9+/-2.5%, LVP: 23.5+/-2.2%, max dP/dt: 49.4+/-3.3%) for LDM assisted (S) beats compared to non-stimulated beats (P < 0.001). Animals with chronic electrical training did not demonstrate a significant increase in any hemodynamic parameter with LDM stimulation. CONCLUSION: Preconditioning the LDM may play an important role in providing early cardiac assistance in CMP. Preconditioning the LDM with vascular delay resulted in improving performance of the LDM with consistent increases in LV hemodynamics. This was not observed after preconditioning with chronic electrical stimulation. Vascular delay of the latissimus dorsi can significantly improve muscle performance in CMP and could provide hemodynamic assistance early after surgery.

Animals↗
PubMed1997

Variable effects of cardiomyoplasty on left ventricular function.

Cardiomyoplasty (CMP) has been considered as a possible treatment for patients with heart failure. Symptomatic improvements occur almost uniformly among survivors with CMP, but changes in left peak ventricular systolic pressure (PVSP) and stroke volume vary in patients. This study examined whether there is variability present shortly after cardiomyoplasty surgery. Cardiomyoplasty was performed in 11 mongrel dogs with normal ventricular function. Nine to twelve days after CMP, left ventricular (LV) function was evaluated by simultaneously measuring LV volume (conductance catheter) and pressure (Millar catheter). The latissimus dorsi muscle (LDM) was stimulated synchronously with ventricular systole in a ratio of 1:4 to 1:7 to avoid muscle fatigue. Data were analyzed on a beat by beat basis. The PVSP, and maximum dP/dt (+dP/dt) increased, but the absolute value of minimum dP/dt (-dP/dt) decreased in stimulated beats in 7 dogs while 4 dogs did not respond. The net changes in stimulated beats versus nonstimulated beats of PVSP were 6.1 +/- 1.8 mm Hg (4.3%), of stroke work was 4.5 +/- 1.9 gm x m (29.5%), of +dP/dt was 185 +/- 47 mm Hg/s (8%), and of -dP/dt was 168 +/- 43 mm Hg/s (7.8%) (p < 0.05) for all these net changes in the responding group while these variations were not significant in the nonresponding group. From the results of our study, active LDM assist improves left ventricular systolic function, occurring in only 7 of 11 experiments. This improvement is inconsistent and varied individually. The integrity of the LDM, tightness of wrapping, and adhesions might contribute to the variability which is present early after surgery and before the LDM is converted into a fatigue resistance muscle.

Animals↗
PubMed1996

Examination of epimysial leads used to stimulate the latissimus dorsi muscle.

Cardiomyoplasty is a new surgical treatment for heart failure in which the patient's latissimus dorsi muscle (LDM) is isolated, wrapped around the heart, and electrically stimulated to provide cardiac assistance. At present, long term stimulation of the LDM is achieved with intramuscular electrodes, which produce minimal nerve damage. This study examined the use of epimysial electrodes by measuring the epimysial lead characteristics during a four-week LDM training. Lead resistance started at 463 +/- 41 omega after implantation, decreased during the following week (251 +/- 16 omega), and remained less than the initial value during the last three weeks (weeks two: 282 +/- 19 omega and week four: 341 +/- 28 omega). The recruitment properties were similar to nervecuff electrodes: low threshold voltages (week one: 0.75 +/- 0.12, week two: 0.90 +/- 0.33, week four: 0.52 +/- 0.10 V) and a very steep recruitment curve with low saturation voltages. Histological examination revealed normal muscle fibers with no inflammatory response. Epimysial leads may be more convenient for most surgeons because the design does not require any free-dissection of the nerve nor guiding a needle around the nerve with the risk of perforating vessels or nerve branches. These results indicate that epimysial leads are worthy of further investigation.

Analysis of Variance↗
PubMed1993

The effect of interferon-gamma on rejection and neutrophil function following transplantation.

