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BACKGROUND: In patients with conventional pacemakers or ICD's, MRI is infrequently performed due to safety concerns. Recent reports have allayed many of these concerns. However, the additive clinical value of scanning patients with cardiac implants has not been established. OBJECTIVE: Assessing the additive value of thoracic and non-thoracic MRI in patients with implantable cardiac devices. METHODS AND RESULTS: Prospective data were analyzed in 500 patients with implanted cardiac devices that underwent MRI over a 12 year period at a single institution (Allegheny General Hospital, Pittsburgh, PA). A set of three questions were answered following scan interpretation by both the MRI technologist and interpreting MRI physician(s): 1) Did the primary diagnosis change? 2) Did MRI provide additional information to the existing diagnosis? 3) Did patient management change? If 'Yes' was answered to any of the above questions, it was considered that the MRI scan was of value to patient diagnosis and/or guiding therapy. Scans encountered were neurological/neurosurgical 354 (70.8%), cardiac 98 (19.6%) and orthopedic 48 (9.6%) in nature. In 431 (86%) MRI added additional information to the primary diagnosis and in 277 (55.4%) MRI changed the primary diagnosis. In 304 (60.8%) cases management changed, 265 (53%) due to a change in diagnosis and in 39 (7.8%) due to providing additional information. No safety issues were encountered and no adverse effects of MRI scan were noted. CONCLUSIONS: MRI in patients with implanted cardiac devices was of additive value to diagnosis and management thereby informing risk-benefit considerations. CONDENSED ABSTRACT: 500 patients with implanted cardiac devices who underwent a MRI examination over a 12 year period were followed prospectively. Imaging primarily focus on three anatomical regions (neurological/neurosurgical, cardiac and orthopedic) providing added information to the primary diagnosis in 431 (86%) cases and changing the primary diagnosis in 277 (55.4%) cases. In 304 (60.8%) cases management changed with 265 (53%) being due to a change of diagnosis and in 39 (7.8%) due to providing additional information. No safety issues were encountered using a defined protocol. CONCLUSIONS: MR imaging retains its diagnostic yield in patients with implanted devices.

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OBJECTIVES: The objective of this study was to assess the diagnostic usefulness of thoracic and nonthoracic magnetic resonance imaging (MRI) imaging in patients with implantable cardiac devices (permanent pacemaker or implantable cardioverter-defibrillators [ICDs]) to determine if there was a substantial benefit to patients with regard to diagnosis and/or management. BACKGROUND: MRI is infrequently performed on patients with conventional pacemakers or ICDs. Multiple studies have documented the safety of MRI scans in patients with implanted devices, yet the diagnostic value of this approach has not been established. METHODS: Evaluation data were acquired in 136 patients with implanted cardiac devices who underwent MRIs during a 10-year period at a single institution. Specific criteria were followed for all patients to objectively define if the diagnosis by MRI enhanced patient care; 4 questions were answered after scan interpretation by both MRI technologists and MRI physicians who performed the scan. 1) Did the primary diagnosis change? 2) Did the MRI provide additional information to the existing diagnosis? 3) Was the pre-MRI (tentative) diagnosis confirmed? 4) Did patient management change? If "Yes" was answered to any of the preceding questions, the MRI scan was considered to be of value to patient diagnosis and/or therapy. RESULTS: In 97% (n = 132) of patients, MR added value to patient diagnosis and management. In 49% (n = 67) of patients, MRI added additional valuable information to the primary diagnosis, and in 30% (n = 41) of patients, MRI changed the principle diagnosis and subsequent management of the patient. No safety issues were encountered, and no adverse effects of undergoing the MRI scan were noted in any patient. CONCLUSIONS: MRI in patients with implanted pacemakers and defibrillators added value to patient diagnosis and management, which justified the risk of the procedure.

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Previous investigations in normotensive animals have demonstrated a marked natriuretic and diuretic response following the acute administration of supraphysiologic doses of synthetic leptin. However, the importance of endogenous leptin in the regulation of renal sodium and water balance is not yet defined. This study examined the hemodynamic and renal excretory effects of circulating leptin blockade with a specific polyclonal antibody in groups of normotensive, chronically saline-loaded Sprague-Dawley rats. In the experimental group (n = 10), leptin antibody significantly decreased urinary sodium excretion and urinary flow by approximately 30% compared to the control rats (n = 10). Mean arterial pressure remained unchanged. Collectively, these results are interpreted to suggest that leptin is an important renal sodium-regulating factor under conditions of mild sodium and volume expansion.

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OBJECTIVE: Previous investigations have demonstrated that leptin promotes natriuresis with a renal tubular effect. However, the mechanisms involved in this response are unclear. The present study was designed to examine the hypothesis that the natriuretic response to leptin in normotensive Sprague-Dawley rats is regulated by nitric oxide (NO). RESEARCH METHODS AND PROCEDURES: The hemodynamic and renal excretory effects of intravenous bolus administration of pharmacological doses of synthetic murine leptin were examined in groups of control Sprague-Dawley rats (n = 8), Sprague-Dawley rats treated for 4 days with the NO synthase inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME) (n = 8), and Sprague-Dawley rats treated for 4 days with L-NAME followed by acute treatment with sodium nitroprusside (n = 8). RESULTS: In the control group (n = 8), an intravenous bolus of leptin, 400 microg/kg body weight, increased urinary sodium excretion 4- to 6-fold. In the Sprague-Dawley rats chronically administered l-NAME (n = 8), an intravenous bolus of 400 microg/kg of leptin did not increase sodium excretion. Acute sodium nitroprusside infusion to Sprague-Dawley rats chronically treated with L-NAME (n = 8) was associated with partial restoration of the sodium excretory response to leptin administration. DISCUSSION: Collectively, these results are interpreted to suggest that the natriuretic and diuretic responses to leptin observed in the Sprague-Dawley rat require a functional NO system.

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