Observation of Quasichanneling Oscillations.

We report on the first experimental observations of quasichanneling oscillations, recently seen in simulations and described theoretically. Although above-barrier particles penetrating a single crystal are generally seen as behaving almost as in an amorphous substance, distinct oscillation peaks nevertheless appear for particles in that category. The quasichanneling oscillations were observed at SLAC National Accelerator Laboratory by aiming 20.35 GeV positrons and electrons at a thin silicon crystal bent to a radius of R=0.15 m, exploiting the quasimosaic effect. For electrons, two relatively faint quasichanneling peaks were observed, while for positrons, seven quasichanneling peaks were clearly identified.

Observation of deflection of a beam of multi-GeV electrons by a thin crystal.

We report on an experiment performing channeling and volume reflection of a high-energy electron beam using a quasimosaic, bent silicon (111) crystal at the End Station A Test Beam at SLAC. The experiment uses beams of 3.35 and 6.3 GeV. In the channeling orientation, deflections of the beam of 400 µrad for both energies with about 22% efficiency are observed, while in the volume-reflection orientation, deflection of the beam by 120 µrad at 3.35 GeV and by 80 µrad at 6.3 GeV is observed with 86%-95% efficiency. Quantitative measurements of the channeling efficiency, surface transmission, and dechanneling length are taken. These are the first quantitative measurements of channeling and volume reflection using a primary beam of multi-GeV electrons.

The demonstration of alternating contractile state in pulsus alternans.

Pulsus alternans was induced in 11 anesthetized, open-chest dogs by rapid atrial pacing, and the left ventricular filling characteristics and length-tension-velocity relationship of alternating beats were compared. The end-diastolic circumferences (cire) of the strong beats were slightly, but significantly, increased over the weak beats (7.3 > 6.9 cm, P < 0.01), confirming that diastolic filling does alternate in pulsus alternans. This alternation in initial fiber length seemed to result from an alternation in the prior end-systolic length, rather than from an alternation in diastolic filling time or compliance. There was also no difference in end-diastolic tension as measured by an isometric strain gauge suggesting no difference in contractile element relaxation before weak and strong beats. THE CONTRACTILE STATE OF THE STRONG BEATS WAS CONSISTENTLY GREATER THAN THAT OF THE WEAK BEATS WHEN CONTRACTILITY WAS DEFINED IN TERMS OF: (a) V(max) (3.13 > 2.53 circ/sec, P < 0.01); and (b) the velocity of circumferential fiber shortening (0.84 > 0.39 circ/sec, P < 0.001) and developed tension (82.5 > 74 g/cm, P < 0.01) at isolength. The length-tension-velocity relationship of the left ventricle also varied between strong and weak beats when: (a) the maximum velocity of contractile element shortening at least common tension (1.68 > 1.28 circ/sec, P < 0.05); and (b) the velocity of circumferential fiber shortening (0.81 > 0.39 circ/sec, P < 0.001) at maximum developed tension were examined. Analysis of the length-tension-velocity characteristics of sequential beats at the onset of alternans in three dogs suggests that an alternation in contractility initiates alternans, with secondary alternations in ventricular filling. Cross-clamping of the aorta in three other dogs essentially eliminated the alternating changes in end-diastolic length and pressure, while the resultant isovolumic contractions continued to demonstrate clear evidence of pulsus alternans in the ventricular systolic pressure, suggesting the persistance of an alternating contractile state. The evidence suggests that an important mechanism in the production and propagation of pulsus alternans, as produced in the intact canine ventricle by rapid pacing, is a beat-to-beat alternation in contractile state with secondary alternations in ventricular filling.

Emergency percutaneous transluminal coronary angioplasty in acute myocardial infarction: a 3 year experience.

