<p>Large quantities of data have described left ventricular adaptation to endurance training, but basic concepts on left ventricular performance during exercise remain controversial. In this thesis, we present the results of studies of left ventricular dynamics during exercise in 89 endurance-trained athletes.</p><p>Using radionuclide ventriculography, 35 female and 30 male endurance athletes were studied in supine position. During supine exercise at 70% of the age-expected maximal heart rate, the adjustments in left ventricular volumes were small, suggesting a high preload before exercise. Stroke volume increased by changes in the left ventricular end-diastolic volumes but no changes were observed in the end-systolic volumes. Moreover, no significant differences were noted between male and female athletes.</p><p>Contrast echocardiography was utilized when 24 male endurance athletes were studied during upright exercise. An almost linear increase in stroke volume was seen from upright rest to upright exercise at a heart rate of 160 beats per minute. Stroke volume increased by an almost linear increase in end-diastolic volume and showed an initial small decrease in end-systolic volume. The left ventricular cavity became geometrically more spherical with the largest increase in the left ventricular end-diastolic short-axis cavity diameters in the mid and apical part of the left ventricle. Left ventricular long-axis length obtained from the epicardial apex to the middle of the mitral annulus at end-diastole showed no significant change from rest to exercise. The mitral annulus motion contributed to more than 50% of the stroke volume during exercise with no significant difference between septal and lateral annular motion at peak exercise. Major changes were observed in left ventricular filling indices during upright exercise. The mean transmitral pressure gradient showed a linear increase and increased several times as the mean diastolic time decreased, with large reductions in mean left ventricular filling time. Despite the shortened filling time, the heart was able to increase the filling rate (measured as volume per time) five times. This observation verifies that the heart has large reserves at rest and reveals the increase in capacity during exercise.</p>

Chronic aortic regurgitation (AR) of varying degree affects 13% of men and 8.5% of women. In persons with severe AR, the expected length of life and its quality are influenced. Some individuals remain asymptomatic for a long period, due to effective compensatory mechanisms, but dysfunction of the left ventricle (LV) usually begins before symptoms appear and can be irreversible by then. This thesis addresses questions of LV function and optimal time for operation of patients suffering from chronic AR. Moreover, detailed echocardiographic studies of the anatomy of the normal aortic valve have been performed to obtain a better understanding of the in vivo anatomic relations within the aortic root. Patients with chronic AR, without concomitant cardiac disease, were studied both retrospectively (n=88) and prospectively (n=29) and the aortic valves of persons (n=32) free from cardiac disease were investigated. For the retrospectively studied patients, survival was 82% at 10 years which is an improvement compared with previously published results. The majority of the patients, however, had LV dysfunction preoperatively. By studying patients prospectively by echocardiography, radionuclide ventriculography (MUGA) and cardiopulmonary exercise testing (CPET) our aim was to evaluate the predictive value of measurements of LV function at rest and during exercise for postoperative outcome. LV diameters were markedly elevated prior to and diminished significantly after surgery. Patients with an abnormal exercise ejection fraction (EF) response by MUGA preoperatively, presented the same reaction postoperatively. This could not be predicted by LV function determination at rest, or by NYHA functional class. In spite of median NYHA class II, these patients had a low work capacity on CPET, which was neither improved 6 months postoperatively nor correlated to echocardiographic LV dimensions. Thus, both MUGA and CPET may be useful complements for timing of surgery in patients with chronic AR. Assuming that patients would benefit from preservation of their native valves the normal aortic valve was studied to gain detailed information about the echocardiographic anatomy and relations within the normal aortic root. This extended examination of the aortic root may facilitate a better planning of aortic valve‐preserving interventions in the future.

Left ventricular hypertrophy (LVH) and the insulin resistance syndrome are common conditions associated with a markedly increased cardiovascular risk. In a fairly large prospective longitudinal study of men from the general population, we found that an unfavorable serum fatty acid profile and components of the insulin resistance syndrome such as dyslipidemia, obesity and hypertension at age 50 predicted the prevalence of LVH at age 70. In cross-sectional analyses at age 70, several components of the insulin resistance syndrome were significantly related to left ventricular relative wall thickness and concentric remodeling, but less to LVH. Left ventricular relative wall thickness was inversely related to insulin sensitivity in skeletal muscle and borderline significantly directly related to insulin sensitivity in the myocardium in a healthy, normotensive sample of the cohort investigated with positron emission tomography, whereas left ventricular mass index was not related to myocardial or skeletal muscle insulin sensitivity. At age 70, echocardiographic LVH was related to a variety of common electrocardiographic diagnoses. In a prospective mortality analysis with baseline at age 70 and a median follow-up time of five years, echocardiographic and electrocardiographic LVH predicted mortality independently of each other and of other cardiovascular risk factors, implying that echocardiographic and electrocardiographic LVH in part carry different prognostic information. In summary, components of the insulin resistance syndrome predicted LVH twenty years later, but were cross-sectionally more related to increased left ventricular relative wall thickness and concentric remodeling. Echocardiographic and electrocardiographic LVH predicted mortality independently of each other and of components of the insulin resistance syndrome.

