Biomedical subjects

S Andreas

Publications and source records attributed to S Andreas.

51 records · Page 3Linked to original sources

PubMed1993

Periodic respiration in patients with heart failure.

Patients with heart failure are known to demonstrate periodic respiration (PR) during sleep. The factors causing PR are not well known. We therefore studied 20 patients (aged 18-66 years) with idiopathic dilated cardiomyopathy. Full-night polysomnography and evaluation of respiration and transcutaneous oxygen saturation were performed. Hypercapnic ventilatory response (HCVR) was evaluated during daytime. The patients showed PR for 25 +/- 26% (mean +/- standard deviation) of total sleep time. During PR, oxygen desaturated 7.1 +/- 4.6%. Sleep was impaired. HCVR was normal. Oxygen desaturation during PR was predicted by HCVR (r = 0.47, P < 0.05) and left atrial diameter (r = 0.60, P < 0.05). The time period of PR expressed as a fraction of total sleep time was correlated with HCVR (r = 0.45, P < 0.05) and left atrial diameter (r = 0.51, P < 0.05). In conclusion, PR with oxygen desaturation, arousals, and impaired sleep was observed in stable heart failure. HCVR and left heart dimensions were related to PR. These findings confirm the concept of a feedback loop describing respiratory control in PR.

Adolescent↗

PubMed1993

Validation of automated sleep stage and apnoea analysis in suspected obstructive sleep apnoea.

Full-night polysomnography is necessary for the diagnosis of obstructive sleep apnoea (OSA). However, analysis of the sleep stages and apnoeas is time-consuming. Computer systems for automated analysis have, thus, been developed to alleviate this task. We investigated 27 consecutive patients referred to our sleep laboratory with suspected OSA. The analysis of sleep stages and apnoeas was performed by visual scoring, according to Rechtschaffen and Kales, and by commercially available automated analysis device. The mean difference between visual scoring and automated analysis was -1, 111, -140, -3, 1 and 27 min, for sleep stages awake, I, II, III, IV and rapid eye movement (REM) respectively. For the apnoea index, the automated analysis rated a lower figure (mean difference 7.h-1, 95% confidence interval 2-12.h-1). The diagnosis of OSA was performed with a sensitivity of 85% and a specificity of 93% by automated analysis. Comparison of two independent handscores showed good agreement, with a mean difference of 6, 4, 3, -7, 1 and -1 min, for sleep stages awake, I, II, III, IV and REM, respectively. In conclusion, the automated analysis underestimates stage I sleep and the apnoea index. Visual scoring is advisable for control of the results. Automated analysis should only be used by those who are able to perform a visual analysis.

Aged↗

PubMed1992

[Why is the Doppler pressure gradient higher than the one measured by catheter?].

Hemodynamic assessment of aorto-iliac occlusive disease is necessary for successful arterial reconstruction of the legs. Various methods have been proposed and the "pull-through" intra-arterial pressure measurement method is accepted as the best standard. The pressure readings, however, seemed to depend on the intraluminal position of the catheter. To explain these observations and make a comparison between the Doppler method and the "pull-through" method, we have studied center-line velocity changes at the stenosis throat by Doppler ultrasound, and axial and lateral pressure gradients using pressure transducers, mounted 10 mm and 40 mm downstream of short (4 mm) and long (40 mm) axisymmetric sharp-edged model stenoses having cross sectional reduced areas of 64%, 84%, 91%, and 96%. Axial manometric pressures measured 10 mm after the throat of 84% stenosis were more than twice as high as the lateral pressures. There was no significant difference between axial and lateral pressures measured 40 mm downstream from throat. This pressure distribution has important clinical relevance. Mean and peak pressure gradients for both the Doppler method and manometric measurements were compared. Measurements with Doppler method and manometric measurements, indicated that mean pressure gradients (r = 0.98; SEE = +/- -2.4 mmHg) correlate better than peak pressure gradients (r = 0.90; SEE = +/- 16.5 mmHg). Doppler gradients were higher than manometer gradients. Overestimation was 13% for mean pressure gradients, and ranging from 10% to 150% for peak pressure gradients. Explanation for the difference between mean Doppler and catheter gradient may be the pressure recovery occurring in the relaminarized poststenotic regions.

Aortic Valve Stenosis↗

PubMed1992

Changes in heart rate during obstructive sleep apnoea.

