Autonomic Effects of Dipyridamole Stress Testing on Frequency Distribution of RR and QT Interval Variability

Transient myocardial ischemia and associated changes in the autonomic nervous system may influence heart rate and ventricular repolarization to variable degrees. This study evaluated the effect of dipyridamole (DIP) induced ischemia on the autonomic balance by spectral analysis of RR and QT intervals variability. Patients with coronary artery disease undergoing DIP stress echocardiography were studied. From high resolution ECG recordings, RR and QT interval measurements were performed by a dynamic template-matching algorithm. A time-variant analysis was used to estimate power in the LF (0.05–0,15 Hz) and in the HF (0.15–0.4 Hz) band of RR and QT interval spectra. Patients were grouped in ischemic and nonischemic subgroups based on the echocardiographic detection of wall-motion abnormalities. In patients without ischemia (n = 28), DIP caused a decrease in LF power and an increase in HF power of the RR and QT interval variability, indicating concordant changes of both intervals. In contrast, patients with inducible ischemia (n = 11) showed a decrease in HF power of the RR interval spectra and an increase of HF power of QT interval spectra. Furthermore, LF power was increased for RR but decreased for QT interval spectra. Our study suggests that DIP induced ischemia causes a loss of autonomic coupling between heart rate and ventricular repolarization for sympathetic and parasympathetic activities. This lability in ventricular repolarization may constitute an arrhythmogenic substrate during acute ischemia in patients with coronary artery disease.     

The Tall R Wave in Lead V1 in Posterior Myocardial Infarction: A Reciprocal Sign or a His-Purkinje Conduction Disturbance?

The significance of the tall R wave in lead V1 with an R/S ratio greater than or equal to 1 in posterior myocardial infarction (PMI) was investigated in 28 patients during programmed electrical stimulation. The patients had been admitted with acute PMI documented by electrocardiogram and proven by enzymatic increase. Electrophysiological study was performed 3 weeks after acute PMI. In 17 of the 28 patients (group 1), the tall R wave in V1 disappeared during stimulation: In 13 of them a premature atrial extrastimulus was responsible for an abrupt normalization of QRS complex in V1 related to an increase in AH or HV interval. In the 4 remaining patients the disappearance of the tall R wave in V1 was related to a sinus pause. In 14 patients of group 1, a different prematurity in atrial stimulation induced a right or left bundle branch block (BBB). In 11 of the 28 patients (group 2) the tall R wave in V1 was unchanged but a premature atrial extrastimulus induced a right BBB in 5 patients and a left BBB in 6. In conclusion, the normalization of QRS complex in lead V1 during atrial stimulation or alterations in cycle length suggests that the tall R wave in V1 in PMI is not a simple reciprocal sign of leads V8 V9. Its association with different varieties of BBB and changes in AH or HV intervals could suggest a relationship with a His-Purkinje conduction disturbance in some patients.     

P Wave and Far-Field R Wave Detection in Pacemaker Patient Atrial Electrograms

This study was undertaken to develop and test a morphology-based adaptive algorithm for real-time detection of P waves and far-field R waves (FFRWs) in pacemaker patient atrial electrograms. Cardiac event discrimination in right atrial electrograms has been a problem resulting in improper atrial sensing in implantable devices; potentially requiring clinical evaluation and device reprogramming. A morphologybased adaptive algorithm was first evaluated with electrograms recorded from 25 dual chamber pacemaker implant patients. A digital signal processing (DSP) system was designed to implement the algorithm and test real-time detection. In the second phase, the DSP implementation was evaluated in 13 patients, Atrial and ventricular electrograms were processed in real-time following algorithm training performed in the first few seconds for each patient. Electrograms were later manually annotated for comparative analysis. The sensitivity for FFRW detection in the atrial electrogram during off-line analysis was 92.5% (± 10.9)and the positive predictive value was 99.1% (± 1.8). Real-time P wave detection using a DSP system had a sensitivity of 98,9% (± 1.3) and a positive predictivity of 97.3% (± 3.5). FFRW detection had a sensitivity of 91.0% (± 12.4) and a positive predictivity of 97.1% (± 4.2) in atrial electrograms. DSP algorithm tested can accurately detect both P waves and FFRWs in right atrium real-time. Advanced signal processing techniques can be applied to arrhythmia detection and may eventually improve detection, reduce clinician interventions, and improve unipolar and bipolar lead sensing.     

