RESUMEN
BACKGROUND: The minimally invasive anterior thoracotomy for beating heart coronary bypass offers a modest 10-cm incision and avoids the morbidity of extracorporeal circulation. This study examines minimally invasive direct coronary artery bypass (MIDCAB) wound complications and contributing comorbid factors. METHODS: A retrospective, single-institution review of 165 consecutive MIDCAB cases performed between March 1996 and August 1999 examined all wound abnormalities. Two surgeons performed all cases. RESULTS: Wound complications occurred in 15 patients (9.1%), including three (1.8%) incisional hernias, four (2.4%) superficial dehiscences, three (1.8%) wound infections, three (1.8%) chronic pain syndromes, and two (1.2%) seromas. Two patients with incisional hernias required operative repair. The remaining wound abnormalities responded to conservative therapy. Two chronic pain syndrome cases resolved spontaneously, but the third required advanced pain management. In contrast to MIDCAB, the sternotomy wound complications proved significantly less prevalent (n = 5259, 1.1% vs 9.1%, p < 0.005). CONCLUSIONS: Although MIDCAB offers several advantages over standard approaches, these data suggest that anterior thoracotomy wound complications are not insignificant and may be underestimated by those exploring minimally invasive options.
Asunto(s)
Procedimientos Quirúrgicos Mínimamente Invasivos , Infección de la Herida Quirúrgica , Toracotomía , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Hernia/etiología , Humanos , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Esternón/cirugía , Dehiscencia de la Herida OperatoriaRESUMEN
BACKGROUND: Beating heart or "off-pump" coronary artery bypass (OP-CAB) has become an accepted method of myocardial revascularization by reducing the perioperative morbidity related to cardiopulmonary bypass (CPB). However, the efficacy of OP-CAB has not been well established in the elderly patient population. METHODS: OP-CABs were performed in 53 patients aged 75 years and older, at Pitt County Memorial Hospital from January 1996 to October 1999, either through a median sternotomy or an anterior thoracotomy. These results were compared with 220 patients who underwent standard coronary artery bypass graft (CABG) operation using CPB during the same time period. RESULTS: Mean patient age for both groups was 79+/-0.5 years and preoperative risk factors were similar. There were no differences in postoperative myocardial infarction, atrial fibrillation, bleeding, neurologic complications, or renal failure. There were no deaths after OP-CAB, compared with the 7.6% operative mortality rate after CABG (p<0.05). The OP-CAB group had a significantly shorter postoperative length of stay (4.4+/-0.4 days vs. 8.4+/-0.6 days) and lower transfusion requirements (0.4+/-0.1 units packed red blood cells vs 1.9+/-0.2 units packed red blood cells) than the CABG group. CONCLUSIONS: Our data demonstrate that OP-CAB is a safe and efficacious method of myocardial revascularization in the elderly, and may actually be preferential in these patients when applicable.
Asunto(s)
Puente de Arteria Coronaria/métodos , Anciano , Fibrilación Atrial/etiología , Transfusión Sanguínea , Femenino , Humanos , Tiempo de Internación , Masculino , Complicaciones Posoperatorias , Reoperación , Factores de RiesgoRESUMEN
BACKGROUND: Minimally invasive heart operation differs from traditional cardiac operations through the omission of a sternotomy, cardiopulmonary bypass, or both. Current concerns with minimally invasive operation include: operative safety, learning curve, operative times, arrest times, and adequacy of myocardial protection. While many of the protective strategies used for traditional procedures may be applied to minimally invasive cardiac operations, the safe applications of minimally invasive operations require unique techniques of myocardial protection. METHODS AND RESULTS: Omission of extracorporeal perfusion may benefit patients through attenuation of systemic inflammatory response, decrement in neurologic insults, and reduced bleeding complications. As a counterbalance, surgeons must consider long-term operative quality and level of myocardial protection provided during beating heart coronary operation. Current issues that must be addressed include: pharmacologic management, coronary collateralization and ischemic preconditioning, the utility of intraluminal coronary shunts, and technical adequacy of the anastomosis. Nonsternotomy cardiopulmonary bypass methods utilize alternative incisions and "port-access" technology, and may render more rapid patient recovery including: decreased pain, shortened hospital stay, and more rapid return to work. Altered strategies of myocardial protection in a closed chest environment must address: method of cannulation, technique of aortic occlusion, rapidity and maintenance of cardiac arrest, and cardiac de-airing techniques. CONCLUSIONS: Previous obstacles to minimally invasive cardiac operations included limitations in operative exposure, inadequate perfusion technology, and inability to provide myocardial protection. Recent advances in videoscopic visualization and evolving mechanisms of myocardial protection may justify the expanding application of minimally invasive techniques.
