Jens Marving

Accuracy of absolute left ventricular volumes and cardiac output determined by radionuclide cardiography.

We determined left ventricular (LV) volumes and derived variables by gated equilibrium radionuclide imaging at rest and during exercise in 12 patients without valve disease or intracardiac shunts. LV volume was determined as the product of the background-corrected LV count rate and an individual attenuation correction factor divided by the count rate in peripheral blood. Attenuation correction was based on measurement of LV depth within the chest from an initial first pass study in the left lateral view and a linear attenuation coefficient of 0.156 cm-1 determined in phantom studies. The average LV depth was 8.0 cm (range 6.9-9.1) in agreement with an average depth measured by echocardiography of 8.2 cm (6.3-9.4), P much greater than 0.05. The correlation between radionuclide (RC) and simultaneous thermodilution (TD) measurements was for cardiac output (CO): r = 0.95; CO (RC) = 1.00 X CO (TD) + 0.10 1/min with a standard error of the estimate (SEE) of 0.79 1/min; for stroke volume (SV): r = 0.90; SV(RC) = 0.93 X SV (TD) + 5 ml; SEE = 8 ml; for end-diastolic volume (EDV): r = 0.96; EDV(RC) = 1.06 X EDV(TD) -14 ml; SEE = 27 ml; and for end-systolic volume (ESV): r = 0.98; ESV(RC) = 1.05 X ESV (TD) -6 ml; SEE = 20 ml. The interobserver variation, expressed as the coefficient of variation, was for cardiac output 6%, for stroke volume 6%, for end-diastolic volume 4%, and for end-systolic volume 5%. This method permits non-invasive determination of LV volume and total LV output per beat based exclusively on data obtained during radionuclide imaging.

The reliability of measuring left ventricular ejection fraction by radionuclide cardiography: evaluation by the method of variance components.

A statistical model based on the method of variance components was applied to obtain confidence statements for single and repeat determinations of left ventricular ejection fraction by radionuclide techniques. With this approach variance caused by individual factors in the measurement procedure is estimated to allow calculation of confidence intervals based on single measurements and the detection limits for changes. Six study groups made up of a total of 143 subjects were examined by both multigated equilibrium and first pass imaging. Under favourable conditions (with an updated gamma camera and experienced observer) the 95% confidence interval with a single measurement of left ventricular ejection fraction by equilibrium imaging was +/- 3 ejection fraction units, compared with +/- 6 units with the first pass technique (one ejection fraction unit = 1/100 of the possible values from 0.00 to 1.00). The minimal significant changes (at the 5% level) in measured equilibrium left ventricular ejection fraction at intervals of 15 min, 3 days, 1, 3, and 4 weeks were +/- 4, +/- 4, +/- 5, +/- 5, and +/- 6 units, respectively. The corresponding minimal detectable changes in a subjects true left ventricular ejection fraction for the same intervals were +/- 7, +/- 7, +/- 10, +/- 10, and +/- 12 units respectively. With first pass imaging, only average values for the variation at repeat determination could be calculated. The minimal significant change in measured first pass left ventricular ejection fraction was +/- 7 units, and the minimal detectable change in true left ventricular ejection fraction was +/- 14 units. Measurements of left ventricular ejection fraction by equilibrium technique were generally more reproducible than first pass determinations because the variability caused by study acquisition, observer analysis, and residual errors was smaller. The method of variance components appears to be well suited to the evaluation of quantitative biological measurements in clinical use. The popularity of established procedures may obscure the lack of basic information about method evaluation.

