Biomedical subjects
Publications and source records attributed to D S Dymond.
An unusual complication of transvenous endocardial lead placement is reported in which an electrode became entrapped within the vicinity of the tricuspid valve apparatus, resisting all initial attempts at removal. The lead was subsequently successfully removed percutaneously via the right femoral vein.
OBJECTIVES: The concept of "cardioprotection" based on ejection fraction was tested to see whether patients with coronary artery disease in whom medical treatment fails to be cardioprotective can be distinguished from those in whom it is safe to continue such treatment. BACKGROUND: Ejection fraction is of fundamental prognostic importance. Its modification by anti-ischemic medication may allow assessment of cardioprotection from adverse outcome. METHODS: Exercise ejection fraction and the change in ejection fraction from rest to exercise were measured by radionuclide ventriculography with and without background medication in 102 mildly symptomatic patients with coronary artery disease suitable for revascularization but initially treated medically. RESULTS: Over 20 months, 23 patients experienced an adverse event. With medication, exercise ejection fraction increased in patients with and without events. By contrast, the ejection fraction response to exercise improved significantly in the event-free group only; the group with events had a persistent decrease in ejection fraction. By Cox analysis, the ejection fraction response to exercise performed with medication made the most significant independent contribution to event-free survival. Comparison of areas under receiver operating characteristic curves suggested that this index is the most useful clinical measure of cardioprotection. CONCLUSIONS: An exercise-induced decrease in ejection fraction despite anti-ischemic medication implies failure of cardioprotection and a greater short-term risk of adverse outcome and crossover to revascularization in patients initially treated medically. Conversely, a preserved left ventricular performance confers a satisfactory prognosis while continuing with that treatment. Thus, the effect of medication on the ejection fraction response to exercise--a reasonable estimate of its cardioprotective efficacy--may influence the choice of continuing with such treatment or performing early revascularization.
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To test the hypothesis that abolition of exercise-induced painless myocardial ischemia by anti-ischemic medication improves prognosis in patients with medically treated coronary artery disease, we studied such patients with painless ischemia during exercise radionuclide ventriculography performed after temporary discontinuation of medication. The test was repeated while patients received conventional medical therapy that rendered angina no worse than New York Heart Association class I. The relative risk of adverse cardiac events was reduced by > 5-fold when painless ischemia was abolished by symptom-dictated therapy. Thus, the abolition of exercise-induced painless ischemia by conventional medical therapy carries a better short-term prognosis in medically treated coronary artery disease, suggesting that therapeutic efficacy may need to be assessed by titration against ischemia and not angina. In patients without overt cardiac events, there were no significant differences between baseline and 12-month measurements of ejection fraction at rest, peak exercise, and the change in ejection fraction from rest to exercise. Thus, in those who remain asymptomatic and event-free, painless ischemia that is easily inducible at baseline despite medication does not lead per se to deterioration of left ventricular systolic function at rest or during exercise over 12 months. Such an effect, if evident as early as at 12 months, would favor a strategy of early revascularization over medical treatment in asymptomatic patients who have inducible painless ischemia despite medication.
OBJECTIVE: To examine how exercise testing on background medical treatment affects the ability of the test to predict prognostically important patterns of coronary anatomy in patients with a high clinical probability of coronary artery disease but who are well controlled on medication. DESIGN: Prospective study. SETTING: Regional cardiothoracic centre and referring district general hospital. PATIENTS: 84 patients with a history of typical angina or definite myocardial infarction and mild symptoms who had been placed on the waiting list for prognostic angiography. INTERVENTION: Maximal exercise electrocardiography and radionuclide ventriculography performed off and on medication, followed by angiography within three months. MAIN OUTCOME MEASURE: Prognostically important coronary artery disease for which early surgery might be recommended purely on prognostic grounds, irrespective of symptoms. RESULTS: Coronary artery disease was present in 71/84 (85%) patients; in 28/84 (33%) patients this was prognostically important. When the result was strongly positive, the predictive accuracy for prognostically important disease was 0.46 off and 0.62 on medication for the exercise electrocardiogram and 0.71 off and 0.82 on medication for exercise radionuclide ventriculography. The likelihood ratio was 1.00 off and 1.36 on medication for exercise electrocardiography and 2.54 off and 10.5 on medication for exercise radionuclide ventriculography. In stepwise logistic regression, the test identified as the strongest predictor of prognostically important disease was exercise radionuclide ventriculography on medication for which the improvement chi 2 was 28 (p < 0.0001). With the regression model, the probability of important disease is 92% if exercise radionuclide ventriculography on medication is at least strongly positive, compared with 16% if the result is normal or just positive. CONCLUSION: In patients likely to have coronary disease, exercise testing should be performed without interruption of medication to optimise its ability to identify those with prognostically important disease, and to help to avoid unnecessary or premature angiography in those who are well controlled on medical treatment.
