RESUMEN
To examine the use of mechanical cardiac assist devices in prolonged hemorrhagic shock lasting up to 120 min. We induced hemorrhagic shock in anesthetized calves that were then treated 30 or 120 min later with either conventional fluid and blood resuscitation methods or the implantation of a mechanical assist device in addition to conventional fluid resuscitation. We measured hemodynamic and hematologic variables, inflammatory mediators, end-organ function via biochemical parameters, and survival time. Although cardiac output and blood flow in the left anterior descending artery decreased significantly in all calves at the end of the hemorrhage period, the drop was significantly less severe in calves who received mechanical assistance in addition to fluids. Furthermore, the biochemical profile, indicating liver and kidney function, and survival time were better after hemorrhage in device-treated calves than in conventionally treated calves. Levels of inflammatory mediators, which contribute to cell and organ dysfunction, were increased after hemorrhage, but calves with mechanical devices had less of an increase than did calves treated only with fluids. Our results indicate that the use of a mechanical cardiac assist device in combination with conventional fluid and blood resuscitation methods improves survival and end-organ recovery and decreases the myocardial inflammatory response after prolonged hemorrhagic shock when compared with the sole use of conventional fluid resuscitation techniques.
Asunto(s)
Corazón Auxiliar , Choque Hemorrágico/fisiopatología , Choque Hemorrágico/terapia , Animales , Gasto Cardíaco , Bovinos , Modelos Animales de Enfermedad , Femenino , Fluidoterapia/métodos , Distribución Aleatoria , Resucitación/métodosRESUMEN
End organ effects of nonpulsatile (NP) and pulsatile (P) left ventricular assist device (LVAD) flow were compared in a canine model of doxorubicin-induced heart failure. After heart failure induction, a prototype bimodal LVAD was implanted. Hemodynamics, cardiac dimensions, and myocardial metabolism were monitored with the LVAD off (baseline) and on (in NP and P modes at 70% or 100% power). End organ perfusion was assessed by colored microsphere analysis. Seven dogs were used: two died before pump implantation and were excluded from analysis, and the remaining five survived to study termination. At 70% NP, ascending aortic flow and myocardial oxygen consumption (MVO2) decreased significantly. At 100% NP, LV dimensions decreased, aortic systolic, pulse, and LV pressures decreased but not significantly, and ascending aorta flow reversed. At 100% NP, coronary blood flow, MVO2, and LV free wall subepicardial and subendocardial blood flows decreased significantly. However, as NP support increased, the subepicardial/subendocardial blood flow ratio remained near baseline. At 100% NP, right ventricular perfusion decreased but not significantly, cerebral perfusion decreased significantly, and renal perfusion stayed constant. P mode results were similar, except that ascending aorta flow decreased significantly at 100% P instead of reversing as at 100% NP. These results suggest that end organ perfusion is not differentially affected by LVAD flow mode during chronic heart failure.
Asunto(s)
Contrapulsación , Insuficiencia Cardíaca/inducido químicamente , Corazón Auxiliar , Flujo Pulsátil , Función Ventricular Izquierda/fisiología , Animales , Aorta/fisiología , Aorta Torácica/fisiología , Presión Sanguínea/fisiología , Perros , Doxorrubicina , Insuficiencia Cardíaca/diagnóstico por imagen , Insuficiencia Cardíaca/patología , Hemodinámica , Miocardio/ultraestructura , Perfusión , UltrasonografíaRESUMEN
We evaluated a new trileaflet prosthesis and a control bileaflet prosthesis in the mitral and aortic positions in 27 calves. The prototype trileaflet valve (TV1) functioned satisfactorily in the mitral position (TV1m, n = 7) but later yielded thrombogenic complications in the aortic position (TV1a, n = 4). The valve was redesigned (TV2) and retested in the mitral (TV2m n = 4) and aortic (TV2a, n = 5) positions, along with control valves (Cm, n = 4; Ca, n = 3). At necropsy, the valves were graded on a scale of 0 (no visible thrombi) to 4 (thrombi greater than 5 mm and/or obstructed leaflets). The TV1m, TV2m, and Cm animals, respectively, had implant durations of 215+/-112, 140+/-63, and 159+/-89 days and thrombus grades of 0.71+/-0.76, 0.33+/-0.58, and 1.50+/-0.58. The TV1a, TV2a, and Ca animals had implant durations of 18+/-12, 159+/-61, and 108+/-62 days and thrombus grades of 2.75+/-1.00, 0.50+/-0.58, and 0.67+/-0.58 (p < .005; TV2a vs. TV1a). Three TV1a calves died early of valve related complications. A design irregularity, undetected in the mitral position but revealed in the aortic position, caused a high early mortality in the TV1a animals. Redesigning the prosthesis eliminated valve related mortality and significantly reduced the thrombus grade. Because satisfactory performance in the mitral position does not guarantee safety or efficacy in the aortic position, site specific preclinical testing is crucial for mechanical heart valves.
