Plastic surgery in the Norwegian undergraduate medical curriculum: students' knowledge and attitudes. A nationwide case-control study.

OBJECTIVE: Changes in medical education have resulted in less available time for plastic surgery, which might jeopardise the availability of plastic surgery for patients. The aims of this study were to investigate the level of knowledge within and attitudes towards plastic surgery among medical students, and find predictors for a wish to pursue a career in plastic surgery. METHODS: A previously used questionnaire was sent to all clinical medical students. Law students were used as a control group. RESULTS: Thirty per cent of all clinical medical students in the country responded. The majority of students considered education in plastic surgery valuable/very valuable and 23% were considering it as a career. Nonetheless, about half of the students were unaware of the plastic surgical education at their faculty and reported non-academic sources of learning. Only 44% of medical students were able to name five common plastic surgical procedures and 8% were unable to name any. Law students were superior to medical students in the task (p = 0.005). Forty-two per cent of medical students were successful in indicating on which body parts plastic surgeons operate, whereas law students were less successful (p = 0.001). Male gender and positive valuing of clinical attachment could predict a wish for a career in plastic surgery. CONCLUSION: In some aspects, medical students are only as knowledgeable as their non-medical peers. These results call for higher quality plastic surgery teaching, to secure referral of the correct patients and successful specialist recruitment to plastic surgery.

Can spectral-spatial image segmentation be used to discriminate experimental burn wounds?

Hyperspectral imaging (HSI) is a noncontact and noninvasive optical modality emerging the field of medical research. The goal of this study was to determine the ability of HSI and image segmentation to discriminate burn wounds in a preclinical porcine model. A heated brass rod was used to introduce burn wounds of graded severity in a pig model and a sequence of hyperspectral data was recorded up to 8-h postinjury. The hyperspectral images were processed by an unsupervised spectral­spatial segmentation algorithm. Segmentation was validated using results from histology. The proposed algorithm was compared to K-means segmentation and was found superior. The obtained segmentation maps revealed separated zones within the burn sites, indicating a variation in burn severity. The suggested image-processing scheme allowed mapping dynamic changes of spectral properties within the burn wounds over time. The results of this study indicate that unsupervised spectral­spatial segmentation applied on hyperspectral images can discriminate burn injuries of varying severity.

Effect of the degree of LAD stenosis on "competitive flow" and flow field characteristics in LIMA-to-LAD bypass surgery.

The long-term patency of the left internal mammary artery (LIMA) in left anterior descending (LAD) coronary stenosis bypass surgery is believed to be related to the degree of competitive flow between the LAD and LIMA. To investigate the effect of the LAD stenosis severity on this phenomenon and on haemodynamics in the LIMA and anastomosis region, a numerical LIMA-LAD model was developed based on 3D geometric (obtained from a cast) and hemodynamic data from an experimental pig study. Proximal LAD pressure was used as upstream boundary condition. The model counted 13 outlets (12 septal arteries and the distal LAD) where flow velocities were imposed in systole, while myocardial conductance was imposed in diastole via an implicit scheme. LAD stenoses of 100 (total occlusion), 90, 75 and 0 % area reduction were constructed. Low degree of LAD stenosis was associated with highly competitive flow and low wall shear stress (WSS) in the LIMA, an unfavourable hemodynamic regime which might contribute to WSS-related remodelling of the LIMA and suboptimal long-term LIMA bypass performance.

A dose-response study of levosimendan in a porcine model of acute ischaemic heart failure.

