Relationships of generalized and regional adiposity to insulin sensitivity in men.

The relative impacts of regional and generalized adiposity on insulin sensitivity have not been fully defined. Therefore, we investigated the relationship of insulin sensitivity (measured using hyperinsulinemic, euglycemic clamp technique with [3-3H]glucose turnover) to total body adiposity (determined by hydrodensitometry) and regional adiposity. The latter was assessed by determining subcutaneous abdominal, intraperitoneal, and retroperitoneal fat masses (using magnetic resonance imaging) and the sum of truncal and peripheral skinfold thicknesses. 39 healthy middle-aged men with a wide range of adiposity were studied. Overall, the intraperitoneal and retroperitoneal fat constituted only 11 and 7% of the total body fat. Glucose disposal rate (Rd) and residual hepatic glucose output (rHGO) values during the 40 mU/m2.min insulin infusion correlated significantly with total body fat (r = -0.61 and 0.50, respectively), subcutaneous abdominal fat (r = -0.62 and 0.50, respectively), sum of truncal skinfold thickness (r = -0.72 and 0.57, respectively), and intraperitoneal fat (r = -0.51 and 0.44, respectively) but not to retroperitoneal fat. After adjusting for total body fat, the Rd and rHGO values showed the highest correlation with the sum of truncal skinfold thickness (partial r = -0.40 and 0.33, respectively). We conclude that subcutaneous truncal fat plays a major role in obesity-related insulin resistance in men, whereas intraperitoneal fat and retroperitoneal fat have a lesser role.

Assessment of coronary arterial restenosis with phase-contrast magnetic resonance imaging measurements of coronary flow reserve.

BACKGROUND: After successful percutaneous coronary arterial revascularization, 25% to 60% of subjects have restenosis, a recurrent coronary arterial narrowing at the site of the intervention. At present, restenosis is usually detected invasively with contrast coronary angiography. This study was performed to determine if phase-contrast MRI (PC-MRI) could be used to detect restenosis noninvasively in patients with recurrent chest pain after percutaneous revascularization. METHODS AND RESULTS: Seventeen patients (15 men, 2 women, age 36 to 77 years) with recurrent chest pain >3 months after successful percutaneous intervention underwent PC-MRI measurements of coronary artery flow reserve followed by assessments of stenosis severity with computer-assisted quantitative coronary angiography. The intervention was performed in the left anterior descending coronary artery in 15 patients, one of its diagonal branches in 2 patients, and the right coronary artery in 1 patient. A PC-MRI coronary flow reserve value /=70% and >/=50%, respectively. CONCLUSIONS: Assessments of coronary flow reserve with PC-MRI can be used to identify flow-limiting stenoses (luminal diameter narrowings >70%) in patients with recurrent chest pain in the months after a successful percutaneous intervention.

Visualization and functional assessment of proximal and middle left anterior descending coronary stenoses in humans with magnetic resonance imaging.

BACKGROUND: Coronary artery bypass grafting improves survival in patients with >70% luminal diameter narrowing of the 3 major epicardial coronary arteries, particularly if there is involvement of the proximal portion of the left anterior descending (LAD) coronary artery. Measurement of coronary flow reserve can be used to identify functionally important luminal narrowing of the LAD artery. Although magnetic resonance imaging (MRI) has been used to visualize coronary arteries and to measure flow reserve noninvasively, the utility of MRI for detecting significant LAD stenoses is unknown. METHODS AND RESULTS: Thirty subjects (23 men, 7 women, age 36 to 77 years) underwent MRI visualization of the left main and LAD coronary arteries as well as measurement of flow in the proximal, middle, or distal LAD both at rest and after intravenous adenosine (140 microgram/kg per minute). Immediately thereafter, contrast coronary angiography and when feasible, intracoronary Doppler assessments of coronary flow reserve, were performed. There was a statistically significant correlation between MRI assessments of coronary flow reserve and (a) assessments of coronary arterial stenosis severity by quantitative coronary angiography and (b) invasive measurements of coronary flow reserve (P<0.0001 for both). In comparison to computer-assisted quantitative coronary angiography, the sensitivity and specificity of MRI for identifying a stenosis >70% in the distal left main or proximal/middle LAD arteries was 100% and 83%, respectively. CONCLUSIONS: Noninvasive MRI measures of coronary flow reserve correlated well with similar measures obtained with the use of intracoronary Doppler flow wires and predicted significant coronary stenoses (>70%) with a high degree of sensitivity and specificity. MRI-based measurement of coronary flow reserve may prove useful for identification of patients likely to obtain a survival benefit from coronary artery bypass grafting.

