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Biomedical subjects

D Katritsis

Publications and source records attributed to D Katritsis.

At least 55 records · Page 3Linked to original sources
PubMed1992

Effects of flecainide on atrial electrophysiology in the Wolff-Parkinson-White syndrome.

The effects of intravenous flecainide and propafenone (2 mg/kg) administered in random order were compared in 16 patients with Wolff-Parkinson-White syndrome. Both agents prolonged significantly the anterograde refractory period of the pathway and caused complete anterograde block in the pathway in 5 patients. Atrial fibrillation was not inducible in 7 patients following both agents. Both drugs prolonged the minimum pre-excited RR interval, but this effect was significantly greater after flecainide than after propafenone. At a pacing cycle length of 500 msec, the atrial effective refractory period was unchanged after flecainide, but the atrial monophasic action potential duration, and the atrial monophasic action potential duration of the earliest inducible atrial beat were significantly increased. These results suggest that rate-dependent prolongation of atrial repolarization does not occur following clinical intravenous doses of flecainide. The prolongation of the repolarization of ectopic beats may prevent induction of atrial arrhythmias and may also have an important role in the termination of atrial fibrillation.

Atrial Fibrillation↗
PubMed1992

Is angiographic ventriculography necessary for the assessment of ischemic patients?

A total of 53 patients with a provisional diagnosis of ischemic heart disease and without any clinical evidence of valvular, congenital, or primary muscle heart disease were studied by echocardiography and biplane left ventricular cineangiography. For angiographic ejection fraction analysis, a program developed in our department for use on an Apple Macintosh computer interfaced to a digitizing tablet was employed. Echocardiographic outlines of systolic and diastolic images were traced with a digitizing system on the screen and ejection fractions were calculated by a program incorporated in the echo machine. Good echo windows allowing ejection fraction calculations were present in 35 patients. There was a good correlation between angiographic and echocardiographic ejection fraction (r = 0.7, SEE = 0.09), and wall motion assessment revealed no significant discrepancies between the two image modalities. The remaining 18 patients had poor echo windows, preventing accurate echocardiographic determination of the ejection fraction. However, limited assessment of left ventricular size and wall motion was possible in all patients and allowed the identification of those who had impaired left ventricular function as judged by angiography (angiographic ejection fraction < 35%). We conclude that even in patients with poor echo windows echocardiographic assessment of left ventricular function provides clinical information similar to angiography which should not be considered mandatory for the investigation of ordinary ischemic patients.

Cardiac Catheterization↗
PubMed1992

How to prescribe and manage antiarrhythmic drug therapy.

The pharmacological approach is the corner-stone of therapy for arrhythmia because it is non-invasive, convenient and widely available. However, the indications for antiarrhythmic therapy in general, as well as the indications for drug therapy as opposed to non-pharmacological therapeutic methods, are far from clearly defined. Among the existing antiarrhythmic drugs, clear reduction of mortality due to arrhythmia has been shown definitively only with beta-blocking agents and possibly with amiodarone.

Anti-Arrhythmia Agents↗
PubMed1992

Intravascular ultrasound imaging of the coronary arteries: an in vitro evaluation of measurement of area of the lumen and atheroma characterisation.

