RESUMO
NASA's Parker Solar Probe mission1 recently plunged through the inner heliosphere of the Sun to its perihelia, about 24 million kilometres from the Sun. Previous studies farther from the Sun (performed mostly at a distance of 1 astronomical unit) indicate that solar energetic particles are accelerated from a few kiloelectronvolts up to near-relativistic energies via at least two processes: 'impulsive' events, which are usually associated with magnetic reconnection in solar flares and are typically enriched in electrons, helium-3 and heavier ions2, and 'gradual' events3,4, which are typically associated with large coronal-mass-ejection-driven shocks and compressions moving through the corona and inner solar wind and are the dominant source of protons with energies between 1 and 10 megaelectronvolts. However, some events show aspects of both processes and the electron-proton ratio is not bimodally distributed, as would be expected if there were only two possible processes5. These processes have been very difficult to resolve from prior observations, owing to the various transport effects that affect the energetic particle population en route to more distant spacecraft6. Here we report observations of the near-Sun energetic particle radiation environment over the first two orbits of the probe. We find a variety of energetic particle events accelerated both locally and remotely including by corotating interaction regions, impulsive events driven by acceleration near the Sun, and an event related to a coronal mass ejection. We provide direct observations of the energetic particle radiation environment in the region just above the corona of the Sun and directly explore the physics of particle acceleration and transport.
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Two distinct proton populations are observed over Jupiter's southern polar cap: a â¼1 keV core population and â¼1-300 keV dispersive conic population at 6-7 RJ planetocentric distance. We find the 1 keV core protons are likely the seed population for the higher-energy dispersive conics, which are accelerated from a distance of â¼3-5 RJ. Transient wave-particle heating in a "pressure-cooker" process is likely responsible for this proton acceleration. The plasma characteristics and composition during this period show Jupiter's polar-most field lines can be topologically closed, with conjugate magnetic footpoints connected to both hemispheres. Finally, these observations demonstrate energetic protons can be accelerated into Jupiter's magnetotail via wave-particle coupling.
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Measurements of lighter, low-energy charged particles in a laboratory beamline are complicated due to the influence of Earth's magnetic field. Rather than nulling out the Earth's magnetic field over the entire facility, we present a new way to correct particle trajectories using much more spatially limited Helmholtz coils. This approach is versatile and easy to incorporate in a wide range of facilities, including the existing ones, enabling measurements of low-energy charged particles in a laboratory beamline.
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We present a review of Anomalous Cosmic Rays (ACRs), including the history of their discovery and recent insights into their acceleration and transport in the heliosphere. We focus on a few selected topics including a discussion of mechanisms of their acceleration, escape from the heliosphere, their effects on the dynamics of the heliosheath, transport in the inner heliosphere, and their solar cycle dependence. A discussion concerning their name is also presented towards the end of the review. We note that much is known about ACRs and perhaps the term Anomalous Cosmic Ray is not particularly descriptive to a non specialist. We suggest that the more-general term: "Heliospheric Energetic Particles", which is more descriptive, for which ACRs and other energetic particle species of heliospheric origin are subsets, might be more appropriate.
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In seven chronically instrumented conscious dogs, micromanometers measured left ventricular pressure, and ultrasonic dimension transducers measured left ventricular minor-axis diameter; the latter recording was filtered to examine data between 20 and 100 Hz. Acceptable external heart sounds were recorded with a phonocardiographic microphone in four of the seven dogs. With each dog sedated, intubated and mechanically ventilated, data were obtained during hemodynamic alterations produced by volume loading, phenylephrine, calcium infusion and vena caval occlusion. Damped oscillations were noted consistently in the left ventricular diameter waveform toward the end of rapid ventricular filling. These wall vibrations, assessed by the filtered diameter, correlated well with the third heart sound (S3) on the phonocardiogram. The peak frequency of the wall vibrations increased with increased diastolic pressure (p = 0.004), probably reflecting an increase in myocardial wall stiffness. In contrast, the amplitude of the vibrations varied directly with left ventricular filling rate (p = 0.0001). Thus, S3 seemed to be related specifically to ventricular wall vibrations during rapid filling, and the spectra of the amplitude-frequency relation shifted toward the audible range with increases in diastolic pressure, wall stiffness or filling rate. Spectral analysis of S3 may be useful in assessing pathologic changes in myocardial wall properties.
