Biomedical subjects

S Aakhus

Publications and source records attributed to S Aakhus.

At least 37 records · Page 2Linked to original sources

PubMed1995

Digital high frame rate stress echocardiography for detection of coronary artery stenosis by high dose dipyridamole stress testing.

Diagnostic accuracy of high dose dipyridamole stress echocardiography (0.84 mg i.v./kg) for detecting coronary artery stenosis was assessed in 94 patients undergoing coronary angiography, and adverse effects were registered in the total study population of 120 patients. Echocardiographic analysis was performed with digital systolic cineloops with high frame-rate (47 frames/sec) for optimal left ventricular wall motion display. Results showed sensitivity of 73% for detection of arterial luminal stenosis > or = 75% or retrograde collateral flow to an occluded coronary artery. Sensitivity for detection of 1-vessel stenosis was 43% (6 of 14 patients), and for 2- and 3-vessel disease 79% (19 of 24) and 88% (16 of 18), respectively. Specificity was 92% (35 of 38), diagnostic accuracy 81%. The stenosed coronary artery was correctly localized in 85% of positive tests. Dipyridamole-induced increase in wall motion score index differed significantly between patients with 1-, 2-, and 3-vessel disease (0.02 +/- 0.17, 0.15 +/- 0.17, and 0.27 +/- 0.24, respectively), and early positive tests (dipyridamole dose of 0.56 mg/kg) were almost exclusively seen in patients with multivessel disease. Six patients (5%) developed symptomatic bradycardia and hypotension during the test. In conclusion, dipyridamole stress echocardiography is useful for detection and localization of coronary artery stenosis, particularly in patients with multivessel disease.

Collateral Circulation↗

PubMed1995

Increased left ventricular contractility during cross-clamping of the descending thoracic aorta.

OBJECTIVE: To evaluate how left ventricular (LV) dimensions and contractility and proximal systemic hemodynamics respond during and after 30 minutes of cross-clamping of the descending thoracic aorta. DESIGN: The study was prospective and controlled. SETTING: The study was performed in a university animal laboratory. PARTICIPANTS: Ten pigs (bodyweight: 22 to 30 kg). INTERVENTIONS: The pigs were anesthetized with fentanyl and ketamine, and the heart and aorta were exposed through a left thoracotomy. The aortic root pressure and flow and LV dimensions were monitored with a high-fidelity pressure catheter, a precalibrated ultrasonic transit-time flow probe, and by two-dimensional ultrasound imaging, respectively. MEASUREMENTS AND MAIN RESULTS: After 1 minute of cross-clamping, LV end-diastolic and end-systolic diameters were increased 17% and 32% above baseline (both p < 0.001), respectively, whereas LV fiber shortening was decreased by 35% (p < 0.05) corresponding to the 257% increase in wall stress (p < 0.001). After 5 minutes, LV dimensions, fiber shortening, and wall stress had returned to baseline levels. After 10 minutes, fiber shortening was increased 67% (p < 0.05), although wall stress was maintained at baseline levels. Simultaneously, the aortic mean blood pressure, heart rate, and cardiac output peaked 112% (p < 0.001), 81% (p < 0.001), and 125% (p < 0.01) above baseline, respectively. CONCLUSIONS: Cross-clamping grossly increased systemic afterload grossly and was followed by moderate LV dilation, which resolved after 5 minutes owing to the combined effects of proximal vasodilation, increased myocardial contractility, and tachycardia. This hyperdynamic circulatory state was maintained during cross-clamping and decreased after declamping.

Animals↗

PubMed1995

Cardiovascular response in patients with and without myocardial ischaemia during dobutamine echocardiography stress test for coronary artery disease.

