Christof Alexander

Influence of right ventricular stimulation site on left ventricular function in atrial synchronous ventricular pacing

OBJECTIVES The study investigates the correlation between left ventricular function and QRS duration obtained by alternate right ventricular pacing sites. BACKGROUND 1. Right ventricular apical pacing is associated with alterations of left ventricular contraction sequence. 2. A stimulation producing narrow QRS complexes is supposed to provide for better left ventricular contraction patterns. METHODS Fourteen patients with third degree AV block received one ventricular pacing lead in apical position. The alternate lead was attached to that site on the septum that produced the smallest QRS complex as measured from the earliest to the last deflection in any of the orthogonal Frank leads (xyz). During atrial synchronous ventricular pacing, the AV delay was optimized individually and for each stimulation site using mitral valve doppler or impedance cardiography. By radionuclide ventriculography, the phase distribution histogram of left ventricular contraction was evaluated as area under the curve (AuC); systolic function was determined as ejection fraction (EF) and as absolute ejected counts (EC) in random order. The difference (delta) in QRS duration between apical and septal stimulation (deltaxyz) was correlated with the difference in phase distribution (deltaAuC) and ejection parameters (deltaEF, deltaEC). RESULTS QRS duration was shorter with septal than with apical pacing in 9 out of 14 patients (64%); it was longer in 4 (29%), and no difference was seen in 1 patient. There was a significant positive correlation between the change in QRS duration (deltaxvz) and phase distribution (deltaAuC: r = 0.66393, p = 0.010) and a significant negative correlation to systolic function (deltaEF: r = 0.70931, p = 0.004; deltaEC: r = 0.74368, p = 0.002). CONCLUSIONS In atrial synchronous right ventricular pacing, if the AV delay is adapted individually, decreased QRS duration obtained by alternate pacing sites is significantly correlated with homogenization of left ventricular contraction and with increased systolic function in acute tests.

Clinical Value of Iodine-123-Alpha-Methyl-l-Tyrosine Single-Photon Emission Tomography in the Differential Diagnosis of Recurrent Brain Tumor in Patients Pretreated for Glioma at Follow-Up

PURPOSE To assess the clinical potential of iodine-123-alpha-methyl-L-tyrosine (IMT) and single-photon emission tomography (SPET) in the differential diagnosis of recurrences in patients pretreated for gliomas at follow-up. PATIENTS AND METHODS Seventy-eight patients were examined after primary therapy over 36 months. Histopathologic diagnoses of all patients was known at first treatment; magnetic resonance and/or computed tomography examination was performed in addition to IMT-SPET. Cerebral SPET images were acquired 20 minutes after intravenous application of 190 +/- 10 MBq of IMT. SPET images were classified as positive or negative for recurrent tumor visually and by calculating the ratios between tracer accumulation in the lesion and the unaffected contralateral regions of reference using region of interest. Final diagnoses were based on prospective clinicopathologic findings obtained independently of IMT-SPET. RESULTS IMT-SPET detected all high-grade recurrent gliomas (grade 4; sensitivity, 100%). A difference could be demonstrated in grade 2 and 3 recurrences (sensitivity, 84% and 92%, respectively). Moreover, benign posttherapeutic lesions (postoperative scars, radiation necrosis) were correctly diagnosed as negative for tumor recurrence. In general, IMT uptake in grade 2 (1.45 +/- 0.24) was significantly lower than that in grades 3 (1.70 +/- 0.41) and 4 (1.88 +/- 0.32). However, it was difficult to evaluate tumor grade only from the IMT accumulation in individual cases. CONCLUSION IMT-SPET seems highly useful for detecting and delineating recurrent gliomas and differentiating between benign posttherapeutic lesions and malignant tumor tissue. It may be a valuable clinical tool to diagnose recurrences in patients pretreated for gliomas at follow-up. However, it showed limitations in determining histologic tumor grade.

