Berndt Lüderitz

Cerebral diffusion-weighted magnetic resonance imaging: a tool to monitor the thrombogenicity of left atrial catheter ablation.

Introduction: Cerebral embolism and stroke are feared complications of left atrial catheter ablation such as pulmonary vein (PV) ablation. In order to assess the thrombogenicity of left atrial catheter ablation, knowledge of both clinically evident as well as silent cerebral embolism is important. The aim of the current study was to examine the use of diffusion‐weighted magnetic resonance imaging (DW‐MRI) for detection of cerebral embolism, apparent as well as silent, caused by PV catheter ablation.

Real-time contrast echo assessment of myocardial perfusion at low emission power: First experimental and clinical results using power pulse inversion imaging

Power pulse inversion (PPI) has been developed for echocontrast specific imaging in order to reduce destruction of microbubbles. The purpose of this study was to evaluate PPI for real‐time contrast echocardiography. Therefore, in vitro studies in a physiological flow‐phantom and clinical examinations in patients with coronary artery disease were performed. The in vitro rersults of this study indicate that PPI allows real‐time imaging at low emission power and is almost nondestructive to contrast microbubbles of Definity. At this low emission power a strong linear relationship between the dosage of the contrast agent and the resulting PPI signal intensity was found (R = 0.998, p < 0.001). In the clinical examinations real‐time imaging using low mechanical index PPI resulted in strong myocardial signals and a complete filling of the cavities indicating absence of bubble destruction. Most striking was the ability of PPI to display myocardial thickening and wall motion simultaneously with the assessment of myocardial contrast replenishment following ultrasound induced bubble destruction by high power frames. We conclude that PPI allows nondestructive contrast imaging both in experimental and clinical settings. Therefore, real‐time imaging of myocardial perfusion and real‐time assessment of contrast replenishment following ultrasound induced destruction of microbubbles is feasible. Moreover, PPI allows simultaneous assessment of perfusion and myocardial function.

Improvement in Endocardial Border Delineation Using Tissue Harmonic Imaging

Background and Methods: For years, tissue has been assumed to be a linear medium in diagnostic ultrasound applications; thus, no backscattered signals in the second harmonic band are expected in harmonic imaging without the injection of a contrast agent. However, it has been shown that a useful tissue image is formed even without a contrast agent. The aim of this study was to evaluate whether this tissue harmonic image provided improved visualization of endocardial borders. Fifty‐six adult patients with various heart diseases were investigated using conventional two‐dimensional echocardiography and tissue harmonic imaging. In 30 of these patients, the left ventricular endocardial borders were well defined in the standard parasternal and apical views using conventional two‐dimensional echocardiography. In the remaining 26 patients, delineation of endocardial borders was not possible in at least two segments. The equipment used was an ATL HDI‐3000 diagnostic system equipped with harmonic imaging. Results: In all 56 patients, the myocardium and valves could be imaged with tissue harmonic imaging. Harmonic recordings were sharper and contained fewer clutter artifacts than conventional recordings. Most striking was the enhancement of left ventricular endocardial borders. In the 26 patients with incomplete delineation of left ventricular endocardial borders, wall motion could be evaluated in 290 of 312 (93%) segments with tissue harmonic imaging compared with only 168 of 312 (54%) segments with conventional echocardiography (P < 0.001). Conclusions: Tissue harmonic imaging improves image quality and can be used to enhance the definition of left ventricular endocardial borders. These findings can be explained by the nonlinear propagation of ultrasound within the tissue, which results in distortion of the transmitted signal and, thus, harmonic generation.

Harmonic Power Doppler Contrast Echocardiography: Preliminary Clinical Results

Background: In fundamental and second harmonic echocardiography new contrast media opacify the cavities and reduce the difference in the gray level between the cavity and the myocardium thus obscuring the borders of the myocardium. Objectives: The aim of the study was to examine the potential usefulness of second harmonic power Doppler imaging (HPD) in providing adequate delineation of the myocardium from the left ventricular (LV) and right ventricular (RV) cavities during intravenous contrast echocardiography. Using HPD, microbubbles in a cavity or a tissue are imaged as colored pixels superimposed on a conventional B‐scan image. Methods: In a pilot study, three healthy volunteers and two patients with ischemic heart disease were investigated using an ATL‐HDI 3000 echo system. Four chamber views were obtained using fundamental B‐scan, harmonic B‐scan two‐dimensional echocardiography (H2D) and HPD following intravenous injections of 3 g Levovist*. Results: Using intermittent scanning/recording, H2D and HPD provided intensive and homogenous contrast effects in the RV and LV cavities. Good delineation of the myocardium was found in all subjects using HPD, whereas in two of three volunteers and in one of two patients ventricular septal and apical endocardial borders were obscured during H2D. No obvious change in myocardial backscatter was visually found with H2D. However, in all three healthy volunteers and in one of two patients, HPD recordings demonstrated patchy and reticular patterns in the myocardium, which were different from the homogenous signals in the LV cavity. These are consistent with imaging of intramyo‐cardial coronary vessels. Conclusions: HPD with intravenous Levovist is feasible. This technique demonstrated good delineation of ventricular cavities from the myocardium as well as presence of visible contrast in the myocardium. This pilot study justifies further clinical trials to evaluate the clinical benefit of this approach.

Changes of pulmonary vein orifice size and location throughout the cardiac cycle: Dynamic analysis using magnetic resonance cine imaging

Introduction: Anatomically guided left atrial ablation is used increasingly for treatment of atrial fibrillation (AF). Three‐dimensional mapping systems used for pulmonary veins (PV) encircling ablation procedures anticipate a stable size and position of the PV orifice. The aim of the current study was therefore to analyze changes of PV orifice size and location throughout the cardiac cycle using cine magnetic resonance imaging (MRI).

