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Biomedical subjects

M M Webb-Peploe

Publications and source records attributed to M M Webb-Peploe.

At least 19 recordsLinked to original sources
PubMed2004

Coronary angiography using a portable super-C-arm imaging system in a district general hospital.

BACKGROUND: New generation portable super-C-arm imaging systems may offer an alternative means of performing coronary angiography at a lower cost compared with a fixed laboratory. We evaluated the use of one such system (GE-OEC 9800) in a district hospital setting. METHODS: The demographics, procedure and screening times, emitted radiation dose and diagnoses of the first 200 consecutive patients were obtained from a prospective database. Comparison between the portable and fixed systems were made by analysing results from similar cohorts of patients who underwent angiography by the same operators. Image quality was assessed in 23 patients, by an independent cardiologist, comparing the GE-OEC 9800 angiograms with repeat images using a fixed laboratory Philips (HM 3000) system within 3 months of the first study. RESULTS: The procedure time (mean (S.D.)) was 18.9 (0.8) min for the 200 cases. The screening time was 255 (15) s with an emitted radiation of 22.8 (1.4) Gy/cm(2). Comparison between the C-arm and fixed systems revealed significantly longer screening time (230.6 (14.6) vs. 157 (12.9) s, p<0.001), whilst the total radiation doses were not significantly different (21.1 (1.5) vs. 18.6 (1.11) Gy/cm(2)). Independently assessed image quality was satisfactory. The main variance in 57 lesions seen in the 23 patients using the angiograms obtained from the fixed laboratory as reference included overestimated stenosis (two lesions), underestimated stenosis (or subsequent disease progression) (four lesions), lack of appreciation of side-branch ostial involvement (two lesions) and vessel calcification (one lesion). CONCLUSIONS: Portable imaging systems can offer a reliable and cost-effective diagnostic coronary angiography service in a district hospital.

Coronary Angiography↗
PubMed2001

Comparison of myocardial fractional flow reserve and intravascular ultrasound for the assessment of slotted-tube stents.

Intravascular ultrasound (IVUS) and myocardial fractional flow reserve (FFR) have been reported to provide similar results for assessment of coil stent deployment. Their relative value in slotted-tube stents has not been investigated. Fourteen patients subjected to coronary angioplasty and IVUS-guided elective stenting with a slotted-tube stent underwent IVUS assessment and FFR measurement following stent implantation at inflation pressures of 12 and 18 atm. FFR values (mean +/- SD) preangioplasty, postangioplasty, and poststenting at 12 atm and 18 atm, were 0.58 +/- 0.07, 0.83 +/- 0.05, 0.94 +/- 0.02, and 0.94 +/- 0.02, respectively. After inflation at 12 atm, the area under the receiver operating characteristic (ROC) curve for the concordance of IVUS and FFR measurements was 0.89 (P = 0.02). Six patients had either an abnormal IVUS (n = 2) or FFR < 0.94 (n = 1) or both abnormal IVUS and FFR < 0.94 (n = 3) after the first inflation and had a second inflation at 18 atm. The area under the ROC curve for the concordance between IVUS and FFR final measurements was 0.855 (P = 0.10). Perfect concordance between IVUS and FFR was seen only for FFR values less than 0.91 or larger than 0.94. Overall, IVUS and FFR have substantial concordance with respect to slotted-tube stent deployment. However, FFR values between 0.91 and 0.94 after inflation are difficult to interpret.

Aged↗
PubMed2001

C-Reactive protein concentrations and angiographic characteristics of coronary lesions.

BACKGROUND: C-Reactive protein (CRP) is a strong predictor of clinical outcome in coronary artery disease (CAD), and inflammation has been implicated in the process. We aimed to evaluate whether CRP concentrations measured with a new, automated particle-enhanced immunoturbidimetric method for high-sensitivity CRP may be related to specific high-risk angiographic features of coronary lesions. METHODS: In a cross-sectional study, we examined 103 consecutive patients undergoing cardiac catheterization for suspected CAD. We assessed the association of preprocedural CRP concentrations with clinical presentation (unstable angina) and angiographic features of coronary lesions. RESULTS: Twenty patients had unstable angina. Independent predictors of unstable angina included increased CRP [odds ratio (OR), 2.93 per 10-fold increase in CRP; 95% confidence interval (CI), 1.28-6.69; P = 0.01] and the presence of macroscopic thrombus (OR, 7.08; 95% CI, 1.33-37.8; P = 0.02). Thirty-two culprit lesions had macroscopic thrombus or eccentric/irregular discrete morphology without total occlusion. Increased CRP was the strongest predictor of such features (OR, 2.04 per 10-fold increase in CRP; 95% CI, 1.03-4.04; P = 0.04), and the effect was independent of the presence of unstable angina. CONCLUSIONS: Among patients with suspected CAD undergoing coronary angiography, increased CRP is strongly associated with unstable angina and with specific high-risk features of the culprit coronary lesions.

