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Biomedical subjects

Hakan Arheden

Publications and source records attributed to Hakan Arheden.

7 recordsLinked to original sources
PubMed2006

Atrioventricular plane displacement is the major contributor to left ventricular pumping in healthy adults, athletes, and patients with dilated cardiomyopathy.

Previous studies using echocardiography in healthy subjects have reported conflicting data regarding the percentage of the stroke volume (SV) of the left ventricle (LV) resulting from longitudinal and radial function, respectively. Therefore, the aim was to quantify the percentage of SV explained by longitudinal atrioventricular plane displacement (AVPD) in controls, athletes, and patients with decreased LV function due to dilated cardiomyopathy (DCM). Twelve healthy subjects, 12 elite triathletes, and 12 patients with DCM and ejection fraction below 30% were examined by cine magnetic resonance imaging. AVPD and SV were measured in long- and short-axis images, respectively. The percentage of the SV explained by longitudinal function (SV(AVPD%)) was calculated as the mean epicardial area of the largest short-axis slices in end diastole multiplied by the AVPD and divided by the SV. SV was higher in athletes [140 +/- 4 ml (mean +/- SE), P = 0.009] and lower in patients (72 +/- 7 ml, P < 0.001) when compared with controls (116 +/- 6 ml). AVPD was similar in athletes (17 +/- 1 mm, P = 0.45) and lower in patients (7 +/- 1 mm, P < 0.001) when compared with controls (16 +/- 0 mm). SV(AVPD%) was similar both in athletes (57 +/- 2%, P = 0.51) and in patients (67 +/- 4%, P = 0.24) when compared with controls (60 +/- 2%). In conclusion, longitudinal AVPD is the primary contributor to LV pumping and accounts for approximately 60% of the SV. Although AVPD is less than half in patients with DCM when compared with controls and athletes, the contribution of AVPD to LV function is maintained, which can be explained by the larger short-axis area in DCM.

Adult↗
PubMed2005

Problem-based learning of research skills.

PURPOSE: To determine whether a short-term, problem-based educational intervention leads to increased research activity among health care practitioners. SUBJECTS AND METHODS: Participant's success was evaluated as a composite of 2 outcomes. These were (1) reporting results for the project designed during the practicum and (2) conducting subsequent research activities. The study population included 36 clinical research outcomes projects developed by clinical practitioners, postgraduate trainees, and medical students during 6 separate practicums. All project teams received the same educational intervention, an "outcomes research practicum" that was divided into 4 primary learning modules administered over a 1 to 4 month period. Each module included a preparatory videotape lecture, supplemental readings, and a 90-minute interactive laboratory session during which faculty members worked with participants to develop answers to a series of predefined questions relating to the design of clinical outcomes research projects. Follow-up continued for a minimum of 12 months and a maximum of 36 months. RESULTS: Eighty-three percent of project teams completed all 4 practicum modules, and 69% completed one of the study outcomes (50% completed their research project and 47% completing a subsequent research activity). Practitioners were more likely to complete subsequent research activities, whereas trainees were more likely to complete their study project. DISCUSSION: This short-term, problem-based educational intervention was successful in increasing the collective research activities of participants. Further, more rigorous structured research is needed to determine the ultimate impact on practice change and patient outcomes.

Education, Medical, Continuing↗
PubMed2005

Center of volume and total heart volume variation in healthy subjects and patients before and after coronary bypass surgery.