Asunto(s)
Paro Cardíaco Inducido , Procedimientos Quirúrgicos Mínimamente Invasivos , Daño por Reperfusión Miocárdica/prevención & control , Estudios de Factibilidad , Paro Cardíaco Inducido/instrumentación , Humanos , Precondicionamiento Isquémico Miocárdico , Daño por Reperfusión Miocárdica/etiología , Revascularización Miocárdica/instrumentación , Instrumentos QuirúrgicosRESUMEN
BACKGROUND: Controversy exists as to whether off-pump CABG with local occlusion results in clinically significant myocardial ischemia during the occlusion period. This study was undertaken to delineate the effects of transient local coronary artery occlusion on regional systolic function. METHODS AND RESULTS: Eight consenting patients undergoing left internal mammary to left anterior descending coronary artery (LAD) bypass were instrumented with a left ventricular pressure catheter and 2 subepicardial cylindrical ultrasonic dimension transducers placed in the minor axis dimension in the region served by the LAD. A digital sonomicrometer was used to collect data before, during, and after coronary occlusion from which percent systolic shortening and pressure-dimension loops were derived. Measuring devices were removed immediately after the final time point. All patients tolerated the procedure well, and there were no complications. Average duration of local occlusion needed for CABG was 15.9+/-4.4 minutes (range, 12 to 26 minutes). Local occlusion was associated with a decrease in peak systolic shortening from 5.8+/-0.8% to 1.8+/-0.8%. In all cases, function returned to baseline after restoration of flow. Pressure-dimension loops confirmed these findings and no evidence of diastolic creep. Linear repression analysis of degree of stenosis versus change in segmental shortening revealed a significant inverse correlation. CONCLUSIONS: Local occlusion of the LAD resulted in a transient decrease in myocardial function during occlusion with complete recovery during reperfusion. This change was less significant with increasing degrees of coronary stenosis. These data suggest that local occlusion is not associated with permanent myocardial injury but that ischemic changes do occur that may be clinically significant, especially in patients with lesser degrees of coronary stenosis.
Asunto(s)
Puente de Arteria Coronaria , Función Ventricular Izquierda , Adulto , Anciano , Puente de Arteria Coronaria/efectos adversos , Puente de Arteria Coronaria/métodos , Femenino , Humanos , Masculino , Persona de Mediana Edad , SístoleRESUMEN
BACKGROUND: Minimally invasive direct coronary artery bypass grafting involving beating heart left internal mammary artery to left anterior descending coronary artery anastomoses are performed with increasing frequency. Controversy exists regarding the need for intraoperative assessment of graft patency. METHODS: We designed a technique to perform arteriography of the left internal mammary artery by using left radial artery access and standard fluoroscopy to evaluate patency in the operating room. The last 50 of 87 minimally invasive direct coronary artery bypass grafting operations were evaluated by intraoperative arteriography and Doppler ultrasound. Angiograms were performed by the surgeon and involved cannulation and direct injection of contrast medium into the origin of the left internal mammary artery via the left radial artery. RESULTS: Total procedure time was less than 15 minutes. No injuries to the left internal mammary artery were identified. Anastomotic occlusions were identified in 4 cases (8%), 2 of which involved sequential diagonal and left anterior descending anastomoses. These were corrected at the time of surgery with 2 cases requiring conversion to standard coronary artery bypass grafting. Qualitative assessment of grafts with Doppler ultrasound failed to definitively identify these occlusions. There were no deaths and no perioperative infarctions. CONCLUSION: Intraoperative arteriography of the left internal mammary artery can be performed by the surgeon, and a significant number of anastomotic problems may be identified and corrected by using this technique. Therefore, a 100% early graft patency rate may be attainable.