Aged↗
PubMed2000

Radiation exposure of patients and coronary arteries in the stent era: A prospective study.

Previous studies have investigated the radiation dose to doctors and patients during coronary angiography and angioplasty, but most of them were retrospective, conducted in the prestent era, and results have not been consistent. Effective dose of 57 patients undergoing coronary angiography and/or angioplasty was assessed by using a dose-area product (DAP) to effective dose conversion factor. Radiation exposure risks to patients were then calculated for each procedure. Thermoluminescent dosimeters, mounted on a specially designed catheter that was advanced to the left or right sinus of Valsalva, were used to measure the dose received by the coronary arteries. Mean effective dose received by patients were 5.0 +/- 0.5 mSv for coronary angiography, 6.6 +/- 1.0 mSv for angioplasty, 10.2 +/- 1.5 mSv for angioplasty followed by stent implantation, 13.6 +/- 2.5 mSv for angiography followed by ad hoc angioplasty, and 16.7 +/- 2.8 mSv for angiography followed by ad hoc angioplasty and stent implantation. Patient risk of developing cancer after each procedure was 0.025%, 0.033%, 0.051%, 0.068%, and 0.084%, respectively. Corresponding mean coronary irradiation doses were 24 +/- 2.5, 31.0 +/- 3.6, 43.6 +/- 7.2, 55.0 +/- 7.5, and 64.7 +/- 5.6 mGy, respectively. A linear relationship of the DAP and the dose at the coronary arteries was found: DAP = 1,273 (cm(2)) x coronary dose (mGy). Radiation exposure to coronary arteries and associated risk to patients are relatively low, even following complicated, multivessel angioplasty with stent implantation. Our method can be used for calculation of radiation risk to patients and radiation dose to coronary arteries by using external dosimeters. Cathet. Cardiovasc. Intervent. 51:259-264, 2000.

Adult↗
PubMed2000

Release of platelet activation markers during coronary angioplasty.

BACKGROUND: Authors of several studies have reported that activation of platelets occurs during coronary angioplasty, but consistent results have not been obtained. Levels of serotonin in coronary circulation have been found to be elevated during percutaneous transluminal coronary angioplasty but greater than normal concentrations of beta-thromboglobulin and platelet factor 4 have not been detected. OBJECTIVE: To perform a serial analysis of platelet-activation markers with simultaneous measurements of levels of serotonin, beta-thromboglobulin and platelet factor 4 in blood samples from the coronary artery and coronary sinus of patients undergoing coronary angioplasty. METHODS: Twenty patients undergoing elective coronary angioplasty were studied. Measurements of levels of beta-thromboglobulin, platelet factor 4, and serotonin in samples from the ostium of the coronary artery and the coronary sinus were performed immediately before angioplasty and after the first balloon deflation. RESULTS: Concentrations of beta-thromboglobulin and platelet factor 4 in coronary artery and coronary sinus were elevated in all patients before dilatation, whereas concentrations of serotonin were elevated in 85% of the patients. Concentrations of all markers in coronary sinus decreased after the first inflation. The coronary-sinus: coronary-artery concentration ratios before dilatation for beta-thromboglobulin, platelet factor 4, and serotonin were > 1 for the majority of patients, particularly for those with complex culprit lesions, indicating that coronary activation of platelets was occurring. Ratios remained unchanged or decreased after the first inflation, depending on initial values. CONCLUSIONS: Both systemic and coronary activation occur in patients subjected to percutaneous transluminal coronary angioplasty before the onset of intervention. After balloon deflation the greater than normal baseline coronary-sinus:coronary-artery concentration ratios of all markers (beta-thromboglobulin, platelet factor 4 and serotonin) tend to decline or remain unchanged, depending on the level of activation.

Adult↗
PubMed1999

Laser angioplasty of restenosed coronary stents: results of a multicenter surveillance trial. The Laser Angioplasty of Restenosed Stents (LARS) Investigators.

