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Three patients with history of documented hypotension, near syncope, or syncope before or after the administration of isoproterenol during head-up tilt table are reported. Severe bradycardia was also noted in one patient. All three patients responded to the administration of 2.5 mg of oral dextroamphetamine 45 minutes prior to a repeat head-up tilt table study. The potent central and peripheral adrenergic agonist pharmacological properties of this drug permitted the prevention of severe vasodepressor syncope in these patients.

Severe methylenetetrahydrofolate reductase (MTHFR) deficiency with less than 2% of normal enzyme activity is characterized by neurological abnormalities, atherosclerotic changes, and thromboembolism. We have discovered a "new" variant of MTHFR deficiency which is characterized by the absence of neurological abnormalities, an enzyme activity of about 50% of the normal value, and distinctive thermolability under specific conditions of heat inactivation. In this study, lymphocyte MTHFR specific activities in the thermolabile variant and control groups were 5.58 +/- 0.91 and 10.33 +/- 2.89 nmol formaldehyde formed/mg protein/h, respectively. The difference was significant (P less than .01). However, there was overlap among the individual values from the two groups. On the other hand, residual MTHFR activity after heat inactivation was 11.2 +/- 1.43% in the thermolabile variant and 36.3 +/- 5.18% in the controls. There was no overlap. Enzyme studies in 10 subjects with thermolabile MTHFR and their family members support the hypothesis that thermolabile MTHFR is inherited as an autosomal recessive trait. To elucidate the association of thermolabile MTHFR with the development of coronary artery disease, we determined the thermostability of lymphocyte MTHFR in 212 patients with proven coronary artery disease and in 202 controls without clinical evidence of atherosclerotic vascular disease. Thermolabile MTHFR was found in 36 (17.0%) cardiac patients and 10 (5.0%) controls. The difference in incidence between the two groups was statistically significant (P less than .01). The average age at onset of clinical coronary artery disease in 36 patients with thermolabile MTHFR was 57.3 +/- 7.6 years (35-72 years). The mean total plasma homocysteine concentration in patients with thermolabile MTHFR was 13.19 +/- 5.32 nmol/ml and was significantly different from the normal mean of 8.50 +/- 2.80 nmol/ml (P less than .05). There was no association between thermolabile MTHFR and other major risk factors. We conclude that thermolabile MTHFR is a variant(s) of MTHFR deficiency which is inherited as an autosomal recessive trait. In addition, it is positively associated with the development of coronary artery disease. Determination of in vitro thermostability of lymphocyte MTHFR is a reliable method for identifying subjects with this abnormality.

• A 58-year-old woman had a unilateral, solitary breast lesion determined by biopsy to be due to giant cell arteritis. Clinical, laboratory, and pathological findings in this patient and in other patients reviewed from the literature revealed that characteristically patients with giant cell arteritis of the breast have (1) tender unilateral or bilateral nodules at times mimicking breast carcinoma; (2) significant constitutional symptoms of anorexia, weight loss, myalgias, fever, and arthralgias; (3) marked elevation of the erythrocyte sedimentation rate; (4) normal or mildly decreased hemoglobin values and normal or slightly elevated leukocyte counts; (5) normal temporal artery biopsy findings; (6) rare organ involvement; and (7) rapid improvement after prednisone therapy or frequent spontaneous resolution. This mode of presentation suggests features of a unique syndrome since many patients had no systemic involvement, require no treatment at all, and had a self-limited clinical course. ( Arch Intern Med. 1990;150:900-904)

The mechanisms and potential mediator of hypercapneic pulmonary hypertension are incompletely understood. We studied 18 dogs, anaesthetised and spontaneously breathing both room air and after the inhalation of a gas mixture containing 10% CO2, 20.9% O2, and 69.1% N2, to determine the role of histamine, serotonin, and acidaemia in pulmonary hypertension produced by hypercapnia. Hypercapnia increased the mean pulmonary artery pressure by 0.33 kPa (2.5 mmHg) while wedge pressure and pulmonary arteriolar resistance did not change. Cardiac output significantly increased, indicating that the pulmonary hypertensive effect of hypercapnia is mainly flow related. Neither chlorpheniramine nor methysergide had significant effects on hypercapneic pulmonary hypertension. The infusion of sodium bicarbonate corrected the pH; pulmonary artery pressure and cardiac output increased while pulmonary arteriolar resistance dropped, suggesting that the increased cardiac output masked the effect of pH on pulmonary arteriolar resistance. The lack of effect of chlorpheniramine or methysergide on pulmonary resistances indicates that the vasoconstrictive effect of increased hydrogen ion concentration which accompanies hypercapnia is attributable neither to histamine nor to serotonin release.

