The impact of aerobic exercise on blood pressure variability

There is increasing evidence that blood pressure variability (BPV, variation of blood pressure over time) constitutes a strong and independent marker of cardiovascular risk. The all-cause mortality is >50% greater in subjects with a standard deviation of inter-visit blood pressure >5 mm Hg. Regular aerobic exercise reduces blood pressure and is recommended by current hypertension guidelines as a basic lifestyle modification. It remains elusive, however, whether aerobic exercise is able to reduce BPV as well. In total, 72 hypertensive subjects were randomly assigned to an 8-12-week treadmill exercise program (target lactate 2.0±0.5 mmol l(-1)) or sedentary control. Blood pressure was measured by 24 h-ambulatory blood pressure monitoring (ABP). Two aspects of BPV were assessed: the variability of ABP and the variability of blood pressure on exertion. The coefficient of variation (CV) was used as a statistical measure of BPV. The CV of systolic daytime ABP was defined as primary outcome. The exercise program significantly decreased systolic and diastolic daytime ABP by 6.2±10.2 mm Hg (P<0.01) and 3.0±6.3 mm Hg (P=0.04), respectively. Moreover, it reduced blood pressure on exertion and increased physical performance (P<0.05 each). Exercise had no impact, however, on the CV of daytime (10.2±2.7 vs. 9.8±2.6%, P=0.30) and night-time systolic (8.9±3.2 vs. 10.5±4.1%, P=0.10) and diastolic ABP (daytime 11.5±3.3 vs. 11.5±3.1%, night-time 12.0±4.3 vs. 13.8±5.2%; P>0.05 each). Regular aerobic exercise is a helpful adjunct to control blood pressure in hypertension, but it has no effect on 24 h- BPV, an independent predictor of cardiovascular risk.

MOCVD OF SnO2 on Silicon Microhotplate Arrays for use un Gas Sensing Applications

The quantitative detection of gas concentrations in mixed atmospheres is becoming increasingly important in manufacturing processing, environmental monitoring, and medical diagnostics. Several conductive oxides, such as SnO2, ZnO, and TiO2, are well known to exhibit changes in resistivity when exposed to various gases at temperatures ranging from 200–500°C. Current discrete devices based on resistive changes such as the Taguchi sensor, however, suffer from certain performance problems, including poor gas detection specificity. Integrated arrays of sensors, fabricated using planar technology, offer a promising solution to these problems, as well as other benefits such as low power consumption and low cost.

In this paper, we report the results of using Metalorganic Chemical Vapor Deposition (MOCVD) to fabricate thin films of SnO2 on microhotplate arrays. The studied arrays contain 4 micromachined, suspended elements, each having an integrated resistive heater that produces a rapid thermal rise time ∼3 msec. By separately heating individual elements, we can take advantage of the thermally selective nature of the MOCVD process to limit deposition to these areas, resulting in a maskless deposition process. In addition, these array elements have surface electrical contacts that permit the measurement of the resistance of the thin films during deposition, as well as when they are operated in a gas sensing mode. In situ growth measurements will be reported.

Effects of an endurance and resistance exercise program on persistent cancer-related fatigue after treatment

BACKGROUND

Fatigue is a relevant problem of cancer patients during and after treatment. Several studies have shown that exercise can improve quality of life and functional status of cancer patients undergoing chemo- or radiotherapy. However, there is a lack of information about the effects of this intervention on persistent cancer-related fatigue. Therefore, we assessed the effects of an exercise program on cancer-related fatigue after treatment.

PATIENTS AND METHODS

A consecutive series of 32 cancer patients with mild to severe persistent fatigue [scores on the Brief Fatigue Inventory (BFI) > 25] participated in a 3-week exercise program consisting of endurance (30 min walking on a treadmill) and resistance/coordination exercises for the major muscle groups. Fatigue, mood, and anxiety were assessed with questionnaires and physical performance with a stress test before and after the program.

RESULTS

At the end of the program, we observed a significant increase of physical performance (workload at the anaerobic threshold pre 61 +/- 26 W, post 78 +/- 31 W, P < 0.0001) and reduction of global fatigue (Functional Assessment of Cancer Therapy: pre 45.7 +/- 13.4, post 52.6 +/- 12.4, P < 0.0001; BFI: pre 37.9 +/- 18.3, post 31.2 +/-17.1, P < 0.001). However, no significant improvement of cognitive fatigue or reduction of anxiety was observed.

