The systolic expansion of the left auricle in mitral disease

670 THE

AMEKIC:lN HEAKT JOUKNX FAST SELF-SUSTAINED ACTIVITY OF MAMMALIAN AUKlCULAR MUSCLE.-A. ROSENWUETH, M.D., ;\ND J. GAKC~.\ RL\~os, M.D., MEXICO D.F., MIXICO.

In isolated auricular appendices, fast nonstimulated discharges follow rapid The frestimulation after acetylcholine or carbaminoylcholine are administered. quency is related to that of the stimuli. Below a critical frequency of stimulation (approximately 20 per second), no automatic discharges ensue. The activity requires the presence of the choline ester. There are more discharges with larger than with smaller doses. Further injections during an episode prolong it. It is longer when acetylcholine is administered after Prostigmine, and longer for carbaminoylcholine than for acetylcholine. Atropine abolishes the phenomenon; curare does not. The discharges end suddenly. The terminal frequency (about 20 per second) is lower than the refractory period requires, for after activity ceases, The activity stimulation elicits faster discharges, whrch may outlast the stimuli. is usually regular, but may become irregular, as if successive impulses started at different points or several regions were discharging independently. It is probably not maintained by a circus movement; it persists in an area smaller than a square centimeter. It differs from the slow type of self-sustained activity both in frequency and in requiring the presence of an acetylcholine-like agent which inhibits the slow activity. NORMAL VALUES OF THE ARTERIAL PRESSURE AND FREQUENCY OF ARTERIAL HYPERTENSION IN HIGH ALTITUDES.--ANDRES ROTTA, M.D., ,~ND ARTEMIO MIRANDA, M.D., LIM.~, PEW. In a town of about 7,000 inhabitants and at 13,850 feet above sea level (Morococha, Peru), an investigation was conducted to detect cases of arterial hypertension. At the same time the blood pressure of 1,878 healthy individuals between 18 and 71 \-ears of age was measured. Among this group there were fifty-three Caucasians (North Americans, Italians, Spaniards, and Peruvians), dwellers of high altitudes for many years; the rest were native Indians. The following results were found: 1. Neither in the investigation nor in the direct examinations were cases of arterial hl-pertension found. 2. The systolic arterial pressure is lower in men at high altitudes than in those at sea level, (mean pressure, 108 mm. Hg); the diastolic arterial pressure is higher than at sea level, (mean pressure, 88 mm. Hg). 3. Since the few nonIndians showed no difference from the natives, either in the systolic or in the diastolic pressure, it may be concluded that the figures obtained have nothing to do with the racial characteristics and that chronic anoxia does not influence arterial pressure. THE

SYSTOLIC DISEASE.-D. FRANCE.

EXPANSlON ROUTIER,

OF THE LEFT AURICLE M.D., AND R. HEIM DE BAISC,

IN MITRAL M.D., PAWS,

The radiologic examination of patients with mitral disease permits recognition in the most advanced cases of an expansion of the left auricular contour during ventricular systole. Radiokymography gives more precise information regarding this phenomenon, which can be observed either in the anteroposterior position when the left auricle extends to the right border of the heart, or in the right anterior oblique, left lateral, or left posterior oblique position, when the tilled esophagus follows the auricular outline closely. A description is given of the radiokymogram and of the expansion observed. Interpretation: The left auricular distension during ventricular systole is evidence of auriculoventri-

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cular regurgitation or “mitral insufficiency” ; thus this physiopathological dixturbance can be easily demonstrated during life. Our radiological-clinical st MI\ of the phenomenon is based upon several hundred observations. Left auricular systolic expansion becomes more marked with marked enlargement of the left auricle and in the presence of auricular tibrillation; the mot-r. advanced the cardiac lesion, the more marked is the systolic espansion of the Iefl auricle. The auricular expansion may or ma!- not be present \vith stenosi> or an apical systolic murmur of mitral insufficient!,. The different possihilitir%c‘an be explained by the volume of regurgitating blood, If rcgurgitatiori i5 slight it ma;. set into vibration the mitral apparatus and produce a murmur I)ut ma). be msufticient to distend the auricle. On the contrar!-, if it is market1 it ma\’ distend the auricle without causing a vibration of ;t mitral apparat USnhic-11 is more or less rigid, thickened and gapping. The left auricular systolic expansion not onl?; establishes the tliagl~osis OI mitral insufficiency, but permits appreciation of the importance of that regurgitation. Thus, it is a sign of considerable importance both ph!-siopathologi(.al~~ ;ITIC I clinicall?-.

,As previously reported (Am. J. Med. 4: 228. 1948) elevated diastolic i)ioc~O pressure peaks of 95 mm. or over were found in the majority of 180 hoq)italizvtl patients injured by the Texas City explosions of ,\pril 16. 1947. This inciclenc~e of acute hypertension, occurring especially from two to twenty-eight hours following the blasts, is much higher than that found in hospitalizctl suqicd patients or in various battle zones during World War I I. Some four to seven months following the explosions, 111 cases \verc: I.(‘examined for signs of cardiovascular disease. It appeared that 23 per cent of the casesshowed diastolic blood pressures of 95 mm. or over, even thouah the iow(.st While statist&II!vaiirl readings obtained following rest were so evaluated. comparable figures for the local general population are not available, the figurt of 23 per cent was found to be statistically higher than the available figure cirlw of industrial examinees or of insurance applicants. Cold pressor tests were positive in 72 per cent of the postexplosion y’ol.~l) and in 77 per cent of the follow-up group of blast victims. In addition to the finding of hypertension as a possible result of the blast, we saw a case of severe hypertensive reaction following massive pulmonar!, embolism. Some casesof ,possible cardiac blast injuries, proved pathologic.;\ll!-, were also encountered. Complete studies, includincr electrocardiographic anti other examinations, throw some light upon the poss’ibleetiology of the c,;~rcliovascular abnormalities.

THE EFFECT OF VASOCONSTRICTIVE AKD HYPEKVOI~FChll~‘ II lC.\SURES upois TETRAETHYL L4mw~~Iu~~~ OI~THOST.Z'I‘IC~ ww).TENSlON.-ARTHUR RUSKIN, M.D., GKVESTON, ~T‘Es.w,. \Ve have previously reported a finding of orthostatic hypotension in varil)u* clinical states in which vasodilation seemed to play a prominent part (I’roc. .Irn. Fed. Clin. Res. 3: 44, 1947). Among the conditions previously and recentI\. observed to be associated with orthostatic hypotension of various degrees havca been acute and severe chronic anemias, other blood dyscrasias, hyperth>.roidism, and alcoholism. Both ephedrine and desoxycorticosterone were obser~-tr(l 1~ us to prevent in various degrees the orthostatic phenomona. Tetraeth>-1 ammonium uniformly- produced orthostatic h!-potensiol! i11