Dobutamine is widely used in cardiac stress testing for coronary artery disease and myocardial viability. To assess the systemic cardiovascular response during dobutamine echocardiography stress testing, we investigated nine patients without myocardial ischaemia (group 1, aged 48 to 72 years) and nine patients with myocardial ischaemia during the test (group 2, aged 53 to 73 years), by use of Doppler/echocardiography and subclavian artery pulse trace calibrated with brachial artery pressures. Peripheral resistance, total arterial compliance, and aortic characteristic impedance were estimated using a 3-element windkessel model of the systemic circulation. During infusion of dobutamine up to 40 micrograms kg-1 min-1, arterial pressure was maintained near baseline levels, whereas heart rate and cardiac index increased, more so in group 1 (mean: 89 and 79%) than in group 2 (58 and 52%; P < 0.05 vs. group 1). Peripheral resistance was decreased by > or = 32% at peak stress, whereas characteristic impedance was maintained at or above baseline in both groups, and total arterial compliance was not significantly altered. The cardiovascular response in group 2 was not influenced by the wall motion abnormalities. Thus, in these patients the inotropic, chronotropic, and vasodilatory effects of dobutamine balanced the ischaemic impairment of left ventricular function during the stress test.

Aged↗

PubMed1995

Effect of sodium nitroprusside on cardiac output during cross-clamping of the descending thoracic aorta in pigs.

Sodium nitroprusside (SNP) is used to control proximal hypertension during cross-clamping of the descending thoracic aorta (XC). To assess the haemodynamic effects of SNP on cardiac output (CO) during XC, 21 pigs were anaesthetized with ketamine and fentanyl. In the control group (n = 11), no vasodilating therapy was given. In the investigation group (SNP group), 2 animals died during the surgical preparation and were excluded, leaving 8 animals in the group (n = 8). In these animals, SNP was infused in order to keep the mean arterial pressure (MAP) at about 100 mm Hg during cross-clamping. In both groups, aorta was cross-clamped for 30 min, and cardiac output (CO) was measured by the thermodilution technique. Following cross-clamping, CO increased 107% in the control group and 96% in the SNP group. There was an increase in heart rate (HR) of 77% in the control group and of 110% in the SNP group, and a reduction in systemic vascular resistance of 41% in the SNP group. Stroke volume (SV) was unchanged in both groups. MAP increased 83% in the control-group. No differences were observed between the two groups regarding central venous pressure or pulmonary artery pressure. Four animals in the SNP group died 5-10 min after release of the aortic clamp. In conclusion, we found equal increase in CO in both groups. The increase in CO was related predominantly to increased HR, whereas SV was largely unaltered. Vasodilation with SNP increased the mortality following clamp removal in this experimental model.

Animals↗

PubMed1995

Systemic cardiovascular response in hemodialysis without and with ultrafiltration with membranes of high and low biocompatibility.

In order to test whether dialyzer membrane biocompatibility influences systemic cardiovascular function, we treated 8 hemodialysis patients (4 men and 4 women, aged 24-73 years) with a low-biocompatible (cuprophane) and a high-biocompatible (polyacrylonitrile) membrane in a randomized double-blind crossover protocol using bicarbonate hemodialysis without ultrafiltration for the first 60 min and with ultrafiltration for the remaining treatment time. Left ventricular function and systemic hemodynamics were assessed noninvasively at baseline and during treatment by Doppler echocardiography combined with external subclavian artery pulse trace calibrated with oscillometrically measured brachial artery blood pressures. There was no significant difference in the cardiovascular response to the 2 membranes, neither during isolated hemodialysis nor when ultrafiltration was added. Mean arterial pressure increased 10% (p < 0.001) during isolated hemodialysis and returned to baseline levels with ultrafiltration. The cardiac index decreased 22% (p < 0.001) during ultrafiltration, due to the greater decrease in left ventricular stroke index (30%, p < 0.001) than increase in heart rate (9%, p < 0.05). Total peripheral resistance increased 10% (p < 0.05) during isolated hemodialysis and a further 19% (p < 0.01) when ultrafiltration was added. Hence, profound cardiovascular alterations were observed during hemodialysis treatment; however, these changes were not related to the biocompatibility of the membranes.