CONCLUSIONS

A 3-week exercise program leads to a substantial improvement of physical performance and reduction of mental and physical fatigue in cancer patients after treatment. However, this intervention does not affect depression, anxiety, or cognitive fatigue.

Beta-blockers do not impair the cardiovascular benefits of endurance training in hypertensives

Aerobic physical exercise is broadly recommended as a helpful adjunct to obtain blood pressure control in hypertension. Beta-blockade interacts with heart rate, sympathetic tone, maximal workload and local lactate production. In the present randomized-controlled study, we compared the cardiovascular effects of an endurance training programme in elderly hypertensives with or without beta-blockers and developed a first approach to determine a lactate-based training heart rate in presence of beta-blockade. Fifty-two patients (23 with beta-blocker, 29 without beta-blocker) > or =60 years with systolic 24-h ambulatory blood pressure (ABP) > or =140 mm Hg and/or antihypertensive treatment were randomly assigned to sedentary activity or a heart-rate controlled 12-week treadmill exercise programme (lactate 2.0 mmol/l). In the exercise group, the training significantly decreased systolic and diastolic 24-h ABP, blood pressure on exertion (100 W) and increased endothelium-dependent vasodilation (flow-mediated vasodilation, FMD) and physical performance both in the presence and absence of beta-blockade (P<0.05 each). The extent of ABP reduction did not significantly differ in the presence or absence of beta-blockade (Delta systolic ABP 10.6+/-10.5 vs 10.6+/-8.8 mm Hg, Delta diastolic ABP 5.7+/-8.6 vs 5.8+/-4.0 mm Hg). Mean training heart rate was significantly lower in the patients on beta-blockers (97.2+/-7.7 vs 118.3+/-7.5/min, P<0.001). Lactate-based aerobic endurance training evokes comparable cardiovascular benefits in the presence and absence of beta-blockade including a marked improvement of endothelial function. In the present study, target training heart rate with beta-blockers is about 18% lower than without.

A randomised, controlled study on the effects of a short-term endurance training programme in patients with major depression

OBJECTIVE

To evaluate the short-term effects of exercise in patients with major depression.

DESIGN

Prospective, randomised, controlled study.

SETTING

A university hospital.

PATIENTS

A consecutive series of 38 inpatients with a major depression episode undergoing standard clinical antidepressant drug treatment.

INTERVENTIONS

Patients were randomly assigned to an exercise (walking, n = 20) or placebo (low-intensity stretching and relaxation exercises, n = 18) group. Training was carried out for 10 days.

MAIN OUTCOME MEASUREMENTS

Severity of depression assessed with the Bech-Rafaelsen Melancholy Scale (BRMS) and the Center for Epidemiologic Studies Depression scale (CES-D).

RESULTS

After 10 days, reduction of depression scores in the exercise group was significantly larger than in the placebo group (BRMS: 36% v 18%; CES-D: 41% v 21%; p for both = 0.01); the proportion of patients with a clinical response (reduction in the BRMS scores by more than six points) was also larger for the exercise group (65% v 22%, p<0.01).

CONCLUSIONS

Endurance exercise may help to achieve substantial improvement in the mood of selected patients with major depression in a short time.

Endurance exercise and the production of growth hormone and haematopoietic factors in patients with anaemia

BACKGROUND

Physical activity has been shown to stimulate haematopoiesis in patients with anaemia due to chronic renal failure or haematological malignancies.

OBJECTIVE

To evaluate the effect of moderate exercise on the production of haematopoietically active factors.

METHODS

Ten patients (four men and six women, mean (SD) age 51 (10) years) with a haemoglobin concentration under 130 g/l (men) or 120 g/l (women) carried out five three minute exercise bouts at an intensity of 80% of the maximal heart rate, corresponding to a lactate concentration of 3 (0.5) mmol/l. Patients rested for three minutes between bouts. The concentrations of interleukin 6, stem cell factor, granulocyte-monocyte colony stimulating factor, granulocyte colony stimulating factor, erythropoietin, and growth hormone (GH) were evaluated before and in the eight hours after exercise.

RESULTS

GH had risen significantly 15 minutes after exercise (1.1 (1.3) v 2.7 (2.8) ng/ml; p<0.05). No change in the concentration of the other cytokines and growth factors was observed in the eight hours after exercise.

CONCLUSIONS

In patients with anaemia, submaximal exercise does not affect the concentration of haematopoietically active cytokines. However, it leads to an increased concentration of GH. This may be responsible for the improved haematopoiesis observed after an exercise programme in patients with chronic diseases.