Left Ventricular Performance Monitored by Radionuclide Cardiography during Induction of Anesthesia

Radionuclide cardiography with 99mTc-labeled erythrocytes was carried out in three different studies comprising 20 female patients without heart or lung diseases. Left ventricular ejection fraction (LVEF) and other hemodynamic variables were measured immediately before and during induction of anesthesia (thiopental, N2O/O2, succinylcholine, laryngoscopy + oral intubation, halothane). In study 1, serial measurements of LVEF, left ventricular volume, and derived variables were obtained by gamma camera in seven patients using 3-min sampling periods. In Studies 2 and 3, LVEF was monitored serially in seven and six patients, respectively, by a portable, nonimaging probe (nuclear stethoscope) at 1-min intervals or less. The induction period was prolonged to last 24 min in studies 1 and 2, against 9 min in study 3.In studies 1 and 2 there was an increase in blood pressure and heart rate after thiopental and after laryngoscopy and intubation. In study 3 a similar increase was observed after intubation. In the gamma camera study LVEF decreased from 0.72 to 0.53 after thiopental, with no further decrease during intubation. This decrease was accompanied by an increase in end-systolic volume and a decrease in the ratio: systolic cuff pressure/end systolic volume, whereas end-diastolic volume and cardiac index remained unchanged. In the nuclear stethoscope studies, LVEF decreased both after thiopental and after intubation, in study 2 from 0.68 to 0.38 and from 0.53 to 0.41, respectively; in study 3 from 0.69 to 0.53 and from 0.57 to 0.44, respectively.Our observation, in healthy, female individuals, provide an impetus for further noninvasive radionuclide studies during anesthesia in patients with cardiovascular disease.

Left ventricular ejection fraction during anaesthetic induction: comparison of rapid-sequence and elective induction.

A randomized clinical trial was conducted in 14 women, aged 24–60 years, to compare the effects of rapid-sequence induction of anaesthesia and elective induction on heart rate, blood pressure and left ventricular ejection fraction (LVEF). None of the patients sufferedfrom heart or lung diseases, and all were scheduled for hysterectomy. Cuff blood pressure was measured repeatedly by an automatic recording device, and heart rate and LVEF were monitored by a portable nonimaging nuclear probe. In seven patients, a rapid-sequence induction was performed following preoxygenation and with simultaneous injection of thiopentone (5mg.kg1) and succinylcholine, without starting manual ventilation until the airway was secured with the endotracheal tube. In another seven patients, elective induction was carried out by sequential administration of the same drugs.Forty seconds after laryngoscopy and intubation mean blood pressure had increased by 38 per cent and heart rate by 29 per cent from preintubalion values in the rapid-sequence induction group, compared to 30 and 12 per cent respectively, in the elective induction group (p < 0.05). Similar decreases in LVEF was observed in both groups, from 0.60 to 0.42 in the elective induction group, and from 0.60 to 0.41 in the rapid-sequence induction group. The equal depression of LVEF indicates that laryngoscopy and intubation produce, with both induction regimens, sudden impairment of cardiac function. The more pronounced hypertension and tachycardia observed during rapid-sequence induction suggests a higher myocardial oxygen consumption which may represent a serious additional burden for the poorly perfused heart.RésuméUne étude clinique randomisée a été faite chez 14 femmes âgées de 24 à 60 ans afin de comparer les effets de la séquence rapide d’induction de l’anesthésie et de l’induction élective sur la fréquence cardiaque, la pression artérielle, et la fraction d’éjection du ventricule gauche (LVEF). Aucune des patientes souffraient de maladie cardiaque ou pulmonaire et toutes étaient cédulées pour hystérectomie. La mesure de la tension artérielle par brassard était répétée par un appareil automatique et la fréquence cardiaque et le LVEF étaient surveillés par un probe portatif nucléaire non imagé. Chez sept patientes, une séquence rapide d’induction était faite après préoxygénation et injections simultanées de thiopentone (5 mg.kg-1) et succinylcholine sans ventilation manuelle jusqu’à l’intubation. Chez sept autres patientes, l’induction élective était faite par l’administration séquentielle des mêmes médicaments. Quarante secondes après laryngoscopie et intubation la pression artérielle moyenne augmenta de 38 pour cent et la fréquence cardiaque de 29 pour cent des valeurs préintubation pour le groupe à séquence d’induction rapide, comparativement à 30 et 12 pour cent respectivement pour le groupe à induction élective (p < 0.05). Une diminution similaire du LVEF a été observée dans les deux groupes de 0.60 à 0.42 pour le groupe à induction élective et de 0.60 à 0.41 pour le groupe à induction rapide.La dépression indentique dans les deux groupes du LVEF nous indique que la laryngoscopie et l’intubation produisent une détérioration soudaine de la fonction cardiaque avec les deux méthodes d’induction. L’hypertension plus prononcée et la tachycardie observée lors de la séquence rapide d’induction suggère une plus grande consommation d’oxygène qui pourra représenter une surcharge additionnelle sérieuse pour le cœur mat perfusé.