In 151 patients experiencing acute myocardial infarction, emergency coronary angioplasty was performed as primary therapy. Overall, angioplasty was successful in 132 patients (87%); it was successful in 91 (85%) of 107 patients with a totally occluded infarct-related artery and in 41 (93%) of 44 patients with a subtotally occluded infarct-related artery. After successful angioplasty, mean residual stenosis was 29% (range 0 to 70). Eighteen patients were in cardiogenic shock (12%) including four patients receiving cardiopulmonary resuscitation during the angioplasty procedure. Hospital mortality was 9%, with 7 of 13 deaths occurring in patients presenting with cardiogenic shock or intractable ventricular arrhythmia. Hospital mortality was 5% in patients with successful angioplasty versus 37% in those with unsuccessful angioplasty (p less than 0.001). In the immediate period after angioplasty, left ventricular ejection fraction was significantly lower for patients with lesions of the left anterior descending artery (34 +/- 10%) than for patients with lesions of the left circumflex or right coronary artery (43 +/- 11%). In patients with successful angioplasty, significant improvement in left ventricular ejection fraction averaged 13 +/- 12% (p less than 0.001) for those with lesions of the left anterior descending artery and 10 +/- 12% (p less than 0.001) for those with lesions of the left circumflex or right coronary artery. Repeat coronary angiography was performed in 85 (70%) of 121 patients who had successful angioplasty and survived hospitalization without requiring bypass surgery; restenosis was found in 26 (31%), and angioplasty was repeated in 22 patients, successfully in each.(ABSTRACT TRUNCATED AT 250 WORDS)

Early diastolic sound associated with mitral valve prolapse.

A patient with the prolapsing mitral valve syndrome demonstrated a most striking early diastolic sound. Noninvasive study with phonocardiograms, external pulse recordings, and echocardiograms lead us to believe that the sound may be related to the initial opening movement of the mitral valve. To our knowledge, such a mechanism for the production of a diastolic sound has not been previously reported.

Normalization of abnormal T waves in ischemia.

Inverted T waves due to coronary artery disease and previous myocardial infarction were observed to revert ot normal, upright position during ischemia in 38 patients. The normalization of inverted T waves was seen on the electroencephalograms of 19 patients during spontaneously occurring angina pectoris and of 11 patients when ischemia was provoked by treadmill exercise; for 8 patients, normalization occurred during the administration of isoproterenol hydrochloride and during the consequent episode of angina pectoris. The mechanism for normalization may be the algebraic sum of the extent of ST segment elevation and the amplitude of the T waves of acute ischemia plus the extent of preexisting ST segment depression and the degree of T wave inversion, to result in isoelectric ST segment and upright T wave. As with myocardial infarction, reciprocal changes may also be recorded. However, the reciprocal nature may be masked since either acute ST segment elevation of T wave inversion, or both, may not be recorded in the leads reflecting the ischemic area because of normalization.

Reversal of digitalis-induced mesenteric vasospasm by sodium nitroprusside.

Digitalis constricts the peripheral vasculature. When digitalis is administered to patients whose mesenteric blood flow is reduced secondary to heart failure, the vasoconstrictor action coupled to reduced mesenteric flow may result in mesenteric ischemia or hemorrhagic bowel necrosis. The clinical syndrome of mesenteric ischemia secondary to heart failure and excess digitalis developed in a patient. Splanchnic vasoconstriction was proved angiographically. Both the vasospasm and clinical evidence of mesenteric ischemia were promptly reversed by sodium nitroprusside.

Left atrial myxoma infected with Histoplasma capsulatum.

A patient is presented in whom a left atrial myxoma was found to be infected with Histoplasma capsulatum. Histoplasmosis has not been previously associated with this tumor, nor has any fungus without preceding bacterial endocarditis and long-term antibiotic therapy. The clinical course in foru previously reported cases of bacterially infected myxoma is reviewed. There have been 18 prior cases of Histoplasma endocarditis and in two the patients have survived. Their clinical presentation and response to therapy are also reviewed, and pertinent therapeutic conclusions drawn. The role of echocardiography in this patient's evaluation and the ultimate successful therapy are discussed.

Dissociation of the inotropic effect of digitalis from its effect on atrioventricular conduction.