Physical performance, depression, immune status and fatigue in patients with hematological malignancies after treatment

BACKGROUND

Fatigue is a frequent and severe problem after treatment of patients with hematological malignancies. This symptom has been associated with anemia, reduced physical performance, mood, endocrine disorders and impaired nutritional status. Recently, it has been suggested that fatigue can be related to a persistent activation of the immune system with increased production of proinflammatory cytokines. However, there is no conclusive evidence regarding the role of the immune system in the origin of fatigue in cancer patients.

PATIENTS AND METHODS

We evaluated the correlation of fatigue with thyroid function, markers of immune activity [interleukin (IL)-1alpha, IL-1 soluble receptor, IL-6, C-reactive protein and neopterin], liver and kidney function, mood and physical ability in 71 patients with hematological malignancies. All patients had been free of relapse and not received treatment (chemotherapy, radiotherapy or immune modulators) for at least 3 months.

RESULTS

Fatigue was related to depression (r=0.84; P<0.0001) and reduced performance status (r=-0.61; P<0.0001). However, there was no correlation between fatigue and thyroid, liver and kidney function, anemia, albumin concentration or markers of immune activity (all r-values <0.20; P>0.05).

CONCLUSIONS

We conclude that fatigue in relapse-free patients with hematological malignancies is associated with depressive mood and reduced physical performance, but not with impairment of thyroid function, anemia or persistent activation of the immune system.

Stem cell mobilization in multiple myeloma patients: Do we need an age-adjusted regimen for the elderly?

The upper age limit for autologous progenitor cell transplantation in multiple myeloma patients is increasing continuously. We examined whether this shift in the age of pretreated myeloma patients requires modification of mobilization regimen. We compared retrospectively 21 consecutive progenitor cell mobilizations in 15 pts < 60 years (median age 56, range 37-59) with 33 consecutive mobilizations in 23 pts > 60 years (median age 65, range 60-73) of age. The number of CD34 positive circulating cells before scheduled leukapheresis was a mean of 67,935 cells/mL (SEM +/- 17,614) in the younger population and a mean of 19,069 (SEM +/- 5,396) for older pts (P = 0.0027). In patients >60 years, 13/33 mobilizations (including 2 patients with 2 failing attempts) were not successful (39%), compared to 6/21 mobilizations (29%, including 1 patient with 3 failing attempts) in the younger population. The increased number of progenitor cells in the grafts of younger patients led to a more rapid regeneration of leukocytes and platelets after stem cell infusion. Our data show that stem cell mobilization in older multiple myeloma patients is inferior compared to a younger patient population. There is a trend towards more leukapheresis until the target stem cell dose has been collected, and the decreased number of progenitor cells in the actual graft delays engraftment of leukocytes and platelets. The overall number of unsuccessful mobilization attempts, however, did not differ significantly between both age groups. A special "age-adjusted" increase in the dose of growth factors seems unjustified. Improvements in timing of leukapheresis, growth factor application, and mobilizing chemotherapy regimen as well as the use of alternative cytokines should be investigated for both age groups.

Health-related quality of life and pulmonary function in lung cancer patients undergoing medical rehabilitation treatment

Treatment for lung cancer results in reduced Quality of Life (QoL) and limited lung function are well-known. Yet, there are no results available concerning the interaction of objective lung function tests and QoL parameters for lung cancer patients during in-patient cancer rehabilitation. This is also true for outcome parameters in medical rehabilitation. The aim was to study the impact of lung and cardiopulmonary function on QoL (EORTC-QLQ C-30 and SF-36 Health Survey) and to identify possible outcome parameters for a rehab program. 56 lung cancer patients participated. Inpatient rehabilitation consisted of individual aerobic exercise and physical, psychological, social, educational and recreational components and only led to a gain of QoL by SF-36 Health Survey sub scales "Vitality" and "Mental Health". Lung function parameters improved; yet the correlation between lung function and health-related QoL questionnaires was not significant. Multivariate analysis for groups with high and low performance in lung functioning showed differences in the SF-36 Health Survey "Vitality" and "Mental Health" sub-scales. However, patients with high and low functional performance of the lungs did not differ in their QoL over time. Health-related QoL and pulmonary function therefore seem to be independent dimensions. Thus, for judging the outcome and success of medical rehabilitation of lung cancer patients, both, QoL and pulmonary function have to be taken into account.

Benefits from aerobic exercise in patients with major depression: a pilot study

BACKGROUND

Several reports indicate that physical activity can reduce the severity of symptoms in depressed patients. Some data suggest that even a single exercise bout may result in a substantial mood improvement.