Asunto(s)
Angiografía Coronaria , Vasos Coronarios/diagnóstico por imagen , Anastomosis Interna Mamario-Coronaria/métodos , Cuidados Intraoperatorios , Radiografía Intervencional , Ultrasonografía Doppler , Ultrasonografía Intervencional , Grado de Desobstrucción Vascular , Adulto , Anciano , Anciano de 80 o más Años , Cateterismo Periférico , Medios de Contraste/administración & dosificación , Puente de Arteria Coronaria , Estudios de Evaluación como Asunto , Femenino , Fluoroscopía , Oclusión de Injerto Vascular/diagnóstico por imagen , Humanos , Anastomosis Interna Mamario-Coronaria/efectos adversos , Complicaciones Intraoperatorias/prevención & control , Masculino , Persona de Mediana Edad , Procedimientos Quirúrgicos Mínimamente Invasivos , Infarto del Miocardio/prevención & control , Arteria Radial , Tasa de Supervivencia , Factores de TiempoRESUMEN
OBJECTIVE: This study was done to determine the potential benefits of minimally invasive mitral surgery performed with intraoperative video assistance. METHODS: From May 1996 until March 1997, a minithoracotomy and video assistance were used in 31 consecutive patients undergoing mitral repair (n = 20) and replacement (n = 11). Their ages ranged from 18 to 77 years (59 +/- 2.6 years; mean +/- standard error of the mean). Ejection fractions were 35% to 62% (55% +/- 1.5%). Operations were done with either antegrade/retrograde (n = 10) or antegrade (n = 19) cold blood cardioplegia and a new transthoracic crossclamp or with ventricular fibrillation (n = 2). Peripheral arterial cannulation (n = 28) and pump-assisted right atrial drainage (n = 26) were used most often. RESULTS: No hospital deaths occurred, but the 30-day mortality was 3.2%. Complications included deep venous thrombosis and a phrenic nerve palsy in one patient each. No patient had a stroke or required reoperation for bleeding. Postoperative echocardiography showed excellent valve function in all but one patient. Cardiopulmonary bypass and arrest times averaged 183 +/- 7.2 and 136 +/- 5.5 minutes, respectively. Compared with 100 patients having conventional mitral valve operations, these patients had significantly shorter hospitalization times (8.6 +/- 0.5 vs 5.1 +/- 0.9 days, p = 0.05). Moreover, 81% of the later cohort were discharged between day 3 and 5 (3.6 +/- 0.2 days). Hospital charges (decreases 27%, p = 0.05) and costs (decreases 34%, p < 0.05) were less than in conventional operations. Patient follow-up suggested minimal perioperative pain and rapid recovery. CONCLUSIONS: Early results suggest that video-assisted minimally invasive mitral operations can be done safely. These methods may benefit patients through less morbidity, earlier discharge, and lower cost.
