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Biomedical subjects

P K Paulsen

Publications and source records attributed to P K Paulsen.

At least 19 recordsLinked to original sources
PubMed2001

Energy stores and metabolites in chronic reversibly and irreversibly dysfunctional myocardium in humans.

OBJECTIVES: Our goal was to study metabolic energy stores and lactate content in chronic reversibly and irreversibly dysfunctional myocardium. BACKGROUND: It is unknown whether metabolism is deranged in chronic reversibly and irreversibly dysfunctional myocardium in humans. Semiquantitative histological examinations have shown altered mitochondrial morphology and glycogen accumulation in dysfunctional regions. METHODS: We studied 25 patients with a mean ejection fraction of 38 +/- 9% scheduled for coronary artery bypass surgery. Regional perfusion and metabolism were assessed by positron emission tomography, and regional function was assessed by echocardiography. Perioperative myocardial biopsies were obtained from a control region and from a dysfunctional region. We analyzed biopsies for contents of noncollagen protein (NCP), ATP, ADP, AMP, glycogen and lactate. Six months after surgery we assessed wall motion by echocardiography to group patients in those with (n = 11) and without (n = 14) functional improvement. RESULTS: Reversibly dysfunctional myocardium had reduced perfusion (0.59 +/- 0.16 vs. 0.69 +/- 0.20 ml/g/min, p < 0.05), similar glucose-tracer uptake (92 +/- 12 and 95 +/- 14%), ATP/ADP ratio (2.4 +/- 1.1 and 2.4 +/- 0.7), glycogen content (631 +/- 174 and 632 +/- 148 nmol/microg NCP) and lactate levels (59 +/- 27 and 52 +/- 29 nmol/microg NCP) compared with control regions. Irreversibly dysfunctional regions (n = 14) had severely reduced perfusion (0.48 +/- 0.15 vs. 0.72 +/- 0.12 ml/g/min, p < 0.001) and glucose-tracer uptake (52 +/- 16 vs. 94 +/- 15%, p < 0.001), reduced ATP/ADP ratio (1.5 +/- 0.9 vs. 2.3 +/- 0.9, p < 0.05), similar glycogen content (579 +/- 265 vs. 593 +/- 127 nmol/microg NCP) and increased lactate levels (114 +/- 52 vs. 89 +/- 24 nmol/microg NCP, p < 0.01) compared with control regions. CONCLUSIONS: Contents of metabolic energy stores and lactate in chronic reversibly dysfunctional myocardium were preserved. In contrast, energy stores were depleted in myocardium without functional recovery after revascularization.

Adenosine Diphosphate↗
PubMed2001

Heart motion-adapted MR velocity mapping of blood velocity distribution downstream of aortic valve prostheses: initial experience.

PURPOSE: To investigate blood flow velocities and shear rates at two distances downstream of an artificial aortic valve in patients. MATERIALS AND METHODS: Blood velocity was quantified downstream of the valve prosthesis (for replacement after aortic valve stenosis or combined stenosis and regurgitation) in 10 patients by using a magnetic resonance (MR) cine velocity mapping method in which the imaging section position is adapted according to the excursion of the valvular plane of the heart. Two acquisitions were performed to display the blood velocity distributions one-fourth valve diameter and one valve diameter downstream of the valve and to quantify blood volumes and shear rates. RESULTS: The velocity profiles measured during flow acceleration one-fourth valve diameter downstream were characterized by a distinct pattern of two lateral jets and one central jet of antegrade flow. High shear rates were found along the leaflet tips. The profiles obtained one valve diameter downstream were skewed, with varying velocity patterns among patients. Peak shear rates were found close to the vessel wall. With correction for through-plane motion of the valve, the mean apparent regurgitant fraction (+/- SD) was 14% +/- 6; the mean regurgitant fraction without correction was 9% +/- 5. CONCLUSION: The described noninvasive procedure for velocity mapping enables measurements close to the valve and thus evaluation of blood flow patterns with respect to valve design in humans.

Adult↗
PubMed2000

[DANAMI. A Danish study of invasive versus conservative treatment of patients with post-infarction ischemia who had received thrombolytic therapy].