Basement membrane components and galactosylhydroxylysyl glucosyltransferase in suction blisters of human skin

Basement membrane components and collagen biosynthesis were studied in suction blisters in human skin. The basement membrane components were characterized by immunofluorescence using specific antibodies to type IV collagen, laminin and fibronectin, and collagen biosynthesis was studied by assaying galactosylhydroxylysyl glucosylatransferase. In suction blisters, the separation of epidermis and dermis occurred above the lamina lucida, indicating that the basement membrane, composed of lamina lucida and lamina densa, forms a mechanically strong entity. During the regeneration phase of blisters, type Iv collagen and laminin were not observed in the old epidermal blister roof. This indicates that keratinocytes when separated from the underlying basement membrane or connective tissue do not synthesize laminin or type IV collagen. Galactosylhydroxylysyl glucosyltransferase activity could be demonstrated in blister fluid and was about the same as in serum when expressed on the basis of protein in fresh blisters. It increased by 2-3 fold during the repair of blisters, indicating that there was local production of this enzyme. Further studies revealed that pure epidermis contained galactosylyhdroxylysyl glucosyltransferase and hydroxyprolineand this suggests that epidermis may synthesize some collagen type which, according to these studies, is not type IV (basement memebrane) collagen.     

Recent Advances in Cardiopulmonary Resuscitation

Recent Advances in CPR. Mechanical and pharmacologic measures intended to increase blood now to vital organs are the mainstay of therapy for patients in cardiac arrest. Several new cardiopilmonary resuscitation (CPR) techniques as well as novel devices and pharmacologic agents have been developed and tested since the first report of manual closed chested CPR over three decades ago. These recent mechanical and pharmacologic advances in the treatment of cardiac arrest are described. Some of these new techniques, devices, and drug therapies are presently undergoing clinical evaluation in patients in cardiac arrest. While many of these new methods and techniques have shown promise in small clinical trials in humans, none have yet lo be found to be conclusively superior to manual closed chested CPR and treatment with standard pharmacologic agents.     

Structural Asymmetries in the Human Forebrain and the Forebrain of Non-human Primates and Rats

ZILLES, K., A. DABRINGHAUS, S. GEYER, K. AMUNTS, M. QÜ, A. SCHLEICHER, E. GILISSEN, G. SCHLAUG, H. STEINMETZ. Structural asymmetries in the human forebrain and the forebrain of non-human primates and rats. NEUROSCI BIOBEHAV REV 20(4)593-605, 1996.—Possible asymmetries of the following structures were studied: volumes of total human hemispheres, cortex and white matter volumes in post-mortem- (unknown handedness) and living brains (male right-handers); volumes of the rat total primary visual cortex, its mon- and binocular subfields, its layer IV and the density of myelinated fibres in layer IV; transmitter receptor densities (NMDA, AMPA, kainate and GABA_A receptors) in sensorimotor regions of the rat cortex; volume of the motor cortex and the 3D-extent of the central sulcus in the post-mortem- (unknown handedness) and living human brain (male right-handers); petalia of the hemispheres in human (male right- and left-handers) and chimpanzee brains. Histological, MRI and receptor autoradiographic techniques were used. With the notable exceptions of the transmitter receptors and the total primary visual cortex in rats and the hemispheres in chimpanzees, which do not show any significant directional asymmetry, all other parameters studied are asymmetrically distributed between the right- and left hemispheres. The regional distribution pattern and the degree of asymmetry of frontal and occipital petalia in living human brains differ between right- and left-handers. Copyright © 1996 Elsevier Science Ltd.     