OBJECTIVE: To assess the accuracy of measurement of area of the lumen, and sensitivity, and specificity of detection of atheroma in coronary arteries in vitro with a commercially available 20 MHz intravascular ultrasound system. SETTING: A teaching hospital department of cardiology with the support of the department of cardiovascular pathology. PROCEDURE: 10 segments of coronary artery were removed from cadaver hearts. Intravascular ultrasound imaging was performed at fixed levels and the vessels were then sectioned and photographed before histological preparation. An independent blinded observer measured luminal area and assessed the presence of atheroma on the intravascular ultrasound images of 76 vessel sections (304 quadrants). The sensitivity and specificity of detection of atheroma was assessed in comparison with the histologically prepared sections. Luminal areas from intravascular ultrasound, photographs of cross sections of the vessels and histological sections were compared with the technique of limits of agreement. RESULTS: Overall 36% of the 304 quadrants studied histologically had identifiable atheroma. Intravascular ultrasound sensitivity for atheroma was 0.593 and the specificity was 0.839. The positive predictive value was 0.674, and the relative risk 3.139. Values for area of the vessel lumen were on average 9.4 mm2 (confidence interval (CI) 8.6-10.2 mm2) larger than those measured from photographs and 10.7 (CI 9.8-11.6 mm2) larger than those measured from the histological sections. CONCLUSIONS: The intravascular ultrasound system assessed in this study significantly overestimated coronary vessel luminal area and had low sensitivity and specificity for detection of atheroma. Improvements in image resolution are required before this system can provide useful information on coronary artery size and morphology.

Coronary Artery Disease↗
PubMed1992

Three decades of antiarrhythmic therapy.

Over the last several decades there has been an impressive expansion in the study and management of cardiac arrhythmias. New developments in diagnostic and interventional clinical electrophysiology as well as research at the cellular tissue and whole heart levels have improved our understanding of the mechanisms of arrhythmias and have allowed the development of new and effective treatment modalities. During the 1960s (Early Decade-Enabling) the first lifesaving measures such as cardiac resuscitation, external defibrillation, and temporary pacing were introduced in the new coronary care units. Cardiac catheterization and reproducible techniques for recording of intracardiac potentials were developed. The decade of 1970 to 1980 (Middle Decade-Diagnosis) was characterized by the development of programmed stimulation for initiation and termination of arrhythmias. This represented a real revolution in clinical cardiology that led to the understanding of the nature of several tachyarrhythmias and related them to experimental mechanisms of arrhythmogenesis. In the same decade, two other diagnostic tools emerged for assessing cardiac arrhythmias and monitoring the efficacy of antiarrhythmic drug therapy: ambulatory ECG monitoring and exercise testing. In addition, the impact of antiarrhythmic drugs on ionic currents was studied and drug classifications based on these properties appeared. The decade 1980-1990 (Recent Decade-Therapy), witnessed the development of interventional electrophysiology techniques such as transcatheter ablation, and the use of cardiac surgery for the ablation of arrhythmogenic substrates. Another major advance was the design of implantable devices capable of recognizing tachyarrhythmias and treating them by programmed stimulation or defibrillation shocks. In parallel, the efficacy and safety of antiarrhythmic drugs has been reassessed and new compounds are being developed.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Arrhythmia Agents↗
PubMed1992

Adaptive-rate pacemakers. Comparison of sensors and clinical experience.

Many types of artificial sensors for adaptive-rate pacing have appeared but as yet there is no single sensor that properly reflects metabolic demand under all circumstances. Several other types of sensors are currently evaluated. Combinations of different sensors in a single unit are very promising. At present, however, the only completely satisfactory sensor is the normal sinus node.

Arousal↗
PubMed1991

Primary restrictive cardiomyopathy: clinical and pathologic characteristics.

Twenty-four patients with restrictive cardiomyopathy were identified at St. Thomas' Hospital during a 17-year period. All had endomyocardial biopsy, but in two patients the biopsy specimens were small and nondiagnostic. Seven patients had amyloidosis and five had other specific heart muscle diseases. The remaining 10 patients with primary restrictive cardiomyopathy had myocyte hypertrophy or interstitial fibrosis, or both. Patients with primary restrictive cardiomyopathy presented earlier but survived longer after presentation than did those with amyloidosis. In each group, survival after cardiac catheterization was related to cardiac index but not to filling pressures. Primary restrictive cardiomyopathy was associated with complete heart block in four patients, two of whom had skeletal myopathy. One had a family history of dominantly inherited skeletal myopathy. Primary restrictive cardiomyopathy was present in a mother and daughter. Two other patients had a family history of heart failure, sudden death or complete heart block, alone or in combination, at a young age. Restrictive hemodynamics and complete heart block were present in patients even in the absence of significant fibrosis. The data suggest that primary restrictive cardiomyopathy may be a distinct myopathy with dominant inheritance and incomplete penetrance that is expressed morphologically as myocyte hypertrophy and interstitial fibrosis. Skeletal myopathy may be associated with the cardiomyopathy.