INTRODUCTION: To compare an invasive strategy employing percutaneous transluminal coronary angioplasty (PTCA) or coronary artery by-pass grafting (CABG) with a medical strategy in patients who had received thrombolytic treatment for first acute myocardial infarction (AMI), and with signs of inducible ischaemia. METHODS: In a prospective study 1008 patients were randomized, 503 to invasive treatment, of whom 266 (52.9%) had PTCA, and 147 (29.2%) CABG, 505 to conservative treatment, of whom eight (1.6%) were revascularized within two months. RESULTS: After a median follow-up of 2.4 years the mortality in the invasive group was 3.6% vs. 4.4% (p = 0.45) in the conservative group, re-infarction incidence was 5.6% vs. 10.5% (p = 0.0038) and percentage of admissions with unstable angina was 17.9% vs. 29.5% (p < 0.00001). DISCUSSION: We conclude that post-infarct patients with inducible ischaemia should be referred to coronary angiography and revascularised accordingly.

Adult↗
PubMed2000

A new method for quantitative evaluation of perceived sounds from mechanical heart valve prostheses.

Closing clicks from mechanical heart valve prostheses are transmitted to the patient's inner ear mainly in two different ways: as acoustically transmitted sound waves, and as vibrations transmitted through bones and vessels. The purpose of this study was to develop a method for quantifying what patients perceive as sound from their mechanical heart valve prostheses via these two routes. In this study, 34 patients with implanted mechanical bileaflet aortic and mitral valves (St Jude Medical and On-X) were included. Measurements were performed in a specially designed sound insulated chamber equipped with microphones, accelerometers, preamplifiers and a loudspeaker. The closing sounds measured with an accelerometer on the patient's chest were delayed 400 ms, amplified and played back to the patient through the loudspeaker. The patient adjusted the feedback sound to the same level as the 'real-time' clicks he or she perceived directly from his or her valve. In this way the feedback sound energy includes both the air- and the bone-transmitted energies. Sound pressure levels (SPLs) were quantified both in dB(A) and in the loudness unit sone according to ISO 532B (the Zwicker method). The mean air-transmitted SPL measured close to the patient's ear was 23 +/- 4 dB(A). The mean air- and bone-transmitted sounds and vibrations were perceived by the patients as an SPL of 34 +/- 5 dB(A). There was no statistically significant difference in the perceived sound from the two investigated bileaflet valves, and no difference between aortic and mitral valves. The study showed that the presented feedback method is capable of quantifying the perceived sounds and vibrations from mechanical heart valves, if the patient's hearing is not too impaired. Patients with implanted mechanical heart valve prostheses seem to perceive the sound from their valve two to three times higher than nearby persons, because of the additional bone-transmitted vibrations.

Acoustics↗
PubMed1999

Development of velocity profiles and retrograde flow in the porcine abdominal aorta under different haemodynamic conditions.

Low and/or oscillating wall shear stresses are related to the development of atherosclerosis and this oscillation is influenced by changes in basic haemodynamics (exercise). The objective of this study was to provide in vivo data on the development of velocity profiles and oscillating blood velocities in the abdominal aorta under varying haemodynamic conditions. Six anaesthetized, 90-kg pigs were used in the study. Abdominal aortic velocity profiles across the anterior-posterior diameter were acquired at different axial positions using 10 MHz pulsed Doppler ultrasound. Measurements were obtained under normal conditions and during cardiac pacing up to 170 beats/min. Velocity profiles were obtained during heart rates ranging between 58 and 169 beats/min, and during flow rates ranging between 0.57 and 2.89 l/min. Main outcome measures included minimum velocities, frequency index, shape of velocity profiles (velocity distribution index), Reynolds' numbers, and Womersley's frequency parameter. Velocity profiles were blunted, with lowest velocities at the distal posterior vessel wall. Multiple regression analysis showed the development of velocity profiles to be inversely correlated with the pulsatility index, Womersley's frequency parameter and the mean Reynolds' number (r = 0.89, p < 0.0005). Minimum velocities were negatively correlated with the PI, Womersley's frequency parameter and positively with the mean Reynolds' number (r = 0.94, p < 10(-8)). Retrograde velocities (and hence oscillating wall shear stresses) were present at mean Reynolds' number < 1000. The oscillation of blood velocities at the wall in the porcine abdominal aorta was highly dependent on general haemodynamics (i.e. flow, heart rate and vessel diameter as expressed in the Reynolds' numbers and Womersley's frequency parameters). The velocity profiles in the abdominal aorta were found to be far from parabolic. These findings have important implications for the understanding and future modelling of the complex haemodynamics in the abdominal aorta and their relation to the development of atherosclerotic disease.

