Applications of nuclear magnetic resonance to surgical disease: a collective review.
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Animals↗
Biomedical subjects
G J Whitman
Publications and source records attributed to G J Whitman.
Early diagnosis of experimental necrotizing enterocolitis using proton nuclear magnetic resonance.
The purpose of this study was (1) to confirm an experimental model of aminophylline-induced necrotizing enterocolitis (NEC); and (2) to determine whether nuclear magnetic resonance (NMR) imaging, based upon proton relaxation values (T1, T2), could detect NEC during its early pathogenesis. Sixty male weanling Lewis rats (avg wt = 75 g) were randomly assigned to one of three experimental groups: (A) superior mesenteric artery (SMA) occlusion (1 min) + aminophylline treatment (40 mg/kg); (B) SMA occlusion; and (C) sham midline laparotomy (control). All surviving animals were sacrificed at 48 hr postoperation and a specimen of ileum was removed for light microscopy (LM), electron microscopy (EM), and NMR analysis. Percentage water content was determined for representative specimens. Mortality occurred only in experimental group A animals (18.2%; P less than 0.05), who had received aminophylline. Microscopy of ileum from sacrificed animals of this group showed changes ranging from mild cellular disruption to severe hemorrhagic necrosis. Early ultrastructural changes consistent with NEC were detectable with EM before LM. Proton relaxation results obtained with NMR showed significant prolongation of T1 (252.5 +/- 4.4 msecs; P less than 0.001) and T2 (69.3 +/- 1.4 msecs; P less than 0.025) during the first stages of NEC. NMR may indeed enable early, safe diagnostic imaging of NEC in infants receiving aminophylline, or those who are otherwise at increased risk for development of this disease.
Aminophylline↗
Nuclear magnetic resonance and cardiovascular surgery.
Nuclear magnetic resonance is opening new ground in the noninvasive diagnosis of anatomic and physiologic diseases. This article introduces the reader to nuclear magnetic resonance and its applications to cardiovascular surgery.
Animals↗
Diagnosis and therapeutic evaluation of a pediatric case of cardiomyopathy using phosphorus-31 nuclear magnetic resonance spectroscopy.
An 8 month old girl presented with undiagnosed non-anatomic congenital cardiomyopathy with massive cardiomegaly on chest X-ray film. Her older sibling had died suddenly at 6 months of age from what appeared to be a similar abnormality. Utilizing phosphorus-31 nuclear magnetic resonance (P-31 NMR) surface coil spectroscopy, a metabolic disorder was demonstrated in both her myocardium and skeletal muscle, revealing a phosphocreatine (PCr) to inorganic phosphate (Pi) ratio of half of that for a normal control infant. Manipulation of serum substrate availability indicated that medium chain triglycerides alone did not improve myocardial metabolism, but that intravenous glucose or oral carbohydrate loading raised the myocardial PCr/Pi ratio from 1.0 +/- 0.05 to 1.8 +/- 0.1 (p less than 0.01) without significantly affecting the PCr/Pi value of her resting skeletal muscle. This study demonstrates the feasibility of using P-31 nuclear magnetic resonance to evaluate the biochemistry of the human myocardium in vivo and to diagnose a metabolic abnormality. Phosphorus-31 nuclear magnetic resonance can thus be used to optimize therapy for human disease.
Cardiomegaly↗
Recovery of left ventricular function after graded cardiac ischemia as predicted by myocardial P-31 nuclear magnetic resonance.
The purpose of this study was to determine noninvasively some critical level of high-energy phosphate stores that relates to the recovery of ventricular contractile function after graded cardiac ischemia. Rabbit hearts (n = 30) were equipped with an intraventricular balloon to monitor developed pressure and +/- dp/dt and placed in a nuclear magnetic resonance magnet (Bruker, 4.7 Tesla). Each heart underwent 10, 20, 40, or 60 minutes of global ischemia followed by 1 hour of reperfusion. The pH as determined by nuclear magnetic resonance dropped from 7.14 +/- 0.04 to 7.07 +/- 0.07 (p less than 0.02) at 1 minute and to 6.19 +/- 0.08 at 30 minutes of ischemia; pH ceased to fall thereafter. Phosphocreatine was depleted to 10% +/- 7% of its preischemic control in 10 minutes. Adenosine triphosphate (ATP) concentrations were 71% +/- 14% and 1% +/- 2% at 10 and 60 minutes. Regression analysis of recovered developed pressure on end-ischemic ATP (EIATP) revealed: developed pressure = 0.93 (EIATP) + 23 (r2 = 0.99). We conclude that: anaerobic metabolism as evidenced by a fall in pH appears to be active for 30 minutes after normothermic ischemia and then ceases; phosphocreatine buffers the fall in ATP during early ischemia; there is a tight correlation between EIATP and recovery of left ventricular contractile function with a threshold content of approximately 80% below which recovery of function will not be complete.
Adenosine Triphosphate↗
A safe approach to left ventriculotomy.
Left ventriculotomy through an anatomically normal left ventricle is an increasingly frequent clinical necessity. In this regard, it is important to envision the epicardial projection of the papillary muscle in order to avoid injuring it. One should open the ventricle from the base (parallel to the left anterior descending or posterior descending coronary artery) and extend the incision apically while continuously palpating the papillary muscle.
Adult↗
Purification and properties of a phosphohydrolase from Enterobacter aerogenes.
