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Biomedical subjects

G Gregoratos

Publications and source records attributed to G Gregoratos.

At least 37 records · Page 2Linked to original sources
PubMed1999

Permanent pacemakers in older persons.

OBJECTIVE: To review (1) the physiologic changes of aging that may lead to the need for a permanent pacemaker; (2) the current standard indications for pacemaker implantation as reported in expert guidelines; (3) newer investigational uses of pacemakers; (4) advances in pacemaker technology; and (5) cost-effectiveness of permanent pacing. DATA SOURCES: Computer-assisted search of the English language literature (MEDLINE database), manual search of articles bibliographies, and review of data provided by a major pacemaker manufacturer. DESIGN: Pertinent articles were reviewed and data extracted. Studies and data involving older persons were emphasized, and these data were extracted and presented. RESULTS: Abnormalities in impulse generation and conduction are common in older people and form the substrate for the need of pacemaker implantation. Pacemaker use is high in older people, with an estimated 70 to 80% of all permanent pacemakers implanted in individuals aged 65 years and older. The hemodynamic changes of aging include a reduction of ventricular compliance and increased contribution of atrial contraction to ventricular filling. Pacemakers that maintain synchrony between atria and ventricles may, therefore, be particularly advantageous in older adults. Recent studies have validated this theoretical reasoning. Chronotropic incompetence is common in older people, and rate responsive ventricular pacing has been shown to improve quality of life compared with fixed rate devices in older patients. Sequential, dual chamber pacemakers reduce the symptoms of pacemaker syndrome and recurrences of atrial fibrillation in certain groups of patients. Potential utility of permanent pacing is being investigated in patients with severe left ventricular dysfunction, markedly prolonged atrioventricular conduction time, hypertrophic and dilated cardiomyopathy, and after cardiac transplantation. Biventricular pacing as therapy for severe heart failure is in the very early phases of investigation. Newer implantable pacemakers provide a host of technological options but are somewhat more expensive and require more frequent follow-up. Controversies still exist regarding the need for pacemakers in certain clinical conditions but are decreasing as new high quality studies are completed. CONCLUSIONS: Permanent pacing is highly cost-effective, safe, and simple to perform. Pacemakers are implanted in patients with sinus node dysfunction, acquired (both native and postsurgical) atrioventricular block, some forms of neurally mediated syndromes, fascicular blocks, and, occasionally, for the prevention of supraventricular or ventricular tachyarrhythmias. Although pacemakers are implanted in individuals of all ages, they are most often utilized in older adults; it is estimated that 70 to 80% of all pacemakers are implanted in patients 65 years of age or older. This is attributable to an increase in abnormalities of impulse generation and conduction with advancing age. Dual chamber pacemakers that maintain synchrony between atria and ventricles are preferable in older patients because of the increased contribution of atrial contraction to ventricular filling in this age group. This theoretical advantage has been confirmed by prospective studies in limited patient subgroups.

Aged↗
PubMed1995

Unique spontaneous coronary artery dissection in an elderly woman.

Spontaneous coronary artery dissection is a rare condition, typically occurring in younger women. A 75-year-old woman with this condition, 17 years older than previously reported, is described, including her unusual presentation with angina rather than infarct. The 112 previously reported cases are summarized and treatment options discussed.

Age of Onset↗
PubMed1990

Pericardial involvement in acute myocardial infarction.

The incidence of both early postinfarction pericarditis and post-myocardial infarction (Dressler's syndrome) appears to be declining. Pericardial pain and pericardial friction rub define early postinfarction pericarditis and usually develop on day 2 or 3 after a transmural myocardial infarction. The clinical course is benign, and the prognosis of the patient is not altered by development of this complication. Pericardial effusions have been found in as many as 28% of patients after acute MI. Asymptomatic pericardial effusions do not require specific therapy nor do they absolutely contraindicate the use of anticoagulation as was previously thought. The preferred form of therapy for early postinfarction pericarditis is aspirin. Avoidance of corticosteroids and NSAIDs must be considered carefully because of the reported complications of these agents. The post-myocardial infarction syndrome develops usually during the second or third week after acute MI but may be seen as early as 24 hours and as late as several months after the MI. Whether this syndrome is the result of autosensitization to myocardial antigens released into the circulation during infarction remains uncertain. Alternative hypotheses for the causation of the syndrome include the release of blood in the pericardial space and simply that the syndrome represents a prolonged and exaggerated form of early postinfarction pericarditis. Clinically, post-myocardial infarction syndrome is manifested by fever, malaise, chest pain, and the presence of a pericardial and possibly pleuropericardial friction rub. Pericardial effusion is frequently large, and, rarely, cardiac tamponade may develop and require pericardiocentesis. Treatment consists of aspirin, NSAIDs, or corticosteroids.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1989

Short-duration, high-dose urokinase infusion for recanalization of occluded saphenous aortocoronary bypass grafts.