Relationship of generalized and regional adiposity to insulin sensitivity in men with NIDDM.

Abdominal obesity, particularly excess intraperitoneal fat, is considered to play a major role in causing insulin resistance and NIDDM. To determine if NIDDM patients accumulate excess intraperitoneal fat, and whether this contributes significantly to their insulin resistance, 31 men with mild NIDDM with a wide range of adiposity were compared with 39 nondiabetic, control subjects for insulin sensitivity (measured using euglycemic-hyperinsulinemic clamp technique with [3-3H]glucose turnover) and total and regional adiposity (assessed by hydrodensitometry and by measuring subcutaneous abdominal, intraperitoneal, and retroperitoneal fat masses using magnetic resonance imaging [MRI], and truncal and peripheral skinfold thicknesses using calipers). MRI analysis revealed that intraperitoneal fat was not increased in NIDDM patients compared with control subjects; in both groups it averaged 11% of total body fat. NIDDM patients, however, had increased truncal-to-peripheral skinfolds thickness ratios. In NIDDM patients, as in control subjects, amounts of truncal subcutaneous fat showed a stronger correlation with glucose disposal rate than intraperitoneal or retroperitoneal fat; however, NIDDM patients were more insulin resistant at every level of total or regional adiposity. Further, no particular influence of excess intraperitoneal fat on hepatic insulin sensitivity was noted. We conclude that NIDDM patients do not have excess intraperitoneal fat, but that their fat distribution favors more truncal and less peripheral subcutaneous fat. Moreover, for each level of total and regional adiposity, NIDDM patients have a heightened state of insulin resistance.

Nuclear magnetic resonance imaging in Marfan's syndrome.

Detection and evaluation of aortic root and other cardiovascular abnormalities in patients with Marfan's syndrome are important in determining appropriate therapy and preventing premature mortality. To evaluate the role of nuclear magnetic resonance imaging (NMR) in this syndrome, 10 patients were evaluated using a 0.35 tesla commercial nuclear magnetic resonance imaging system. Findings from these studies were compared with data from other noninvasive tests as well as surgical follow-up. Results from these examinations indicate that NMR-derived measurements of aortic root diameter agree closely with echocardiographic measurements. In addition, NMR provides more complete anatomic detail than does echocardiography and can be utilized to assess and follow up virtually all patients with this syndrome.

Administration of an intravenous perfluorocarbon contrast agent improves echocardiographic determination of left ventricular volumes and ejection fraction: comparison with cine magnetic resonance imaging.

