Biomedical subjects

Igor Knez

Publications and source records attributed to Igor Knez.

13 recordsLinked to original sources

PubMed2006

Influences of culture and environmental attitude on thermal, emotional and perceptual evaluations of a public square.

The main objective of the present quasi-experimental study was to examine the influence of culture (Swedish vs Japanese) and environmental attitude (urban vs open-air person) on participants' thermal, emotional and perceptual assessments of a square, within the PET (physiological equivalent temperature) comfortable interval of 18-23 degrees C. It was predicted that persons living in different cultures with different environmental attitudes would psychologically evaluate a square differently despite similar thermal conditions. Consistent with this prediction, Japanese participants estimated the current weather as warmer than did Swedish participants and, consistent with this, they felt less thermally comfortable on the site, although participants in both countries perceived similar comfortable thermal outdoor conditions according to the PET index. Compared to the Japanese, the Swedes estimated both the current weather and the site as windier and colder, indicating a consistency in weather assessment on calm-windy and warm-cold scales in participants in both cultures. Furthermore, Swedish participants felt more glad and calm on the site and, in line with their character (more glad than gloomy), they estimated the square as more beautiful and pleasant than did Japanese participants. All this indicates that thermal, emotional and perceptual assessments of a physical place may be intertwined with psychological schema-based and socio-cultural processes, rather than fixed by general thermal indices developed in line with physiological heat balance models. In consequence, this implies that thermal comfort indices may not be applicable in different cultural/climate zones without modifications, and that they may not be appropriate if we do not take into account the psychological processes involved in environmental assessment.

Adaptation, Physiological↗

PubMed2006

Invited commentary.

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Cardiac Surgical Procedures↗

PubMed2006

Autobiographical memories for places.

The purpose of the present exploratory study was to investigate operations and contents of a naturally occurring reminiscence for physical places in 26 Swedish participants. Using Conway and Pleydell-Pearce's (2000) model of autobiographical memory as a framework, two main questions were examined. First, in what sense are physical places ingredients of our selves-that is, of our self-knowledge-and, if so, how are they and their characteristics organised in the autobiographical knowledge base? Second, what form do personal memories for places take and what kinds of meanings and emotional contents do we bind to this type of reminiscence? The results showed that the Swedish participants' most important places in their lives were mainly childhood- and cottage-related rural types of milieus, and mostly categorised as summarised events; that is, frequently revisited. The personal recollections of the place-related event-specific knowledge were mostly of the generic imagery type, comprising semantic, perceptual, and emotional contents related to the "self", "others", and the "environment". The memories mainly reflected on the participants' growth period and feelings of activation and pleasantness. This was more pronounced in older (M = 59) than in younger (M = 35) participants. All this indicates that physical places can serve as thematic pathways guiding reminiscence and self-knowing consciousness as we recollect details of perceptual, semantic, and emotional characters of periods in our lives.

Adult↗

PubMed2005

Psychological impact of air velocity variations in a ventilated room.

Two experiments investigated the psychological impact of two velocity conditions (constant low velocity (V1) and variations of low and high velocity (V2)) in two temperature conditions (Experiment 1: an air temperature increase from 21 degrees C to 24 degrees C; Experiment 2: an air temperature increase from 25 degrees C to 27 degrees C) in females and males, aged 16 to 18 years, under realistic classroom conditions during an exposure period of 80 min. It was predicted that the V2 room condition compared to the V1 room condition would be more beneficial for subjects' perceived room temperature and air quality, self-reported affect and cognitive performance. The results obtained showed no significant effects on cognitive performance. However and as predicted, in Experiment 1, the subjects in the V2 compared to those in the V1 room condition felt that the air temperature decreased (while it de facto increased) and reported a constant level of high activation. In Experiment 2, the subjects in the V2 room condition felt that the air temperature increased less and reported that their unactivated unpleasantness increased less and activated pleasantness decreased less than it did for subjects in the V1 room condition. All this indicates, as was suggested by Wigö et al. (2002), that a cooling effect, induced by air velocity variations, might be beneficial for subjects in a ventilated room and that their perceived pleasantness of the indoor climate could be met at a higher room temperature than otherwise.