Animals↗
PubMed1999

High-frequency pressure fluctuations measured in heart valve patients.

BACKGROUND AND AIM OF THE STUDY: Due to the risk of thromboembolic complications, mechanical heart valve patients require life-long anticoagulant therapy, in contrast to bioprosthetic valves. The reason for this is still not fully understood. In vitro studies have demonstrated the presence of cavitation bubbles in the vicinity of mechanical heart valves, but not of bioprosthetic valves. When cavitation bubbles collapse, they release a significant amount of energy, which may damage the formed elements of the blood. A correlation between the presence of cavitation bubbles and high-frequency pressure oscillations has been established in vitro. Thus, the aim of this study was to measure and quantify high-frequency pressure oscillations in patients with normal, bioprosthetic or mechanical aortic valves. METHODS: Measurements were performed in six patients with normal aortic valves after coronary bypass surgery, in five patients fitted with a Carpentier-Edwards pericardial bioprosthesis, and in nine patients fitted with a St. Jude Medical or CarboMedics aortic valve. High-frequency pressure fluctuations were measured intraoperatively using a hydrophone placed near the aortic annulus. The root mean square (RMS) value of the high-frequency pressure signals were calculated in the frequency range 35-150 kHz. RESULTS: High-frequency pressure fluctuations, with intensities above the noise floor, were registered only in the vicinity of mechanical heart valve prostheses, and not in the vicinity of normal or bioprosthetic valves. The mean value of RMS pressure fluctuations was 0.5 Pa for normal aortic valves, 0.8 Pa for bioprosthetic valves, and 67 Pa for mechanical valves. CONCLUSIONS: This study is the first to show the presence of high-frequency pressure fluctuations in patients with mechanical valves.

Aged↗
PubMed1999

Assessment of perceived mechanical heart valve sound level in patients.

BACKGROUND AND AIM OF THE STUDY: When mechanical heart valves close, they generate an impulse that is transmitted to the patient's inner ear by two routes: (i) As acoustically transmitted sound waves; and (ii) as vibrations transmitted through bones and vessels. The aim of this study was to quantitate what patients perceive as sound from their mechanical heart valve prostheses - including both air-transmitted sound waves and bone-transmitted vibrations. METHODS: Thirty-four patients with implanted mechanical bileaflet aortic and mitral valves (St. Jude Medical and On-X) were included in the study. Measurements were performed in a specially designed sound-insulated chamber equipped with microphones, accelerometers, preamplifiers and a loud-speaker. The closing sounds measured by an accelerometer on the patient's chest were delayed 400 ms, amplified and played back to the patient through the loudspeaker. The patient adjusted the feedback sound to the same level as the 'real-time' clicks they perceived directly from their valve. In this way the feedback sound energy includes both the air- and bone-transmitted energies. Sound pressure levels (SPL) were quantitated in both dB(A) and in loudness units (sones) according to ISO 532B (Zwicker method). RESULTS: The mean air-transmitted SPL measured close to the patient's ear was 23 +/- 4 dB(A). The total air-and bone-transmitted sounds and vibrations were perceived by the patients as a SPL of 34 +/- 5 dB(A). There was no statistically significant difference in perceived sound from the two bileaflet valves investigated, and no difference between aortic and mitral valves. CONCLUSIONS: The study showed that the presented feedback method is capable of quantitating the perceived sounds and vibrations from mechanical heart valves, if the patient's hearing is not too impaired. Patients with implanted mechanical heart valve prostheses seem to perceive the sound from their valve two to four times higher than nearby persons, because of the additional bone-transmitted vibrations.

Adaptation, Psychological↗
PubMed1998

CABG shortly after AMI treated with thrombolysis: an analysis of the surgical group and a comparison with PTCA in the DANAMI study. Danish multicenter randomized study of invasive versus conservative treatment in patients with inducible ischemia after thrombolysis in acute myocardial infarction.

