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Biomedical subjects

J B Barlow

Publications and source records attributed to J B Barlow.

At least 19 recordsLinked to original sources
PubMed1999

The quadrileaflet mitral valve: follow-up in rheumatic heart disease.

This prospective study evaluated the clinical performance of a novel stentless quadrileaflet bovine pericardial mitral valve implanted at one center since December 1996. After giving informed consent, patients were included in the study if they required isolated mitral valve replacement. All underwent comprehensive clinical evaluation, as well as transthoracic M-mode, two-dimensional and Doppler (pulsed, continuous, and color) echocardiography preoperatively and postoperatively at 1 month, 3 months, and annually thereafter. Mitral valve area was derived by planimetry, the pressure half-time method, and the continuity equation. The degree of mitral regurgitation was semi-quantitated using color Doppler. In all 38 patients with rheumatic valvular heart disease (mean age 35+/-13 years) were monitored for 13.8+/-7.5 months (range, 1 to 29 months). All but three patients are alive and symptomatically improved (functional New York Heart Association class I or II). One valve was explanted because of early prosthetic valve endocarditis. There were no episodes of thromboembolism or anticoagulation-related hemorrhage. Left ventricular function was maintained with increased cardiac output and low transmitral pressure gradients. The mitral valve area was larger when measured by pressure half-time and planimetry than by the continuity equation (P<.05). In an independent clinical evaluation of a subset of 30 patients, mitral stenosis was considered absent in 33%, mild in 30%, mild to moderate in 26%, and moderate in 10% of cases. No or less than or equal to mild mitral regurgitation was noted in the majority of patients postoperatively, both clinically and echocardiographically. We are encouraged by the clinical performance of the quadrileaflet mitral valve and with patient outcome. Long-term follow-up data are needed to assess durability.

Adult↗
PubMed1996

Cardiologic aspects of aortic valve surgery--who? when? what?

The title invites a discussion of a patient (age, lesion, physical condition, compliance, and other organ pathology) with aortic valve disease in the context of proposed surgical management. It further seeks clarification on the timing of such surgical contribution and on which operation is optimal. Without reviewing all the vast and somewhat conflicting literature, these aspects are addressed by a clinical cardiologist based principally on his own experience. Among the principal conclusions are the following: a) Surgery can safely be delayed in hemodynamically significant congenital aortic stenosis in children or young adults provided that the patients are nearly asymptomatic and that submaximal or maximal stress testing shows minimal or no ST-T changes. b) Prognosis after successful valve surgery for critically tight aortic stenosis in middle-aged and elderly patients differs from that for aortic regurgitation in that left ventricular myocardial dysfunction, however severe, will always improve postoperatively in the former condition. There is, therefore, never a cardiac contraindication to surgical management of symptomatic patients with tight aortic stenosis. c) Certain features in cases of chronic severe aortic regurgitation, such as diminished ejection fraction, increased end-systolic left ventricular diameter, electrocardiographic repolarization abnormalities, marked cardiomegaly on radiologic examination, and NYHA class III or IV symptoms, reflect a higher operative mortality and poorer long-term prognosis. Nevertheless, none of these features, alone or combined, can to date justify a definite contraindication to surgery in a specific patient. d) There is little uniformity or agreement among surgeons, including their cardiologists if or when that is pertinent, on the type of operation for patients of any age requiring aortic valve surgery. For example, a patient aged 40 years and depending on the "whims and fancies" of a Department or indeed those of an individual surgeon, which include his own judgement of his technical ability, may be subjected to a repair, a Ross procedure, insertion of a homograft or replacement with one of a variety of bioprosthetic and mechanical valves. The reasons, logic or motives behind these different choices are sometimes difficult, certainly for this author, to comprehend. Hopefully, ongoing international experience and research endeavors will, at least partially, clarify the current confusion. There is presumably an "optimal" way to hold a golf club or to kick a football?! The skill and judgement of the operators will, inevitably and sometimes regrettably, always vary.

Adolescent↗
PubMed1996

Mitral valve disease: a cardiologic-surgical interaction.