Adolescent↗

PubMed2005

Midterm results after aortic valve replacement with a stentless bioprosthesis aortic valve.

BACKGROUND: It is suggested that a simplified implant model Cryolife-O'Brien (CryoLife International, Kennesaw, GA) offers less satisfactory outcome compared with standard stentless models. This study was conducted to prospectively evaluate the midterm results after aortic valve replacement with the Cryolife-O'Brien stentless bioprosthesis. METHODS: In 1996, a prospective clinical trial using different stentless valves was initiated. From September 1996 through September 2002, 156 consecutive patients with a mean age of 74.5 years underwent aortic valve replacement with the Cryolife-O'Brien porcine stentless bioprosthesis. The predominant aortic valve lesion was stenosis in 128 and insufficiency in 28 cases. Patients have been followed from 2 to 72 months (mean, 42 months). Echocardiography was performed by one echocardiographer preoperatively, intraoperatively, postoperatively at discharge, 2 to 6 months later, and annually thereafter. RESULTS: Sixty percent of patients received a valve 25 mm in diameter or larger; 39% had concomittant coronary bypass grafting. The 30-day operative mortality rate was 6.4%. Ten late nonvalve-related deaths have occurred. Severe aortic insufficiency caused by oversizing leads to early reoperation in 3 patients. The peak and mean systolic gradients decreased significantly during the first 12 months after implantation, p < 0.001, and the effective valve areas increased significantly during this time interval p < 0.001. At 5 years, ten patients have moderate aortic insufficiency. The actuarial survival at 5 years was 88 +/- 3%. The rate for freedom from endocarditis was 100% and for freedom from thromboembolic events was 94%. CONCLUSIONS: Midterm results after aortic valve replacement with the Cryolife-O'Brien stentless bioprosthesis are encouraging. Good hemodynamics have been coupled with low rate of valve-related complications, thus representing a very good alternative to conventional stented bioprostheses.

Aged↗

PubMed2005

Eight-year results after aortic valve replacement with the CryoLife-O'Brien Stentless Aortic Porcine Bioprosthesis.

OBJECTIVE: The long-term durability and hemodynamics of stentless valves are largely unknown. In this study we prospectively analyzed 8-year clinical results with the CryoLife-O'Brien Stentless Aortic Porcine Bioprosthesis (CryoLife Inc, Kennesaw, Ga) and assessed its hemodynamic performance by serial echocardiography. METHODS: A total of 206 patients with a mean age of 72.8 years were followed up prospectively after aortic valve replacement with the CryoLife-O'Brien stentless bioprosthesis. Patients have been followed up from 2 to 96 months for mean 56 months. Echocardiography was performed by a single echocardiographer preoperatively, intraoperatively, postoperatively at discharge, 3 to 6 months later, and annually thereafter. RESULTS: The 30-day operative mortality was 4.8%. Sixty-five percent of patients received a valve 25 mm in diameter or larger, and 37% underwent concomitant coronary bypass grafting. Twelve late deaths, none valve-related, have occurred. Severe aortic insufficiency caused by oversizing led to early reoperation in 3 patients. The peak and mean systolic gradients decreased significantly during the first 12 months after implantation (P < .001), and the effective valve areas increased significantly during this interval (P < .001). At 8 years, 2 patients have mild to moderate aortic insufficiency. The actuarial survival at 8 years was 82% +/- 3%. The freedom from endocarditis was 100%, and the freedom from thromboembolic events was 93%. CONCLUSION: Despite more demanding surgical technique than with conventional bioprostheses, the CryoLife-O'Brien bioprosthesis can be implanted safely in a population predominantly older than 70 years at the time of the operation, with excellent measures of hemodynamics, clinical outcomes, prosthesis durability, and survival through 8 years.

Aged↗

PubMed2003

Mitral annuloplasty in patients with ischemic versus dilated cardiomyopathy.

