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Biomedical subjects

O Kamp

Publications and source records attributed to O Kamp.

At least 19 recordsLinked to original sources
PubMed2006

Comparison of the haemodynamics of different pacing sites in patients undergoing resynchronisation treatment: need for individualisation of lead localisation.

BACKGROUND: Biventricular pacing is a new therapy for the treatment of heart failure. However, a substantial number of patients do not respond to this therapy. HYPOTHESIS: Individually determined maximal pacing sites will improve the haemodynamic response and increase the number of responders. METHODS: In 48 patients with heart failure, the acute haemodynamic effects of nine different pacing configurations were studied, using two right and left ventricular pacing sites and their combinations. Cardiac index was measured using Doppler echocardiography. For further analysis, the combination with the highest cardiac index improvement was compared with baseline. Moreover, the number of responders was calculated using a cut-off value of 10% increase in cardiac index. RESULTS: The mean (SD) increase in cardiac index ranged between 3.8% (6.0%) and 11.1% (8.6%). The pacing site with maximal cardiac index was highly variable between patients, and here the cardiac index increased to 14.8% (7.6%; (p<0.001). The number of responders varied between 15% and 64%, increasing to 75% at the site with maximal increase in cardiac index. In a subset of patients, the haemodynamic improvement after pacemaker implantation correlated well with the acute haemodynamics. CONCLUSION: Individualisation of pacing configuration for biventricular pacing leads to further haemodynamic improvement in patients with heart failure and reduces the number of patients not responding to this therapy.

Adult↗
PubMed2006

Aggressive antihypertensive strategies based on hydrochlorothiazide, candesartan or lisinopril decrease left ventricular mass and improve arterial compliance in patients with type II diabetes mellitus and hypertension.

We investigated the effects of aggressive antihypertensive therapy based on hydrochlorothiazide, candesartan or lisinopril on left ventricular mass (LVM) index and arterial stiffness in hypertensive type II diabetic individuals. Seventy hypertensive type II diabetic individuals were treated with three antihypertensive strategies in a randomized, double-blind, double-dummy design. Blood pressure was titrated to levels below 130/85 mm Hg or a decrease in systolic pressure of 10% with a diastolic pressure below 85 mm Hg. After titration, patients were treated for 12 months. Mean blood pressures were 157/93, 151/94 and 149/93 mm Hg at baseline in the hydrochlorothiazide (n = 24), candesartan (n = 24) and lisinopril (n = 22) groups, and 135/80, 135/82 and 131/80 mm Hg after titration. About 70% reached target blood pressures, with the median use of three antihypertensive drugs. Left ventricular mass index and all estimates of arterial stiffness showed significant improvement after 12 months: that is, LVM index (-11 g/m(2); -8%); carotid distensibility coefficient (DC; +2.8 x 10(-3) kPa(-1); +27%), compliance coefficient (CC; +0.13 mm2/kPa; +21%) and elastic modulus (-0.19 kPa; -16%); femoral DC (+1.6 x 10(-3) kPa(-1); +50%) and CC (+0.08 mm2/kPa; +26%); brachial DC (+2.1 x 10(-3) kPa(-1); +39%) and CC (+0.03 mm2/kPa; +27%) and total systemic arterial compliance (+0.29 ml/mm Hg; +16%). No differences in outcome variables between treatment groups were observed. Aggressive antihypertensive treatment, although difficult to achieve, resulted in substantial reductions of LVM index and arterial stiffness in relatively uncomplicated hypertensive type II diabetic individuals. Strategies based on renin-angiotensin system inhibitors were not clearly superior to conventional (i.e. diuretic-based) strategies.

Adult↗
PubMed2006

Transient permeabilization of cell membranes by ultrasound-exposed microbubbles is related to formation of hydrogen peroxide.

In the present study, we addressed the interactions among ultrasound, microbubbles, and living cells as well as consequent arising bioeffects. We specifically investigated whether hydrogen peroxide (H(2)O(2)) is involved in transient permeabilization of cell membranes in vitro after ultrasound exposure at low diagnostic power, in the presence of stable oscillating microbubbles, by measuring the generation of H(2)O(2) and Ca(2+) influx. Ultrasound, in the absence or presence of SonoVue microbubbles, was applied to H9c2 cells at 1.8 MHz with a mechanical index (MI) of 0.1 or 0.5 during 10 s. This was repeated every minute, for a total of five times. The production of H(2)O(2) was measured intracellularly with CM-H(2)DCFDA. Cell membrane permeability was assessed by measuring real-time changes in intracellular Ca(2+) concentration with fluo-4 using live-cell fluorescence microscopy. Ultrasound, in the presence of microbubbles, caused a significant increase in intracellular H(2)O(2) at MI 0.1 of 50% and MI 0.5 of 110% compared with control (P < 0.001). Furthermore, we found increases in intracellular Ca(2+) levels at both MI 0.1 and MI 0.5 in the presence of microbubbles, which was not detected in the absence of extracellular Ca(2+). In addition, in the presence of catalase, Ca(2+) influx immediately following ultrasound exposure was completely blocked at MI 0.1 (P < 0.01) and reduced by 50% at MI 0.5 (P < 0.001). Finally, cell viability was not significantly affected, not even 24 h later. These results implicate a role for H(2)O(2) in transient permeabilization of cell membranes induced by ultrasound-exposed microbubbles.