Assuntos
Ruídos Cardíacos/fisiologia , Função Ventricular/fisiologia , Animais , Cães , Análise de Fourier , Manometria , Contração Miocárdica/fisiologia , FonocardiografiaRESUMO
To assess the value of intraoperative transesophageal echocardiography during cardiac valve surgery, 154 consecutive patients who had a valve operation in conjunction with pre- and postcardiopulmonary bypass transesophageal imaging were studied. Prebypass imaging yielded unsuspected findings that either assisted or changed the planned operation in 29 (19%) of the 154 patients. Imaging immediately after bypass revealed unsatisfactory operative results that necessitated immediate further surgery in 10 (6%) of the 154 patients. Postbypass left ventricular dysfunction, prompting administration of inotropic agents, was identified in 13 patients (8%). Transesophageal echocardiography proved most useful when both two-dimensional and Doppler color flow imaging were employed in patients undergoing a mitral valve operation, where surgical decisions based on echocardiographic results were made in 26 (41%) of 64 cases. Postbypass echocardiographic findings identified patients at risk for an adverse postoperative outcome. Of 123 patients whose postbypass valve function was judged to be satisfactory, 18 (15%) had a major postoperative complication and 6 (5%) died, whereas of 7 patients with moderate residual valve dysfunction, 6 (86%) had a postoperative complication and 3 (43%) died (p less than 0.05 for both). Likewise, of 131 patients with preserved postbypass left ventricular function, 12 (9%) had a major complication and 7 (5%) died, whereas of 23 patients with reduced ventricular function, 17 (73%) had a postoperative complication and 6 (26%) died (p less than 0.05 for both). These data indicate that intraoperative transesophageal echocardiography is useful in formulating the surgical plan, assessing immediate operative results and identifying patients with unsatisfactory results who are at increased risk for postoperative complications.
Assuntos
Ecocardiografia Doppler/métodos , Valvas Cardíacas/cirurgia , Ponte Cardiopulmonar , Ecocardiografia Doppler/normas , Esôfago , Feminino , Seguimentos , Valvas Cardíacas/fisiopatologia , Humanos , Período Intraoperatório , Masculino , Valva Mitral/cirurgia , Complicações Pós-OperatóriasRESUMO
The end-systolic pressure-volume relation, the relation between stroke work and end-diastolic volume, termed the preload recruitable stroke work relation, and the relation between the peak of the first derivative of left ventricular pressure (dP/dtmax) and end-diastolic volume have been employed as linear indexes of left ventricular contractile performance in laboratory animals. The purpose of this study was to examine the relative utility of these indexes during routine cardiac catheterization in seven human subjects (mean age 48 +/- 18 [SD] years) with a normal left ventriculogram and coronary angiogram. Left ventricular pressure was recorded continuously with a micromanometer catheter, and left ventricular volume was derived from digital subtraction contrast ventriculograms obtained at 30-ms intervals. Transient occlusion of the inferior vena cava with a balloon-tipped catheter was employed to obtain beat to beat reductions in left ventricular pressure and volume over 8.7 +/- 1.7 cardiac cycles. Stroke work declined by 49 +/- 13% during vena caval occlusion, but end-systolic pressure fell by only 26 +/- 11%, and changes in dP/dtmax were small and inconsistent (12 +/- 22%). Consequently, the range of data available for determination of the preload recruitable stroke work relation greatly exceeded that for the end-systolic pressure-volume relation and the dP/dtmax-end-diastolic volume relation, and much less linear extrapolation from the measured data was required to determine the volume-axis intercept. Preload recruitable stroke work relations were highly linear (r = 0.95 +/- 0.07), and much more so than end-systolic pressure-volume relations (r = 0.79 +/- 0.23).