Acrylic Resins↗

PubMed1995

Comparison of digital dipyridamole stress echocardiography and upright bicycle stress echocardiography for identification of coronary artery stenosis.

This study compared the diagnostic accuracy of dipyridamole (0.84 mg i.v./10 min) and bicycle stress echocardiography in 37 patients with inconclusive standard bicycle electrocardiography (ECG) tests; all underwent coronary angiography. Sensitivity for detection of coronary stenosis with dipyridamole echocardiography was 68% (21 of 31 patients), and for 1-, 2- and 3-vessel disease 56, 69 and 83%, respectively. Overall bicycle echocardiography sensitivity was 84%, and 78, 88 and 83% for patients with 1-, 2- and 3-vessel disease, respectively. Dipyridamole echocardiography was negative in all 6 patients with negative coronary angiography (specificity 100%), bicycle echocardiography was positive in 2 (specificity 67%). We conclude that dipyridamole echocardiography tends to be less sensitive in patients with mild disease, but is more specific than bicycle echocardiography.

Adult↗

PubMed1994

Calcitonin gene-related peptide (human alpha-CGRP) counteracts vasoconstriction in human subarachnoid haemorrhage.

Calcitonin gene-related peptide (CGRP) is a neuropeptide co-stored with tachykinins (substance P, neurokinin A) in cerebrovascular sensory fibers in the trigeminal ganglion. Preceding studies on subarachnoid hemorrhage (SAH) revealed that an enhanced release of CGRP resulted in the selective loss of perivascular CGRP. Therefore, the present study was designed to evaluate the effects of intravenous administration of human alpha-CGRP on cerebral vasoconstriction in the postoperative course after SAH in 5 patients (8 infusions). Cerebral vasoconstriction was evaluated with transcranial Doppler sonography. The increase in the relationship between middle cerebral artery (MCA) velocity and internal carotid artery (ICA) velocity (the hemodynamic index) was used as an indicator of vasoconstriction and compared to the contralateral side. A significant reduction was found in the hemodynamic index during the CGRP infusion (4.3 +/- 0.5, P < 0.05) as to compared to before infusion (6.2 +/- 0.5). There was no measurable change in the hemodynamic index on the contralateral side. No significant change was observed in pulsatility index, blood pressure or consciousness during the peptide infusion. A significant increase in heart rate was observed during the infusion as compared to before and after infusion (90 +/- 4 vs. 76 +/- 5). Cardiac ultrasound data indicated a mean cardiac output increase of 1.9 liter/min, and a mean decrease in total peripheral resistance of 538 dynes s/cm5. The results obtained show that infusion of human alpha-CGRP may induce normalisation of cerebrovascular tone in SAH.

Adult↗

PubMed1994

Noninvasive study of left ventricular function and systemic haemodynamics during dipyridamole echocardiography stress test.

Left ventricular function and systemic haemodynamics were noninvasively assessed during cardiac stress testing with dipyridamole (0.84 mg kg-1 i.v.) in 10 subjects (44-61 years) with normal coronary arteries (group 1), and in 14 patients (46-77 years) with coronary artery disease either without (group 2, n = 6) or with (group 3, n = 8) echocardiographic evidence for myocardial ischaemia during test. Left ventricular wall motion and dimensions, and aortic root pressure and flow were obtained by Doppler echocardiography combined with an externally traced subclavian artery pulse calibrated with brachial artery pressures. Peripheral arterial resistance, total arterial compliance, and aortic characteristic impedance were estimated from aortic root pressure and flow, by use of a three-element windkessel model of the systemic circulation. Left ventricular ejection fraction improved from baseline to peak stress in group 1 (mean +/- SD: 62 +/- 6% vs. 65 +/- 6%, P = 0.05), whereas it was not significantly changed in group 2 (58 +/- 10% vs. 56 +/- 6%) and decreased in group 3 (53 +/- 10% vs. 43 +/- 10%, P < 0.05). Otherwise, the haemodynamic response was similar in the three groups: heart rate and cardiac index increased by at least 30% and 37%, respectively, whereas stroke index and arterial pressures were maintained at or slightly above baseline. Peripheral resistance decreased by at least 22%, and total arterial compliance and aortic characteristic impedance were not significantly altered during test. The worsening of wall motion abnormality at peak stress in group 3 was not significantly related to the change in systemic haemodynamics. Thus, dipyridamole acted predominantly on the arterioles without significantly influencing the large systemic arteries. Myocardial ischaemia during test impaired regional and global left ventricular function, but did not influence the systemic haemodynamic response.