OBJECTIVE

To evaluate the short term effects of a training programme on patients with moderate to severe major depression.

METHODS

Twelve patients (mean (SD) age 49 (10) years; five men, seven women) with a major depressive episode according to the Diagnostic and Statistical Manual of the American Society of Psychiatry (DSM IV) criteria participated. The mean (SD) duration of the depressive episode was 35 (21) weeks (range 12--96). Training consisted of walking on a treadmill following an interval training pattern and was carried out for 30 minutes a day for 10 days.

RESULTS

At the end of the training programme, there was a clinically relevant and statistically significant reduction in depression scores (Hamilton Rating Scale for Depression: before, 19.5 (3.3); after, 13 (5.5); p = 0.002. Self assessed intensity of symptoms: before, 23.2 (7); after, 17.7 (8.1); p = 0.006. Values are mean (SD)). Subjective and objective changes in depression scores correlated strongly (r = 0.66, p = 0.01).

CONCLUSIONS

Aerobic exercise can produce substantial improvement in mood in patients with major depressive disorders in a short time.

Aerobic exercise as therapy for cancer fatigue

PURPOSE

Fatigue and impairment of physical performance are common and severe problems of cancer patients. We describe the effect of an aerobic exercise program designed for cancer patients suffering from these symptoms.

METHODS

Five cancer patients (4 female, 1 male, age 18 to 55), participated in the training program. Fatigue had been present for a time ranging between 5 wk and 18 months and hindered the patients from carrying out normal daily activities. The training program consisted of walking daily on a treadmill with an intensity corresponding to a lactate concentration of 3 +/- 0.5 mmol.L-1 and was carried out for 6 wk.

RESULTS

By the end of the exercise program we observed an improvement in maximal physical performance (from 6.4 +/- 0.4 km.h-1 to 7.5 +/- 0.9 km.h-1, P < 0.05) and maximal walked distance (from 1640 +/- 724 m to 3300 +/- 953 m, P < 0.05). Heart rate and lactate concentration by an equivalent submaximal workload (5 km.h-1) were significant reduced (from 138 +/- 21 beats.min-1 to 113 +/- 20 beats.min-1, P < 0.05, and from 2.6 +/- 1.4 mmol.L-1 to 1.3 +/- 0.6 mmol.L-1, P < 0.05); all patients experienced a clear reduction of fatigue and could carry out normal daily activities again without substantial limitations.

CONCLUSION

We conclude that an aerobic exercise program of precisely defined intensity, duration, and frequency can be prescribed as therapy for primary fatigue in cancer patients.

Ultra-triathlon-related blood-chemical and endocrinological responses in nine athletes

BACKGROUND

Objective of this study was to get more insight in hematology, biochemistry, and endocrinology of ultra-endurance exercise, to improve knowledge in this field, supplementation, and medical care of affected athletes.

METHODS

A large body of individual hematological, biochemical, and endocrinological parameters was analyzed in the blood taken from ultra-athletes before and after completing the 1993 Colmar ultra triathlon covering 7.5 km swimming, 360 km cycling, and approximately 85 km running.

PARTICIPANTS

Nine experienced ultra-athletes participated in the study. A follow-up was not possible since the athletes left Colmar within 24 hrs after the contest.

RESULTS

The athletes finished the ultra-contest at rankings 4, 5, 7, 8, 9, 11, 18, 22, 23 in a total time between 23:38:53 and 27:54:30 hr:min:sec. Their final body mass (68.6 +/- 1 kg) was significantly lower than at baseline (71.9 +/- 4.2 kg). Non of the athletes made use of medical care. Data after this contest reflect mild hyponatremia, intravascular hemolysis, increased triglyceride turnover, acute-phase reaction, hyperaldosteronemia 2061 +/- 1013 pmol.L-1), hypercortisolemia 971 +/- 486 nmol.L-1), hyper-growth-hormonemia (median 6.8 ng.ml-1), hypoinsulinemia, hypo-free-testosteronemia (42 +/- 17 pmol.L-1), protein catabolism, depressed testicular function, oliguria, and muscle cell leakage.

CONCLUSIONS

In our opinion, data presented do not reflect any acute health risks in healthy athletes who are well prepared and carefully supplied during such a contest.

Correlation between physical performance and fatigue in cancer patients

BACKGROUND

Fatigue and a reduction in physical ability are common and often severe problems of cancer patients regardless of disease stage and modality of treatment. However, while physical performance can be assessed objectively with laboratory tests, fatigue is a subjective phenomenon whose perception is influenced by past experience and expectations for the future.