Thrombolytic recanalization of arterial bypass grafts has been pursued aggressively in the peripheral circulation but not in the coronary circulation. In an attempt to apply peripheral transcatheter thrombolytic techniques to the coronary circulation, nine patients with 10 occluded saphenous aortocoronary bypass grafts underwent recanalization procedures using a short-duration, high-dose urokinase infusion. Urokinase was infused at the occluded graft orifice at a rate of 600 units/min. The average infusion time was 1 hr, 26 min. The average urokinase dose was 435,000 units. Graft recanalization was achieved in eight (80%) of 10 grafts, although only six (60%) of 10 grafts were widely patent at the end of the procedure. All successfully recanalized grafts required balloon angioplasty of underlying stenoses. No complications, specifically myocardial infarction or cerebrovascular accident, were encountered. We have shown that occluded aortocoronary bypass grafts can be recanalized successfully by using a short-duration, high-dose urokinase infusion. It appears that, with attention given to angiographic techniques that minimize clot manipulation, recanalization can be accomplished safely in a majority of cases.

Adult↗
PubMed1986

Pulmonary function tests in the detection of left heart failure: correlation with pulmonary artery wedge pressure.

Standard pulmonary function tests, including lung volumes measured by three fundamentally different techniques, were performed in 40 patients undergoing cardiac catheterization. These were compared with clinical and radiologic evaluations in detecting left heart failure (LHF). Patients with elevation in mean pulmonary artery wedge pressure (PAWM) greater than or equal to 20 mm Hg had significant restrictive changes with reduction in vital capacity (VC), forced expiratory volume in 1 s (FEV1.0), and total lung capacity (TLC) measured by helium dilution and body plethysmography. Radiographic TLC was not reduced in these patients or correlated with PAWM. Obstructive changes were not present. Radiologic gradings by 5 different observers were reasonably accurate in detecting LHF but varied between observers. VC and TLC measured by helium dilution and body plethysmography were slightly less sensitive but more specific in detecting PAWM elevation. Clinical classification was sensitive but nonspecific; in addition, clinical signs were not reliable indicators of elevated PAWM. We conclude that pulmonary function testing may provide objective, accurate, and useful information in the evaluation of cardiac patients for LHF. However, radiographic measurement of thoracic cage volume does not reflect the changes in lung gas volume measured by gas dilution or plethysmographic techniques in patients with chronic congestive heart failure.

Adult↗
PubMed1985

Paradoxical pulmonary vasoconstriction induced by nitroglycerin in idiopathic pulmonary hypertension.

Administration of intravenous nitroglycerin in a patient with idiopathic pulmonary hypertension resulted in an increase in pulmonary artery pressure associated with a decrease in blood flow that is best explained by an increase in pulmonary vascular resistance. This observation highlights the need for hemodynamic monitoring when potent vasodilators are used in this disorder.

Adolescent↗
PubMed1985

Fiberoptic angioscopy: role in the diagnosis of chronic pulmonary arterial obstruction.

We evaluated the role of fiberoptic angioscopy in eight patients with suspected chronic pulmonary embolic obstruction of the pulmonary arteries. Angioscopy, preceded by ventilation-perfusion lung scans, right-heart catheterization, and pulmonary angiography, resulted in diagnostic changes in four patients: from pulmonary artery agenesis to chronic emboli; from chronic emboli to normal pulmonary arterial intima (primary pulmonary hypertension); from chronic pulmonary emboli to extrinsic compression of a major pulmonary artery (fibrosing mediastinitis); and from suspected agenesis or chronic emboli to a tumor (fibrosarcoma) of the pulmonary artery. Angioscopy also more accurately determined the extent and surgical accessibility of chronic embolic obstruction in the five patients with that disorder; as a result, we decided that the obstruction in one patient was inoperable. No significant complications occurred with angioscopy and we conclude that its direct visualization capability can contribute significantly to the diagnostic evaluation of suspected chronic pulmonary arterial obstruction.

Adult↗
PubMed1984

Effects of atrial pacing on global and regional left ventricular function in coronary heart disease assessed by digital intravenous ventriculography.

Digital i.v. ventriculography in conjunction with rapid atrial pacing was used to assess the effects of ischemic stress on global and regional function in 22 patients referred for cardiac catheterization (5 had normal coronary arteries and 17 had greater than 70% diameter reduction of at least 1 major coronary artery). End-diastolic, end-systolic and stroke volume indexes and the ejection fraction were determined by an area-length technique from the mask mode images before and after pacing. In addition, segmental responses were quantitated using a radial shortening method. Subjects with normal coronary arteries showed no overall change in the postpacing volume or ejection fraction indexes. Coronary patients showed no overall change in postpacing end-diastolic volume (86 +/- 25 ml/m2 at control vs 90 +/- 31 ml/m2 after pacing, difference not significant), but there was a significant increase in end-systolic volume (25 +/- 15 ml/m2 at control vs 32 +/- 18 ml/m2 after pacing, p less than 0.005) and a decrease in ejection fraction (72 +/- 11% at rest vs 64 +/- 18% after pacing, p less than 0.025). Furthermore, quantitative deterioration in wall motion was seen in 14 of 17 coronary patients (82%) and in none of the normal patients. Analysis of segmental wall motion was the most sensitive diagnostic variable. A combination of atrial pacing stress testing and digital i.v. ventriculography is useful in detecting functionally significant coronary disease through quantitation of global and regional dysfunction which does not require arterial cannulation.