Adult↗

PubMed1994

Three-dimensional echocardiography for quantitative left ventricular wall motion analysis: a method for reconstruction of endocardial surface and evaluation of regional dysfunction.

A method for quantitative LV wall motion analysis based on 3-D reconstruction of the LV endocardial surface is presented. The reconstruction is based on a minimum of three transthoracic apical 2-D cineloops of the LV, digitally transferred from the ultrasound scanner to a computer. Images are obtained by rotating the transducer around the LV long axis. Endocardial borders are traced with an automatic edge detection algorithm with manual correction. These borders are used with a specially designed computer algorithm for reconstruction of LV cavity 3-D shape, and LV volumes, ejection fraction, and endocardial surface area can be determined. The end-diastolic and end-systolic endocardial surfaces are compared for analysis of regional wall motion. A threshold value is selected to discriminate between normal and abnormal wall motion. Regional wall motion abnormalities are displayed in a bull's eye plot, and the corresponding endocardial surface area is expressed in percent of the total endocardial area. Phase analysis is performed from reconstruction of the endocardial surface throughout the cardiac cycle, and displays regions with abnormal wall motion as being out of phase with LV volume variation. Thus, LV 3-D reconstruction performed by this method can be used for quantitative analysis of wall motion in several clinical situations, and due to the simplicity of processing the data, can be useful outside the research laboratory.

Echocardiography↗

PubMed1994

Model-based estimation of vascular parameters: evaluation of robustness and suitability of models.

Left ventricular performance depends not only on myocardial state, but also on the properties of the systemic arterial tree. These properties can be assessed from recordings of aortic root pressure and flow by the use of appropriate vascular models. Noninvasive estimates of aortic root pressure and flow can be obtained by the combined use of calibrated external subclavian artery pulse tracing and Doppler echocardiography. With recent advances in computer technology, estimation of model parameters are thus accessible in the clinical setting. We discuss the suitability of different parametric vascular models together with methods for adapting these models to the measured aortic root pressure. We compared the results obtained with simple vascular models (three-component modified Windkessel models) with those of five-component models. The simpler models gave less accurate approximation of the measured pressure waveform, but for a representative set of aortic root pressure and flow data, the simpler models provided adequate estimates of the peripheral arterial resistance, the total arterial compliance, and the proximal aortic area compliance. Furthermore, the simpler models are robust for measurement noise with simple estimation algorithms. Distal arterial pressure and flow waveforms are more oscillatory, and for these the five-component model has more robust estimation schemes with more accurate estimated parameters. Hence, we conclude that for clinical noninvasive assessment of aortic vascular properties, the simpler three-component models provide adequate information. For assessment of the peripheral arteries with large oscillations in the flow, the three-component models can give more than 10% error in the compliance estimate and more complex models can be appropriate.

Aorta↗

PubMed1994

Exercise tolerance and work ability following aorto-coronary bypass surgery.

This investigation was performed to study the reasons for receiving disability pension after aortocoronary bypass surgery. During the period March 1983 to November 1985, 250 patients underwent aortocoronary bypass surgery. At a mean follow-up of 4.9 years (range 3.6-6.7) after the operation, 31 patients were dead. Of the 219 survivors, all except four underwent a follow-up examination including an exercise test. The mean physical work capacity had increased from 92.2 W preoperatively to 119.3 W at follow-up (p < 0.001). At follow-up, however, 72 patients had received disability pension. The percentage of positive ECG-tests were equal among those who were working and those who had received disability pension. We suggest that, among those who had received disability pension, about 50% were in sufficient physical condition to manage their previous jobs or another type of job. Reasons other than physical working capacity played an important part as criteria for receiving disability pension.