Animals↗
PubMed2005

Adverse reactions to ultrasound contrast agents: is the risk worth the benefit?

The introduction of ultrasound contrast agents has led to a marked improvement in diagnostic capabilities in echocardiography. As no serious adverse events were seen during the preclinical development phase, ultrasound contrast agents were thought to be safe. Recently, three fatal and 19 severe, non-fatal adverse reactions were reported in a post marketing analysis of more than 150,000 studies of Sonovue, which has led to the addition of several contra-indications for the use of this ultrasound contrast agent. Although a strong relationship was established between the non-fatal cases and administration of Sonovue, a causal relationship between the fatal cases and the use of Sonovue is debatable. Therefore, the risk associated with the use of this ultrasound contrast agent should be judged carefully, taking into consideration the prevalence of adverse effects of other contrast media and diagnostic procedures used in cardiology.

Contrast Media↗
PubMed2004

Microbubbles and ultrasound: from diagnosis to therapy.

The development of ultrasound contrast agents, containing encapsulated microbubbles, has increased the possibilities for diagnostic imaging. Ultrasound contrast agents are currently used to enhance left ventricular opacification, increase Doppler signal intensity, and in myocardial perfusion imaging. Diagnostic imaging with contrast agents is performed with low acoustic pressure using non-linear reflection of ultrasound waves by microbubbles. Ultrasound causes bubble destruction, which lowers the threshold for cavitation, resulting in microstreaming and increased permeability of cell membranes. Interestingly, this mechanism can be used for delivery of drugs or genes into tissue. Microbubbles have been shown to be capable of carrying drugs and genes, and destruction of the bubbles will result in local release of their contents. Recent studies demonstrated the potential of microbubbles and ultrasound in thrombolysis. In this article, we will review the recent advances of microbubbles as a vehicle for delivery of drugs and genes, and discuss possible therapeutic applications in thrombolysis.

Contrast Media↗
PubMed2003

[Diastolic heart failure].

Diastolic heart failure is predominantly a disease of the elderly: at the age of 70 years, almost half of all patients with heart failure have diastolic heart failure. Hypertension and obesity are common underlying disorders in patients with diastolic heart failure. Patients with diastolic heart failure have an equal, or only slightly better, prognosis in terms of mortality compared to patients with systolic heart failure. Echocardiography can distinguish diastolic heart failure from systolic heart failure. Patients with heart failure and a normal ejection fraction almost certainly have a diastolic dysfunction. There is a lack of reliable data about the optimal medicinal treatment strategy for patients with diastolic heart failure. Angiotensin-converting enzyme (ACE) inhibitors, beta-blockers, and (non-dihydropyridine) calcium antagonists have therapeutic potential. Digoxin may be contraindicated.

Adrenergic beta-Antagonists↗
PubMed2003

Successful percutaneous extraction of an inadvertently placed left ventricular pacing lead.

A 74-year-old patient was referred for a rapidly increasing pacing threshold 9 months after DDD pacemaker implantation because of symptomatic total atrioventricular (AV) block. She had a history of hypertension, diabetes with micro-angiopathy and a recent transient ischaemic attack. The paced electrocardiogram on admission had a right bundle branch block pattern and 3-dimensional transoesophageal echocardiography demonstrated passage of the lead through an atrial septal defect with a left ventricular position in addition to moderate atherosclerosis of the ascending aorta. No thrombus could be detected on the lead. Percutaneous extraction is usually not recommended because of the risk of mobilization of thrombus material. However, the risk of stroke during removal using cardiopulmonary bypass in this patient was considerably increased because of the presence of multiple independent risk factors. Therefore, percutaneous extraction using a locking device was selected and performed without complications: follow-up was uneventful.

Aged↗
PubMed2002

Assessment of the left atrial appendage mechanical function by three-dimensional echocardiography.

