Haemodynamic effects of arterial compliance, total peripheral resistance, and glyceryl trinitrate on regurgitant volume in aortic regurgitation.

STUDY OBJECTIVE: Afterload reduction is known to reduce regurgitant flow in patients with aortic regurgitation. Both arterial compliance and total peripheral resistance are determinants of afterload. The aim of this study was to evaluate the influence of arterial compliance and total peripheral resistance on the regurgitant volume. DESIGN: The values of arterial compliance and total peripheral resistance were assessed during aortic regurgitation at different regurgitant orifice areas in eight pigs before and after a bolus of glyceryl trinitrate. In a computer model the importance of arterial compliance and total peripheral resistance on the regurgitant volume was assessed by keeping each of them constant while the other variable was changed. MEASUREMENTS AND MAIN RESULTS: In both the experimental and computer models a very strong correlation was found between decreased total peripheral resistance and decreased regurgitant volume. Arterial compliance was of hardly any importance. A bolus of glyceryl trinitrate reduced regurgitant volumes and regurgitant fractions significantly. CONCLUSIONS: Total peripheral resistance is an important factor in influencing the regurgitant volumes at a given regurgitant orifice area in aortic regurgitation, while arterial compliance is of less importance. Glyceryl trinitrate effectively reduces the regurgitant volumes by its effect on peripheral resistance.

Flow estimation using ultrasound imaging (color M-mode) and computer postprocessing.

We have developed a method to calculate flow noninvasively in blood vessels using color Motion-mode (M-mode) and computer postprocessing. The velocity of each point in the cross-sectional area of the vessel was found from the color M-mode recording by correcting for angle both distances and velocities and by assuming a symmetrical circular velocity field. Volume flow was then found by integrating the velocity field at 5-ms intervals through the cardiac cycle. In a cardiovascular hydromechanical model, a correlation of 0.99 and p value of less than 0.001 were found between estimated and measured flow in the model (n = 8). In 20 healthy individuals, we made 31 investigations in the common carotid (CCA), internal carotid (ICA), and external carotid (ECA) artery, comparing flow in the CCA with the added flow in the ICA and ECA. The values (CCA versus ICA + ECA) correlated with r = 0.91 and p less than 0.01. Repeated investigations (n = 8) in one individual gave flow estimates of 495 +/- 50 ml/min in the CCA, 304 +/- 45 ml/min in the ICA, and 165 +/- 37 ml/min in the ECA (means +/- SD). This article shows that this system can make accurate estimation of blood flow to the brain noninvasively.

Venous air embolism in swine: transport of gas bubbles through the pulmonary circulation.

The assumption that the lung is an effective filter for gas bubbles is of importance for certain occupations (e.g., divers, astronauts) as well as in the accomplishment of several medical procedures. The filtering capacity was tested in pigs by use of continuous air infusion into the right ventricle and a transesophageal echocardiographic transducer for detection of air in the left atrium. Twenty pigs, anesthetized with pentobarbital sodium and mechanically ventilated, were divided into groups that received air at infusion rates of 0.05 (group 1a, n = 7), 0.10 (group 2, n = 6), and 0.20 (group 3, n = 5) ml.kg-1.min-1. Two pigs served as controls. The breakthrough incidence was 0, 67, and 100%, respectively. Group 1a received a second infusion of 0.10 ml.kg-1.min-1 (group 1b, n = 7), and spillover of bubbles occurred in only 14% of these pigs. Infusion of gas caused a maximum increase in mean pulmonary arterial pressure (PAP) of 129 +/- 9% to 39.2 +/- 1.3 (SE) mmHg, with no significant difference between the groups. Breakthrough was observed only in animals with a dramatic reduction in mean arterial pressure and a PAP that returned to almost-normal values at spillover time. Our results suggest that the threshold value for breakthrough of air bubbles in pigs is reduced compared with that in dogs. The hemodynamic consequences at a given infusion rate are, however, greatly enhanced.

Regurgitant volume in aortic regurgitation from a parameter estimation procedure.