OBJECTIVE: To present surgical results of the DANAMI study comparing conservative and invasive treatment of postinfarction myocardial ischaemia and to compare these with percutaneous transluminal angioplasty (PTCA) which was the alternative invasive treatment in that study. METHODS: A group of 413 patients with verified acute myocardial infarction treated with thrombolysis within 12 h of the onset of symptoms, who demonstrated postinfarction myocardial ischaemia were treated with coronary artery bypass grafting (CABG) or PTCA. Patients with left main lesions, three-vessel disease, two-vessel disease with more than three stenoses and patients with occlusions of a non-infarct related vessel had primary CABG. Patients with 1- and 2-vessel disease with not more than a total of three stenoses had PTCA. In case of failed PTCA patients had secondary CABG. The median distance from AMI to CABG was 45 days. PTCA was performed at a mean of 39 days after the infarction. RESULTS: A total of 147 patients had CABG and 266 had PTCA. The operative mortality for CABG was 1.4%. No PTCA patients died in relation to the procedure, 0.8% developed acute myocardial infarction as a consequence of the procedure, 1.5% had acute CABG and 3.5% elective CABG due to failed PTCA. In spite of more severe coronary artery disease among the CABG patients there was no difference in survival at 2.4 years. The CABG group had significantly fewer episodes of unstable angina, 10.2% versus 25.6% (P = 0.0002). No CABG patients had re-do revascularisation at 2.4 years follow-up versus 15.4% of the PTCA patients. At 3 years 80% of the CABG patients were free of angina compared to the 61% of the PTCA group (P < 0.0001). CONCLUSION: Low morbidity and mortality justifies the deferred elective revascularisation in patients with postinfarction myocardial ischaemia even in patients with silent ischaemia. There is no difference in survival at 2.4 years between CABG and PTCA but CABG offers more lasting results concerning incidence of stable and unstable angina than PTCA, which, however, is a valuable alternative in patients with less severe coronary artery disease.

Adult↗
PubMed1998

The influence of propofol and midazolam/halothane anesthesia on hepatic SvO2 and gastric mucosal pH during cardiopulmonary bypass.

OBJECTIVE: Because propofol is known to reduce vascular resistance, the objective of this study was to compare the indices of hepatosplanchnic circulation and oxygenation during cardiopulmonary bypass (CPB) in patients anesthetized with either propofol or midazolam/halothane. DESIGN: A prospective, randomized, nonblinded study. SETTING: A university hospital. PARTICIPANTS: Twenty patients undergoing cardiac surgery with CPB. INTERVENTIONS: Nine patients were anesthetized with propofol/fentanyl/pancuronium and 11 patients were anesthetized with midazolam/halothane/fentanyl/pancuronium. All patients had a nasogastric tonometer tube and two fiberoptic thermodilution catheters inserted; one in the pulmonary artery and one in the upper right hepatic vein. During bypass, SvO2s were measured from the venous line of the heart-lung machine. MEASUREMENTS AND MAIN RESULTS: Gastric mucosal pH (pHi) was measured prebypass, 30 minutes after the start of CPB, and just before weaning off CPB. Hepatic SvO2 (HSvO2) values were recorded every 5 minutes. The pH gap was less at 30 minutes of hypothermic CPB in the propofol group. In the midazolam/halothane group, the HSvO2 decreased after the start of rewarming, whereas in the propofol group the values remained almost at the prebypass levels. At the end of rewarming, the HSvO2 was almost identical in the two groups. CONCLUSION: Propofol preserved the HSvO2 during CPB and produced a more optimal relationship between the hepatosplanchnic blood flow and oxygen consumption.

Adjuvants, Anesthesia↗
PubMed1998

Medtronic Hall versus St. Jude Medical mechanical aortic valve: downstream turbulences with respect to rotation in pigs.