Asunto(s)
Implantación de Prótesis de Válvulas Cardíacas/métodos , Válvula Mitral/cirugía , Puente Cardiopulmonar , Estudios de Cohortes , Femenino , Enfermedades de las Válvulas Cardíacas/cirugía , Implantación de Prótesis de Válvulas Cardíacas/economía , Precios de Hospital , Costos de Hospital , Humanos , Tiempo de Internación , Masculino , Persona de Mediana Edad , Procedimientos Quirúrgicos Mínimamente Invasivos/economía , Procedimientos Quirúrgicos Mínimamente Invasivos/métodos , Estudios Retrospectivos , Esternón/cirugía , Toracotomía/métodos , Grabación en VideoRESUMEN
Cardiac surgery remained largely unchanged while other surgical specialties moved rapidly toward less invasive operations during the past 10 years. In the past year, however, heart surgery has begun to turn in a minimally invasive direction. The present feverish pace is fueled by the media and patient preference as well as commercial developments that have made minimally invasive heart surgery possible. At present, select coronary artery bypass procedures can be performed without the use of cardiopulmonary bypass or median sternotomy. Both mitral and aortic valve replacements can now be done through limited incisions that avoid sternal splitting. These minimally invasive operations probably represent the infancy of a new era of cardiac surgery. In the 21st century many coronary bypass operations will be performed as ambulatory procedures with same day or next day discharge. Patients will return to full activity within a week. Cardiac valve procedures will remain inpatient procedures with hospital stays of approximately three days and return to normal activity will occur at two weeks. We will attain these goals given the current state of the art. Imagine what vast improvements the future holds.
Asunto(s)
Procedimientos Quirúrgicos Cardíacos/métodos , Procedimientos Quirúrgicos Cardíacos/tendencias , Procedimientos Quirúrgicos Mínimamente Invasivos , Puente de Arteria Coronaria/métodos , Enfermedades de las Válvulas Cardíacas/cirugía , Humanos , Procedimientos Quirúrgicos Mínimamente Invasivos/tendenciasRESUMEN
This report describes a minimally invasive mitral valve repair done through a limited (6-cm) thoracic incision. The patient was supported by peripheral extracorporeal perfusion with cardiac arrest established using a new transthoracic aortic cross-clamp and antegrade blood cardioplegia. The patient was discharged on postoperative day 3 with minimal pain. This less invasive approach to mitral valve surgery may offer combined advantages to patients by increasing comfort, expediting recovery, and decreasing surgical costs by using modified traditional methods compared with specialized intraaortic occlusive balloons.
Asunto(s)
Insuficiencia de la Válvula Mitral/cirugía , Válvula Mitral/cirugía , Procedimientos Quirúrgicos Cardíacos/métodos , Constricción , Femenino , Paro Cardíaco Inducido , Humanos , Persona de Mediana Edad , Procedimientos Quirúrgicos Mínimamente InvasivosRESUMEN
Minimally invasive coronary artery bypass grafting involving anastomosis of the left internal mammary artery to the left anterior descending coronary artery has become popular in the last year. Critics of this technique infer lower graft patency rates and increased cardiac morbidity. Therefore a technique is described that allows intraoperative selective left internal mammary arteriography to be performed by the surgeon to ensure graft patency before leaving the operating room.
Asunto(s)
Cateterismo/métodos , Puente de Arteria Coronaria/métodos , Arterias Mamarias , Humanos , Cuidados Intraoperatorios , Procedimientos Quirúrgicos Mínimamente Invasivos , Arteria Radial , Grado de Desobstrucción VascularRESUMEN
A new practical descriptor of metabolic to mechanical myocardial energy transfer (MET), termed the virtual work model, was evaluated in 32 conscious dogs and in 8 isolated canine hearts. An index of total mechanical energy expenditure (TME) was calculated as the sum of external energy (stroke work) and an internal energy index of heat (left ventricular end-diastolic volume times left ventricular mean ejection pressure). Physiological comparison of TME (x-axis) and myocardial oxygen consumption (MVO2; y-axis) yielded highly linear MET relationships (mean r = 0.93 +/- 0.07), with an average slope of 0.86 +/- 0.39 (SD) and a y-intercept of 9.1 +/- 6.4 mW/ml myocardium. The linear MVO2-TME relationship did not vary under steady-state vs. dynamic vena caval occlusion, increased heart rate, increased afterload, or increased inotropic state with calcium infusion. Compared with five other indexes of myocardial energetics, the virtual work model of MET was the most linear, the most practical in not requiring determination of the end-systolic pressure-volume relationship, and the most accurate predictor of MVO2 under normal and altered hemodynamic conditions.