Large quantities of data have described left ventricular adaptation to endurance training, but basic concepts on left ventricular performance during exercise remain controversial. In this thesis, we present the results of studies of left ventricular dynamics during exercise in 89 endurance-trained athletes. Using radionuclide ventriculography, 35 female and 30 male endurance athletes were studied in supine position. During supine exercise at 70% of the age-expected maximal heart rate, the adjustments in left ventricular volumes were small, suggesting a high preload before exercise. Stroke volume increased by changes in the left ventricular end-diastolic volumes but no changes were observed in the end-systolic volumes. Moreover, no significant differences were noted between male and female athletes. Contrast echocardiography was utilized when 24 male endurance athletes were studied during upright exercise. An almost linear increase in stroke volume was seen from upright rest to upright exercise at a heart rate of 160 beats per minute. Stroke volume increased by an almost linear increase in end-diastolic volume and showed an initial small decrease in end-systolic volume. The left ventricular cavity became geometrically more spherical with the largest increase in the left ventricular end-diastolic short-axis cavity diameters in the mid and apical part of the left ventricle. Left ventricular long-axis length obtained from the epicardial apex to the middle of the mitral annulus at end-diastole showed no significant change from rest to exercise. The mitral annulus motion contributed to more than 50% of the stroke volume during exercise with no significant difference between septal and lateral annular motion at peak exercise. Major changes were observed in left ventricular filling indices during upright exercise. The mean transmitral pressure gradient showed a linear increase and increased several times as the mean diastolic time decreased, with large reductions in mean left ventricular filling time. Despite the shortened filling time, the heart was able to increase the filling rate (measured as volume per time) five times. This observation verifies that the heart has large reserves at rest and reveals the increase in capacity during exercise.

The investigation of exercise specific left ventricular (LV) adaptations to training have been predominantly cross sectional in design. The purpose of the current thesis was to investigate LV adaptations to short term (6-9 weeks) training to establish if any changes are exercise specific. A correlation study was used to investigate correlations between cardiac variables and MAXOV2&(study 1). Cardiac variables were found to be the strongest predictors for absolute MAXOV2&, MAXOV2&BM and MAXOV2&FFM in cyclists compared to the total sample or sedentary group, predicting 79% (p<0.01), 70% (p<0.01) and 77% (p<0.01) of the variance, respectively. Secondly, it was found that when MAXOV2& was scaled to body mass (BM) or fat free mass (FFM) cardiac variables predicted less of the variance than for absolute MAXOV2&, for all groups. Study 2 investigated the hypothesis that there would be no evidence of LV hypertrophy when there was no increase in FFM. This was achieved by taking sedentary participants through a resistance training programme of 6 weeks duration to control for increases in skeletal muscle hypertrophy. Both resting systolic blood pressure (sBP; p = 0.01, d = 1.19) and diastolic blood pressure (dBP; p = 0.029, d = 0.88) were significantly reduced following the 6 weeks resistance training. One repetition maximum (1RM) bench press significantly increased (p = 0.00, d = -1.44) as did 1 RM parallel squat strength (p = 0.00, d = -1.86), with no associated increases in relative FFM (p = 0.45) or absolute LM (p = 0.87). There was no adaptation to LV morphology (p>0.05), however early diastolic function changed with a significant decrease in peak E wave (p = 0.00, d = 1.94). Study 3 compared differences in the time course of the initial adaptations to LV structure and function during 9 weeks of aerobic, resistance and combination exercise ii training, to establish whether LV adaptations are exercise specific. The resistance and combination groups demonstrated increases in relative wall thickness (p = 0.021, ηp2 = 0.408; p = 0.004, d = -1.06, respectively). PWd also significantly increased in the combination group (p = 0.032, ηp2 = 0.301); however there were no structural adaptations evident in the aerobic group (p > 0.05). In contrast, the aerobic group demonstrated functional adaptations with a decrease in A wave (p = 0.44, d = 0.87) as did the combination group (p = 0.002, ηp2 = 0.407). The results of the training studies showed limited support for the Morganroth Hypothesis as structural adaptations demonstrated LV remodelling of the myocardial tissue, with no increase in LV mass. Further to this, combination training appears to have an additive effect of LV adaptations of both aerobic and resistance training.

