Agreement between methods of measurement with multiple observations per individual.

Limits of agreement provide a straightforward and intuitive approach to agreement between different methods for measuring the same quantity. When pairs of observations using the two methods are independent, i.e., on different subjects, the calculations are very simple and straightforward. Some authors collect repeated data, either as repeated pairs of measurements on the same subject, whose true value of the measured quantity may be changing, or more than one measurement by one or both methods of an unchanging underlying quantity. In this paper we describe methods for analysing such clustered observations, both when the underlying quantity is assumed to be changing and when it is not.

Intra- and interhospital repeatability of radionuclide left ventricular ejection fraction in post-infarction patients.

OBJECTIVE: To evaluate intra- and interobserver and interhospital repeatability of radionuclide left ventricular ejection fraction in post-infarction patients. DESIGN: The study comprised 131 patients who were examined in three different hospitals 2-7 days post infarction. The radionuclide examinations were conducted in a standardized manner, and different observers carried out repeated measurements blind on the stored raw data. RESULTS: The coefficients of variation were between 1.5% and 6.2%, and limits of agreement between +/- 0.012 and 0.056. There were no significant differences between the intra- and interobserver or interhospital repeatability in average, but some significant differences between individual observers were noted. CONCLUSION: The repeatability of LVEF was acceptable, with limits of agreement in the range +/- 0.012-0.056. Some differences between observers and hence hospitals were noted, which may be of clinical relevance.

The value and correlates of left ventricular cavity assessment in dipyridamole 201Tl SPET studies.

Left ventricular cavity (LVC) enlargement during SPET dipyridamole 201Tl myocardial perfusion imaging studies is a proven marker of severity of coronary artery disease. Nevertheless, the influence of the extent of myocardial infarct and ischaemia on the degree of LVC enlargement both at rest and with dipyridamole has not been clearly analysed. One hundred and one patients were studied by both dipyridamole myocardial perfusion imaging and radionuclide ventriculography within 1 week. The left ventricular ejection fraction (LVEF) was 57 +/- 9 in normal resting LVC patients (group I), 43 +/- 8 in mild LVC enlargement patients (group II) and 28 +/- 5 in moderate-to-severe LVC enlargement patients (group III). The number of fixed defects was increased in patients in group II and group III, but there was no significant differences in the number of ischaemic segments among groups. The number of ischaemic segments was much higher in patients with transient cavity dilatation than those without cavity change; nonetheless, both LVEF and the numbers of fixed segments were unchanged. The degree of LVC enlargement at rest strongly reflects the resting left ventricular systolic function as well as the extent of previous myocardial infarct. On the other hand, transient cavity dilatation during dipyridamole infusion can only reflect the extent of viable myocardium at risk.

Nuclear cardiology in the UK 1994: activity relative to Europe, USA, and British Cardiac Society targets.

OBJECTIVE: To survey practice in nuclear cardiology in the UK in 1994. DESIGN: A questionnaire was sent to 219 centres performing nuclear imaging asking for details of current practice in nuclear cardiology. Replies were received from 192 centres (88%). MAIN OUTCOME MEASURES: Activity in performance of myocardial perfusion imaging (MPI) and radionuclide ventriculography (RNV), anticipated changes in activity, differences between regional and district hospitals, technical imaging parameters, and referral sources. RESULTS: Of the responding centres, 125 (65%) performed nuclear cardiology procedures. More regional than district hospitals performed nuclear cardiology procedures (85% v 55%, p < 0.0003) and regional centres performed a higher proportion (62% v 24%, p < 0.001) of nuclear cardiology activity. Nuclear cardiology activity was 0.82 scans per 1000 population per year (MPI 0.56, RNV 0.26). There has been a significant increase (24%) in nuclear cardiology since 1988. There has been a pronounced rise in MPI (350%) while RNV has fallen by 47%. Myocardial perfusion activity in the UK remains very low (25% and 5% in regional and district hospitals, respectively) compared with the 1994 figures of 2.2/1000/year for Europe or 10.8/1000/year for the USA. CONCLUSIONS: MPI has increased on average by 23%/annum (compound rate) since 1988, but in 1994 was still only 32% of the British Cardiac Society target of 2.6/1000/year. Proper resources for capital expenditure on new equipment and new staff will be important to maintain momentum in closing the gap. Also important is improved clinical understanding, as already implemented by including nuclear cardiology in guidelines for specialist cardiology training.

Changes in left and right ventricular performance and volumes in seven-year survivors of acute myocardial infarction.

We describe the spontaneous long-term changes in right (RV) and left (LV) ventricular performance during a 7-year period after acute myocardial infarction (AMI). Radionuclide ventriculography was performed in the second week after AMI in 201 patients. RV and LV ejection fractions, and LV end-diastolic and end-systolic volumes were determined. A follow-up after 7 years was performed in 55 survivors. Of these, 16 patients were also examined after 1 year. During the 7-year follow-up period, LV ejection fraction decreased from 0.49 to 0.45 (p < 0.01). LV end-diastolic volume increased from 161 to 210 ml (30%) (p < 0.01), and LV end-systolic volume from 83 to 123 ml (48%) (p < 0.01). In patients without recurrent AMI, coronary artery bypass grafting surgery, or angiotensin-converting enzyme inhibitor therapy (n = 37) during follow-up, no change in average LV ejection fraction was observed. Nevertheless, this subgroup had substantial increases in LV end-diastolic volume, from 157 to 190 ml (21%) (p = 0.002) and in LV end-systolic volume, from 80 to 105 ml (31%) (p < 0.001). In a subgroup of patients also reinvestigated after 1 year (n = 16), there was a 15% increase in LV end-diastolic volume the first year after AMI with an additional 10% increase in LV end-diastolic volume between years 1 and 7. Corresponding figures for LV end-systolic volume were 20% and 12%, respectively. Hardly any association was apparent between LV ejection fraction, LV end-diastolic volume, and LV stroke volume at discharge for subsequent LV dilatation.(ABSTRACT TRUNCATED AT 250 WORDS)