Reproducibility of determination of right ventricular ejection fraction by radionuclide imaging: assessment by the statistical method of variance components.

SummaryConfidence limits for single and repeat measurements of right ventricular ejection fraction (RVEF) were established by means of a model based on the statistical method of variance components. A total of 80 subjects (age 23 to 74 years) were examined by two radionuclide methods 1) gated first-pass (fp) technique performed in a standard 30° right anterior oblique projection, and 2) multigated equilibrium imaging (muga) in an individual left anterior oblique view, applying with both methods separate end-diastolic and endsystolic ventricular regions of interest.Values obtained by fp technique were clearly higher than those measured by the muga approach, and the correlation between them was only fair: RVEFmuga = 0.48 RVEFfp + 0.13; r = 0.73; SEE = 0.08. The 95% confidence limits for a single measurement were with the fp technique: ‘true’ RVEF = measured RVEF ±6 EF-units compared to ±16 units with the muga method. At repeat determination within an interval of four weeks, the minimal changes in measured RVEF that were statistically significant at the 5% level were with the fp technique ±8 units with the same observer on both occasions and ±9 units with different observers. Corresponding figures with the muga method were ±16 and ±22 units, respectively. The minimal changes in a subjects ‘true’ RVEF necessary to produce a significant change in measured RVEF were with fp technique ±14 units for the same observer and ±17 units for different observers, compared to ±30 and ±41 units with the muga method.In conclusion, the variability with the muga approach was far greater than with the fp technique and the consequent reproducibility so poor as to preclude meaningful measurement of RVEF by the muga method.

Scintigraphy of kidneys located at different depths: the geometric mean method for determination of differential renal function: case report

In patients with kidneys located at different depths, differential renal function cannot simply be determined with Tc-99m DMSA scintigraphy using the accumulated count rates from each kidney in the anteroposterior or posteroanterior projection. This will give grossly misleading results. In patients with abnormally located kidneys, scintigrams in both the anteroposterior and posteroanterior views may be obtained so that the geometrical mean method can be applied. An example of the use of this method is given.

Underestimation of equilibrium radionuclide left ventricular ejection fraction due to myocardial uptake of 99mTc

First pass and gated equilibrium radionuclide imaging (in vitro labelling) was performed on three occasions (on day 1, 1 week and 4 weeks later) in a patient, who had suffered from myocardial infarction 6 months previously. At the 1 week assessment four successive equilibrium blood pool scans were performed within an hour. The patient was in a stable clinical condition, and the following values for right (RVEF) and left ventricular ejection fraction (LVEF) were obtained from first pass studies performed on the three occasions, RVEF: 0.66, 0.64 and 0.68; LVEF: 0.30, 0.29 and 0.30, respectively. Corresponding values for global LVEF determined by equilibrium imaging were: day 1 0.24, 1 week 0.16, 0,15, 0.13 and 0.14, 4 weeks 0.26. Underestimation of the LVEF by the gated equilibrium method at the 1-week assessment was probably due to myocardial uptake of non-RBC bound 99mTc in an apical aneurysm as later confirmed by a positive myocardial scan with 99mTc-stannous pyrophosphate.