The mechanisms behind the decrease in heart rate during apnoeas in patients with obstructive sleep apnoea (OSA) are little known. Recent findings in animal experiments indicate that stimulation of the upper airway activates postinspiratory and cardiac vagal neurones in the medullary respiratory centre, causing alterations in heart rate and respiratory rhythm. Since OSA leads to a collapse of the airway and consequent stimulation of upper airway receptors, we studied the interrelations between heart rate and respiratory rhythm during apnoea and during negative intrathoracic pressure generated by the Mueller manoeuvre (MM). Fifteen patients with OSA (apnoea hypopnoea index (AHI) 45 +/- 28.h-1) were studied by polysomnography, during a MM and a Valsalva manoeuvre, each of 15 s duration. The heart rate decrease (delta HRA) and the increase in total respiratory cycle duration (TOT) were evaluated during apnoea in non-rapid eye movement (REM) sleep. Patients with OSA demonstrated a decrease in heart rate during apnoea (-14.4 +/- 9.0 beats.min-1), and during MM (-11.5 +/- 13.5 in OSA vs 3.1 +/- 7.8 beats.min-1 in a control group). TOT increased during apnoea (4.6 +/- 3.1 s). There was a significant correlation between delta HRA and AHI (r = -0.64) as well as between delta HRA and increase in TOT (r = 0.62). These findings indicate that upper airway obstruction may cause an activation of receptors at the site of airway collapse or distortion leading to changes in heart rate and respiratory rhythm.

Female↗

PubMed1991

Doppler echocardiographic analysis of cardiac flow during the Mueller manoeuver.

The inspiration against a closed airway, the Mueller manoeuver, leads to a negative intrathoracic pressure. It is controversially discussed whether this is causing an augmentation of right heart murmurs. There is only limited knowledge on the temporal relationship of the negative intrathoracic pressure with right and left ventricular filling and stroke volume. To investigate this relationship, the flow through the mitral, aortic, tricuspid and pulmonary valves was studied continuously by Doppler echocardiography during a standardized Mueller manoeuver in 15 healthy subjects (age 45 +/- 10 years). Five heart beats after the initiation of the manoeuver, flow through the mitral and aortic valve decreased 12.2 +/- 7.2% (P less than 0.001) and 10.1 +/- 6.6% (P less than 0.001), respectively. A transient increase of 15.1 +/- 9.2% (P less than 0.001) in tricuspid flow was followed by a 14.3 +/- 9.8% (P less than 0.005) increase of flow through the pulmonary artery. Ten heart beats after the initiation of the Mueller manoeuver, flow through the pulmonary artery again reached baseline, while tricuspid flow remained below baseline values. In contrast to previous studies, our results indicate that the Mueller manoeuver causes a small and transient increase in right ventricular stroke volume which is unlikely to cause a marked augmentation in right heart murmurs.

Adult↗

PubMed1991

[Impaired diastolic ventricular function in dilated cardiomyopathy with variously reduced systolic function. A Doppler echocardiography analysis].

Diastolic ventricular function was assessed by Doppler echocardiography in 50 patients with idiopathic dilated cardiomyopathy (DCM) and sinus rhythm. The patients were subdivided into two groups with either a moderately reduced ejection fraction (less than 32%; group 1, n = 25) or a severely reduced ejection fraction (less than 32%; group 2, n = 25), the latter having an unfavorable prognosis. The degree of heart failure according to the NYHA classification was more pronounced in group 2 (p less than 0.05). Mean pulmonary capillary wedge pressure (PCm) was also higher in group 2 (gr. 1:9.8 +/- 5.5 vs. gr. 2: 16.2 +/- 8.9; p less than 0.02), and the morphological parameters obtained by conventional M-mode echocardiography showed increased left ventricular volumes and mass in both groups with DCM, as compared with a control group (n = 16); there was a reduced volume/mass ratio in group 2. The parameters of systolic function derived from M-mode and Doppler echocardiography were reduced in patients with DCM, but were more pronounced in group 2. Doppler parameters of diastolic ventricular filling were differently affected in both groups with DCM. In group 1 there was a reduced contribution of the early diastolic phase to ventricular filling (FE/FA) (contr.: 2.29 +/- 0.99 vs gr. 1: 1.40 +/- 0.45; p less than 0.05) and a reduced early peak Doppler velocity, indicating an impaired ventricular relaxation. In group 2, as compared with controls and group 1, there was an increased ratio of early/late diastolic peak velocities (VE/VA) (contr.: 1.49 +/- 0.54 vs gr. 2: 2.32 +/- 1.37; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗

PubMed1991

[ST segmental changes and arrhythmias in obstructive sleep apnea].

