Increase In Functional Capacity Research Articles

Adaptive and pathological alterations in experimental cardiac hypertrophy.

Based on investigations of various models of experimental cardiac hypertrophy (renal hypertension, spontaneous hypertension, aortic stenosis, swimming training, thyrotoxicosis), an attempt has been made to characterize adaptive and pathological alterations that are inherent to or accompany the process of hypertrophy. In principle, the designation of a process as adaptive is rooted in a teleological point of view and implies that the basic tendency of the respective structural and functional alterations is appropriate for coping with the altered functional requirements. This does not mean, however, that such alterations are favorable under all conditions and in all stages of hypertrophy. Since organisms generally reveal relatively stereotypic reaction patterns, the terms “adaptive” and “pathological” are not mutually exclusive in the final analysis. In the chronically pressure-loaded ventricle, nearly all alterations are ambiguous (myocardial mass increase, prolongation of the action potential, overproportional increase of intracellular contractile material, decrease of myofibrillar ATPase activity). The altered ATPase activity, which is based on a shift in the isoenzyme pattern of myosin in the direction of isoenzyme V3, is accompanied by a decrease in unloaded shortening velocity but an increase in the efficiency of tension development, as is reflected in reduced oxygen consumption (per wall stress and heart rate) of the whole heart under isovolumetric conditions. This change in the elementary contractile process and the myofibrillar ATPase activity need not be interpreted a priori as negative. However, the ability to adapt to other types of loading, e.g., physical exertion with corresponding increase in heart rate, is limited by the specialization for coping with enhanced pressure load. The term “overadaptation” should be reserved for stages and degrees of hypertrophy in which the negative effects of double-faced alterations predominate. Rapid, excessive increase in pressure loading, as well as long-term hemodynamic overloading, leads to degenerative alterations of the myocardium. At the level of the whole ventricle, structural dilatation results in a decreased cardiac efficiency. Fibrosis of the ventricular wall, the pathogenesis of which is not always unequivocal, is also a negative factor for mechanical performance. Since there are pronounced degrees of hypertrophy without connective tissue increase, e.g., in thyrotoxicosis, fibrosis and accompanying decreased distensibility of the myocardium apparently are not necessarily involved in the development of hypertrophy. Ischemically induced alterations stemming from vasculopathy should be distinguished from hypertrophy-induced changes. The adaptive alteration of the heart in swim-trained rats, which involves an increase in myofibrillar ATPase activity and a shift in the myosin isoenzyme pattern in the direction of V1, leads to an increase in functional capacity at all levels and is in agreement with the generally accepted concept of contractility.

Evaluation of the role of coronary angioplasty in patients with unstable angina pectoris

Seventeen patients presenting with unstable angina pectoris underwent percutaneous transluminal coronary angioplasty (PTCA). Despite vigorous medical therapy, all patients were disabled with 10 experiencing refractory in-hospital angina. PTCA was judged successful in 13 patients and resulted in decreased coronary diameter narrowing from 80 ± 16% to 34 ± 13% and reduced transstenotic pressure gradient from 69 ± 13 to 23 ± 12 mm Hg. Regional coronary blood flow (CBF) and myocardial metabolism were assessed at rest and during pacing tachycardia in six patients with left anterlor descending coronary stenosis. Prior to PTCA, neither regional CBF increased nor coronary vascular resistance declined during rapid pacing; myocardial lactate extraction fell, indicating a shift from aerobic to anerobic metabolism. Following PTCA, however, rapid pacing resulted in increased regional CBF, decreased coronary vascular resistance, and preservation of aerobic metabolism. Following PTCA, successfully dilated patients demonstrated marked relief of angina symptoms, increase in functional capacity, and objective exercise ECG and thallium scintigraphic evidence of relief of previously ischemic myocardium. This investigation demonstrates that PTCA, when combined with medical therapy, can be performed safely and successfully in selected patients who present with otherwise refractory unstable angina, and indicates the procedure deserves further study as a therapeutic alternative in this condition.

Effects of exercise training on left ventricular mass in patients with ischemic heart disease

To determine whether exercise training results in increased left ventricular mass in patients with ischemic heart disease, we obtained echocardiograms in 14 coronary patients before and after an average of seven months (range 3 to 14 months) of supervised arm and leg exercise. Each echocardiogram was interpreted jointly by two blinded observers, using three different measurement conventions and a semiautomated method of analysis to minimize errors of interpretation. Exercise training led to subjective improvement in all 14 patients, and to an objective increase in functional capacity in 13 of 14 patients, as evidenced by an increase in maximal oxygen consumption estimated from symptom-limited treadmill exercise testing (8.8 ± 2.7 (SD) and 10.7 ± 2.5 METS before and after training, respectively, p < 0.01). However, this functional improvement was not accompanied by any significant change in left ventricular end-diastolic diameter, or posterior wall or interventricular septal thickness. Likewise, left ventricular cross-sectional area (CSA), an index of left ventricular mass which corrects for altered ventricular volume and theoretically reflects directional changes in mass despite nonuniform wall thickness, did not change significantly after training by any measurement convention (CSA = 18.0 ± 6.5 and 17.6 ± 6.5 cm 2 before and after training, respectively, by American Society of Echocardiography measurements). These data strongly suggest that improved functional capacity after exercise training in patients with ischemic heart disease is not due to exercise-induced left ventricular hypertrophy.