BACKGROUND AND AIMS OF THE STUDY: Turbulences downstream of mechanical aortic valves are known to contribute to most valve-related complications such as thrombosis, embolization or damage to blood components. In vitro studies have demonstrated the impact of the orientation of prostheses on transvalvular energy loss. This study evaluates the influence of valve orientation on turbulences in the supravalvular aorta in pigs. METHODS: A rotation device which could carry a Medtronic Hall (MH) or St. Jude Medical (SJM) aortic valve prosthesis (23 mm) was constructed and implanted into four healthy pigs. Turbulence measurements using pulsed Doppler ultrasonography were carried out 3 cm downstream of the valve, while the prostheses were rotated in 45 degrees steps. Reynold's normal stress values (RNS) were calculated as key markers for turbulent stresses. RESULTS: Turbulences downstream of MH and SJM valves demonstrated a significant change with rotation. The MH valve showed minimum RNSmean values with orientation of the large orifice to the right posterior aortic wall, which is the area of highest velocities during ejection. With this orientation, aortic flow almost complied with physiologic conditions. Increase of turbulence was observed with any other position. The SJM valve revealed significant turbulent flow at any orientation. Minimum RNSmean values were also measured with one orifice facing the right posterior wall of the aorta. CONCLUSION: With optimum orientation (major orifice facing the right posterior aortic wall) the MH valve matches the aortic flow pattern to near-normal physiology. The flow patterns of the SJM valve are less susceptible to rotation, but cannot attain the optimum RNS values of the MH prosthesis.

Animals↗
PubMed1997

Danish multicenter randomized study of invasive versus conservative treatment in patients with inducible ischemia after thrombolysis in acute myocardial infarction (DANAMI). DANish trial in Acute Myocardial Infarction.

BACKGROUND: The aim of the DANish trial in Acute Myocardial Infarction (DANAMI) study was to compare an invasive strategy of percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG) with a conservative strategy in patients with inducible myocardial ischemia who received thrombolytic treatment for a first acute myocardial infarction (AMI). METHODS AND RESULTS: Of the 503 patients randomized to an invasive strategy, PTCA was performed in 266 (52.9%) and CABG in 147 (29.2%) from 2 to 10 weeks after the AMI. Of the 505 patients in the conservative treatment group, only 8 (1.6%) had been revascularized 2 months after the AMI. The patients were followed up from 1 to 4.5 years. The primary end points were mortality, reinfarction, and admission with unstable angina. At 2.4 years' follow-up (median), mortality was 3.6% in the invasive treatment group and 4.4% in the conservative treatment group (not significant). Invasive treatment was associated with a lower incidence of AMI (5.6% versus 10.5%; P=.0038) and a lower incidence of admission for unstable angina (17.9% versus 29.5%; P<.00001). The percentages of patients with a primary end point were 15.4% and 29.5% at 1 year, 23.5% and 36.6% at 2 years, and 31.7% versus 44.0% at 4 years (P=<.00001) in the invasive and conservative treatment groups, respectively. At 12 months, stable angina pectoris was present in 21% of patients in the invasive treatment group and 43% in the conservative treatment group. CONCLUSIONS: Invasive treatment in post-AMI patients with inducible ischemia results in a reduction in the incidence of reinfarction, fewer admissions due to unstable angina, and lower prevalence of stable angina. We conclude that patients with inducible ischemia before discharge who have received treatment with thrombolytic drugs for their first AMI should be referred to coronary arteriography and revascularized accordingly.

Adult↗
PubMed1997

New semiautomated Doppler method for quantification of volumetric flow: intraoperative validation with multiplane transesophageal color Doppler imaging.

We have validated a new semiautomated method for quantification of volumetric flow applied to multiplane transesophageal color Doppler mapping. This Doppler technique assumes only the incompressibility of the fluid and includes variations of flow area. By computing velocity vectors across a surface normal to the point of scanning, volumetric flow can be measured independently of the angle of incidence between the ultrasonic beam and the direction of blood flow. Mitral valvular flow rate was measured during surgery by transesophageal color Doppler echocardiography in 27 patients undergoing coronary artery bypass grafting at 45 sets of observations. The results were compared with those obtained by the thermodilution technique. The mean of the differences between the thermodilution technique and color Doppler echocardiography was 0.06 +/- 0.866 L/min for the mitral valvular flows (mean of differences [thermodilution-color Doppler] &/- 2 SDs of differences). Thus mitral valvular volumetric flow measured by this color Doppler method showed a close agreement to the thermodilution technique during surgery.