Patients with obstructive sleep apnea show a fall in arterial oxygen saturation during apneas. Whether this is causing myocardial ischemia and consecutively ST segment depressions in the electrocardiogram is not known. Therefore 15 consecutive patients (53 +/- 8 years, apnea index 45 +/- 28, minimal oxygen saturation 71 +/- 14%) with OSA were studied by Holter electrocardiogram and polysomnography. History and exercise testing gave no evidence of coronary heart disease. Three patients had ventricular arrhythmias Lown IVA and 10 had Lown I or III. Three patients showed unspecific negative T waves or ST segment elevations. In no patient significant ST segment depression was found. It is concluded that OSA does not lead to ischemic ST segment depression in the absence of coronary heart disease. The cause of ventricular arrhythmias in OSA seems not be related to myocardial ischemia.

Adult↗

PubMed1990

Embolic mononeuropathy in subacute bacterial endocarditis.

A 49-year-old man presented with temperature up to 39.5 degrees C, a sudden peroneal nerve lesion, and a cardiac murmur. The peroneal nerve lesion was likely caused by an embolic occlusion of an artery supplying the nerve. Until now, six cases of embolic mononeuropathy in endocarditis have been reported in the literature. Embolic mononeuropathy is a very rare manifestation of subacute bacterial endocarditis and quite often complicates, as do other more common embolic manifestations, the correct diagnosis.

Embolism↗

PubMed1990

Impaired relationship between Doppler echocardiographic parameters of diastolic function and left ventricular filling pressure during acute ischemia.

The relationship between left ventricular filling pressure and Doppler echocardiographic parameters of diastolic mitral flow (MF) was evaluated in patients with ischemic heart disease during acute ischemia induced by percutaneous transluminal coronary angioplasty (PTCA) of the left anterior descending artery. Thirty-two patients were examined by simultaneous recordings of the Doppler MF signal and the mean pulmonary capillary wedge pressure (PCm) as an approximation of left ventricular filling pressure. At rest PCm was correlated with the early/late velocity integral ratio (Ei/Ai: r = 0.62: p less than 0.0001; n = 32). In 25 of 32 patients the recordings during PTCA could be evaluated. At the end of the inflation (duration: 69 +/- 24 seconds) PCm increased from 11.2 +/- 5.5 to 17.2 +/- 7.2 mm Hg (p less than 0.001), and total MF integral as an index of systolic ventricular function decreased by 14.9 +/- 12.8% (p less than 0.001). Inasmuch as both early and late velocity integrals were reduced during PTCA, the Ei/Ai ratio did not change significantly (1.41 +/- 0.51 to 1.34 +/- 0.60; NS). In a subgroup of inflations without ECG signs of ischemia, Ei was decreased without a concomitant decrease in Ai, thus leading to a decrease in the Ei/Ai ratio (1.36 +/- 0.43 to 1.17 +/- 0.31; p less than 0.05). Summarizing the events during PTCA, a steady increase in PCm was observed, whereas the Ei/Ai ratio was slightly decreased. Thus the observation at rest that an elevated PCm was associated with an elevated Ei/Ai was no longer valid during PTCA (Ei/Ai: r = 0.28; NS). A significant correlation was found between parameters of Doppler MF and PCm in patients with ischemic heart disease at rest. During PTCA this relationship was attenuated. Therefore noninvasive assessment of left ventricular filling pressures during acute ischemia by Doppler echocardiography does not seem feasible.

Adult↗

PubMed1990

[Doppler echocardiography determination of systolic and diastolic function in sequential and ventricular stimulation].