The regurgitant volume and regurgitant orifice area as well as total peripheral resistance and arterial compliance were estimated in a cardiovascular hydromechanical simulator and in 10 patients with aortic regurgitation. A parameter estimation procedure based on a simple model of the cardiovascular system, Doppler measurements of the regurgitant jet, aortic systolic flow, and systolic and diastolic blood pressures was used. In the cardiovascular simulator the estimated regurgitant orifice area was compared with the size of a hole in the disk of a mechanical aortic valve. In the patients the regurgitant fraction was compared with semiquantitative grading from echocardiography routinely performed in our laboratory. In the hydromechanical simulator, the estimated regurgitant orifice area of 26.5 +/- 3.5 (SD) mm2 (n = 9) was not different from the true value of 24 mm2. In the patients there was a fair relationship between the estimated regurgitant fraction and the semiquantitative grading. The estimated regurgitant orifice areas varied between 1.6 and 31.2 mm2. The estimated mean values of total peripheral resistance and arterial compliance were 1.67 +/- 0.55 mmHg.s.ml-1 and 1.30 +/- 0.42 ml/mmHg, respectively.

Pressure half-time in aortic regurgitation: evaluation with Doppler in a cardiovascular hydromechanical simulator and in a computer model.

Doppler echocardiographic determination of pressure half-time has been proposed as a method of assessing the severity of aortic regurgitation. To evaluate this method, we assessed the relation between pressure half-time and simulated aortic regurgitant flow under various conditions in two models of the cardiovascular system. In a hydromechanical model we assessed the influence of total peripheral resistance and arterial compliance on the pressure half-time as measured by continuous wave Doppler echocardiography. In a computer model that used the half-time of the pressure gradient between the aorta and the left ventricle as an expression of pressure half-time, we assessed the influence of total peripheral resistance and arterial compliance and also the influence of left ventricular compliance on pressure half-time. In both models, although we found an inverse relation between regurgitant orifice area and pressure half-time, changing total peripheral resistance and arterial compliance (but not left ventricular compliance) within the physiologic range significantly altered the pressure half-times. We concluded that the influence of total peripheral resistance and arterial compliance limits the usefulness of Doppler echocardiographic determination of pressure half-time as a method of assessing the severity of aortic regurgitation.

Estimation of regurgitant volume and orifice in aortic regurgitation combining CW Doppler and parameter estimation in a Windkessel-like model.

A method for noninvasive estimation of regurgitant orifice and volume in aortic regurgitation is proposed and tested in anesthetized open chested pigs. The method can be used with noninvasive measurement of regurgitant jet velocity with continuous wave ultrasound Doppler measurements together with cuff measurements of systolic and diastolic systemic pressure in the arm. These measurements are then used for parameter estimation in a Windkessel-like model which include the regurgitant orifice as a parameter. The aortic volume compliance and the peripheral resistance are also included as parameters measurements in the open chest pigs are used. Electromagnetic flow measurements in the ascending aorta and pulmonary artery are used for control, and a correlation between regurgitant volume obtained from parameter estimation and electromagnetic flow measurements of 0.95 over a range from 2.1 to 17.8 mL is obtained.

Estimation of arterial compliance in aortic regurgitation: three methods evaluated in pigs.

Three methods for measuring arterial compliance when aortic regurgitation is present are examined. The first two methods are based on a Windkessel model composed of two elements, compliance C and resistance R. Arterial compliance was estimated from diastolic pressure waveforms and diastolic regurgitant flow for one method, and from systolic aortic pressure waveforms and systolic flow for the other method. The third method was based on a three-element Windkessel model, composed of characteristic resistance r, compliance C and resistance R. In this method arterial compliance was calculated by adjusting the model to the modulus and phase of the first harmonic term of the aortic input impedance. The three methods were compared and validated in six anaesthetised pigs over a broad range of aortic pressures. The three methods were found to give quantitatively similar estimates of arterial compliance at mean aortic pressures above 60 mm Hg. Below 60 mm Hg, estimates of arterial compliance varied widely, probably because of poor validity of the Windkessel models in the low pressure range.

Quantification of aortic regurgitation by Doppler echocardiography: a new method evaluated in pigs.