PATIENTS AND METHODS

To evaluate the correlation between fatigue and physical impairment, we assessed maximal physical performance with a treadmill test, and mental state with two questionnaires, the Profile of Mood States (POMS) and the Symptom Check List (SCL-90-R), in a successive series of 78 cancer patients with solid tumors or hematological malignancies.

RESULTS

A weak association between fatigue and maximal physical performance was found (r = -0.30; P < 0.01). However, intensity of fatigue showed a strong correlation with several indicators of psychological distress such as depression (r = 0.68), somatization (r = 0.64) and anxiety (r = 0.63; P for all < 0.001). Furthermore, patients with lower levels of physical performance had significantly higher scores for depression (P = 0.005), somatization (P = 0.03) and anxiety (P = 0.08), and significantly lower scores for vigor (P = 0.05) than their counterparts whose physical performance was higher.

CONCLUSIONS

We conclude that fatigue in cancer patients may be related to mood disturbance but appears to be independent of physical performance. Moreover, low physical performance can be viewed as an independent predictor of mental distress in cancer patients.

Effects of aerobic exercise on the physical performance and incidence of treatment-related complications after high-dose chemotherapy

Loss of physical performance is a universal problem of cancer patients undergoing chemotherapy. We postulated that this impairment can be partially prevented by aerobic exercise. In a randomized study, 33 cancer patients receiving high-dose chemotherapy followed by autologous peripheral blood stem cell transplantation (training group, T) performed an exercise program consisting of biking on an ergometer in the supine position after an interval-training pattern for 30 minutes daily during hospitalization. Patients in the control group (C, n = 37) did not train. Maximal physical performance was assessed with a treadmill test by admission and discharge. Physical performance of the two groups was not different on admission. The decrement in performance during hospitalization was 27% greater in the control group than in the training group (P = .05); this resulted in a significantly higher maximal physical performance at discharge in the trained patients (P = .04). Duration of neutropenia (P = .01) and thrombopenia (P = .06), severity of diarrhea (P = .04), severity of pain (P = .01), and duration of hospitalization (P = . 03) were reduced in the training group. We conclude that aerobic exercise can be safely carried out immediately after high-dose chemotherapy and can partially prevent loss of physical performance. Based on the potential significance of the observed outcomes, further studies are warranted to confirm our results.

An aerobic exercise program for patients with haematological malignancies after bone marrow transplantation

We describe the effects of an aerobic exercise program designed to improve the physical performance of patients undergoing bone marrow transplantation. Twenty patients entered the rehabilitation program, consisting of walking on a treadmill, and carried it out for 6 weeks. Patients started the training program 30 +/- 6 days (range 18-42) post-BMT. By the end of the program we observed a significant improvement in maximal physical performance and maximum walking distance, and a significant lowering of the heart rate with equivalent workloads (P for all significances < 0.001). All participants of the program reached a peak performance (calculated in metabolic equivalents, METs) more than sufficient for carrying out all basic activities of daily living. These results contrast with literature reports indicating that spontaneous recovery of physical functioning after BMT can take many months and that about 30% of patients experience long-lasting impairment of physical performance. We conclude that that fatigue and loss of physical performance in patients undergoing BMT can be corrected with adequate rehabilitative measures.

Serum amino acid concentrations in nine athletes before and after the 1993 Colmar ultra triathlon

The amino acid imbalance hypothesis should explain the fatigue originating in the brain during sustained exercise or over-training as a branched-chain (BCAA)/aromatic amino acids (AAA) imbalance with increased brain tryptophan uptake and 5-hydroxytryptamine synthesis. The serum amino acid profile was determined in 9 ultra-triathletes before and after completing the 1993 Colmar ultra-triathlon to additionally analyse the extent of this amino acid imbalance during such an extreme prolonged contest lasting more than 23 hours. The summed serum concentration of 25 amino acids decreased by 18% from 3962 +/- 846 to 3255 +/- 694 umol.l-1 likely reflecting a catabolic state of the organism with a decrease in 18 individual amino acids by 9-56%, an increase in cystine (+38%), methionine (+24%), tyrosine (+10%), phenylalanine (+12%), free tryptophan (+74%), and constant glutamine, leucine and total tryptophan levels. Since plasma volume increased by approximately 7.6% with a 3.3 kg body mass decrease in the athletes during the ultra triathlon, a decrease in intra-cellular water with an extra-cellular fluid increase is hypothesized. This decrease in cellular hydration state is seen as a protein-catabolic signal.