(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Cateterismo Cardíaco , Contração Miocárdica/fisiologia , Volume Sistólico/fisiologia , Função Ventricular Esquerda/fisiologia , Angiografia Digital , Angiografia Coronária , Feminino , Coração/diagnóstico por imagem , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Since abnormalities in regional myocardial function and nucleotide metabolism persist for a prolonged period after a brief coronary occlusion the temporal relation between the resolution of myocardial dysfunction and repletion of nucleotide pools in postischaemic myocardium was studied in conscious mildly sedated animals. In a second experiment 5-amino-4-imidazolecarboxamide riboside (AICAriboside) was infused in an attempt to influence myocardial function by altering the rate of adenine nucleotide synthesis. Conscious dogs mildly sedated with morphine underwent coronary occlusion for 15 min followed by reperfusion for 30 min or 12 h, at which time a myocardial sample was obtained for nucleotide analysis. Segment shortening averaged 62% of control values at 15 min of reperfusion and increased to 81% of control by 12 h of reperfusion (p less than 0.05). Adenine nucleotide content was 75(5)% of control after 30 min of reperfusion and did not change significantly over the next 12 h of reperfusion. Thus the early return of systolic function was not accompanied by a detectable increase in total adenine nucleotide content. In the second experiment a pronounced stimulation of the proximal purine nucleotide synthetic pathway occurred as evidenced by a 13-fold to 25-fold increase in inosine monophosphate content. One branch of the distal purine pathway was also stimulated as evidenced by complete repletion of guanine nucleotide pools, but the product of the other branch (adenine nucleotides) did not increase significantly. These results indicate a selective limitation of the distal adenine nucleotide synthetic pathway in postischaemic myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)
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Doença das Coronárias/fisiopatologia , Coração/fisiopatologia , Nucleotídeos de Purina/metabolismo , Aminoimidazol Carboxamida/análogos & derivados , Aminoimidazol Carboxamida/metabolismo , Animais , Cães , Hemodinâmica/efeitos dos fármacos , Miocárdio/metabolismo , Nucleotídeos/metabolismo , Fosfocreatina/metabolismo , Ribonucleosídeos/metabolismoRESUMO
Urinary excretions of progesterone (P) during normal menstrual cycle have been measured by radioimmunoassay. The excretion pattern mimics that of plasma P. Measurements of P in a single voided urine may be a reliable substitute for plasma analyses in the evaluation of ovulation and corpus luteal function.
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Corpo Lúteo/fisiologia , Menstruação , Ovulação , Progesterona/urina , Feminino , HumanosRESUMO
Chronic left ventricular-atrial regurgitation (LVAR) was created in 8 dogs by means of an external conduit so that the effects of acute correction of regurgitation on the mechanics of left ventricular performance could be studied in detail. LVAR of 46 to 77 per cent of the total left ventricular (LV) output was associated with a depression of the LV inotropic state (downward displacement of the stress-velocity relationship, reduction in V max), reduced forward flow, and signs of cardiac failure. Acute occlusion of the shunt (analogous to return of mitral valvular competence) in the anesthetized, open-chest animal resulted in a statistically significant increase in the integrated LV systolic wall stress (afterload), which averaged 18 per cent. In the dog with greatest depression of the LV inotropic state, the increase in afterload was associated with a decrease in forward flow. Occlusion of the shunt had no significant effect on the inotropic state. This model of mitral regurgitation appears to be useful in assessing the effect of chronic LVAR on cardiac performance and may explain the hemodynamic deterioration observed in some patients with severe mitral regurgitation following valve replacement.