Blood Flow Velocity↗
PubMed1997

Wear patterns in the Sorin Bicarbon mechanical heart valve: a clinical explant study.

BACKGROUND AND AIMS OF THE STUDY: Mechanical heart valve prostheses are subject to wear due to impact and friction between the occluder(s) and valve housing. Reference data on the extent of wear in vivo is lacking. Therefore, the aim of this study was to describe the wear pattern in Sorin Bicarbon valves explanted from humans for comparison with the findings established in an earlier in vitro study. METHODS: We investigated eight valves explanted from seven patients, which had been functioning for more than six months and were returned to the Sorin Company for investigation. The protocol comprised: (i) initial visual inspection on receipt; (ii) stereomicroscopy after cleaning and disassembly; (iii) computed planimetry of the worn areas in the housing; (iv) pivot surface profilometry; and (v) scanning electron microscopy. RESULTS: All wear depths and exposed areas of titanium were less than that predicted from in vitro figures. No valves were explanted due to mechanical failure and none of the patients had reported peripheral embolic events which could be attributed to valve wear. The extent of wear was comparable with that of other valves. CONCLUSIONS: This descriptive study did not indicate any association between the Bicarbon valve wear characteristics and clinical complications. Clinical studies on valve performance are of paramount importance for elucidating this issue. The establishment of an independent body for studying explanted valves in collaboration with the manufacturers may promote the publication of findings which are of interest for the entire medical community.

Adult↗
PubMed1996

Validation of a new transit time ultrasound flowmeter in man.

OBJECTIVES: To validate the new CardioMed CM 4000 transit time ultrasound apparatus for intraoperative measurement of volume blood flow in vivo in man. DESIGN: Open, prospective series. MATERIALS: Thirteen patients undergoing in situ saphenous vein grafting for chronic critical leg ischaemia and 12 patients subjected to myocardial revascularisation with the internal thoracic artery as coronary bypass. METHODS: During operations, volume blood flows were measured simultaneously by exsanguination from the cut distal end of the in situ saphenous vein graft or the internal thoracic artery and by the transit time flowmeter equipment. In addition, the feasibility to detect arteriovenous fistula during in situ saphenous vein grafting was examined. RESULTS: Within the examined blood flow range, the volume blood flow determined by the transit time method corresponded to the directly measured blood flow. For in situ saphenous vein grafts: y = -2.4 + 0.95.x (r = 0.99; 35 measurements in 13 patients), and for internal thoracic artery grafts: y = -9.6 + 1.1.x (r = 0.99; 21 measurements in 12 patients), where y is blood flow determined by transit time, and x is directly measured blood flow by exsanguination (r = correlation coefficient) as calculated by the least squares regression method. Fistula detection was easy and swift. CONCLUSIONS: The transit time apparatus was simple to use during intraoperative settings and gave fast, precise measurements of volume blood flow.

Adult↗
PubMed1996

Magnetic resonance imaging of blood velocity distribution around St. Jude medical aortic valves in patients.

BACKGROUND AND AIMS OF THE STUDY: Complications after replacement of diseased heart valves with mechanical prostheses may be related to fluid dynamic disturbances. Magnetic resonance velocity mapping may allow quantitative, non-invasive, serial assessment of the blood velocity distribution around prosthetic heart valves in patients. MATERIAL AND METHODS: Velocity mapping was performed in six patients with aortic St. Jude Medical valves. Axial velocity components were measured at three positions near the valve and correlated with earlier in vitro results and with earlier invasive measurements. RESULTS: The velocity profiles downstream of the valve prostheses reflected the valve design and thus confirmed previous findings. In the one diameter downstream position blood flow velocities accelerated initially through the lateral orifices of the valve. Later in the acceleration phase the velocity profile became skewed and the antegrade velocity components increased in the part of the vessel corresponding to the central slit of the valve. Retrograde velocities occurred in part of the lateral orifice regions. CONCLUSIONS: MR velocity mapping provides valuable information on velocity fields around prosthetic bileaflet aortic valves. The velocity fields from the present study disclose qualitative similarity to those previously obtained. The present study, however, suggests a more skewed velocity profile than predicted from former studies. More extensive studies on larger patient groups should be performed, also with other valve types in order to establish a bank of reference data.

Adult↗