Adult↗
PubMed1984

Interaction between systolic and diastolic time intervals in atrial fibrillation.

To assess determinants of left ventricular filling time at rest simultaneous phonocardiograms, M mode echocardiograms, and indirect carotid pulse traces were performed on 50 patients with atrial fibrillation. Thus the effect of random variation in RR interval in the absence of atrial contraction on the inter-relation between systolic and diastolic events could be seen. Left ventricular filling time was closely related to RR interval and affected by it to a much greater extent than ejection time, so that filling time became very short when heart rate was fast. Two mechanisms were, however, identified whereby filling time was preserved: (a) prolongation of filling during the pre-ejection period of the following cycle, so that when the RR interval was less than 400 ms all of ventricular filling frequently occurred at this time; and (b) abbreviation of the QA2 interval of the succeeding beat with reduced filling, so that mitral valve opening occurred early. Changes in the duration of isovolumic contraction or relaxation time were not involved, neither could alteration in left ventricular contractile state resulting from variation in the interval between beats be shown to affect time at rest. The striking sensitivity of left ventricular filling time to rapid heart rate in atrial fibrillation suggests that it may be a major factor limiting cardiac performance. Diastolic as well as systolic events should, therefore, be taken into account when the effects of drugs or other physiological manoeuvres are studied in these patients.

Adult↗
PubMed1984

Delayed postoperative cardiac tamponade mimicking severe tricuspid valve stenosis.

A patient developed acute, severe hemodynamic deterioration five days after an aortic valve replacement. Cardiac catheterization revealed a markedly elevated right atrial pressure but a normal right ventricular end-diastolic pressure. Angiography revealed an extrinsic mass causing compression of the right atrium and the tricuspid anulus. A large clot overlying the right atrium and ventricle was found at emergency surgery. Postoperative cardiac tamponade may result in an atypical hemodynamic presentation when there is selective compression of one chamber or of a valve anulus.

Acute Disease↗
PubMed1983

Comparison of digital intravenous ventriculography with direct left ventriculography for quantitation of left ventricular volumes and ejection fractions.

Digital images of the left ventricle obtained at 30 frames/second from continuous fluoroscopy after intravenous injection of contrast medium (digital intravenous ventriculography) were used to estimate left ventricular (LV) volumes and ejection fraction with use of several techniques for identifying the ventriculographic silhouette. The digital technique was compared with direct contrast left ventriculography in 26 patients undergoing diagnostic cardiac catheterization. End-diastolic and end-systolic volumes calculated from digital intravenous and direct left ventriculograms were obtained with use of a standard area-length formula. Both end-diastolic volume (EDV) (r = 0.88, y = 1.06x - 17.1 ml) and end-systolic volume (ESV) (r = 0.89, y = 0.96x + 0.43 ml) determined from digital intravenous ventriculography (mask mode images) correlated closely with those obtained by direct left ventriculography. Combining the EDV and ESV to define the relation between the 2 techniques yielded an even closer correlation (r = 0.96). There was also good correlation between the 2 techniques for measurement of ejection fraction (r = 0.81, standard error of the estimate 6.7%). Measurements from direct left ventriculography were frequently invalidated by ventricular arrhythmias during the time of opacification of the left ventricle; this was rarely the case for digital intravenous ventriculography. It is concluded that area-length estimates of LV volumes and ejection fraction can be accurately obtained from digital processing of fluoroscopic LV images after intravenous injection of contrast medium.

Arrhythmias, Cardiac↗
PubMed1983

Quantitative assessment of segmental wall motion abnormalities at rest and after atrial pacing using digital intravenous ventriculography.

Digital intravenous ventriculography lends itself readily to quantitative assessment of ventricular wall motion with computer algorithms. Forty-five patients referred for cardiac catheterization were studied by digital intravenous ventriculography (mask mode) and direct ventriculography in the 30 degrees right anterior oblique position. Quantitative wall motion was analyzed by a radial shortening method applied to both studies. Lower limits of normal radial shortening were determined for each technique and used to determine the presence or absence of wall motion disorders. The inter- and intraobserver variability of radial shortening measurements was +/- 5.3 and +/- 8.8%, respectively, with maximal discrepancies of -6 and +7% fractional shortening units. The overall agreement between the two techniques in wall motion assessment was 87% (274 of 315 radii). A subset of patients also underwent atrial pacing, and a second digital intravenous ventriculogram was obtained (5 normal subjects and 15 patients with coronary artery disease). Although analysis of wall motion at rest showed a poor sensitivity for detection of significant coronary stenoses, nine of nine patients with coronary artery disease and normal wall motion at rest showed a quantitative decrease in radial wall motion after atrial pacing. Thus, digital intravenous ventriculograms can be used to provide quantitative wall motion analyses that show a high degree of agreement with those of standard, direct left ventriculography. Atrial pacing can be used to increase the sensitivity of wall motion analysis for the detection of significant coronary disease.

Aged↗