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N Krasnow

Publications and source records attributed to N Krasnow.

At least 19 recordsLinked to original sources
PubMed2000

Smaller organ tissue mass in the elderly fails to explain lower resting metabolic rate.

We previously reported our in vivo prediction of whole body resting energy expenditure (REE) using magnetic resonance imaging and echocardiography-derived organ volumes combined with published organ tissue metabolic rates. The models, developed in young healthy persons from predicted and measured variables, were highly correlated (e.g., calculated vs. measured REE, r = 0.92, p < 0.001), with no significant differences (p = NS) between them. This study employed the same approach to determine whether possible age-related decreases in organ tissue mass may account for the lower REE commonly reported in elderly persons. Measurements of REE (REEm) were acquired by indirect calorimetry. Calculated REE (REEc) models were developed from measured tissues and organs, and energy flux rates were assigned for each of the seven tissue/organ components, as reported by Elia. Older men (n = 6) and women (n = 7) had significantly lower REEm compared to REEc (p = 0.001). The magnitude of the differences were 13% and 9.5%, respectively, for men and women. These preliminary data suggest that factors other than organ atrophy may contribute to the lower metabolic rate of older persons. Further studies are required to investigate whether there is a reduction in the oxidative capacity of individual organs and tissues.

Absorptiometry, Photon↗
PubMed1998

Diagnosis of pericardial effusion and its effects on ventricular function using gated Tc-99m sestamibi perfusion SPECT.

Pericardial effusion is a common disorder associated with a variety of medical disorders. Diagnostic methods of choice include echocardiography, CT, and MRI. However, diagnosing pericardial effusion with radionuclides is uncommon. A pericardial effusion under pressure may result in tamponade and hemodynamic compromise, which constitutes a cardiac emergency, necessitating emergency intervention with pericardiocentesis or pericardiotomy. Presented is an unusual case of a patient who was referred to the nuclear cardiology laboratory for evaluation of atypical chest pain using stress and rest Tc-99m sestamibi perfusion SPECT. The patient had a large pericardial effusion evident on planar projection images and tomograms. From the gated perfusion study, the authors were able to evaluate left and right ventricular function and to exclude cardiac tamponade because there was no evidence of diastolic collapse of the right ventricle.

Aged↗
PubMed1998

Organ-tissue mass measurement allows modeling of REE and metabolically active tissue mass.

Investigators have expressed interest in the associations between resting energy expenditure (REE) and body mass for over a century. Traditionally, descriptive models using regression analysis are applied, linking REE with metabolically active compartments such as body cell mass (BCM) and fat-free body mass (FFM). Recently developed whole body magnetic resonance imaging (MRI) and echocardiography methods now allow estimation of all major organs and tissue volumes in vivo. Because measured values are available for REE, BCM, and FFM content of individual organs and tissues, it should now be possible to develop energy expenditure-body composition estimation models based on MRI-measured organ-tissue volumes. Specifically, the present investigation tested the hypothesis that in vivo estimation of whole body REE, BCM, and FFM is possible using MRI- and echocardiography-derived organ volumes combined with previously reported organ-tissue metabolic rates and chemical composition. Thirteen subjects (5 females, 8 males) had REE, BCM, and FFM measured by indirect calorimetry, whole body 40K counting, and dual-energy X-ray absorptiometry, respectively. Models developed from estimated and measured variables were highly correlated, with no significant differences between those estimated and measured [e.g., calculated vs. measured REE: r = 0.92, P < 0. 001; (mean +/- SD) 6,962 +/- 1,455 and 7,045 +/- 1,450 kJ/day, respectively (P = not significant)]. Strong associations were observed between REE, individual or combined organ weights, BCM, and FFM that provide new insights into earlier observed metabolic phenomona. The present approach, the first to establish an energy expenditure-body composition link with a mechanistic model in vivo, has the potential to greatly expand our knowledge of energy expenditure-body size relationships in humans.

Adolescent↗
PubMed1997

Subaortic septal bulge simulates hypertrophic cardiomyopathy by angulation of the septum with age, independent of focal hypertrophy. An echocardiographic study.

Focal hypertrophy of the basal anterior septum occurs not infrequently in elderly patients and is considered by some to be a significant form of hypertrophic cardiomyopathy; others consider it to be an unimportant anatomic variant associated with an angulated septum, called a septal bulge (SB). We analyzed 94 cases of SB collected prospectively and compared them with 88 patients with extensive hypertrophic cardiomyopathy (HCM), 20 patients with hypertrophic cardiomyopathy limited to the entire septum (ASH), and 20 age-matched controls. The SB cases were also divided into three groups, with marked, moderate, or no basal septal hypertrophy associated with the occurrence of an SB. All groups of SB patients had increased fractional shortening compared with controls (0.48 +/- 0.07 versus controls 0.40 +/- 0.07), comparable with HCM (0.48 +/- 0.12), and increased left ventricular outflow tract velocity both at rest and especially after amyl nitrite inhalation (3.42 +/- 1.35 versus 1.55 +/- 0.60 m/sec [controls]). Other features of HCM were not present: normal wall thickness except for the basal septal hypertrophy, no anterior malposition in SB patients, no age-independent reversal of ratio of early to late mitral inflow velocity (E/A), and no decrease in end-diastolic dimension. It is concluded that outflow tract narrowing by an angulated septum is the primary mechanism responsible for the increased outflow tract velocity, rather than the hypertrophic septum. The resultant increase in convective acceleration simulates the dynamics of hypertrophic cardiomyopathy. The focal hypertrophy may be secondary and contributory to the enhanced ventricular dynamics, but it does not appear to be a primary cardiomyopathy.