Myocardial metabolic imaging by means of fluorine-18 deoxyglucose/technetium-99m sestamibi dual-isotope single-photon emission tomography

The detection of preserved glucose uptake in hypoperfused dysfunctional myocardium by fluorine-18 deoxyglucose (FDG) positron emission tomography (PET) represents the method of choice in myocardial viability diagnostics. As the technique is not available for the majority of patients due to cost and the limited capacity of the PET centres, it was the aim of the present work to develop and test FDG single-photon emission tomography (SPET) with the means of conventional nuclear medicine. The perfusion marker sestamibi (MIBI) was used together with the metabolic tracer FDG in dual-isotope acquisition. A conventional SPET camera was equipped with a 511-keV collimator and designed to operate with simultaneous four-channel acquisition. In this way, the scatter of 18F into the technetium-99m energy window could be taken into account by a novel method of scatter correction. Thirty patients with regional wall motion abnormalities at rest were investigated. The results of visual wall motion analysis by contrast cine-ventriculography in nine segments/heart were compared with the results of quantitative scintigraphy. The scintigraphic patterns of MIBI and FDG tracer accumulation were defined as normal, matched defects and perfusion-metabolism mismatches. Spatial resolution of the system was satisfactory, with a full width at half maximum (FWHM) of 15.2 mm for 18F and 14.0 mm for 99mTe, as measured by planar imaging in air at 5 cm distance from the collimator. Image quality allowed interpretation in all 30 patients. 88% of segments without relevant wall motion abnormalities presented normal scintigraphic results. Seventy-five akinetic segments showed mismatches in 27%, matched defects in 44% and normal perfusion in 29%. We conclude that FDG-MIBI dual-isotope SPET is technically feasible with the means of conventional nuclear medicine. Thus, the method is potentially available for widespread application in patient care and may represent an alternative to the 201T1 reinjection technique.

Radioimmunoscintigraphy of ovarian tumours with technetium-99m labelled monoclonal antibody-170: first clinical experiences.

The recently developed technetium-99m-labelled monoclonal antibody-170 (MAb-170) was designed for diagnostic use in patients suffering from gynaecological adenocarcinoma. Following in vitro studies which showed immunoreactivity of this antibody to more than 90% of human adenocarcinomas, the present investigation was initiated to verify its usefulness for radioimmunoscintigraphy of ovarian tumours. Most of the 30 patients participating in this study underwent immunoscintigraphy prior to first-look surgery. Biokinetic evaluation in two patients showed a plasma half-time of 18.9 h (mean value,n = 2,r = 0.98) and a biexponential total body curve with values of 7.7 h and 17 days (r = 0.98). The mean 24-h urinary excretion was 12% of the injected dose. Radioimmunoscintigraphy using the MAb-170 recognised 12 of 13 cases of adenocarcinoma of the ovaries, corresponding to an overall sensitivity of 92.3% . Specificity was 94.1% (16/17). The calculation of accuracy yielded a figure of 93.3% (28/30). Of 33 known lesions, 26 were visualised successfully; thus the locoregional sensitivity was 78.8%. Of 29 benign tumour sites, 28 showed no evidence of tracer accumulation, corresponding to a locoregional specificity of 96.6%. The smallest lesion visualised was an adenocarcinoma of the corpus uteri with a diameter of 1.5 cm. Technetium-99m labelled MAb-170 is a promising new radiopharmaceutical for immunoscintigraphy of ovarian adenocarcinoma.

Rapid measurement of blood leakage during regional chemotherapy

In order to avoid complications after regional chemotherapy (isolated hyperthermic perfusion) of the extremities, rapid measurement of blood leakage from the extracorporeal to the systemic circulation is important. A method using technetium-99m in vivo red blood cell (RBC) labelling is reported that provides results within 3 min. Blood samples drawn from the systemic and the extracorporeal circulation were measured for 99mTc activity using a mobile well counter, and the leakage values calculated. The mean result was 7.6%±6.5%/15 min (n=209). The corresponding flow rate was 100.2±85.7 ml/15 min (mean ± SD). The values for isolation perfusion of the upper and the lower extremities are compared. The leakage results using 99mTc RBC labelling were correlated with other blood pool markers. Iodine-125 human serum albumin and indium-113 m transferrin were administered in subgroups of 4 and 19 patients simultaneously. Using linear regression, the coefficient of correlation was 0.72 for 99mTc/113mIn and 0.58 for 99mTc/125I. Comparison with the alternatives suggests that the rapid method of leakage measurement after 99mTc RBC labelling can be considered one of the most practicable and reliable methods available.

Monoclonal antibody MAb-170 for immunoscintigraphic detection of ovarian tumors.

