RESUMEN
OBJECTIVE: Cardiomyoplasty is a surgical procedure to support the failing heart, in which a burst-stimulated latissimus dorsi muscle flap is transposed and wrapped around the ventricles. The effect of dynamic cardiac compression, implemented as cardiomyoplasty, on left ventricular performance remains controversial; the mechanism by which clinical symptoms are improved remains unclear. To investigate the mechanism for improvement of patients' symptoms, it is important to evaluate the effects of cardiomyoplasty on left ventricular energetics and on left ventricular systolic and diastolic function. We therefore evaluated the efficiency of energy transfer from the native pressure-volume area to external work under conditions of 1:3 skeletal muscle burst pacing in an animal model with chronic heart failure. METHODS: In seven Merino-Wether sheep, cardiomyoplasty was performed after stable heart failure was induced by staged coronary embolizations (ejection fraction < 35%). Hemodynamic assessment including the assessment of the pressure-volume relationship was performed 8 weeks after cardiomyoplasty when the latissimus dorsi muscle was fully trained. Instantaneous left ventricular pressure and volume were measured with a catheter-tipped manometer and a conductance catheter during steady-state conditions and after a transient inferior vena cava occlusion. The effect of dynamic cardiac compression on left ventricular systolic function was assessed by comparing pre-assisted and assisted beats and on diastolic function by comparing assisted and post-assisted beats. RESULT: The slope of the end-systolic pressure-volume relationship decreased by 30.5% +/- 27.8% (p = 0.02) during assisted beats. However, left ventricular pump performance improved by increasing stroke volume and external work by 35.9% +/- 36.0% (p = 0.03) and 9.7% +/- 6.8% (p = 0.03), respectively, resulting in a reduction of the volume intercept. As a result, the end-systolic pressure-volume relationship shifted to the left. The efficiency of energy transfer from the native pressure-volume area to the overall external work improved by 7.6% +/- 8.2% (p = 0.04). Cardiomyoplasty did not affect the time constant of left ventricular isovolumic pressure decline or the maximal rate of pressure decay, which suggested that cardiomyoplasty did not affect left ventricular relaxation. CONCLUSIONS: Dynamic cardiac compression in the form of cardiomyoplasty enhanced left ventricular pump performance without interrupting left ventricular filling. The ratio of energy transfer from the native pressure-volume area to the overall external work suggests a myocardial oxygen-sparing effect of cardiomyoplasty.
Asunto(s)
Cardiomioplastia , Transferencia de Energía/fisiología , Ventrículos Cardíacos/cirugía , Función Ventricular Izquierda/fisiología , Animales , Cateterismo Cardíaco , Modelos Animales de Enfermedad , Estimulación Eléctrica , Insuficiencia Cardíaca/cirugía , Contracción Miocárdica , Consumo de Oxígeno , Ovinos , Ventrículo de Músculo Esquelético , Volumen Sistólico , Resultado del Tratamiento , Función Ventricular , Presión VentricularRESUMEN
Similarities in coronary circulation and heart size of sheep to that of humans are specific advantages of a sheep model of congestive heart failure (CHF). CHF was created in 11 sheep (51 +/- 4 kg) by selective sequential intracoronary injection of 90 microns microspheres under 1.5% isoflurane anesthesia. Hemodynamic characteristics were assessed at baseline, 4 weeks after establishment of CHF (ejection fraction [EF] < 35%, n = 11), and 26 weeks (n = 7) later. Baseline echocardiographic EF was 59 +/- 5% and fell to 26 +/- 5% after 5 +/- 2 embolizations. The left ventricular (LV) pressure-volume relationship showed stable decreases in LV end-systolic elastance (Ees) and preload recruitable stroke work. Intravenous infusion of dobutamine increased Ees from 2.8 +/- 1.7 to 4.3 +/- 2.2 and 4.5 +/- 1.4 mmHg/ml at heart rates of 140 and 160/min, respectively, at baseline. Increases of Ees (from 1.3 +/- 0.5 to 2.3 +/- 0.7 and 1.9 +/- 0.5 mmHg/ml at heart rates of 140 and 160/min, respectively) with dobutamine under CHF conditions did not exceed Ees values at baseline without dobutamine. This response to dobutamine infusion did not change 26 weeks after establishment of CHF. This stable ovine CHF model is proposed for studies on the long-term effects of cardiac assist devices.
Asunto(s)
Insuficiencia Cardíaca/etiología , Insuficiencia Cardíaca/terapia , Corazón Auxiliar , Animales , Modelos Animales de Enfermedad , Estudios de Evaluación como Asunto , Insuficiencia Cardíaca/fisiopatología , Hemodinámica , Humanos , Masculino , Microesferas , Ovinos , Especificidad de la Especie , Factores de Tiempo , Función Ventricular IzquierdaRESUMEN
In 1965, the Human Population Laboratory (California State Department of Health Services) conducted a survey of the non-institutionalized population of Alameda County. Subsequent checking of death records disclosed that 521 survey participants aged fifty-five years or over in 1965 had died by January, 1975. A follow-up in 1977-78 of nursing home experience among these decedents revealed that about two-fifths of those for whom information could be obtained (N = 455) had entered a nursing home at least once in the nine-year follow-up period. Further inquiry located 158 cases whose experience of institutionalization before their death could be reconstructed. Among these cases, only 22 per cent ever returned home or transferred to a residential facility after being institutionalized. Most persons died after the first admission, at the nursing home itself or at an acute care hospital to which they had been transferred shortly before death. Among the cases whose experience of institutionalization could be reconstructed, five out of ten spent less than three months, and six out of ten spent less than six months, as patients in nursing home(s). However, nearly 30 per cent of the 158 cases with reconstructed histories accumulated patient-days exceeding a year.