OBJECTIVE: Mitral regurgitation is a frequent finding in patients with end-stage cardiomyopathy predicting poor survival. Conventional treatment consists medical treatment or cardiac transplantation. However, despite severely decreased left ventricular function, mitral annuloplasty may improve survival and reduce the need for allografts. METHODS: From January 1996 to July 2002, 121 patients with severe end-stage dilated (DCM) or ischemic cardiomyopathy (ICM), mitral regurgitation > or =2, and left ventricular ejection fraction < or =30% underwent mitral valve annuloplasty using a flexible posterior ring. DCM was diagnosed in 30 patients (25%), whereas ICM was found in 91 patients (75%). Concomitant tricuspid valve repair was performed in 14 (46.6%) patients in the DCM, and in 11 (12%) in the ICM group (P=0.0001), coronary artery bypass grafting in three (10%) in the DCM, and in 78 patients (86%) in the ICM group (P<0.00001). The mean follow-up time was 567+/-74 days in the DCM and 793+/-63 days in the ICM group (ns). RESULTS: Early mortality was 6.6% (8/121), and was equal for both groups. Improvement in NYHA class (DCM 3.3+0.1-1.8+/-0.16; ICM from 3.2+0.04 to 1.7+/-0.07) were equal between groups after 1 year. Seventeen (15%) late deaths occurred during the follow-up period. There was no difference in the 2-year actuarial survival between groups (DCM/ICM 0.93/0.85). Risk factors for mitral reconstruction failure, defined as regurgitation > or =2 after 1 year, were preoperative NYHA IV in the DCM group (P=0.03), a preoperative posterior infarction (P=0.025), decreased left ventricular function (P=0.043), larger ring size (P=0.026) and preoperative renal failure (P=0.05) in the ICM group. Risk factors for death were larger ring size (P=0.02) and an increased LVEDD (P=0.027) in the DCM group and the postoperative use of IABP (P=0.002), renal failure (P=0.001), and a larger preoperative LVESD (P=0.035) in the ICM group. CONCLUSION: Mitral reconstruction with a posterior annuloplasty using a flexible ring is effective in patients with severely depressed left ventricle function and has an acceptable operative mortality. Mid-term results are superior to medical treatment alone and comparable to cardiac transplantation.

Aged↗

PubMed2003

Partial liquid ventilation combined with two different gas ventilatory strategies in acute lung injury in piglets: Effects on gas exchange, respiratory mechanics, and hemodynamics.

BACKGROUND/PURPOSE: Partial liquid ventilation (PLV) has been shown to improve oxygenation and lung mechanics in different models of acute lung injury. This study was designed to investigate the effects of 2 gas ventilatory strategies during PLV on gas exchange, respiratory mechanics, and hemodynamics in acute lung injury in piglets. METHODS: After induction of acute lung injury, the animals were assigned randomly to 2 groups with different positive end-expiratory pressure (PEEP) levels and tidal volumes (Vt) (group A, Vt > 12.5 mL/kg; PEEP = 6 cm H2O, n = 7; group B, Vt < 9 mL/kg, PEEP = 12 cm H2O, n = 7). Thereafter, the perfluorocarbon (PFC) liquid (30 mL/kg) was instilled into the endotracheal tube. Cardiorespiratory parameters were measured at baseline, after induction of acute lung injury, and every 30 minutes up to 120 minutes. RESULTS: During PLV, oxygenation significantly improved with no difference between both gas ventilatory strategies. The high PEEP-moderate Vt gas ventilatory strategy reduced the inspiratory airway resistance and was associated with moderate hypercapnia. There were no significant differences in hemodynamics and respiratory compliance between both gas ventilatory strategies. CONCLUSIONS: The results of this pilot study suggest that oxygenation was equally improved during PLV. This effect was independent of the mode of gas ventilation. However, the high PEEP-moderate Vt gas ventilatory technique resulted in moderate hypercapnia.

Acute Disease↗

PubMed2003

Angiotensin-converting enzyme polymorphisms and their potential impact on left ventricular myocardial geometry after aortic valve surgery.