BACKGROUND: Total heart volume variation (THVV) and center of volume variation (COVV) likely affects the efficiency of cardiac pumping, but no study has determined COVV of the heart throughout the cardiac cycle or the effect of surgery on THVV in adults. Therefore, the purposes of this study were to determine COVV in healthy adults and patients with cardiac failure due to ischemic heart disease (IHD), identify any difference in THVV between these two groups, and determine how these parameters are affected by coronary bypass surgery. METHODS: Six healthy volunteers and eight patients before and after surgery were investigated with cardiovascular magnetic resonance imaging. The atrioventricular plane movement (AVPM), THVV and time resolved three-dimensional coordinates of the center of the cardiac volume (COVV) were measured. RESULTS: COVV followed a loop in 3D space that between the end-points was approximately 2 mm with no difference between healthy subjects and patients before surgery (P = 0.093), although AVPM was significantly lower in patients (P = 0.002). However, after surgery the COVV during the cardiac cycle doubled (P = 0.012) and the increase in THVV was significant (P = 0.050), although of very small magnitude, and the AVPM remained unchanged (P = 0.401). CONCLUSION: COVV and THVV were similar in patients and healthy subjects even though AVPM was lower in the patient population. After surgery, however, COVV doubled despite a very small change in THVV and no change in AVPM. Taken together, the results of this study may provide new insights into the energy expenditure and efficiency of cardiac pumping.

Adult↗
PubMed2005

Physiological determinants of the variation in left ventricular mass from early adolescence to late adulthood in healthy subjects.

BACKGROUND: The physiological determinants of left ventricular mass (LVM) measured by cardiac magnetic resonance (CMR) imaging are not well defined as prior investigators have studied either adults or adolescents in isolation or have not strictly excluded hypertension or accounted for the effects of exercise habits, haemodynamic, demographic, or body shape characteristics. METHODS: A total of 102 healthy volunteers (12-81 years, 53 males) underwent CMR. All parameters [unstandardized and adjusted for body surface area (BSA)] were analysed according to gender and by adolescence versus adulthood (adolescents <20 years, adults > or = 20 years). The influence of haemodynamic factors, exercise, and demographic factors on LVM were determined with multivariate linear regression. RESULTS: LVM rose during adolescence and declined in adulthood. LVM and LVMBSA were higher in males both in adults (LVM: 188 +/- 22 g versus 139 +/- 21 g, P < 0.001; LVMBSA: 94 +/- 11 g m(-2) versus 80 +/- 11 g m(-2), P < 0.001) and in adolescents when adjusted for BSA (LVM: 128 +/- 29 g versus 107 +/- 20 g, P = 0.063; LVMBSA: 82 +/- 8 g m(-2) versus 71 +/- 10 g m(-2), P = 0.025). In adults, systolic blood pressure (SBP) and self-reported physical activity increased while meridional and circumferential wall stress were constant with age. Multivariate regression analysis revealed age, gender, and BSA as the major determinants of LVM (global R2 = 0.69). CONCLUSIONS: Normal LVM shows variation over a broad age range in both genders with a rise in adolescence and subsequent decline with increasing age in adulthood despite an increase in SBP and physical activity. BSA, age, and gender were found to be major contributors to the variation in LVM in healthy adults, while haemodynamic factors, exercise, and wall stress were not.

Adolescent↗
PubMed2004

Total heart volume variation throughout the cardiac cycle in humans.

Variations in total heart volume (atria plus ventricles) during a cardiac cycle affect efficiency of cardiac pumping. The goals of this study were to confirm the presence, extent, and contributors of total heart volume variation during the cardiac cycle in healthy volunteers with the use of MRI. Eight healthy volunteers were examined by MRI at rest. Changes in total cardiac volume throughout the cardiac cycle were calculated using the following methods: 1) planimetry derived from gradient-echo cine images and 2) flow-sensitive sequences to quantify flow in all vessels leading to and from the heart. The maximum total heart volume diminished during systole by 8.2 +/- 0.8% (SEM, range 4.8-10.6%) measured by method 1 and 8.8 +/- 1.0% (SEM, range 5.6-11.8%) by method 2 with good agreement between the methods [difference according to Bland-Altman analysis -0.6% +/- 1.0% (SD), intraclass correlation coefficient = 0.999]. This decrease in volume is predominantly explained by variation at the midcardiac level at the widest diameter of the heart with a left-sided predominance. In the short axis of the heart, the change of slice volume was proportional to the end-diastolic slice volume. The present study has confirmed the presence of total heart volume variation that predominantly occurs in the region of atrioventricular plane movement and on the left side. The total heart volume variation may relate to the efficiency of energy use by the heart to minimize displacement of surrounding tissue while accounting for the energy required to draw blood into the atria during ventricular systole.

Adult↗