Collateral blood flow from skeletal muscle to normal myocardium

Collateral blood vessels from skeletal muscle to myocardium might supplement intramyocardial collaterals during periods of acute myocardial ischemia. This study was conducted to verify the existence of such collaterals and to measure their contribution to collateral flow. In 12 male goats, the innate coronary collateral system to a moderate size myocardial risk area was defined with colored microspheres, and a latissimus dorsi pedicle flap was then apposed to the heart. After 3 weeks, skeletal muscle to myocardial collaterals were characterized by (a) creation of vascular casts (three animals); (b) estimation of skeletal muscle to myocardial collateral blood flow (three animals); and, (c) measurement of total collateral blood flow to the risk area (innate plus skeletal muscle to myocardial collateral flow). Under a dissecting microscope the vascular casts revealed direct communications from the skeletal muscle which penetrated deeply into the myocardium. With the coronary artery to the risk area open, the estimated myocardial collateral blood flow derived from the muscle flap was 0.01, 0.02, and 0.04 ml/min. With the coronary artery to the risk area closed, there was no significant increase in total coronary collateral blood flow. Although the quantity of blood flow delivered by skeletal muscle collaterals was small, this study demonstrates that clearly identified collateral blood vessels form between skeletal muscle and myocardium in a cardiomyoplasty model. This raises the possibility that, under conditions more favorable to their development, extramyocardial collaterals from skeletal muscle might be exploited to augment the intramyocardial collateral system.

Functional right-heart replacement with skeletal muscle ventricles

Skeletal muscle ventricles were constructed from the latissimus dorsi in seven dogs. All skeletal muscle ventricles underwent a vascular delay period followed by 4-7 weeks of electrical preconditioning. In group 1 (n = 5), the skeletal muscle ventricle was used to replace native right-heart function. Venous return from the superior and inferior venae cavae was directed to the skeletal muscle ventricle with outflow directed to the pulmonary artery. In group 2 (n = 2), the skeletal muscle ventricle was used for partial bypass of the right heart. In both groups, right-heart bypass was continued for as long as 8 hours. In group 1 after 4 hours of continuous complete right-heart bypass, stroke work was 163 +/- 63% of canine right ventricular stroke work. Skeletal muscle ventricle output was 1.14 +/- 0.02 l/min, central venous pressure was 13 +/- 1.5 mm Hg, and systemic systolic blood pressure was 95 +/- 9 mm Hg. Skeletal muscle ventricles are capable of performing the work of the right heart with near-physiological filling pressures.

Skeletal muscle ventricles: improved performance at physiologic preloads

We attempted to construct skeletal muscle ventricles (SMVs) so that they would develop optimal stroke work at physiologic preloads of 5 to 15 mm Hg. Thirty-one SMVs were constructed in mongrel dogs. The effects of electrical preconditioning with 2 Hz continuous and 25 Hz burst patterns were evaluated, as well as the application of passive stretch to the muscle fibers during preconditioning. We evaluated the stroke work developed by these SMVs at afterloads of 30 mm Hg and 80 mm Hg in vivo, using a mock circulation device. During mock circulation studies, the SMVs were stimulated via the thoracodorsal nerve with either a 25 Hz or 85 Hz burst pattern. SMVs with 2 Hz preconditioning developed significantly higher stroke work than SMVs with 25 Hz preconditioning under all conditions of afterload, preload, and stimulation frequency (p less than or equal to 0.001). Under these conditions, for the 2 Hz preconditioned SMVs, passive stretch during preconditioning resulted in a further significant increase in developed stroke work (p less than 0.05). For these SMVs, with an 85 Hz stimulation frequency, stroke work averaged 410% of canine RV stroke work, and 59% of canine LV stroke work at physiologic preloads and afterloads.

Long-term neurostimulation of skeletal muscle: its potential for a tether-free biologic cardiac assist device

Skeletal muscle has a tremendous capacity to adapt. This adaptive phenomenon is seen perhaps to the greatest extent when skeletal muscle is subjected to chronic low frequency stimulation via the motor nerve. There is a decrease in glycolytic enzymes and an increase in oxidative enzymes, as well as a change in the contractile proteins and an increase in the mitochondrial volume fraction of the muscle fiber. These adaptive changes result in a muscle that is considerably more fatigue-resistant. Specifically herein, we report on a pneumatic aortic counterpulsator device powered by skeletal muscle. These muscle pumps functioned continuously and pumped blood effectively in tether-free animals for several weeks.