BACKGROUND AND AIM OF THE STUDY: Genetic variants of the angiotensin-converting enzyme (ACE) cascade may influence left ventricular myocardial mass (LVMM) regression after aortic valve surgery. Postoperative long-term changes in LV indices were investigated in patients with asymptomatic aortic regurgitation (AR) and symptomatic aortic stenosis (AS) and related to alleles of ACE polymorphisms. METHODS: A total of 96 patients was included in the study, 21 with class IIa AR (22%) and 75 with class I AS (78%) recommendations for surgery. Patients were evaluated for demographic risk factors and underwent a thorough clinical examination including 3-D cardiac imaging by ultrafast-computed tomography. Genomic DNA was isolated for genotyping. RESULTS: AR patients were younger (55.8 +/- 8.9 versus 64 +/- 9.1 years, p = 0.0014), had a larger body surface area (1.92 +/- 0.21 versus 1.82 +/- 0.19 m2, p = 0.039), and were more likely to be asymptomatic (myocardial infarction, p = 0.04; syncope, p = 0.0099; thromboembolism, p = 0.03; NYHA class IV, p = 0.04). Postoperatively, the reduction in absolute LVMM (from 297.1 +/- 52.6 to 190.1 +/- 57.1 g versus 214.4 +/- 55.7 to 143.8 +/- 40.0 g; pT = 0.0000001) and indexed LVMM (from 156.0 +/- 31.7 to 99.3 +/- 28.4 g/m2 versus 118.7 +/- 28.3 to 79.3 +/- 20.6 g/m; pT = 0.0000001) over time was more significant in AR patients, but never reached normal values. Enforced ACE inhibitor medication resulted in significantly higher postoperative indexed LVMM differences in homozygote DD patients compared to AR patients with II/ID alleles of ACE 16 ins/del polymorphism. CONCLUSION: AR patients showed a statistically significant decrease in absolute/indexed LVMM during follow up, but never achieved LV mass recovery compared to standard values or to values in patients undergoing aortic valve replacement for AS. The benefits of ACE inhibitors were observed among AR patients with homozygote DD alleles of ACE 16 ins/del polymorphism.

Aged↗

PubMed2002

Late dissection of the ascending aorta after previous cardiac surgery: risk, presentation and outcome.

OBJECTIVE: Aortic dissection is a potentially life-threatening condition and may follow surgical interventions as a complication with distinct presentation and high mortality. Information on the incidence and etiology of aortic dissections following cardiac surgery is sparse and inconsistent. The true incidence of this entity may so far have been underestimated. METHODS: Data of 223 operations on the thoracic aorta performed exclusively at our institution between January 1990 and May 2001 were analysed for clinical and prognostic features. Patients with Marfan syndrome and traumatic cases were not included. Cases of type A aortic dissection following cardiac surgery were investigated further. RESULTS: Dissection of the ascending aorta occurred in 83 patients, of whom 11 (13.2%, six acute and five chronic) had undergone previous cardiac surgery (four aortic valve replacements (AVR), two double valve replacements (DVR), two AVR+coronary artery bypass grafts (CABG), three CABGs). The time interval between first operation and dissection was 0.2-17 years (median 3.3 years). Eight (72%) patients had arterial hypertension. The aortic diameter was >or=50mm in all 11 cases upon presentation. Dissections were treated with Bentall procedures (3), Cabrol procedure (1), supracoronary tube graft (6) including concomitant CABG (3) and AVR with local repair (1). Total in-hospital mortality was 54% (6/11), and 66% (4/6) in cases with acute dissection due to low cardiac output (3) and myocardial infarction (3). CONCLUSIONS: Type-A aortic dissection can follow cardiac operations at any time with no typical interval or associated histology and with high overall hospital mortality. Male patients with arterial hypertension are at increased risk. Clinical presentation may differ from primary dissection with implications for management and risk estimation.

Aged↗

PubMed2002

Changes in the current approach do not qualify prosthesis-patient mismatch either (reply to Dumesnil et al., EJCTS 2002;21:157-158).

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Heart Valve Prosthesis↗

PubMed2002

Partial liquid ventilation versus conventional mechanical ventilation with high PEEP and moderate tidal volume in acute respiratory failure in piglets.