Rats were used as a model for a living heterotopic cardiac allograft organ transplant. Rats treated in this model with recombinant rat interferon-gamma (IFN-gamma) showed accelerated rejection in a dose-dependent fashion. However, rats treated with maintenance doses of cyclosporine and IFN-gamma expressed increased rejection at 20 days that had resolved completely by 45 days post-transplantation. Polymorphonuclear leukocytes (neutrophils) were isolated from the blood of rats, and their function was determined by treating the cells with f-Met-Leu-Phe (fMLP) and measuring superoxide produced. Results indicate that the neutrophils from rats treated with maintenance doses of cyclosporine and IFN-gamma still had increased IFN-gamma-modulated fMLP-induced respiratory burst and that maintenance cyclosporine therapy can inhibit the IFN-gamma-mediated accelerated rejection without compromising the antimicrobial effects of IFN-gamma treatment.

Abdomen↗
PubMed1992

Quantitative electroencephalographic monitoring during myocardial revascularization predicts postoperative disorientation and improves outcome.

We evaluated computerized quantitative electroencephalography for the intraoperative detection of cerebral dysfunction. The quantitative electroencephalogram was recorded continuously during 96 myocardial revascularizations involving hypothermic cardiopulmonary bypass using Cerebrovascular Intraoperative MONitor (CIMON) software. CIMON relies on an adaptive statistical approach to detect subtle, but clinically relevant, changes in electroencephalographic activity indicative of cerebrocortical dysfunction. Relative (percent of total) low-frequency (1.5 to 3.5 Hz) power was chosen as the single quantitative electroencephalographic descriptor because it is an established hallmark of cortical dysfunction and is surprisingly insensitive to moderate changes in body temperature and level of opioid anesthesia. Reference values for this measure were established for each patient after anesthetic induction before sternotomy. The large sample variance often seen in low-frequency power was dramatically decreased by using log-transformed data and allowing each patient to serve as his own control. Quantitative electroencephalographic changes in standard deviation units or z-scores were determined from the individualized reference self-norm. Prolonged (greater than 5 minutes) and statistically significant (greater than 3 standard deviation) focal increases in relative low-frequency power were temperature-corrected to determine a standardized cerebrocortical dysfunction time at 37 degrees C. (CDT37). In phase I (n = 48), this objective quantitative electroencephalogram-based numeric descriptor was used to predict neuropsychologic outcome. These CDT37 greater than 5-minute episodes occurred 38 times in 19 patients. The quantitative electroencephalogram-based descriptor predicted the occurrence of such disorientation (n = 14 or 29%) with a 68% false positive rate but only an 8% false negative rate. Since these intraoperative quantitative electroencephalographic episodes were often (19/38) associated with low (less than 50 mm Hg) pump pressures, phase II (n = 48) sought to correct the quantitative electroencephalographic abnormality and prevent postoperative disorientation by appropriate increases in cerebral perfusion. Although the number of episodes of quantitative electroencephalographic abnormality was similar (n = 31) in phase II, these ischemic events disappeared after prompt elevation of perfusion pressure. The phase II disorientation rate fell significantly (p less than 0.002) to 4%. Thus statistically significant increases in low-frequency electroencephalographic relative power persisting for a temperature-corrected duration of 5 minutes or more are a reliable means of alerting the surgical/anesthesia team to the presence of cerebrocortical dysfunction and provide a rational and objective basis for corrective intervention. This form of electroencephalographic monitoring appears to offer an opportunity for the timely correction of perfusion abnormalities or the administration of cerebroprotectant compounds.

Aged↗
PubMed1991

Lateral thoracotomy for the automatic implantable defibrillator.

