Biomedical subjects
Publications and source records attributed to Christian Knackstedt.
Mitral valve prolapse usually has a good prognosis. However, an association between mitral valve prolapse and atrial and ventricular arrhythmias has been described. This case presents a patient who was admitted after cardiac resuscitation due to ventricular fibrillation. A severe mitral valve prolapse was the only pathology found.
BACKGROUND: Left ventricular lead implantation for cardiac resynchronization therapy (CRT) usually requires a pre- or intraprocedural occlusion contrast venography of the coronary sinus (CS) in order to identify tributaries to the lateral wall. As many patients undergo a preprocedural coronary angiogram, we investigated the diagnostic accuracy of venous phase imaging of the CS in patients prior to CRT implantation. The aim of this study was to assess the quality of venous phase coronary sinus angiography. METHODS: In 24 CRT patients retrograde occlusion venography and venous phase coronary sinus angiography obtained during coronary angiography were compared with respect to image quality, vessel diameters and the ability to identify a coronary sinus side branch suitable for left ventricular lead placement. RESULTS: Suitable target vessels for left ventricular lead implantation were identified in all patients irrespective of the method (retrograde occlusion venography or venous phase coronary sinus angiography). There was a high concordance in vessel diameters between venous phase and retrograde angiography. Visibility was superior in retrograde venography. CONCLUSIONS: In heart failure patients who are scheduled for coronary angiograms venous phase coronary sinus angiography is a time-saving and easy to perform alternative imaging modality. Radiation exposure and the amount of contrast medium needed is reduced as compared to coronary sinus occlusion angiography. The information obtained thereby may be used to plan subsequent CRT implantation without the need for retrograde coronary sinus angiography.
Explore the source record for details and available documents.
BACKGROUND: Pre-interventional three-dimensional (3D) reconstruction of the heart by CT or MRI provides important information on cardiac anatomy for electrophysiological interventions. However, updates of 3D-imaging modalities with high soft-tissue contrast are not available during ablation procedures. OBJECTIVE: We describe the development and first clinical testing of a close to real-time visualization of cardiac anatomy by intracardiac echocardiography (ICE). METHODS: An electronic phased-array 5-10 MHz ICE-catheter (AcuNav/Siemens/64 elements) was inserted via a straightened femoral vein sheath (12F) and placed in the right atrium in 5 pigs. A custom-made prototype stepper motor allowed automatic rotation around the longitudinal axis from 90 degrees to 360 degrees in 2-5 degrees steps. For every plane 2D images of a complete cardiac cycle were acquired, triggered by respiration and ECG. The ultrasound images were digitized and 3D-reconstruction was performed by a prototype software. After experimental validation the system was tested in 6 patients during electrophysiological studies. RESULTS: From a single location in the right atrium, 3D-acquisition and reconstruction of both atria and ventricles with good image quality were achieved within 3-5 minutes. Doppler-mode facilitated identification of the great vessels including the pulmonary veins and their entry into the heart. 3D-visualization of ablation catheters was also possible in all patients and pigs. CONCLUSION: Semi-automated 3D intracardiac echocardiography from a single site inside the right atrium provides the electrophysiologist with a detailed image of both atria and ventricles with repeated updates of the cardiac anatomy.
Explore the source record for details and available documents.