Assuntos
Débito Cardíaco , Ventrículos do Coração/fisiopatologia , Insuficiência da Valva Mitral/fisiopatologia , Animais , Modelos Animais de Doenças , Cães , Insuficiência Cardíaca/etiologia , Insuficiência da Valva Mitral/complicações , Insuficiência da Valva Mitral/cirurgia , Contração MiocárdicaRESUMO
Dopamine frequently is used to improve cardiac performance after acute myocardial ischemia. Inotropic agents, however, increase myocardial oxygen demand and could potentially delay recovery from ischemic injury. To evaluate this problem, we studied eight chronically instrumented dogs in the conscious state and performed two 15-minute coronary occlusions 48 hours apart. After one of the occlusions, either dopamine (15 micrograms/kg/min) or saline placebo was administered intravenously from 1.0 to 1.5 hours of reperfusion. The alternative infusion was given during the second study. Preload recruitable work area, the area beneath the stroke work versus end-diastolic length relationship, was used to assess intrinsic myocardial performance. Ischemia decreased preload recruitable work area to 13% of control after both occlusions. After reperfusion, a 30-minute dopamine infusion acutely increased myocardial function nearly threefold as compared with placebo. Myocardial performance after dopamine administration, however, was significantly depressed compared with placebo throughout the remaining 24 hours of reperfusion (p less than 0.01). These data indicate that dopamine may impair functional recovery after ischemic myocardial injury and suggest that inotropic interventions should be used in this setting only when absolutely indicated.
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Doença das Coronárias/fisiopatologia , Dopamina/farmacologia , Coração/efeitos dos fármacos , Animais , Circulação Coronária , Cães , Eletrocardiografia , Coração/fisiopatologia , Frequência Cardíaca/efeitos dos fármacos , Contração Miocárdica/efeitos dos fármacos , Traumatismo por Reperfusão Miocárdica/fisiopatologia , Volume Sistólico/efeitos dos fármacosRESUMO
Of all patients with acute evolving myocardial infarction treated surgically at Duke University Medical Center between 1984 and 1986, 27 patients given high doses (greater than 1.5 million units) of streptokinase preoperatively were studied. Eleven patients who received streptokinase had coronary bypass grafting 12 hours after thrombolytic therapy (early hours), eight patients between 12 and 72 hours (delayed), and eight patients beyond 72 hours (late hours). Seventeen patients who underwent coronary bypass grafting within 6 hours of the onset of symptoms, without preoperative streptokinase, were included as control patients. Only the patients having early operation had significantly greater postoperative blood loss; postoperative use of red blood cells; fresh-frozen plasma; cryoprecipitate; prolonged postoperative prothrombin time; and prolonged partial thromboplastin time. Patients having delayed or late operations did not differ significantly from patients not receiving streptokinase. Only the interval between time of streptokinase administration and operation could account for the coagulopathy and the postoperative bleeding complications in the early group. Patients in the early group had a higher in-hospital mortality (27% versus 6% for the non-streptokinase group) and major noncardiac morbidity (36% versus 12% for the non-streptokinase group). Patients in the delayed and late groups had minimal postoperative complications and no mortality. Observations were not explained by differences in total ischemic time, number of angioplasty failures, or number of patients with cardiogenic shock between the early group and the non-streptokinase group. Postoperative bleeding and massive use of blood products seemed to be contributory factors: Two of three deaths in the patients having early operations were associated with clinical suspicion of tamponade. Patients undergoing coronary bypass grafting within 12 hours of streptokinase therapy appear to be a high-risk group in a more emergent, uncontrolled clinical setting and require aggressive monitoring and correction of coagulopathy.