We have developed a method to quantify aortic regurgitant orifice and volume, based on measurements of the velocity of the regurgitant jet, aortic systolic flow, the systolic and diastolic arterial pressures, a Windkessel arterial model, and a parameter estimation technique. In six pigs we produced aortic regurgitant flows between 2.1 and 17.8 ml per beat, i.e. regurgitant fractions from 0.06 to 0.58. Pulmonary and aortic flows were measured with electromagnetic flow probes, aortic pressure was measured invasively, and the regurgitant jet velocity was obtained with continuous-wave Doppler. The parameter estimation procedure was based on the Kalman filter principle, resulting primarily in an estimate of the regurgitant orifice area. The area was multiplied by the velocity integral of the regurgitant jet to estimate regurgitant volume. A strong correlation was found between the regurgitant volumes obtained by parameter estimation and the electromagnetic flow measurement. These results from our study in pigs suggest that it may be possible to quantify regurgitant orifice and volume in patients completely noninvasively from Doppler and blood pressure measurements.

Myocardial ischaemia and the inflammatory response: release of heat shock protein 70 after myocardial infarction.

OBJECTIVES: To test the hypothesis that heat shock protein (Hsp) 70 may be released into the circulation after acute myocardial infarction (AMI) by exploring the kinetics of Hsp70 release and the relations between Hsp70 and markers of inflammation and myocardial damage in AMI. DESIGN: Blood samples from 24 patients were prospectively collected through to the first day after AMI. Hsp70, interleukin (IL) 6, IL-8, and IL-10 in serum were measured by enzyme linked immunosorbent assay (ELISA). RESULTS: Median Hsp70 concentrations in AMI patients measured at arrival, six hours thereafter, and the following morning were 686, 868, and 607 pg/ml, respectively. These concentrations were all significantly different from those of the control patients with angina with a median serum Hsp70 concentration of 306 pg/ml. Peak Hsp70 correlated with creatine kinase (CK) MB (r = 0.62, p < 0.01) and cardiac troponin T (r = 0.58, p < 0.01). Furthermore, serum Hsp70 correlated with IL-6 and IL-8 at six hours (r = 0.60, p < 0.01 and r = 0.59, p < 0.01, respectively). CONCLUSIONS: In this study, Hsp70 was rapidly released into the circulation after AMI. Circulating Hsp70 is suggested as a marker of myocardial damage. In addition, Hsp70 may have a role in the inflammatory response after AMI.

[Hemopericardium with cardiac tamponade. Case reports from a coronary care unit]. / Hemoperikard med hjertetamponade. Kasuistikker fra en hjerteovervåkingsavdeling.

We describe three patients with cardiac tamponade who had been admitted to a coronary care unit, two because of rupture of the free wall during acute myocardial infarction and one because of proximal aortic dissection. Pericardiocentesis was performed in the coronary care unit after the diagnosis had been made by echocardiography. One of the patients with acute infarction and the one with proximal aortic dissection, who also underwent surgery, survived. We discuss various aspects of acute cardiac tamponade with hemopericardium.

[Acute stroke--who dies in a stroke unit?]. / Akutt hjerneslag--hvem dør i en slagenhet?

Stroke unit care increases the proportions of patients able to live at home, improves functional outcome, reduces the need for institutional care, and reduces mortality. We have evaluated the data on the 69 patients who died in our stroke unit with an acute stroke, among the first 1,000 patients treated. The patients who died were older and had lower functional scores (median Barthel Index score 0 versus 70) and neurological scores (median Scandinavian Stroke Scale score 6 versus 48) at admittance. Early progression of the stroke was also more frequent in the group of patients who died. No differences in blood pressure, heart rate and body temperature were found between the groups, aside from increased diastolic pressure and heart rate in patients who died with an embolic infarction and increased systolic pressure in patients who died with an intracerebral haemorrhage.

[Acute stroke. Patients treated in a stroke unit in Trondheim]. / Akutt hjerneslag. Pasienter behandlet ved slagenheten i Trondheim.