AIMS: We evaluated the feasibility of three-dimensional echocardiography, in the assessment of left atrial appendage (LAA) function. METHODS AND RESULTS: Forty-five patients underwent multiplane transoesophageal echocardiography. In addition to Doppler and two-dimensional echocardiography, data for three-dimensional echocardiography reconstruction were obtained during transoesophageal echocardiography. Left atrial appendage ejection fraction based on three-dimensional echocardiography volume measurements (EFv) and two-dimensional echocardiography area measurements (EFa), coupled with other echocardiographic data, were related to left atrial appendage late peak emptying velocity, a frequently used indicator of left atrial appendage function. Multiple regression analysis has revealed a significant association of peak emptying velocity with EFv (P<0.0001), spontaneous echocardiographic contrast (P=0.001), tricuspid regurgitation (P=0.03) and left ventricular hypertrophy (P=0.05). No significant relation was observed between peak emptying velocity and EFa, presence or absence of atrial fibrillation, left ventricular dysfunction, mitral stenosis and insufficiency, left atrial dilatation, pulmonary venous peak systolic, diastolic and peak reverse flow velocity at atrial contraction as well as left atrial appendage volumes derived from two-dimensional echocardiography and three-dimensional echocardiography. In a simple linear correlation, the degree of association between peak emptying velocity and EFv was higher as between peak emptying velocity and EFa (r=0.7 vs 0.4, both P<0.001). Observer variabilities for calculating EFv were considerably lower than for two-dimensional echocardiography derived EFa. Ejection fractions determined by two-dimensional echocardiography area measurements at 45 degrees, 90 degrees and 135 degrees cutplane angulations were related to EFv only at 135 degrees. CONCLUSIONS: Left atrial appendage ejection fraction calculation by three-dimensional echocardiography is feasible, more accurate than by two-dimensional echocardiography and has lower observer variability. Furthermore, an optimal cutplane angulation of the left atrial appendage view at 135 degrees has been demonstrated.

Adult↗
PubMed2002

Myocardial viability: impact on left ventricular dilatation after acute myocardial infarction.

OBJECTIVE: To evaluate whether the presence of viable myocardium, detected by low dose dobutamine echocardiography, limits the likelihood of left ventricular dilatation in patients with acute myocardial infarction. PATIENTS: 107 patients were studied by low dose dobutamine echocardiography at (mean (SD)) 3 (1) days after acute myocardial infarction. Cross sectional echocardiography was repeated three months later. Patients were divided in two groups based on the presence (n = 47) or absence (n = 60) of myocardial viability. RESULTS: Baseline characteristics were comparable between the two groups, except for infarct location. Left ventricular end diastolic volume index (EDVI) was stable in patients with viability, but end systolic volume index (ESVI) decreased significantly (p = 0.006). Patients without viability had a significant increase in both EDVI (p < 0.0001) and ESVI (p = 0.0007). Subgroup analysis in patients with small and large infarcts (peak creatine kinase < or = 1000 v > 1000 IU/l) showed that ventricular dilatation occurred only in patients with large infarcts without viability. This resulted in larger ESVI values at three months in that group compared with patients with large infarcts plus viability (p < 0.05). Multivariate regression analysis identified myocardial viability as an independent predictor of left ventricular dilatation, along with wall motion score index on low dose dobutamine echocardiography and the number of pathological Q waves. CONCLUSIONS: The presence of viability early after acute myocardial infarction is associated with preservation of left ventricular size, whereas the absence of viability results in ventricular dilatation, particularly in large infarcts.

Cardiac Volume↗
PubMed2002

Early prediction of improvement in ejection fraction after acute myocardial infarction using low dose dobutamine echocardiography.

OBJECTIVE: To evaluate the relation between changes in ejection fraction during the first three months after acute myocardial infarction and myocardial viability. PATIENTS: Myocardial viability was assessed using low dose dobutamine echocardiography in 107 patients at mean (SD) 3 (1) days after acute myocardial infarction. Cross sectional echocardiography was repeated three months later. Left ventricular volumes and ejection fraction were determined from apical views using the Simpson biplane formula. RESULTS: In patients with viability, ejection fraction increased by 4.4 (4.3)%; in patients without viability it remained unchanged (0.04 (3.6)%; p < 0.001). A > or = 5% increase in ejection fraction was present in 21 of 107 patients (20%). Receiver operating characteristic analysis showed that myocardial viability in > or = 2 segments predicted this increase in ejection fraction with a sensitivity of 81% and a specificity of 65%. Multivariate logistic regression analysis was used to define which clinical and echocardiographic variables were related to > or = 5% improvement in ejection fraction. Myocardial viability, non-Q wave infarction, and anterior infarction all emerged as independent predictors, myocardial viability being the best (chi(2) = 14.5; p = 0.0001). Using the regression equation, the probability of > or = 5% improvement in ejection fraction for patients with a non-Q wave anterior infarct with viability was 73%, and for patients with a Q wave inferior infarct without viability, only 2%. CONCLUSIONS: Myocardial viability after acute myocardial infarction is the single best predictor of improvement in ejection fraction. In combination with infarct location and Q wave presence, the probability of > or = 5% improvement can be estimated in individual patients at the bedside.