Central haemodynamic effects of metoprolol early in acute myocardial infarction. A placebo controlled randomized study of patients with low heart rate

The central haemodynamic effects of metoprolol in patients withacute myocardiol infarction and with heart rate 65 beats min^–1have been investigated in a randomized double-blind trial. Theaim was to study the tolerance in this selected patient groupand to assess possible differences in haemodynamic responseamongst patients with initially higher heart rates. Exclusioncriteria were: treatment with beta blockers; heart rate 65beats min^–1 systolic blood pressure 110 mmHg; and physicalsigns of serious heart failure. Following pulmonary artery catheterization,22 patients were randomized to metoprolol 15 mg i. v. + 50 mgq.i.d. orally ( N = 12) or placebo (N = 10). Central pressuresand cardiac output were recorded before and during the 24 hoursafter drug administration. There was a significant fall in heartrate, cardiac index, rate pressure product and stroke work indexof 10–20% in the metoprolol, compared with the placebogroup. The differences were most pronounced immediately afterthe metoprolol injection. The pulmonary artery capillary wedgepressure was not significantly changed. The overall haemodynamicresponse to metoprolol was similar to that reported in patientswith acute myocardial infarction and heart rate above 65 beatsmin^–1 Tolerance was good.     

Declining hospital mortality in acute myocardial infarction

Beta-blockers, nitrates, aspirin and thrombolytic drugs haveeach separately been shown to reduce mortality in acute myocardialinfarction, but the effect of these treatments combined duringroutine coronary care has not been assessed. The coronary careunit at Östra Hospital services a stable community of 250000 inhabitants. Since 1984 all patients have been entered intoa computerized database. In addition, information on age, sex,discharge diagnosis and hospital outcome is also available forpatients admitted between 1979 and 1983. In 1984, routine treatmentwith intravenous beta-blockers was introduced, to be followedin 1986 by intravenous nitroglycerin and in 1988 by aspirinin all patients without contraindications. Since 1988, intravenousthrombolytic treatment has been also given routinely to allpatients with ST-elevation and chest pain <6 h. Despite asimilar number of patients and an increasing median age, thein-hospital mortality has declined from 18·5% in 1979to 11·8% in 1990 (P<0·01). It is concludedthat mortality from acute myocardial infarction has declinedby almost 40% since 1979. This reduction cannot be explainedby a single major therapeutic intervention but may be attributedto the combined use of multi-lead monitoring, early use of beta-blockers,nitroglycerin, aspirin and thrombolytic agents.     

Repeated Radiofrequency Ablation of Atrial Tachycardia in Restrictive Cardiomyopathy Secondary to Myofibrillar Myopathy

Myofibrillar myopathy is characterized by nonhyaline and hyaline lesions due to mutations in nuclear genes encoding for extra‐myofibrillar or myofibrillar proteins. Cardiac involvement in myofibrillar myopathy may be phenotypically expressed as dilated, hypertrophic, or restrictive cardiomyopathy. Radiofrequency ablation of atrial fibrillation and flutter has so far not been reported in myofibrillar myopathy. We report the case of a young female with myofibrillar myopathy and deteriorating heart failure due to restrictive cardiomyopathy and recurrent atrial fibrillation and atrial tachycardias intolerant to pharmacotherapy. Cardiac arrhythmias were successfully treated with repeat radiofrequency ablations and resulted in regression of heart failure, thus postponing the necessity for cardiac transplantation.     

Overtreatment Effects Associated with a Radiofrequency Tissue Tightening Device: Rare, Preventable, and Correctable with Subcision and Autologous Fat Transfer

Device complication rates were analyzed in the Regulatory and Quality Assurance departments of Thermage, Inc., Hayward, CA, USA, in consultation with Dr. Whitney D. Tope. Corrective treatment in the case study was performed at the Dermatology Surgery and Laser Center, White Plains, NY.