Treatment in a stroke unit raises the proportion of stroke patients who are able to live at home, improves functional outcome, reduces the need for institutional care, and brings down mortality. We have evaluated the data on the first 800 patients treated in our stroke unit. Nine patients were incorrectly registered as acute stroke victims and were excluded from the analysis. Hence, 791 patients (429 men, 362 women; mean age 72.3 years range 35-101 years) fulfilled the criteria for acute stroke or TIA. In the group of 654 patients who had suffered an acute stroke, 85 patients (13%) had intracerebral haemorrhage, 439 (67.1%) nonembolic infarction, and 130 (19.9%) embolic infarction. The majority of the patients were discharged to home (55.4%), while 23.6% were discharged to a rehabilitation institution, and 6.1% were discharged to nursing homes. 48 (6.1%) of the patients died during the stay in hospital. The mean time spent in the stroke unit was 12.1 days.

[Myocardial injury in acute stroke assessed by troponin I]. / Myokardskade ved akutte hjerneslag bedømt med troponin I.

BACKGROUND: Acute ischaemic or haemorrhagic cerebrovascular events may produce myocardial damage. Cardiac troponin I is an indicator of cardiac cell injury with very high sensitivity and specificity. MATERIAL AND METHODS: We measured troponin I in 149 acute stroke patients admitted to the stroke unit of Trondheim University Hospital, Norway, in January to June 1999. RESULTS: 40 patients (27%) had troponin I values at 0.4 microgram/l or higher, indicating myocardial injury. 10 patients (6.7%) had troponin I values above 2.0 micrograms/l. Similarly, the mean value of CK-MB vas higher in the patients with myocardial injury, and these patients had more often ECG findings suggesting myocardial ischaemia. Patients with myocardial injury had a higher rate of previous TIA and heart failure. ECG showed atrial fibrillation in 13 of 39 patients with myocardial damage. Patients with detectable levels of troponin I had more embolic brain infarctions than thrombotic brain infarctions. Patients with myocardial injury did more often have abnormal values of CRP. 9 of 10 patients with troponin I-values above 2.0 micrograms/l had abnormal CRP values. No differences in glycosylated haemoglobin, cholesterol, heart rate, blood pressure or body temperature were found. Patients with the highest troponin I values had lower systolic blood pressure, and a higher heart rate, but these differences were not statistically significant. Patients with troponin I values above 2.0 micrograms/l had lower functional and neurological scores at admittance. Patients with myocardial injury were more often discharged to nursing homes. INTERPRETATION: Many patients with an acute stroke have at the same time a myocardial injury, determined by elevated troponin I values.

[Use of magnetic tomography in cardiology. Introduction of a new method]. / Bruk av magnettomografi i kardiologien. Innføring i en ny metode.

Magnetic resonance imaging of the heart has already become an important tool in evaluating the cardiovascular system. This paper describes the basic principles of magnetic resonance imaging, the application of magnetic resonance imaging in the diagnosis of heart diseases, and the experience of using it in Trondheim since 1987. The paper is illustrated by several heart images from Trondheim.

Segmental aortic wall stiffness from intravascular ultrasound at normal and subnormal aortic pressure in pigs.

Segmental aortic wall stiffness was calculated from intravascular ultrasound images and intravascular pressures in six pigs at normal and subnormal aortic pressures (21 sequences of pressures and areas before and after boli of intravenous nitroglycerin). The wall stiffness was expressed as the pressure-strain elastic modulus (Ep). The Ep was calculated from the formula: Ep = delta PR delta R-1 (P, pressure; R, radius) in two different ways. First from maximal and minimal values of pressure and area. Second as the slope of linear regression line of delta PR as a function of delta R from 29 simultaneous recorded pressures and images. The average Ep value for all sequences in the different segments was 0.58 +/- 0.55 10(5) Pa (Method 1) and 0.50 +/- 0.40 10(5) Pa (Method 2). Ep increased with the distance from the heart at normal aortic pressures. At subnormal aortic pressures after intravenous nitroglycerin this relationship was not so evident. At subnormal aortic pressures the calculated Ep values were significantly reduced in the lower half of the abdominal aorta. The phase lag, i.e. hysteresis, between pressure and diameter was demonstrated. Our study shows the applicability of intravascular ultrasound as a tool to evaluate arterial wall stiffness.