Asunto(s)
Válvula Aórtica , Prótesis Valvulares Cardíacas/efectos adversos , Trombosis/etiología , Animales , Bovinos , Diseño de Equipo , Prótesis Valvulares Cardíacas/normas , Válvula Mitral , Complicaciones Posoperatorias/mortalidad , Trombosis/mortalidad , Trombosis/patología , Factores de TiempoRESUMEN
BACKGROUND AND AIM OF THE STUDY: The hemodynamic characteristics of a new trileaflet mechanical heart valve (TTV) (TriFlo Inc., Costa Mesa, CA, USA) in the aortic position were evaluated in a bovine model. The TTV was designed to combine the durability of mechanical heart valves with the central flow characteristics of a bioprosthesis. METHODS: Using nine calves, the native aortic valve was replaced with a 21-mm TTV (n = 6) or a St. Jude Medical (SJM) valve (n = 3). Hemodynamic values were assessed with echocardiography at implantation and with catheterization at explantation. All calves underwent a necropsy, followed by gross pathology and light microscopy studies. RESULTS: The mean implant duration was 159 +/- 55 days for the TTV and 102 +/- 67 days for the SJM valve. Immediately before euthanasia, the peak and mean pressure gradients were respectively 35 +/- 14 and 24 +/- 9 mmHg for the TTV, and 100 +/- 72 and 59 +/- 38 mmHg for the SJM valve (p = 0.03). Two of the SJM-valve animals were electively sacrificed after showing symptoms of aortic stenosis. At necropsy, all nine valves were free from thrombi, pannus, occlusive tissue, or mechanical impairment of leaflet motion. The prematurely sacrificed SJM-valve animals had concentric myocardial hypertrophy consistent with severe functional aortic stenosis. CONCLUSION: The significantly higher gradients and left ventricular hypertrophy in the SJM-valve animals were related to a smaller effective orifice area, which precluded adaptation to increasing transvalvular volumes in the growing animal. This problem was not seen with the TTV, which performed hemodynamically as well as the SJM valve. The high transvalvular gradients seen with the SJM valve at study end may suggest that the hemodynamic characteristics of the TTV may be superior, though additional studies are needed to confirm this.
Asunto(s)
Válvula Aórtica/fisiopatología , Prótesis Valvulares Cardíacas , Hemodinámica/fisiología , Animales , Válvula Aórtica/diagnóstico por imagen , Estenosis de la Válvula Aórtica/diagnóstico por imagen , Estenosis de la Válvula Aórtica/etiología , Bovinos , Modelos Animales de Enfermedad , Ecocardiografía , Electrocardiografía , Análisis de Falla de Equipo , Hipertrofia Ventricular Izquierda/diagnóstico por imagen , Hipertrofia Ventricular Izquierda/etiología , Modelos Cardiovasculares , Complicaciones Posoperatorias/diagnóstico por imagen , Complicaciones Posoperatorias/etiología , Diseño de Prótesis , Ajuste de PrótesisRESUMEN
BACKGROUND: The bileaflet valve is currently the mechanical replacement valve of choice. Though durable, it does not closely mimic native valve hemodynamics and remains potentially thrombogenic. METHODS: Prototype trileaflet valves (T1 and T2) were implanted in the mitral position in calves. Group I calves received either a T1 valve (n = 12) or a control bileaflet valve (n = 5); Group II, either a T2 valve (n = 7) or a control bileaflet valve (n = 5). Valve function, perivalvular leakage, and transvalvular pressure gradients were evaluated. Also, long-term prototype leaflet wear was evaluated in vivo in one Group I calf (502 days) and two Group II calves (385 and 366 days). Calves were euthanized and necropsied at study termination, and major organs weighed and examined. RESULTS: Valve function was excellent and hematologic parameters remained normal in all calves that survived to study termination. Mean peak transvalvular pressure gradients were 10 +/- 7 mm Hg for T1 valves, 6 +/- 3 mm Hg for T2 valves, and 12 +/- 4 mm Hg for bileaflet control valves. Clinically insignificant valvular regurgitation was observed in both prototypes. Explanted valves showed no thrombus-impaired leaflet motion, except in two T1-fitted calves and one T2-fitted calf. Major organs showed no evidence of clinically significant thromboembolic events. There were no other significant differences between the results of experimental and control groups. CONCLUSIONS: Prototype trileaflet valves performed safely and effectively in the mitral position in calves, even without long-term anticoagulation. This warrants their evaluation as an equivalent alternative to bileaflet valves.
Asunto(s)
Prótesis Valvulares Cardíacas , Válvula Mitral , Animales , Bovinos , Prótesis Valvulares Cardíacas/efectos adversos , Pruebas Hematológicas , Válvula Mitral/diagnóstico por imagen , Válvula Mitral/patología , Válvula Mitral/cirugía , Complicaciones Posoperatorias/epidemiología , Diseño de Prótesis , UltrasonografíaRESUMEN
Outcomes of mechanical circulatory assistance during hemorrhagic shock were evaluated in a swine model. Pigs were bled to a mean arterial pressure of 35 mm Hg (group I, n = 3) or 40 mm Hg (group II, n = 5; group III, n = 5), maintained there for 30 minutes, and then resuscitated with fluids alone (groups I and II) or fluids plus mechanical circulatory assistance (group III). Mean blood loss was greater in group I than in groups II or III (1,037 +/- 212 vs. 862 +/- 387 ml vs. 681 +/- 117 ml, respectively; I vs. III, p < 0.05) and survival was shorter (230 +/- 25.5 min vs. 709 +/- 251 min vs. 662 +/- 428 min, respectively; I vs. II or III, p < 0.05). Cardiac arrhythmia caused death in most cases. Mean biochemical parameters increased progressively in all cases. Left anterior descending coronary artery flow stayed relatively constant in group II but increased in group III. Superior mesenteric artery flow returned to baseline in group II but increased in group III. Cardiac output was similar in groups II and III, but SGOT levels significantly differed (750 +/- 135 U/L vs. 359 +/- 157 U/L; p < 0.005). These results suggest that the swine model will be useful for studying ways to improve outcomes after prolonged hemorrhagic shock.