A computational model has been developed to study the effects of left ventricular assist devices (LVADs) on the cardiovascular system during a ventricular collapse. The model consists of a toroidal pulsatile blood pump and a closed loop circulatory system. Together, they predict the pump's motor current traces that reflect ventricular suck-down and provide insights into torque magnitudes that the pump experiences. In addition, the model investigates likeliness of a suction event and predicts reasonable outcomes for a few test cases. Ventricular collapse was modeled with the help of a mock circulatory loop consisting of a artificial left ventricle and centrifugal continuous flow pump. This study also investigates different suction detection schemes and proposes the most suitable suction detection algorithm for the TORVAD pump, toroidal left ventricular assist device. Model predictions were further compared against the data sampled during in vivo animal trials with the TORVAD system. The two sets of results are in good accordance. / text

Objective: The aim of this study was to determine the role of race as a significant risk factor for prediction of outcomes in heart failure (HF). Methods: The data was collected on demographics, detailed history of HF, family history, vital signs, medication and laboratory profile for 585 patients from Heart failure Treatment Center of Emory University after year of 2000. Outcome of HF was defined as combination of death, placement of left ventricular assisted devise, heart transplant or emergency transplant. The independent relationship between race and outcomes of HF was evaluated by univariate and multivariate logistic regression analyses. The survival analysis was done by Cox regression modeling. Results: Among 585 HF patients, 58.1% were whites and 41.9% were blacks and 28.2% HF patients had positive outcomes. Although Whites tended to have a more positive outcome (34.6%) than blacks (28.9%), the difference was not statistically significant. Factors predicting the outcome in whites were male gender (OR 5.02), history of hypertension (OR 2.3), ventricular arrhythmias (OR 2.4), placement of AICD(OR 0.09), low EF% (OR 0.95), high NYHA class (OR 3.25), use of beta blockers (OR 0.12), aldosterone blockers (OR 2.19), furosemide (2.18); while in blacks they were age in years (OR 0.96), history of PTCA (OR 7.04), dislipidemia (OR 3.90), depression (OR 0.01), placement of AICD (OR 0.14), low EF% (OR 0.92), systolic blood pressure (OR 0.96), high NYHA class (OR 4.01), use of beta blockers (OR 0.14), torsemide (OR 2.86), and digoxin (OR 4.91) etc. Blacks had higher survival than whites (p < 0.001). Conclusion: There is no significant difference in combined outcome (death, transplant, emergency transplant, and Left Ventricular Assisted Devise placement) of HF between whites and blacks. There are differences regarding the risk factors, which are more prominent in each race. Further exploration is required to evaluate the race as significant risk factor for predicting the outcome in HF.

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A left ventricular thrombus develops in approximately 40% of patients following an anterior myocardial infarction. Embolization from these thrombi has been regarded as the most important cause of stroke following a myocardial infarction. The occurrence and characteristics of left ventricular thrombi and stroke after anterior myocardial infarction may, however, have changed after the introduction of aspirin and thrombolytics as standard therapy. The occurrence of left ventricular thrombi was examined in 99 patients with an acute anterior myocardial infarction, 74 of whom were treated with streptokinase. Thrombi were equally common in the thrombolysis group (46%, 95% confidence interval [Cl], 35-57%) as in the non-thrombolysis group (40%, 95% Cl, 21-59%). The risk of thrombus formation was related to the degree of left ventricular segmental dysfunction. Using serial echocardiographic examinations, the formation and resolution of thrombi was found to be highly dynamic. The majority of thrombi diagnosed during the hospital stay had resolved at follow-up one month later, irrespective of treatment with streptokinase or anticoagulants. The development of new thrombi was, however, observed at every follow-up examination interval. One-hundred-and-twenty-four patients suffering a stroke within 28 days of an acute myocardial infarction were identified in the northern Sweden MONICA stroke registry between 1985 and 1994. The overall event rate of ischemic myocardial infarction-related stroke was 1.07%. The risk of a stroke was highest duringt he first 5 days after the infarction. Only approximately half the strokes were preceded by an anterior myocardial infarction. In a case-control analysis, atrial fibrillation (chronic or new onset), ST elevation and a history of a previous stroke were found to be independent predictors of stroke. There was a long-term trend towards a lower incidence and event rate for myocardial infarction-related stroke. Clinical stroke characteristics were examined in 103 patients with a first-ever stroke within 28 days of a myocardial infarction and compared with stroke characteristics in 206 control subjects without a recent myocardial infarction. The sudden onset of neurological symptoms, an impairment of consciousness, a progression in neurological deficits and a stroke of the total anterior circulation infarction subclass were more common in cases than in controls. The risk of a recurrent stroke during one year of follow-up was not influenced by a recent myocardial infarction, but patients who had suffered a myocardial infarction had markedly higher mortality. To conclude, thrombolytic treatment does not reduce the occurrence of left ventricular thrombi after a myocardial infarction. The risk of thrombus formation is related to the extent of the myocardial injury. The development and resolution of thrombi is a highly dynamic process. There is a long-term trend towards a lower incidence and event rate of ischemic stroke after a myocardial infarction. Although the clinical stroke characteristics differ, they are not specific enough to differentiate between patients with and without a recent myocardial infarction. / <p>S. 1-84: sammanfattning, s. 85-136: 5 uppsatser</p> / digitalisering@umu

Thesis (M.Sc.)--Memorial University of Newfoundland, Faculty of Medicine, 2001. / Typescript. Bibliography: leaves 95-112.