In 51 patients who required automatic implantable cardioverter defibrillator implantation without additional cardiac procedures, the lead system was implanted using a lateral thoracotomy approach, with complete muscle sparing in the last 24 patients. Exposure was excellent and allowed repositioning of leads for optimal defibrillation thresholds in 18 patients. Five of 19 patients who had previously undergone intrapericardial procedures required intrapericardial dissection for lead placement to provide satisfactory defibrillation thresholds. There were no intraoperative deaths or infarctions. The 30-day mortality rate of 3.9% was comparable with those in other series, and the use of muscle-sparing techniques and supplemental epidural anesthesia prevented pulmonary complications or the need for prolonged ventilatory support. We favor a muscle-sparing lateral thoracotomy incision for automatic implantable cardioverter defibrillator insertion, particularly in patients with a history of previous intrapericardial procedures.

Adult↗
PubMed1991

Emergency aortocoronary bypass after failed angioplasty.

One thousand two hundred fourteen percutaneous transluminal coronary angioplasties were performed over a 38-month period. Sixty patients required immediate emergency coronary artery bypass grafting after angioplasty failure; 7 of these had evidence of acute myocardial infarction before angioplasty and were excluded from the study. Of the 53 patients remaining, 27 (51%) had electrocardiographic and enzyme evidence of postoperative myocardial infarction. Two patients died (4%), and 10 had postoperative complications (19%). No statistical significance was noted comparing age, sex, incidence of prior myocardial infarction or myocardial dysfunction, time for revascularization, or average number of grafts completed in those with single-vessel (n = 21) versus multiple-vessel (n = 32) coronary artery disease. Postoperatively, those with multiple-vessel disease required intraaortic balloon pump support (p = 0.06) and antiarrhythmic medications more frequently than single-vessel patients (p less than 0.01) and had a higher complication rate (p less than 0.05). Although not reaching statistical significance, the data also suggest a higher death and postoperative myocardial infarction rate in patients with multiple-vessel disease. Emergency coronary artery bypass grafting after failed percutaneous transluminal coronary angioplasty carries a higher morbidity and mortality than elective coronary artery bypass grafting, particularly for patients with multiple-vessel coronary artery disease.

Aged↗
PubMed1991

Is defibrillation testing safe?

Determination of defibrillation thresholds (DFTs) and implantable cardioverter defibrillator (ICD) testing requires repeated inductions of ventricular fibrillation (VF) and defibrillation attempts using known energy outputs. Little is known about the individual and cumulative effects of repetitive brief episodes of VF and hypoperfusion on cerebral function. The potential clinical utility of quantitative electroencephalographic (QEEG) monitoring during intraoperative ICD testing, by using processed 19-channel EEG (0.5-35 Hz bandwidth), was examined in ten anesthetized patients, five males and five females (mean age 62 +/- 10 years), who underwent ICD implantation and testing. Ischemic QEEG patterns were defined as those with a 3 standard deviation increase (P less than 0.01) in absolute delta (1.5-3.5 Hz) power persisting for greater than or equal to 2.5 minutes. The majority (80%) of the VF episodes (70) were accompanied by QEEG "slowing" (doubling of the pre-VF low frequency delta waves amplitude). All the patients (5/5) experiencing greater than 6 VF episodes showed a statistically significant increase in the low frequency amplitude. In contrast, this EEG abnormality was apparent in only one of five patients experiencing less than 6 VF episodes. These results suggest a cumulative QEEG depression associated with ICD testing. QEEG may provide an objective means for establishing an individualized upper safe limit of DFT testing and the total number of induced VF episodes.

Electric Countershock↗
PubMed1991

Continuous arteriovenous hemofiltration in the critically ill patient.

Continuous arteriovenous hemofiltration (CAVH) is a simple extracorporeal treatment for fluid overload, electrolyte imbalances, and removal of uremic toxins. The CAVH technique can be initiated rapidly and allows effective fluid removal without compromising cardiovascular status. This article describes two illustrative cases where CAVH was used to treat fluid overload accompanying in one case cardiogenic shock and in the other case septic shock. CAVH may have contributed to the removal of sepsis-related vasodilators as well as excess fluid. This therapy is an attractive alternative to hemodialysis in the critical care setting and may be the treatment of choice in hemodynamically unstable patients.