The respective roles of cardiologist and cardiac surgeon in the operative management of any specific case of mitral valve disease are variable. The range from the prevalent complete predominance of the surgeon through meaningful interaction between the two, concerning the timing and type of surgery, to predominance of the cardiologist when the surgeon accepts a role of technician. There are a number of scenarios in mitral valve surgery in which a reduced risk of postoperative hospital mortality and morbidity, by performing the simplest and shortest procedure, have to be balanced against enhanced peri-operative problems when other aspects are addressed that improve, sometimes markedly, the long-term prognosis. It is argued that a mildly stenotic aortic valve should often be replaced at the time of mitral valve surgery; that despite technical difficulties and a variable long-term postoperative course, surgeons should continue to repair rather than replace the mitral valves of young patients with severe mitral regurgitation despite the invariable presence of active rheumatic carditis; and that excess leaflet tissue and lax chordae in cases of degenerative mitral regurgitation are casually related to multifocal and potentially fatal ventricular ectopy. The crucial but neglected role of an organically abnormal tricuspid anulus in allowing dilatation and hence tricuspid regurgitation in patients with rheumatic mitral valve disease is considered in some detail. Such dilatation may occur late after mitral valve surgery for rheumatic disease, has generally and incorrectly been regarded as "functional" tricuspid regurgitation, contributes importantly to the postoperative "restriction-dilatation syndrome" and can be effectively prevented, or when once established then surgically managed, by a modified De Vega anuloplasty. Finally it is believed that, unlike mitral balloon valvuloplasty in selected instances, successful tricuspid balloon valvuloplasty can never be accomplished without causing significant tricuspid regurgitation and the procedure should be abandoned.

Aortic Valve Stenosis↗
PubMed1994

The spectrum of severe rheumatic mitral valve disease in a developing country. Correlations among clinical presentation, surgical pathologic findings, and hemodynamic sequelae.

OBJECTIVE: To describe the demographic, pathologic, and hemodynamic profiles of patients with severe rheumatic mitral valve disease in a developing country and to assess their relation to uncontrolled rheumatic disease activity. DESIGN: Retrospective, cross-sectional, cohort study. SETTING: Tertiary medical center in Soweto, South Africa. PATIENTS: 714 of 737 consecutive black patients, 4 to 73 years old, with pure mitral regurgitation, pure mitral stenosis, or mixed mitral disease who had mitral valve surgery and in whom preoperative and surgical data were concordant. MEASUREMENTS: Valve lesions were evaluated on the basis of clinical, echocardiographic, hemodynamic, and surgical pathologic data. Active rheumatic carditis was diagnosed according to clinical evidence for concurrent acute rheumatic fever (Jones criteria), macroscopic appearances at surgery, and histologic findings. RESULTS: 219 patients had pure mitral regurgitation, 275 had pure mitral stenosis, and 220 had mixed lesions. Ongoing rheumatic activity was diagnosed in 106 patients with pure regurgitation (47%) and in only 5 patients with pure stenosis (2%). Pure regurgitation was the most common lesion in the first and second decades; the relative prevalence of pure stenosis increased with age. Purely regurgitant valves had pliable, unscarred leaflets (95%), dilated mitral annuli (95%), elongated chordae tendineae (92%), and anterior leaflet prolapse (81%). In contrast, purely stenotic valves had fused leaflet commissures (100%) and rigid leaflets (38%) but no evidence of prolapse. CONCLUSIONS: The spectrum of rheumatic mitral valve disease that is hemodynamically severe in developing countries differs from that currently reported in the United States. Severe, pure rheumatic mitral regurgitation is as prevalent as pure stenosis but has an entirely different time course, surgical anatomy, and relation to disease activity, suggesting a separate pathophysiologic mechanism.

Adolescent↗
PubMed1992

Mitral valve billowing and prolapse--an overview.

Three decades after it was demonstrated that nonejection systolic clicks and late systolic murmurs have a mitral valve origin and that a specific syndrome is associated with the primary degenerative mitral lesion, numerous questions remain unanswered. A principal cause of confusion is the use of the term 'prolapse', which essentially implies a pathological state, in many patients with minimal evidence of a mitral valve anomaly. It should be recognised that no specific feature, whether evaluated by high standard echocardiography or indeed by careful morphological and histological examination, can be defined which distinguishes a normal variant from a pathological valve. There is a gradation from the normal billowing during ventricular systole of mitral leaflet bodies to marked billowing. With advanced billowing or floppy leaflets, failure of leaflet edge apposition supervenes (true prolapse). This is functionally abnormal and allows mitral regurgitation. Prolapse in turn may progress to a flail leaflet and hence gross regurgitation. Relatively rare complications of this degenerative mitral valve anomaly include systemic emboli, infective endocarditis, arrhythmias and, arguably, autonomic nervous system abnormalities. An attempt is made to clarify the management of some symptoms and other aspects of mitral prolapse-including rheumatic anterior leaflet prolapse (without billowing) which remains prevalent in South Africa and Third World countries.