Asunto(s)
Miocardio/metabolismo , Consumo de Oxígeno , Animales , Fenómenos Biomecánicos , Constricción Patológica , Perros , Metabolismo Energético , Frecuencia Cardíaca , Hemodinámica , Homeostasis , Técnicas In Vitro , Modelos Cardiovasculares , Contracción Miocárdica , Venas Cavas/fisiopatologíaRESUMEN
The physiological effects of intravenous ouabain on left ventricular (LV) systolic function and metabolic-to-mechanical energy transfer were examined in eight conscious dogs. LV pressure and volume were measured using micromanometers and ultrasonic dimension transducers during transient vena caval occlusions under control conditions and after increasing doses of ouabain. Doppler coronary flow and coronary sinus O2 saturations were used to determine arterial-to-coronary sinus O2 content difference and thereby to calculate LV O2 consumption; total mechanical energy was computed as the sum of LV stroke work and the product of end-diastolic volume and LV mean ejection pressure, neglecting LV unstressed cavitary volume. The slope (10(4) erg/ml) of the stroke work vs. end-diastolic volume relationship increased progressively with rising doses of ouabain from 7.0 +/- 1.6 at control to 9.6 +/- 1.7 after ouabain 0.75 mg (P = 0.0002). Regression analysis of LV O2 consumption (mW/cm3) vs. total mechanical energy (mW/cm3) yielded a linear relationship that did not change with 0.75 mg of ouabain (P > 0.4). These data indicate that ouabain possesses a significant positive inotropic effect on the intact left ventricle without a change in energy transfer efficiency or O2 wasting.
Asunto(s)
Corazón/fisiología , Miocardio/metabolismo , Ouabaína/farmacología , Consumo de Oxígeno/efectos de los fármacos , Animales , Estado de Conciencia , Diástole/efectos de los fármacos , Perros , Relación Dosis-Respuesta a Droga , Metabolismo Energético/efectos de los fármacos , Corazón/efectos de los fármacos , Oxígeno/sangre , Análisis de Regresión , Volumen Sistólico/efectos de los fármacos , Función Ventricular Izquierda/efectos de los fármacos , Función Ventricular Izquierda/fisiologíaRESUMEN
BACKGROUND: Procedure-related costs are of increasing concern in selecting the appropriate procedure for the treatment of coronary artery disease (CAD). METHODS AND RESULTS: To determine what preoperative factors influence total postoperative hospital costs, data on 604 coronary artery bypass graft surgery (CABG) patients from 1990 to 1991 were analyzed. Professional fees were excluded. Hospital costs were computed by multiplying patient charges by the Medicare cost-to-charge ratio used in determining federal reimbursement. Median postoperative cost was $12,912 (range $7100 to $259,546). Data were analyzed with a semiparametric regression model. Patients dying in the hospital were censored at time of death. There were significant differences among surgeons in costs but no significant differences in operative mortality. Significant risk factors for increased cost after adjusting for surgeon were: older age (P < .0001), lower left ventricular ejection fraction (P < .0001), prior CABG (P < .0001), female sex (P < .0049), no prior percutaneous transluminal coronary angioplasty (P < .0091), increased degree of CAD (P < .0102), black race (P < .0190), and diabetes (P < .032). CONCLUSIONS: These results suggest that preoperative characteristics have important economic and medical implications. Surgeons should compare their management strategies on the basis of data analysis to determine the most effective practice with regard to mortality and cost.