Assuntos
Ponte de Artéria Coronária , Hemorragia/epidemiologia , Complicações Pós-Operatórias/epidemiologia , Cuidados Pré-Operatórios , Estreptoquinase/uso terapêutico , Transtornos da Coagulação Sanguínea/epidemiologia , Transtornos da Coagulação Sanguínea/etiologia , Transtornos da Coagulação Sanguínea/prevenção & controle , Ponte Cardiopulmonar , Emergências , Hemorragia/etiologia , Hemorragia/prevenção & controle , Humanos , Infarto do Miocárdio/complicações , Infarto do Miocárdio/tratamento farmacológico , Infarto do Miocárdio/mortalidade , Infarto do Miocárdio/cirurgia , Complicações Pós-Operatórias/etiologia , Complicações Pós-Operatórias/prevenção & controle , Estudos Retrospectivos , Fatores de TempoRESUMO
Although periprosthetic leak is presently uncommon after mitral valve replacement, suture line disruption still occurs and may be significant in some patients. Suture technique is obviously an important factor in preventing disruption, but few authors have examined this variable. The purpose of this study was to determine which of four suture methods for mitral valve replacement maximized prosthetic stability in the mitral anulus. Horizontal mattress sutures with subannular pledgets, horizontal mattress sutures with supra-annular pledgets, figure-of-eight sutures, and interrupted simple sutures were compared. A Carpentier-Edwards sewing ring was sutured to the mitral anulus of intact canine left ventricles, each technique randomly assigned to eight hearts. Suture size, number of bites, and annular depth were maintained constant in all groups. Progressively increasing force was applied across the suture line until disruption occurred. The yield force at initial suture disruption was measured by a semiconductor strain-gauge transducer and defined the experimental end point. Subannular pledget-supported sutures required the greatest force (38.4 +/- 0.8 N) to produce prosthetic dehiscence and were significantly more secure than supra-annular pledgets (32.7 +/- 0.5 N). The two suture techniques in which pledgets were used were better than the nonsupported sutures, the mean yield force averaging 28.3 +/- 0.3 N for figure-of-eight and 21.3 +/- 0.7 N for interrupted simple sutures. Although clinical techniques may vary with prosthetic valve design, surgical preference, or pathological anatomy, this study suggests that horizontal mattress sutures with subannular pledgets provide the best prosthetic valve stability during mitral valve replacement.
Assuntos
Próteses Valvulares Cardíacas , Técnicas de Sutura , Animais , Fenômenos Biomecânicos , Cães , Valva Mitral/cirurgia , Complicações Pós-OperatóriasRESUMO
On the basis of recent investigation, controversy has arisen regarding which of several cardiopulmonary resuscitation methods optimizes hemodynamics. The present study was designed to compare five recently described chest compression techniques: high-impulse manual chest compression at 150/min, mechanical compression at 60/min with simultaneous ventilation, mechanical compression at 60/min with simultaneous ventilation and either systolic or diastolic abdominal compression, and pneumatic vest compression at 60/min. Eight dogs were chronically instrumented with electromagnetic flow probes in the ascending and descending aorta while matched micromanometers measured aortic, left ventricular, and pleural pressures. At study, each dog was anesthetized with morphine, intubated, and the heart was fibrillated by rapid ventricular pacing. The five cardiopulmonary resuscitation methods were performed randomly in each preparation within 7 to 10 minutes of arrest. In four dogs, brachiocephalic blood flow was computed as total cardiac output minus descending aortic blood flow, and in all dogs coronary perfusion pressure was calculated as mean diastolic aortic pressure minus mean diastolic left ventricular pressure. Average cardiac output for seven studies was 662 +/- 61 ml/min with high-impulse manual compression, 340 +/- 46 ml/min with mechanical compression and simultaneous ventilation, 336 +/- 45 ml/min with mechanical compression and simultaneous ventilation with systolic abdominal compression, 366 +/- 52 ml/min with mechanical compression and simultaneous ventilation with diastolic abdominal compression, and 196 +/- 29 ml/min with vest resuscitation (high-impulse manual compression significantly greater than other techniques by multivariate analysis, p less than 0.05). Brachiocephalic blood flow generally followed cardiac output and was statistically the greatest with high-impulse manual compression at 273 +/- 47 ml/min (p less than 0.05). Finally, high-impulse manual compression provided the highest coronary perfusion pressure of 31 +/- 4 mm Hg (p less than 0.05) compared to 23 +/- 2 mm Hg for mechanical compression and simultaneous ventilation, 23 +/- 2 mm Hg for mechanical compression and simultaneous ventilation with systolic abdominal compression, 23 +/- 3 mm Hg for mechanical compression and simultaneous ventilation with diastolic abdominal compression, and 11 +/- 2 mm Hg for vest resuscitation. These data demonstrate that high-impulse manual compression generated physiologically and statistically superior hemodynamics when compared with other methods in this model of cardiopulmonary resuscitation.