Cardiotonic Agents↗
PubMed2001

Predictive value of markers of myocardial reperfusion in acute myocardial infarction for follow-up left ventricular function.

This study evaluated recently suggested invasive and noninvasive parameters of myocardial reperfusion after acute myocardial infarction (AMI), assessing their predictive value for left ventricular function 4 weeks after AMI and reperfusion defined by myocardial contrast echocardiography (MCE). In 38 patients, angiographic myocardial blush grade, corrected Thrombolysis In Myocardial Infarction frame count, ST-segment elevation index, and coronary flow reserve (n = 25) were determined immediately after primary percutaneous transluminal coronary angioplasty (PTCA) for first AMI, and intravenous MCE was determined before, and at 1 and 24 hours after PTCA to evaluate myocardial reperfusion. Results were related to global wall motion index (GWMI) at 4 weeks. MCE 1 hour after PTCA showed good correlation with GWMI at 4 weeks (r = 0.684, p <0.001) and was in an analysis of variance the best parameter to predict GWMI 4 weeks after AMI. The ST-segment elevation index was close in its predictive value. Considering only invasive parameters of reperfusion myocardial blush grade was the best predictor of GWMI at 4 weeks (R(2) = 0.3107, p <0.001). A MCE perfusion defect size at 24 hours of > or =50% of the MCE perfusion defect size before PTCA was used to define myocardial nonreperfusion. In a multivariate analysis, low myocardial blush grade class was the best predictor of nonreperfusion defined by MCE. Thus, intravenous MCE allows better prediction of left ventricular function 4 weeks after AMI than other evaluated parameters of myocardial reperfusion. Myocardial blush grade is the best predictor of nonreperfusion defined by MCE and is the invasive parameter with the greatest predictive value for left ventricular function after AMI. Coronary flow parameters are less predictive.

Aged↗
PubMed2001

In-hospital and long-term prognostic value of viable myocardium detected by dobutamine echocardiography early after acute myocardial infarction and its relation to indicators of left ventricular systolic dysfunction.

The prognostic value of myocardial viability early after acute myocardial infarction (AMI) is still controversial, depending on the patient under study and the outcome end point considered. Furthermore, the relative prognostic importance of viability compared with indicators of systolic left ventricular (LV) dysfunction is not known. One hundred thirty-eight patients were studied with low-dose dobutamine echocardiography 3 +/- 1 days after AMI. Patients were divided in 2 groups based on presence (n = 55) or absence (n = 83) of myocardial viability and followed up for in-hospital and late cardiac events. During hospitalization, myocardial viability was the only independent predictor for recurrent ischemic events (chi-square 5.0, p = 0.025). End-systolic volume index and ejection fraction were both independent predictors of the occurrence of heart failure, whereas gender and end-systolic volume index emerged as independent predictors of hard cardiac events (death and sustained ventricular tachycardia). After hospital discharge, patients were followed for 19 +/- 7 months. Again, myocardial viability emerged as the only independent predictor of unstable angina (chi-square 7.7, p = 0.005). Age, hypertension, and ejection fraction were the most important independent predictors of hospitalization for heart failure, whereas ejection fraction was the only independent predictor of hard cardiac events. Presence of myocardial viability early after AMI is the single best predictor of recurrent in-hospital ischemic events and unstable angina after discharge. With respect to hard cardiac events and occurrence of heart failure, indicators of LV systolic dysfunction have a higher prognostic value than presence of myocardial viability.

Adrenergic beta-Agonists↗
PubMed2001

Granulocyte-macrophage colony-stimulating factor (GM-CSF) decreases left ventricular function. An echocardiographic study in cancer patients.