Age Factors↗
PubMed1990

Sinus of Valsalva aneurysms.

Sinus of Valsalva aneurysms are rare cardiac anomalies which may be acquired or congenital. The congenital aneurysm is more common than the acquired form, with an incidence ranging from 0.1 to 3.5% of all congenital heart defects. Acquired aneurysms may result from trauma, endocarditis, syphilis, Marfan's syndrome, and senile-type dilatation in which the three sinuses dilate as a result of the normal aging process. This review focuses on both congenital and acquired aneurysms with particular attention to the noninvasive diagnosis of this anomaly.

Adolescent↗
PubMed1987

Fatigue, acid-base and electrolyte changes with exhaustive treadmill exercise in hemodialysis patients.

Aerobic conditioning exercises have been shown to be beneficial for maintenance hemodialysis patients, but biochemical changes during exhaustive exercise in these functionally anephric patients have been less thoroughly studied. We evaluated serum biochemical changes in 7 patients during and after treadmill exercise to patient exhaustion. Duration of exercise was limited by lower leg fatigue without claudication. At exhaustion, only mild changes from baseline rest values were noted in arterial pH (7.39 +/- 0.03-7.33 +/- 0.04) and lactate (0.94 +/- 0.3-5.73 +/- 2.68 mmol/l) despite normal exercise-induced intracellular fluid shifts as evidenced by albumin concentration increases (44.9 +/- 2.8-49.3 +/- 3.1 g/l). Increases in serum K+ concentrations are also modest (change in K from baseline = 0.87 +/- 0.22 mmol/l). An explanation for these minimal biochemical alterations at exhaustion is unclear, but could relate to exercise being limited well below estimated maximum cardiac output and muscle O2 extraction levels by early, unexplained muscle fatigue. Fatigue in hemodialysis patients does not appear to be due to muscle hypoxia.

Acid-Base Equilibrium↗
PubMed1985

A familial dilated cardiomyopathy associated with cataracts and hip-spine disease.

A dilated cardiomyopathy was observed in two generations of a kindred, associated with articular disease and premature cataracts, a unique triad not previously described to our knowledge. The cardiomyopathy was characterized histologically by basophilic PAS-positive granulofilamentous deposits in the myocardium. The articular disease included hip joint degeneration, irregular intervertebral disks, and platyspondyly. The lenticular abnormalities may occur in young adults prior to other manifestations of the triad. Consanguinity was noted in the parents, and inheritance was most compatible with an autosomal recessive trait, with variable penetrance and expressivity.

Adult↗
PubMed1980

The distribution patterns of biatrial myxomas.

Biatrial myxomas are extremely rare, and by 1970 only three of eight attempts at removal had been successful. Another successful removal, the difficulty of establishing the biatrial nature of a myxoma by echocardiography, and a summary of the distribution patterns of biatrial myxomas are presented here. In more than 50% of patients, both pedicles grew into separate atrial chambers from a common location in the atrial septum. The surgical implications are discussed.

Aged↗
PubMed1980

Stroke as a complication of mitral valve prolapse.

A patient with mitral valve prolapse had two minor strokes after she stopped taking oral anticoagulants. While routine oral anticoagulant therapy is not indicated for mitral valve prolapse, such therapy is strongly recommended when this condition is accompanied by stroke.

Adult↗
PubMed1980

Clinical value of early exercise testing after myocardial infarction.

The clinical utility of predischarge exercise ECGs was assessed prospectively in 47 patients 17 +/- 2 days after myocardial infarction. The graded-interval ergometric exercise protocol was terminated at 450 kilopond-m/min (kpm/min), a heart rate greater than 75% of predicted maximum, or for established clinical indications. Prior to testing, the attending physician and resident indicated their clinical impressions with regard to anticipated (1) angina, (2) exercise capacity, (3) arrhythmias during limited exercise, as well as anticipated discharge medications and activity prescriptions. Ratings were compared to exercise results and consequent alterations in management noted. No complications were noted during the evaluations. Nine patients noted anginal pain during exercise; five were unsuspected by the attending physician or resident. Ten patients demonstrated significant ventricular arrhythmias. Four were receiving antiarrhythmic therapy. Severe limitation of exercise capacity (< 300 kpm/min) was noted in six patients, unanticipated in four. Where not contraindicated, routine use of predischarge exercise ECG testing is recommended.

Angina Pectoris↗
PubMed1979

Increasing pre-excitation during exercise and isoproterenol infusion. Evidence for a catecholamine sensitive bypass tract.

A patient with atypical chest pain developed pre-excitation during exercise and isoproterenol infusion, with "ischemic" ST depression only during the pre-excited beats. Coronary angiography and myocardial lactate extraction showed no evidence of abnormal coronary vessels. Electrophysiologic study and pacing-induced tachycardia did not induce pre-excitation, whereas exercise induced progressive increase in pre-excitation. The data are consistent with an unusual form of pre-excitation, perhaps related to responsiveness of an accessory bypass tract to catecholamine stimulation. The data also show that the false positive exercise test in this syndrome is due to progressively increasing pre-excitation and therefore more abnormal repolarization.

Adult↗