Oversensing and recycling due to a pacemaker stimulus after-potentials are recognized complications of non-competitive pacing. Often masquerading as T-wave sensing, after-potential oversensing may result in slowing or acceleration of pacing rate. We report two cases of after-potential oversensing in patients with R-wave inhibited (VVI) programmable pulse generators. In both cases, recycling of the pulse generators by the sensed after-potentials resulted in slowing of the pacing rates. This phenomenon was abolished non-invasively by decreasing the duration or width of the stimulus pulse which diminished the magnitude of the after-potential signal.

Two patients found to have congenital absence of the circumflex coronary artery are reported. The clinical, electrocardiographic, vectorcardiographic, and cineangiographic findings are presented. No distinctive clinical or laboratory abnormalities were found except for the unusual anatomical posterior origin of the ostium of the main left coronary artery.

Summary Eight patients with complete A-V block were studied during cardiac pacing at multiple ventricular rates to provide information about the mathematical relationship between Q-T and R-R intervals for each patient. Six of eight patients had the highest regression coefficient when the logarithm of the R-R interval was related to the Q-T interval. Cube root treatment of the R-R interval yielded the best fit equation in two patients. Analysis of the regression coefficients of all eight patients indicates that, within a range of heart rates between 35 and 130 beats/min. there were no significant differences among analyses conducted with the logarithm of the R-R interval, or with the R-R interval raised to exponents of 1., 0.5 or 0.33. The small scatter of data obtained within a single patient studied at multiple rates is in contrast to the large scatter encountered in studies of large numbers of patients. Correspondingly, previously described simple linear regression equations should provide meaningful estimates of predicted Q-T interval by extrapolation from information contained in electrocardiograms obtained prior to illness in a given patient.

Reports of four patients demonstrate the value of angiocardiography in the diagnosis of hilar masses. Two patients had large pulmonary arteries after initial diagnoses of carcinoma; hilar tumors were erroneously called large pulmonary arteries in the other two patients. Pulmonary angiocardiography is more valuable than routine x-ray films and laminography in the definition of hilar masses.

A case of Touraine-Solente-Gole syndrome ( a primary, idiopathic, and familial form of hypertropic osteoarthropathy) is described in a 42–year-old man. The syndrome was partially expressed in the man's father, three brothers, and in the son of one of these brothers. Chromosome studies revealed normal comple-ments in the man, his two sons, and in an older brother. An earlier finding of the XYY trisomy in this syndrome is thought to be fortuitous.

Pelvic lipomatosis is a disease characterized by abnormal deposition of mature adipose tissue within the confines of the pelvis surrounding the bladder, prostate, and rectosigmoid. The presenting symptoms are vague and nonspecific, and it has typical radiologic features. Computed tomography is extremely useful in the differential diagnosis because of its ability to differentiate fatty infiltration from other conditions which can cause elevation and compression of the urinary bladder and sigmoid colon. Computed tomographic confirmation of the presence of fat surrounding the bladder and rectum eliminates the need for surgical biopsy, unless indicated for other reasons. The course of this disease is usually benign and indolent, however a close follow-up is mandatory to rule out those cases in which ureteral obstruction may develop requiring surgical relief of the obstruction. When cystitis glandularis is found in association with pelvic lipomatosis, periodic cystoscopic examinations are recommended because of the potential risk of malignant transformation.

The findings in two patients with angiographically proven massive pulmonary embolism and with clinical and phonocardiographic evidence of abnormal respiratory movement of the pulmonic sound are reported. One patient with complete right bundle-branch block and another with normal conduction had a wide and fixed split second sound with a loud pulmonic component. Both patients had a moderate degree of pulmonary hypertension. Approximately two weeks after administration of heparin, the pulmonic sound moved normally during respiration in both patients. Thromboembolic pulmonary hypertension regressed in one patient and remained unchanged in the other. Changes in impedance through the large pulmonary arteries are are postulated to be responsible for the abnormal movement of the pulmonic valve during both phases of respiration. Wide expiratory splitting of the second sound should be an important clue in the diag nosis of acute massive pulmonary embolism, and the reappearance of a normal inspiratory splitting could be used at the beside to assess indirectly the rate of resolution of the blood clots.

Exercise electrocardiography and selective coronary arteriography was per formed in 24 consecutive patients with complete bundle branch block. The criteria for a positive exercise electrocardiogram (E-ECG) were a 1 mm depres sion or elevation in the J point from the control state, as well as in the ST segment measured at 0.04 seconds from the J point. Eleven of 12 patients with complete left bundle branch block had a positive E-ECG. Nine of them had normal coronary arteriograms, except one with less than 50% lesions in two arteries. Two patients had severe three-vessel disease. Only one patient had a true negative exercise test. No patient had a false negative test. Nine of 12 patients with complete right bundle branch block had a positive E-ECG. One of these 9 had minimal nonobstructive disease, while the other 8 had severe two- or three-vessel coronary artery disease. Three of the 12 right bundle branch block patients had a negative E-ECG. Two of them had a true negative exercise test, and one a false negative test. Because of a high incidence of probably false positive results, E-ECG appears to be unreliable in detecting coronary artery disease in patients with complete left bundle branch block. But it can provide useful information in the non- invasive evaluation of coronary artery disease in patients with complete right bundle branch block.