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Massagem Cardíaca/métodos , Hemodinâmica , Animais , Débito Cardíaco , Cães , ManometriaRESUMO
Early endotracheal extubation has been shown to be a safe postoperative management option in patients having cardiac operations. However, few objective data exist on the response of ventricular performance to early termination of controlled ventilation. Seven patients undergoing routine elective coronary artery bypass grafting or adult repair of atrial septal defect were studied after intraoperative placement of left ventricular micromanometers, left ventricular minor axis dimension crystals, and left atrial and intrapleural pressure catheters. Physiologic data were recorded intraoperatively, during controlled mandatory ventilation in the intensive care unit, and during spontaneous respiration immediately after extubation. Extubation to spontaneous breathing was associated with a significant decline in intrapleural pressure and significant increases in left ventricular end-diastolic diameter, ejection diameter shortening, stroke work, and cardiac output. The augmented left ventricular diastolic filling seemed to result from the fall in intrapleural pressure and perhaps from normalization of right ventricular afterload. The preload recruitable stroke work relationship showed that myocardial contractility remained constant after extubation, and ventricular function improved primarily because of increased preload associated with shifting of the capacitance blood volume toward the chest. Thus endotracheal extubation enhances cardiac performance after uncomplicated cardiac surgical procedures, and by this mechanism early extubation may be clinically beneficial as a routine adjunct to postoperative care.
Assuntos
Ponte de Artéria Coronária , Intubação Intratraqueal , Contração Miocárdica , Respiração Artificial , Débito Cardíaco , Humanos , Masculino , Pessoa de Meia-Idade , Cuidados Pós-Operatórios , Período Pós-Operatório , Volume Sistólico , Fatores de TempoRESUMO
Adequate coronary blood flow is a major determinant for successful resuscitation from cardiopulmonary arrest. To develop compression techniques that optimize coronary blood flow, we implanted in eight dogs electromagnetic flow probes that measured circumflex coronary blood flow and ascending aortic blood flow. Micromanometers measured left ventricular and aortic pressures. Each dog was anesthetized and intubated, and the heart was fibrillated electrically. High-impulse manual chest compressions were performed with the dog in the supine position, and compression rate was varied from 60/min to 150/min. Antegrade coronary blood flow occurred primarily during artificial diastole, and there was a brief period of retrograde coronary blood flow with compression during artificial systole. Cardiac output and diastolic aortic pressure increased with compression rate, significantly augmenting peak coronary blood flow velocity. However, diastolic perfusion time decreased linearly with compression rate and limited coronary perfusion at rates greater than 120/min. As a result, net coronary blood flow during high-impulse manual chest compression was determined primarily by diastolic aortic pressure and diastolic perfusion time. Coronary blood flow was optimized in this model at a compression rate of 120/min.