The relation between sequential changes in left ventricular contractility and atrioventricular (A-V) nodal conduction and refractoriness was assessed in open chest dogs during intravenous administration of acetylstrophanthidin (5 mug/kg) at 5 minute intervals until toxic arrhythmias developed. At each time interval, high fidelity left ventricular pressure, its electronic derivative (dP/dt) and a His bundle electrogram were simultaneously recorded and the A-V nodal refractory period was measured by graded trains of stimuli. Animals were studied with an intact autonomic state (Group I), with pharmacologic blockade of both the beta adrenergic and parasympathetic system (Group II) and with parasympathetic blockade (Group III). Whereas contractility increased in response to small doses of digitalis, displaying a linear dose-response relation independent of autonomic tone, A-V nodal transmission indexes responded minimally to less than 50 percent of the toxic dose of digitalis, and the response was dependent upon autonomic tone. These results indicate a dissociation between the effects of digitalis on contractility and A-V transmission in that the major drug action on the ventricular contractile mechanism is a direct, linear one in contrast to the nonlinear response of A-V nodal transmission, which is predominantly mediated through the autonomic system. Clinically, these observations imply that the optimal dose and serum level of digitalis required to treat congestive heart failure may differ significantly from those required to treat supraventricular tachycardias, the therapeutic response of the latter being largely determined by the underlying autonomic tone.

Treatment of recurrent ventricular tachycardia and fibrillation with aprindine.

Twenty-three patients with recurrent ventricular tachycardia or ventricular fibrillation, or both, were treated with aprindine, a new antiarrhythmic agent. It was found that: (1) no patient had a recurrence of ventricular fibrillation after aprindine therapy was begun, except as a terminal event subsequent to the development of acute myocardial infarction and cardiogenic shock or refractory congestive heart failure; (2) 6 patients experienced ventricular tachycardia after the loading dose, but with continued aprindine therapy the ventricular tachycardia was suppressed in 3 of these 6 patients, and a fourth patient was asymptomatic during brief paroxysms of ventricular tachycardia; (3) in 2 patients, aprindine was ineffective and was discontinued; (4) electrical cardioversion was not required in any patient receiving aprindine; (5) premature ventricular extrasystoles were decreased in 18 of the 23 patients treated with aprindine; (6) aprindine was discontinued in 1 patient because of intolerable side effects, although ventricular arrhythmias were suppressed in this patient; and (7) 5 patients died from acute myocardial infarction or severe heart failure while receiving aprindine.

Pacemaker-induced endocardial friction rub.

Two patients had a typical sounding cardiac friction rub after placement of a temporary transvenous pacemaker. Absence of myocardial perforation was documented in one patient during thoracotomy for placement of an epicardial electrode and in the other with an electrogram recorded from the pacemaker as it was being withdrawn. The rubs disappeared during pacemaker removal. These cases are believed to represent endocardial friction rubs resulting from contact of the pacing wire with the endocardium.

Noninvasive documentation of Prinzmetal's angina.

A 57 year old women with substernal nonexertional chest pain and angiographically patent coronary arteries was evaluated with two dimensional echocardiography and myocardial perfusion scintigraphy after provocation of pain with methacholine. Simultaneous with the development of angina pectoris, the electrocardiogram demonstrated S-T segment elevation in leads II, III and aVF, followed by atrioventricular block. The echocardiogram revealed akinesia of the previously normally contracting left ventricular posterior wall during pain followed by hyperkinesia after the administration of nitroglycerin. Perfusion imaging suggested reversible inferior wall hypoperfusion. Thus, these studies provided noninvasive documentation of segmental left ventricular dysfunction and hypoperfusion during variant angina.

An unusual precordial pulse and sound assoicated with large pericardial effusion.

An unusual, high-pitched, early diastolic sound coinciding with a prominent, sharp precordial pulse was observed in a patient with a large chronic pericardial effusion. The pulse and sound coincided exactly with the anterior excursion of the heart within the fluid-filled pericardial sac, suggesting that the sound and pulse result from the ballistic effect of the heart striking the anterior pericardium and chest wall. This finding may be specific for large pericardial effusion with a "swinging heart."