OBJECTIVES: This study evaluated safety and efficacy of excimer laser angioplasty for treatment of restenosed or occluded coronary stents. BACKGROUND: Balloon angioplasty of in-stent restenosis is limited by a high recurrence rate. Debulking by laser angioplasty is a novel concept to treat in-stent restenosis. METHODS: A total of 440 patients with restenoses or occlusions in 527 stents were enrolled for treatment with concentric or eccentric laser catheters and adjunctive balloon angioplasty. RESULTS: Laser angioplasty success (< or =50% diameter stenosis after laser treatment or successful passage with a 2.0-mm or 1.7-mm eccentric laser catheter) was achieved in 92% of patients. Adjunctive balloon angioplasty was performed in 99%. Procedural success (laser angioplasty success followed by < or =30% stenosis with or without balloon angioplasty) was 91%. There was neither a significant difference in success with respect to lesion length, nor were there differences between small and large vessels or native vessels and vein grafts. Success was higher and residual stenosis lower using large or eccentric catheters. Serious adverse events included death (1.6%, not directly laser catheter related), Q-wave myocardial infarction (0.5%), non-Q-wave infarction (2.7%), cardiac tamponade (0.5%) and stent damage (0.5%). Perforations after laser treatment occurred in 0.9% of patients and after balloon angioplasty in 0.2%. Dissections were visible in 4.8% of patients after laser treatment and in 9.3% after balloon angioplasty. Reinterventions during hospitalization were necessary in 0.9% of patients; bypass surgery was performed in 0.2%. CONCLUSIONS: Excimer laser angioplasty with adjunctive balloon angioplasty is a safe and efficient technology to treat in-stent restenoses. These data justify a randomized comparison with balloon angioplasty.

Adult↗
PubMed1997

Cannulation of the coronary sinus via the femoral vein--a new technique.

BACKGROUND: Cannulation of the coronary sinus usually has been accomplished by advancing a catheter through the sub-clavian or internal jugular veins. HYPOTHESIS: We have developed a new technique for cannulation of the coronary sinus with a modified 6F Judkins L5 coronary catheter positioned through the femoral vein. RESULTS: The technique was tried successfully in 20 consecutive patients by the same operator and the average fluoroscopy time for coronary sinus cannulation was 1.6 +/- 1.0 min. CONCLUSION: Analysis of the results showed evidence of a learning curve with improvement of time with an increasing number of patients. The method provides a safe and inexpensive solution for catheterization of the coronary sinus, easily accessible to every catheter laboratory.

Catheterization, Peripheral↗
PubMed1993

Regional sympathetic innervation of the heart by means of metaiodobenzylguanidine imaging in silent ischemia.

Metaiodobenzylguanidine was used to determine regional cardiac sympathetic innervation and whether it is reduced in silent ischemia. Patients with silent ischemia (group 1, n = 6) and angina (group 2, n = 5) and normal subjects (n = 6) underwent single-photon emission tomography at 4 hours. From base to midventricle, uptake increased in group 1 (p < 0.006), group 2 (p < 0.01), and the normal subjects (p < 0.004). In group 1 anterior ventricular uptake was greater than inferior uptake at the midventricle (p < 0.03) and apex (p < 0.05). In group 2 the same relationship was demonstrated at midventricle (p < 0.01) and apex (p < 0.05). Group 2 uptake was only significantly greater than group 1 at midventricle (p < 0.05). Innervation is greatest in midventricle and the apex of the left ventricle and greater in the anterior wall compared with the inferior wall. There is no evidence of reduced innervation in silent ischemia.

3-Iodobenzylguanidine↗
PubMed1993

Initial experience with excimer laser angioplasty for coronary ostial stenoses.

The excimer laser has several potential advantages over conventional balloon angioplasty in the management of stenoses of the native coronary arteries and of the ostia of saphenous vein grafts. Its use in nine patients, eight of whom were classed as high risk, is described. Four lesions involved the ostia of saphenous vein grafts, three of protected left main stems, and two of native right coronary arteries. Stand alone laser was used in seven cases and laser with additional balloon angioplasty was used in two vein graft stenoses. Acute laser success was achieved in all cases, with a mean reduction of stenosis from 82% to 34% after laser alone and to 28% when balloon angioplasty was used as well. One patient died during laser angioplasty to a non-ostial lesion (procedural success rate 89%) and a second died ten weeks after the procedure. In one patient recurrent angina developed (clinical recurrence rate 25%) and restenosis was confirmed on angiography. Follow up angiography was also performed on the other six surviving patients, all of whom were symptom free and none of whom showed evidence of significant restenosis (restenosis rate 14%). With a mean follow up of 19.7 months the overall success rate was 67%.

Aged↗
PubMed1993

Effect of aortic valve replacement on syncope in patients with aortic stenosis.

