RESUMO
INTRODUCTION: Left ventricular (LV) end-systolic elastance (Ees) can be estimated using single-beat (Ees(sb)) Chen method, employing systolic and diastolic arm-cuff pressures, stroke volume (SV), ejection fraction and estimated normalized ventricular elastance at arterial end-diastole. This work aims to conduct a sensitivity analysis of Chen formula to verify its reliability and applicability in clinical scenario. METHODS: Starting from a baseline condition, we evaluated the sensitivity of Ees(sb) to the parameters contained in the formula. Moreover, a mathematical model of the cardiovascular system was used to evaluate the sensitivity of Ees(sb) to end-diastolic LV elastance (Eed), Ees, arterial systemic resistance (Ras) and heart rate (HR). RESULTS: In accordance with Ees definition, Ees(sb) increases by increasing aortic pressure and pre-ejection time, reaching the highest value for a pre-ejection time = 40 ms, and then decreases. In contrast with Ees definition, Ees(sb) increases (from 3.21 mmHg/mL to 12.15 mmHg/mL) by increasing the LV end-systolic volume and decreases by increasing the SV. In the majority of the analysis with the mathematical model, Ees was underestimated using the Chen method: by increasing Ees (from 0.5 to 2.5 mmHg/mL), Ees(sb) passes only from 0.56 to 1.54 mmHg/mL. Ees(sb) increases for higher Eed (from 1.03 to 2.33 mmHg/mL). Finally, Ees(sb) decreases (increases) for HR < 50 bpm (< 50 bpm), and for Ras < 1100 mmHg/gcm4 (> 1100 mmHg/gcm4). CONCLUSION: Unexpectedly Ees(sb) increases for higher LV end-systolic volume and decreases for higher SV. These results contrast with Ees definition, which is the ratio between the LV end-systolic pressure and the LV end-systolic volume. Moreover, Ees(sb) is influenced by cardiocirculatory parameters such as LV Eed, HR, Ras, ejection time, and pre-ejection time. Finally, Ees(sb) computed with the model output often underestimates model Ees.
Assuntos
Ventrículos do Coração , Função Ventricular Esquerda , Reprodutibilidade dos Testes , Volume Sistólico , Sístole , Função Ventricular Esquerda/fisiologiaRESUMO
The Alpha Magnetic Spectrometer (AMS01), a high-sensitivity particle spectrometer, was successfully flown for 10 d in June 1998 (STS91) in the orbit of the International Space Station (51.7 degrees, -380 km). A high-statistics dataset of galactic cosmic rays were measured as a function of geomagnetic latitude, including the primary protons, leptons and helium as well as the trapped and quasi-trapped proton and lepton components. In this paper, the absorbed dose rate owing to the protons, leptons and helium are presented and compared with measurements made by other instruments flown on the same mission.
Assuntos
Radiação Cósmica , Partículas Elementares , Hélio/análise , Modelos Biológicos , Monitoramento de Radiação/métodos , Voo Espacial , Análise Espectral/métodos , Carga Corporal (Radioterapia) , Simulação por Computador , Prótons , Doses de Radiação , Eficiência Biológica RelativaRESUMO
Hospitalization of patients with heart failure is often caused by poor adherence to drug therapy, by suboptimal utilization of ACE inhibitors and beta-blockers, and by the lack of systematic monitoring of patients after discharge. The aim of the study is to verify the impact of an outpatient management program on the hospitalization rate and functional status of patients with chronic heart failure. Over a five-year period, 435 patients entered our outpatient management program, which includes adjustment in medical therapy, patient education and visits timed according to the patient's status. Fifty-six percent of the patients were in New York Heart functional class I-II; 74% were male; mean age was 62 +/- 11 years. Heart failure was due to coronary heart disease in 42%, dilated cardiomyopathy in 35%, hypertensive heart disease in 13%, other etiologies in 10%. The following changes in medical therapy were made compared to the period before referral: ACE inhibitors in 88% of the patients vs 70% (p < 0.05), mean dose of enalapril and captopril respectively 18 +/- 6 mg vs 11 +/- 4 mg (p < 0.05) and 89 +/- 28 mg vs 61 +/- 34 mg (p < 0.05); digoxin in 71 vs 70% (NS); furosemide in 90 vs 87%; beta-blockers in 16 vs 6% (p < 0.05); amiodarone in 24 vs 16% (p < 0.05); oral anticoagulants in 22 vs 12% (p < 0.05); calcium channel blockers in 10 vs 16% (p < 0.05). During the follow-up period (35 +/- 11 months), there were 111 hospital admissions compared to 518 during the year before recruitment (p < 0.05). Seventy-two patients died (65 for cardiac causes) and four patients underwent cardiac transplantation. Functional status improved (301 patients in I-II functional class and 56 in III-IV after referral compared to 225 and 132 before referral, respectively). Our results were obtained through adjustment in pharmacological therapy, intensive patient education and therapeutic continuity made possible by our outpatient heart-failure clinic organization. It is likely that the increase in costs due to therapeutic adjustment and to the increase in the number of visits is counterbalanced by the reduced rate of hospital admissions.