Electrical proarrhythmia: induction of inappropriate atrial therapies due to far-field R wave oversensing in a new dual chamber defibrillator.

R Wave Far‐Field Sensing in Dual Chamber Defibrillators. This case report describes delivery of atrial therapies during a sinus tachycardia in a new dual chamber implantable cardioverter defibrillator inappropriately caused by far‐field oversensing of ventricular beats in the atrial channel. Upon classification of the PR interval pattern, the rate criterion for an atrial tachycardia was fulfilled, and the device initiated high‐frequency burst pacing as the first stage of programmed tiered atrial therapies. Atrial fibrillation subsequently was induced by high‐frequency burst pacing, and eventually a programmed 10‐J shock was delivered for successful termination of atrial fibrillation. The phenomenon of far‐field oversensing of ventricular beats could be repeatedly observed during exercise testing and abolished by decreasing the atrial sensitivity.

Comparison of Indicator‐Dilution Curves Obtained from Dye Dilution and Echo Contrast Using Harmonic Power Doppler Imaging

Background: Harmonic power Doppler imaging (H‐PDI) has been introduced into the field of contrast echocardiography as a contrast‐specific imaging modality. However, there has been considerable skepticism as to whether H‐PDI would be quantifiable, because it depends on the destruction of microbubbles and has more complex signal processing than gray scale imaging. The aim of the present study was to evaluate the relationship between the concentration of microbubbles and the resulting H‐PDI signals even under conditions where bubble destruction is most likely. Furthermore, we evaluated whether micro‐bubbles of Levovist freely pass the microcirculation, which is a prerequisite for the assessment of myocardial blood flow. Methods and Results: A strong positive correlation was found between the H‐PDI signals and the amount of microbubbles up to the onset of acoustic shadowing (r= 0.968, P < 0.001). Time‐intensity curves for H‐PDI of air‐filled microbubbles were compared with time‐concentration curves of indocyanine green (ICG) in both a flow phantom and a working heart setup. The mean transit times (MTTs) through the myocardium of both agents were compared after a bolus injection into the left coronary artery. A close correlation was observed between 1/MTT and flow in both setups (r> 0.98, P < 0.0001). However, at high flow rates, the MTTs of the microbubbles were slightly, albeit not significantly, faster than those of indocyanine green. Conclusions: We conclude that microbubbles fulfill the prerequisites of free flowing tracers through the myocardium. Furthermore, H‐PDI technology allows a reliable assessment of time‐concentration curves of air‐filled microbubbles up to the onset of acoustic shadowing. (ECHOCARDIOGRAPHY, Volume 17, January 2000)

A New Classification Algorithm for Discrimination of Ventricular from Supraventricular Tachycardia in a Dual Chamher Implantable Cardioverter Defibrillator

New Atrioventricular Classification Algorithm. Introduction: The high incidence of inappropriate therapies due to supraventricular tachycardia remains a major unsolved problem of implantable cardioverter defibrillators. We report a new detection formula for discrimination of ventricular tachycardia from supraventricular tachycardia in a patient with a dual chamber implantable cardioverter defibritlator and a new atrioventricular classification algorithm.

Radiofrequency catheter ablation of frequent monomorphic ventricular ectopic activity.

Ablation of Ventricular Ectopic Activity. Introduction: Frequent ventricular ectopic beats can result in severe symptoms and may even be incapacitating in some patients. Although radiofrequency catheter ablation is an effective and safe therapy for drug refractory idiopathic ventricular tachycardia, it has not been widely used in ventricular ectopy. The purpose of this study was: (1) to assess the potential role of catheter ablation in eliminating monomorphic ventricular ectopy in symptomatic patients regarding feasibility and safety and (2) to determine the usefulness of various mapping strategies.

We Have Come a Long Way with Device Therapy: Historical Perspectives on Antiarrhythmic Electrotherapy

Historical Perspectives on Antiarrhythmic Electrotherapy. The history of device therapies is long and fascinating. In the beginning, there is not simply the anatomy and physiology of the heart, but also analysis of the pulse, which indicates the activity of the heart. The analysis of the (peripheral) pulse as a mechanical expression of heart activity goes back several millennia. In China, in 280 BC, Wang Shu He wrote 10 books about the pulse. The Greeks called the pulse “sphygmos”; thus, sphygmology deals with a theory of this natural occurrence. In Roman times, Galen interpreted the various types of pulse according to the widespread presumption of the time that each organ in every disease has its own form of pulse. The growing clinical importance of electrical cardiac stimulation was recognized and renewed as Zoll in 1952 described a successful resuscitation in cardiac standstill by external stimulation. Meanwhile, millions of patients with cardiac arrhythmias worldwide have been treated with pacemakers in the last 40 years. The concept of a fully automatic implantable cardioverter defibrillator system for recognition and treatment of ventricular tachyarrhythmias was first suggested in 1970. The first implantation of the device in a human being was performed in February 1980. Further developments involved atrial and atrioventricular defibrillators, radiofrequency ablation, laser therapy, and advanced antiarrhythmic surgery. Since 1990, there has been a growing interest in using cardiac pacing as additional treatment in severe cardiac failure. Recent reports have suggested that intervention with left ventricular or biventricular pacing may be helpful for a subgroup of patients with congestive heart failure. Despite encouraging (preliminary) acute and short‐term results, pacing strategies for heart failure still are limited and currently regarded as investigational. Advances in the field of therapeutic application of pharmacologic and electrical tools as well as alternative methods will continue as rapidly as before and provide us further significant aid in taking care of patients.