Stroke unit treatment. Long-term effects.

BACKGROUND AND PURPOSE: We have previously shown that treatment in our combined acute and rehabilitation Stroke Unit improves outcome during the first year after onset of stroke compared with stroke patients treated in general wards. The aim of the present trial was to examine the long-term effects of the stroke unit care. METHODS: In a randomized controlled trial, 110 patients with symptoms and signs of an acute stroke were allocated to the Stroke Unit and 110 to general wards. No significant differences existed in baseline characteristics between the two groups. The outcome after 5 years was measured by the proportion of patients at home, the proportion of patients in an institution, the mortality, and the functional state assessed by Barthel Index. RESULTS: After 5 years, 38 (34.5%) of the patients randomized to the Stroke Unit and 20 (18.2%) of the patients randomized to the general wards were at home (P = .006). Sixty-five (59.1%) of the patients from the Stroke Unit and 78 (70.9%) of the patients from the general wards were dead (P = .041), while 7 (6.4%) and 12 (10.9%), respectively, were in an institution (e.g., nursing home) (P = NS). Functional state was significantly better for patients treated in the Stroke Unit. CONCLUSIONS: For the first time it is shown that stroke unit care improves long-term survival and functional state and increases the proportion of patients able to live at home 5 years after the stroke. Combined acute and rehabilitation stroke units appear to be an effective way of organizing treatment for acute stroke patients.

Stroke unit treatment. 10-year follow-up.

BACKGROUND AND PURPOSE: We have previously shown that treatment in our combined acute and rehabilitation stroke unit (SU) improves the outcome during the first 5 years after onset of stroke compared with that for stroke patients treated in general wards (GW). The aim of the present trial was to examine the effects of SU care after 10 years of follow-up. METHODS: In a randomized controlled trial, 110 patients with symptoms and signs of an acute stroke were allocated to the SU and 110 to GW. No significant differences existed in baseline characteristics between the groups. The outcome after 10 years was measured by the proportion of patients at home, the proportion of patients in an institution, the mortality, and the functional state as assessed by the Barthel Index, in which a Barthel Index score of >/=60 was classified as independent or partly independent and a score of >/=95 was classified as independent. RESULTS: After 10 years, 21 (19.1%) of the patients randomized to the SU and 9 (8.2%) of the patients randomized to the GW were at home (P=0.0184). Eighty-three (75.5%) of the patients from the SU and 96 (87.3%) of the patients from the GW were dead (P=0.0082), and 6 (5.4%) and 5 (4.5%), respectively, were in an institution (eg, nursing home; NS). Twenty-two (20.0%) of the SU patients and 9 (8. 2%) of the GW patients had a Barthel Index score of >/=60 (P=0.0118), and 14 (12.7%) and 6 (5.4%), respectively, had a score of >/=95 (P=0.0606). CONCLUSIONS: For the first time it has been shown that SU care improves survival and functional state and increases the proportion of patients able to live at home 10 years after their stroke. Treatment in combined acute and rehabilitation SU seems to have important long-term effects on outcome for stroke patients.

Treatment in a combined acute and rehabilitation stroke unit: which aspects are most important?

BACKGROUND AND PURPOSE: We have previously shown that treatment of acute stroke patients in our stroke unit (SU) compared with treatment in general ward (GWs) improves short- and long-term survival and functional outcome and increases the possibility of earlier discharge to home. The aim of the present study was to identify the differences in treatment between the SU and the GW and to assess which aspects of the SU care which were most responsible for the better outcome. METHODS: Of the 220 patients included in our trial, only 206 were actually treated (SU, 102 patients; GW, 104 patients). For these patients, we identified the differences in the treatment and the consequences of the treatment. We analyzed the factors that we were able to measure and their association with the outcome, discharge to home within 6 weeks. RESULTS: Characteristic features in our SU were teamwork, staff education, functional training, and integrated physiotherapy and nursing. Other treatment factors significantly different in the SU from the GW were shorter time to start of the systematic mobilization/training and increased use of oxygen, heparin, intravenous saline solutions, and antipyretics. Consequences of the treatment seem to be less variation in diastolic and systolic blood pressure (BP), avoiding the lowest diastolic BP, and lowering the levels of glucose and temperature in the SU group compared with the GW group. Univariate analyses showed that all these factors except the level of glucose were significantly associated with discharge to home within 6 weeks. In the final multivariate Cox regression model, shorter time to start of the mobilization/training and stabilized diastolic BP were independent factors significantly associated with discharge to home within 6 weeks. CONCLUSIONS: Shorter time to start of mobilization/training was the most important factor associated with discharge to home, followed by stabilized diastolic BP, indicating that these factors probably were important in the SU treatment. The effects of characteristic features of an SU, such as a specially trained staff, teamwork, and involvement of relatives, were not possible to measure. Such factors might be more important than those actually measured.