This prospective randomized pilot study aimed to test the hypotheses that partial liquid ventilation combined with a high positive end-expiratory pressure (PEEP) and a moderate tidal volume results in improved gas exchange and lung mechanics without negative hemodynamic influences compared with conventional mechanical ventilation in acute lung injury in piglets. Acute lung injury was induced in 12 piglets weighing 9.0 +/- 2.4 kg by repeated i.v. injections of oleic acid and repeated lung lavages. Thereafter, the animals were randomly assigned either to partial liquid ventilation (n = 6) or conventional mechanical ventilation (n = 6) at a fractional concentration of inspired O(2) of 1.0, a PEEP of 1.2 kPa, a tidal volume < 10 mL/kg body weight (bw), a respiratory rate of 24 breaths/min, and an inspiratory/expiratory ratio of 1:2. Perfluorocarbon liquid 30 mL/kg bw was instilled into the endotracheal tube over 10 min followed by 5 mL/kg bw/h. Continuous monitoring included ECG, mean right atrial, pulmonary artery, pulmonary capillary, and arterial pressures, arterial blood gas, and partial pressure of end-tidal CO(2) measurements. When compared with control animals, partial liquid ventilation resulted in significantly better oxygenation with improved cardiac output and oxygen delivery. Dead space ventilation appeared to be lower during partial liquid ventilation compared with conventional mechanical ventilation. No significant differences were observed in airway pressures, pulmonary compliance, and airway resistance between both groups. The results of this pilot study suggest that partial liquid ventilation combined with high PEEP and moderate tidal volume improves oxygenation, dead space ventilation, cardiac output, and oxygen delivery compared with conventional mechanical ventilation in acute lung injury in piglets but has no significant influence on lung mechanics.

Acute Disease↗

PubMedDate not supplied

Predictors of failure to cure atrial fibrillation with the mini-maze operation.

BACKGROUND: Maze-III is a complex surgical procedure designed to treat chronic atrial fibrillation. A reduction in the number of right and left atrial incisions could decrease the operative time. The aim of this study was to assess the results of a mini-maze operation and to define predictors of its failure. METHODS: Between 1995 and 2000, 72 patients (mean age 64 +/- 9 years) undergoing cardiac surgery had a concomitant mini-maze operation for symptomatic chronic atrial fibrillation. Three and 12 months post-operatively, heart rhythm and left atrial transport functions were assessed by electrophysiology, echocardiography, and magnetic resonance imaging. Multivariate analysis was performed to identify predictors of failure of the mini-maze operation. RESULTS: Operative mortality was 1.4% (1/72). Death during follow-up occurred in 5.6% of patients (4/71), in one due to chronic heart failure. After 1 year, 80% of patients (48/60) were either in sinus rhythm (n = 43; 72%) or had a pacemaker (n = 5; 8%) implanted due to sick sinus syndrome. Intermittent and chronic atrial fibrillation was found in 20% of patients (12/60). Preoperative duration of atrial fibrillation (p = 0.05), preoperative left atrial diameter (p = 0.001), preoperative right atrial diameter (p = 0.02), a reduced left ventricular ejection fraction (p = 0.03), an increased left ventricular end-diastolic diameter (p = 0.04), and the presence of mitral valve stenosis (p = 0.001) were found to be univariate predictors of failure of the mini-maze operation 1 year postoperatively. Multivariate analysis defined preoperative diagnosis of mitral valve stenosis (p = 0.005; OR 117.5), longer duration of preoperative atrial fibrillation (p = 0.01; OR 1.33), and increased preoperative left ventricular end-systolic diameter (p = 0.02; OR 1.2) as incremental independent risk factors for failure of the mini-maze operation to cure chronic atrial fibrillation. CONCLUSION: The mini-maze operation is a safe procedure with similar results to that of Cox's Maze-III operation. The less-invasive mini-maze operation could be applicable even to patients with severely reduced left ventricular function, in whom complex cardiac surgery has to be performed concomitantly as well as in those presenting severe comorbidities.

Adult↗