OBJECTIVES: Levosimendan is a novel inotropic agent claimed to improve myocardial contractility by a calcium-sensitizing effect. Our aim was to evaluate dose-dependent effects of levosimendan on left ventricular (LV) contractility and energetic properties in an acute, ischaemic heart failure porcine model. METHODS: Six pigs were used in an anaesthetized in vivo open-chest model. The time points of measurements were: baseline, after heart failure induction and after dose 1-4 (D1-D4). Heart failure was induced by microembolization of the left coronary artery before infusion of four different doses (D1: 2.5 µg/kg, D2: 10 µg/kg, D3: 40 µg/kg, D4: 80 µg/kg) of levosimendan. Haemodynamics were assessed by the pressure-conductance catheter technique. LV oxygen consumption was calculated from coronary flow measurements and coronary sinus blood gases. Mitochondrial respiration was studied in biopsies of the LV. RESULTS: Levosimendan had no significant, load-independent effect on contractile force (slope of preload recruitable stroke work was 34 mmHg immediately following failure and 39 (P = 0.406), 42 (P = 0.219), 46 (P = 0.067) and 41 (P = 0.267) at D1-D4), although the more load-dependent contractility indicator of dP/dt(max) was slightly increased at dose 4 (P < 0.05). LV energy conversion efficiency (PVA-MVO2 relationship) remained unaltered at all doses. Maximal mitochondrial respiration decreased after induction of failure and remained at an unaltered low level during levosimendan infusion. CONCLUSIONS: Surprisingly, levosimendan had no significant effect on contractility, energy efficiency and mitochondrial respiration of the LV, in a porcine model of acute heart failure. At high doses, levosimendan induced vasodilatation and increased heart rate and cardiac output.

Impact of competitive flow on wall shear stress in coronary surgery: computational fluid dynamics of a LIMA-LAD model.

AIMS: Competitive flow from native coronary vessels is considered a major factor in the failure of coronary bypass grafts. However, the pathophysiological effects are not fully understood. Low and oscillatory wall shear stress (WSS) is known to induce endothelial dysfunction and vascular disease, like atherosclerosis and intimal hyperplasia. The aim was to investigate the impact of competitive flow on WSS in mammary artery bypass grafts. METHODS AND RESULTS: Using computational fluid dynamics, WSS was calculated in a left internal mammary artery (LIMA) graft to the left anterior descending artery in a three-dimensional in vivo porcine coronary artery bypass graft model. The following conditions were investigated: high competitive flow (non-significant coronary lesion), partial competitive flow (significant coronary lesion), and no competitive flow (totally occluded coronary vessel). Time-averaged WSS of LIMA at high, partial, and no competitive flow were 0.3-0.6, 0.6-3.0, and 0.9-3.0 Pa, respectively. Further, oscillatory WSS quantified as the oscillatory shear index (OSI) ranged from (maximum OSI = 0.5 equals zero net WSS) 0.15 to 0.35, <0.05, and <0.05, respectively. Thus, high competitive flow resulted in substantial oscillatory and low WSS. Moderate competitive flow resulted in WSS and OSI similar to the no competitive flow condition. CONCLUSION: Graft flow is highly dependent on the degree of competitive flow. High competitive flow was found to produce unfavourable WSS consistent with endothelial dysfunction and subsequent graft narrowing and failure. Partial competitive flow, however, may be better tolerated as it was found to be similar to the ideal condition of no competitive flow.

Pulsatility index variations using two different transit-time flowmeters in coronary artery bypass surgery.

OBJECTIVE: Transit-time flow measurement is widely accepted as an intra-operative assessment in coronary artery bypass grafting (CABG). However, the two most commonly applied flowmeters, manufactured by MediStim ASA and Transonic Inc., have different default filter settings of 20 and 10 Hz, respectively. This may cause different flow measurements, which will influence the reported results. The aim was to compare pulsatility index (PI) values recorded by the MediStim and Transonic flowmeters in two different clinical settings: (1) analysis of the flow patterns recorded simultaneously by both flowmeters in the same CABGs; and (2) evaluation of flow patterns under different levels of filter settings in the same grafts. METHODS: Graft flow and PI were measured using the two different flowmeters simultaneously in 19 bypass grafts. Finally, eight grafts were assessed under different digital filter settings at 5, 10, 20, 30, 50 and 100 Hz. RESULTS: The Transonic flowmeter provided substantially lower PI as compared with the MediStim flowmeter. By increasing the filter setting in the flowmeter, PI increased considerably. CONCLUSIONS: The Transonic flowmeter displayed a lower PI than the MediStim, due to a lower filter setting. In the Transonic,flow signals are filtered at a lower level, rendering a 'smoother' pattern of flow curves. Because different filter settings determine different PIs, caution must be taken when flow values and flowmeters are compared. The type of flowmeter should be indicated whenever graft flow measurements and derived indexes are provided [corrected].