Adolescent↗
PubMed1991

Limitations of coronary angiography: an underestimated problem?

Angiographic imaging suffers from many limitations which may distort the diagnostic information obtained from coronary arteriograms. Radiographic features limiting precise coronary stenosis measurement are caused by the x-ray source, the image intensifier, and the chemical properties of the cinefilm. Biologic variations are introduced by fluctuations in angiographic contrast concentration and flow- or contrast-dependent coronary dilation. Random errors are also introduced by the selection of the radiographic projection and frame to be analyzed and the digitization of cineangiograms. These limitations and their significance in distorting quantitative information obtained from coronary angiograms are discussed in this review.

Angiography↗
PubMed1991

Single-lead VDD pacing: excellence or expedience?

The interest in VDD pacemakers has been renewed by the introduction of single-pass leads, and continuing modifications and technical developments promise significant improvement. However, convincing long-term data confirming the reliability and the use of newer leads are not yet available. Compared with VVIR pacemakers VDD pacing has theoretical advantages over the VVIR mode, offering better hemodynamic and endocrine responses. However, its range of indications is narrow and rate adaptation is essential when sinus node chronotropic inadequacy is present or likely to occur. In addition, on certain occasions a VDD pacemaker may not maintain persistent atrial-synchronous pacing, thus necessitating the use of a DDD unit.

Electrodes, Implanted↗
PubMed1991

201Tl scintigraphy in the assessment of patients with multi-vessel coronary disease undergoing angioplasty who have previously had a coronary bypass graft operation.

Percutaneous transluminal coronary angioplasty (PTCA) has an important therapeutic role in the treatment of coronary artery disease. The purpose of this study was to investigate the role of 201Tl scintigraphy in symptomatic patients with multi-vessel coronary artery disease undergoing angioplasty who had previously undergone coronary graft operations. 201Tl imaging was carried out in 12 patients prior to PTCA, 6 weeks and 6 months to 1 year post-PTCA. Prior to PTCA, 201Tl imaging correctly identified the site of the dominant lesion in all patients in correlation with the catheter results. Six weeks post-PTCA, seven cases who had angiographically successful angioplasty showed persistent defects on 201Tl imaging. In five of these cases, follow-up catheter showed that re-stenosis had occurred. Six months to 1 year post-PTCA, 201Tl imaging was found to have good correlation (11 out of 12 patients) with the catheter results. The results suggest that 201Tl imaging is useful in the management of patients with multi-vessel disease undergoing angioplasty.

Aged↗
PubMed1991

Influence of propranolol on the ventricular depolarization gradient.

Sensing of the ventricular depolarization gradient (VDG) has recently been used as the basis of a closed-loop rate responsive pacemaker. Factors influencing this aspect of the evoked response have not been fully evaluated although previous reports have suggested that sympathetic stimulation and circulating catecholamines are primarily responsible for the observed changes during stress and exercise. In five patients (Table I), four males and one female (mean age 60.4 +/- 10.1 years) implanted with the Prism pacemaker, the pacing response to exercise and tilting was assessed before and after the infusion of propranolol. There was an increase in the pacing rate in all patients during the infusion of the drug (mean 27 +/- 12.9 beats/min) suggestive of a direct drug effect on the VDG. The rate control parameter (RCP) of the pacemaker, the numerical equivalent of the VDG, was significantly different after the administration of propranolol (P less than 0.01). However, exercise performance and pacing rate behavior were not different after beta blockade. The pacing rate increase observed when tilting patients to the supine position was not altered by propranolol. Out date suggest that factors other than adrenergic stimulation may be of importance in affecting the ventricular evoked response and accordingly the rate adaptation of the Prism pacemaker.