In 16 patients with sequential pacing and partly impaired left-ventricular function (mean shortening fraction 23 +/- 7%), the flow through the mitral and aortic valves were studied with Doppler echocardiography at different AV-intervals, keeping heart rate constant at 70/min. The time-velocity integral of the early and late diastolic filling, the first one-third filling fraction, and the diastolic-filling time were found to be significantly dependent on the length of the AV interval (p less than 0.001). In the left ventricular outflow tract, the maximum stroke volume of 85.6 +/- 28.4 ml was measured at an AV interval of 200 ms. The stroke volume under VOO stimulation (70.5 +/- 24.1 cm) was 17% less (p less than 0.003). There was no correlation between the increase in stroke volume during sequential pacing and M mode or Doppler echocardiographic parameters. Thus, the haemodynamic benefit of sequential pacing cannot be predicted by echocardiography. Doppler echocardiography is useful for determining the AV interval leading to the maximal cardiac output at rest. In the Doppler echocardiographic assessment of left-ventricular function, the influence of the AV interval on diastolic-filling parameters must be considered.

Adult↗

PubMed1990

[Doppler echocardiography evaluation of left ventricular function in intra-aortic balloon counterpulsation].

Doppler-echocardiographic measurement of transaortic and mitral flow allows an assessment of systolic and diastolic left ventricular performance. To evaluate the hemodynamic effects of intra-aortic balloon counterpulsation (IABP) 10 patients were examined during IABP after myocardial infarction or cardiothoracic surgery. Doppler echocardiographic transaortic (VAo), early (VE) and late (VA) transmitral flow velocities, transaortic velocity time integral (VTIAo), acceleration and deceleration intervals and rates were obtained. The IABP augmentation was changed from 1:1, 1:2 to 1:4 causing no notable change in invasively measured arterial pressures (p greater than 0.05). With constant heart rate the VE/VA ratio was similar in 1:2 and 1:1 mode (1.44 +/- 0.42 vs 1.47 +/- 0.27; p greater than 0.2), whereas VAo and VTIAo were increased (p less than 0.01). A beat-to-beat analysis during 1:2 mode confirmed an increase in VAo (84.1 +/- 13.5 vs 98.3 +/- 16.5 cm/s; p less than 0.01) and VTIAo after the augmenting balloon inflation, but did not confirm any concomitant effect on diastolic transmitral parameters; acceleration and deceleration intervals were not changed. Thus, Doppler-echocardiography was able to detect an increase in transaortic flow during IABP augmentation by beat-to-beat analysis. The increase in VTIAo indicates an elevated cardiac output. A similar instantaneous effect on the diastolic transmitral flow could not be identified.

Blood Flow Velocity↗

PubMed1990

[Estimated relation of Doppler echocardiography parameters of diastolic ventricular function and pulmonary capillary pressure in acute ischemia].

A close relation between the Doppler-echocardiographic transmitral flow signal (TMF) and the left ventricular filling pressure in patients with coronary heart disease (CHD) was described in several reports. The present study investigated the validity of this relation during an episode of acute ischemia induced by coronary angioplasty (PTCA) by simultaneous recording of TMF and mean pulmonary capillary wedge pressure (PCm). Thirty-nine patients were examined at rest, and 33 of them were further studied during a subsequent PTCA of the left anterior descending artery (n = 22) or the right coronary artery (n = 11). The onset of ischemia was evaluated by electrocardiography. The Doppler-echocardiographic parameters of diastolic ventricular function were correlated with PCm; the closest correlation was obtained for the relation between PCm and the ratio of the early/atrial velocity integral (Ei/Ai: r = 0.59; p less than 0.0001), and between PCm and the relative share of the early diastolic velocity integral (Ei%: r = 0.58; p less than 0.0001). A wide confidence interval of individual values did not allow a calculation of PCm from Ei/Ai. By a semiquantitative approach an elevated PCm could be estimated from Ei/Ai greater than 1.5 with a high sensitivity (86%) and specificity (81%). During PTCA an increase of PCm was observed (start: 10.2 +/- 4.8; end: 15.0 +/- 6.5; p less than 0.0001), while Ei/Ai decreased slightly (start: 1.37 +/- 0.41; end: 1.27 +/- 0.51; p = 0.32). With increasing duration of inflation, the correlation between PCm and Doppler-echocardiographic parameters was attenuated.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗

PubMed1989

[Acute myocardial infarct caused by nicotine-induced erythrocytosis].

A 29-year-old heavy smoker presented with an acute myocardial infarction and hematocrit of 70%. At immediate coronary angiography a complete occlusion of the right coronary artery was found. After intracoronary urokinase the coronary arteries were found to be completely normal. Causes for the erythrocytosis other than smoking could be excluded. We conclude that thrombotic coronary occlusion with acute myocardial infarction was caused by erythrocytosis due to heavy smoking.