Long-term results after aortic valve replacement with four different prostheses

The long-term results after implantation of isolated aortic ball and disc prostheses were studied. The Starr-Edwards ball valve type 1200 was first used in 80 patients, thereafter type 2300 was used in 173, later the Björk-Shiley and the Lillehei-Kaster disc valves were implanted in 99 and 97 patients according to randomization. The surviving patients with the oldest ball valve were examined after 4.7 and 6.7 years on an average, the others after approximately 2.5 and 4.5 years. The early mortality rate was 15%, and did not differ between the four groups. Even the late mortality rate was quite similar in the patient groups, the five-year survival rate being 65% in patients with ball valves and 68% in those with disc valves, as estimated with the actuarial method. The average reduction of heart size was moderate and quite similar in the four groups, most pronounced in patients with isolated aortic valve involvement. The reduction was greater in patients who received larger rather than smaller valves of all types. Aortic valve replacement resulted in a considerable clinical improvement in patients with all valve types; it corresponded largely to one functional group according to the NYHA classification. The heart size reduction and functional improvement was most moderate in patients with smaller ball valves, which could be anticipated from higher peak systolic gradients than across the other valves used. No significant differences appeared between patients with the larger valves of the four types. The initial improvement, as recorded either by reduction of heart size or increase in functional capacity, had reached its maximum at the first follow-up examination in most patients. The preoperative myocardial function appeared to be the limiting factor which determined what late results could be obtained regardless of the type of valve implanted. The results therefore indicate that more can be achieved by earlier valve replacement than by improving the prostheses.

Effect of chronic pentagastrin, cholecystokinin, and secretin on pancreas of rats.

Pentagastrin (1.5 mg/kg), 20% pure natural cholecystokinin (CCK, 37.5 Ivy dog U/kg) or secretin (25 microgram/kg) was given in a depot carrier subcutaneously to rats 3 times daily for 15 days. The dose of CCK and secretin was submaximal for pancreatic secretion, whereas the dose of pentagastrin was supramaximal for gastric acid secretion. The pancreatic wet weight increased by 12% (P less than 0.01) in the rats treated with pentagastrin, 57% (P less than 0.001) in those treated with CCK, and 9% (P less than 0.01) in those treated with secretin. In CCK-treated rats, the maximal protein and bicarbonate outputs in response to cholecystokinin increased proportionately to the increase in pancreatic weight, but maximal bicarbonate and protein outputs in response to secretin were unaltered. The secretin-treated rats showed a lowered basal secretion of bicarbonate and a lowered sensitivity to secretin stimulation, but the maximal bicarbonate and protein outputs to secretin and CCK were unchanged. Treatment with pentagastrin produced no significant changes in pancreatic responses to secretin or CCK. We conclude that 1) the increase in pancreatic weight produced by repeated injections of cholecystokinin was accompanied by proportional increase in functional capacity as reflected by the increased maximal bicarbonate and protein outputs in response to cholecystokinin, and 2) repeated administration of secretin decreased the sensitivity of the pancreas to secretin without altering maximal bicarbonate response.

Results of treatment of chronic low-back pain at the Portland Pain Center.

We have evaluated 100 consecutive patients with low-back pain admitted to the Portland Pain Center. The average patient had been disabled for about 6 years, and had had an average of two surgical attempts to improve his symptoms. Most of the patients considered had open claims with their Workmen's Compensation carriers. Significant gains were demonstrated in drug reduction, general well behavior, and increased range of motion and exercise tolerance. The Pain Center setting provides a multidisciplinary approach to the treatment of chronic low-back pain. Significant increases in functional capacity are demonstrated.

The effects of 21 and 23 milimeter aortic valve prosthesis on hemodynamic performance and functional capacity in young adults

Early and medium-term improvement of functional capacity and regression of left ventricular hypertrophy was evaluated in the young adult patient group following application of 21 mm or 23 mm bileaflet aortic mechanical valve prosthesis due to aortic stenosis. Methods : Twenty two patients (10 male, 12 female; mean age 27+-8.2 (19-43)) who underwent isolated aortic valve replacement due to rheumatic aortic stenosis, were included in the study. 21 mm and 23 mm bileaflet mechanical prosthesis was used respectively in eight and fourteen patients. The mean body surface area was 1.86 m(2) and 1.68 m(2) respectively in 23 mm and 21 mm prosthesis while 1.73 ±0.25 m(2) for the whole group. Functional capacity was New York Heart Association (NYHA) class II in 9 patients and class III in thirteen patients. Implantation was performed without enlarging the aortic root in all except four patients. In all patients transvalvular gradients, effective orifice area and the diameter of left ventricle were measured with transthoracic echocardiography during rest and after maximal exercise. Mean follow-up was 34±12 months (range 11-57 months). There were no postoperative complications or deaths. All the patients were assessed as NYHA class I with regards to functional capacity (p=0.01). Significant improvements were determined in postoperative mean transvalvular gradient (p=0.005) and left ventricular mass index (p=0.01) when compared with preoperative values. Our findings show that replacement with 21 mm and 23 mm mechanical prosthesis provides a significant improvement in regression of symptoms and increase of functional capacity in young adults in early and mid-period without increasing mortality and morbidity.