Asunto(s)
Puente de Arteria Coronaria/economía , Enfermedad Coronaria/cirugía , Costos de Hospital/estadística & datos numéricos , Hospitales Universitarios/economía , Cuidados Posoperatorios/economía , Adulto , Factores de Edad , Anciano , Enfermedad Coronaria/epidemiología , Análisis Costo-Beneficio , Diabetes Mellitus/epidemiología , Femenino , Mortalidad Hospitalaria , Humanos , Modelos Logísticos , Masculino , Persona de Mediana Edad , North Carolina , Factores de Riesgo , Factores Sexuales , Volumen SistólicoRESUMEN
The physiological mechanism of paradoxical pulse in cardiac tamponade remains controversial. In eight conscious dogs with intact pericardia, ultrasonic dimension transducers assessed biventricular geometry and volumes, while micromanometers measured right ventricular (RV), left ventricular (LV), pleural, and pericardial pressures. With normal inspiration, peak LV pressure fell by 7.7 +/- 1.3 mmHg at control and by 20.3 +/- 3.7 mmHg during tamponade (P < 0.001), consistent with the development of paradoxical pulse. At peak inspiration during tamponade, RV filling increased, the interventricular septum shifted leftward, transeptal pressure became negative, and LV septal arc length (l theta) became smaller than its respective unpreloaded value at maximal vena caval occlusion (l(o)). Analysis of stroke work (SW)-end-diastolic volume (EDV) and end-systolic pressure-volume coordinates at peak inspiration during tamponade revealed that end-systolic pressure was 19.1 +/- 10.2 mmHg below the baseline end-systolic pressure-volume curve (P < 0.01), and SW was 24.2 +/- 8.8% below the baseline SW-EDV curve (P < 0.01), indicating transient inspiratory LV dysfunction. It is proposed that inspiratory leftward interventricular septal shifting at low LV EDV during tamponade completely unloads the septum (l theta < l o), eliminates the septal contribution to global LV SW, results in transient inspiratory LV dysfunction, and contributes to the phenomenon of paradoxical pulse.
Asunto(s)
Presión Sanguínea , Taponamiento Cardíaco/fisiopatología , Respiración , Animales , Volumen Sanguíneo , Perros , Hemodinámica , Modelos Cardiovasculares , Pericardio/fisiopatología , Pleura/fisiopatología , Presión , Valores de Referencia , Volumen Sistólico , Sístole , Función Ventricular Izquierda , Función Ventricular DerechaRESUMEN
Although improved surgery, angioplasty, and thrombolysis have made early revascularization of ischemic myocardium commonplace, the effects of arterial hypertension on myocardial recovery remain unclear. Therefore eight conscious dogs were instrumented to measure left ventricular transmural pressure and myocardial segment length in the left anterior descending (LAD) coronary distribution. Reversible ischemic injury was produced by two 15-min LAD occlusions separated by 4 days of reperfusion, with each dog randomly receiving either phenylephrine or placebo infusion for 30 min beginning 1 h after reperfusion. With ischemia, systolic myocardial performance fell to 14.3 +/- 3.7% of control and required greater than 48 h to recover. Compared with placebo, phenylephrine significantly depressed recovery of systolic function assessed by systolic shortening (57 +/- 12 vs. 85 +/- 13% control) or the area under the stroke work vs. end-diastolic length relationship (62 +/- 14 vs. 93 +/- 7% control) (both P less than 0.05). These data imply that ischemically injured myocardium is highly sensitive to arterial hypertension and that ventricular loading is a major determinant of the rate of myocardial recovery.