OBJECTIVES: The purpose of this study was to determine whether contrast-enhanced transthoracic echocardiography improves the evaluation of left ventricular (LV) volumes and ejection fraction (EF). BACKGROUND: Echocardiographic assessment of LV volumes and EF is widely used but may be inaccurate when the endocardium is not completely visualized. Recently the intravenous (i.v.) administration of perfluorocarbon microbubbles has been shown to enhance opacification of the LV cavity, but the utility of these agents to improve the echocardiographic assessment of LV systolic function is unknown. METHODS: In 40 subjects (29 men and 11 women, aged 24 to 81 years) an assessment of LV volumes and EF was performed with a magnetic resonance imaging examination, followed immediately by a transthoracic echocardiogram before and after the intravenous administration of 2% dodecafluoropentane emulsion (EchoGen; Sonus Pharmaceuticals, Bothell, Washington). RESULTS: Contrast enhanced the echocardiographic assessment of LV end diastolic volume (p < 0.02), end systolic volume (p < 0.01) and LVEF (p < 0.03). The percentage of subjects in whom the correct echocardiographic classification EF was normal, mild to moderately depressed or severely reduced improved significantly after contrast enhancement (from 71% before contrast to 94% after, p < 0.03). These findings were most striking in the subjects with two or more adjacent endocardial segments not visualized at baseline. CONCLUSIONS: Administration of an intravenous contrast agent improves the ability to accurately assess LV volumes and EF in humans. Contrast enhancement is most useful in subjects with two or more adjacent endocardial segments not seen at baseline.

In vivo measurement of myocardial mass using nuclear magnetic resonance imaging.

To examine the accuracy of nuclear magnetic resonance imaging in measuring left ventricular mass, measurements of left ventricular mass made using this technique were compared with left ventricular weight in 10 mongrel dogs. Left ventricular myocardial volume was measured from five short-axis end-diastolic images that spanned the left ventricle. Left ventricular mass was calculated from left ventricular myocardial volume and compared with the left ventricular weight determined after formalin immersion-fixation. Linear regression analysis yielded the following relation in grams: left ventricular mass determined using nuclear magnetic resonance imaging = (0.94) (left ventricular weight) + 9.1 (r = 0.98, SEE = 6.1 g). The small overestimation of left ventricular weight by nuclear magnetic resonance imaging was judged to be secondary to both difficulty with proper border definition and partial volume effects. Hence, this imaging technique can be used to obtain accurate measurements of left ventricular mass in dogs in vivo.

Gadolinium-DTPA-enhanced nuclear magnetic resonance imaging of reperfused myocardium: identification of the myocardial bed at risk.

Gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA)-enhanced nuclear magnetic resonance (NMR) imaging can be useful in the identification of reperfused myocardium. However, the effects of dose and the time of administration and the relation of the extent of the region of enhancement to the myocardial bed at risk have not been evaluated. In this study, dogs were given Gd-DTPA (0.1 mM/kg body weight [n = 21] or 0.34 mM/kg [n = 7]) or saline solution (n = 5) after various periods of occlusion and reperfusion. Twenty-five dogs were killed after 1 or 2 h of reperfusion and the excised hearts were imaged. Images were analyzed for presence, intensity and extent of a region of increased signal. All images in dogs given Gd-DTPA had easily identifiable regions of increased signal in the distribution of the reperfused myocardial bed. Analysis of the extent of these regions in spin-echo images of excised hearts when Gd-DTPA was administered after 5 min of reperfusion demonstrated a correlation coefficient of 0.72 with the bed at risk as determined postmortem with a dye perfusion technique. These images consistently overestimated the infarct size. Signal intensity of the reperfused myocardium increased to a maximum of 1.67 times control (p less than 0.05) in spin-lattice relaxation time (T1)-weighted sequences as the dose of Gd-DTPA increased. This was due to a higher concentration of Gd-DTPA in the reperfused myocardium with resultant shortening of the T1 relaxation time. When Gd-DTPA was given after 90 min of reperfusion, NMR images did not identify the bed at risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of myocardial systolic wall thickening using nuclear magnetic resonance imaging.