Different graft flow patterns due to competitive flow or stenosis in the coronary anastomosis assessed by transit-time flowmetry in a porcine model.

OBJECTIVE: To assess whether coronary graft flow patterns are affected differently by native coronary competitive flow or by stenosis of the coronary anastomosis. METHODS: Nine pigs (65-70 kg) underwent off-pump grafting of the left internal mammary artery to the left anterior descending artery (LAD). Transit-time flow patterns in the mammary grafts were recorded under four different conditions: (1) baseline flow (proximal LAD occluded), (2) full competitive flow, (3) partial competitive flow and (4) after creation of a stenosis in the anastomosis. Competitive flow was achieved by an adjustable occluder on the left anterior descending artery. The mean luminal stenosis of the anastomosis was 75+/-11%, calculated by epicardial ultrasound. Mean flow, systolic and diastolic antegrade and retrograde flow during different flow conditions were calculated as ratios of baseline flow and compared. Different derived flow indexes were calculated and compared in the same manner. Friedman's test and post hoc analyses by Wilcoxon signed-ranks were performed without correction for multiple comparisons. RESULTS: Mean graft flow was more reduced by competitive flow than by a stenotic anastomosis of 75+/-11%. Competitive flow significantly decreased diastolic antegrade flow and both diastolic and systolic maximum peak flows, but increased retrograde flow, compared with baseline and stenosis. Furthermore, competitive flow and stenosis could be distinguished by analysis of several derived indexes. Pulsatility index (maximum-minimum flow/mean flow) and insufficiency percent (retrograde flow as fraction of total flow) was increased significantly more by competitive flow than by stenosis. Diastolic filling percent was significantly reduced at competitive flow compared with stenosis and baseline. CONCLUSIONS: The mammary graft flow was significantly reduced by native coronary competitive flow, but marginally decreased by a stenotic anastomosis of 75% mean luminal stenosis. Reduction of graft flow due to competition was particularly evident in diastole. A detailed flow pattern analysis may differentiate between competitive flow and stenosis of the anastomosis.

Transit-time blood flow measurements in sequential saphenous coronary artery bypass grafts.

BACKGROUND: Little information is available on transit-time flow measurements of sequential saphenous vein grafts. The aim of the study was evaluation of mean blood flow and pulsatility index of sequential saphenous vein grafts in a large population of patients operated on with coronary artery bypass grafting. METHODS: In 581 patients 1,390 grafts were nested into left internal mammary artery to left anterior descending artery, single vein grafts, or double and triple sequential vein grafts, and analyzed. RESULTS: Within the single vein graft group there were no differences between flow of grafts to different target vessels except for diagonals (diagonal versus obtuse marginal, p < 0.001; versus posterior descending artery, p = 0.035; versus right coronary artery, p = 0.003). Flows measured in single vein grafts were significantly lower than in double (p < 0.001) and triple sequential vein grafts (p < 0.001). Flows were lower in double versus triple sequential vein grafts (p = 0.017) and higher in men versus women (p < 0.001). Mean pulsatility index of vein grafts were lower in the left versus the right coronary system, 2.0 +/- 0.01 and 2.4 +/- 0.06, respectively (p < 0.001). Between sex and groups of vein grafts within each coronary system, mean pulsatility index had similar values. CONCLUSIONS: Blood flow increases from single to double and up to triple sequential grafts. Single grafts directed to diagonals have the lowest flow. Graft blood flows are higher in male versus female patients. Single, double, and triple saphenous vein grafts have similar pulsatility indexes. Pulsatility index of grafts to the right coronary system is significantly higher than that of grafts to the left coronary system.