Effects of oral propafenone on defibrillation and pacing thresholds in patients receiving implantable cardioverter-defibrillators. Propafenone Defibrillation Threshold Investigators.

OBJECTIVES: The effects of propafenone, a predominantly class IC antiarrhythmic drug, on defibrillation and pacing thresholds were evaluated in patients undergoing cardioverter-defibrillator implantation. BACKGROUND: Previous studies have shown that the class IC agents encainide and flecainide may increase the energy requirements for pacing and defibrillation. Animal studies with propafenone have shown inconsistent results regarding its effect on defibrillation energy requirements. This report investigated the effects of propafenone on defibrillation and pacing thresholds in humans. METHODS: After cardioverter-defibrillator implantation, 47 patients were enrolled in a double-blind, three-way parallel, randomized trial of 450 mg/day (Group 1) or 675 mg/day (Group 2) of oral propafenone or placebo (Group 3) for 3 to 7 days. Predischarge defibrillation and pacing thresholds after treatment were compared with baseline thresholds obtained at implantation. RESULTS: There was no statistically significant difference between implantation and predischarge defibrillation thresholds in the three groups (Group 1: [mean +/- SE] 11.0 +/- 1.3 vs. 12.1 +/- 1.5 J; Group 2: 11.5 +/- 1.1 vs. 13.6 +/- 1.3 J; Group 3: 12.5 +/- 1.2 vs. 13.3 +/- 1.6 J), and no significant difference between treatment groups was found with a 0.86 power to detect a 5-J difference between groups. Paired pulse width pacing thresholds at 2.8 V were compared in 14 patients. A small increase of 0.02 ms was noted at predischarge testing in patients treated with propafenone and placebo. CONCLUSIONS: Short-term oral propafenone (450 and 675 mg/day) does not significantly affect defibrillation or pacing thresholds. Concomitant use of propafenone in patients with implantable cardioverter-defibrillators with recurrent ventricular or atrial tachyarrhythmias should not interfere with proper device function.

Cost-effectiveness of radiofrequency ablation compared with other strategies in Wolff-Parkinson-White syndrome.

BACKGROUND: Patients with Wolff-Parkinson-White syndrome fall into four risk groups: those with (1) prior cardiac arrest, (2) paroxysmal supraventricular tachycardia or atrial fibrillation (PSVT/AF) with hemodynamic compromise, (3) PSVT/AF without hemodynamic compromise, and (4) no symptoms. METHODS AND RESULTS: For each group, we developed a cost-effectiveness analysis examining five clinical management strategies: (1) observation, (2) observation until a cardiac arrest dictates the need for therapy, (3) initial drug therapy guided by noninvasive monitoring, (4) initial radiofrequency ablation (RFA), and (5) initial surgical ablation. We used a Markov simulation model to estimate life expectancy and costs for patients whose ages are between 20 and 60 years. The model includes the risks of cardiac arrest, PSVT/AF, drug side effects, procedure-related complications and mortality, the efficacy of drugs and RFA, and costs. Based on literature and expert opinion, we assumed that the annual risks of cardiac arrest are 0.01%, 0.05%, and 0.5%, respectively, in patients who are asymptomatic, who had PSVT/AF without hemodynamic compromise, or who had PSVT/AF with hemodynamic compromise. We also assumed that RFA has an overall efficacy of 92% in preventing cardiac arrest and arrhythmias. Our model predicts that RFA should yield a life expectancy greater than or equal to other strategies. In cardiac arrest survivors and patients who have had PSVT/AF with hemodynamic compromise, our model suggests that RFA should both prolong survival and save resources. For patients with PSVT/AF without hemodynamic compromise, the marginal cost-effectiveness of attempted RFA (followed by conservative treatment if the RFA fails) ranges from $6600 per quality-adjusted life year (QALY) gained for 20-year-old patients to $19,000 per QALY gained for 60-year-old patients. For asymptomatic patients, RFA costs from $174,000 per QALY gained for 20-year-old patients to $540,000 per QALY gained for 60-year-old patients. CONCLUSIONS: Our analysis supports the emerging practice of performing RFA in patients with Wolff-Parkinson-White syndrome who survive cardiac arrest or who experience PSVT/AF but also supports the current practice of observing asymptomatic patients.

Detection of abnormal parathyroid glands in postoperative patients with recurrent hyperparathyroidism: sensitivity of MR imaging.

OBJECTIVE: The efficacy of MR imaging in identifying abnormal parathyroid glands in patients with recurrent hyperparathyroidism after surgery was investigated. SUBJECTS AND METHODS: Findings on preoperative T1- and T2-weighted MR images in 44 patients with recurrent hyperparathyroidism were prospectively evaluated and compared with surgical/pathologic results in all patients. A blinded retrospective analysis of the MR findings comparing T1- or T2-weighted images alone and in combination for detection of abnormal parathyroid glands also was performed. RESULTS: Seventy-four percent of surgically proved abnormal parathyroid glands were detected prospectively and 65% were detected retrospectively on MR images. The combination of T1- and T2-weighted images increased the sensitivity for detection. The sensitivity for detection of abnormal glands was 72% in the neck and 86% in the mediastinum. The sensitivities for detecting parathyroid adenomas (80%) and hyperplastic glands (69%) were not significantly different. There was no threshold volume for detection of lesions with MR imaging. Both intrathyroid parathyroid adenomas were missed on MR images. Abnormal glands could not be differentiated from lymph nodes on MR images in three cases. CONCLUSION: MR imaging is a useful technique for detecting abnormal parathyroid glands preoperatively in patients with recurrent hyperparathyroidism after surgery. The combination of T1- and T2-weighted images increases the sensitivity for detection.