One hundred three patients with ischemic heart disease (IHD) were compared with 29 patients with organic heart disease and normal coronary arteries (OHD) and with a control group of 101 patients free of heart disease and matched for age and sex. Twelve patients in the control group, 4 in the OHD group, and 34 patients in the IHD group were found to have hearing loss (HL) of different degrees, cause, and duration (P = 0.0003). Of the HL-IHD group, 19 of the 34 patients had no underlying etiologic factor compared with 4 of the 12 patients in the control group (P = 0.0005); age was not an important factor. Multiple logistic regression analysis suggests that the probability of a patient with HL of unknown etiology to have IHD is eight times greater than in individuals with normal hearing. In the HL groups (12 controls and 34 with IHD), there were no significant differences in sex, hypertension, obesity, or smoking, but there was a lower incidence of diabetes and a higher incidence of family history in the HL-IHD group than in the HL-control group. Two patients in the HL-IHD group had families with many members affected by both deafness and IHD, suggesting a heredofamilial disease. HL always preceded the clinical manifestation of IHD and appears to be an important "early marker" of a vascular or generalized arteriosclerotic process.

One hundred and fifteen consecutive symptomatic patients undergoing graded exercise testing, selective coronary angiography and left ventriculography were retrospectively evaluated. The sensitivity, specificity, and false negative response rates of the exercise tests were 79%, 81%, and 21%, respectively. Although the magnitude of a positive ST-segment response was related to more extensive vascular disease, the frequency of false negative responses was nearly identical in patients with single, double, or triple vessel disease (22%, 21%, 19%). Analysis of the false negative group demonstrated significant ventriculographic and hemodynamic abnormalities when compared to the true positive responders. Five out of six patients with the most serious motion disorders in the study fell into the false negative group. There were no significant differences in the extent, distribution and severity of vascular involvement, or in the development of collateral circulation in the two groups. However, occluded vessels supplied abnormal ventricular segments more frequently in the false negative group (88% vs 38%); the absence of an "ischemic response" and the presence of segments of abnormal myocardium may be related. Left ventricular dysfunction appears to be an important reason for a false negative response to exercise.

Summary Diverse results have been found when the effect of the adrenergic nervous system on the duration of electrical systole has been tested in various animals. The present study was designed to determine whether beta adrenergic stimulation shortened the Q-T interval at any given heart rate in man. Right atrial pacing at several rates was carried out before and during the administration of isoproterenol in six subjects. The Q-T interval shortened linearly as the R-R interval shortened. The administration of isoproterenol did not alter the Q-T interval at comparable heart rates as determined by rank sum analysis of Q-T intervals. The results were similar in a single study of a denervated heart, indicating that the results were not masked by rate-related release of endogenous catecholamine. These data demonstrate that beta adrenergic stimulation by the intravenous infusion of isoproterenol did not modify the duration of electrical systole in man independently of its effect on heart rate.

HEMATURIA is a well recognized occurrence in the course of sickle cell trait and anemia. Since hematuria occurs with relatively high frequency,1-5other causes of hematuria are often overlooked in patients who exhibit sickling. Two cases of acute glomerulonephritis in children with type S hemoglobin are presented to illustrate the concurrence of these diseases. Report of Cases Case1.—A 2 year 5 month-old Negro boy was well until three weeks prior to admission, when he suffered multiple mosquito bites, several of which became infected. For the four days prior to admission, decreased urination, increased weight, and edema were noted. Physical examination on admission revealed an acutely ill child with a temperature of 102 F (38.9 C); blood pressure, 120/90 mm Hg; pulse rate, 140 beats per minute, and respiration rate, 50 breaths per minute. There was generalized edema involving his face, abdomen, presacral area, hands, and legs. Eye grounds

Inhalation of 8 per cent oxygen produced pulmonary hypertension in only 13 of 22 dogs anesthetized with pentobarbital. Conversely, each of the dogs anesthetized with a mixture of droperidol and fentanyl developed hypoxic pulmonary hypertension (p = 0.0055), with an increased in the average mean pulmonary artery pressure from 9.7 ± 0.55 (S.E.) to 13.2 ± 0.77 mm. Hg. The average calculated pulmonary arteriolar resistance increased from 280 to 353 dynes-sec.-cm. −5 without significant change in the pulmonary arterial wedge pressure. This analgesic-neuroleptic combination provides satisfactory anesthesia for studies of hypoxic pulmonary hypertension in dogs.