Silent myocardial ischaemia is readily detected by exercise radionuclide ventriculography in patients with coronary artery disease. In those who remain asymptomatic and event-free, it is not known whether silent ischaemia which is inducible despite anti-ischaemic medication exerts an insidious detrimental effect on left ventricular function. To study this, 34 medically treated patients (mean age 57; 26 men) underwent prospective measurement of left ventricular ejection fraction (LVEF) during rest and exercise radionuclide ventriculography without interruption of anti-ischaemic medication at baseline and 12 months later. There was no significant mean (standard deviation, 95% confidence interval) deterioration from baseline to 12 months in LVEF at rest (50% v 49%, SD 5; 95% CI = -3 to +1), peak exercise (44% v 45%, SD 8; 95% CI = -1 to +4) and the change in LVEF from rest to exercise (-6% v -4%, SD 7; 95% CI = -1 to +5). Thus, in coronary artery disease patients who remain asymptomatic and event-free on medical therapy, silent myocardial ischaemia which is readily inducible at baseline despite medication does not lead per se to deterioration of left ventricular systolic function at rest or exercise over 12 months.
OBJECTIVE: The long-term predictability of left ventricular ejection fraction (LVEF) measurements was evaluated with particular emphasis on the assessment of deterioration in individual patients whose coronary artery disease was initially treated medically. DESIGN: Prospective pilot study. SETTING: Regional cardiac centre. PATIENTS: 60 minimally symptomatic patients with coronary artery disease who, after arteriography, were initially treated medically. INTERVENTION: Measurement of LVEF by first pass exercise radionuclide ventriculography at baseline and six months later without interruption of usual anti-ischaemic medication. Baseline and six-month studies were analysed independently of each other. MAIN OUTCOME MEASURE: Based on 51 patients who remained event free, 95% prediction intervals were derived for prognostic LVEF indices to suggest the minimum change from baseline that might be considered clinically important in the individual patient, alerting clinicians to the need for closer review. RESULTS: At six-month ventriculography, 22 patients showed apparent deterioration in exercise LVEF or the change in LVEF with exercise (delta LVEF). Only two patients had six-month values below the lower limit of 95% prediction intervals, compared with 15 when 95% group confidence intervals (z = 3.33, p < 0.001) were used. When delta LVEF = 0 at baseline, the lower limit of 95% prediction intervals allowed for an exercise induced fall at six months of < or = 13%. For a baseline exercise LVEF of 50% (just normal), the lower limit of 95% prediction intervals was 38%--that is, the exercise LVEF could be measured as low as 38% > or = six months later without necessarily indicating or missing true deterioration. CONCLUSION: In the follow up of minimally symptomatic patients with coronary artery disease, serial long-term changes, in particular "deterioration," in prognostic LVEF indices may be interpreted more meaningfully with reference to 95% prediction intervals.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
During exercise radionuclide ventriculography, many patients with coronary artery disease exhibit painless myocardial ischemia defined as an abnormal left ventricular ejection fraction response without accompanying angina. To see if complete suppression of such exercise-induced painless ischemia by anti-ischemic medication implies a better prognosis in medically treated coronary artery disease, 34 patients underwent repeat testing at 4 weeks receiving regular conventional therapy that rendered angina no worse than class I. With such therapy, painless ischemia was abolished in 12 patients (group I) and persisted in 22 (65%, group II). Both groups were similar in age, number of diseased vessels, proportion with previous myocardial infarction, exercise ejection fraction, and degree of exercise-induced painless ischemia at baseline. At 9 months, adverse events had occurred in 11 patients (2 patients with myocardial infarction, 4 with unstable angina, 2 with angioplasty and 3 with bypass surgery). Only 1 of 12 patients (8%) in group I had experienced events compared with 10 of 22 (45%) in group II (chi-square, 5.4; p less than 0.025; 95% confidence interval, 12 to 61%). Thus, the relative risk of adverse events in patients whose painless ischemia was abolished was only 18% of that in patients in whom it was persistent. These results suggest that (1) the abolition of exercise-induced painless ischemia by conventional symptom-dictated medical therapy confers a better short-term prognosis in medically treated coronary artery disease, and (2) therapeutic efficacy may need to be assessed by titration against ischemia and not against angina.