Arrhythmias, Cardiac↗
PubMed1992

Aspects of active rheumatic carditis.

Fulminating active rheumatic carditis has been observed for over 3 decades in this environment with no recent alteration in either the incidence or the pattern of presentation. Patients are black, seldom older than 20 years and are usually in their early teens but may occasionally be as young as five years. Heart failure is prevalent but occurs only when a haemodynamically important left-sided valve lesion supervenes. Regurgitation is the predominant valve lesion and involves principally the mitral valve. Mitral annular dilatation is the initial pathology and predisposes to lengthening--or rupture--of chordae tendineae and prolapse of the anterior leaflet. The resultant cardiac work-overload apparently perpetuates the rheumatic activity. Heart failure, whether caused by or associated with active rheumatic carditis, makes surgical management of the valve lesion mandatory as a life-saving measure. Mitral valve repair, rather than replacement, is the surgical procedure of choice but is not always practicable when the rheumatic activity is fulminant, significant aortic regurgitation associated or the surgeon relatively inexperienced. Aggressive medical therapy for heart failure, which should include vasodilator drugs, provides temporary improvement only. Contrary to ongoing doctrine, treatment with steroid drugs is neither life-saving nor beneficial. Varying degrees of left ventricular dysfunction are encountered pre-operatively and may be a sequel of the severe regurgitant valve lesion rather than of a rheumatic 'myocardial factor'.

Acute Disease↗
PubMed1992

The importance of assessing time-course behaviour of abnormal ST/T changes after exercise.

Routine stress electrocardiography has been criticised for yielding too many so-called 'false-positive' results because ST/T changes that develop during and after exercise are prevalent. Recent studies in our institution indicate, however, that the time-course behaviour patterns of these ST/T configurational 'abnormalities' after exercise are different from those reflecting myocardial ischaemia due to epicardial coronary artery disease (CAD). Time-course analysis increases the predictive value of exercise testing and has dramatically decreased the number of asymptomatic subjects or symptomatic patients at low risk of having CAD being subjected to coronary arteriography in our institution. Our method of assessing post-exercise time course patterns of abnormal ST/T are described in detail. Ischaemic ST/T abnormalities have late onset, early offset or early onset, late offset whereas those ST/T changes associated with normal epicardial coronary arteries have late onset, late offset or early onset, early offset post-exercise time course patterns.

Coronary Disease↗
PubMed1991

Observer accuracy and confirmation of the important role of abnormal ST/T time course behavior in the evaluation of stress electrocardiograms.

Routine exercise electrocardiography has been criticized for yielding too many so-called "false-positive" results. Recent studies in our institution indicate that evaluation of the time course behavior of ST segment and T wave (ST/T) changes after cessation of exercise differentiates ischemic from non-ischemic ("false-positive") stress electrocardiograms (SEs). Our method of assessing time course behavior is clarified. The principal aim of this study was to determine the accuracy of experienced observers in making this differentiation. Records of consecutive patients undergoing coronary arteriography over a 2 year period were reviewed and 30 with SEs judged positive for ischemia by the widely accepted ST/T configurational criteria alone were selected at random for the investigation. Sixteen subjects had normal coronary angiograms and had therefore previously been regarded as having false-positive SEs. Fourteen patients had at least one significantly (> 70%) stenosed coronary artery which was our yardstick for ruling that true myocardial ischemia, due to epicardial coronary artery disease (CAD), was present. Five observers, familiar with post-exercise ST/T time course patterns, independently and "blindly" analyzed all 30 configurationally abnormal SEs. Observers were informed only of the patient's age and sex; they were thus unaware of symptoms, exercise variables, coronary anatomy and the number of patients in the 2 groups. The observer consensus for ischemia of SEs using time course analysis was: total test accuracy 87%, sensitivity 79%, specificity 94%, positive predictive value 92% and negative predictive value 83%. Because all 30 patients had ST/T abnormalities, results of the sample for ischemia based on configurational criteria alone were sensitivity 100%, specificity 0% and positive predictive value 47%. We concluded that time course analysis plays a crucial role in evaluating SEs and that exercise electrocardiography remains a safe, cost-effective and reliable method of screening many asymptomatic, as well as symptomatic, subjects for CAD.

Coronary Angiography↗