INTRODUCTION: Because of the proximity of the esophagus to the heart, transesophageal defibrillation might increase defibrillation success. We assessed the defibrillation threshold (DFT) of transesophageal defibrillation compared with standard transthoracic defibrillation. METHODS: Defibrillation success and DFTs were determined in 22 female pigs with high (68+/-4 kg, n=12) or low body weight (39+/-1 kg, n=10). After induction of ventricular fibrillation, biphasic shocks were delivered between two cutaneous patch electrodes (sternal and apical position) or between an esophageal and two cutaneous patch electrodes in a sternal and apical position. The esophageal electrode was integrated into a latex sheath covering a standard transesophageal echocardiography probe. RESULTS: In 5 of 12 pigs with high body weight, external defibrillation failed despite 3 consecutive 200-J shocks, whereas subsequent transesophageal defibrillation was successful with the first shock. In the remaining 7 pigs, a more than 50% reduction in DFT was obtained with transesophageal defibrillation compared with standard biphasic external defibrillation (67+/-27 vs 164+/-23 J, P<.001). Pigs with lower body weight were successfully defibrillated by both transthoracic and transesophageal shocks. The DFT in pigs with low body weight was significantly lower using transesophageal defibrillation compared with transthoracic shocks (65+/-15 vs 99+/-38 J, P<.05). CONCLUSIONS: In this animal model, nonresponders to standard external defibrillation could successfully be defibrillated via an esophageal-cutaneous electrode configuration. Overall, an almost 50% DFT reduction was achieved by transesophageal defibrillation. Transesophageal defibrillation may provide an additional tool for terminating VF, which is refractory to external defibrillation, eg, in patients with very high body weight.
The purpose was to evaluate a new semi-automated 3D region-growing segmentation algorithm for functional analysis of the left ventricle in multislice CT (MSCT) of the heart. Twenty patients underwent contrast-enhanced MSCT of the heart (collimation 16 x 0.75 mm; 120 kV; 550 mAseff). Multiphase image reconstructions with 1-mm axial slices and 8-mm short-axis slices were performed. Left ventricular volume measurements (end-diastolic volume, end-systolic volume, ejection fraction and stroke volume) from manually drawn endocardial contours in the short axis slices were compared to semi-automated region-growing segmentation of the left ventricle from the 1-mm axial slices. The post-processing-time for both methods was recorded. Applying the new region-growing algorithm in 13/20 patients (65%), proper segmentation of the left ventricle was feasible. In these patients, the signal-to-noise ratio was higher than in the remaining patients (3.2+/-1.0 vs. 2.6+/-0.6). Volume measurements of both segmentation algorithms showed an excellent correlation (all P<or=0.0001); the limits of agreement for the ejection fraction were 2.3+/-8.3 ml. In the patients with proper segmentation the mean post-processing time using the region-growing algorithm was diminished by 44.2%. On the basis of a good contrast-enhanced data set, a left ventricular volume analysis using the new semi-automated region-growing segmentation algorithm is technically feasible, accurate and more time-effective.
OBJECTIVES: This study was designed to develop a technique to selectively increase the sympathetic tone to the heart by cardiac sympathetic nerve stimulation (SNS). BACKGROUND: Access to the cardiac sympathetic neurons may allow modulating the adrenergic tone of the heart while avoiding systemic side effects. METHODS: Cardiac sympathetic nerves course within neural sleeves along the subclavian artery. Because of this proximity, transvascular SNS was attempted with electrode catheters inside the subclavian artery in 16 pigs. RESULTS: Right/left (R-/L-) SNS (20 Hz) during ventricular pacing at 200/min evoked a >100% increase of left ventricular systolic pressure (baseline: 51 +/- 1 mm Hg; L-SNS: 118 +/- 26 mm Hg; R-SNS: 116 +/- 33 mm Hg; p < 0.001) while systemic vascular resistance remained unchanged. There was a sigmoid dose-response curve with rapid on- and offset of the effect during SNS initiation/cessation. Positive inotropic effects persisted for 12 h of continued SNS (n = 4). Besides positive dromotropic effects, L-SNS/R-SNS yielded a 41% and 77% sinus rate increase, respectively. CONCLUSIONS: The neural adrenergic tone to the heart can be selectively increased by catheter stimulation of cardiac efferent sympathetic nerves.
Explore the source record for details and available documents.