Percutaneous transluminal coronary angioplasty was attempted with elective percutaneous intra-aortic balloon pump support in 21 patients (mean age 60 years, range 40-82; 18 males) with unstable angina (n = 2), multivessel coronary disease requiring multivessel angioplasty (n = 2), severe left ventricular dysfunction (ejection fraction 10-30%; n = 16) or ventricular fibrillation at diagnostic angiography (n = 1). Fourteen patients had 3-vessel disease (1 with vein grafts also diseased), 6 had 2-vessel disease and 1 had isolated left anterior descending disease. Twenty-five procedures were performed (one in 18 patients, two in 2 patients and three in one patient) on 42 lesions in 34 vessels/grafts. There was no angioplasty-related death. Successful dilatation was achieved in 38/42 lesions (90%) in 21/25 procedures (84%) without major complication. Three procedures were complicated: one by major coronary dissection without sequelae, one by haemodynamic deterioration due to distal occlusion and one by an unstable residual stenosis in the attempted vessel necessitating urgent bypass surgery. The only complication related to the intra-aortic balloon pump was local haematoma in 2 patients. In conclusion, elective intra-aortic balloon pump support may be safely used to stabilise high-risk patients undergoing coronary angioplasty, leading to a satisfactory primary success rate.
Most count-based radionuclide methods for calculating left ventricular volume rely on measurement of radioactivity in a peripheral blood sample and a measurement of ventricle to collimator distance. We have developed a method which requires neither a blood sample nor a distance measurement and which is applicable to first-pass radionuclide angiography. The parameters used to calculate volume are the area of pixel, the total counts in the left ventricle and the maximum pixel count. The equation was used to calculate the volumes in 50 patients who had both resting first-pass radionuclide angiography (25 patients with a single crystal and 25 patients with a multicrystal camera) and contrast ventriculography on the same day. Correlation coefficients for end-diastolic and end-systolic volumes showed r ranging 0.93-0.98 and standard error of estimate ranging 23-35 ml for end-diastolic volume (14%-17% of mean end-diastolic volume) and 16-23 ml for end-systolic volume (18%-21% of mean end-systolic volume). Image processing software for extracting the needed values is generally available on most commercial nuclear medicine imaging systems and the additional time for the calculations is short. Although the theory is based on multiple assumptions, the volume calculation appears to be reasonably accurate and clinically applicable.
We examined the prognostic value of exercise radionuclide ventriculography (RNV) performed on anti-ischaemic medication following thrombolysis. Within 3 months of thrombolysis for first myocardial infarction, 31 medically treated patients with revascularisable but non-critical and minimally symptomatic coronary disease had left ventricular ejection fraction (LVEF) measured by first-pass exercise RNV. This was first performed off treatment and then repeated within 4 weeks on patients' regular medication. Follow-up at 12 months post-thrombolysis showed that 5 patients (Group I) had suffered significant recurrent symptoms (worsening angina requiring revascularisation in 3, unstable angina in 1, reinfarction in 1), but 26 remained well (Group II). Both groups were similar in age, post-thrombolytic severity of coronary disease, exercise LVEF whether off (39% vs 43%) or on medication (43% vs 44%), and change in LVEF with exercise ([symbol: see text]LVEF) off medication (-11% vs - 3%). However, on medication, there was a significant difference in mean [symbol: see text]LVEF between Groups I and II (-11% vs + 5%, P = 0.0008, 99% confidence interval = 4 to 26%). Thus, following thrombolysis, an abnormal [symbol: see text]LVEF despite anti-ischaemic medication may identify patients at risk of significant early recurrent ischaemia. Post-thrombolysis prognostic testing by exercise RNV may therefore be of greater value when performed on rather than off medication.