Teratomas versus cystic hemorrhagic adnexal lesions: differentiation with proton-selective fat-saturation MR imaging.

To assess the value of proton-selective fat-saturation magnetic resonance (MR) imaging in differentiating teratomas from cystic hemorrhagic masses, 38 patients with 48 lesions (21 teratomas, 27 cystic hemorrhagic masses) detected at prior ultrasound or computed tomography were imaged with standard T1- and T2-weighted spin-echo (SE) sequences. Twenty-one patients with 28 lesions (13 teratomas, 15 cystic hemorrhagic masses) were imaged with an additional T1-weighted fat-saturation sequence. On standard T1- and T2-weighted SE images, 43% of the teratomas and 52% of the cystic hemorrhagic masses were characterized correctly with signal intensity criteria. Sixty-two percent of the teratomas and 100% of the cystic hemorrhagic masses were characterized correctly with chemical shift artifact criteria. With fat-saturation images alone, the characterization sensitivity for teratomas and cystic hemorrhagic masses increased to 92% and 100%, respectively. Fat-saturation MR imaging was statistically superior to standard T1- and T2-weighted imaging in characterizing teratomas.

Ovarian lesions: detection and characterization with gadolinium-enhanced MR imaging at 1.5 T.

Magnetic resonance (MR) imaging for detection and characterization of ovarian masses was assessed in 33 patients with a total of 60 lesions. Lesions were characterized prospectively as benign or malignant by using T2-weighted MR images and unenhanced and gadolinium-enhanced T1-weighted MR images. MR imaging findings were compared with results of surgical laparotomy performed for staging of lesions. When malignancy was suspected, staging with MR imaging was performed. MR imaging demonstrated 57 of 60 (95%) surgically proved ovarian masses (34 of 36 were benign, 23 of 24 were malignant). Five significant primary criteria and four ancillary criteria for malignancy were established. For all MR pulse sequences combined, characterization of either type of lesion was correct in 84% of cases (48 of 57) when the five primary criteria were used and 95% (54 of 57) were correct when the four ancillary criteria were added. With gadolinium-enhanced images, correct characterization of malignant lesions increased from 56% to 78% with use of the five primary criteria and from 83% to 100% with use of both sets of criteria. Malignancies were correctly staged with MR imaging in 12 of 16 patients. Staging accuracy was 63% with unenhanced images and 75% with the addition of enhanced images.

Combined gadolinium-enhanced and fat-saturation MR imaging of renal masses.

Combined gadopentetate dimeglumine enhancement and fat-saturation (FS) spin-echo (SE) magnetic resonance (MR) imaging for the detection and characterization of renal masses was evaluated in 43 patients with a total of 71 lesions (28 solid masses and 43 cysts). SE MR sequences compared were the following: short repetition time (TR)/echo time (TE), conventional SE, short TR/TE FS SE, long TR/TE conventional SE, gadolinium-enhanced short TR/TE conventional SE, and gadolinium-enhanced short TR/TE FS SE techniques. MR findings were compared with findings of contrast-enhanced computed tomography (CT) and with pathologic findings in all patients. The sensitivities for detection of renal masses with gadolinium-enhanced FS (71 of 71 lesions) and with gadolinium-enhanced short TR/TE conventional (65 of 71 lesions) SE sequences were significantly (P less than .01) greater than with any unenhanced (short TR/TE conventional [40 of 71 lesions], or long TR/TE [39 of 71 lesions]) SE sequence. Lesion characterization was also best with the gadolinium-enhanced FS SE sequence (65 of 71 lesions correctly classified). When combined pre- and postcontrast short TR/TE FS SE images were analyzed with both qualitative (visual) and quantitative (region-of-interest measurements) assessment, lesion characterization improved even further (70 of 71 lesions were correctly characterized). All lesions detected with CT were visualized with the gadolinium-enhanced FS SE MR sequence, which in addition depicted seven cysts and two small renal cell carcinomas. In summary, the use of gadopentetate dimeglumine, especially when combined with the FS technique, was superior to unenhanced MR imaging for detection and characterization of renal lesions.

Repopulation of marrow after transplantation: MR imaging with pathologic correlation.