Adrenergic beta-Antagonists↗
PubMed1991

Amiodarone in long term prophylaxis.

Amiodarone is predominantly a potassium channel inhibitor which prolongs repolarisation and refractoriness, and thus qualifies as a Group III antiarrhythmic agent. In addition, it possesses a variety of electrophysiological actions such as sodium channel blockade, calcium channel blockade and noncompetitive inhibition of adrenergic receptors. In the studies reported below, the incidence of successful treatment of refractory ventricular arrhythmias with amiodarone appears to range between 50 to 60% in the first year. However, there are very few prospective randomised studies which assess its efficacy in controlling ventricular tachycardia in comparison with placebo or another antiarrhythmic compound. As there have been no controlled studies to examine the impact of amiodarone in preventing ventricular tachycardia in survivors of cardiac arrest compared with either no treatment or with alternative therapies, the actual efficacy of amiodarone in patients who have survived a cardiac arrest is virtually unknown. Although there are indications that amiodarone reduces the incidence of sudden death in patients with malignant arrhythmias, definitive evidence based on controlled trials is not available.

Administration, Oral↗
PubMed1990

Are antiarrhythmic drugs safe?

The indications for antiarrhythmic therapy are far from clearly defined and the choice of treatment is usually based on empiric strategies. Antiarrhythmic agents can have serious side effects. Systemic adverse effects are usually use-related and reversible with withdrawal of the drug. Impairment of left ventricular function is considerable in patients with heart failure. The most important, life-threatening side effect of antiarrhythmic drugs is their proarrhythmic tendency which gives rise to certain concern about their clinical use. Aggravation of arrhythmia often occurs without symptoms, goes unrecognized by the patient, and is exposed only by monitoring, exercise testing, or invasive electrophysiological testing. Patient monitoring with electrolyte measurement, Holter recording, and electrophysiological reassessment can reveal or reduce the proarrhythmic risk but cannot eliminate the problem completely. The institution of antiarrhythmic therapy should be considered in highly symptomatic or life-threatening arrhythmias after careful consideration of the benefit-risk ratio.

Anti-Arrhythmia Agents↗
PubMed1990

Cardiac phase-related variability of border detection or densitometric quantitation of postangioplasty lumens.

We applied an automated computer program capable of simultaneous geometric (through border detection) and densitometric quantitation of digital angiograms for evaluation of the results of percutaneous transluminal coronary angioplasty (PTCA) in different phases of the same cardiac cycle. Digital subtraction coronary angiograms (DSA) of 28 patients who had undergone PTCA to a total of 30 lesions, were analyzed in diastole, in systole, and in the middle of the cardiac cycle to test the variability in coronary quantitation resulting from random frame selection relative to cardiac phase. Before PTCA there was a low degree of variation between measurements obtained from the same lesion in different phases of the cardiac cycle, in both geometric (coefficient of variation between cardiac phases = 4.2%) and densitometric (coefficient of variation between cardiac phases = 5.1%) quantitation. After PTCA, however, there was a wider variation of values in different cardiac phases, which predominated in the densitometric measurements (coefficient of variation between cardiac phases = 33.6%, compared to 20.6% for geometric measurements). There was less agreement between different post-PTCA phases in densitometry, and discrepancies as large as 47% could occur in densitometric evaluation of the stenotic areas when different phases of the cycle were used. We concluded that border detection or densitometric quantitation of the postangioplasty lumens is subject to greater variation resulting from random frame selection relative to cardiac phase, as compared to preangioplasty assessment. This variation predominates in densitometric quantitation, which seems to be dependent not only on the radiographic projection but also on the cardiac phase. The usefulness of densitometric techniques for the evaluation of PTCA results appears to be questionable.

Angiography, Digital Subtraction↗