Twenty one patients with NYHA class II-III congestive heart failure received single ascending doses of 0.5, 1.25 and 2.5 mg cilazapril daily followed by the minimum effective dose for six weeks. Fifteen patients completed the study, but the data from only 11 were sufficiently complete for kinetic evaluation. The pharmacokinetics of the metabolite, cilazaprilat, after a single dose of 0.5 mg cilazapril were similar to previous observations in healthy volunteers at identical dosage. Repeat administration, however, led to greater accumulation than previously observed in volunteers at the higher dosages of 1.25 or 5 mg given for 8 days. Seven patients experienced adverse events. Four were severe, leading to withdrawal of the patients from the study, but only one event was related to cilazapril. Of the other three, one suffered a myocardial infarction and subsequently died due to worsening congestive heart failure. One other patient was withdrawn with two adverse events probably related to cilazapril. No other deaths occurred amongst the study population, and there were no significant abnormalities in haematology or blood chemistry.
We examined retrospectively the usefulness of routine clinic visits in preventing adverse cardiac events in 115 patients awaiting coronary surgery or angioplasty. Mean waiting time from angiography to revascularization was 126 days. A total of 126 visits were made by 80 patients. No deaths occurred, but one patient, despite three visits, suffered myocardial infarction at 316 days post-angiography. Eight patients required admission for unstable angina, five having been on the waiting list for less than 5 weeks. The mean number of clinic visits, number of diseased vessels and proportion on triple anti-ischaemic therapy were similar in the patients suffering such events and those remaining stable. In conclusion, the inherent unpredictability of coronary disease greatly limits the role of interim clinic visits in the prevention of adverse cardiac events in patients awaiting revascularization.
We conducted a retrospective study to correlate thrombotic variables with the risk from an acute coronary event, using a new in vitro technique, which measures haemostasis, thrombolysis and coagulation from non-anticoagulated blood samples. The analysis was based on data from 63 patients who had undergone exercise radionuclide ventriculography, 50 of whom were considered to be at risk from an acute coronary event because they satisfied at least one of the following three criteria: (1) coronary angiography documented disease, (2) prior myocardial infarction, (3) ventriculography assessed provocable ischaemia. Fifty matched normal subjects were used as controls. Significantly enhanced haemostasis was measured in patients considered at risk from acute coronary event, and haemostatic activity was further increased in patients with provocable ischaemia. Haemostasis in eight patients at risk (provocable ischaemia), who continued with the medication during the test, did not differ significantly from the controls. Greatly reduced spontaneous thrombolytic activity was measured in all patients at risk from acute coronary events. These findings suggest the presence of hyperactive platelets in patients at risk from acute coronary events, with an additional risk of greatly reduced spontaneous thrombolytic activity.
It is very important to pay attention to technical detail when acquiring nuclear scans of the heart. It must be remembered that not only is the heart a three dimensional structure, which imposes its own limitations on the interpretation of information represented as two dimensional images, but the organ also moves which will in turn degrade static images. Dynamic studies of left ventricular function must be able to resolve the rapidly changing events of the cardiac cycle which makes specific technical demands upon the imaging equipment and computer system used. In spite of these potential drawbacks, both static and dynamic imaging of the heart using radiopharmaceuticals are widely used in a clinical and research environment. In this article some of the technical considerations will be covered as they apply to both the commonly used clinical applications of nuclear cardiology and some of the newer but potentially exciting techniques will also be covered briefly.