A phosphohydrolase from Enterobacter aerogenes which hydrolyzes phosphate mono- and diesters has been purified approximately 50-fold to apparent homoeneity and crystallized. The enzyme is produced when the bacteria utilize phosphate diesters as sole phosphorus source. From sedimentation equilibrium experiments the molecular weight of the native enzyme is 173,000; from sodium dodecyl sulfate polyacrylamide gel electrophoresis the subunit molecular weight is 29,000, indicating that the enzyme is hexameric. The hydrolytic activity of the enzyme using both mono- and diesters is maximal at pH 5; THE Km of the enzyme for bis-p-nitrophenyl phosphate is constant from pH 5 to 8.5 whereas that for p-nitrophenyl phosphate increases about 40-fold as the pH increases over the same range. The phosphodiesterase activity is not inhibited by chelating agents but is inhibited by several divalent metal ions. 31-P NMR spectroscopy was used to identify the hydrolysis products of glycoside cyclic phosphates. The enzyme-catalyzed hydrolysis of methyl beta-D-ribofuranoside cyclic 3:5-phosphate yields exclusively the 5-phosphate whereas that of adenosine 3:5-monophosphate yields a 4:1 mixture of 3- and 5- AMP.
4-Nitrophenylphosphatase↗
Changes in cardiac excitability and vulnerability in NMR fields.
Alterations in ventricular excitability and vulnerability were assessed in nine isolated perfused rabbit hearts in and out of static external magnetic fields (4.7 tesla) associated with radiofrequency pulsing (5 gauss). Ventricular refractoriness was assessed with the strength interval relationship in and out of the NMR magnet. Strength interval curves were measured at threshold, at the midpoint of the strength interval relationship, and at 10 mA. The refractory period measured at threshold was 193 +/- 24 mS outside the magnet and 195 +/- 24 mS inside the magnet (P = ns). Ventricular refractoriness measured at the midpoint of the strength interval curve was 169 +/- 16 mS outside and 167 +/- 17 mS in the magnet (P = ns). At 10 mA the refractory period outside of the magnet was 162 +/- 16 mS and 161 +/- 17 mS in the magnet (P = ns). To assess ventricular vulnerability the repetitive response threshold and the ventricular fibrillation threshold were also determined in and out of the NMR magnet. The repetitive response threshold was 61 +/- 16 mA out of the magnet and 75 +/- 24 mA inside the magnet. This was significant at the P = 0.04 level. The ventricular fibrillation threshold was 71 +/- 14 mA out of the magnet and 81 +/- 20 mA in the magnet (P = ns). In summary, static magnetic fields associated with radiofrequency pulsing have no measureable effect on the strength interval relationship. There is no increase in ventricular vulnerability as assessed by the repetitive response threshold and the ventricular fibrillation threshold.
Animals↗
Uniform safety of beating heart surgery using the octopus tissue stabilization system.
BACKGROUND AND PURPOSE: Minimally invasive coronary artery bypass grafting (CABG) has been facilitated by the introduction of the Octopus Tissue Stabilization system (OTS). OTS improves exposure immobilizing the heart with minimal hemodynamic effects allowing multivessels off cardiopulmonary bypass (CPB) CABG. The purpose of this study was to compare the utilization and clinical outcome of the OTS in three geographically distinct centers. METHODS: 239 patients who underwent OTS-CABG at Allegheny University Hospital/Medical College of Pennsylvania, Harrisburg Hospital, and Park Nicollet Clinic/HealthSystem Minnesota were reviewed. Age, acuity of patients, and number and type of vessels bypassed were recorded. Complications, mortality, length of hospital stay, incidence of conversion to CPB and blood transfusions, and operating room costs were compared to risk matched control patients who underwent CPB CABG during the same period. RESULTS: Results were similar in all three centers. The average age was 62.3 years. Emergent operation was necessary in 7%-10% of patients, the operations averaged 1.8 grafts/patient. Arteries bypassed were LAD, DIAG, OM, RCA, PDA, and RPLB. There were 96% of operations completed without CPB. Morbidity was low (12%). Atrial fibrillation and blood transfusion rate were decreased. Mortality was 0 compared with a predicted mortality of 1.6%. Hospital length of stay was shorter and operating room costs were 61% lower. CONCLUSIONS: OTS provides predictable reproducible immobilization allowing the performance of single and multiple off-pump CABG to almost all coronary branches with minimal morbidity and decreased costs in a variety of patients. Similar findings from three different centers suggests that these results are easily reproducible.
Aged↗
Unusual occurrence of ankylosing spondylitis and multiple sclerosis in a black patient.
A possible association between ankylosing spondylitis (AS) and multiple sclerosis (MS) has been suggested in whites. The authors describe the first report of the coexistence of AS and MS in a black patient. The clinical diagnosis of MS was further substantiated by the results of magnetic resonance imaging of the brain. The diagnosis of AS met the Rome as well as the New York criteria. The patient possessed HLA-B27; his complete HLA phenotype was Aw66, B27, Cw2, DR3, and DR5.
Adult↗
Renal pseudoenlargement secondary to retroperitoneal liposarcoma.
A case of renal pseudoenlargement caused by a large retroperitoneal mass is reported. An intravenous urogram showed apparent enlargement of the right kidney and a normal left kidney. Computed tomography showed a normal-sized right kidney. The discrepancy was due to magnification produced by marked anterior displacement of the right kidney by a retroperitoneal liposarcoma.
Diagnosis, Differential↗
Erythrocyte catalase decreases cardiac reperfusion injury.
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Amitrole↗