OBJECTIVE The technetium Tc 99m-labeled monoclonal antibody MAb-170 was designed for diagnostic use in patients with gynecologic adenocarcinoma. Our investigation was initiated to verify its usefulness for radioimmunoscintigraphy of ovarian tumors. STUDY DESIGN Most of the 82 patients participating in this study underwent immunoscintigraphy before first-look surgery. RESULTS Radioimmunoscintigraphy recognized 36 of 41 patients with adenocarcinoma of the ovaries, corresponding to an overall sensitivity of 88%. Specificity was 90% (38/42). The calculation of accuracy gave a result of 89% (74/83). Of 110 known lesions, 92 were visualized successfully; thus the local-regional sensitivity was 84%. Of 160 benign tumor sites, 154 showed no evidence of tracer accumulation, corresponding to a local-regional specificity of 96%. The smallest lesion visualized was an adenocarcinoma of the corpus uteri with a diameter of 1.5 cm. CONCLUSION The monoclonal antibody MAb-170 is a promising radiopharmaceutical for immunoscintigraphy of ovarian adenocarcinoma.

Localization of extramedullary hematopoiesis with Tc-99m-labeled monoclonal antibodies (BW 250/ 183)

Extramedullary hematopoiesis is of special interest to physicians because of its relation to hematologic disease. Because it normally remains asymptomatic, sites are typically found by chance. Effective diagnosis involves a specific, reliable, whole-body and low-cost method of screening. Although radiologic methods such as computed tomography and magnetic resonance imaging can only suggest the presence of extramedullary hematopoiesis, apart from invasive and therefore risky biopsy procedures, only scintigraphy can detect and confirm the nature of hematopoietic tissue. Although radioactive tracers commonly in use partly lack the demands for specific diagnosis, Tc-99m–labeled antibodies (NCA-95) seem to combine the advantages of different scintigraphic approaches. Two patients with dyserythropoetic anemia and paravertebrally situated pelvic and thoracic tumor masses were studied for extramedullary hematopoiesis. Planar and SPECT images were obtained 6 and 24 hours after injection of 800 to 850 MBq (22 to 23 mCi) Tc-99m–labeled monoclonal antibodies (BW 250/183). In both patients, tracer accumulated in the masses, thereby revealing hematopoietic tissue. Biopsy confirmed these findings. By using Tc-99m–labeled monoclonal antibodies to detect extramedullary hematopoiesis, the demands of diagnosis were met. As an alternative to invasive diagnostic procedures, this tracer combines the advantages of other radioactive substances previously used, such as radioiron, In-111 chloride, and Tc-99m colloids. This low-cost agent is readily available and when applied, reliable, and delivers whole-body images free of additional uptake in the liver or spleen.

Radioimmunoscintigraphy of Ovarian Tumours with Tc-99m Labelled Monoclonal Antibody-170

The present publication reflects our first experiences using the Tc-99m labelled monoclonal antibody MAb-170 for diagnostic use in patients with ovarian tumours. The collective included 10 patients suspected to have ovarian carcinoma. The results showed a sensitivity of 100 percent, the specificity was 100 % for adenocarcinoma and 71 % for ovarian carcinoma. In conclusion Tc-99m MAb-170 is a promising radiopharmaceutical for the detection of ovarian carcinoma.

Long-Term Side Effects after High Dose Radioiodine Therapy in Thyroid Carcinoma Patients

The investigation is an evaluation of intermediate and long-term side effects in patients after high-dose radioiodine treatment due to differentiated thyroid carcinoma. The results demonstrate that severe long-term non-stochastic side effects are rare after high-dose radioiodine treatment of differentiated thyroid carcinoma. Moderate side effects are more common than mentioned in literature. Mostly they are the result of radiation damage to the salivary glands.

Influence of Right Ventricular Stimulation Site on Left Ventricular Function in Atrial Synchronous Pacing

In 14 patients with 3rd degree AV block, one pacing lead was implanted in the right ventricular apex, the septal electrode was attached to that site exhibiting the smallest QRS complex. During atrial synchronous ventricular pacing, AV delay was optimized individually for each stimulation site. Phase distribution of left ventricular contraction and systolic function were randomly determined for each pacing site by radionuclide ventriculography. Decreased QRS duration was correlated with less dyssynergy of contraction and with an increase in systolic function. In atrial syncronous pacing, this can be obtained if the pacing site is optimized by surface ECG guidance and the AV delay is adapted individually.