A quantitative nuclear magnetic resonance (NMR) imaging method of evaluating regional left ventricular function was compared with histochemical evidence of infarction in dogs and functional measurements in patients. Short-axis images of the heart were obtained at end-diastole and at 100 ms intervals thereafter. Regional diastolic left ventricular wall thickness and maximal percent systolic wall thickening were measured at the level of the papillary muscles in each of six segments. In six normal dogs, the mean end-diastolic wall thickness was 9 +/- 1.6 mm, and the mean maximal percent thickening was 61 +/- 11%. In eight dogs with a 4 day old infarct, maximal percent thickening was 5 +/- 8% (p less than 0.001) in the infarcted segments. In 10 normal human volunteers, the mean end-diastolic wall thickness was 10.1 +/- 1 mm, and the mean maximal percent systolic wall thickening was 60 +/- 18%. Reduced maximal percent systolic wall thickening was defined as a value greater than or equal to 2 SD below the mean value obtained in normal volunteers. Seven patients with regional wall motion abnormalities were independently assessed by NMR imaging and biplane ventriculography. With a sensitivity of 94% and a specificity of 80%, NMR imaging demonstrated reduced maximal percent systolic wall thickening in the same segments identified as akinetic or dyskinetic by biplane ventriculography. Thus, abnormalities of regional systolic wall thickening are accurately identified with this quantitative imaging technique.

In vivo nuclear magnetic resonance imaging of myocardial perfusion using the paramagnetic contrast agent manganese gluconate.

Previous nuclear magnetic resonance (NMR) imaging studies have indicated that coronary occlusion does not produce sufficient changes in standard tissue relaxation times to allow the detection of acute ischemia. To identify acute myocardial perfusion abnormalities, the use of the paramagnetic agent manganese gluconate combined with calcium gluconate (MnGlu/CaGlu) was investigated in canine models of acute coronary artery occlusion. In vitro studies showed that MnGlu/CaGlu was a more efficient relaxing agent than gadolinium-DTPA (relaxivity of 7.8 versus 5.1 s-1 mM-1) and demonstrated affinity for normal myocardium. The distribution of MnGlu/CaGlu as measured by manganese-54 tracer studies was proportional to myocardial blood flow in both normal and ischemic tissue. Hearts excised from dogs after coronary artery occlusion and administration of 0.035 mM/kg MnGlu/CaGlu were imaged ex vivo using a relatively spin-lattice relaxation time (T1)-weighted gradient reversal technique (repetition time [TR] 50 ms and echo time [TE] 9 ms). These images showed increased signal intensity in the normally perfused myocardium with a mean signal intensity ratio of hypoperfused to normal myocardium of 0.55 +/- 0.12 (mean +/- SD). In vivo images obtained in nine dogs after coronary artery occlusion and administration of the same dose of MnGlu/CaGlu demonstrated the region of hypoperfused myocardium in six dogs with a signal intensity ratio of hypoperfused to normal myocardium of 0.64 +/- 0.23 (p less than 0.05 versus control). When a higher dose of 0.1 mM/kg MnGlu/CaGlu was utilized and in vivo imaging was performed using a relatively spin-spin relaxation time (T2)-weighted (TR gated, TE 60 ms) spin-echo sequence in six dogs, the signal intensity of normal myocardium was decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise-induced attenuation of alpha-adrenoceptor mediated vasoconstriction in humans: evidence from phase-contrast MRI.

OBJECTIVE: We recently provided evidence for contraction-induced attenuation of reflex sympathetic vasoconstriction in human skeletal muscle microcirculation. We now asked whether contraction-induced modulation of alpha-adrenoceptor mediated vasoconstriction in the human forearm (a) is evident in a large artery supplying the contracting skeletal muscle and (b) implicates a post-junctional site of action. METHODS AND RESULTS: To address these questions in humans, we used phase-contrast magnetic resonance imaging to measure blood flow velocity and cross-sectional area of the brachial artery during brachial-artery infusion of the alpha-adrenoceptor agonist norepinephrine (NE) (1.1 g/min for 5 min) at rest and during mild ipsilateral rhythmic handgrip (20% of maximum). At rest, brachial artery conductance decreased progressively during the entire 5 min period of infusion (baseline to first half to second half of infusion: 0.421 +/- 0.157 to 0.255 +/- 0.187 to 0.012 +/- 0.014 ml/min/mmHg, P < 0.05). When NE was superimposed on handgrip, conductance at first decreased sharply (1.205 +/- 0.127 to 0.330 +/- 0.097 ml/min/mmHg, P < 0.05). However, during the second half of the infusion, conductance did not decrease further but rather returned progressively toward baseline (0.476 +/- 0.199 ml/min/mmHg at the end of the exercise, P < 0.05 vs. NE alone). CONCLUSION: These data provide new evidence in humans that alpha-adrenoceptor mediated vasoconstriction is sensitive to modulation by skeletal muscle contraction. Such modulation is evident at the level of a large conduit artery and it involves a post-junctional mechanism of action.