Adult↗

PubMed1994

Angiographic findings of silent ischaemia following aortocoronary bypass surgery.

Silent ischaemia, defined as ST-depression > or = 1 mm without chest pain, was found on exercise testing in 22 (10.7%) of 206 patients who underwent aortocoronary bypass surgery in the period from March 1983 to November 1985. Exercise testing was performed 4.9 (range 3.6-6.7) years after operation on an electrically braked bicycle. Sixteen of the 22 patients were free from chest pain, while the remaining six had slight to moderate angina pectoris on exercise. Coronary angiography was performed in 21 patients with silent ischaemia; one of the 22 patients died before this investigation. Some 13 patients had one or more occluded grafts, one a new stenosis in a native vessel and five incomplete myocardial revascularization. For the remaining two patients, no aetiology for the ischaemia was found, and revascularization appeared to be complete. Before surgery, 13 patients had three-vessel disease, six two-vessel disease and three one-vessel disease. At follow-up, two patients had three-vessel disease, ten two-vessel disease and seven one-vessel disease. The value of identifying patients with silent ischaemia after aortocoronary bypass surgery with regard to life expectancy and quality is controversial. Subsets of patients, namely, those with main-stem stenosis and three-vessel disease, may benefit from secondary operation. Identification of these patients may therefore be of clinical importance.

Adult↗

PubMed1993

Digital dipyridamole stress echocardiography in silent ischemia after coronary artery bypass grafting and/or after healing of acute myocardial infarction.

This study evaluates dipyridamole stress echocardiography in silent ischemia. Fourteen patients with previous coronary artery bypass grafting (group A) and 16 patients with healed myocardial infarction (group B) were studied. All had > or = 1 mm ST depression without chest pain during bicycle exercise testing. Left ventricular wall motion was analyzed using a computerized display of digital systolic cineloops with a high frame rate. Test results were compared with coronary angiography. Dipyridamole echocardiography accurately identified patients with significant coronary artery stenosis in both groups (3 of 4 in group A, 11 of 14 in group B). Retrograde flow to the occluded native artery was associated with positive results on dipyridamole testing in 6 of 7 patients in group A and all 3 in group B. Sensitivity, specificity and diagnostic accuracy for detecting significant coronary stenosis or occlusions with retrograde flow was 78, 100 and 83%, respectively. Patients with angiographic multivessel disease had a significantly larger increase in wall motion score index during dipyridamole stress than patients with 0- or 1-vessel disease, 0.18 +/- 0.11 versus 0.05 +/- 0.18 (p < 0.05). Two patients developed symptomatic bradycardia and hypotension during dipyridamole infusion. It is concluded that dipyridamole echocardiography accurately identifies myocardial regions with restricted coronary flow. Stress echocardiography is a valuable tool for assessing coronary flow in silent ischemia.

Adult↗

PubMed1993

Noninvasive computerized assessment of left ventricular performance and systemic hemodynamics by study of aortic root pressure and flow estimates in healthy men, and men with acute and healed myocardial infarction.

Aortic root pressure and flow data can be used to assess left ventricular (LV) performance and properties of the systemic arterial tree. The calibrated subclavian arterial pulse trace was combined with echocardiographic imaging and Doppler velocity recordings to obtain noninvasive estimates of aortic root pressure and flow in 8 healthy subjects (group A), 12 patients with recent myocardial infarction (group B), and 8 with healed myocardial infarction and a dilated left ventricle (group C). The pressure and flow data were transferred to a computer and processed in specially designed software, including a new procedure for estimation of 3-element windkessel model parameters. There were no significant group differences for either aortic root pressure estimates or heart rate. In groups B and C, stroke and cardiac indexes were lower and total peripheral resistance higher than in group A. There were no group differences in the model estimates of total arterial compliance, whereas the characteristic impedance was greater in group C than in A, indicating a less compliant aorta in C. Both LV total and steady power were less in groups B and C than in A, whereas no group difference was found for percent oscillatory power. The reproducibility for recording was good for the aortic root pressure estimates, and lower for the derived parameters (stroke and cardiac indexes, windkessel model parameters and LV power), whereas that for interpretation was generally good. This method provides a unique noninvasive access to important parameters of LV function and the systemic circulation.