Adult↗

PubMed1987

[Doppler echocardiographic findings in hypertrophic cardiomyopathy].

This study was performed to evaluate diastolic and systolic flow parameters in patients with hypertrophic cardiomyopathy as assessed by Doppler echocardiography. We examined 45 patients with hypertrophic cardiomyopathy (35 of which had an obstruction) and compared the results of diastolic and systolic measurements with those of two groups of normals (less than 25 years, n = 15; greater than 40 years, n = 10). For the diastolic parameters the isovolumetric relaxation time showed a significant prolongation with 107 +/- 23 ms as compared to normals (greater than 40 years) with 86 +/- 10 ms. No differences were found for the time-to-peak velocity in early diastole. The ratio of the time-velocity-integrals of early and late diastolic filling (E/A) with 2.4 +/- 1.3 was significantly lower as compared to young normals with 4.0 +/- 1.9 but not for the group of normals greater than 40 years with 2.5 +/- 1.0. The time-to-peak velocity in systole (TPVS) of the left ventricular outflow was prolonged in patients with an intracavitary obstruction, and the ratio of TPVS/LVET significant lower as compared to normals. Pressure gradients measured with Doppler showed good correlations to invasive measurements with an r = 0.88, SEE 28.5 mmHg. In color-coded Doppler echocardiography turbulent flow is portrayed as a color-mosaic. The location of turbulence in the outflow tract as well as an accompanying mitral insufficiency are immediately visible, but color-flow Doppler does not allow for quantifying the degree of an obstruction. Conventional and color-coded Doppler echocardiography is an enhancement of noninvasive diagnostics also in hypertrophic cardiomyopathy with respect to the assessment of pathologically changed systolic and diastolic flow parameters, the localization and quantification of an obstruction and the assessment and semiquantification of an concomitant mitral regurgitation.

Adolescent↗

PubMedDate not supplied

Coronary flow analysis during autoperfusion angioplasty.

BACKGROUND: Autoperfusion balloons are available for the protection of the myocardium during balloon angioplasty. The aortic pressure is the driving force that delivers blood to the distal vessel during balloon inflation. Autoperfusion balloons can achieve sufficient flow rates in vitro. The use of these devices is recommended in high-risk patients in danger of haemodynamic collapse during balloon inflation. The quantity of the distal blood flow during balloon inflation in vivo is still unknown. OBJECTIVES: To measure distal coronary perfusion using Doppler guidewires during percutaneous transluminal coronary angioplasty (PTCA) with autoperfusion balloons. METHODS: Coronary flow velocity was measured with 0.014-inch Doppler guidewires bypassing the autoperfusion balloon in eight patients undergoing elective PTCA (degree of stenosis 74 +/- 7.2%). We used balloons with diameters of 3.0 and 3.5 mm. The coronary diameter at the location of the flow measurements was obtained by quantitative angiography in two planes. Coronary blood flow was calculated as the luminal area multiplied by the average peak flow velocity of the Doppler wire divided by 2. Coronary flow velocity reserve was measured before and after angioplasty by intracoronary injection of adenosine. RESULTS: Coronary blood flow was 35 +/- 11.6 ml/min before PTCA. During average inflation times of 4.6 +/- 0.9 min, coronary blood flow was 19 +/- 3.8 ml/min (P = 0.002) after withdrawing the guidewire in the autoperfusion balloon. Five minutes after angioplasty it increased to 42 +/- 13.5 ml/min (P < 0.001). Four patients had electrocardiographic changes during balloon inflation; three patients reported chest pain. One patient required a stent because of a local dissection. To achieve satisfactory angiographic results (residual stenosis 11 +/- 8.5%), we performed 2.1 +/- 0.78 inflations on average with a cumulative inflation time of 8.8 +/- 3.35 min. Coronary flow velocity reserve increased from 1.3 +/- 0.20 to 2.2 +/- 0.22 (P < 0.001). CONCLUSIONS: Using the autoperfusion balloon we measured a coronary blood flow during angioplasty of 56 +/- 10.3% of the distal perfusion before PTCA. In high-risk patients dependent on adequate coronary perfusion, autoperfusion balloons are not able to provide sufficient distal coronary blood flow during balloon inflation. In these patients active coronary or circulatory support devices are recommended.

Aged↗