Adipose tissue distribution pattern in patients with familial partial lipodystrophy (Dunnigan variety).

Familial partial lipodystrophy, Dunnigan type (FPLD), is a rare autosomal dominant genetic disorder characterized by gradual loss of sc fat from the extremities, commencing at the time of puberty. Excess fat deposition may occur in the face and neck area. Limited information is available about adipose tissue distribution in patients with FPLD. To investigate whether there is a unique pattern of fat distribution in both affected men and women with FPLD, we performed whole-body magnetic resonance imaging in one male and three female patients from two pedigrees. Magnetic resonance imaging studies confirmed the clinical findings of near-total absence of sc fat from all extremities. Reduction in sc adipose tissue from the truncal area was more prominent anteriorly than posteriorly. Increased fat stores were observed in the neck and face. Intermuscular adipose tissue in the extremities and pelvic area were subjectively increased. Intraabdominal and intrathoracic adipose tissue was not reduced. Bone marrow fat, as well as mechanical adipose tissue, was present in normal amounts. The pattern of fat distribution in the male and females was similar. We conclude that FPLD results in a characteristic absence of sc fat from the extremities, with preservation of intermuscular fat stores.

Peculiar distribution of adipose tissue in patients with congenital generalized lipodystrophy.

Congenital generalized lipodystrophy (CGL) is a rare genetic disease with extreme paucity of fat from birth which is believed to be generalized, involving the whole body. Affected patients are characterized by severe insulin resistance. Sites of adipose tissue distribution in patients with CGL have not been studied systematically. Therefore, the fat distribution in three women (17-20 yr old) with CGL was investigated. Determination of body composition by underwater volume displacement suggested the complete absence of body fat (range, -3 to -7%; normal, 15-25%). Whole body magnetic resonance imaging, however, detected fat in particular anatomical sites, namely in orbits, palms and soles, and periarticular and epidural regions. Some fat was also localized in the tongue, breasts, vulva, and buccal area. Fat in other subcutaneous areas, intraabdominal and intrathoracic regions, and bone marrow was essentially absent. Thus, patients with CGL do not have a complete absence of body fat; of interest, fat is present in those sites where adipose tissue may be serving mainly a mechanical function. Patients with CGL, therefore, provided a unique opportunity to identify the various sites of localization of "mechanical" adipose tissue in the human body. Our study suggests that the genetic defect in CGL results in poor growth and development of metabolically active adipose tissue, whereas mechanical adipose tissue is well preserved.

Prediction of total subcutaneous abdominal, intraperitoneal, and retroperitoneal adipose tissue masses in men by a single axial magnetic resonance imaging slice.

To develop a simplified but accurate method for determining the masses of various abdominal adipose tissue compartments, we studied the predictive value of masses of intraperitoneal, retroperitoneal, and subcutaneous abdominal adipose tissue determined on single axial abdominal magnetic resonance imaging (MRI) slices taken at various intervertebral levels from the 12th thoracic to 1st sacral vertebra (identified on a sagittal section) for the respective total masses of each compartment calculated from contiguous 10-mm thick MRI slices covering the entire abdomen in 49 men (26 without diabetes and 23 with non-insulin-dependent diabetes mellitus). The MRI slice at the intervertebral level between the lumbar (L) 2 and 3 vertebrae showed the highest and most consistent predictive value for all three compartments (R2 = 0.85 for all). Furthermore, compared with other intervertebral levels, the L2-L3 level had a higher amount of intraperitoneal and retroperitoneal adipose tissue mass. We conclude that determining the masses of various abdominal adipose tissue compartments at the L2-L3 intervertebral level by MRI is an acceptably reliable and accurate method for studying abdominal adiposity in men.