Adult↗
PubMed1990

Management of extensive right ventricular injury or rupture.

Most penetrating right ventricular injuries require simple suture repair, but more extensive injury or rupture of the right ventricle may not be amenable to this method. We have developed an approach to the problem and a technique for repair. Compression of the area with early institution of cardiopulmonary bypass will result in decompression of the right ventricle and preservation of perfusion, preventing profound hypotension. Coverage with an onlay autologous tissue patch provides hemostatic control of the defect without compromising ventricular function. Reinforcement with omentum or muscle flap can give additional protection when risk of infection is present. Application of these principles can be lifesaving and insure good cardiac function despite massive injury to the right ventricular myocardium.

Aged↗
PubMed1990

Extended use of bilateral internal mammary arteries for coronary artery disease.

The internal mammary artery is the conduit of choice for coronary artery revascularization. Wide angulation between the left anterior descending coronary artery and obtuse marginal branches and the diseased segments of the coronary arteries can prevent optimal positioning of the left internal mammary artery for sequential anastomoses for revascularization. We describe a technique using a segment of the left internal mammary artery as a free graft sewn in an end-to-side fashion to the in situ left internal mammary artery. This approach has technical and physiological advantages over previously described techniques.

Coronary Artery Bypass↗
PubMed1990

Surgical approach to atrial septal defect in the female. Right thoracotomy versus sternotomy.

Repair of atrial septal defect (ASD) remains a high-benefit, low-risk procedure due to technologic improvements. From July 1981 to December 1986, 35 females (age, 7 months to 28 years) had repair of ASD; 20 by right thoracotomy and aortic cannulation (group 1) and fifteen by median sternotomy (group 2). In general, right thoracotomy was applied to patients with secundum ASD two years or older and without associated lesions, while median sternotomy was applied to patients with ostium primum lesions and/or associated lesions. Patients or their families perceived the cosmetic results superior to the right thoracotomy approach over the median sternotomy. We feel that a right thoracotomy and aortic cannulation is effective in females (2 years and older) with secundum ASD for a superior cosmetic result over median sternotomy. However, females with ostium primum and/or associated lesions should undergo median sternotomy for better cardiac access and safety.

Adolescent↗
PubMed1989

The Pierce-Donachy ventricular assist device as a bridge to cardiac transplantation.

The Pierce-Donachy ventricular assist device (VAD) was used as an attempted bridge to orthotopic cardiac transplantation in 12 patients aged 13 to 55 years. Ischemic (4 patients), dilated (4 patients), acute viral (1 patient), postpartum (1 patient), and hypertrophic cardiomyopathy (1 patient), along with a failed transplant (1 patient), were the causative factors of end-stage cardiomyopathy in these patients. All patients were candidates for orthotopic cardiac transplantation but sustained refractory cardiogenic shock (cardiac index less than 2 L/min/m2). Left VADs were placed in all patients; 7 also required right VADs. Four patients died of hemorrhagic complications less than 24 hours after VAD insertion. Ventricular assist device stabilization was successful in 8 patients and support ranged from eight hours to 64 days. Seven patients successfully underwent orthotopic cardiac transplantation. One died postoperatively of hemorrhagic complications, 6 were discharged from the hospital, and 1 patient died at 3 months of cytomegalovirus infection. Five patients are long-term survivors. The Pierce-Donachy VAD is an effective means for supporting critically ill patients with end-stage cardiomyopathy and cardiogenic shock before orthotopic cardiac transplantation. Death is related to hemorrhagic, rather than infectious or thromboembolic, complications. Patients successfully stabilized with the VAD can undergo orthotopic cardiac transplantation with acceptable mortality and morbidity rates.

Adolescent↗