Asunto(s)
Enfermedad Coronaria/complicaciones , Corazón/fisiopatología , Hipertensión/complicaciones , Reperfusión Miocárdica , Animales , Presión Sanguínea , Circulación Coronaria , Enfermedad Coronaria/fisiopatología , Perros , Hipertensión/inducido químicamente , Hipertensión/fisiopatología , Fenilefrina , Volumen Sistólico , SístoleRESUMEN
The need for a better organ preservative solution in heart transplantation is clear. At the same time, newer techniques in the assessment of cardiac function in the laboratory have made accurate load-independent quantification of myocardial preservation possible. Therefore a study was undertaken to evaluate left ventricular function in transplanted hearts after 14 hours of preservation in the intracellular lactobionate solution. Nine dogs were instrumented with ultrasonic dimension transducers, to measure left ventricular epicardial volume, and with micromanometers, to measure left ventricular pressure. Left ventricular wall volumes were determined from epicardial echocardiograms. To define the extent of organ injury resulting from the transplant procedure and cardiopulmonary bypass alone, four other animals were instrumented in a similar fashion, and left ventricular function was assessed after standard cardioplegic arrest and transplantation. The transplant procedures were performed with a warm ischemic period of 0.75 +/- 0.2 hours. In all experiments, data were collected before graft harvest and 1 hour after separation from cardiopulmonary bypass. Standard cardioplegic arrest and 2.4 +/- 0.1 hours of ischemia resulted in a decrease in left ventricular ejection fraction from 0.43 +/- 0.04 to 0.27 +/- 0.1 (37%) (p less than 0.01), a decrease in the slope of the stroke work/end-diastolic volume relationship from 15.4 +/- 7.9 to 7.9 +/- 2.0 erg X 10(4) (49%; p less than 0.01), and a decrease in the myocardial power output from 19.7 +/- 10.9 to 5.9 +/- 1.9 (70%; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Soluciones Cardiopléjicas , Trasplante de Corazón/fisiología , Soluciones Preservantes de Órganos , Preservación de Órganos/métodos , Soluciones , Adenosina , Alopurinol , Animales , Perros , Ecocardiografía , Glutatión , Insulina , Contracción Miocárdica/fisiología , Rafinosa , Factores de Tiempo , Función Ventricular Izquierda/fisiologíaRESUMEN
Pulse-transit sonomicrometry was used to measure the base-apex (a), anteroposterior (b), and septal-free wall (c) diameters of the left ventricle and the septal-free wall diameter of the right ventricle (d) in eight excised and three isolated, pump-perfused canine heart preparations, as well as in nine conscious dogs. In the three perfused hearts and in four of the excised hearts, right ventricular free wall regional segment lengths and segment area also were assessed. Biventricular volumes were measured directly with intracavitary balloons in all isolated hearts. When left ventricular balloon volume was held constant, relations between right ventricular free wall dimensions and right ventricular balloon volume were highly linear. With increments in left ventricular volume, however, these relations remained linear but shifted progressively upward, indicating an independent relation between right ventricular free wall dimensions and left ventricular cavitary volume. An ellipsoidal shell subtraction model (pi/6.abd minus right ventricular free wall volume) was developed to estimate right ventricular cavitary volume from cardiac dimensions. With this method, a highly linear relation was observed between calculated right ventricular volume and right ventricular balloon volume (mean r = 0.99 +/- 0.01). Moreover, this relation appeared to be independent of changes in left ventricular balloon volume. With the shell subtraction model, dynamic right ventricular volume was computed in nine conscious dogs, and in four, stroke volume derived from dimensions was compared with right ventricular stroke volume measured with ultrasonic flow probes. A highly linear relation was observed, suggesting the accuracy of the shell subtraction method in vivo. Right ventricular end-systolic pressure-volume and stroke work/end-diastolic volume relations then were evaluated, and both proved to be highly linear in the right ventricle (both mean r = 0.99 +/- 0.01). Thus, the shell subtraction model allows a simple estimate of dynamic right ventricular volume in the intact heart and facilitates assessment of right ventricular performance in vivo.
Asunto(s)
Volumen Cardíaco , Función Ventricular , Animales , Perros , Técnicas In Vitro , Modelos Biológicos , Volumen SistólicoRESUMEN
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.