Three-dimensional motion and perfusion quantification in gated single-photon emission computed tomograms.

Methods for quantification and display of left ventricular (LV) functional parameters from gated single-photon emission computed tomographs are described. Using previously documented surface detection methods, we developed techniques for calculating global variables, such as volumes and areas, as well as local variables such as segmental motion and local perfusion from gated tomographic radionuclide ventriculograms (TRVG) and gated perfusion tomograms (sestamibi). We have developed three-dimensional displays to allow realistic visualizations of the results. The motion results have been validated using correlative magnetic resonance imaging (MRI) studies; motion calculated from user-traced MR images of the heart was compared to motion calculated from automatically detected surfaces in TRVG and sestamibi. The average motion error was calculated to be 0.67 mm in TRVG and -0.21 mm in sestamibi. Errors were largest in basal LV regions; we explain this phenomenon using simulations. Finally, we present additional examples of the analysis using studies obtained from normal volunteers and from subjects whose coronary artery anatomies were known.

Measurement of blood-retinal barrier breakdown in endotoxin-induced endophthalmitis.

PURPOSE: Endophthalmitis is a severe inflammatory disorder with profound visual consequences. Treatment of this disorder has been limited by the lack of quantitative information regarding retinal responses to severe inflammation. The purpose of this study was to measure the effect of endotoxin-induced endophthalmitis on blood-retinal barrier (BRB) function in vivo using contrast-enhanced magnetic resonance imaging (MRI). METHODS: Endophthalmitis was produced by injecting Escherichia coli endotoxin into the midvitreous of pigmented rabbits. Contrast-enhanced MRI was performed at selected intervals thereafter. In all cases, a clinical grading system was used to assess the severity of inflammation before imaging. In a dose-response experiment, total vitreous protein was measured from vitreous specimens obtained 1 day after endotoxin injection and immediately after the imaging procedure. RESULTS: At 1 day after injection, endotoxin produced a selective breakdown of the inner BRB at all doses evaluated (0.01 microgram to 500 micrograms). Permeability-surface area product normalized to the area of leaky retina (PS') increased from 1.35 +/- 0.78 x 10(-4) cm/minute (mean +/- SEM, n = 4 eyes) at a dose of 0.01 microgram to 8.15 +/- 2.22 x 10(-4) cm/minute n = 4) eyes) at a dose of 10 micrograms. Inner BRB integrity was restored by day 28 after injection. In general, changes in PS', blood-aqueous barrier leakage, mean clinical score, and vitreous protein concentration were found, but the correlation between any two of these parameters was poor. CONCLUSION: Leakage of contrast appears early in the course of endotoxin-induced endophthalmitis and is a self-limited process. In future studies, these quantifiable changes in BRB permeability should prove useful in the assessment of various therapeutic interventions.

Clinical cardiovascular magnetic resonance imaging.

Magnetic resonance imaging (MRI) is a powerful tool providing high-resolution images of the heart and great vessels without the use of ionizing radiation or contrast agents. MRI systems currently in use at many hospitals can be used effectively in the routine, clinical evaluation of many forms of cardiovascular disease, including great vessel disease, ischemic cardiac disease and congenital cardiac disease. Moreover, quantitative and cine MRI techniques are now available, which provide highly accurate measures of chamber size, wall motion and wall thickening. Recent developments in the areas of myocardial tagging, high-speed imaging and MR assessments of flow and perfusion suggest potential for an increasing role of MRI in the clinical evaluation of the cardiovascular system.

Deep venous contribution to hydrostatic blood volume change in the human leg.