Stroke unit treatment improves long-term quality of life: a randomized controlled trial.

BACKGROUND AND PURPOSE: We have previously shown that treatment of acute stroke patients in the combined acute and rehabilitation stroke unit in our hospital improves survival and functional outcome compared with treatment in general wards. The primary aim of the present trial was to examine whether the treatment in our stroke unit had an effect on different aspects of quality of life (QoL) for stroke patients 5 years after the onset of stroke. METHODS: In a randomized controlled trial, 110 patients with symptoms and signs of an acute stroke were allocated to the stroke unit and 110 to general wards. No significant differences existed in baseline characteristics between the two groups. The patients alive after 5 years were assessed by the Nottingham Health Profile (NHP) and the Frenchay Activities Index (FAI), which were the scales used as primary outcome measures for QoL. As secondary outcome measures we used a global score for the NHP and a simple visual analogue scale (VAS). RESULTS: After 5 years, 45 of the patients treated in the stroke unit and 32 of those treated in general wards were alive. All surviving patients were assessed by the FAI. Thirty-seven (82.2%) of the stroke unit patients and 25 (78.1%) of the general wards patients were assessed by the NHP; 38 (84.4%) and 28 (87.5%), respectively, were assessed by the VAS. Patients treated in the stroke unit had a higher score on the FAI (P=0.0142). Assessment with the NHP showed better results in the stroke unit group for the dimensions of energy (P=0.0323), physical mobility (P=0.0415), emotional reactions (P=0.0290), social isolation (P=0.0089), and sleep (P=0.0436), although there was no difference in pain (P=0.3186). The global NHP score and VAS score also showed significantly better results in the stroke unit group (NHP, P<0.01; VAS, P<0.001). Patients who were independent in activities of daily living had significantly better QoL assessed by these scales than patients who were dependent. CONCLUSIONS: Our study shows for the first time that stroke unit care improves different aspects of long-term QoL for stroke patients.

Measurement of volumetric mitral and aortic blood flow based on a new freehand three-dimensional colour flow imaging method. An in vivo validation.

AIMS: To validate a new three-dimensional (3D) colour flow method used to calculate cardiac output (CO) in aortic and mitral blood flow. METHODS: The transducer was freely tilted transthoracically using a magnetic locating device recording its spatial position. Raw digital ultrasound data were recorded in healthy subjects during 10-20 heartbeats at a high frame rate ranging from 41 to 66 frames/s and analysed off-line with no loss in temporal resolution. Blood flow velocities aligned with the ultrasound beam were integrated across a moving spherical surface to calculate volumetric flow. RESULTS: The range of agreement between the 3D mitral and 3D aortic method was 0.04+/-1.32 l/min (mean+/-2 standard deviations). The range of agreement between 3D aortic flow and the two-dimensional (2D) pulsed wave Doppler method (2DPW) in the left ventricular outflow tract (LVOT) was 0.7+/-1.7 l/min, while the range of agreement between 3D mitral flow and the 2DPW method was 0.88+/-1.64 l/min. CONCLUSION: The 3D methods agreed well. The 3D volumetric flow overestimated the 2DPW method, as expected, and the range of agreement was wide. The common pitfalls in pulsed wave ultrasound methods to calculate CO were avoided, as the 3D method was angle-independent, no assumptions about the velocity profile were made, and a moving sample surface was applied. The acquisition of data was fast and easy and high temporal resolution was achieved.