Assuntos
Circulação Coronária , Parada Cardíaca/terapia , Massagem Cardíaca , Animais , Cães , Feminino , Hemodinâmica , MasculinoRESUMO
The internal mammary artery has become the coronary bypass graft of choice in recent years because of enhanced long-term patency. Along with this trend, sequential, bilateral, and free mammary grafts have been employed more frequently in an effort to maximize the number of distal internal mammary anastomoses. This approach of maximally using the internal mammary artery (complex mammary grafting) seems logical, but at present little information about patency of the newer types of internal mammary artery grafts is available to justify the more complicated procedures. Over a 15 month period, 207 patients underwent bypass graft angiography from 1 to 32 weeks after operation. This is an 85% restudy rate for a consecutive series of coronary bypass procedures. Patency was defined as complete filling of the graft and distal vessel bypassed. A total of 841 distal vessels were grafted, or 4.1 per patient. The overall patency rate was 91% for 503 distal vein graft anastomoses and 99% for 338 internal mammary artery grafts. Individual patency rates of distal anastomoses, expressed as number patent/total (percent patent), were as follows: simple vein grafts, 262/285 (92%); sequential vein grafts, 196/218 (90%); left internal mammary artery to left anterior descending coronary artery, 109/110 (99%); left internal mammary to circumflex marginal artery, 14/14 (100%); right internal mammary to right coronary artery, 19/20 (95%); right internal mammary to left anterior descending coronary artery, 10/10 (100%); right internal mammary to circumflex marginal artery via transverse sinus, 18/20 (90%); sequential left internal mammary artery to left anterior descending system, 133/134 (99%); sequential left internal mammary to circumflex marginal system, 15/15 (100%); free internal mammary artery, 9/9 (100%); free sequential internal mammary artery, 6/6 (100%). Of the 18 patent transverse sinus right internal mammary grafts to the circumflex marginal artery, three exhibited very slow flow and probably were not functional. The hospital mortality associated with internal mammary revascularizations was 0.4% for nonemergency cases and 3.1% for emergency procedures. On the basis of clinical and postoperative graft patency data, expanded use of more complicated types of mammary grafts seems justified. Function of the right internal mammary graft to the circumflex marginal artery was suboptimal, and this method has been discontinued. All other complex mammary techniques had excellent patency rates as compared to vein grafts, and these differences may become even more significant in the late postoperative period.(ABSTRACT TRUNCATED AT 400 WORDS)
Assuntos
Angiografia Coronária , Doença das Coronárias/cirurgia , Revascularização Miocárdica/métodos , Idoso , Doença das Coronárias/diagnóstico por imagem , Humanos , Revascularização Miocárdica/estatística & dados numéricos , North Carolina , Período Pós-Operatório , Veia Safena/transplante , Grau de Desobstrução VascularRESUMO
Although it is well established that coronary revascularization can reverse exercise-induced ischemic dysfunction, the effects on resting ventricular performance are controversial. From a group of 183 patients receiving surgical therapy for ischemic heart disease, 166 underwent bypass graft arteriography at an average of 7 to 14 days postoperatively. In 149 patients, satisfactory preoperative and postoperative biplane left ventriculograms were obtained. Regional wall motion was assessed by the 100 segment method of Sheehan and Dodge, and a perioperative change in shortening greater than 2 standard deviations of normal variability over 20 or more adjacent segments was considered significant. Ninety-five patients had stable or progressive angina, 88 had medically refractory unstable angina, 155 were in New York Heart Association Class IV, and 37 had a preoperative left ventricular ejection fraction of less than 0.4. Myocardial integrity was preserved with crystalloid cardioplegia and topical hypothermia. Seven hundred ninety-eight bypass grafts were performed (522 vein grafts and 276 mammary artery grafts), and 13 patients had concomitant left ventricular aneurysmectomy. Hospital mortality was 2.2%. The overall early graft patency rate was 95.9% (93.7% for vein grafts and 100% for mammary arteries). Only one patient had a decrement in regional wall motion, and 51 (37%) had significant postoperative improvement (27 in the unstable angina group and 24 in the stable angina group); in the patients with improved regional wall motion, ejection fraction increased by an average of 0.18 (p less than 0.01). Ejection fraction also improved after aneurysmectomy, and the increment seemed to result from both a reduction in end-diastolic volume and improved regional wall motion. Thus, reversible ischemic myocardial dysfunction appears to be common in the general population of patients undergoing coronary artery bypass grafting; 40% of patients with unstable angina and 34% of those with stable angina can be expected to have improved regional wall motion after successful revascularization. Finally, ventricular aneurysm resection significantly enhances left ventricular performance as assessed by ventriculographic ejection fraction.