BACKGROUND: Direct stenting may reduce trauma to the vessel wall, thereby having a positive impact on acute and long-term results. This study evaluated acute vessel trauma and acute and follow-up angiographic and intravascular ultrasound (IVUS) results after direct stenting in comparison to conventional stenting. METHODS: Two hundred forty-nine patients were randomly assigned to direct stenting (n = 124) or stenting after predilatation (n = 125) and were followed up by angiography at 6 +/- 2 months. Intracoronary serum endothelin (ET-1) levels were determined distal to the lesion before and after coronary intervention to define vessel trauma, and IVUS was performed before and after intervention and at follow-up to determine induced changes in vessel morphology and intimal hyperplasia in a subgroup of 40 patients. RESULTS: Feasibility of direct stenting was 91%, with 9% requiring crossover to predilatation. There were no differences between the 2 groups in immediate clinical, angiographic, and intravascular ultrasound results. Intracoronary ET-1 levels increased significantly after intervention, without differences between the 2 groups (increase in ET-1 level, 0.79 +/- 1.06 vs 0.96 +/- 1.22 fmol/L, P =.206). At 6-month follow-up, angiographic late loss (0.76 +/- 0.86 vs 0.69 +/- 1.09 mm, P =.788) and restenosis rate (21% vs 20%, P = 1.000) were similar for direct stenting versus conventional stenting, respectively. IVUS demonstrated comparable intimal hyperplasia areas for direct versus conventional stenting (2.0 +/- 1.5 mm(2) vs 2.2 +/- 1.6 mm(2), respectively, P =.243). CONCLUSIONS: Direct stenting is highly feasible and results in similar vessel trauma and change in vessel morphology and acute lumen dimensions compared with stenting after predilatation. Similar acute angiographic and IVUS results persist at 6-month follow-up.
Implantable cardioverter defibrillators and pacemakers detect an increasing number of silent episodes of AF. In a porcine model, the study evaluated the contractility of the left atrial appendage (LAA) during AF paroxysms as they may occur in patients. Peak outflow velocity of the LA and mean outflow velocity of the LAA (LAA-V(outmean)) (n = 17) were measured before, during, and after induction of self-terminating AF. LAA-V(outmean) was also measured during incremental pacing from different atrial sites using epicardial Doppler probes (n = 6) and during continuous recordings (n = 5) of 40 minutes of pacing maintained AF. Compared to baseline sinus rhythm, LAA-V(outmean) increased during short AF episodes (41 +/- 3 vs 35 +/- 2 cm/s, P < 0.05). After termination of the AF episodes, LAA-V(outmean) further increased (69 +/- 15 cm/s, P < 0.001 vs baseline). This "postfibrillatory enhancement" maintained after repeated induction of short AF paroxysms. During prolonged AF episodes lasting 40 minutes, an initial hypercontractility (44 +/- 2 vs 38 +/- cm/s, P < 0.01) was followed by a hypocontractility after 20 minutes (29 +/- 12 P < 0.05 vs SR) and a postfibrillatory enhancement after cessation of AF (56 +/- 12 vs 27 +/- 9 cm/s at 40 minutes AF, P < 0.001). L-type Ca channel blockade abolished the initial hypercontractility during AF and the postfibrillatory enhancement. Repetitive AF paroxysms up to 2 minutes did not decrease left atrial contractility. During maintained AF up to 40 minutes an initial hypercontractility and a consecutive hypocontractility, which is overcompensated by a postfibrillatory enhancement of atrial inotropy after cessation of AF, are present. The observed phenomenon seems to be related to an increased Ca(2+) influx through the L-type Ca(2+) channel.