OBJECTIVE: To determine the role of exertion as a precipitating factor in syncope in patients with aortic stenosis. DESIGN: Follow up for at least one year after aortic valve replacement. SETTING: Regional cardiac centre. PATIENTS: Consecutive patients who underwent aortic valve replacement for aortic stenosis and who had a history of syncope and no other clinically significant cardiac lesion were recruited during a five year period. METHODS: Patients were interviewed to determine the characteristics of syncope and were divided into those in whom syncope was consistently related to exertion (group 1, 26 patients) and those in whom it was not (group 2, 13 patients). Recurrence of syncope after valve replacement was determined at visits to the clinic. RESULTS: Groups 1 and 2 did not differ significantly with respect to valve area, age, or sex. In 13 of the 26 patients in group 1 syncope was preceded by angina despite the absence of coronary artery disease, but none of the 13 patients in group 2 had angina. After valve replacement none of group 1 and eight of the 13 patients in group 2 had recurrence of syncope (p < 0.01). CONCLUSION: When patients with aortic stenosis experience syncope unrelated to exertion, the symptom is usually unrelated to the valve disease and another cause should be sought.

Aged↗
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

Mechanical restitution of isolated human ventricular myocardium subjected to in vivo pressure and volume overload.

OBJECTIVE: The aim was to make a comparison of the mechanical and electrical refractory properties of isolated strips of human ventricular myocardium obtained from patients with either left ventricular pressure overload, volume overload, or normal left ventricular function. METHODS: Strips of ventricular myocardium were obtained at the time of cardiac surgery from 17 patients with aortic stenosis, representing pressure overload, 14 patients with aortic regurgitation, representing volume overload, and nine patients with mitral stenosis, representing normal left ventricular function. Muscle strips were mounted isometrically in a tissue bath, superfused with physiological saline at 37 degrees C, and stimulated at 1 Hz. Mechanical restitution curves were constructed from the isometric twitch tension obtained from extrastimuli during a special stimulus protocol. Transmembrane action potentials were recorded using glass microelectrodes and restitution of the upstroke velocity of action potentials studied in the presence of high external potassium concentration. RESULTS: The aortic stenosis group was older and had higher left ventricular systolic pressures and thicker left ventricular walls than the other groups. Electrocardiographic evidence of left ventricular hypertrophy was present in both the aortic stenosis and aortic regurgitation groups. Peak tension, time to peak tension, and the maximum rates of rise and fall of tension were not significantly different between groups. The time constant of the initial rapid recovery phase of mechanical restitution (tau 1) was prolonged in the aortic stenosis group, at 603(SEM 80) ms v 367(53) ms in the aortic regurgitation group (p < 0.005), and 259(70) ms in the mitral stenosis group (p < 0.005). There was a positive correlation between tau 1 and left ventricular wall thickness (p < 0.05). Neither "normal" nor "slow" (in the presence of raised external potassium) transmembrane action potentials differed in the groups studied. The mean time constant of recovery of "slow" action potential dV/dtmax was slower in the aortic stenosis group, but this difference was not significant. CONCLUSIONS: These data are consistent with the hypothesis that the rate of recovery of calcium release from the sarcoplasmic reticulum is slowed in myocardial hypertrophy due to pressure overload in man and provides a possible explanation of the occurrence of mechanical alternans in such patients.

Action Potentials↗
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

Echocardiographic left ventricular wall thickness: a poor predictor of the severity of aortic valve stenosis.

Echocardiographic left ventricular hypertrophy is thought to be helpful in grading the severity of aortic stenosis. This study compared M-mode echocardiographic left ventricular wall dimensions with Gorlin aortic valve area. Good quality echocardiograms were obtained in 294 patients with aortic stenosis who also underwent cardiac catheterization. Patients with grade 3 or 4 aortic regurgitation were excluded. The correlation was calculated between the aortic valve area and the left ventricular wall dimensions. Correlation coefficients were poor; r = 0.13 for the septum, r = 0.15 for the posterior wall, and r = 0.17 for the mean wall dimension. Correlation was not improved significantly if patients with poor left ventricular function or systemic hypertension were excluded. Correlation with other hemodynamic parameters was better, peak left ventricular systolic pressure having r values of 0.36 and 0.30 for posterior wall and septum. Mean and peak aortic valve gradient had r values approaching 0.30 for both dimensions. If the peak gradient was included in multivariate analysis, the wall dimensions then had no predictive power for severity of aortic stenosis. This study demonstrates that the degree of left ventricular wall hypertrophy is not related to the severity of aortic outflow obstruction and therefore cannot be used to grade the severity of aortic stenosis.

Aortic Valve↗