Assuntos
Doença das Coronárias/cirurgia , Coração/fisiopatologia , Revascularização Miocárdica , Idoso , Doença das Coronárias/fisiopatologia , Feminino , Humanos , Masculino , Contração Miocárdica , Volume SistólicoRESUMO
Right ventricular failure is a leading cause of death in patients who require the left ventricular assist device. Previous reports suggested right ventricular functional deterioration during left ventricular assist but lacked a method by which right ventricular function could be quantified adequately. This study examined the effects of left ventricular volume unloading on right ventricular systolic function by means of the stroke work/end-diastolic volume relationship, a load-insensitive index of myocardial performance. In 12 anesthetized open-chested dogs, right ventricular and left ventricular pressures were measured with micromanometers while ultrasonic dimension transducers measured left and right ventricular orthogonal diameters. Left ventricular unloading was accomplished with left atrial-to-femoral artery bypass with a centrifugal pump. Data were recorded during transient vena caval occlusion in the control state and with maximal left ventricular unloading by full support by the left ventricular assist device. Modified ellipsoidal geometry was used to calculate simultaneous biventricular volumes, and linear regression analysis of right ventricular stroke work versus end-diastolic volume was used to quantify right ventricular systolic function. Average slope and x intercept of this relationship under control conditions were 2.2 +/- 0.3 X 10(4) erg/ml and 10.7 +/- 5.0 ml, respectively. During full support by the left ventricular assist device (mean flow rate, 2.4 +/- 0.3 L/min), left ventricular end-diastolic volume decreased by 31% (p less than 0.01), left ventricular septal-free wall diameter decreased by 7% (p less than 0.001), and rate of rise of right ventricular peak positive pressure declined by 13% (p less than 0.05). The corresponding slope and x intercept of the right ventricular stroke work/end-diastolic volume relationship during full unloading of left ventricular assist device were 2.3 +/- 0.3 X 0.3 X 10(4) erg/ml and 14.3 +/- 4.8 ml, respectively; these values were not significantly different from control values (p greater than 0.5). Additionally, analysis of right ventricular end-diastolic pressure-volume relationships suggested improved right ventricular chamber compliance, although the effects were small and did not reach statistical significance (p = 0.10). These data imply that marked alterations in biventricular geometry accompanying left ventricular volume unloading by the left ventricular assist device in a normal heart do not significantly alter right ventricular performance characteristics.
Assuntos
Coração Auxiliar , Função Ventricular , Animais , Pressão Sanguínea , Cães , Hemodinâmica , Modelos Cardiovasculares , Volume SistólicoRESUMO
To develop a method for quantitative analysis of regional left ventricular function from transesophageal two-dimensional echocardiograms, we conducted studies 10 and 20 minutes after induction of anesthesia in 16 patients with normal hearts who were undergoing minor orthopedic operations. Wall thickening was measured with the centerwall method along 100 chords drawn perpendicular to a line constructed around the center of the ventricular wall, midway between the endocardial and epicardial contours. Thickening, either normalized by the length of the end-diastolic perimeter or expressed as a percentage of the end-diastolic wall thickness at each chord, was compared with measurements of endocardial motion. Wall motion was relatively diminished in the anteroseptal region and enhanced on the contralateral wall, but wall thickening was homogeneous throughout the contour. Normalized wall thickening was significantly less variable (standard deviation/mean, 0.47 +/- 0.13) in the normal population than were either percent wall thickening (0.53 +/- 0.012) or wall motion (0.51 +/- 0.09) (p less than 0.005 for both comparisons). There was no significant change in regional or global function between 10 minutes and 20 minutes after the induction of anesthesia. In summary, normalized wall thickening as a parameter of regional left ventricular function is more homogeneous and less variable in subjects with normal hearts than is endocardial motion because wall thickening measurements are not subject to cardiac translocation artifacts. This low variability suggests that normalized wall thickening measured by the centerwall method may prove particularly useful for intraoperative and postoperative monitoring of regional left ventricular function by transesophageal echocardiography in patients undergoing both cardiac and noncardiac surgical procedures.