Sixty-seven magnetic resonance (MR) studies of the lumbar spine were performed in 15 patients with bone marrow transplants, and the appearance of marrow regeneration on MR images was correlated with results of bone marrow biopsy and pathologic examination. After transplantation, T1-weighted MR images of vertebral marrow showed a characteristic band pattern consisting of a peripheral zone of intermediate signal intensity and a central zone of bright signal intensity. Reciprocal changes were identified on short inversion time inversion recovery images. At histologic examination the central zone corresponded to fatty marrow; the peripheral zone corresponded to a zone of regenerating hematopoietic cells. Posttransplantation T1 and T2 relaxation times of the entire vertebral marrow were calculated from the spin-echo images; no statistically significant trends in relaxation times were noted. Knowledge of the normal MR pattern of marrow regeneration after transplantation may be useful in screening for residual marrow disease, determining marrow engraftment, and differentiating marrow repopulation with normal versus malignant cells.

Early and late bone-marrow changes after irradiation: MR evaluation.

Knowledge of the chronologic evolution of bone-marrow changes during and after radiation therapy is essential in differentiating normal postradiation changes from other marrow abnormalities. The appearance of the lumbar vertebral bone marrow was studied on 55 serial spin-echo and short-T1 inversion-recovery (STIR) MR images obtained in 14 patients receiving radiation therapy for Hodgkin disease, seminoma, or prostate carcinoma. Images were obtained before, at weekly intervals during, and at various monthly intervals up to 14 months after a 3- to 6-week course of fractionated paravertebral lymph-node irradiation of 1500-5000 rad (15-50 Gy). During the first 2 weeks of therapy, there was no definite change in the appearance of the marrow on spin-echo images; however, there was an increase in signal intensity on the STIR images, apparently reflecting early marrow edema and necrosis. Between weeks 3 and 6, the marrow showed an increasingly heterogenous signal and prominence of the signal from central marrow fat, shown best on T1-weighted images. Late marrow patterns (6 weeks to 14 months after therapy) varied and consisted of either homogenous fatty replacement or a band pattern of peripheral intermediate signal intensity, possibly representing hematopoietic marrow surrounding the central marrow fat. No focal marrow lesions or soft-tissue edema were identified during the course of radiation therapy; their presence should raise the possibility of the presence of a pathologic process other than radiation change. These data suggest that MR can detect radiation-induced marrow changes as early as 2 weeks after starting therapy, and that there are at least two distinct types of late marrow MR patterns.

Mesenteric cyst with atypical computed tomography appearance.

A case of mesenteric chylous cyst containing an unusual fluid-fluid level demonstrated on computed tomography but not on ultrasonography is presented.

Renal oxypurine deposition in Lesch-Nyhan syndrome: sonographic evaluation.

Lesch-Nyhan syndrome is a rare X-linked recessive disorder of purine metabolism associated with a virtually complete deficiency of the enzyme hypoxanthine-guanine phosphoribosyl-transferase (HPRT). The disease is characterized by hyperuricemia, self-multilation, choreoathetosis, spasticity, and mental retardation. The abnormalities of purine metabolism are present at birth and may lead to uric acid crystalluria and stone formation early in life. Radiographic findings described in Lesch-Nyhan syndrome include faintly radio-opaque stones on abdominal radiographs or, if renal disease is present, small kidneys with poor function on intravenous urogram. Radiolucent stones are usually composed of uric acid; however, several cases of xanthine and hypoxanthine-containing calculi in Lesch-Nyhan patients receiving allopurinl therapy have also been described. Oxypurine is the collective name for the compounds hypoxanthine, xanthine, and uric acid, and all may be radiolucent. We report a case of Lesch-Nyhan syndrome with presumed renal parenchymal oxypurine deposition demonstrated readily by ultrasonography but not detected on standard radiographs or intravenous urograms.

Differences in the migration of B and T lymphocytes: organ-selective localization in vivo and the role of lymphocyte-endothelial cell recognition.

The migration of B and T lymphocytes in the mouse has been studied by using 1) short-term in vivo homing studies, and 2) an in vitro assay of lymphocyte binding to specialized lymphoid organ venules (post-capillary, high endothelial venules (HEV)) in frozen sections of lymph nodes and Peyer's patches. The homing characteristics of B and T cell populations are largely independent of their organ of origin. B cells from any source distribute preferentially to Peyer's patches, whereas T cells home preferentially to peripheral lymph nodes. This organ specificity of migration appears to be determined at the site of lymphocyte exit from the blood by selective recognition of organ-specific determinants on the endothelial cells of HEV. In addition, the in vivo tendency of B cells to migrate preferentially to the spleen, and of T cells to localize better in lymph nodes is confirmed. The results indicate that, in a hypothetical situation in which an equal number of B and T lymphocytes localized in peripheral lymph nodes (or bound in vitro to peripheral node HEV), there would be about 2.5 B cells for every T cell in the mesenteric node, four to six B cells per T cell in Peyer's patches, and seven to nine B cells per T cell in the spleen. Comparison of these homing preferences with the distribution of B and T lymphocyte populations in situ suggests that selective lymphocyte migration may help determine the proportions of functionally distinct lymphocyte classes in particular lymphoid organs or sites of chronic inflammation, and thus may serve to influence the character of local immune responses.