[Biventricular functional adaptation during a prolonged race. An analysis of global and regional ventricular function]. / Adaptación funcional biventricular durante una carrera de larga duración. Análisis de la función ventricular global y regional.

To determine the effects of a six-hour competitive race on left and right ventricular performance, 99mTc gated blood pool scans were performed to 6 long distance runners before the race (rest), each hour during the race and one hour after concluding the exercise (recovery). Heart rate increased during the race, peaking at 4th hour of competition (55 +/- 3 to 110 +/- 9 lpm; p = 0.001). Evolution of right ventricular ejection fraction showed a similar behavior with the evolution of left ventricular ejection fraction during the competition (r = 0.39; p = 0.006). Blood volume in the lungs increased at the end of the race (index 1.13 +/- 0.14) normalizing at recovery (index 1.03 +/- 0.03). Left and right ventricular peak filling rate had an inverse correlation with pulmonary blood volume (r = -0.31; p = 0.041 and r = -0.47; p = 0.001 respectively). Both left and right ventricular ejection fraction had an inverse correlation with pulmonary blood volume (r = -0.38; p = 0.006 and r = -0.34; p = 0.01 respectively). The anteroseptal regional ejection fraction showed an inverse correlation with end-systolic and end-diastolic volume (r = -0.32; p = 0.03 and r = -0.4; p less than 0.01 respectively). The posterolateral region showed a parallel evolution with the global ejection fraction for both left and right ventricles (r = 0.57; p less than 0.0001 and r = 0.38; p = 0.009 respectively). In conclusion, a transient biventricular functional adaptation during a prolonged race is related to pulmonary blood volume redistribution and to a higher preload for both ventricles and a greater afterload for the right ventricle. The posterolateral and inferoapical regions show a similar behavior as both left and right ventricular ejection fraction, response that does not occur with the anteroseptal regional ejection fraction.

Diagnostic testing in acute myocardial infarction: does patient age influence utilization patterns? The Worcester Heart Attack Study.

To assess the impact of patient age on the use of diagnostic testing in the management of acute myocardial infarction, the authors reviewed the hospital charts of 4,109 patients hospitalized for validated acute myocardial infarction in the Worcester, Massachusetts, metropolitan area during selected years between 1975 and 1986. Older patients were more likely to be female and to have a prior history of angina, hypertension, and diabetes mellitus (p less than 0.001). Acute myocardial infarctions among older patients were more likely to be recurrent, anterior in location, non-Q wave, smaller as reflected by peak creatine kinase levels, and complicated by congestive heart failure, cardiogenic shock, and atrial fibrillation (p less than 0.001). In-hospital mortality was directly related to increasing patient age (p less than 0.001). Patterns of utilization of the following diagnostic tests were examined: Holter monitoring, radionuclide ventriculography, echocardiography, exercise testing, pulmonary artery catheterization, and coronary arteriography. After adjustment for differences in demographic and clinical characteristics and in-hospital mortality, patients aged 65 years and older were significantly less likely to undergo exercise testing than were patients less than age 55. Patients older than age 75 were significantly less likely to undergo radionuclide ventriculography, pulmonary artery catheterization, and coronary arteriography than were younger patients. Sex-specific analyses did not produce results substantially different from those for the overall study population. The results of this community-wide study suggest that among patients hospitalized for acute myocardial infarction, chronologic age may be an independent determinant of utilization patterns of diagnostic testing. These findings suggest the need for a prospective evaluation of this issue, with an additional emphasis placed on the contributions of functional status and noncardiovascular illness to decision-making in the clinical management of acute myocardial infarction patients.

The nature of the background in radionuclide ventriculography: deductions from the mathematical behaviour of the ejection fraction.

The relationship between the ejection fractions calculated from 'uncorrected' radionuclide time activity curves (UEF) and angiographic ejection fractions (AEF) in 200 catheterized patients yielded the regression equation AEF = 1.74 UEF + 0.21. It follows from this linear relationship that the left ventricular ejection fraction can be estimated by linear regression without explicit background correction: RREF = 1.74 UEF + 0.21, where RREF is the radionuclide regression ejection fraction. We first investigated the possibility that changes in photon self-attenuation within the cardiac chambers cause the observed mathematical characteristics of the cardiac background, B. Self-attenuation was calculated for cylindrical and spherical ventricular models. The results were insensitive to the particular geometry and would have only a small effect on the observed EF. Alternatively, the 'background' may result from extra-ventricular radiation scattering from the heart into the detector. If we assume that B should be proportional to the ventricular scattering volume, Bd = Kd EDC for diastole and Bs = Ks ESC for systole, the background corrected ejection fraction will be BCEF = K UEF + (1-K) where K = (1-Ks)/(1-Kd). This agrees with the form of the empirical regression equation.