Ectopic beats originating from sleeves of atrial tissue within the pulmonary veins (PVs) can induce and sustain paroxysmal atrial fibrillation (AF). Left atrial stretch and dilatation favors the development of atrial ectopy and AF. Similarly, PV dilatation, if present, might trigger PV ectopy in patients with AF. This study was designed to evaluate whether PV dilatation is present in patients with nonfocal AF and whether the PV diameter correlates to the left atrial diameter (LAD). The diameters of the right superior (RSPV) and left superior PV (LSPV) were measured at the ostium and at a depth of 1 cm in 170 patients (AF, n = 75; sinus rhythm [SR], n = 95) using transesophageal echocardiography. The LAD was determined by transthoracic echocardiography. The diameters of the PVs were significantly larger in patients with AF than in patients with SR (LSPV(ostium): AF 13.6 +/- 3.5 mm vs SR 10.6 +/- 2.7 mm, P < 0.001; LSVP(1cm): AF 12.5 +/- 2.9 mm vs SR 10.2 +/- 2.5 mm, P < 0.001; RSPV(ostium): AF 13.9 +/- 3.5 mm vs SR 11.7 +/- 2.9 mm, P < 0.001; RSVP(1cm): AF 12.8 +/- 2.8 mm vs SR 10.6 +/- 2.6 mm, P < 0.05). Similarly, LAD was larger in patients with AF (44.7 +/- 7.7 mm) as compared to patients with SR (38.8 +/- 6.8 mm, P < 0.001). Neither for the SR nor the AF group did the PV size correlate to the LAD. AF is associated with a significant enlargement of the RSPV, LSPV, and LAD. There is no correlation between LAD and PV diameters. This raises the question whether PV dilatation in patients with AF is a cause or a consequence of AF and whether it may contribute to the development and perpetuation of AF.
BACKGROUND: There is controversy about the role of decreased resting blood flow as the pathophysiologic correlate of hibernating myocardium. The aim of this study was an absolute quantification of volumetric myocardial blood flow (MBFvol) in dysfunctional myocardium with different viability conditions as defined by fluorine 18 deoxyglucose (FDG) positron emission tomography (PET) while taking into consideration the functional recovery after revascularization. The impact of MBFvol in the diagnosis of functional recovery was also investigated. METHODS AND RESULTS: Forty-two patients with severe coronary artery disease and dysfunctional myocardium underwent resting oxygen 15 water PET, as well as FDG PET and technetium 99m tetrofosmin single photon emission computed tomography, all attenuation-corrected. Relative FDG and Tc-99m tetrofosmin uptake (normalized to the segment with 100% Tc-99m tetrofosmin uptake), as well as MBFvol (myocardial blood flow multiplied by the water-perfusable tissue fraction to account for the flow to the entire segment volume), were determined in 18 myocardial segments per patient. Viability in dysfunctional segments (estimated by ventriculography) with reduced Tc-99m tetrofosmin uptake of 70% or lower was classified as viable (FDG >70%, mismatch) or nonviable (FDG < or =70%, match). Fifteen patients underwent revascularization and were followed up. Mismatch segments with improved function were classified as hibernating myocardium. Mean MBFvol in viable myocardium was slightly reduced (0.60 +/- 0.02 mL x min(-1) x mL(-1)) compared with that in normokinetic myocardium (0.64 +/- 0.01 mL x min(-1) x mL(-1)) (P = .036) and was significantly higher than in nonviable myocardium (0.36 +/- 0.01 mL x min(-1) x mL(-1)) (P < .001). Receiver operating characteristic analysis confirmed an FDG uptake greater than 70% as the optimal threshold to predict functional recovery (diagnostic accuracy [ACC], 76%). MBFvol in hibernating myocardium (0.62 +/- 0.04 mL x min(-1) x mL(-1)) was not significantly reduced compared with that in normokinetic myocardium (0.66 +/- 0.02 mL x min(-1) x mL(-1)) and was significantly higher than in persistently dysfunctional myocardium (0.51 +/- 0.04 mL x min(-1) x mL(-1)) (P < .05). The ACC of MBFvol greater than 0.40 mL x min(-1) x mL(-1) as the threshold to predict functional recovery was 61% but did not improve the accuracy of FDG PET by itself. CONCLUSIONS: In patients with severe coronary artery disease and dysfunctional myocardium, MBFvol as determined with O-15 water differs significantly between viable and nonviable myocardium as determined by FDG PET and is not significantly reduced in hibernating compared with normokinetic myocardium. Therefore chronically reduced resting blood flow appears unlikely to be the pathophysiologic correlate of the functional state of hibernation. However, MBFvol does not improve the ACC of FDG PET by itself.