Adult↗

PubMed1993

Non-invasive estimates of aortic root pressures: external subclavian arterial pulse tracing calibrated by oscillometrically determined brachial arterial pressures.

This investigation assessed the ability of a non-invasive method to reproduce aortic root pressure waveform and pressures. An external pulse tracing of the subclavian artery was obtained simultaneously with direct aortic root pressures during routine left heart catheterization in 26 patients (aged 39-74 years) with various cardiovascular disorders. Indirect brachial arterial peak-systolic and nadir-diastolic pressures were obtained with oscillometry. The direct and indirect peak-systolic and nadir-diastolic pressures, were separately used to calibrate the pulse tracing. Adequate pulse tracing was obtained in 19 patients (73%). The waveforms agreed well with cross-correlation coefficients for systole and diastole of 0.98. The difference between the pulse trace and the direct pressure curve, when the first was calibrated with the peak-systolic and nadir-diastolic pressures of the latter on average was less than 1 mmHg for systole and diastole. At end-systole the mean difference was 5 mmHg. Oscillometric brachial arterial peak-systolic pressures were (mean +/- SD) 3 +/- 7 mmHg below the corresponding direct measurements, while diastolic pressures were 8 +/- 4 mmHg above. The difference between the pulse trace and the direct pressure curve, when the pulse trace was calibrated with oscillometric pressures, was at end-systole 6 +/- 6 mmHg and for mean arterial pressures 5 +/- 4 mmHg. Thus, the external subclavian arterial pulse tracing provides a non-invasive, clinically feasible access to the aortic root pressure waveform. With optimal calibration, good estimates of aortic root pressures throughout systole and diastole can be obtained, while end-systolic pressure tends to be slightly overestimated.

Adult↗

PubMed1991

Anterior perforations in lumbar discectomies. A report of four cases of vascular complications and a CT study of the prevertebral lumbar anatomy.

Four cases of vascular complications to anterior perforations during discectomy prompted a CT study to measure lumbar disc diameters and to evaluate the prevertebral anatomy. Fifty young adults who had been referred for low-back pain and/or sciatica but had not undergone operation were included. In five additional patients, prone versus supine CT examinations were compared. Six typical configurations of the vascular anatomy could be classified to explain the type of vascular complications occurring at the L3-4 and L4-L5 disc levels. The sagittal diameter of the three lowest lumbar discs varied from 33 to 56 mm, indicating the importance of this parameter as an intraoperative guideline for the spine surgeon. Air-filled intestines were observed anterior to the L5-S1 disc predominantly in the prone position. The possible relationship between this finding and postoperative discitis is discussed.

Adult↗

PubMed1990

[Ultrasonography of strangulated Richter's hernia].

Ultrasonography may show early pathological changes in an obstructed intestine and also identify abnormal structures in the abdominal wall and inguinal region. We describe a patient with intestinal obstruction due to a femoral hernia of Richter's type. The hernia was shown well by ultrasonography. Ultrasonic examination of the abdomen, including the inguinal regions, may facilitate earlier diagnosis in patients with acute abdominal disease.

Aged↗

PubMed1990

[Chloroquine poisoning].

Chloroquine poisoning has profound effects, chiefly on contractility and conduction of the heart. No treatment has been proven effective, and most cases of serious poisoning are fatal. We describe one case of chloroquine poisoning and discuss its treatment.

Adult↗