To study the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on the heart, echocardiographic assessments of left ventricular (LV) end-diastolic and end-systolic (ES) diameters (D), ejection fraction (EF) and cardiac output (CO) were done in six male patients (28-70 years of age) with advanced sarcoma (Group 1), prior to (day -1-0), during (day 7-9) and after (day 20-21) a first course of i.v. doxorubicin (day 0) without GM-CSF and a second course (3 weeks after the first one) with GM-CSF 250 microg/m(2)subcutaneously and daily from day 1-11. A similar study was done in ten female patients with advanced breast cancer (31-58 years of age, Group 2) for a first course of doxorubicin+cyclophosphamide with GM-CSF (same schedule as in Group 1). As compared to the mean of values prior to and after the course with GM-CSF in Group 1 and 2, the LVESD during GM-CSF administration transiently increased by median 6% (range -19 to 30%, P<0.05) vs -9% (-21 to 6%, not significant) in the first course without GM-CSF in Group 1 (P<0.05 between courses). The CO and EF tended to decrease during GM-CSF. GM-CSF thus causes a small and transient decrease of LV contractility.

Adult↗
PubMed2001

Serial evaluation of perfusion defects in patients with a first acute myocardial infarction referred for primary PTCA using intravenous myocardial contrast echocardiography.

AIMS: To investigate whether myocardial contrast echocardiography using Sonazoid could be used for the serial evaluation of the presence and extent of myocardial perfusion defects in patients with a first acute myocardial infarction treated with primary PTCA, and specifically, (1) to evaluate safety and efficacy of myocardial contrast echocardiography to detect TIMI flow grade 0--2, (2) to evaluate the success of reperfusion and (3) to predict left ventricular recovery after 4 weeks follow-up. METHODS AND RESULTS: Fifty-nine patients underwent serial myocardial contrast echocardiography, immediately before primary PTCA (MCE1), 1 h (MCE2) and 12--24 h after PTCA (MCE3). A perfusion defect was observed in 21 of 24 patients (88%) with anterior acute myocardial infarction. All but one had TIMI flow grade 0--2 prior to PTCA. Nine of 31 patients (29%) with inferior acute myocardial infarction showed a perfusion defect and all had TIMI flow grade 0-2 prior to PTCA. Restoration of TIMI flow grade 3 was achieved in 73% of the patients by primary PTCA. A reduction in size of the initial perfusion defect of at least one segment (16 segment model) or no defect vs persistent defect in patients with anterior acute myocardial infarction was associated with improved global left ventricular function at 4 weeks; mean global wall motion score index 1.29+/-0.21 vs 1.66+/-0.31 (P=0.009). Multiple regression analysis in patients with an anterior acute myocardial infarction revealed that the extent of the perfusion defect at MCE3 was a significant (P=0.0005) independent predictor for left ventricular recovery at 4 weeks follow-up. The only other independent predictor was TIMI flow grade 3 post PTCA (P=0.007). CONCLUSION: Intravenous myocardial contrast echocardiography immediately prior to primary PTCA seems safe and is capable of detecting the presence of a perfusion defect and its subsequent dynamic changes, particularly in patients with a first anterior acute myocardial infarction. A significant reduction in size of the initial perfusion defect using serial myocardial contrast echocardiography predicts functional recovery after 4 weeks and these findings underscore the potential diagnostic value of intravenous myocardial contrast echocardiography.

Aged↗
PubMed2001

Differences in pacing from the atrial appendage and the lateral atrial free wall on left ventricular filling and haemodynamics during DDD pacing.

INTRODUCTION: Atrioventricular sequential pacing involves stimulation from electrodes in the right atrium, generally the atrial appendage (RAA) and the right ventricular apex. The appendage, however, may be unsuitable if a stable position cannot be achieved. The aim of this study was to assess the haemodynamic consequences of different atrial stimulation sites during DDD pacing. METHODS: In 12 consecutive patients (mean age 67 +/- 7 years) who underwent DDD pacemaker implantation, an additional temporary bipolar pacing electrode was positioned on the right atrial free wall. Pacing was performed alternating from the two locations at 85, 100 and 120 beats per minute (bpm). Paced atrioventricular delay was set at 180 ms. Cardiac output and mitral inflow measurements were performed using Doppler echocardiography. RESULTS: Pacing at 85 and 100 bpm resulted in a significantly higher A-peak velocity from the RAA compared with the right atrial free wall. Cardiac index was consistently higher from the RAA location (2.4 +/- 1.2 vs 2.1 +/- 0.91. min-1 m-2 at 85 bpm, 2.71 +/- 1.4 vs 2.35 +/- 1.11. min-1 m-2 at 100 bpm and 2.94 +/- 1.5 vs 2.61 +/- 1.41. min-1 m-2 at 120 bpm, P < 0.05). CONCLUSION: Stimulation from the RAA was superior to stimulation from the right atrial free wall with respect to left ventricular filling and cardiac output. Compared with stimulation from the right atrial free wall, RAA pacing resulted in an increase of 10-15% in cardiac output.

Aged↗