The causes of orthostatic intolerance following prolonged bed rest, head-down tilt or exposure to zero gravity are not completely understood. One possible contributing mechanism is increased venous compliance and peripheral venous pooling. The present study attempted to determine what proportion of the increased calf volume during progressive venous occlusion is due to deep venous filling. Deep veins in the leg have little sympathetic innervation and scant vascular smooth muscle, so their compliance may be determined primarily by the surrounding skeletal muscle. If deep veins make a large contribution to total leg venous compliance, then disuse-related changes in skeletal muscle mass and tone could increase leg compliance and lead to decreased orthostatic tolerance. The increase in deep venous volume during progressive venous occlusion at the knee was measured in 6 normal subjects using calf cross-sectional images obtained with magnetic resonance imaging. Conventional plethysmography was used simultaneously to give an independent second measurement of leg volume and monitor the time course of the volume changes. Most of the volume change at all occlusion levels (20, 40, 60, 80 and 100 mm Hg) could be attributed to deep venous filling (90.2% at 40 mm Hg and 50.6% at 100 mm Hg). It is concluded that a large fraction of the calf volume change during venous occlusion is attributable to filling of the deep venous spaces. This finding supports theories postulating an important role for physiological mechanisms controlling skeletal muscle tone during orthostatic stress.

Left ventricular mass as determined by magnetic resonance imaging in male endurance athletes.

Although many studies of the effect of dynamic exercise training on left ventricular (LV) mass have been reported, controversy continues to exist. Previous work has been criticized because of the techniques used for measuring LV mass, the variable level of training of the subjects recruited and the methods used to normalize the data. In an attempt to resolve this controversy, LV mass was determined using the very accurate and reproducible technique of magnetic resonance imaging (MRI). Highly trained competitive athletes including cross-country skiers, endurance cyclists and long distance runners (VO2max = 77 +/- 1, 72 +/- 2 and 75 +/- 2 ml (kg X min)-1, respectively) were examined. The data were normalized for body weight, body surface area and lean body mass. LV mass was significantly greater in skiers (239 +/- 9 g), runners (244 +/- 10 g) and cyclists (258 +/- 11 g) when compared with nonathletic control subjects (189 +/- 6 g) (p less than 0.001), which represents percent differences of 26, 29 and 37%, respectively. LV mass remained greater in the athletes, regardless of the method used to normalize the data. In addition, there was a good correlation between LV mass and VO2max (r = 0.80, p less than 0.001). It was concluded that LV mass is significantly greater in highly trained competitive endurance athletes and that normalizing LV mass with respect to body weight, body surface area or lean body mass does not alter this relation.

Hydrogen peroxide contrast echocardiography.

Several agents are used as echocardiographic contrast agents, but their unreliability discourages routine clinical use. Studies from the early 1960s suggest that dilute hydrogen peroxide (H2O2) is a safe intravascular agent. Its use was evaluated in contrast echocardiography. To obtain dense opacification reliably, H2O2 (3%) was passed through a sterile 0.2 micron Millipore filter and diluted with heparinized saline solution to make a 0.1 to 0.2% solution. A drop of blood was withdrawn from an indwelling peripheral venous needle into a syringe containing 0.5 to 2.0 ml of the dilute H2O2 and the contents injected. Studies in dogs, normal adults and 36 patients with noncyanotic congenital and acquired cardiac disorders produced dense opacification with no complications. In vitro mixture of H2O2 (0.3%) with leukocyte-poor blood or plasma produced only a few microbubbles, while addition to whole blood or buffy coat produced many, suggesting a role for leukocyte peroxidase. H2O2 contrast echocardiography is simple, inexpensive, and reliably provides dense, sustained opacification. This study and previous studies suggest that intravenous injection of 0.2% H2O2 can be done safely. Great caution should be exercised in patients with severe pulmonary hypertension or large right-to-left shunts because little clinical experience with H2O2 is available.